AD-A270 508 

I 1111111 ~111~11111111111!1!1 ~Ill II!! ~I! 1/ 

DOT/FAA/AM-93/15 

Office of Aviation Medicine 

Washington, D.C. 20591 

Human Factors in Aviation 

Maintenance - Phase Three, 

Volume 1 Progress Report 

Galaxy Scientific Corporation 

Pleasantville, NJ 08323 

Office of Aviation Medicine 

Federal Aviation Administration 

Washington, DC 20591 

August 1993 OTIC ' ELEC~!n OCT121--u 

Final Report B . 

This document is available to the public 

tbrough the National Technical Information 

Service, Springfidd, V trginia 22161. 

u.s. Oeparlmenl 

of Transporlalion 

Federal Aviation 

Admlnlstrlllon 
NOTICE 

This document is disseminated under the sponsorship of 

the U.S. Department of Transponation in the interest of 

information exchange. The United States Government 

assumes no liability for the contents or use thereof. 
Technical Report Documentation Page 

1 . Report No. 2. Government Accession No. 3. Recipient's Catalog No. 

DOT/FAA/AM-93/15 

4. Tide and Subtitle 5. Report Date 

Human Factors in Aviation Maintenance- Phase Three, Volume I August 1993 

Progress Repon 

6. Performing Organization Code 

7. Author(s) 8. P~:forming Organization Report No. 

Galaxy Scientific Corporation 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS} 

Galaxy Scientific Corporation 

2500 English Creek Avenue, Suite 1100 

Pleasanrville, NJ 08323 11. Contract or Grant No. 

DTF AO 1-92-Y -0 I 005 

12. Sponsoring Agency r •.. 1e and Address 13. Type of Report and Period Ccr.-ered 

Office of Aviation Medicine Interim Federal Aviation Administration 

800 Independence Avenue, S.W. Feb!Uai}' 1992- December 1992 

Washington, DC 20591 

14. Sponsoring Agency Code 

15. Sui)Diemental Notes 

16. Abstract 

The third phase of research on Human Factors in Av:ation Maintenance continued to look at the human's 

role in the aviation maintenance system via investigations, demonstrations, and evaluations of the research 

program outputs. This report describes an evaluation of a computer-based training simulation for 

troubleshooting an airliner environmental control system and an evaluation of the aircraft maintenance 

visual environment. A job aid for Aviation Safety Inspectors is also reponed on, along with an evaluation 

of pen computers considered for the job aid. This ptogress report also describes research on ergonomic 

factors related to posture and fatigue; identification of characteristics of personnel best suited for 

inspection-oriented jobs; redesigr of work control cards; and visual inspection and training alternatives in 

aviation maintenance. 

17. KsyWonls 18. Distributir.n Statement 

human factors, maintenance, computer-bated instruc- Document is available to the public through the 

tion, simulation visual environment, job aid, pos- National Technical Information Service, 

rure, fatigue, workcards, training, NDI performance Springfield, Virginia 22161. 

19. Security Classif. (of this report) 2::1. ~-:.--curity Cfass;f. (of this page) 21. No.ofPag~ 22. Price 

Unclassified Unclassified 167 

Form DOT F 1700.7 (8-72) Reproduction of completed page authurized 
Acknowledgments 

TheA viationMaintenance Human Factors research team is directed by Dr. William T. Shepherd 

and Ms. Jean Watson of the Oifice of Aviation MedicinE~ 

Galaxy Scientific Corporation is the prime contractor. Galaxy Scientific is technically 

responsible for Chapters One through Three. Dr. Ric..'lard Thackrayprepared Chapter Four. 

Chapters Five through Eight were prepared by the Department of Industrial Engineering at 

the State University of New York at Buffalo. The total report was edited by Ms. Suzanne 

Morgan of Galaxy Scientific Corporation. 

The pragmatic nature of this research is attributable to many FAA, airline, manufacturer, and 

vendor personnel who provided advice to the research team. 

ITIS QR.U:I 

DfiC TAB 0 

Uuazmounced 0 · Just 1! .. ,.,,u<>ZL..----1 

Ill •• "":.:.t.'~· 

.. • 
··~·· . 

Table of Counts 

Table of Contents 

CHAPTER ONE - Pm!se ID 

L 1 SUMMARY . . . . . . . • . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

1.2 AN AIRLINE EVALUATION OF ADVANCED TECHNOLOGY TRAINING (Chapter 

Two) • . • • • • • • . • • . • • . • • • • • • • . . • . . . . . . • . • . • . • . . . • . . • . . . . . . . . . . • . . . . . 1 

1.3 IMPROVING PERFORMANCE WI1H BETTER INFORMATION CONTROL (Chapter 

Tilree) . . . • • . • • • • • • • . . • • • . • • • • . . • • . . . • • . . . . • • . • . . • . . . . . . . . • . . . . . . • . 2 

1.4 PERFORMANCE IN INSPECTION TASKS (Chapter Four) . . . . . . . . . . . . . . . . . . . . . . 2 

L5 ERGONOMIC FACTORS AFFECI1NG POSTURE AND FATIGUE (Chapter Five) . . . . 2 

1.6 AN EVALUATION OF'IHEAIRCRAFr MAINTENANCE VISUAL ENVIRONMENT 

(Chapter Six) . . . . • . . • . . . . . . . . . . . . . . . • . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . 2 

1.7 A REDESIGN OF MAIN'IENANCE WORK CONTROL CARDS (Chapter Seven) . . . . . 3 

1.8 TRA.NING FOR VISUAL INSPECTION (Chapter Eight) . . . . . . . . . . . . . . . . . . . . . . . 3 

1.9 CONTINUING RESEARCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

CHAPTER TWO - Results of the Environmental Control System Tutor Experiment 

2.0 INTRODUCTION • • . • . . . . . . . • • . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

2.1 PURPOSES OF 'IHE EXPERIMENT . • • . . . • . . . • • . . • • . . . . . . . . . . . . . . • . . . . . . . 5 

2.2 ENVIRONMENTAL CONTROL SYSTEM OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . 5 

2.21 1be Flightline Technician . . . . . . • • . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

2.2.2 Overview of ECS Tutor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

2.3 METHOD • . • • • . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

2.3.1 Subjects . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . 7 

2.3.2 Procedure . . • . . . . . . • . . . . . • . • • . . . . • . . . . . . . . . . . . . . . • . . • • . . . . . . . . 7 

2.3.3 Data . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

2.4 RESULTS • . . . . • . • . . . . . . . . . . . • . . . . • . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

2.4.1 Examjnation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

2.4.2 Examim!lion Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

2.4.3 Written Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

2.4.4 Caveats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

2.5 CONCLUSION . . . . . . • • . . . . . . • . . . . . • . • • . . • . . . . . . . . • . . . . . . . . . . . . . . . . 13 

2. 6 REFERENCES • • • . . • • • • . . • • . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

Appendix A . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

CHAPTER THREE - Pea Computers: Evaluations, Recommendations, and Ole PENS Project 

3.0 INTRODUCTION . . .. • .. • .. • .. .. .. • .. • . .. • .. . .. .. . . . . .. . . .. . . . .. .. . 25 

3.1 GENERAL CHARACTERISTICS OF PEN COMPUTERS . . . . . . . • . . . . . . . . . . . . . . 25 

3.2 KEY BENEFIT OF PEN COMPUTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

3.3 PO'IENTIAL USES OF PEN COMPUTERS .. .. . .. . . .. . .. .. .. . .. . . . . . .. . .. . 26 

v 
Ttible of Contents 

3.4 

3.5 

. 3.6 

3.7 

COMPARISON OF PEN COMPUTERS . . . . . . . . . . . . . . . • . . . . . . . . . • . . . . . . . . . 27 

3.4.1 Evaluated Characteristics . . . . . . . . . . . . . . . • . . . . . . . . . • . . . . . . . . . . . . . . 27 

3.4.2 Common Features of Pen Computers . . • . . . • . . . . . . . . . . . . . . . . . . . . . . . . . 31 

3.4.3 Common Limitations of Cuirent Pen Computers . . . . . • . . . . . . . . . . . . . . . . . . 33 

3.4.4 Tradeoffs Between Pen Computers . . . . . . . . • . . . . . • • . • . . • . . . . . . . . . . . . 33 

PENS: A EERFORMANCE ENHANCEMENT ~YSTEM . • . . • . . • . . . • . . . . . . . . . . 34 

3.5.1 Improved Fonns . . . . . . . • . . . . • . . . . . . . . . . . . . • . • . . . • • . • . . . . . . . . . . 34 

3.5.2 On-line Documentation . . . . . . . . . . . . . . . . . . . . . . • • . . • . . . • . . . . . . . . . . 35 

3.5.3 Additional Benefits . . . . . • . . . • . . . . . • . . . . . . . . . . . • . . . . . • . . . . . . . . . . 35 

EVALUATION AND IMPLEMENTATION . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . 36 

3.6.1 Evaluation Plan . . . • . . . . . . . . . . . . . . . . . . • . • . • • . . . . . • . . • . . • . . . . . . . 36 

3.6.2 FAA Regions . . . . . . • . . . . . • . . . . . . . . . . . . . . . . . • . • . . . . • . • . . . . . . . . 37 

3.6.3 Pen Computer Models . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 

3.6.4 Experimental Design . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . • 37 

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 

3.8 

Appendix A 

Appendix B 

Appendix C 

Appendix D 

REFERENCES . . . • . . . . . . . . . . • . • . • . . . . . . . . . . . . . . . . . . . • . . . . . . . • 38 

•••••••• 0 • 0 •• 0 •••••••••••••• 0 ••• 0 ••• 0 •••••••••• 0 ••• 0 •••••••• 

39 

47 

50 

52 

CHAPTER FOUR - Correlates of Individual Differences In Nondestructive IDSpedlon Performance 

4.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . • . . • . . . . . • • . . . . • . . 55 

4.1 BACKGROUND AND SURVEY OF RELEVANT NDI RESEARCH . . . . . . . . . . . . . . 55 

4.l.l Nondestructive Testing and Damage-tolerance Design . . . . . • • . . . . . . . . . • . . . 55 

4.1.2 Air Force Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 

4.1.3 Nuclear Power Industry Research . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . 61 

4.1.4 Federal Aviation Administration (FAA) Research . . . . . . . . . . . . . . . • . . • . . . . 63 

4.2 GENERAL SURVEY OF INSPECTION AND VIGILANCE RESEARCH . . . . . . . . . . . 65 

4.2.1 Inspection . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . 65 

4.2.2 Vigilance . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 

4.3 RESEARCH NEEDS . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . 68 

4.4 PROPOSED RESEARCH . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . 69 

45 REFERENCES . . . . . . . . . . . . . . . . . . . . . . • . . . . • . . . . • . . . . . . . . . . . . . . . . . . . . 70 

CHAPTER FIVE - Investigation of Ergonomic Factors Related to Posture and Fatigue 

5.0 INTRODUCTION . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . • . . . . . . . . . . . 73 

5.1 RESTRICTIVE SPACE MODEL • . . • • . • . . . . . . . . . . . . . • . . . . . . . . . • • . . . • . . . . 73 

5.2 RESTRICTIVE SPACE FACI'ORS . . • • . • . . • • . . . • . . . . • • . . • . . . • . • • . . . . . . . . 15 

5.2.1 The Task . . . . . . . • . . . • . • . . . . . . . . . . . . . . . . • . . . • . . . • . . . . • • . . . . . . 75 

5.22 The Environment . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . • . . . . . . . . . . 78 

5.2.3 The Operaror . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 

5.3 PHYSICAL AND PERCEIVED SPACES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . 79 

5.4 STRESS . . . . . . . . . . . . . . • . . . . . . . . . . . . • . . . . . . . . . . . . • . . . . . . . . . . . . . . • . 79 

vi 
~:-: .·-- ·

 :-.:"";··- ·:-:~ 

.. >· 

Table of CorJents 

5.5 FATIGUE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 

5.6 OPERATOR RESPONSE . . . . . . . • . . . . . • . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . 81 

5.7 EFFECTS ON OPERATOR • . . . . . . . . . . . . . . . . • . . . . . • . . . . . • • . . . . . . . . . . • . 81 

5.8 . A RESTRICTIVE SPACE FRAMEWORK TO MEASURE THE EFFECTS ON 

PERFORMANCEIWORKLOAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 

5.8.1 Zone 0- Anthropometrically Restricted Zone . . . . . . . . . . . . . . . . . . . . . . . . . 82 

5.8.2 Zone 1 -Performance Restricted Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 

5.8.3 Zone 2- Workload/Stress Restricted Zone . • . . • • . . . . . . . . . . . . . . . . . . . . . . 82 

5.8.4 Zone 3 - Unrestricted Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 

5.9 RESTRICTIVE SPACE METIIODOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 

5.10 ON-SITE EVALUATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 

5.10.1 Task Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 

5.1 0.2 Behavioral Measures . . . . . . . . . . . . . . . . . . . • . . . . . . . • . . . . . . . . . . . . . . . 83 

5.10.3 Psychophysical Measures . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . 84 

5.10.4 Experimental Protocol . . . . . • . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 

5.11 LABORATORY EVALUATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 

5.11.1 Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 

5.11.2 Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 

5.11.3 Independent Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 

5.11.4 Dependent Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 

5.11.5 Experimental Procedure . . . • • • . . . • • . . • • • • . . • . • . • . . . . . . . • • . . • . . . . . 87 

5.12 ANALYSIS OF RESULTS . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 

5.13 DEVELOPMENT OF CHECKLIST/INTERVENTION GUIDE . . . . . . . . . . . . . . . . . . . 88 

5.14 REfERENCES . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 

CHAPTER SIX - Evaluation the Visual Environment in Iaspection: A Methodology and a Case 

Study 

6.0 

6.1 

6.2 

6.3 

6.4 

INI'RODUCl"'ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

LIGHT CHARACTERISTICS/LIGHfiNG SYSTEM DESIGN .................. . 

6.1.1 Ught Level ................................................ . 

6.1.2 Color Rendering . . . . . . . . . . . . . . . • • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6.1.3 Glare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6.1.4 Reflectance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . 

6.15 Specialized Ughting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 

6.1.6 Design Requirements For Ughting . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . 

THE EXISTING VISUAL ENVIRONMENT IN AIRCRAFT INSPECTION ........ . 

6.2.1 Classification Of Ught Sources . . . • • • . • • . . . • . • • • . . • . . . • • • . • . . • • . . • . 

6.2.2 Site Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

EVALUATION OF A VISUAL ENVIRONMENT ........................... . 

6.3.1 Evaluation Of Ambient lliumination, Luminance, and Reflectance .......... . 

6.3.2 Evaluation Of Task Illumination, Luminance, and Reflectance ............. . 

6.3.3 Inspector Perceptions ..................•........................ 

EVALUATION OF ALTERNATIVE LIGHfiNG SOURCES ................... . 

6.4.! Laboratory Evaluation . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6.4.2 Field Evaluation ..............•........•.•.................... 

vii 

93 

93 

93 

94 

95 

95 

96 

96 

97 

97 

97 

97 

98 

99 

100 

104 

104 

104 
Table of Contents 

6.5 RECOMMENDATIONS . . . . . . . . . . . • . . . • . . . . . . . . . . . • . . . . . . • . . . . • . . • . . . 106 

6.6 GUIDE FOR VISUAL ENVIRONMENT EVALUATION ...................••. 109 

6.7 CONCLUSIONS . • • . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . • . . . • . . . 111 

6.8 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . • . . . • . . . . . . . . . . . . 111 

CHAPTER SEVEN - Design of Workcards 

7.0 iNTRODUCTION . . . . . . . • . . . . . . . • . . . . . . . . • . . • . . . . . . . . . . . . . . . . . . . . . . 113 

7.1 A TAXONOMY OF ISSUES IN DOCUMENTATION DESIGN •....•........... 113 

7.2 INFORMATION READABILITY .............•.......... · ............... 113 

7.2.1 Typographic Layout • . . . . . . • • • . . . • • . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 

7.2.2 The Senlence, the Wor<l an<1 the Letter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 

7.3 INFORMATION CONTENT •.....••...............•................... 114 

7.3.1 Approprlale Information Conrent ................................... 114 

7.3.2 Graphic Information . . . . . . . . . . . . . . . . . . . . . . • • . . . . . . . . . . . . . . . . . . . 115 

7.4 INFORMATION ORGANIZATION ...................................... 115 

7 .4.1 Classification of Information . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 

7.4.2 Information Layering . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • . . 116 

7 .4.3 Other Organizational Issues . . • . • . . • • . . • . • . • . • . • • . . • • . . • . . . • • . . • . . 116 

7.5 PHYSICAL HANDLING/ENVIRONMENTAL FACTORS ...................... 116 

7.6 SUMMARY AND GUIDELINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 

7.7 CASE STUDIES IN WORKCARD DESIGN ............................... 119 

7.8. A-CHECK CASE STUDY . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 

7.8.1 Task Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 

7.8.2 Metho<ls . . • . . . • . . • . • . • • • • • • • . . . . • • . . . . . . . • . . • . . . • • . • • . . . . . . • 121 

7.8.3 Results ..................................................... 121 

7.8.4 Worlccard for A-Check: Proposed Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 

7.9 C..CHECK CASE STUDY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 

7.9.1 Task Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 

7.9.2 Methods Used for the Study . . . • . . . . . • . . . . . . • . . . • . . . • . . • . . . . . • . . . . 125 

7.9.3 Results . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 

7.9.4 Workcard for C-check: Proposed Design ............................. 125 

7.10 FIELD EVALUATION OF PROPOSED DESIGNS FOR C-CHECK WORKCARD .... 129 

7.10.1 Experimental Design ........................................... 129 

7.1 0.2 Results . . . . . . . . . . . . . . . . . . . • . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 

7.11 RECOMMENDATIONS AND CONCLUSIONS .............................. 130 

7.12 REFERENCES .................•...•..•.......•.........•......... 132 

CHAPTER EIGHT - Training for Vlsnal Inspection of Aircraft Structures 

8.0 INTRODUCTION: THE STATE OF VISUAL INSPECTION TRAINING . . . . . . . . . . 133 

8.1 CURRENT METHODS IN TRAINING: AN OVERVIEW OF RESEARCH ......... 134 

8.2 TRAINING CONTENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . • . . . . . . . . . . . . 134 

viii 
Table of Contents 

8.3 TRAINING ME1HODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . 134 

8.3.1 Pre-Training ...••.•.............•..•........••............... 135 

8.3.2 Knowledge of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 

8.3.3 Guidance or Feedforward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 

8.3.4 Part-Task Training ............•....•.........•................. 135 

8.3.5 Whole-Task Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 

8.3.6 Adaptive Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 

8.3. 7 Active Training . . • • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 

8.4 TRAINING DELIVERY SYS1EMS ....•................................. 136 

8.4.1 On-the-Job Training (OJT) . . . . . . • . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . 136 

8.4.2 Traditional or Conventional Training . . . . . . . . . . . . • . • . . . . . . . . . . . . . . . . . 137 

8.4.3 Computer-Based Training (CBT) Systems ..........•................. 137 

8.4.4 Intelligent Tutoring Systems (ITS) . • • . . . • • . . . . . . . . • . . . . . . • . . . . . . . . . 137 

8.5 EXPERIMENTAL EVALUATION OF TRAINING INTERVENTIONS ............. 137 

8.6 VISUAL SEARCH TRAINING EVALUATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 

8.6.1 Can Training Improve Defect Conspicuity? .........................•. 1.:10 

8.6.2 How Effective is Feedback in Changing Search Strategy? . . . . . . . . . . . . . . . . . 142 

8.6.3 How Effective is Feedforward in Changing Search Strategy? ............... 144 

8.7 DECISION MAKING ISSUES ......................................... 145 

8.7.1 Perception of Multiple Defect Attributes: Active or Passive Training? ........ 146 

8. 7.2 lntegntion of Multiple Defect Attributes: Active or Passive Training? . . . . . . . . . 146 

8.8 TRAINING METHOD FOR AIRCRAFT STRUCTURAL INSPECTION . . . . . . . . . . . . 148 

8.9 CLASSROOM TRAINING . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 

8.10 STRUCTURED ON-THE-JOB TRAINING ................................. 149 

8.11 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 

8.12 REFERENCES . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 

IX 
Table 2.1 

Table 2.2 

Table 3.1 

Table 5.1 

Table 5.2 

Table 6.1 

Table 6.2 

Table 6.3 

Table 6.4 

Table 6.5 

Table 6.6 

Table 6.7 

Table 6.8 

Table 6.9 

Table 6.10 

Table 7.1 

Table 7.2 

Table 7.3 

Table 7.4 

Table 7.5 

Table 7.6 

Table 7.7 

Table 8.1 

Table 8.2 

Table 8.3 

Table 8.4 

Tablell.S 

Table 8.6 

Table 'd.7 

List of TtdJles 

List of Tables 

Summary of Test Statistics . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Written Responses to Poll . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . • . . . . . 11 

Miscellaneous Pen Computer Characteristics . . . . . • . . . . . . . . . . . . . . . . . . . . . 32 

Restrictive Space Factors . . . . . . • . . . . . . . . . • • . . . . . . . . . . . . . . . . . . . . . . 75 

Performance, Workload, and Stress Defined within Restrictive Space 

Framework . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . • . . . . . . . . . 82 

Levels of lllumiru:tion Required in Aircraft Inspection/Maintenance . . . . . . . • . . 94 

Commonly Used Ughting Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 

Recommended Diffuse Reflective Values . . . . . . . • . . . . . . . . . . . . . . . . . . . . . 96 

Task Ught EnVironment and Dlumination by Task Area • . • . • • . . . . . . . • . . . . 99 

Relevant Ughting Consideratiollf Based Upon Inspector Perceptions . • . . . . . . • . 103 

Specifications of Selected Pon 'ble Ughting Equipment . . • . • • . . . . . . . . . . . . . 105 

Specifications of Selected Personal Ughting Equipment . . . . . . . . • . . . . . . . . . . 105 

Ughting Recommendations for Various Tasks Based Up<.n the Tasks Demands, the 

Ughting Requirements, and the Size of the Area • . . • . • • • . . . . . • • . . • • . • • . 108 

Ughting Source Design Considerations . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . 110 

General Visual Environment Design Considerations . . . . . . . . . . . . . . . . . . . . . 110 

Guidelines for Design of Paper -based Documentation for Aircraft Inspection . . . . 117 

A-Check Workcard: Issues Identified Within the Taxonomy . . . . . . . . . . • . . . . . 122 

A-check Workcard Usag.::: Interpretatious of Inspector Responses •........... 123 

C-Check Workcard: Issues Identified within the Taxonomy ............... 1:27 

C-Check Workcard: Interpretations of Inspector Responses ................ 128 

Experimental Design . . . . . • . . . . . . • . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . 130 

Summary of the Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 

Percentage Improvement in Mean Search Times After Training for the Four Training 

Groups . . . . . . . . . . . . . . . . . . . . . . • • . . . . . . • . . . . . . . . . • . . . . . . . . . . . . 141 

Percentage Changes in Process Measures afte.r Training for Feedback 

Experiment . . . • . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 

Percentage Performance Changes by Group for Feedback Experiment ......... 143 

Percentage Performance Changes by Group for Feedforward Experiment ....... 145 

Percent Correct Decisions for Attribute Perceptions • . . • • • . . . . . . . . . . . . . . • . 146 

Performance by Group, Integration Experiment ..•.•.................... 147 

Nose Landing Gear and Wheel Well Inspection (B-Check) ................ 151 

xi 
Figure 1.1 

Figure :Z.1 

Figure :z.:z 

Figure %.3 

Figure 2.4 

Figure 2.5 

Figure2.6 

Figure 3.1. 

Figure 3.:Z 

Figure 3.3 

Flgure3.4 

Flgure3.5 

Figure 3.6 

Flgure3.7 

Figure 5.1 

Figure 6.1 

Figure 6.% 

Figun6.3 

Figure 6.4 

Figure 6.6 

Figu..ooe 6.5 

Figure 6.7 

Figure 7.1 

Figure 7 .:Za 

Flgure 7.:Zb 

Figure 7.3 

Flgure 7.411 

Figure 7.4b 

Flgure 8.1 

Flgure s.:z 

List of Figures 

1be Research Program . . . • . . . . • . . . . . . • . . . . . • . . . . . . . . . . . • . . . . . . . . . 1 

A Sample Screen from 1he ECS Tutor . . . • . . . . • . . . . . . • • . . . . • • . . . . . . . . • 6 

Design of tbe Experiment • • . • • • • . . . • . • . • • . . . . . . • . • _ . . . . • • . . . . . . . . • 8 

Overall Test Scores for Instructor-led (A) and Individual-use (B) Groups . . . . . . 10 

Tutor Preferences of 1he Two Groups, Measured by Poll Responses • . . . . . . . . . 11 

Dislribution of scores for examination sections A. B, C, and D. . . . . . . . . . . . . . 15 

E-ramination Response Disttibution for 1he Individual-use Group . . • • . . . . • . . . • 16 

Typical Desklop and Pen Computers • . . . . :-. . . . . . . . . . . . . . • . . . . . . . . . . . 25 

Comparison of CPU Type and Speed • . . . • . . . . . . . . . • . . . . . . . . . . . . . . . . 28 

Comparison of Hard Disk Capacities • • . • • • • • • . • . . • . • • . . . . . • • . • . . • • . . 28 

Comparison of Display Types • • • • • • • • • • • • • • • . • • • • . . • • • • • • • . . • . . . • . 29 

Comparison of Weights • . • • • • • • • • • • • • • . • • • • • . • • . • • • • . • • . • • . . • • • • 29 

Comparison of Battery Ufe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 

Comparison of Prices • . . • . • • • • • • • . • • • . • • • • • • • . • • • • • . • . . • . . • . • • . . 33 

, Restrictive Space Model . . . . • . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . • . . . . 7 4 

IDnminat!on by Akaaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 

Perceived Glare by Aircraft Area . • • . • . • • • . . . . . . . . . . . . . . • . . . . . . . . • . 99 

Perceived Ught Level by Aircraft Area . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 

Perceived Contrast by Aircraft Area . . . . . . • . . . . . • . . . . . . . . . . . . . . . . . . . 100 

Perceived Color Rendering by Aircraft Area . . • • . . . . • . . . . . . • • . . . . . . . . • . 101 

Perceived Glare by Aircraft Area . • . • • . . . • . . . . . . . . • . . . • . • . . . . . . . . . . 101 

Ugbting Utilizalion by Aircraft Area . • • . • • . . • . • . . . . . . . . . . • . . • . . . . . . . 102 

Sample Page from 1he Current Workcard ............................. 120 

Proposed Design for A-Check Workcard: Checklist . • • • • . • • . • . • . . • . • • . . . . 123 

Proposed Design for A-check Workcard: Detailed Information .•........... 124 

Protot}!Jle of Workcard Holder . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 

C-Check Workcard: Proposed Design • • • • • • • • . • . . • • . • • • • . • . • • . . . • • . • 129 

C-Cilect Workcard: Proposed Design- Graphics AttadlDients .............. 129 

Screen of VJSUal Simulation • • • • • • • • • . . . • . . . . . . . . • . • • . . . . . . . • • . . . . 139 

Model for Training Program Development in Commercial Aviation . . . . . • . . . . 150 

xiii 
List of Abbreviations 

AANC . . . . . . . . . . • . . . . . . . . . , • . . Aging Aircraft NDI Development and Demonstration Center 

ANOVA . . . . . . . . . . . . . . . . . . . . ...............••.....••....• ANalysis Of VAriance 

ASis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • . • . . • . • Aviation Safety lllspedois 

BITE .............•.•...............••.•..•••.....•••..•• built-In test equipmeot 

BPD . • . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . • . . • . . • • • . . • Body Part Discomfort Chart 

CAl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • . . . . • • . . • . • . • . computer-aided inslruclion 

CAMI . . . . . . . . . . . . . • . • . . . . . . . • . . . . . . • • . . • • • . • . . • . • . . . Civil Aeromedical Iustitute 

CBT . . . . . . . . . • . • . • . . . . . . • • • • . . . . . • • • . . • • • • • • • • . . • . • • • • . • computer -based training 

CD-ROM . . . . . . . . . . . . • . . . • . . . • • • . . . . . . . . . . • • • . • . . . compact disc, read only memory 

CPU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . • • . • . . . . . . . • . . • • • . ceD1ra1 pocessing unit 

ECS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • . Environmental Control Simulation 

EFr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Em~ Figures Test 

EPRI • . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . • . . . . . • . . • . • • Elec:ttic Powe£ Rese.udllilstitute 

FAA . . . . . . . . . . . . • • . . . . . . . • • . . . . . . . . . . . • . . . . • • . . . . Federal Aviation Administration 

f -c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . foot -candJI'$ 

F1M . . . . . . . . . . . • • • . . . . . • . . .•..•.......••..•..•..•.•.••••. Fault Isolation Manual 

f-1 • . . • . • . • • • . . • . . • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • foot-lamberls 

FOV . . . . . . . . . • . . . . . • . • . . . . . • . . . . . • . . . • . . . . . . • • . . . • • . . . • . • • • . . . field of view 

FI'C . . . . • . . . . . . • • • • . . . • • . . . . . • . . . . . . . . . . • . . . . . • • . . . • • . . . Feeling Tone Checklist 

IDT . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . • . . Harris Inspection '}:est 

HT A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . hie£archical task analysis 

IES • . • . • . . . • . . • . . . • • . . • . • • • • • • . • . . . • • . . • • . . • . • • . IDnminating Engineering Society 

IIMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ; . . Integrated Information Management System 

ITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . intelligent tutoring system 

KSA . . . . : . . • . . . . . . • • . . . . . . . . . . . . . . . . . • • . . . . . • . . . . • knowledge, skiDs, and abilities 

LC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . • . . • • . . . . • . • _ Locus of Control 

LRU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . line replaceable unit 

MFFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Matching Familiar Figures Test 

MSACL . . . . . . . . • . . . . • . • . . . . . . . . . . . . . . . • . . . . . . • . MOdified Stress-Aro"oJSal Checklist 

tliEC . . • . • . • . • • • . . • . • • . • • . • • . • • • . • • • • . • • • • . • • . • • • • • . • • • National Electtical Code 

NDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . , nondestructive inspection 

NDT . . . . • • . . . . • . . . . . . . . . . . • . . . . . • • . . . . • . • . . . . • . . . . . . . . • . • . noodestructive test 

NiCad • . . . . • • . . . • • . . . . . . . . . . • . • • . . . . • . . . . . . • • . . . • • • • • . . • • • . • • nickel-cadmium 

XV 
orr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . On-the-Job Training 

OSHA . . . . . . . . . . . . . . . . . . . . . • . • . . • . . . . . . . Occupational Safety & Health Administtation 

PCMCIA . . . . . . . . • . . . . . . . . . . . . . . Personal Computer Memory Card International Association 

PENS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pens ENhancement System 

POD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . probability of detection 

R.I.I. . . . • . • . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Required Inspection Item 

ROC . . . . . . . . • . . • . . . . • • . . . • . . . . . . . . . . . . . . . . . . . . . . . receiver operating characteristic 

ROM . • . . . . . . . • . . . . . . • . • . . • . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . read only memory 

SA TO . • • . • . • • . . . • . . . • . • • • • . . . • . . • • • . . • • . . • . . . . . . . • . . . . . speed/accuracy tradeoff 

SDT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . signal detection theory 

SUNY . . . . • . . • . . . . . • . • . . . . . • . . . . • . . . . . . . . . . . . . . . . . . State University of New York 

SwRI . . • . . • . . • . • • . • • . . . • . . . . . . . . . . . . . . . • . • . . • . . • . . . . Southwest Research Institute 

n.x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Task Load Index 

USAF . . . . . , . • . • . . . . . . • . • . . . . . . . • . . . . . . . • . . . . . . . . . . . • . . . . United States Air Force 

W AIS .....•.•..•••.••.......•••............•..... Wescblec Adult Intelligence Scale 

XVI 
1.1 SUMMARY 

Chapter One 

Phase m Overview 

Plulse m 011e1'11iew 

This is Volume I (of II) of the Phase Three report of the Office of Aviation Medicine research program 

on Human Factors in Aviation Maintenance and Inspection. The research pl"Ogram has matured since it 

began in 1989. Figure 1.1 shows tbat the research program has fully transitioned to the final stages of 

Implementation/Evaluation. The government and the aviation industry have begun to embrace a"'.d adopt 

the products of the research program. 1bese products and research results are described herein. 

The success of this research and 

development pl"Ogram is founded on 

the principle that "good science" must 

be the basis for "good practice. • 

However, basic scientific research 

An Ongoing Research & 

Development Program 

must not be confined to the laboratory 

- end users must be involved in all 

stages of the research. This research 

I Investigation/Problem Definition 11-

+ 

attributes its success to the active IProtolypasJDemonstrations 

participation of end users. lbose 

participants include the FAA Flight 

Standards Service; industry 

consortiums like the U.S. and 

International Air Transport 

I Implementation I Evaluation I--

Association and the Aviation 

Technician Education Council; 

individual airlines like Delta, 

Continental, USAir, Northwest, Figure 1.1 

United. and others; and labor 

Industry Adoption of 

Reoearoh Prod,.ots 

The Research Program 

representatives like the International Association of Machinists. Under such guidance the various members 

of the research team have been able to develop, implement, and evaluate human-centered maintenance 

performance enhancements. 

Each chapter contained in this volume addresses an aspect of performance enhancement. The research 

program re.:ognizes tbat outputs must have a focus on safety and on cost control. Our current air 

transportation system is safe and all trends show increasing reliability and safety. The safety must 

continue in concert with cost control. Cost control means working smarter. reducing errors, reducing tlight 

delays or cancellations, and geDmilly improving the overall efficiency and effectiveness of tbe human in 

the total aviation maintenance system. 

1.2 AN AIRLINE EVALUATION OF ADVANCED TECHNOLOGY TRAINING (Chapter Two) 

During Phase I and n of the Aviation Medicine Human Factors in Aviation Maintenance and Inspection 

research program, training was a key research topic. A key product of the initial phases was advanced 

1 
Chapter One 

technology computer-based training foc technicians. The focus of training is the Boeing 767-300 

environmental conttol system (ECS). The training system includes an operational simulation of the ECS 

and a robust method of tracking student performance and providing advice and feedback. 

This third phase of the research had the go'll of evaluating the instructional effectiveness m an airline 

training setting. A formal evaluation was conducted comparin!! individualized student computer-based 

training (CBT) versus instructor-lead CBT. Results of the experiment are reported in this section. The 

results should be helpful to trainiD.g personnel as they make de<;isions regardiD.g the best application of 

instructional technology. 

1.3 IMPROVING PERFORMANCE WITH BETTER INFORMATION CONTROL (Chllpter 

Three) 

The .P.erformance ENhancement .fu'stem (PENS) is beiD.g designed for the 2600 Aviation Safety Inspectors 

(ASis) of the FAA Flight Standard Service. PENS capitalizes on advanced technology software and 

hardware to improve the collection. storage, analysis, and distribution of field data. Chapter Threl! 

describes the requirements analysis, early design and evaluation of a variety of hand held portable 

computer systems. 

1.4 PERFORMANCE IN INSPECTION TASKS (Chapter Four) 

Aviation maintenance requires the highest quality assurance. Thus, continumg inspection is a critical 

component of quality. This chapter describes an example of the laboratory research underway to identify 

cha~iictecistics of personnel best suited to inspection-oriented jobs. 

The chapter reviews over twenty-five years of Department of Defense literature related to personnel and 

inspection. 

l.S ERGONOMIC FACTORS AFFECTING POSTURE AND FATIGUE (Chapter Five} 

Aviation maintenance tasks require the technician to bend over, squat, and perform a vaiiety of anatomical 

contortions. Such forced changes iD. posture iead to fatigue, back and limb soreness, and perhaps, error. 

This chapter, first, reviews the research literature related to such topics as the followmg: restrictive space 

factors, stre:JS, and fatigue. Second, the chapter presents a plan to identify aviation maintenance tasks that 

are likely to force unna1Ural posture and, thus, increase 1be likelihood of fatigue and resultant error. 

Wtimately this research will prescribe a program to identify maintenanoe tasks where posture demands 

are beyond that at which a human can perform safe and reliable work performance. The research will 

offer ways to improve human performance under such conditions. 

1.6 AN EVALUATION OF THE AIRCRAFf MAINTENANCE VISUAL ENVIRONMENT 

(Chapter Six} 

v;sual inspection accounts for 90% of all inspection activity. Therefore there is a high value in research 

that will improve the inspection visual environment This study used a visual environment evaluation at 

the facilities of an airline partner to develop a general methodology for recommending the correct 

equipment Ambient illumination must be supplemented by both portable area !ightiD.g and personal light 

2 
sources to achieve the necessary Illumination levels. 'The importance of a glare-tree visual enviromnent 

that makes use of surface reflectance is stressed. 'The developed methodology used task analysis data, 

lighting evaluations, input from inspectors and G.e evaluation of light sources to specify better er, !lipment 

and visual surroundings. 

1.7 A REDESIGN OF MAINTENANCE WORK CONTROL CARDS {Chapter Seven} 

Aircraft maintenance and inspection is often driven by workcards. They p-esent a detailed and organized 

ordering of the subtasks necessary to complete a job. This chapter describes an effort to improve the 

method in which workcards are designed and presented to the aviation maintenance technician. 

As part of this project new workcards were designed for A-check and C-check on DC-9 aircraft. 'The 

results of an airline evaluation are reported. Not only does this chapter propose specific design solutions, 

but it also provides a highly generic ll'.ethodology for design of quality technical documentation, both 

written and digital. 

1.8 TRAINING FOR VISUAL INSPECTION ~Chapter Eight) 

During previous phases of the research a computer-based simulation was built for laboratory research on 

training for visual inspection. This chapter summari-res the results of laboratory experiments and offers 

concrete examples of the necessary components of a training program for visual inspection. 

This charter reports on the status of visual inspection in airlines. aircraft manufacturers, and other nonaviation maintenance enviromnents. The chapter describes training alternatives such as part-task, wholetask, adaptive, active, on-the-job, and computer-based training for visual inspection. 'The chapter also 

describes training and inspection feedback that is likely to improve technician performance in visual 

inspection. 

1.9 CONTINUING RESEARCH 

Phase III, Volume II will be published about four months after this volume. The next volume will place 

increasing importance on the measurable impact of the research on human performance enhancem.ont The 

aviation industry is struggling through increasingly difficult financial hardships. Research programs must 

continue to improve the "bottom line" by providing procedures and products that improve maintenance 

efficiency. That will remain a highest priority of this program. 

3 
·"" -

Chapter Two 

Results of the Environmental Control System Tutor Experiment 

2.0 INTRODUCI'ION 

lbis study investigates the effect of presentation methods on computer-based training effectiveness. The 

ex¢riment was conducted at the technical operations training center of a major airline in the Fall of 1992. 

Subjects used the Environmental Control System Tutor with both instructor-led and individual-use teaching 

methods. The experiment found no significant difference in overall performance between the two groups, 

although the instructor -led group did perform slightly better on the part identification section of the 

examination. Also, the experiment found no significant difference in the preference of the presentation 

method betw~ the two groups. lbis report also covers shortcomings in the design of the experiment 

2.1 PURPOSES OF THE EXPERIMENT 

The study bad two motivations: verification of the ~ffectiveness of the tutor and comparison of computerbased training (CBT) methods. FJCSt, we wanted to ensure that the use of the Environmental Control 

System (ECS) Tutor will improve the students' performance in diagnostic tasks. We have already 

conducted several informal usability studies that looked at the compatibility and understandability of the 

tutor as described in Pearce (1992), and felt it necessary to perform a formal effectiveness study of the 

tutor for final evaluation. By comparing the performance of technicians who have used the tutor with the 

performance of subjects who have been taught with traditional methods, we were able to get a better idea 

of the strengths and weaknesses of the ECS Tutor. In addition to testing, we also collected data on the 

opinions of the subject concernlng the tutor, to see lf there are problems with the design or implementation 

of dte tutor. 

Second, we wanted to compare the effectiveness of presentation methods for CBT systems. The two toplevel classifications for presenting CBT systems are the instructor-led and individual-use methods. The 

instructor -led method is the traditional mode of teaching, in which the teacher controls the presentation 

of material. In the individual-use method, each student controls his or her own learning process. Several 

studies have compared the efficiency of these two methods for general instruction (Charney and Reder, 

1986; Czaja et al., 1986), but no studies could be found that have compared these methods for teaching 

troubleshooting. The information obtained from these results will help to determine specific components 

of CBT systems that improve student performance. The data from this study will also be useful in the 

evaluation of the cost effectiveness of computer-based training systems. 

2.2 ENVIRONMENTAL CONTROL SYSTEM OVERVIEW 

The ECS, found in all modem airliners, controls the pressure and temperature of air in the airplane. The 

ECS of the airliner that the tutor simulates consists of three control and display panels in the cockpit. 

several electronics modules in the avionics bay, the distribution system, and the two cooling packs located 

in the fuselage. The ECS is a very complex SYstem and consists of electrical, mechanical, and air flow 

subsystems that interact to provide the cool, pressurized air. It was chosen for the training domain of the 

tutor because !be ECS is fairly common across airliner types, and therefore the training could be 

5 
Chapter Two 

generalized across airliner types. Built-In test equipment (BITE) of modem airliners makes the job of the 

technician easier, since it tests some compoueots with the push of a button. Not aD compoll£llts are tesled 

by the BITE. so the technician must know wben and bow to use external test equipment to isolate 

malfunctions. 

2.2.1 The Flighotne Technldan 

The flightline technician must quickly diagnose and repair malfunctions on the aircraft on which they are 

certified to work. Technicians must know about the systems of several different types and models of 

aircraft Tbelr task is time constrained, since most flights bave about 40 minutes on the grol1lld between 

landing and takeoff. Also, some repairs take more than 40 minutes, and the technician must find these 

faults quickly to minimize delays in the flight schedules. 

It is standard procedure for the flightline mechanic to use the Fault Isolation Manual (FIM), which is a 

logic tree used to diagnose malfunctions. The technician follows the branches of the FIM based on the 

outcomes of tests and inspections. The FIM specifies a "minimal path" of actions to repair a failure, from 

the high-level description of the malfunction to the malfunctioning component. In some cases, it is 

possible to diagnose malfunctions with a single test (for example, by looking for abnormal temperatures 

in the airflow path), so in practice the FIM is not always used. 

2.2.2 Overview of ECS Tutor 

The ECS Tutor is a computer-based 

training (CBT) system that trains 

aircraft technicians to diagnose and 

repair malfunctions of the ECS of the 

Boeing 767 (Figure 2.1). The tutor 

contains a deep simulation model of 

thP. ECS, which allows the user to see 

the consequences of his actions on the 

system down to the sensor level. The 

user can change switch settings to 

observe the values of various system 

parameters. Tbe tutor is also highly 

graphical, allo\\-ing for direct 

manipulation ofECS components, and 

contains realistic pictures an<! 

animations of system components and 

schematics. 

The. tutor allows four types of actions 

on the components of the ECS: operate, inspect. test. and replace. The first is to operate the ECS 

equipment. For example, the student can change switch settings of the cockpit control panels. The second 

action is to inspect a component; this action includes reading of display values on control equipment or 

looking for visible failures in pack components. The next action, test, differs from inspection in that the 

technician bas to perform some type of action, usually operating some internal or external test equipment, 

6 
rather than just observing a component. One example or tbls actiVity is wben tbe technician tests tbe pact 

controller by operating tbe BITE. The last action, replace, allows tbe usu to swap out liDe replaceable 

units (LRU's) with worldng compoDCDts. 

2.3 METHOD 

The experiment was designed to measure differences in performance between students taught to 

troubleshoot using a "traditional" instructor-led training method and an indiVidual-use training method. 

Because the participating airline does not give a formal course that explicitly teaches troubleshooting 

skills, we had to design a short instructor-led CBT session based on traditional teaching metbods. To 

standardize the information that was being presented in both groups, the instructor for the instl'~ctor -led 

group presented the same version of the tutor that was used by tbe subjects in the individual-use group. 

The only difference between the two groups was in the method of presentation; the individual-use group 

interacted directly with the tutor, while the instructor-led group had this information presented by an 

instructor. Thus any differences in performance could be attributed to the method of presentation, rather 

than any differences in content. 

2.3.1 Subjects 

The subjects participating in the experiment consisted of 10 ground training instructors and 10 fligbtline 

technicians. All of the subjects had some level of general knowledge of the operation of ECS, from either 

troubleshooting experience or courses on the ECS's of other aircraft None of the subjects had worked 

on the Boeing 767 ECS. Instructor experience ranged from two to 19 years as instructors, while all of 

the flightline technicians had less tban two years experience as aircraft technicians. Subjects were 

randomly assigned to one of the experimental groups, with half the instructors and half the technicians 

going to each experimental group. 

2.3.2 Procedure 

The experiment was divided into three phases: introductory lesson, tutor usage, and testing (shown in 

Figure 2.2). All of the subjects participated in an introductory lesson on the basic operating principles 

of the B-767 ECS. This course, developed by an instructor of the technical operations training department 

of the participating airline, covered the general operation of the B-767 ECS, modes of operation of the 

ECS, and the functions of the sensors, valves, and eiectronics that control ECS operation. All subjects 

went through this one-hour course before participating in the tutor usage portion of the experiments. 

After this one-hour course came the tutor usage phase, in which the students were split into the two groups 

("instructor-led" and "individual-use") for the 2 1n hours troubleshooting training course. Each member 

of the individual-use group used the ECS Thtor individually to solve as many problems in the tutor as 

possible in the allotted time. The students used the tutor on the participating airline's training computers. 

The instructor-led group was given a stand-up lecture on ECS troubleshooting, with the instructor using 

the ECS Tutor as an instructional aid This tutor usage phase was stopped for both groups when the 

instructor finished all ten problems in the tutor. Thus the time of instruction was the same for both 

groups, except for the three subjects in the individual-use group who finished early. 

7 
ClulpterTwo 

2.3.3 Data 

After the instructor-led group bad 

finished all 10 troubleshooting 

problems in the tutor, both groups 

were given a short examination that 

measured troubleshooting skills. 'Ibis 

one-hour ell'amination, developed by 

an instructor at the participating 

airline, was designed to measure a 

variety of skills. Most of the 

questions were multiple choice, With 

some fill-in-the-blank questions. 

Questions were divided into four Flgure 2.2 

sections, and data was collected on 

completion times for each of these 

3hoLn 

Design of the Experiment 

sections (the questions are described in the "Results" section). During the examination the subjects could 

use a diagram of the ECS and the fault isolation manual to help them solve all the problems. 

The exam also contained a poll With questions about the user's satisfaction level With the tutor. We also 

administered a background poll to determine the distribution of skill levels for computer use and ECS 

maintenance. After the subjects finished the examination and polls, they were asked to write about any 

impressions or observations concerning the tutor. 

2.4 RESULTS 

This section is divided into an Examination results section, covering the analysis of the data from the tutor 

examination, the Examination Ctmlnl£llts section, which describes the results of the 1;10ll, and the Written 

ctmtn~£~~ts section, covering the written comments concerning the tutor. 

2.4.1 Examination Results 

The examination contained 23 questions, divided into four question types: components, procedures, 

systems, and troubleshooting. Component questions measured knowledge of the parts of the ECS. The 

procedure questions measured knowledge of the procedures necessary to diagnose the ECS. Sys-.ems 

.• uestions addressed the vadous control systems and their relationships. The largest part of tb'<' ex:uniru!tion 

was the malfunction section, wbich tested knowledge of troubleshooting performance or. the B-767 ECS. 

Scores on lhe questions were weighted by difficulty; for example the troubleshooting questions counted 

about twice as much as the component questions, because they were more difficult and time consuming. 

The only significant difference between the group's scores was in the component section. These questions 

dealt with the ECS on a component level; for example these questions concerned the function. of the parts, 

connections to other parts, or behavior of a specific part. 1bere were two main reasons for the superior 

performance of the instructor-led group in the component-related questions. First, since th:: ECS Tutor 

does not explicitly teach the user about the ECS at the component level, the individual-use subjects were 

disadvantaged when it came to learning about the parts of the system. Second, students in the instructor8 
Results of the E1111ironmenllll Control System Tutor Experiment 

led group could ask the instructor to explain the finer points of the operation of the ECS, and the 

instructor would often answer questions by describing the behavior of one of the components. On the 

other hand, students in the individual-use group could ask the tutor about a component by clicking on one 

of the "Help" buttons, but dialog with a computer is not always as robust or meaningful as that with an 

instructor. 1bis result. alo11.g with several of the written comments, points out the importance of giving 

adequate background information before attempting to teach troubleshooting. 1bis b&ekground information 

could be taught with the computer, although in many cases it may be more effective and efficient for an 

instructor to teach this material. 

The examination data showed no significant difference between the two groups in the time to comple:e 

the examination or in the weighted overall examination scores, as shown in Table 2.1. 1bis is shown 

graphically in Figure 2.3, which is a "box and whiskers" plot of the median (line in the box), the first 

standard deviation (the box), and the second standard deviation (ends of the whiskers) for the overall 

scores of the two groups. Also, there was no significant difference in performance on the procedures, 

systems, and troubleshooting sections of the examination. There was also no significant difference in the 

average time that it took to complete the examination. Figure 2.5 in the Appendix A shows the score 

distributions of the two groups for the four examination sections. 

Table 2.1 Summary of Test Statistics 

Instructor-led Individual-use 

Time to OOI!1llete test 31 min. 32min. 

Average component (A) score 80.0"/o 46.7% 

Average procedure (B) score 73.3% 63.3% 

Average system (C) score 63.4% 54.8% 

Average troubleshooting (D) score 71.3% 76.6% 

Average overall score 70.3% 65.1% 

2.4.2 Examination Results 

The examination contained 17 questions about various aspects of the tutor. Questions were of two types: 

general questions dealing with the usability and general behavior of the tutor, and questions about several 

features of the tutor. Subjects were asked to rate their agreement with each statement, using the scale 

"agree strongly," "agree," "no opinion," "disagree," and "disagree strongly." The questions were equally 

mixed between ~tively and negatively phrased sentences. Figure 2.6 in the Appendix A shows the 

distributic;: of responses for the subjects in the individual-use group. 

Overall, satisfaction with the tutor was high. Some subjects in the individual-use group thought that the 

tutor behaved in unexpected ways. Ongoing usability studies are being used to locate the source of this 

problem. Also, fine-tuning of the context -sensitive help will improve the system's ability to offer 

guidance to the user at the appropriate time. There were no strong negative responses to the overall 

9 
ChaptuTwo 

design of tbe tutor or to specific 

features, lllthough the responses to 

several questions indicated that the 

wording of error messages could be 

improved. 

A comparison between the two groups 

showed no significant difference in 

satisfaction wilh the tutor. This 

comparison was done by removing all 

examination questions that were not 

relevant to satisfaction or were not 

100% ;;;;--

90%~ 

80%'-

70%~ 

60%f50%'-

i 

4) 

) 

relevant tu bolh user groups. The 

negatively-phrased questions were 

then inverted, and then the responses 

for each question were sorted by 

value, wilh "one" being the highest 

level of agreement and satisfaction, 

and "five" being the lowest. The 

distributions for the two groups are 

shown in Figure 2.4. The two 

40%~----._·------------~·-----

distributions are almost identical, 

indicating that preference for the tutor Figure 2.3 

wu independent of the me1hod of 

presentation. This seems to indicate 

that the positive features of instructorlnstructor Individual 

led use 

Overall Test Scores for Instructor-led (A) aDd 

Individual-use (B) Groups 

led instruction (for example, natura! instructor-student dialog) wm: balanced by the positive features of 

individual-use instruction (for example, full control over instructional rate). 

2.4.3 Written Comments 

The examination asked the subjects to write down any specific Jr(lblems that they had with the tutor, and 

about their general opinion of the tutor. Only four subjects (of twenty total) responded to tbis section, 

all of whom were in 1he individual-use group. Table 2.2 sbows all Qf 1be written comments from tlle 

examination. 

2.4.3.1 Hardware aDd Software Bugs 

The written responses indicated several different problems that subjects had wilh the tutor and the training 

program. On 1be first level were problems wilh the computer hardware. Since there was not enough time 

to allow the students to calibrate their own touchscreens, tile touchscreens were calibrated by one of the 

evaluators. But individual differences in height, handedness, and hand-eye coordination were significant 

enough to cause problems for some subjects. Since not all user's actions are confirmed, some errors in 

screen touching were attributed to logic errors by 1he tutor. 1bere was no way to correct these problems 

during the experiment, and several users became lnitated at being "falsely accused" of ma!cjng mistakes. 

Similarly, 1be tutor would unpredictably crash on two of the training computers, and the subjects wnuld 

10 
ResUlts of the EnvirolfiMntlll Control System Tutor Erpufmmt 

have to start again from the 

beginning. Thus some individual-use 

subjects paid nrore attention to the 

mechanics of using the tutor, rather 

than focusing on the content of the 

tutor. This software problem was 

found after the experiment and has 

been fixed. 

Instructor-led Individual-use 

60 - aor 

50 - .... 50 i- r40- 401 !- ,... ;-

3IJ ~-

=~n r- 20~;- r10 !·· 

n ! 0 

liked disliked liked disliked 

. Figure 2.4 Tutor Preferences of the Two Groups, 

Measured by Poll Responses 

Table 2.2 Written Responses to Poll 

Subject B-49: 

This training without an instructor is close to useless; H should only be used to enhance the class. 

Subject B-50: 

ECS Tutor is very affective, but takes time to get relaxed with. For someone with a lot of computer 

background tha ECS Tutor would help a great deal. 

Subject B-55: 

1) Arrow was not always accwa!e; touch screen was not aligned correctly 

2) No chance to correct yourself if computer made wrong selection, because of poor alignment! 

3) Twice system locked up - may be Delta's computer net program - and made student go to 

beginning of lesson and the time and mistakes shown at end of lesson were unrealistic 

Was very interesting thanks. 

Subject B-56: 

I found it frustrating when I tried to get back to a problem to see how it was written. The backup 

selaction would only take me one screen back but not any further. 

I did not like the CBT simply because it did not answer my questions, only gave me information that 

the program thought I needed. 

2.4.3.2 Response Time 

Another problem some subjects bad with the tutor was the long lag between the time that the students 

performed an action and the time that the tutor responded to that action. The computers used for 

development were two to three times as fast as those used for the experiment, and the lag was not 

significant on the development computers. The lag was much more noticeable on the computers used in 

the experiment. The subjects would sometimes repeat an action several times if there was not feedback 

showing that the computer was processing their input As a result, user actions were applied to subsequent 

displays, which led to unwanted behaviors in the tutor. 

11 
2.4.3.3 Navigation 

Some subjects were also uncomfortable with tbe behavior of navigation between screeus. For example, 

tbe version of tbe tutor that was used in tbe experiment had a "back" button that allowed the user to toggle 

back and forth between tbe previous two screens. In designing tbe tutor we tbougbt that this would be 

as nmch as tbe user would need. and went with this simple design. But tbe users expected that the button 

would csuse tbe tutor to keep going back to previous screens until they arrived at the starting screen. 

1bere were several times when it would be faster to have tbe button work in tbe expected way, and some 

users became fruslrated when it did not work the way they wanted. Earlier testing did not indicate that 

this was a problem; only in a classroom setting did it tend to confuse the users. 

2.4.3.4 Time Constraints 

Probably the largest source of frustration was the limited information that tbe subjects had about the ECS. 

In tbe standard two-week training course that technicians must take before being certified ou a plane type, 

about five hours are spent on the ECS. But because of time limits, only one hour was spent on this 

background material. Thus there were many uncertainties about tbe ECS, which led to frustration when 

trying to use the tutor. In retrospect. more time should have been spent on the introductory part of the 

experiment 

These results show that it is important that the subjects have all tbe necessary background information. 

Students that lack the prerequisite knowledge will have trouble in learning complex reasoning tasks such 

as troubleshooting. Also, having robust, usable tutoring software that has been thoroughly tested on tbe 

target platform is important Software that is frustrating to use will not have the full impact of usable 

software. 

2.4.4 Caveats 

Although we did our best to ensure that tbe ECS Tutor experiment was a valid experiment, there were 

several problems with tbe design of the study. These problems are quite common in the design and 

execution of training evaluations (Goldsteln 1987). The problems that we experienced were not a result 

of poor planning, but had more to do with constrained resources. These problems need to be considered 

when drawing conclusions from this study. The problems have to do with sample size, experience level 

of tbe subject&, and tbe testing of troubleshooting skills, and are described below. 

2.4.4.1 Subject Group Sample Size 

It is difficult to draw hard conclusions from subject groops that are smaller than 40 persons. Individual 

differences play an important role when population sizes are small, as they were in this experiment Most 

of tbe results were not statistically significant, but this could be from indiv.dual differences between tbe 

two groups, and not because of inherent differences in tbe efficiency of tbe teaching methods. Future 

studies should use larger subject groups. 

12 
Ruults of 1M Environmental Control S:ptem Tutor Experiment 

2.4.4.2 Experience Level of Subjects 

Anothfl" problem had to do with the experience levels of the subjects. Of the twenty subjects, ten were 

experienced instructors with between two and 19 years experience, &nd the othfl" ter participants were 

flightline technicians with less than two years experience. This should be compared with the two goals 

of the ECS Thtor: to teach general troubleshooting skills, and to teach specific knowledge to troubleshoot 

the B-767 ECS. The first goal, teaching general skills, is the most important of the two, as general skills 

can transfer across in.<tances of airliner troubleshooting, and across airliner types. Clearly, the participants 

in the experiment already had strong troubleshooting skills, although they did not have specific knowledge 

of the B-767 ECS. Because of the mismatch between the intended users and the actual users of the tutor 

in this study, it would be very unlikely for any teaching method to cause a measurable difference in 

performance, since most of the subjects were already fairly knowledgeable about troubleshooting. 

2.4.4.3 Testing Troubleshooting Skills 

The last problem has to do with the difficulty of testing troubleshooting skills. Because troubleshooting 

requires a combination of several types of skills and knowledge, tests that attempt to measure 

troubleshooting skills should also measure a variety of skills. It is also difficult to design an examination 

to measure this knowledge "out of context," because performance on the job may be very different from 

performance in the classroom. In an ideal experiment, the subjects would have been tested on real 

equipment and evaluated by a panel of experts, but this was not possible. Future examinations should 

attempt a more realistic task for measuring troubleshooting skills, even if the testing must be done on 

paper. 

2.5 CONCLUSION 

The experiment found no significant difference between the troubleshooting performance of subjects that 

used the tutor in instructo£-led and individual-use modes. An analysis of the performance on the four 

question types (components, procedures, systems, and malfunctions) also found no statistically significant 

difference. An analysis of user satisfaction with the tutor found no difference between the two groups. 

Possible problems with the significance of 1hese results are small population size, experience levels of the 

subjects, and difficulty of testing troubleshooting skills. 

'Ibis experiment also led to several important points to be considered in designing CBT courses and CBT 

evaluations. Fust, the subjects should have all the necessary background information, since students who 

lack the prerequisite knowledge will have trouble in learning complex reasoning tasks. Also, having 

robust, usable tutoring software that has beet. thoroughly tested on the target platform is important. 

Diflicu..lt software that is frustrating to use will not have the full impact of usable software. 1bird, because 

individual differences play an important role when population sizes are small, studies should use larger 

subject groups with at least 40 subjects. 

2.6 REFERENCES 

Charney, D. H., and Reder, L. M (1986). Designing interactive tutorials for computer users. 

Human-Computer Interaction, 2. (4), 297-317. 

13 
Clulpto Two 

Czaja, S. 1., Hammond, K., Blascovich, 1. 1., anu Swede, H. (1986). Leaming to use a word-processing 

system as a function of training strategy. Behavior and Information Technology, 5, (3), 203-216. 

Goldstein, L L (1987). The relationship of traiDIDg goals aDd training systems. In G. SalveJJdy (Ed), 

Handbook of human factors (pp. 963-975). New York: John Wlley & Sons. 

Pearce. M. C. (1992). Report on the environmental control system tutor usability study at clayton state 

college. Unpublished manuscript. Galaxy Scientific Corporation. 

14 
1.1 

.01 ~ 

s 

c -

D 0 .116 - r 

e 

.84 r-

.02 r-

.DI 

A B 

G-p 

Results oftM Enviromullllll Control System Tutslr Ezperiment 

ChaptecTwo 

Appendix A 

. s 

c . • 

r 

e . 

. 

l.D 

. 08 

.llli 

.D4 

.02 

.oo 

.... 

- . 

-

- '--- - 0 

-

.\ B 

Group 

Scores for Test Section A Scores for Test Section B 

1.1 

.01 

s 

e 

0 .05 

r 

e 

.04 

.02 

.DI 

Figure 2.5 

• 

1.0 ,L j_ 

.aa r- - s f-- -- c 

0 .86 - r 

e 

.84 -

.02 

.00 

A B A B 

Gnoup Greep 

Scores for Test Section C Scores for Test Section D 

Disttibution of scores for examination sections A, B, C, and D. These "box and 

wblskers" show tbe median (liDe in tbe box), the first standard deviation (the box), and 

the second statv!ard deviation (ends of the whiskers) for the section scores of the two 

groups. Group A was instructor-led and Group B was ilL.vidual·use. 

15 

- ••• ~ ' > 
... 

01 

Flpre l.6 

-=IV .... no opinion dlo0 C> C> 

<====== 

dlollllf\'! otrong,. 

* 

* 

I. Tlleoptomc"'"m-•ro-touoo. 

a. llaoloompolont -tho optom ...... -

•• Whonlgaton onar .,._ Ills nal helploltn lclontllylo!g tho pmll!om. 

4. Thoro orolciomony~ ond-loto ..... 

1. The tulor lleh-ln ""V8-I dkln'loxpoot. 

1. I have- romombo~ngthoaommondl ond op1tone. 

7. The optom woo nattnUmldoltng, lfoll oomtortll>lo utlna n. 

e. I often know m.otto do, bull dklll't -._to don. 

1. The'hlnlo"lhlloUQIIOIIM .,-to till or ,.,.._won Olllut. 

to. Tile holp -on• provtdlclooolullnlormotlon In ootvlna the pmll!omo. 

11. Tile lanoni.--M helpod mo underotand tho motlunottono. 

Ill. I did nal k.--to do olltr roploolna a component. 

11. Tile 'Info" bor .elho boiiGm er aorun helpoti!OO unde,.tand the optom. 

14. Tile FIM ,.,. woo eaayto uound helpotlln ootvtna pnlll!lm. 

11.1 coUld nal tall whallbo ptcluroo Cll ECI .,-wo,. ouppoaad to bo. 

II. Tlletouohloroon-onyto..._ 

n. Tile compulerwoo otaw In roopondtng to my aholo ... 

Examlnadon Response Dlstrlbudon for the Individual-use Group 

f 

f 
Resu/Js of the Environmenllll Conlrol System Tutor Experiment 

Chapter Two 

Appendix B 

ECS Tutor Evaluation 

Evaluation# __ _ 

nn~ ('valuation will measure your knowledge of the B-767 ECS and of troubleshooting procedures. 

1b::: evaluation is to be g!vea afte£ you bave seen the ECS Tutor, and is divided into background and 

troubleshooting questions. The background questions will measure your knowledge of the various 

component, systems, and procedures related to the ECS. The troubleshooting questions measure your 

ability to diagnose malfimclions of the ECS. 

Most of the questions are multiple cboice; simply circle the letter in front of that answer you think is 

correct If you need more room for the "short answer• questions, continue on the back of that page, 

but the answers should not tie very long. 

You may use the materials from the introductory section of the evaluation (the pack diagram. 

equipment .:lrawings, and FIM), including any notes you took. 

For each of t~ sections, you should write the times that you begin and end that section; an area is 

provided. You should not rush to finish the evaluation; correctness is more important tban time. 

The last two pages of this package are forms that ask your opinion of the tutor and about your 

experience with ECSs. Please tate the time to fill these out, as they will infiuence the changes that are 

made to the tutor. 

NOTE: This is not a test! This results of this evaluation are confidential and will not be used to 

evaluate you. You should not sign your name to this evaluation. The study is designed to evaluate the 

ECS Tutor, and not the people taking this evaluation. 

17 
ChaptuTwo 

A. Components 

These questions will evaluate your knowledge of tlle parts of tlle B-767 ECS. These questions are all 

multiple choice; just circle tlle correct answer. 

Start Time: __ _ 

l. The function of tile Prlmary Heat EW!angec Is to: 

A. limit flow of bleed air into tile pack. 

B. cool the air before it enters tbe compressor. 

C. cool bleed air coming out of the compressoc before it enters the condensec. 

D. none of the above. 

2. The low limit valve: 

A. receives ditferenlial pressure to comma!!d lbe valve. 

B. can receive an electrlcal command ftom lbe standby pack controllec to command 

lbe valve. 

C. can receive an electrlcal command ftom the pack tempera111re controllec to 

command the valve. 

D. all of the above. 

3. When performing a pack temperature controllec BITE, the pack sensor is faulted. Where Is the 

sensor located? 

A. In the ceiling of the cabin. 

B. Between the primary water extractor and tlle turbine. 

C. Near tlle flow control valve. 

D. Downstream of tlle tuibine. 

Finish Time: __ _ 

18 
RUJilts of the Enviro1U11ental Control System Tutor Experlmml 

B. Procedures 

The questions in this section will measure your knowledge of the procedures necessary to diagnose the 

B-767 ECS. You will be given a task, and must describe the steps to perform the task. For the "short 

answer" questions, please include an explanation. 

Start Time: __ _ 

4. On the pack temperature controlla-, if you press the PRESS lEST switch and the GO light does not 

illuminate, you should: 

A replace the componeuts with the lights illuminated 

B. press the VERIFY switch to reset the controlle£. 

C. replace the controlla-. 

D. replace the faulty lamp. 

5. A B-767 has a problem with the ECS system. Using the FIM and fault code 21-51-19, go to the 

appropriate chart to filld the fault. Starting at block '11 answer YES. The next block would be 

answered NO. Wbat is the problem? 

6. A B-767 has a problem with the ECS system. Using the FIM, fiDd the correct fault code. On the 

ova-head panel with the pack selector switch in "AUTO," the "INOP" light on the reset switch is 

illuminated. When STBY was selected the light extinguished. Wbat is the fault code for this problem? 

Finish Time: __ _ 

19 
Chllpter Two 

C. Systems 

This section will measure your lalowledge of the various systems and the relationships between 

components of the ECS. The goal is to measure what you lalow of tbe behavior and functioning of 

tbe pack. 

Start Time: __ _ 

7. What controls the pack wben tbe selector switch is in auto? 

8. Wbat conttols the pack wben tbe selecu switch is in STBY N? 

----------------------~and ______________________ __ 

9. Circle the coaect answers: In STBY C tbe Low Umit Valve is normally (closed, open), and lbe 

Temperature COnttol Valve is normally (closed, open). 

10. If 1be INOP light and tbe PACK OFF lights are illuminaterl on the reset sWitch in the AUTO 

position, the problem is wilh tbe 

. A Trim Valve failed. 

B. Pack Outlet oveztemp. 

C. Gasper Fan failed. 

D. Compressor Outlet overtemp. 

II. Wbat is tbe purpose of tbe altitude switch? 

A to increase airflow through the pack at 31,000 feet, since tbe air is tbiDner 

at higher altitude. 

B. to allow colder air to the turbine at 31,000 feet 

C. so tbe EICAS can record tbe altitude on tbe autoevent if tbe pack fails. 

D. all of tbe above. 

12. Wbat indication would you get in tbe cockpit if the altitude switch failed? 

A Failure flag on tbe captaiDs allimefer. 

B. Bolh pacts ttip and will not reset. 

c. No iDdlcation in tbe coclcpit. 

D. EICAS mahlfenanre message "PACK CONTR.OU.ER BITE." 

Ffnfsb Time: ---

20 
Results of tlu BnviroR~~~enllll Control System TutlJr Experiment 

D. Malfunctions 

1bis is the most tmportant section of the evaluation, since it measures what the ECS Thtor was 

designed to teach to its users. Include a short expicwation for your answers. 

Start Time: __ _ 

13. The left pack fails. In the cockpit the left PACK OFF light on the RESET switch is illuminated 

and will not reset when the pack selector switch is in any position. There is also an EICAS message L 

PACK OFF. Wnat wouid you suspect the problem to be? 

14. The pilot tells you the INOP light on the pack reset switch for the right pack illuminated and will 

not extinguish. You go up to tbe cockpit and move the selector switch to the STBY positions and tty 

to reset the switch. The INOP light stays illnminatoo There is also an EICAS message L PACK 

TEMP. You go down to the pack bay and physically check the heat exchangers. Heat exchangers 

check OK. You also do a B11E check on the Pack Temperature Controller; the BTIE test is OK. You 

check the Row Control Valve. It checks out OK. You do a BTIE check on the Standby pack 

controller; checks OK. Using the FIM manual, what is the problem? 

15. When performing a BTIE test on the standby pack controller, you get a NO GO light in position 3. 

What component is faulted? 

16. When performing a pack temperature controller BITE, what position should the pack selector 

switch on the overllead be set to? 

17. A B-767 is illcoming with a pack malfunction. The indications were not radioed in. Once the plane 

lands, in what or<a wouid you check these items? 

_ inspect heat exchangers. 

_ operate pack temperature controller BITE. 

_ check condition of the PACK OFFIINOP lights. 

_ try to operate the pack in different modes. 

21 
CluJptq Two 

18. A B-767 has a problem with the ECS system. On the ground with the packs operating, the left 

pack trips off. You have an "INOP" light and "PACK OFF" light illuminated. You allow the pack to 

cool and reset the switch, the lights extinguish. After a while the pack trips again in AUTO and 

STBY. You go down to the left pack bay and notice water dripping from a drain tube on the water 

extractor. This would indiate: 

A nonnal condition. 

B. coalescent bags need to be replaced. 

C. water nozzles in the ram air duct are clogged 

D. leak in the potable water system. 

Finish Time: __ _ 

You have completed the evaluation; please 6D out the following evaluation. 

22 
Resulls of the Erwironmentlll Control System Tutor Experiment 

Evaluation for ECS Tutor 

1bis is an evaluation to determine how effective you think the ECS Tutor is. Please choose a number 

between 1 and 5 that describes your agreement with each statement, using the definition in the scale 

below. Be sure to read the statements carefully. Write your choice to the left of the question. 

NOTE: This is not a test! This study is confidential and will not be used to evaluate you. You should 

not sign your name to this evaluation. 1be evaluation is designed to determine which parts of the ECS 

Thtor need improvement 

1 -------1----3 ---- 4---5 

strongly agree neutral disagree strongly 

~ree ~ 

General System Questions 

_ 1. The system commands are easy to use. 

_ 2. I feel competent with and knowledgeab!e about the system commands. 

_ 3. When I get an error message, I find that is n01. help.ful in identifying the source of the problem. 

_ 4. There are too many options and special cases. 

_ 5. 1be tutor behaved in ways that I didn't expect. 

_ 6. I have trouble remembering !l!P. commands and options and must ask questions frequently. 

_ 7. The system was not intimidatin~. I felt comfortable ·asing it 

_ 8. I often knew what to do, b'Jt I didn't know bow to do it 

Questions about Specific Components of the ECS Tutor 

_ 9. The "hints" that suggested possible parts to test or replace were useful. 

_ 10. The help buttons provided useful information in solving the problems. 

_ 11. The lesson introductions and reviews helped me to understand how the malfunctions were 

related. 

_ 12. I did aot know what to do after replacing a component 

_ 13. The "Info" bar at the bottom of screen helped me understand the system. 

_ 14. The FIM tree was easy to use and helped in solving problem. 

_ 15. i could not tell what the pictures of ECS parts were supposed to be. 

_ 16. The touchsaeen was easy to use. 

_ 17. The computer was slow in responding to my choices. 

If you have any other comments about the ECS Tutor or about your answers to these questions, 

please write them on the back of this paper. Thank You. 

23 
l"en Computers: Evobmtiou, RecontnU!ndations, and tJu PENS Project 

Chapter Three 

PEN COMPUTERS: EVALUATIONS, RECOMMENDATIONS, 

AND THE PENS PROJECT 

3.0 INTRODUCTION 

Pen computer technology has the potential to revolutionize the computer industry. Pen computers are 

compact, easy to use, and designed for field use. These factors make pen computers ideal tools for field 

data collection and analysis, even for individuals who do not currently use computers. Galaxy Scientific 

is working with the Flight Standards Service and the Office of A vialion Medicine to develop a job aiding 

system that is based on this exciting new technology. 

1be following is a discu:lSion of the general cllaracterlstics of pen computers, a comparison of pen 

computers available from a variety of manufactllrers. and a description of the progress of the Performance 

ENban(" Jlllent System (PENS) for A vialion Safety Inspectors. 

3.1 GENERAL CHARACTERISTICS OF PEN COMPUTERS 

Pen computers are similar to personal computers in that they consist of a display, a central processing unit 

(CPU), and an input 

device. Unlike personal 

computers, however, 

pen computers put the 

CPU and display in one 

small box. Instead of a 

keyboard and mouse, a 

pen comP'.!ter uses a 

special pen stylus for 

input The pen stylus 

not only functions as a 

pointing device, it also 

serves as the primary 

means for entering data. 

Fi~e 3.1 illustrates 

both a typical personal computer and a typical pen computer. 

Unlike a personal computer, data are written on the screen, rather than typed; a handwriting recognizer 

translates the printed input into "typed" characters. (Script or "cursive" recognition software is currently 

being developed by several companies.) Additional gestures are used for editiqg. Each person customizes 

the recognizer to her/his handwriting style for improved recognition accoracy. Pen computers also come 

with "virtual" keyboards (software versions of keyboards), with a connection for an actual keyboard, or 

with an actual keyboard located benea1b the pop-up display. 

Pen computers, like norellook computers or laptops, are battery powered. Extending the charge life of 

batteries is one of the hottest areas of portable computer research. Battery lite currently ranges from one 

25 
hour (with no ellel"gy conserving featureS turned on) to three or more bours (with all energy conserving 

features in use) on a single charge. While manufacturers take diverse approacbes to battezy charging and 

power management, nearly all pen computers come with user-replaceable batteries and ac adapters; several 

manufacturers also offer automobile cigarette lighter adapters. 

Personal Compoter Memory Card Intematlonal Association (PCMCIA) slols also differentiate pen 

computers. Whereas notebook and laptop comp~ters have seen limited use of these slots (and they're 

practically nonexistent on desktop computen), nearly every pen computer has at least one PCMCIA slot. 

These slols can be used for fax/modem cards, network cards, removable storage devices, and memory 

extension cards. The cards are approximately the size of a credit card and will likely see widesprelld use 

in the near future. Such devices allow quick and easy addition of peripherals or personal data. The 

PCMCIA slols make it easy to have a pool of computenl for field workers. When someone needs to go 

to the field, sheJhe can grab a computer and a few PCMCIA cards and quickly have a customized 

machine. 

Fmally, pen computers are generally lightweight. Units range in weight from approximately three and a 

half pounds to around seven and a half pounds. This broati range is due to the unique featureS of each 

computer. For instance, the lightest computer uses a low voltage power system 1hat reduces battely size 

(bence weight) and constrains the sizes (weighls) of intemal components. Two of the computers in the 

middle weight range come with built-in keyboards that can be stored beneath the displays. At the high 

end of the weight range are the ruggedized unils; these uni1s can withstand environmental extremes, such 

as cold temperatures and rain, and the general hazards of portable use, such as drops or collisions. The 

individualizing features of pen computers are discussed later in this document. 

3.2 KEY BENEFIT OF PEN COMPUTERS 

Pen computer technology capitalizes on the evolution of several brancbes of computer science and 

engineering. Graphical operating environments, such as Windows, allow the user to operate a computer 

almost entirely through pointing and "clicking" (tapping twice in rapid succession with the pointing 

device). The pen stylus not only supports such pointing and clicking, but when it is combined with 

handwriting recognition, it allows the user to enter data or issue commands. "Thus, one simple device can 

be used as the sole means of comp~ter operation and data collection. The result of such technological 

advances is 1hat pen computers offer the promise of empowering field workers with computer technology. 

Even those people who don't traditionally use computers can be brought up to speed with relative ease. 

3.3 POTENTIAL USES OF PEN COMPUTERS 

Because pen computers are designed· for field use, they have a variety of applications. Some of these 

application areas include sales, production, health care, census, law enforcement, delivery services, 

investigation, and inspection. 

For example, sales people can make sales calis, assess the customer's needs, quote a price, and even sign 

up the customer, all on the computer. Production personnel can document production difficulties and track 

work in progress as they walk through the plant. Health care applications include patient forms, 

pharmaceutical orders, meal planning, and patient tracldng and charting. Instead of using paper forms and 

26 
Pen Computers: EVGI:uotions, ReconunendDtions, and the PENS Project 

waiting months for the data to be entered into a computer database. a census could be taken wilh on-line 

forms, lhus facilitating quick compilation of a database. 

Law enforcement personnel could use pen computers in a variety of ways, from mundane tasks such as 

writing tickets, to more involved tasks such as documenting and investigating crimes. Personnel in the 

National Transportation Safety Board could use 1hem for aircraft accident investigations. Delivery services 

currently use custom pen computers for package tracking, delivery schedules, and recipient signatures. 

Any regulatory agency could use pen computers for inspections. For example, Food and Drug 

Administration personnel could use them wben inspecting food production and sales facilities (e.g., meat 

packing plants, restaurants, grocery stores, etc.). Occupational Safety and Heallh Administration officials 

could use pen computers for inspections of workplace environments. Aviation Safety Inspectors could 

use pen computers to speed data collection, information retrieval, information distribution, and 

certification. 

3.4 COMPARISON OF PEN COMPUTERS 

Eight pen computer models from a variety of manuf::..;:turers were obtained, evaluated, and ccmpared on 

the basis of CPU type and speed, hard disk capacity, display type, weight, ruggedness, cost, and a number 

of olher factors. (Specific computers are hereafter identified as Computer fl through Computer #8.) The 

following specifications, figures, and tables describe the results of that evaluation. While none of the pen 

computers evaluated could be considered "perfect," some were clearly better 1han olhers. While pen 

computers come in a variety of models and config>,Jiations, these units were selected because they are all 

capable of running Windows for Pen Computing. The models evaluated represent the bulk of the currently 

available pen computers that will run lhat operating environment. (Computers that use the NEC V.'lJJ 

CPU are incapable of supporting Windows; lherefore, computers that use 1his type of CPU were not 

evaluated.) Perllnent specifications of the evaluated units can be found in Appendix A. 

(Two of the units, Computers #4 and #5, were not available in time for a "hands-on" evaluation. The 

specifications reported here were obtained from printed materials from the manufacturer and from 

published reports.) 

3.4.1 Evaluated Characteristics 

Central Processing Unit Central Processing Unit (CPU) type and speed are central to the response time 

of a computer. An 80386 CPU should be considered the absolute minimum for portable use, particularly 

if running Windows. Indeed, one would be hard pressed to find a currently manufactured portable 

computer lhat uses an older generation processor. Whereas an 80386 is a minimum, it is difficult to 

conceive of a unit lhat is too powerful; many portable computer manufacturers are unveiling 80486-based 

models. In lhe future we may expect more powerful CPUs, such as an 80586. 

The clock speed of the CPU affects response lime nearly as much as the type of CPU. A 20 megahertz 

clock rate is an effective minimum for portable use, particularly when using the handwriting recognition 

software that comes wilh Windows for Pen Computing. While desktop computers now have clock rates 

of 33, 50, or 66 megahertz, pen computers typically have a 25 megahertz upper limit However, the 

higher the clock rate, the better the response lime. 

27 
Most of pen computers use an 

80386 CPU with a 25 megabeltz 

clock rate. However, Computers 

#2 and #3 have a 20 megabeltz 

clock rate (and both are produced 

by tbe same manufacturer). 

Computl% #4 uses an 80486 CPU 

with a 20 megahertz clock ~; 

given the increased power of tbe 

80486 CPU, this unit is faster 

than the units that bad 25 

megahertz '386 CPUs. Another 

model :li:om the same company, 

Computl% #5, has an 804R6 CPU 

with a 25 megai1er1z clock rate. 

c 

p 

u 

I 

I 

• • 

:-

~-

-

(A 80486/33 megahertz model is Figure 3.2 

to be released lata" this year.) 

One manufacturer chose to use a 

-

-

Comparison of CPU Type and Spefd 

-

• 

special low voltage 80386 CPU in its computa, Computer #7, because it allows for a smaller battery, tlms 

reducing weight Figure 3.2 compares the CPU characteristics of eacb unit 

Hard Disk Caoacicy. The baa! 

disk capacity varied greatly across 

pen computer products. 

Capacities ranged from 40 

megabytes (Computers #2 and #7) 

to 190 megabytes (Computl% #8). 

Although there can be 

diminishing returns for large hard 

disks (in terms of capacity versus 

cost), software is becoming more 

space-intensive, particularly with 

regard to Wmdows programs. 

For example, the Wmdows 

operating software can use over 

seven megabytes of disk space, 

and a typical word processing 

application can use ove~: 10 

H 

• r 

• 

D 

I 

I 

• 

c 

• • • • I 

' 

(1011 ' 

megabytes of space. 1berefore, Figure 3.3 

40 megabytes is an effective 

lower limit on capacity, while 190 

._ -r..-·-·- ........... ....... -...--. .. ----- Comparison of Hard Disk Capacities 

megabytes CllllllOt be considered excessive. Currently Computer #7 is limited to a 40 megabyte hard drive 

because that is the only available size that runs on the low voltage system chosen by the lllllllUfacturer. 

Figure 3.3 represents the distribution of disk capacities for the evaluation units. 

28 
Pen Computers: Evaluatil'<IS, ReeommeiUiJlJioJJS, fliUl tlui PENS Project 

Display Type. Display type 

greatly affects the ability to read 

the display in a variety of lighting 

conditions. Transflective displays 

work beSt in bright light. and they 

work fine in typical indoor 

lighting. However, transflective 

displays are nearly impossible to 

read in the dark. Backlit displays 

work beSt in the dark, and they 

work fine, in typical indoor 

lighting. However, backlit 

displays can be difficult to read in 

bright light (1his problem is 

greatly ameliorated by separate 

- D 

I 

·-

OTI 

• • 

• 

T -• • 

-

r--- - -

- r- r- f--

-

_____ .,__ __ 

A a D .. • .. 111 • 

..,.. ......................................... -- -- briglltness and contrast controls). Figure 3.4 Companson of Display Types 

(It is extremely difficult to 

. . 

describe exactly what transflective 

and backlit displays are or how they look. One really needs to see these displays to understand more 1ban 

the factS 1hat one works best in the light and the other works best in the dark.) ComputerS #7 and IS are 

unique in 1hat they have backlit displays 1hat can be completely turned off, in which case the displ:ly 

becomes transflective. Computer #S is the only unit available with a color display. Figure 3.4 depicts 

the display cypes of the compared units. 

8 

7 

Weight Weight is a critical 

factor when evaluating computers 

for field use. 1be computer must 

be easy to hold and carry for a 

significant portion of the 

workday. 1be weight of pen 

computers is highly correlated 

with ruggedness; the more rugged 

a 'dliChlne, the heavier it is likely 

w 8 ~ • 5 

• ' 4 

• t 3 

I 

to be. Computer #7 was the 

lightest evaluated unit at 3.3 Ibs. 

Computer #8, which is 0----- _l 

-- ruggedized, was the heaviest unit 

at 7.5 lbs. (1be unit ev11l:lated 

was a pre-production unit; Figure 3.5 

production units are supposed to 

.. .. • • • • • .,... ........ __ . ·---.....,.~----­ ----· 

Comparison of Weigbl:s 

weigh 6.5lbs.-wbich would still make it the heaviest pen computer.) Computer #1, because of its built-in 

keyboard. is toward the upper end of the weight range. Computer #5, which also has a built-in keyboard, 

weighs 7.0 Jbs., which is also at the upper end of the weight range. However, the pen tablet can be 

removed ftom the keyboard base unit to lighten the load. Figure 3.5 shows the weights of the evaluated 

units. 

29 
B!!fterv Life. ADotber fac:toc tbar affects the lllillty of a portable compura-is battery Hfe; tllltt is, mw long 

em the computer be operated before it is necessary to challge tbe battery or recbarge it. Battery life can 

be extl;llded by incorporating vadous energy-saving fea&ures into tbe compute£. One of tbe most common 

energy-saving teawres is to shut otr compouems that are idle. For example. if the bard disk has not been 

used for a period of time. say 30 seconds, it can be shut down to conserve power. Similarly, tbe screen 

and the CPU can be turned oft wben not in use. 1be amount of time that passes before a component is 

sbut down is usually adjustable by 1be operator. While pen computer manufacturers tend to specifY long 

battery lives based on all energy-saving features enabled, real use tests indicate 1bat a standard pen 

computer battery will last about an bour of continuous use when none of the energy-saving features are 

enabled. (Ibis assumes tbe display is backlit; a display that is not backlit consumes considerably less 

power. For example, Computer #l will run approximately two hours on a single cbarge.) Computer #8 

is an exception to this rule in 1hat 

it will run approximately two 

hours on a single charge with 1be 

display on. 1be pen computer 

manufacturers are combating the 

problems associated with short 

battery life in several ways: 1be 

manufacturer of Computer #7 

supplies two batteries as standard 

equipment with their p00uct; 

Computer #8 uses a quick-charge 

battery 1bat recharges in an hour; 

tbe manufacturers of Computers 

#7 and #8 both use nonreplaceable backup batteries 1hat 

allow tbe operaror-to~ main 

batteries without shutting down 

• • • t 

• 

r 

' 

l 

I 

' • 

IN 

9 

• 

1be unit; Computer ffl has an Figure 3-6 

optional beavy duty battery tbat 

gives two bours of continuous 

CJ ....... .._.. ... ,-....-.. ·-...... ...,... ...,_..,...... mmJ 4- ·-· ,,..__ ........ --~ .... -.-------....... ....-...------ ---Comparison of Battery Life 

use. All of tbe mamd'acwers have designed their units such that a dead battery can be quickly replaced 

with a fully charged one. Figure 3.6 compares the battery lives of the evaluated units, with and without 

energy conserving fea&ures turned on. 1be manufacturer's specifications sbould be taken with a grain of 

salt. 

Ruggedness. Ruggedness, or the immunity fiom damage due to drops, collisions, water, extreme 

temperatures, etc., can be an important aitclion on which to evaluate pen computers. Most field 

enviromnents are rather barsb compared to tbe typical office environment. Instead of sitting quietly on 

a piece of furniture, as would a desktop computer, a field computer wiJl (at a minimum) be subjected to 

a lot of handling. 1n tbe course of such handling, it is likely that: tbe computer will be dropped; tbe 

operator will bump into things while operating tile computer; it will rain or snow on the computer; or, the 

computer will be left on tbe dasll of a locked car on an August afternoon. All of these things can take 

a toll on 1be hardware if it is not designed with such factors in mind. While Computer #8 is specifically 

designed to handle such environments, most of the other evaluated units were designed to be semi-rugged. 

Instead of making ruggedness a fixed aspect of tbeir units (tbus making tllem heavy all of the time), the 

30 

.· ~ 

I 
Pen Computers: EVIIhudions, Reco11111U1111lltidns, tuUl the PENS Projed 

manufacturers of these units have opled for ruggedized carrying cases. 1bese cases improve impact and 

water resistance, and tbey have strapS and handles to ease carrying the computer. Table 3.1 SU1lliiWizes 

the ruggedness characteristics of the evaluated units, along with a number of other factors. 

Other Factors. Other factors 1llat contribute to the desirability of a given pen computer over another 

include such things as a built-in keyboard, separate brightness and contrast controls, a standard internal 

or external floppy disk drive, tlle number ofPCMCIA slots, a built-in fax/modem, and the size of the unit 

There are tradeoffs involved witb many of these factors. For example, a computer 1llat bas one PCMCIA 

slot and an internal fax/modem is nearly equivalent to a computer 1llat bas two PCMCIA slots but no 

internal fiDVmodem. (One of the PCMCIA slots can be used for a fiDV!DOdem. A fiDVmodem can be very 

important to remote field workers who need to communicate with otbers in other field locations or at a 

central office.) Table 3.1 lists the factors and their presence on the units. 

Price. For many people, the determiuing factor on purchasing a pen computer will be price. It is 

important to realize 1llat although tlle initial cost of a pen computer is likely to be bigber than an 

equivalently equipped notebook computer, pen computers also wcigh less and are smaller. Furthernlore, 

pen computers were designed to speed data collection and reduce reliance on data-entry personnel. In 

Other words, many agencies who use paper forms rely on data entry clerks to read tlle data off those forms 

and transcribe them into a computer database. Data entry clerks are an intermediate step in the data 

collection and distribution process; such intermediate steps can reduce data integrity and slow assimilation 

of the data into databases. Pen computers allow data to be directly entered in the proper database format 

at the time of collection. This method ensures that data are entered correctly and it reduces reliance on 

data entry personnel. Wblle price is bighly conelated with capabilities, it is not a reliable indicator. Price 

should be one factor used to choose between pen computer models, but it should not be the sole fa-:tor. 

The prices of the pen computers evaluated are shown in Figure 3.7 

3.4.2 Common Features of Pen Computers 

All of the evaluated pen computers bad an external keyboard port (with the exceptions of Computer #1 

and Computer #5, which bad built-in keyboards). The units also had serial and parallel ports; on 

computers other than Computers ~. #3 and #8, the parallel port doubled as a floppy disk drive connector. 

Serial ports are often used for communications (including loading software onto the pen computer) and 

a mouse (wbich, of course, is unnecessary wben using a pen stylus as a pointing <levice). Parallel ports 

are also used for communications, but their primary use is for connecting printers. Computer #7 was the 

only model that did not have a VGA port; a VGA port is a convenient feature if the operator wants to 

display items on a large monitor instead of the pen display. All of the units were configured with cigbt 

megabytes of RAM; this is an effective minimum for running Windows for Pen Computing. 

31 
Table 3.1 Miscellaneous Pen Computet Characteristics 

Ctmp•ter Ctmp•ter Ctmp•ter 

. - fl fZ t3 

R•ued Optional Opdllllll OpllOIIII 

Case CUe CIW 

B111lt-ia Yes No No 

kerlleard 

·N•mber ef 2 1 1 

Brl<•••• 

••• Ceatrast 

Ctatroll 

~ Esteraal Yes No No 

Ooppf dhk 

drive 

atudar.d 

N•mberof I I 1 

PCMCIA 

slots 

D•llt-ia Yes No No 

fas/modem 

J)lmeasloas 1.6"H x 1.2"Hx 1.2"Hx 

li.S"W s lt.7"W X 11.7"Wx 

9.3"D 9.4"D 9.4"D 

$lntem&l 

Camp•ter Comp11ter Ctmputer 

t4 NS *' OptiOaal Optional 

Cue Case 

No Yes No 

2 2 2 

Yes Yes• No 

2 2 I 

No No No 

1.2"Hs 2.1"H X 1.3"Hx 

10.9"Wx 11.7"W X li"Wx 

9.8"D 9.3"0 11"0 

Comp•ter 

117 

Optloaal 

Clle 

No 

2 

Yea 

2 

No 

l.S"H X 

10.6"Wx 

8.3"0 

Comp•ter 

,. . 

Yea 

No 

2 

No 

0 

I 

' 

Yes 

' 2.0"H X 

12.S"W x I 

10.1"0 

i 

r 
3.4.3 Common Umltatious of 

Curreut Pea Computers ,. 

r 

I 

c 

As mentioned above, a cune11t • 

common limitation to pen rr 

computers is tbe sbort battery life. : 

Batteries also make significant : 

• • 

-

• f 

collttibutions to tbe weight of a 

unit. Several manufacturers are 

working to improve battery life, 

while maintaining lightweight ; 1-i;~;.i;~l;tc~~~~~TBD~:ti;~~~i!;+~~ batteries. Many curreDt pen ., 

computers use niclrel-cadmium 

(Nicad) batteries, which appear to 

have an upper limit on battery life 

of one hour (given a backlit 

c::::J -- .,.. 

--.............. ...,...,. ... ....._. _____ _ ,.. ... .......... 

display and current technology). 

Nickel-metal hydride batteries are Figure 3•

7 

now beginning to appeat, tbese 

Comparison of Prices 

batteries appear to have longer lives tllan do NiCad batteries. It is only a matter of time before compact. 

lightweight, long-life batterles are available. 

On the subject of batterles, a limitation of an current pen computers. except ComputerS #2 and #3, is that 

tbe pen stylus requires batteries. Unless tbere is an accompanying keyboard, there is no way to operate 

tbe compnter if tbe pen stylus batteries die. The pen stylus batteries are typically readily available (and 

irexp:nsive) calculator or mmng aid batteries. It is probably a good idea to cmy a spare set of pen 

stylus batteries in tbe field The pen styli for Computers #2 and #3 use internal inductors that are sensed 

by tbe radio 1i:equenCy gdd on tbe computer. Otber manufacturers are probably moving in tbe inductor 

cfirection. 

The biggest limitation of pen computers is tbe handwrltiDg recognition software. Recognition accuracy 

is unacceptably low wben using tbe recognizer that comes with Windows for Pen Computing. The 

standard recognizers that run under~ operating environments, such as PenPoint and PenRigbt, do not 

perform any better. However, dlere is a third-party recognizer, Nestor Writer, that llllS very high 

recognition accuracy. According to a receut publication {Bachus & Weston. 1993), a novice user can get 

initial accuracy rates above 80'1>. The authors reported rates above 90% after one hour of training. 'Ibis 

software is currently avaDable for PenPoint and should be available for Windows within six months. 

While an cummtly available recognizers require printed text input, several companies are working on 

cursive recognizers. 

3.4.4 Tradeoffs Between Pea Computers 

It should be apparent that tbe pezfect pen computer has not yet been invented. As mentioned above, there 

are several tradeoffs between tbe features of pen computer models and each model has features that make 

it unique. Computer #1 is modestly priced and has a built-in keyboard, but tbe keyboard makes 1he unit 

heavy. Computers #2 and #3 have tbe benefit of not requiring batteries for the pens, but they are more 

33 
expensive than similarly configured units. Computer tl4 bas an 80486 processor and is lightweight. 

Computer #5 also bas an 80486 processor, a color display, and a ouilt-in keyboard However, tbese units 

are rather expensive. Computer f6 bas a handle that doubles as a stand and it bas a "hot dock." The bot 

dock aiiows the unit to be quickly placed !n a docking station that supplies power and colllleCtS the UDit 

to a network. Computer #6 fails in the middle of the group in terms of overaii performance. Computer 

#7 bas two PCMCIA slots, is the lightest unit evaluated. and bas a baclditllransflective display. 

Unfortunately, it bas a smaii bard disk and the evaluated pre-production units bad very short life main and 

pen batteries. Computer #8 is very rugged and bas quick-cbarge batteries, but it is heavy and expensive. 

Such tradeoffs make it difficult, if not impossible, to dictate which unit to purchase for a given applicatioa 

When implementing any application, the designer must perform an extensive field evaluation to fully 

understand which features are most important to the people wbo will actually be using the equipment. 

Just such an evaluation is proposed in the next section. 

3.5 PENS: A PERFORMANCE ~CEMENT .§.YSTEM 

The Performance ENhancement System, PENS, is a tool to aid Aviation Safety Inspectors in performing 

their tasks. Aviation Safety Inspectors (ASis) make up the inspection team for the FAA. A viatio'l Safety 

Inspectors perform a variety of tasks, in both commercial and general aviation areas, including: jnspecting 

aircraft and equipment, reviewing manuals and records, certificating pilots, and evaluating training 

programs. 

There are 2600 ASis in the nine regions of the FAA. The initial target of PENS is an ASI performing 

an airworthiness (safety) ramp inspection. (A ramp inspection consists of inspecting an aircraft. while it 

is at the gate, before a scheduled departure.) PENS is an electronic performance support system (Gery, 

1991) that consists of two components: a "smart" forms application and an on-line documentation system. 

PENS capitalizes on the recent advances in pen computer technology outlined above. 

3.5.1 Improved Fonns 

As is typical with regulatory agencies, there are several forms that must be completed while performing 

an ASI task. Currently, these forms are on paper and require that rednndant information be recorded on 

each form. After completing the forms, the ASI either types the data into a local computer database or 

helsbe submits the forms to a data entry clerk. 1bere are several drawbacks to such an approach. First, 

redundant recording of data on multiple forms takes time that could be devoted to more productive 

activities. Second, the two-step process of recording data on paper and then entering the data into a 

computer is inefficient. Third. one is either paying an inspector to do a task for which helsbe is overqualified, or one is paying for a staff of data entry clerks. Fourth, a data-entry clerk may make 

transcription errors (due to misreading the inspector's handwriting) or errors due to incomplete knowledge 

and underslanding of the inspector's activities. Such errors mean that the database is an unreliable source 

of information. Finally, Ute currem process takes considaable time, which means tbece is a delay in 

gelling safety data into the national database where it can be accessed by otbec members vi the FAA. 

Pen computer technology can be easily applied to such tasks to minimlre the number of steps required 

to collect data and assimilate it into the database. Forms will be linked together so that an entry in one 

form propagates to the other forms, thus eliminating re<!undant data entries. Furthermore, the data will 

34 
be collected so that they are ready for direct downloading into the database. This method of collecting 

data reduces the need for data emry clerks and it reduces data traliSCiiplion errors. At the end of the work 

day, the Inspector will return to the omce, colllleCt the pen computer to the network, and initiate a 

downloading procedure that will be carried out ovemigbL 

3.5.2 On-Hne Documeatadon 

The second major coDIIibution of PENS is an on-line documentation system. Whereas ASis currently 

must carry two briefcases full of books (including Federal Aviation Regulations, ASI Handbooks, and 

other regulatory documents), the necessary data will be stored on the hard disk of the pen computer or 

on a CD-ROM (compact disc, read-only memory). Not only is the computer media more lightweight and 

compact, it also facilitates quick retrieval of specific information. For instance, an ASI will be able to 

search the regulations for the word "corrosion" to answer a question on reporting defects. PENS would 

then indicate all of the instances of the word corrosion. The ASI could !hen ask PENS to retrieve the 

relevant documents and display the pages that discuss !he term. 

Besides the bulk and inefflciency of the books, inspectors must deal with problems of information 

currency. One complaint made by inspectors is that they will tell an operator that it is not in compliance 

with the regulations, only to be shown a more recent edition of those regulations. That is, sometimes the 

operators get the most recent editions of the regulations before the inspectors do. This problem could be 

dealt with by distributing updated documents to the pen computers when they are connPrlPA'! to the 

database computer network. Thus, a new edition of a document could literally be published one da.y and 

in the i.nspector' s hands the next. 

3.5.3 Additiooal Benellts 

A side benefit of using a computer to support inspection activities is that it opens the door to other types 

of activities lUld methods for docu::nenting an inspection. For example, an inspect:>r could follow an online checklist for an Inspection. The cbecklist would then become the focus of interactio~t with the 

computer; by completing the cbecklist. all of the necessary forms would be automatically completed. We 

could even develop a schedi!}Ing compooont that would remind the inspector to follow up on an 

inspection. Wben documenting an inspection, ASis currently must record their findings verbally. 

However, because the bulk of a ramp inspection is conducted by visually inspecting an aircraft, sketching 

is a more natural method for reconling the results of such an inspectiQO. Thus, if an icspector found a 

leaking seal on the wing of an aircn!ft, the inspector could annotate a line art drawing of that aircraft on 

the computer. This graphic could then be stored along with the completed form. 

Another important benefit of giving AS Is computer -based inspection tools is that it would greatly ease 

inspection of air carrier records. Nearly all air carriers keep their records in computer files, as well as 

paper files. (At least one airline bas only computer records.) Whereas searching paper files for specific 

data can be tedious and cumbersome, computer databases were designed for just such activity. Indeed, 

some industry offlciliiJ are promoting lbe notion of allowing the FAA to inspect their records: 

35 
•• > _.<· 

''We're not taking adVlllltllge of the data sysleiiiS airlines have in place." [a] senior vice 

president of tecbnical operations at [an airline], said. Those systems could be the 

foundation of a oew surveillance system "tbat penalizes bad behavior and rewards good 

behavior." (McKenna, 1992) 

The proposed concept would consist of reducing the frequency of inspections for operators who 

consistently meet airwortbilless standards, while inaeasing the ftequency of inspections for those operators 

who do not meet those standards. (A similar concept is already applied to other typeS of activities.) This 

approach should bellefit the airlines by streamHning maintenance (thus reducing costs due to out of service 

aircraft) and reducing the amount of company time speDt on inspections. 

3.6 EVALUATION AND IMPLEMENTATION 

1bere are a number of issues that can affea 1he success of introducing new technology into the ASI work 

environment. Many inspecto!: ::0 not have experience using computelS. Of those inspectors, some are 

willing to try the new tools based on promised increased productivity, while others &-e hesiu.nt to embrace 

a new method for performing their work. Some inspectors are even concerned with how they will be 

perceived by the operatorS wben they are carrying a pen computer. 

Pedlaps the most significant hurdle to widespread implementation of PENS, however, Is the adequacy of 

the handwriting recognition software. 1be difficulties involved with handwriting recognition (writer 

independence, print vs. cursive writing, inttaindividual variations in writing style) are directly aoalogous 

to difficulties with speech recognition; however, handwriting recognition Is five to ten years behind speech 

recognition. Although much research and development Is going in to oew methods for handwriting 

recognition, we cannot wait for such advancements before fielding a system. Therefore, we are 

capitalizing on coostraints built into the forms and data to reduce dependence on handwriting recognition. 

For instance, ;.ec;mse many fields ontbe forms IeqUire one item out of a finite set of possible entries, one 

can display that set and select an item from it. This approach bas 1he added benefits of reducing memory 

demands on the inspectorS and of inaeasing data reliability. 

Pen computer configurations and durabillties must also be considered. as there are significant tradeoffs 

in these areas. Questions that should be asked include: Is it better to have a lightweight unit without a 

keyboard. or a slightly heavier unit with a keyboard? Which Is more important to inspectors, weight or 

ruggedness? Is battery life sufli.cien• to even consider using such a device? Appendix B lists these 

questions and others, along with our recommr,ndations. 1bese recommendations are based on very 

informal evaluations, however, and should be considere& only a.~ preliminary guidelines. 

3.6.1 Evaluation Plan 

Given the above concerns, the following evaluation Is proposec:l as a means to assess the utilities of various 

hardware configurations and the effectiveness of the software. We expect to modify the software based 

on inspector feedback, but the field evaluations will largely determine which models of pen computer 

hardware will be put into actllal use. Although we expect the hardware to withstand most environmental 

conditions, it Is possible that some extreme conditions will preclude the use of computer hardware. The 

following expenlliC!Ital plan will provide inspectors with experience with a range of models and it will 

subject the hardware to a range of operating environments. 

36 
P•n Co111pl11Ns: Evo''UitiofiS, R4co,.rultrtions, arul 1M PENS Project 

3.6.2 FAA Regions 

We will field units In six to lliDe RegioDS, In a variety of locations. This will give the project broad 

exposure to field Inspectors end it will subject the banlware to a range of environmental conditions. The 

six Regions identifiOO below are suggested based on the worst-case environmental conditions present In 

those regions. 

Suggested location: 

Alaska 

Northwest Mountain 

Central 

New EnglaDd/Eastem/Great Lakes 

Sou1hwest 

Southern/Western Pacific 

3.6.3 Pen Computer Models 

Reasons: 

Cold, snow 

High humidity, low temp., rain 

Average temp., average humidity 

Cold, snow 

Low humidity, heat 

High humidity, rain, heat 

We will field four different models, each from a different manufacturer; this will reduce reliance on one 

manufacturer and it will help Identify design factors important to 1he inspector population. From this 

evaluation, it is likely 1hat two of the models (or subsequent versions of them) would be chosen for final 

implementation. However, all of tllf: purchased units would remain In service after the evaluation. 

Each unit would have nearly Identical hardware configurations, so as not to bias the results. 

Seventy-two computers (and peripberals) will be purchased; 1his will provide each Region wi1h two units 

from each ID2llUfacturer. 

Suggested Computer; 

Computer#l 

Computer#4 

Computer #17 

Computer#8 

Reasons: 

Built-In keyboard 

80486, medium weight 

tightest 

Rugged 

(Note: Computer #S is also an 80486 unit wi1h a built-in keyboard; this may be used instead of Computer 

#4.) 

3.6.4 Experimental Design 

A team of eight inspectors in each Region will evaluate these units. These inspectors will represent a 

cross-section of the inspector population In terms of age, sex, work experience, and computer experience. 

Each inspector will use one of the computers for a week and then switch to a different model. The 

rotation would be cnonterbalanced to eliminate order effects. This rotation will continue until each 

inspector has had an opportunity to use each model. At the end of the rotation, each inspector will 

complete an evaluation form (sample attached) 1hat requests him/her to rate each unit and answer some 

general questions. The Inspectors should still have access to the units at this time to refresh 1heir 

37 
memories of the specifics of each UDit. From tbese data, we will recommmd two of the models (or 1beir 

subsequent versions) for final implemeutation. 

3.7 SUMMARY AND CONCLUSIONS 

As discussed above, pen computers use bandwritiug recognllion software and a pen stylus for bJput, ramer 

tban a keyboard. The operator writes on the screen and the bandVAitiJJg recognition software translates 

the written cllaracters to typed cbaracters. The pen stylus aiSl' liC1S 211 a poi!IUng device, mncb like a 

mouse. When combined with graphical user interf'al:e:;, s:!~.h a.s Windows for Pen Computing or PeDPoint, 

the pen stylus and handwritiug recognition software hold the promise of making computers easier to use 

tban traditional desktop computers. Many pen computer models from a variety of manufacturei:S have 

undergone preUminary in-house evaluations. These evaluations bave identified severn! differences in the 

design of such devices and bave identified some ttadeoffs involved in these design choices. While such 

evaluations are valuable, they should be seen as only a fiiSt step in selecting equipment; final selections 

must be made based on field evaluations by dle actual user population. 

As with the introduction of any new tool into an existing system, the effects are widespread (Cbapulis, 

1982; Helmreich, 1987; and, London, 1976). The potential for enhancing the productivity lllld job 

satisfaction of Aviation Safety 1nspectors is great. However, with that potential comes the possibility of 

either having no effect (because of rejection of the tool) or, WOISe yet, actually decreasing performance. 

The PENS project is taking a cautious, iterative approach to design and introduction of the tools. Only 

tbrough careful cognitive task analysis, rapid design and prototyping, and empirical evaluation will PENS 

be seen in the eyes of the inspectors as a belleficial cognitive tool, rather than another doorstop or 

paperweight. 

3.8 REFERENCES 

Bachus, K. & Weston, R. (1993, January). Pen power. CfnpoTlll$ Cont.plllillg, 68-95. 

Chapanis, A (1982). Computers and tbe common man. Jn R. A JCasschau, R. I actunan, & K. R. 

Laughery (Eds.), lnfo17111JlWn teChnology and psychology: Prospects for the futUre (pp. 106-132). 

Praeger. 

Gery, G. J. (1991). Electronic peT{omumce support systems (2nd ed.). Boston: Weingarten. 

Helmreich, R. {1987). Changing potelllial users to actual users: An evolutionary approach to office 

system acceptanCe. In M. Frese, E. UHch, & W. Dzida (Eds.), HUIIfOTI-Computer Interaction in the 

Work Place (pp. 81-94). Amsterdam: Nonb-Holland. 

London, K. R. (1976). The people side of systems. London: McGraw-Hill. 

McKenna, J. T. (1992, December 7). Airlines seek better sbarillg of safety data with FAA Aviation 

Week & Space Technology, p. 43. 

38 
AppeiKIII A, Coolputer Spedfleatlou 

C'..omputer #1 

Features 

Dimensions--1.6" H X 11.5" W X 9.3" D 

80386125 MHz CPU 

8 MB RAM (2 MB Std., 6 MB upgrade) 

130 MB Hard Drive 

Built-in keyboard 

External floppy drive (parallel port) standard 

Sidelit (backlit) 95" 64 shade VGA LCD display (blue) with brlghtnc>ss and contrast controls 

Optional built-in FAX/Modem (2400 baud modem/9600 baud fax or 14.4 ktaud modem/9600 

baud fax) 

Serial port 

Parallel port/floppy disk drive port (requires adaptor for parallel port) 

Monitor port 

1 PCMCIA slot 

Battery-operated pen 

Computer battery is replaceable 

Operating temperature range 41 to 104 degrees F 

Storage temperature range -4 to 140 degrees F 

Operating relative b.umidity 10% to 80% noocoodensing 

Storage relative humidity 5% to 80% noncondensing 

Shock toieraoce-operating 5g, nonoperating 80g 

Vibration tolerance-3-200-3 Hz at 0.4g (operating); 3-200-3 Hz at l.Sg (nonoperating) 

Alti~perating 10,000 fi; nonoperating 40,000 ft 

Electtostatic discharge 15kV 

Die-cast magnesium and Injection-molded 1hermoplaslic case 

5 llllbs. 

$2796 base price; $4070 configured 

Drawbacks 

1 hour battery life with standard battery and enfl"gy conservation features disabled. 

Pen ink is "noisy"; abated somewhat by supplied mterlng software. 

Keyboard only usable In landscape display rotation. 

Other Factors 

Pen "feel" simulates a felt tip pen on paper. 

Screen is good indoors and outdoors (but has rome glare). 

Optional beavy duty battery. 

Optional cigarette lighter power adaptor. 

39 
Pninion 

One of the favorites until handwriting recognition produces near 100% accuracy. Even then, it will be 

a good unit because the keyboard gives the unit more flexibility and because many people can type 

faster tJJan they can write. 

40 
Pen CollfJIIIIUB: EVfllwrtiev, Rtt:o11111Um111ltions, and the PENS Project 

Computer ##llllld Computer 13 

Features 

Dimeuslons--1.2"H X 11.7"W X 9.4"D 

80386120 MHz CPU 

8 MB RAM (4 M Std., 4 M upgrade?) 

40 or 60 MB Hard Drive 

Transfleclive 16 shade VGA LCD display (green)--Computer #2 

Backlit 16 shade VGA LCD display (blue) with single brlgbtoosslconttast conttol--Computec #3 

Serial port through docking strip 

Parallel port through docking strip 

Monitor port tbrough dockiDg strip 

Operating tempemture range 41 to 104 degrees F 

Storage temperature range -4 to 122 degrees F 

Operating relative humidity 5% to 95% 

Alti1ude--operating 9800 ft; nonoperating 40,000 ft 

No battery in pen 

Rechargeable computer batteey is replaceable 

Optional FAX/Modem. 

4 112lbs. 

$5350 CODfigured 

Drawbacks 

Choice between Flash Disk and hard drive. 

Pen "feel" is very slick, uncomfortable. 

Parallel port does not support floppy disk drive; one must choose between a fax/modem and a floppy 

drive controller. 

Othel" Factors 

A favorite pen stylus because of slim design, out-of-die-way button. 

BatteEy life of Computer #2 is longest of tested units becmse displliy is not backlit. 

Terrible sales support. 

Opinion 

Computer #fl. was discontinued while this report was being written. Computer #3 is probably in the 

bottom third of 386-based machines in terms of features, performance, and price. 

41 
Computer ft4 

Features 

Dhnensioos--1.2" H X 10.9" w X 9.8" D 

80486120 MHz CPU 

8 MB RAM (4 MB Std., 4 MB upgrade) 

40 or 80 MB ffilrd Drive 

Optional extemlll keytoaro 

External floppy drive ttandard 

Backlit 9.4" 64 shade VGA LCD display (blue) with bri~ and coldraSt controls 

Optional PCMCIA FAXJModem (2400 baud modem/9600. baud fax or 14.4 kbaud modem/fax) 

Serial port 

Parallel pottlfioppy disk drive port (requires adaptDc for parallel port) 

Monitor port 

2 PCMCIA slots 

Battery-operated pell 

Computer battery 1s riJI)Iaceable 

Operating temperature range 0 to 45 degrees c 

Storage tempt;rature range -20 to 60 degrees C 

Operaling relative bumidity 0% to 85% 

Storage relative bumidity 0% to 95% ooncondensing 

3.9lbs. 

$3999 base price; $5770 fully configured MSR 

Drawbacks 

TBD 

Other Factors 

TBD 

Opinion 

TBD 

42 
Computer#S 

Features 

Dimensions-2.1" H x 11.7" W x 9.3" D 

80486120 MHz or 80486125 MHz CPU 

8 MB RAM (4 MB Std.. 4 MB upgrl!de) 

80, 120, or 180 MB Hard Drive 

Built-in keyboard 

Internal floppy drive standard 

Backlit 9.4" 64 sbade VGA LCD display or 9.4" 256 color Super VGA active matrix display 

Optional PCMCIA FAX/Modem (2400 baud modem/9600 baud fax or 9600 baud modem/14.4 kbaud 

fax) 

Serial port 

Parallel port 

Monitor port 

2 Type n or 1 Type m PCMCIA slots 

Battery-{)}lefated pen 

Computer battery is repiaceable 

Optional second battery 

Optional docking station 

7.0 lbs.; but display can be removed to function as pen-only tablet 

·Price TBD 

Drawbacks 

Keyboard only useable in lancJscape display rotation. 

Otbel: Factors 

TBD 

Opinion 

TBD 

43 
Computer IS 

Features 

Dimensioos-2.1" H x 11.7" W x 9.3" D 

80486120 MHz or 80486125 MHz CPU 

8MB RAM (4MB Std., 4MB upgrme) 

80, 120, or 180MB Hard Drive 

Built-in keyboard 

Intemal floppy drive standard 

Backlit 9.4" 64 shade VGA LCD display or 9.4" 256 color Super VGA aclive matrix display 

Optional PCMCIA FAX/Modem (2400 baud modem/9600 baud fax or 9600 baud modem/14.4 kbaud 

fax) 

Serial port 

Parallel port 

Monitor port 

2 Type n or 1 Type m PCMClA slots 

Battery-operated pen 

Computer battery is replaceable 

Optional second battery 

Optional docking station 

7.0 lbs.; but display cao be removed to function as pen-only tablet 

·PrlceTBD 

Drawbacks 

Keyboard only useable in landscape display rotation. 

Otber Factors 

TBD 

Opinion 

TBD 

43 
>. ::;._,~'. 

Featl!res 

Dimeusioos-t.3•H X ll"W X U"D 

tm»>AB }A& a"J.J .BAlD~--- /_qpk>~.Am> ....... , ..... -..... RlJ MD 11-.1 Dd.e l- h> 1Jil) MD) 

R~w fBR'!\.IIb"DD nan~ mtlll\ nro f6 ~ Y~ l:JtSR <at.'l W~l WlU1 ~~"!' . ss 804 coullat COilll01s 

Sedal port 

Parallel port 

~~~~r 

~pilft 

Dullt-h> 9QlO Ni1i1 PAXDAOO Mud Modem 

"116t ~ ~ 16£ tor lllWEI' llllloc odn ffi!IIII'RiOD:'\: 

Da&tcry-opente!J pen 

Recbargeable COIJili''h 11attuy is ~aceable; 2 batteries std. 

4k 

moob.cllfiteiDV~IS3W~ 

<K4«t&. 

~ 

.. 

me;edS. 4 ('ll! I !IJiCd .. scseeD. iS IJIX evcoly liL 

:Pen~......,.,., ....,t\na PM l!ftlr!ruot!M tmhlmn'l 

...I!'"L::27..z;;;;l" 

JL L Jlii! •.. .:z-)JA~ __ ...., ·atJ!u!3--~ -- _-

Slow lllW i»i;c Mve. 

Oilier I"'?OM 

NO OlrrWll (1fJ pm ~ /JUr.llNRJ 1llDdcr-JbaD l2KlY l»lp). 

~R:e bulk-ln. •li rt Ne b ..... 

~~wz JH~ • .._ ____._ <d }_ )~ ----····· •am>f•l!b71'1!# a • f!&l-.-;a ~urr~~apulfiQ ~ 

@"'iW(~'?'Gf{l' ~1""W'n!! »m-..m~-

crv ~ .J:Uic. E5 2: ~ ~.ani u:se.. ...t. l-ours ~,., lDA.. WJ!II Dhov~ 9.V@m$!8.. 

QJ!{Rfl)ll 

UDU » sdaai"VCIT ~Lot 'il"*'hM''v 

1 
Cempaterf6 

Features 

Di!Df'.IISi9118-l.3"H X ll"W X ll"D 

80386125 MHz CPU 

8 MD RAM Std. (up to 20 MD) 

80 MB Hard Drive (up to 180 MD) 

Backlittrraosfler.tive (brtllgbtlng can be tumed off) 64 shade VGA LCD display (blue) with 

brigb!::ess L:l wullast ClOIIIlOis 

Se!ial port 

Pamllel port 

Floppy disk drive port 

Monitor port 

Bunt-in 9600 baud FAX/2400 baud Modem 

"Hot Dock" cJodcing port for power llldfor otbe£ CODDeCiiODS. 

Battely-operarecl pen 

b:bargeab1e COIIIplller battery is replaceable; 2 batteries std. 

4lbs. 

$2500 base price to VAR; S3SOO MSR 

Drawbacks 

SaeeD lll:eds CODSWit adjuslmeul; saeea is DDt evenly lit. Pre-production problem? 

Pen saatdles sa=a roatlng .f>le..procluct problem? 

Pen is difficult to Jelrieve from lioJder. 

Slow bald disk ddve. 

OOier F!!C!O!S 

No button on pea (pea t-•1" "" biDder more than tbey help}. 

Nice built-in. adjustLihle bancQe 

Units m• .. u•facbiRd by 1I!IIIK -OOD!l-act""' by large comp~ter manufv.turer. 

DesigJwl for la"""':ape disp)ay lOIIItion, but usable in portrait rotation. 

CPU battery Ufe is 2 bours baRi use, 4 boUis oonnaJ use. Well above average. 

Cln!n!on 

Unit is relalively well..designrd, but nnspertaen~ar. 

44 
Pen OJmprden: Evtduotions, Recommen41ltions, and the PENS Project 

Computer tl1 

Feature.! 

Dimensions-1.5" H X 10.6" W x 8.3" D 

80386125 MHz CPU 

8 MB RAM (4 MB Std. vs 4 MB upgrade) 

40 MB Hard Drive 

3.3 Volt "Low Power System" 

External floppy drive (paralleJ port?) standard 

Backlitll'raosflective (backlighting can be turned off) VGA LCD display (gray-brown) with 

brighlness and contrast COIIIrols 

Serial port 

Parallel port/floppy disk drive port (requires adaptor for parallel port) 

Keyboard port 

Monitor port 

2 PCMCIA slots 

Battery-operated pen 

Computer battery is replaceable 

3.3lbs. 

$3499 base price; $??'!? configured 

Drawbacks 

Pen batteries need fulquent replacement (eg. weekly). 

Hard disk is largest available for given d1mensions, but is still too small. 

Otlla" Factors 

Screen is good indoors and outdoors. 

The 2 PCMCIA slots will allow a data card and a fax/modem card simultaneously. 

Not rugged. but 3rd party is designing a "wetsuit". rubber, ruggedized case. 

Tested unit was early production. 

Opinion 

Assuming they can solve the pen battery problems, this will be a nice, small, lightweight. pen-only 

unit. 

45 
Computer 118 

Features 

Ruggedized 

Dimeos.!oos--2.0"H x 12.S"W x lO.l"D 

80386125 MHz CPU 

8MB RAM Std. 

85 MB or 190 MB Hard Ddve 

Soft keys built into be:l.el of display 

Backlit 64 shade VGA LCD 10" display (green) with brlghlress and contrast colllrOls; 

optional 11.6" SVGA 64 shade dlspJay 

Built-in 9600 baud FAX!l400 baud Modem S<d.; optiooal 960019600 FAX/Modem 

Serial port 

Parallel port 

Keyboard port 

Monitor P'Jrt 

Optional docking station 

Ballistic-composite main housing with aircraft aluminum and stainless steel fittings 

Battery-operated pen 

Quick-cbarge 3 hour computer battery with b:x:kup battery. 

6.5Ibs. . 

$5995 base price; $6495 configured w/o docking station; $6990 w/docking station 

.Qrawbacks 

Weigbl. 

Althougb battery monitor indicates over 2 .hourS of charge, it is closer to 1-1 112 hours. 

Other Factors 

Start-up company; company's only product; difficulty in l'llinging it to the market 

Optional keyboard unit bas floppy drive, portS. 

Gelling a demo unit was exttemely difficult; units received were pre-production. Company started 

production in 11/92. 

Opinion 

Ruggedness is contim•ally mentioned as a key criterion for field units; this is a good example. 

46 
Computer 118 

Features 

Ruggedized 

Dimeos.!oos--2.0"H x 12.S"W x lO.l"D 

80386125 MHz CPU 

8MB RAM Std. 

85 MB or 190 MB Hard Ddve 

Soft keys built into be:l.el of display 

Backlit 64 shade VGA LCD 10" display (green) with brlgt»ness and contrast colllrOls; 

optional 11.6" SVGA 64 sbade dlspJay 

Built-in 9600 baud FAX!l400 baud Modem S<d.; optiooal 960019600 FAX/Modem 

Serial port 

Parallel port 

Keyboard port 

Monitor P'Jrt 

Optional docking station 

Ballistic-composite main housing with aircraft aluminum and stainless steel fittings 

Battery-operated pen 

Quick-cbarge 3 hour computer battery with b:x:kup battery. 

6.5Ibs. . 

$5995 base price; $6495 configured w/o docking station; $6990 w/docking station 

.Qrawbacks 

Weigbl. 

Althougb battery monitor indicates over 2 .hourS of charge, it is closer to 1-1 112 hours. 

Other Factors 

Start-up company; company's only product; difficulty in l'llinging it to the market 

Optional keyboard unit bas floppy ckive, portS. 

Gelling a demo unit was exttemely difficult; units received were pre-production. Company started 

production in 11/92. 

Opinion 

Ruggedness is contim•ally mentioned as a key criterion for field units; this is a good example. 

46 
Pera Computers: E'l'llllultWns, Reeommendlllions, an4 the PENS Project 

Appencllx B, Evaluation/Implementation Questions 

-The following questions need to be addressed when specifying a pen computer for the Flight Standards 

Service: 

Environmental Immunity--How resistant is the unit to temperature extremes (eg. Anchorage in the winter 

to Puerto Rico in the summer), humidity, rain, etc.? 

Ruggedness-Can the unit be dropped? How susceptible is the screen to damage from collision? Will the 

paint chip from minor collisions? Is a ruggedized case necessary and available? 

Harness-Is there a harness or sttap to alleviaie carrying the unit and preventing damage if dropped? 

Weight--Are the units light enough to be earned for an entire work day? 

lighting Conditions--Will current units work in lighting conditions ranging from bright sunlight to 

absolute darkness? 

Display-Is the display monocbrome, grey scale, or color? How many shades or colOIS can be displayed 

simultaneously? What is the resolution? 

Pen-Is there a provision for tethering the pen so that it won't get lost? Will the pens allow user 

replacement of the batteries, rather than buying a new pen? Is the location of the button on the pen such 

that it is not accidentally depressed while writing? 

Pen Feel--Does the feel of "writing" with the pen on the computer simulate a pen on paper? 

Storage Capacity--What is the capacity of the hard disk, in Megabytes? 

Speed/Computing Power--What are the fastest and most powerful CPUs available? 80386? 80486? 80586? 

RAM--What are the available RAM capacities and speeds? At least 8 Megabytes are required; can more 

be put in? 

PCMCIA card slots-PCMCIA (Penonal Computer Memory Card International Association} cards allow 

peripherals, such as FAX/Modems, CD ROM controllers, and ROM (read only memory), to be easily 

added to and removed from the unit These cards are revolutionizing the portable computer industry. 

How many PCMCIA slots are available? 

Keyboard--Is there a keyboard built into the units? Is there a lightweight standard keyboard as an 

accessory to the units? 

CD-ROM Players--Do the units currently suppon. CD-ROM (compact disc, read ollly memory) players? 

FAX/Modem--1bese allow for communication with computers and other parties over the phone lines. Are 

they available for the pen colllpllte£? 

47 
CoDDeCtivity-Is tbe unit capable of supponiDg a network coDDeCiion, eitbe£ tbrough a serial port or a 

dedicated port? Wbat about wireless coDDeCiions? 

Upgrades-Are tbe£e user-l.'ilplaceable CPUs or otbec upgrade paths? 

Based 011 in-house evalumions, we m:OIIUI'Ibld field evallllllions. However, we can make the following 

consetvative rec01111t1e111!ati: 

Environmental Immunity aDd Ruggec!ress A ruggedized case that allows ODe to use the computer while 

it resides in the case will .improve ruggedness aDd e.nvir()ll1'lleDtlll immunity. Most CUJieDily available 

products will function in mist to very light rain. Cuaent pen COlllpilters Will operate in temperatureS 

ranging from about 20 degrees to 110 degrees Fabrenbeit. Because pen computers tend to be ve:cy 

susceptible to damage from dropping. tbe best approach may be to cboose one that is itself semi-rugged, 

but wbicb bas a ruggedized case. A ruggedized case will also allow an in..<:pector to use the unit in 1te 

rain, snow, etc. Only one company waeatly manufactures a unit that is already ruggedized 

Hamess-Eitlll% the unit itself or a ruggedized case should be equipped with a carrying strap or harness. 

1be currently available ruggedized unit comes with a carrying case that bas a strap. 

Weight-lbis is the primary draWback to ruggedized unim aDd becomes a problem when adlling a 

ruggedized case to otbe£ units. We think that a unit that does not allow one to remove the ruggedized 

case will be too heavy for general acceptanCe. A removable case Will allcw a minimum weight 

configuration for most uses, witll the flexibility to add the case (and, lienee, weight) when required. 

Cuaent weigbts range from llpiKO•Imately 3.5 lbs. to approximately 7 lbs. (for tbe ruggedized unit). A 

weigbt of llpiKOximately s lbs. is probably acceptable. initially. 

Ligbting ConditionsiDisplays-Most currently available 80386 based pen computers come with backlit. 

grey scale, VGA (16 to 64 simultaneous shades of grey, 640 x 480 pixel resolution) displays. Such units 

allow one to use them in the dark and in btigbt sunlight. 1be best such units allow i!!depende.nt control 

of contrast aDd.btigbtness. A monochrome display is nna<X:eptable {regardless of resolution); a grey sclile, 

VGA display is acceptable; while color, Super VGA {greater resolution, 256 colors) displays are not 

currently available, they would be pr>..felred. 

Pen-A tedJered pen is a little more difficult to use, but it is mucb more difficult to lose. Given the cost 

of replacement pens ($75-$100), we would recommend tetllering tbe pen. Again, given pen cost. we 

recommend that tbe pen allow user replacement of the batteries. A pen that has a button that prevents 

oDe from accide.ntally depressing it while writing is preferable. but not mandatory (because the pens can 

usually be rotated such that tbe button is out of the way). 

Pen feel-Ideally, writing on tbe pen computer would simulate writing with a pen on paper. Some of the 

available products are better than others in this regard. 

Storage Capacity-Current bard disk stmage capacities range from 40 Megabytes to 120 Megabytes. Wbiie 

40 Megabytes could be coosidered tbe absolute minimum, the more capacity one can get, tile more 

48 
Pen ColllpliiNS: El'tlhuztions, Reeommellllations, tuUl the PENS Project 

software programs/tools and data can be stored and used. We would recommend a 120 Megabyte hard 

drive for now, while keeping in mind that larger capacity hard disks will be available in the future. 

Speed/Computing Power--Currently, 80386, 25 Megaheltz CPUs are used in most pen computers. 

However, 80486 and 80586 CPUs with faster clock rates should be available in the near future. 

RAM-Because it is likely that the pen computers will be using Windows for Pen Computing as their 

operating environment, II Megabytes of RAM sbould be considered the absolute minimum requirement. 

Some manufacturers allow 16 Megabytes or more of RAM. The availability of RAM greztly affects 

processing speed and response times. 

PCMC~A card slots-Most manufacturers offer one PCMCIA slot. Because many desired features of the 

pen computer could be addressed through the use of PCMCIA cards, two or more slots would be better, 

although not ma!!datmy. 

Keyboard-We recommend that a roncealable keyboard be built in, similar to standard notebook or laptop 

computers; however, the pen computer must be fully functional when the keyboard Is concealed. That 

Is, tbe screen must be visible and allow pen input. even when the keyboard is concealed. The built-in 

keyboard wouid allow one to readily enter large amounts of text. Pen computers with built-in keyboards 

are compact and convenient. whereas detachable keyboards tend to be inconvenient and cumbersome. 

CD-ROM-It Is becoming increasingly clear that the pen computer will need to support a portable 

CD-ROM player. For the foreseeable future, a PCMCIA card or a parallel port will support this function. 

Ideally, a PCMCIA SCSI inielface card wlll be used to drive the CD-ROM because they are faster than 

parallel port devices. Portable CD-ROM players that use parallel ports are currently available. 

FAX/Modem--Most manufacturers offer FAX/Modems either as standard equipment or through a PCMCIA 

slot 

Connectivity-All pen computers aarrently supply a parallel port, whicb would allow connection to a 

network. We do not recommend that a wireless network connection provide the sole access to networks; 

a wired connection should be available. 

Upgrades-No manufacturer aarrently supports upgradeable CPUs, but this will likely change. Sucb 

upgrades would allow Flight Standards to take advantage of the most recent technology without scrapping 

the computer itself. 

49 
Appenclb: C, Eumple Evaluation Form 

Please rate the folloWing on a relative I-5 scale. where 1 is worst and 5 is best: 

Computec#l Computer#2 Computer#3 Compute£#4 

Weight 12345 12345 12345 12345 

Size 12345 12345 12345 12345 

Speed 12345 12345 12345 12345 

Display-inside 12345 12345 12345 12345 

Display-outside 12345 12345 12345 12345 

Pen Responsiveness 12345 12345 12345 12345 

Pen Feel 12345 12345 12345 12345 

Handwriting 12345 12345 12345 1·2 3 4 5 

Comfort 12345 12345 12345 12345 

Which product do you prefer? 

Computec#l Computer#2 Compute£#3 Compute£#4 

Which orientation do you prefet1 Horizontal Vertical 

Do you prefer to have the pen tellleted to the unit? Yes No 

Do you think you could carry any of these units for a normal work day? Yes No 

If a neck, shoulder, or waist strap were available. would you use it? Yes No 

Wbich wouid you prefer? Neck Shouldec Waist 

Would you prefer a rugged unit to one that is less tdgged. even ibough it weighs more? Yes No 

What are the three largest drawbacks to all of l:be&e )XO!Iucts'l 1. --------

2. ______ _ 

3. _______ _ 

so 
Pen Computers: Evalulltions, Recommen411tions, Gild the PENS Project 

Would you prefer using a smaller, more lightweight product (eg. less than 4 lbs.) with fewer software 

tools (eg. no word processors, spreadsheets, etc.) available or a heaver product with more tools? 

Lightweight, Few tools Heavy, More tools 

Would you prefer using a smaller, more lightweight product (eg. less than 4 lbs.) if software tools 

available on the pen computer (eg. word processors, etc.) were vecy different from those used in the 

office or & heavier product that used the same software as used in the office? 

Lightweight, Different tools Heavy, Same tools 

Would you prefer using a smaller, more lightweight product (eg. less than 4lbs.) or a heavier product 

with a built in keybo&rd? 

Lightweight, No keyboard Heavy, Built in keybo&rd 

Would you prefer using a smaller, more lightweight product (eg. less than 4lbs.) with an operating 

environment (eg. DOS) that was differelll from the office computer operating environment (eg. 

Windows) or a heavier unit with the same opell!ling system? 

Lightweight, Di:fferellt environmelll Heavy, Same environment 

Would you prefer using a product that was light, but not rugged, or a heavy, rugged product? 

Lightweight, Fragile Heavy, Rugged 

Would you prefer a standard laptop computer, without a pen (ie. no handwriting input), to the pen 

computers? 

Yes No 

51 
Appendk D, Summary MIDimum Hardware Speclflc:ations 

Currently, two different pen computer specifications are appropriate; one specification describes what 

is available today, while the other describes what may be cost effective in the future. 

Specification for available egul!WJMt 

Pointing device (eg. pen, mO"JSe,IIackball) 

Keyboard input device (either affixed, detachable, or "virtual") 

Storage device (eg. 40 Megabyte or greater capacity bard disk, PCMCIA card) 

20-25 Megahertz. 80386 CPU 

Display device: grey scale, backlit, VGA 

AdjustJible screen brigbtlress and/or co!llraSt 

8 Megabytes RAM, millimum 

Serial, Parallei communications pons (allo'll/S network coDDeCtion, for example) 

Replaceable, rechargeable batteries with at least O!le hour of operational capability without powersaving options in effect 

Battery cbargerlpower supply 

w eigllt less dum !J lbs. 

Floppy disk drive (external) 

External CD ROM drive 

Optional: 

FAX/Modem 

DockinJ! !ltation-sbould include: card cage, keyboard, floppy drives; may also include: color Super 

VGA monitor, large capacity hard disk, tape backup drive 

External IIIOIIitor connector 

Additional PCMCIA slots 

Ruggedized carrying caselsttap 

Specification for equipment available within 1-2 ye."'l!l: 

Pen pointing device 

Attached keyboard input device that accommodates either a horizontal or a vertical display 

orielltation 

100 Megabyte or greater capacity hard disk 

2 or more PCMCIA card slots 

33-50 Megaherlz. 80486 or 80586 CPU 

Color Super VGA monitor 

Adjustable screen brightness and contrast 

16 Megabytes or more RAM 

Serial, Patallel communications ports on the unit 

Replaceable, rechargeable batteries with at least three bours of oper&tional capability without powersaving options in effect 

Battery charger/power supply 

52 
Pen Computus: El'tzluafioru:, Recommeruitztions, and the PENS Project 

Weight less than 3 lbs. 

Bar code and/or magneti<; strip reader 

In!emal floppy disk drive 

CD-ROM drive (possibly internal) 

FAX/Modem 

Wireless LAN ("WaveLAN") 

Iiltemlll card slot (eg. for a network card) 

Docking station-including, but oot limited to: card cage, keyboard. floppy drives, color Super VGA 

monitor, large capacity hard disk. tape backup drive 

External monitor connector 

Ruggedized carrying case/strap 

53 
Correllltu of Indmdutll Di!feruu:u in Norutestnu:tive Inspection Peifo7'1RIJIU:e 

Chapter Four 

Correlates of Individual Differences in Nond~ctive 

Impection Perfonnanc:e 

4.0 INTRODUCTION 

This chapter is divided into four sections. The first section, Background and Survey of Relevant NDI 

Research, discusses nondeslructive testing and damage-tolerance design and research programs on NDI 

capabilities conducted by the Air Force, the nuclear power industty and the FAA. The General Survey 

of Inspec1ion and Vigilance Research section reviews research related to individual difference variables 

in inspection and vigilance. The remaining two sections, Research Needs and Proposed Research, outline 

the direction and methods of the NDI performance research tc; be performed undec the current FAA/AAM 

contract. 

4.1 BACKGROUND AND SURVEY OF RELEVANT NDI RESEARCH 

4.1.1 Nondestructive Testing and Damage-tolerance Design 

According to Panbuise (1989), in most industries, the inspection requirements for various components are 

defined in a specification document that describes the sensitivity level of the inspection method as well 

as the rejectable flaw size. These inspection requirements, designed to control both the inspection process 

and the quality of the inspeclfon results, define the detection/rejection requirements for each quality class 

material, the required procedures for meeting these requirements, and the required level of inspector 

training to meet requirements. However, several major, catastrophic failures of engineering systems (e.g., 

the F-111, space shuttle, nuclear reactors) led to the development of a new design method that assumes 

the existence of structural defects and then allows the designer to answer the following questions: 

• What is the critical flaw size that will cause failure for a given component subject to 

service stress and temperature ccnditions? 

• How long can a precracked structure be safely operated in service? 

• How can a structure be designed to prevent catastrophic failure from preexisting cracks? 

• What inspections must be performed to prevent catastrophic failure? 

The answer to these questions forms the basis of nondestructive inspection (NDI), which involves damagetolerance design and is centered on the philosophy of ensuring safe operation in the presence of flaws. 

Damage-rolerance design assumes that flaws exist as part of the normal manufacturing process. Flaw size 

is predicted to grow as a function of service usage and, in the case of aiicraft, will reach a critical size 

after a certain number of flight hours. Damage-tolerance design further assumes that nondestructive 

evaluations, performed on a periodic basis, will be able to detect such cracks or flaws before they reach 

this critical size. The validity of this assumption was initially evaluated in the aerospace industry during 

the 1970's with findings thai were profoundly disturbing, as described below. 

55 
Clulptu Four 

4.1.2 Air Foree Research 

4.12.1 Reliability of Nolldes!ructive Inspections (1978 Study) 

1be first, and most comprehensive field evaluation of NDI capabilities in the aerospace industry to date, 

was conducted by Lockheed in the 1970's in a major Air Focce study that bas since become known as the 

"Have Cracks, Will Travel" program (Lewis et al., 1978). This study, which began in 1974 and was 

completed in 1978, was designed to answer the following questions: 

• Wbat is the relative effectiveness of conventional NDI methods applied to structure (i.e., flaw 

detection probabililies relative to radiographic, ultrasonic, eddy-current, and penetrant 

inspections)? 

• Wbat is the Air Force field and depot capability in NDI? More specifically, wllat are the 

probabilities of flaw detection in structures by Air Force personnel and equipment? 

• Wbat differences, if any, exist in NDI capabilities ftom base 10 base? 

• How effective are 7 Level Air Force NDI personnel in devising NDI procedures? 

• Wbat is tlle range of individual capabilities among all groups (all bases) and within each 

group (base)? In otller words, what is the scatter factor attributed to individual differences 

and to differences between bases? 

1be approach taken was to obtain representative samples of six different types of aircraft structure with 

fatigue cracks ranging ftom .010 to 1.05 incbes. These structure samples were presented to the NDI 

technicians in settings which closely approximate<! those encountered in routine field and depot operations. 

Some were placed in an overbead position to simulate NDI on a lower wing surface, others were in faceup and vertical orientations. Twenty-two facilities were involved in the study, with an average of 15 

participants tested at each of the Air Logistics Centers and 6 at each field level base. Data obtained for 

each tecbnician consisted of (a) the IIIJIIlber of finds (hits}, (b) the number of false calls, (c) the number 

of no-finds (misses), (d) tlle ratio of finds-to-total flaw count, and (e) that ratio in percent. Also obtained 

were (a) the total finds ratioed to the total number of teelmicians and (b) that ratio in percent Each 

sample tested by a technician containerl flaws of various sizes; no samples were included that containl'il 

no flaws nor were there any samples included in which all sites were flawed. 

Military specification, MIL-A-83444 (USAF), • Aiiplane Damage Tolerance Requirements," states that inservice inspections are assumed capable of detecting cracks of specified lengths. A major finding of this 

study was the realization that the previously established 90-95 percent reliability criteria (90 percent 

probability of detection with a 95 percent confidence bound) for a .25 inch crack was not obtainable under 

normal field inspection. With the exception of dye penetrant inspection, the results inmcated considerable 

difficulty in achieving a 50 percent probability of detection for a l/2 inch crack size with a 95 percent 

confidence level. 

1bere were no significant differences (with tlle exception of one depot) in NDI performance between 

individual installations, between individual Commands, or between field inst2llations and depots. Nor v;-ere 

any significant differences observed be.ween teelmicians using different manufacturers' equipment 

For purposes of the present paper, the most significant findings were with regard to individual differences 

between inspectors. While it coma as no surprise that the study found considerable differences in the 

56 
NDI proticiencies of individual tecbnicians, the lack of any apparent relationship of such obvious variables 

as training and years of expedence to performance is swprising. There was essentially no relationship 

between performance and any of the following variables: 

• Skill level: Air force tecbllicians at three skill levels (levels 3, 5, and 7, representing new 

entrants iDto NDI, the majority of pmcticing tecbnicians, and advanced technicians, 

respectively) were compared with regard to their proficiency using each NDI method and on 

various types of structmal samples. Although some positive relationships appeared to exist 

between skill level and performance, there were numerous instances of no apparent 

relationship. 1be authors were led 10 conclude that cechnician proficiency in crack: detection 

ability was not significantly related to skill level. 

• Formal education: High school graduates, when compared to those lacking a high school 

diploma, did not differ in NDI proficiency. 

• Age: 1be ped'ormance of technicians under 25 years of age was ccntrasted with perlormance 

of those 40 years or older. As with skill level, the findings were mixed. with some 

comparisons showing a relationship and others not. 1be general conclusion, however, was 

that age was not systematically related to NDI proficiency. 

• Years of NDI expedence: As with age, two experience groups were compared: technicians 

with less than three years NDI experience were compared with those having more than ten 

years experience. Although age was generally confounded with experience, there was no 

evidence that experience pee se was significantly related to NDI proficiency. 

• NDI training: Hours of formal NDI training, as reported bY the technicians, were examined 

for effect on performance by contrasting tbo5e with under 200 hours with those having over 

500 hours. As with the previous comparisons, '!he amount of Nm training was found to be 

umelated to proficiency. 

To summarize the results of this study, the dominant finding was the failure to relate NDI proficiency to 

any of the personnel variables. However, the stndy was not without deficiencies, the must important of 

which was recognized by the authors. This was the failure to make use of any of the data collected on 

"false calls" in their analyses. Consequently, a technician could theoretically call every site visited a 

"flaw" and achieve 100% detection. 1be authors roJICluded, however, that, while some technicians showed 

extremely high false call counts and were then:fore suspect, those instances of extremely high false call 

count were not numerous enough to cause the total data andfor findings to be suspect. 

4.122 1978 NDI Reliability Workshop 

Concomitant with the release of the "Have Cracks, Will Travel" stndy, a Lockheed-sponsored workshop 

was held to preseot the study's findings (along with some additional material not contained in the stnltj 

report), and to solicit comments and recommendations from the workshop's participants (Lewis, Pless, and 

Sproat, 1978). Several aspects of this meeting relative to personnel considerations are worth mentioning: 

57 
Clulpter Four 

• 

• 

• 

4.1.2.3 

As a subsidiary aspect of the "Have CracKS" study, a techoician seleclionlscreelling method 

was developed to detennine wbelher simple fiat plate test pllllels containing cracks could be 

used lo assess profiCiency, and hence predict technician performance on the SIUdy' s SIIIlCIDral 

test samples. Twenty-six techoicilliiS participated with mixed results. The job sample task 

predicted ultrasonic performance with reasonable accuracy, but failed to predict eddy-current 

performance. In spite of these mixed findings, the use of a job sample approach was viewed 

as having considerable potential for predictiJJg technician performance 

Although not mentioned in the results of the primary study, data were presented at the 

workshop showing eddy-current performance plotted against the lllJIIlbeJ.· of eddy-current 

inspections performed per month. While the trend was weak, there was some evidence that 

poor performance tends to disappear with moderate fu:quency of inspections (more than ten 

limes per month). 

The task group charged with developing selection criteria/cecommendations devised the 

following profile for the ideal inspector. He or she should (a) have integrity, (b) have a sense 

of responsibility, (c) be mature enough to recognize his/her responsibilities, (d) take pride in 

accomplishments, (e) be self-motivated, (t) be self-disciplined, {g) have moral convictions, (!l) 

have allegiance, and (i) be good at decision-making ability. Obviously, lhJs profile would 

appear to characterize those traits desirable in employees in virtually any job. Howe·1er, either 

stated or implied in this list are several qualities that have surfaced repeatedly in talks with 

inspectors, managers, and NDI instructors. Desirable qualities stated generally relate to 

personal integrity, motivation or interest in the job, and the ability to make decisions. 

The Technician Proficiency Measurement Program 

The high degree of variability in technician proficiency found in the "Have Cracks. Will Travel'' study 

led the Air Force to consider possible forms of corrective action. As noted earlier, one of the subsidiary 

studies canied out under the "Have Cracks" project involved the assessment of a job sample test to predict 

technician performance. Although the findings were somewhat mixed, the approach was considered 

sufficiently promising to warrant further consideration. The result was the development of the • Air Force 

Technician Proficiency Measurement Program." This program was one in which practical tests involving 

nondestructive inspection of flawed aircraft structures, called test racks, were administered to technicians. 

The test racks, fabricated by the Lockheed-Georgia company, were made up of several specimen plates 

with simulated fatigue cracks of various sizes at randomly selected fastener sites. Technicians participating 

in the program were required to perform eddy-current or ultrasonic tests on the samples, with the resulting 

data scored in terms of hits, misses, false alarms, and true negatives. 

Background for the development of this program, as well as a detailed description of the tests and 

procedures used, can be fouad in a paper by Boisvert, Lewis and Sproat (1981). Jayachandran and Larson 

(1983) have reported on the use of the proficiency measurement test in a study of 360 technicians 

distribeted over 17 Air Force bases and 6 Air Force commands. Unfortunately, the study was concerned 

mainly with different methods for analyzing the data, and no attempts to assess the test's usefulness for 

either selection or training are reported. As v.ith the original "Have Cracks" study, results of the job 

sample test again revealed a wide range of individual differences among technicians in NDI proficiency. 

A subsequent stlldy by Summers (1984) examined relationships between personnel infonnation, as 

obtained from questionnaire items and performance (both ultrasonic and eddy-current) on the technician 

58 
.. ·, ~ .. 

proficieocy me• "emeul test. NDI proficieocy measures were obtained on 205 Air Force teSt participaeiS 

(125 inspeeiOis aDd 79 supervison}. (It is not clear as to wlleiJier tbis sample was taken ftom the study 

repolted lbo-ve by JayacbaDdran llld Larson or wbetber it was an eulirely differeut sample.) Of the 

respoDdeuls. 

• 63'J, - military; 37'J> civilian. 

• 87'J> were male; 13'J> female 

• 14'J> bad less tbaii a blgb scbool education. 

• SO'J, bad compltted bigh scbool Ollly. 

• 2S'J> bad as muc:h as 2 yem of coUcge. 

• ll'J> bad completed more lban 2 yem of college. 

Amwers to questiODDalre items were tabulated aDd related to pecformaDce on tbe ultrart>nic aDd eddycurrent job sample test!:. 1be following relalioDSbips were obtained. 

Negative finctiJ!!!!!: 

• Amount of formal scbooliDg was not significaatly telaled to job sample ptafOlmance 

• Neitbe£ eddy-aureut nor ultrasonic test data showed a relationship to 1he amount of NDI trainlng 

(Air Force or civilian). 

• 1bele was DO hyJ!cllion of a relatiOnship between perfonnance and wlleiJier or DOt a teclmician 

was a voiUIIleer me tbe NDI career field. 

• Previous e1pe1 !ence in metal worldDg prior to NDI trainiDg was liJJI'elated to NDI pedormance. 

• No slgnific:ant relationship was found between iDspector performance and tbe degree of like/dislike 

for preseat job or me tbe NDI career field 

• Al1bough self ntinp of lbJifty on eddy-c:um:ut aod ultrasonic performance were sigDificaatly 

correlated (1=.67), ldUal job sample perfonnance was umelated to an inctividual's self-rated 

abllity. 

• Performance on eddy-aureut aDd ultrasonic iospecti<>ns was DOt related to tile degree of 

comfortfdiscomfort tedmidans felt with equipmellt used in the inspection test!:. 

• Pedi e "W!Q'! on tbe iDspedjoD tasks was not sigoificantly re1ated to local on-the-job training or 

exif:tlng fl"Skkent NDI tralDing. 

• Nei1bec amount of time speal on NDI tasks (in 1belr J101111al job) nor time spent on inctividual NDI 

tccimiquc:s ~also relali-ve to tbeir preseat job} was related to ability to find flaws in the job sample 

tllSt. 

• Supervisor ntings of tedmician proficiency correlated DO bette£ with inspection test perfonnance 

than did t1r: tedpricians' self ratings. 

• Tbere was large Ylll'lability in eddy-cuneut aDd ulttasODic inql"dion pelformance across the 

sample among tedmiclans aDd aaoss bases and commands In general, .inspeclion results were 

too inooilsistent me maintenance managen to have confidence in NDI capability. 

59 
Cluqltq Fow 

Positive findings: 

• 'lbere was a sligbt, but significant tendency for teclmicians with more dian 2 years of college to 

have fewer false calls.. 

• The 17% of respolldents who stated tbey were certified by tbe American Society for 

Nondestructive Testers pe:fomled somewhat better in making finds tlwt did IIOilCeltffied 

inspectors on both eddy-current and ultrasonic tests. 

• Technicians who indicated an intention to re-enlist in the Air Force scored significantly bigbec in 

both bits and false ca1Js than did tbo!e who bad no such intention. (This suggests a motivational 

component that manifests itself as an increase in the frequency of positive responses.) 

It is evident that 1he Summefs study failed to identify clear-cut individual difference variables that 

correlate with inspection ptrlormanre. In Ibis respect, 1he study's conclusions did not differ appreciably 

from those of 1he earlier "Have Cracks. Will Travel" study. Neither study found any strong, collsistent 

relationships between persoDDel variables and inspection ptrlOl'IDIIDCe. Unfornmately, the Summers study 

was esseniially a summary final report and failed to provide much information on either the personnel d3ta 

obtained or on the metliods used in scoring inspection performance. Consequently, as with tile earlier 

1978 study, it is difficult to aitique or evaluate 1he findings. 

4.1.2.4 Reliability of NDI Applied to Aircraft Engine Components 

The previously desaibed "Have Cracks, Will Travel" study was direcled toward an assessment of NDI 

reliability on aiicraft structures under field conditions. However, it provided no information on the 

reliability or proficieDcy of Air Force impectDrs performing NDI on engine components. leaving 

nnanswered the question of wbedler 1he same levels of variability among inspectors found by Lewis et 

aL (1978) also applied to inspo IIJts in engine overbaul facilities. Consequently, llil Air Force sponsored 

study was coMncted by Loclrberd Aircraft to answer tllis question (Rmnmel et al., 1984). 1be apJEadl 

was similar to that used by Lewis et al.: Sets of gas turbine blades, vanes and disks were consttucted such 

that bait the items in eacb sampe set were IIOIIflawed and half were fiawed items, with flaws ranging in 

length from .01 to 0.5 inches Inspectors at two Air Force logistic centers employed dye peuetrant, 

magneti<: particle, ultrasonic, and eddY-current methods to test for fiaws. 

The general findings of 1bis study were similar to those found by Lewis et al.: (a) the overall reliability 

of nondestructive Inspections used by 1he Air Force in engine overllaul was found to be below that which 

bad been assumed or genenllly desired, and (b) variations in teclmician proficiency were observed and 

documented. With regard to this latter finding, however, the magnitode of 1he differences between 

techmcians did not appear as great as that obtained by Lewis et al.. and those differences that were 

observed seemed to be gelllr.llly allr:ibutable to recency of training/experience. Consequenl!y, no 

systematic attempts were made to relate teclmician proficiency to various subject or personnel variables. 

4.1.25 Recommendations for Improving Air Force NDI Reliability 

In 1987. Southwest Research Jnstinrte (SwRI) was contracted by the Air Force to investigate what might 

be done to improve teclmician proficiency. The approach taken in the resulting study (Schroeder, 

Dunavant. and Oodwin, 1988) used NDI experts to (a) identify relevam areas of concern that could 

ne~y impact 1he proficiency of Air Force NDI teclmicians. (b) seek possible solutions for 1he 

60 
Ctll'l'dllla of IlllllviduDl Dl,jfennees in Nondestnu:tive Inspection Petjo1'11UlnCe 

identified CODCmiS, and (c) Incorporate the most feasible, promising, and cost~ffeclive potenlial solutions 

into recoiiiiM:Ddations for improving technician proficiency. Since the present review is concerned only 

with Individual difference variables lllld tbeir relationship to NDI performance, only concerns and possible 

solutions relal'.ld tu Ibis topic will be reviewed bere. From the numerous concerns raised by tbe expms, 

three were cousidered most relevant. 'lbese, along with proposed solutions, are given below: 

A. Concern: Although NDI is a highly teclmical area, the Air Force has no intentional selection 

mP£hanism. Teclmicians come from tbe general manpower pool. 

Solution: As a short-term partial solution, h was suggested that samples be selected from the 

population who are higher in eleclronic and mechanical abilities, and then measure and compare 

their perfonnance with personnel selected using the current approach. 

B. Concern: 1bere are a number of candidate selection variables proposed in the technical literature 

(e.g., ability to concentrate, patience. manual dexterity, intelligence, temperament, motivation), but 

virtually no systematic researdl into wbich variables predict good NDI technicians. 

Solution: (a) Sponsor and collduct research to establish predictors of proficient NDI personnel, and 

(b) analyze any new data using receiver operator characteristic (ROC) based measures of 

proficiency. 

C. Concern: Much of tbe relatively little research that has been done is not meaningful, since 

measures of the predicted variable (proficiency) were not adequate. 

Solution: Analyze any new dam using receiver operator characteristic (ROC) based measures of 

proficiency. 

In a recent pboDe conversation with tbe principal author of tbis study, it was learned that, while the issues, 

concerns, and suggested solutions were received with considerable interest and enthusiasm by the Air 

Force, to tbe best of bis knowledge, no researcll programs have been funded to implement the 

recommended solutions (J. E. Sdlroeder, personal communication, September I, 1992). Schroeder stated 

that the problems the Air Force was having with differences in proficiency level of enlisted technicians 

has, to a large extent. been circumvented by hiring civilian teclmicians in their place. While tbis action 

may increase the overall level of inspection reliability, it is obviously a way of simply avoiding the more 

difticnlt problem of ascertaining reasons for differences among Air Force technicians, and then developing 

the necessary selection and/or training procedures to improve technician proficiency. 

4.1.3 Nudear Power Industry Research 

Apart from the Air Force, the only other major organization to carry on a systematic research program 

in the human factors of nondestructive inspection would appear to be the nuclear power industry. As noted 

in a report by 'Diggs et al. (1986), NDI inspection in the nuclear power industry suffers from many of the 

same problems found in the Air Force studies. Although confining themselves primarily to ultrasonic 

inspection, they note that relatively bigh error rates in flaw detection are commonly obtained. In one of 

the reported studies, probability of detection for 30 flaws ranged from 0.0 to 1.0, with a mean of 0.37. 

Imtitution of new procedures resulted in a decrease in flaws missed. However, even under the best 

61 
Chapter Four 

possible conditions, 34% of the flaws were still missed In a second reported study, an NRC (Nuclear 

Regulatory Commission) analysis of six teams, who inspected 80 circumfetential pipe welds requiring 

I ,500 operator judgements, fOUIId wide di1fereDces among teams and collditions of perfonnance and a 

wide range of success rates. (No actual reference is provided for eitber of tbe above two studies cited by 

Triggs et al.) 

Human factors research on variables related to NDI proficiency bas not been much greater in the nuclear 

industry than in Ll}e Air Force. That which bas been done bas been largely conducted under the aegis of 

the Electric Power Research Institute (EPRI) located in Palo Alto, California. Under contractual support 

from EPRI, Hams bas conducted several recent studies related to 1mman factors aspects of NDL In one 

of his more recent studies, information processing factors involved in ultrasonic flaw detection were 

investigated (Harris, 1990). Inspectors were hypothesized to employ some or all of the following factors 

in assessing signal characteristics: (a) Explicit hypothesis, (b) Test of explicit hypothesis, (c) Early 

conclusion, (d) Disregard of evidence, (e) If-tben logic, (f) Explicit signal discrimination, (g) Identification 

of weld geometty, (h) Verification of signal, and (i) Recognition of a malfunction or abnormality. A 

stepwise multiple-regression analysis revealed that most of the pedictive variability was contributed by 

five of the above factors - early conclusion, test of an explicit hypothesis, if-then logic, disregard of 

evidence, and signal continuity. It was concluded that an inspection approach based on a well-defined 

information-processing strategy offered promise for improving inspection performance. 

The study makes no reference to individual differences among inspectors. Differences are at least 

acknowledged, however, in a study of eddy-current inspection of steam generator tubes used in nuclear 

heat exchangers (Harris, 1991). Inspections of the test wnp1es by experienced analysts showed 

considerable variation between inspectors in accuracy of detection. The large differences in analyst 

performance were not predicted by the qualification testing conducted in accordance with existing 

guidelines and current induslry practice. The correlation between qualification test scores and pawntages 

of indications correctly reported was oDly 0.17, not sigoificantly different from zero. Beyond 

acknowledging this lack of relationsllip of qualification test scores to inspection performance, the study 

offered no further analysis of the obtained differences. 

In another study of NDI personnel in nuclear power plants, an attempt was made to evaluate the 

characteristics of the most proficiellt inspectors (Bebaravesb et al., 1988). Interviews were held with S7 

persons involved, in one capacity or another, with ultrasonic inspection - teclmicians, training supervisors, 

and vendor personnel Characteristics of highly competeut teclmicians, as deterlninPA from the frequency 

of characteristics mentioned in interviews were: 

• Can handle pressure/stress 

• Is conscientiouslreliablddedicated 

• Is independentlautooomouslself-confident 

• Is knowledgeable/sldltful/experienced 

• Is able to work well with others 

• Is mentally and emotionally stable 

• Has good attentionallperceptual/1110tor skills 

In referring to the above list of characteristics, Harris (1988) notes that "these are the genesal 

characteristics of people who are the most competeut in any job--airline pilot, assembler, police officer, 

62 
taxi driver, football player, Clllpelller, computer programmer, rodeo clown, aDd otherS" 8lld states that such 

characteristics are not sufficiently UDique to serve as tile basis for selecting persous who will become 

competent ulttasonlc lr.rspectors. The reader may remember that a similar list of cbaracteristics, refern:d 

to earlier, was compiled by participaniS at tile 1978 Air Force workshop on NDI reliability. 

4.1.4 Federal Aviation Administration (FAA) Researcb 

4.1.4.1 The State University of New York (SUNY) Program 

Acting in respoose to ll1e Aviation Safety Research Act of 1988, Public Law too-951, ll1e FAA's Office 

of Aviation Medicine bas established a human factors research program to investigate aira"aft maintenance 

and iospection practices, especially as these are applied to aging fleet repair, and to evaluate and 

recommend imp-ovements The current program, carried out largely under contract with Galaxy Scientific 

Corporation, is conducting research to improve IXactices in several related areas. These include, but are 

not limited to, the maintenance organization itself, maintenance inspection, advanced technology for 

training, and job aids. For purposes of the present paper, only that aspect of the total program dealing 

with iospection will be considered here. This presentation will be fur1her narrowed to concentrate on that 

portion of the maintenance inspection research program dealing with task simulation of NDI. 

As a subcontractor for Galaxy Scientific, Dr. Colin Drury at ll1e State University at New York at Buffalo 

is conducting a substantial research program in aircraft inspection. In essence, work thus far bas largely 

concentrated on development of task descriptious, task analyses, and a detailed error taxonomy. In 

addition, however, Dr. Drury bas developed a simulated NDI task, using a SUN workstation, that 

incorporates tile physical aspects and functioml characteristics of an eddy-current NDI task. As was atated 

in ll1e initial research study using this simulation, ll1e task was not developed with the intention of 

measuring absolute values of the probability of detecting particular types and sizes of flaws, nor was it 

developed as a means of training inspectors for the actual tasks involved (Latorella et al., 1992). The 

intended use of the task, then, was and is to explore variables related to inspection performance and to 

isolate those that might have potential relevance to the operational environmenL ('Ibis siomlated NDI task 

will 1le described in greater detail in a later section of this paper as well as its intended use in proposed 

studies.) 

A basic intent of the NDI study mentioned above was to evaluate the use of off-line performance 

feedback. Also included, however, were two personality tests previously shown to correlate with 

iospection performance. These were the Embedded figures Test (a measure of field dependency) and the 

Matching Familiar figures Test (a Ct'~nltive style measure of speed vs. accuracy in performance). The 

study failed to demoustrate improved performance as a result of off-line feedback, presumably because 

of the large between-subject variability. Interestingly, one of the two co variates based on the personality 

tests did show a relationship to perfonnance. lbus, the covariate based on a composite index comprised 

of Matching Familiar figures Test and visual acuity scores, was significantly relaied to both total task time 

and to ll1e decision criterion used. 

Drury clearly feels, with some justification, that intensive investigation of individual difference variables 

as possible correlates of inspection performance is likely to have a rather low probability of success 

(Drury, 1992). However, he has also noted that continued Study of individual differences in aircraft 

iuspection sbould not be disparaged. because the payoff for establishing a reliable and valid inspection test 

63 
CluJptu Fow 

would be large (Shepherd et al., 1991). 1be sizable between-subject variability found in the above study 

by Latorella et al. (1992) is certainly consistent with Air Force and nuclear industry studies reviewed 

earlier, and the finding of a relationship between cognitive style auc1 NDI pecfOI'IIIliiiCe supports the 

present author's belief that at least some of the variance in inspection performance is related to individual 

difference variables of potelll.ial use in selection. [lbis variable {cognitive style) and othen: will be 

considered latter in a seclion dealing with laboratory and field studies of individual difference variables 

and general inspection performance.] 

4.1.4.2 The Sandia Program 

Another research program in NDJ has been funded through the Aviation Safety Divisicn of the FAA 

Technical Center. One aspect of this program is the establishment of an Aging Aircraft NDI Development 

and Demonstration Center {AANC) at the Sandia Corporation. The essential purpose of this center is to 

suppon NDI technology, technology assessment, technology validation, datll correlation, and automation 

adaptation as on-going processes. A second aspect of the program i> to determine how well current 

equipment and procedures used in the field detect structural flaws (Spencer et al., I992a). Only the field 

program will be briefly discussed here. 

The stated objective of the field research study is to evalu&te the reliability of eddy-current inspection 

procedures as they are done routinely at airline maintenance and illspection facilities (Spencer et al., 

1992b ). As described in this report, the planned experiment will be specific to inspection procedures used 

on Boeing 737 lap splice joints with sliding probe, oversize templale, and rotating surface p-obe NDI 

eddy-current techniques. Panels of test samples will be developed with each panel containing differing 

frequencies of tlaw length and density. Test samples will be evaluated by inspectors at different facilities 

and during different shifts. In evaluating factors that could affect reliability, the specific objectives of the 

study are to: (a) Assess Effects of Off-angle Cracks; (b) Assess the Effect of Inspecting Painted Versus 

Unpainted Surfaces; (c) Charadaize the Reference Standards Used Within a Facility; {d) Assess Effects 

of Accessibillty; {f) Access InspectiQn TJJDe Effects; {g) Gather Facility Specific and Inspector Specific 

Data as Potential Explanatory Factors; {h) Provide Baseline (Laboratory Environment) Inspection 

Reliability ABsessments; (i) Assess Effects Col!!lfUed with Sbift Work; and (j) Assess the Effect of 

Specimen Definition. 'Ibis latter factor refers to assessing possible differences between test results 

conducted on "real" flaws and those generated by various artificial means. 

It is anticipated thal nine facilities will be visited, representing a range of facility characteristics. Data 

obtained from four inspectOrs at each facility will be analyzed in iemiS of probability of detection (POD) 

measures and measures derived from receiver operating characteristic (ROC) curves. Personnel data 

obtained on each inspector will include age, sex, pllysical condition, NDI experieoce, time since last 

performed eddy-current testing, amount of equipment-specific training, and perceived importance of NDJ 

to management, as well as to the individual inspector. Each facility will be rated on lighting, temperature, 

atmospheric conditions, management practices, tools, general housekeeping p-actices, and noise level. 

Facility differences in p-ocedures, equipment, training, and environment are thus considered to be pan of 

the system being consi<bed and will be analyzed as potential explanatory factors for observed variation 

in inspection results. 

The Sandia Ellldy, then, is obviously quite different from the SUNY program in purpose and scope. 

However, it is swpr.lsingly similar, botil ln purpose and methodology, to the previously described Air 

64 
Colftflllu of IndMtlual Dljfenm:es in NondesiTUdive Inspection Per[o171111TlU 

Force "Have Cracks, WID Travel" study. 1be major difference between the two studies would appear to 

be that tbe Sandia study plaus to iiiCOipOiate false alarm data in their assessment of reliability while the 

earlier Air Force study failed to do so. Many of the same individual difference variables (e.g., age, years 

experience, level of NDI training) incorporated in Air Force studies (Lewis et al., 1978; Summers, 1984) 

are also iDCluded in the S8Ddia study. like the earlier Air Force studies, the Sandia study will not attempt 

to experimentally control for any of these persoDDel variables, but rather will depend on correlational 

analyses to reveal possible relationships of eacb variable to NDI performance. The vaiue of such an 

approach is, of course, dependent upon the extent of attribute variation in the samples that are available. 

4.2 GENERAL SURVEY OF INSPECriON AND VIGILANCE RESEARCH 

4.2.1 Inspection 

The single most consistent finding of the Air Force and nuclear power industry NDI research programs 

and studies reviewed thus far has been the fi!Kiing of sizeable and consistent individual differences among 

inspectors. Perhaps not surprising, this was also the most consistent finding reported by Wiener (1975) 

in his review of individual difference variables in inspection research carried out in university laboratories 

and in industrial settings. Unfortunately, like the Air Force and nuclear power pl11nt studies, Wiener found 

little evidence of a consistent relationship of various individual difference (selection) measures to inspector 

performance. However, most of the studies reviewed were conducted in what Wiener refers to as the "preergonomics era" (during and prior to World War II). These studies frequently used such questionable 

messures as supervisor's ratings as criteria. This was particularly tme of the early studies employing 

aptitude tests. Of the aptitude tests employed, none was tailor -made for predicting inspection performance. 

The only aptitude test that has apparently been devised specifically for inspection is the Harris Inspection 

Test (HI1). a paper-and-pencil test that can be administered in 10-20 minutes (Harris and Chaney, 1969). 

As reported by Harris and Chaney, the test was successfully validated on six inspection tasks. 

Unfortunately, Wiener (1975) reportS that a later study by Chaney and Harris found test results to be 

unrelated to inspection performance. (More recent use of this test. as well as others, will be given shortly 

when other studies by Drury and his colleagues are considered.) 

Apart ftom "isual tests, such as acuity which has obvious relevance to visual inspection, Wiener confines 

the remainder of his review to personality, gender, age, and intelligence as possible factors related to 

inspection proficiency. With the exception of age. Wiener found little or no research had been conducted 

that was specifically directed at the relationship of personality measures, gender, or intelligence to 

inspection performance Age effects were found to have been studied by various investigators. with some 

evidence that inspection- proficiency deciines with age. However, conflicting findings led Wiener to 

conclude that any age-related differences in inspection are likely be small and of minimal significance. 

(It will be recalled that a similar finding was reported in the "Have Cracks, Will Travel" study.) 

4.2.2 Vigilance 

Vigilance research has often been considered in conjunction with inspection findings because the two areas 

have much in common. 8oth frequently involve sustained attention, decision making, and may involve 

visual search and scaooing. Interestingly, both inspection and vigilance are characterized by sizeable 

individual differences and relatively consistent within-Sllbject performance over time. Researchers 

65 
Clulpter Four 

attempting to account for individual differences in vigilance performance have often been as frustrated as 

those working in the area of inspection. 

It is for many of these reasons that reviews of individual difference variables in inspection research, such 

as the one by Wiener (1975) just consideced, generally include vigilance findings as well. Thus, Wiener 

reviews studies that have eXliDiine<l the relationship of gender, age, intelligence, and personality variables 

to vigilance performance. In general, the findings have been similar to those of inspection research. wilb 

gender, age, and intelligence showing either an inconsistent or lack of relationship to vigilance 

performance. Personality variables, studied wilbin the context of vigilance have, however, been somewhat 

more successful in predicting performance. This is particularly true of tbe introversion-extroversion 

dimension, where introvetts are hypotbeslzed to perform better than extroverts (Eysenck. 1967). Although 

few of the studies reviewed by Wiener show a clear-cut superiority of introverts over extroverts, none 

show the opposite. [A recent review of extroversion and vigilance using a meta-analysis of studies 

covering a 30-year period generally supports tbe belief that introverts are superior in vigilance 

performance, but the effect size was found to be quite small because of a high incidence of inconsistencies 

(Koelega, 1992).] 

A later review of individual differences in sustained attention or vigilance extends the earlier findings of 

Wiener and focuses more directly on personality variables (Berch and Kanter, 1984). The introversionextroversion dimension is again shown to be rather consistently related to monitoring, although admittedly 

most of the studies reviewed were ftom the same time period encompassed by the Wiener review. Two 

additional dimensions not included in tbe Wiener paper were field dependence/independence and locus 

of control. Berch and Kanter cite examples of studies showing both field independence and internal locus 

of control to be related to superior vigilance performance. With regard to age, gender, and intelligence, 

these reviewers are in accord with Wiener in that there is little evidence to support a relationship of either 

gender or intelligence to monitoring performance Some studies showed a relationship of age to 

monitoring performance, but perhaps only when certain conditions prevailed. These conditiol's are 

believed by Davis and Parasuraman (1982) to occur wben: (a) detection of more than one signal is 

required; (b) the event rate is high; (c) visual search is involved; (d) an increased memory load is required 

for reporting or discriminating the critical signal. A number of these conditions were present in a study 

of complex monitoring petfOlUlliiiCe comparing young, middle-aged, and older subjects (Thackray and 

Touchstone, 1981). Both the onset of attentional decline as well as its magnitude were found directly 

related to age. 

The preceding, rather cursory examination of individual differences in both inspection and vigilance was 

intended to emphasize both the prevalence of wide subject variability found in the two related areas of 

research and to highlight the fact that neither area has been too successful in finding significant correlates 

of this variability. Within the past 10 years, however, several studies have been carried out to clarify 

reasons why the selection approach has thus far met with minimal success (Gallwey, 1982; Wang and 

Drury. 1989). The initial study by Gallwey (1982), based partially on an earlier task analysis of a visual 

inspection task by Drury (1975), used a variety of selection tests to predict inspection performance on a 

computer-generated symbol task containing multiple fault types. The task was designed to simulate a 

typical industrial inspection task containing elements of visuai search, memory, judgement, and decision. 

The tests were chosen to tap different subtasks of the primary t:l.ik. In general, the subtasks involved 

scanning an area to select a fixation region, examination of items within the region, comparisons with 

images in memory, and a decision to accept or reject item(s). Tile tests used included a measure of visual 

66 
COJTrJIIltu of lndivillual Differences in Nondestnu:tille lnspectiDn Perjo1'111111Jce 

acuity, the Hams InspecUon Test, the Eysenck Personality Inventory, a questionnaire on mental imagery, 

a card sorting task, two portions (the Emtredded Figures Test and a composite test consisting of the 

Arithmetic, Digit Span, and Digit Symbol subtests) of the Weschler Adult Intelligence Scale (W AIS), the 

Embedded Figures Test, a mCIIl>"Ure of short-term memory, a measure of visual lobe size, and a measure 

based on part-task performance (single fault detection) of the primary task. Some of the more important 

findings were as follows: 

• Single fault detection time was a very good predictor of detection time on the primary or 

multiple fault task. 

• The W AIS composite score (a measure of attention-concentration) was effective in predicting 

probability of search and classification errors. 

• Extroversion scores obtained from the Eysenck Test correlated significantly with search errors, 

with low scores on extroversion related to fewer errors. 

• The Embedded Figures Test was found to be the best single predictor of inspection performance, 

being related to search time, search errors, and decision errors. 

• Visual lobe size was a reasonable predictor of classification errors. 

A second study comparing a variety of selection measures with inspection performance was reported by 

Wang and Drury, (1989). Based partially on some of the findings of the Gallwey (1982) study, these 

authors hypothesized that the skills and abilities of inspectors may indeed be task specific. If this is the 

case, and different inspection tasl:s require different skillslabilities, then the search for a general 

"inspection type" or a single selection task could prove to be a futile exercise. Thus, a more fruitful 

approach might be to select only those tests expected to correlate with the particular skillslabilities of a 

specific inspection task. In order to identify those skillslabilities, Wang and Drury first provided a sevenstep task description of a generalized inspection task. These StilS are: 

( 1) Orient the item to be inspected. 

(2) Search the item. 

(3) Detect a flaw or unusual phenomenon. 

( 4) Recognize/classify the phenomenon. 

(5) Decide on stalUS of item. 

( 6) Dispatch item to appropriate destination. 

(7) Record information pertaining to the item. 

Each of the above steps was then analyzed in terms of the skills (manual or perceptual) and abilities 

(attention, perception, memory, detection, recognition, judgement, classification) required. Based on the 

generalized task description, 11 tests, selected as potential measures of each of the above abilities, were 

incorporated as pretests in the st:Idy. Three different inspection tasks were chosen to represent different 

types of inspection. These were: (a) Circuit Pattern inspection, a pure search task; (b) Computer 

Generated Symbols inspection task, used previously by Gal1wey (1982) and which incorporates both search 

and decision; and (c) Color Video Comparator inspection of printed circuit boards, representing a real 

inspection task currently used by electronics manufacturers. Each of 12 subjects performed all three tasks. 

Separate factor analyses of pretest ar.d performance scores revealed four pretest factors (labeled as 

Attention, Perception, Judgement, and Memory) and five perfoi'IIWlce factors (generally encompassing 

various measures of search time, search errors, and decision errors). Pearson correlations were also 

67 
Chllpter Four 

computed between the four pretest and five perfonnance factors. Several significant relationships were 

obtained: 

• The Attention factor was significantly correlated with search error and search time (the higher 

the attention score the fewer the search errors). 

• The Judgement factor was significantly correlated with decision error (the higbee the judgement 

score the fewer the decision errors). 

• Time and error scores fell into different groupings, showing that speed and accuracy represent 

different aspects of performance 

• Correlations for each of the three inspection tasks tended to cluster together witbin particular 

factors 

• Tests loading on the Perception factor correlated with speed of visual search. but only on the 

computer -generated symbols task. 

Although significant relationships were obtained, the patterns were far from clear. For example, none of 

the preteSts demonstrated consistent predictive ability of search performance across the tbree inspection 

tasks. Thus, a perceptual or attention-concentration test that predicts search performance well on one task 

may not be a valid predictor on another. In summarizing their results, the authors conclude that: 

the best strategy in developing a valid inspection selection device would be to find out the 

specific mental requirements for the particular task by conducting a detailed task analysis, 

as weD as by eliciting information from experienced inspectors. Then, based on these 

mental requirements, select a set of valid test items which can effectively measure those 

cognitive traits and, thus, produce one's own version of an inspection selection battery. 

(Wang and Drury, 1989, p. 189) 

4.3 RESEARCH NEEDS 

It was noted, in the 1988 Southwest Research Institute study of recommendations for improving Air Force 

NDI technician proficiency, that no research had been carried out with the specific intent of studying 

individual difference variables in NDI performance (Schroeder et al., 1988). Since the time of this 1988 

study, there has apparently been only one study conducted that has at least ('xamined a few individual 

dif1'ereLce variables in NDI performance. That study is the study referred to earlier by Latorella et al. 

(1992) in which two psychometric tests, the Embedded Figures Test and the Matching Familiar Figures 

Test, were correlated with performance on the SUNY simulated NDI eddY-current task. The finding that 

one of these tests, the Matching FIUililiar Figures Test. was significantly related to several performance 

measures suggests that at least some of the subject variance in performance can be accounted for, and that 

a more concerted effort. using tests covering a wider range of abilities, is warranted. Although research 

efforts have ~,. e!' rather unsuccessful thus far in devising predictors of general inspection or vigilance 

perfor.Al;mce, this may be, as was indicated in the above quote from the Wang and Drury paper, that 

pwJictor measures are at least partially task specific. Consequently, and as these authors suggest, the most 

premising approach may be to select tests based on a detailed analysis of task behaviors for the task in 

mind, and thus produce a selection battery more likely to correlate with performance on the intended task. 

It is the intent of this research project to utilize this approach to develop useful predictors of NDI eddycurrent performance. 

68 
Correlllta of 11U/iJiiilu4l Differences in Nondestructi'le Inspection Peifo171Ul1U:e 

4.4 PROPOSED RESEARCH 

The research proposed here will incorporate elements of the recent findings of Drury and his colleagues, 

specifically with regard to NDI performance, with the findings of Thackray and others (e.g., Thackray et 

al., 1973, 1974; Thackray and Touchstone, 1980) who have examined correlates of sustained vigilance 

performance, with the intentlon of (a) isolating variables that successfully predict NDI task performance 

and (b) examining the interactions of these relationships with sustained performance on an NDI task. 

The task to be used is the simulated NDI eddy-current task devised by Drury and his colleagues and 

described in studies by Drury et al. (1991) and Latorella et al. (1992). In essence, the task is implemented 

on a SUN SP ARC workstation using a standard keyboard and optical three-button mouse as input devices. 

'The aisplay consists of four windows: 

Inspection Wmdow. The left-central portion of the screen displays rows of simulated aircraft 

fuselage rivets. The subject uses the mouse to circle each rivet in order to classify it as defective 

or nondefective. 

Macro-view and Directionals. A macro-view in the upper left portion of the screen allows the 

subject to determine where, or what area on the total simulated fuselage, he is currently examining. 

Eddy-Current Meter. Defect indications are displayed in a simulated analog meter located in the 

upper right window of the screen. DeflectioDS lleyond a set point on the meter produce an audible 

alarm as well as a red flash on an indicator light. The particular meter value cf the set point may 

be either subject or experimenter determined. Subjects judge whether detlections beyond the set 

point value are likely to be indicative of a defect. 

Lower-Right Window. 'Ibis area of the display is used as a dialogue region in which subjects may 

use the mouse to exercise a number of task options (e.g., "zoom" to take a closer look at a rivet 

being inspected, stop task in orde£ to take a break, display elapsed time, record subjective 

assessments). 

The NDI simulation program generates an output file of the subject's performance which gives summary 

performance measures for the entire task. 1bese include measures of time taken for various aspects of 

the task, number of bits, misses, and false alarms, total number of faults present, number of rivets 

classified and unclassified, and total number of rivets visited. 

A SUN SP ARC workstation has been procured by CAMI and the HOOPS graphics software installed. 

Arrangements will be made shortly with Dr. Drury at SUNY to procure and iDS!:all the NDI simulation 

software. 

Phase D of the present contract, then, is to conduct a pilot study using the SUNY NDI simulation with 

the intent of examining the relationships of a number of potential predictor variables to performance on 

this task. The first several months of this phase will largely be spent (a) in familiarization with the NDI 

task and its functional cbaracterislics and (b) in selecting tests and measures that would appear to be 

promising measures of the relevant task behaviors involved. It would be premature at this time to specify 

exactly all of the behaviors to be assessed or the particular tests most relevant to each. However. based 

69 
Clulpter Four 

upon interviews with NDI inspectors and instruct~Jr>s, the findings of Drury and Olbers relative to both 

general and NDI in&peclion, and upon the work of various researcllefs in the area of vigilanre, measures 

of the following would appear potentially related to task perfonnanre and lilrely caudidates for inclusion: 

• Decision Making(Judgement 

• Concentration/ Atlentiveness/Disttaction Susceptibility 

• Motivation/Curiosity/Perseverance 

• Boredom Susceptibility 

• Sustained Attention 

• Mechanical/Electronics Interest and/or Aptitude 

The experience of Drury and his colleagues in using the NDI task will be utilized extensively ill 

formulating the teslingftask protocol. Thus, it is anticipated that much of the subject's first day will be 

spent in (a) receiving m orientationfmdoctrlnation in eddy-eunent testing and in the need for 

nondestructive testing in genecal, (b) taking the various psychometric pretests, including visual acuity tests, 

and {c) administering essentially the same training procedures used by Drury and his colleagues (Druzy 

et al., 1991) in their report of a pilot study using this task. This will then be followed by one or two days 

of sustained performance on the task. (Actual periods of task performance will be detennined after 

gaining familiarity and experience with task cbaracterlstics.) It is expected that 5 to 8 subjects will be 

tested in the pilot study. The pilot study will be completed on or before May 1, 1993 and a report of the 

findings submitted to Galaxy Scientific Corporation. 

4.5 REFERR~CES 

Bebravesh, M. M., Darimi, S. S., & Ford, M. E. (1988). Human factors affecting NDE technician 

performance. Proceedings of the Ninth lntematiolltll Conference on NDE in the Nuclear Industry, 

Tokyo, Japan. 

Berch, D. B. & Kanter, D. R. (1984). lndividualllifferences. In J. S. Warm (Ed), Sustllined attention 

ill human performance. New York: Wiley. 

Boisvert, B. W., Lewis, W. H., & Sproat, W. H. (1981). Uniform qualifications of military and civilitm 

nondestruCtive inspection personnel. Report No. LS81 WP254-003, Lockheed-Georgia Company, 

Marietta, Georgia. 

Davis, D. R. & Parasuraman, R. (1982). The psychology of vigilance. New York: Wiley. 

Drury, C. G. (1975). Inspection of sheet materials - Model and data. Human FDCtt>rs, 17, 257-265. 

Drury, C. C., Prabhu, P., Gramopadhye, A., and Latorella, K. (1991). Norulestructive testing ill aircraft 

inspection. Report of a pilot study prepared under subcontract 89-1014-SC-3 to Galaxy Scientific 

Cc1}JOration, Mays Landing, New I~ney. 

Drury, C. G. (1992). Inspection performance. In G. Salvendy (Ed.), Handbook of imlustrial engilu!ering, 

second edition. New York: Wiley. 

70 
Cornltltes of lndMdutll Differenees in No:u/eslruelive Inspection Per/o17111111U 

Eysenck, H. 1. (1967). The biological basis of personalily. Springfield. Dlinois: Thomas. 

Banis, D. H. (1988). HU111Q11 perfoTmllliCe in nondestructive inspections and fwzctional tests. EPRI NP6052, Project 2705-9, Prepared for Eledlic Power Research Institute, Nuclear Power Research Institute, 

Nuclear Power Division, Palo Alto, California. 

Harris, D. H. (1990). Etlect of human informalion processing on the ultrasonic detection of inttagranular 

stress-corrosion cracking. Materials Evaluation, 48, 475-480. 

Harris, D. H. (1991). &1dy current steam generator data analysis performanre. In D. A. Steining:r (Ed.). 

NDE techniques for nuclear heat exchangers. Proceedings of the 1991 International Joint Power 

Creneration Conference, American Society of Mechanical Engineels, San Diego, California. 

Harris, D. H. & Chaney, F. B. (1969). HUIIUJtl factors in quality assurance. New York: Wiley. 

Gallwey, T. J. (1982). Selection tests for. visual inspection on a multiple fault type task. Ergonomics, 

25, 1077-1092. 

Jayachandran, T. & Larson, H. J. (1983). Statistical analysis for the nondestructive inspection (NDI) 

technician proficiency measurement program. NPS-53-83-0008, Naval Post Graduate School, 

Monterey, California. 

Koelega, H. S. (1992). Extraversion and vigilance performance: 30 years of inconsistencies. 

Psychological Bul!elin, 112 (2), 239-258. 

Latorella, K. A., Gramopadhye, A. K., Prabhu, P. V., Drury, C. G., Smith, M. A. & Shanahan D. E. 

(1992, October). Computer-simulated aircraft inspection tasks for off-line experimentation. Paper 

presented at the Annual Meeting of the Human Factors Society, Atlanta, Georgia. 

Lewis, W. H., Pless, W. M. & Sproat, W. H. (1978). Proceedings from the govemment/"uulustry 

workshop on the relillbility of nondestructive inspections. Report No. SA-ALC/MME 76-6-38-2. 

Lockheed-Georgia Company, Marietta. Georgia. 

Lewis, W. H., Sproat, W. H., Dodd, B. D. & Hamilton, I. M. (1978). Reliability of nondestructive 

inspections- Final report. Report No. SA-ALCJMME 76-6-38-1, Lockheed-Georgia Company, 

Marietta, Georgia. 

Panhuise, V. E. (1989). Introduction. In Merals handbot:Jk, 9th F.d., Vol. 17, Nondestructive evaluation 

and quality control, ASM International. 

Rummel, W. D., Mullen, S. 1., Christner, B. K., Ross, F. B., & Marthart, R. R (1984). Reliability of 

nondestructive inspection (NDI) of aircraft engine r:omponents. Report No. SA-ALCJMM!II51, San 

Antonio Air Logistics Command, Kelly Air Force Base, Texas. 

71 
Chopter Four 

Schroeder, J. E., Dunavant, D. W., & Godwin, J. G. (1988). Recommendations for improving Air Force 

nondestructive inspectitm technician proficiency. SwRI Project No. 17-7958-845, San Antonio Air 

Logistics Center, Air Force Logistics Command, Kelly Air Force Base, Texas. 

Sbepberd. W. T., Jobnson, W. B., Drury, C'. G., Taylor, J. C., & Beringer, D. (1991). Human factors 

in avialion maintenance, phase I: Progress report. DOT/FAA/AM-91116, Office of Aviation 

Medicine, Washington, D. C. 

Spencer, F., Borgooovi, G., Roach, D., Schurma-., D., & Smilb, R. (1992a). Generic reliability 

assessment programs at airline maintenance and inspectitm facilities. Final Draft Report prepared for 

the FAA Technical Center, Atlantic City, New Jersey 

Spencer, F., Borgonovi, G., Roach, D., Sclrurman, D., & Smith, R. (1992b). froposed reliability 

assessment experiment for eddy current inspection of lap splice joints in airline maintenance and 

inspection facilities. Fmal Draft Report prepared for the F/ A Technical Center, Atlantic City, New 

Jersey. 

Summers, R. H. (1984). Nondestructive inspection: Improved capabilities of technicians: Final Report. 

AFHRL-'IP-83-63, Training Systems Division, Air Force Human Resources Laboratory, Lowry Air 

·Force Base, Colorado. 

Thackray, R. L, Jones, K. N., & Touchstone, R. M (1973). Self-estimat~ of distractibility as related to 

performance on a task requiring sustained attention. Ergonomics, 16, 141-152. 

'Ibacb'ay, R. 1, Jones, K. N., & Touchstone, R. M (1974). Personality and physiological correlates of 

performance dec:remi:llt on a monotonous task requiring sustained attention. British Joumal of 

Psychology, 65, 351-358. 

Thackray, R. L & Touchstone, R. M (1980). An El:ploratory Investigation of Various Assessment 

Instruments as Correlates of Comple:A: VISUal Monitoring Performance. FAA-AM-80-17, Office of 

Aviation Medicine, Wasbington, D. C. 

Thackray, R. L & Toucllstone, R. M (1981). Age-Related Differences in Comple:A: Monitoring 

Performance. FAA-AM-81-12, Office of Aviation Medicine, Washington, D. C. 

Triggs. T. J., RaDkin, W. L, Badalamente, R. V., & Spanner, J. C. (1986). Human reliability impact on 

inseTvice inspectiorL VoL 2. Review and arudysis of human performance in nondestructive testing 

( emphasiZ..1g ultrasonics). "f!JREG/CR-4436-V2, B&tteDe Human Affairs Researcb Centers, Prepared 

for U.S. Nuclear Regulatory Commission. 

W!lll& M_ 1_ & Drury. c_ G_ (1989). A metbQ<I of evaluating inspector's performance differences and 

job requirements. AppiWf Ergonomics, Z0.5, 181-190. 

Wiener. E. L (1975}. Individual ana group differences in inspection_ In Drury, C. G. Wid Fox. J. G_ 

(Eds.), Human reliability in quality control. New York: Taylor and Francis. 

72 
Oapfer Five 

Invesdpdon of ErgoDomic: Factors Related to Postw'e 

IIDd Fatigue in the lospedion Environment 

5.0 INTRODUCDON 

In aim'aft inspertioo lllll mal!mwnre tasks, cme of tbe IIIOilt ooticeable devialioos from ezgooomically 

OJfinmm roncJitious Js 1blt tasks must be peafonued in restricted spaces wblch force awkward posmres. 

I.iterldute revJewed dmil:l& l'l1llle m lllfllcates 1bat tasks wblch possess exressive postural demands (Le., 

cmuped posftioDs, m~li•• ,.,. e of awkward pootures) can );n'llluce fatigue and ultimately affect both 

pedi•m•.,• aDd well-bciDg (e.g., Corlett, 1983; Cor1ett and Bisbop, 1978; Hunting, et al., 1980; Van 

Wely, 1970; We:!!fgUnlllld Ainu, 1984). 1be project repoiled bere came from a task statemeot tD 

propose a JIJil!hrdology tD SIDdy e:iCileiDe spadal cootfitions, aeatlld by restrictive or confined spaces, and 

1beir effect on lpnnan pDIItute, pedi.Y4"!1i!iC'J\ aDd sttas. 

llepewleDt upon tile 11a of awJQtion, JeSI•IcU:d 01' oo.ofiDed spaces have been defined in a variety of 

ways. FOI' our purpoa;s, 1 at«k'the q.:e wBl be clt.fimd as any area in wbi<il 111e spalial COIIditioDs 

result in deer s in pafi• '""" ,. or , .. , 111 ill ope&IIIOI ;wr!doad, Slress, or fatigue. Coufined spaces 

are IIOl1Dilly 1111or.lal!ld wi1ll .m ': bOOy lellldclions wbi<il oceur when an qx"SVOI' must eater an 

intervealing 1lllUCIUre to P' fiM m a 1Uk {e.g., ClrJO bold), lbus aeatiDg a situation in ~ 111e entire body 

is w::diDed to a ap:cHic: area. HoweY«, Rllll'k:thle 11p1K:iJ1 a aJso aeated in areas wb:re tile Jilysiea1 

space Js u>Hmited, but tile '""'wll• wort1ug aea Js resttided 'lbese partial-body restticUoDs result in 

limited movem:11t of a sp:cHic body pt; tor """''Ilk:, tasks aided by access devices (e.g., stepS, 

scafCOlcliDg. tb&tnktern) CIIIIC 1ow:r Jimb resttk:tion. for 1be feet must reside witbin a limited area. 

Odie£ ., ... , .... Jaclucle •u '"'• IIDifl 1brouJb access boles llld positioning various body parts in and 

lii.OOIId fixed liraaft ., MiipO" I!!• {e.g., 'riewhlj iDslde a IIIDIIl access panel). 'lbese partial-body 

ICSIIictloos may occur ill K.didoa to wbole body resttfl:doos, as in interior inspection of 1be tail 

compidweid. wblch """"!!C's dllllbe IJISllel "* climb 111t0 1be area {Wbole-body resldclion), as wen as 

place tbeir beld llid IDDJ 1brougll i&WW COIIfill:s to ~ OOi!ipO.Delllli (padial-body esuictiOD). 

A model is ofl'ered to guide • <il Ia tbe de* d&ICion ..t pl"edidion of tbe effccls of esuictive spaces 

and !be asrod.., .PD'"' .. :ol, ....,....~ ..tlttess drcc:ls on &O'i•mance and workload. Olltidelislics of 

tbe emhm"''""' op•••· 811dtlllk wbil:h let to cl:fine i2le ~ of spaces are Jden!ifleA 1be 

objectives of c:mHIMiinl rem dl 11e to eumtftetbeope&IIIOI compensatloDS forced byfflllictioD, and their 

plfljjj* e1Ject on palin•··~ llld w~ to c1ew:1op tedlnlqaes tor mmming and al1evialiag tbe 

res!ricliVCIICIII of ..--a: l!ld to cboooilll!tle tbe use of tbese fe<:lmiqoiCS 

5.1 RES'l'RlCfiYE SPACE MODEL 

Tile Rattk:tiw Sp.:e lillldel (Pipre 5.1) M'"''41ll to s, rt:ml!dca11y df*71be space, Ia terms of iDputl, 

or factois. wbk:h ddiDe a physlc:al or perceived spa;:e, and outpi.IIS wbidl anow tbe effeciS of space to be 

understood and (ll'edlctl'd 

73 
Reatrlctlve Spece F80tara 

Envlroliblent 

ODerator 

T811k 

74 

... ·.~ 
- ···- ... ..-, 

5.2 RESTRICTIVJ: SPACE FACTORS 

Key factors posed by fi:!e task, environment, and operator which cause restriction and/or extreme posi:UreS 

have been identified and compiled (Table 5.1). This compilation of factors is not an exhaustive list and 

may be expanded during on-going investigation. 

Table 5.1 Restrictive Space Factors 

TASK ENVIRONMENT OPERATOR 

Demands/Requirements Affordances Age 

Duration Area/Volume Body Size 

Equipment/Tooting Ughting Experience 

Perceived Value Number of People (acquaintance leva!, Flexilility 

gender, status level) Personality 

Surface Concfdion 

Resources 

TeqMIRiture 

Ventilation 

5.2.1 The Task 

The aircraft maintenance/"mspection tas1c delfUliUislrefluirements logically define performance in resttictive 

spaces. Research performed during Phase I produced a generic task description wbicb hv!!cates the 

primary task demands involved In aircraft inspection (Shepherd, et al., 1991). Each of the primary task 

components will be discussed below in relation to rescrlcdve space considerations, with the excepdon of 

Buyback Inspection. Althongb Buyback Inspection poses restrictive coocems, they are not unique from 

those to be considered during the primary inspection functions (ie., search and decision-making) and thus 

will not be discussed illllqJendently. 

5.2.1.1 Initiate 

Before the inspection task even begins, the perceived value of a task may affect the tolerance to the space 

conditions. In geoeral, if the operator does not value the job, cursory performance may occur, so that the 

operator can get out of the space quickly. Most tasks exbibit a speed/accuracy tradeoff (SATO), wilb 

faster performance increasing emJr probability. However, if the cost of mistakes is high, sucb as in 

aviation maintenance and inspection, pedormance is more deh"berate. Furtbermore, Shepherd. et al. (1991) 

indicates that inspectors are highly motivated to perform accurately, but a reduction of adverse 

environmental effects will belp ensure that accuracy is oever traded for speed. 

5.2.1.2 

Access tasks consist of physlcally readring the area to be inspected AU of these activities involve 

controlling the movement of the body or body part(s) within. a restrictive space. In aircraft 

mahuenanrefmspeclion, this may be an 1maided human task {e.g., area inspection of lower filselage skin), 

75 
Chllpler Five 

aided by access devices (e.g., steps, scaffolding, cbenyplckers), or require access tbrough an intervening 

structure (e.g., inspection of wing fuel tank interiors through access boles). 

Space bas been found to be a critical parameter in the mathematical modeling of movement control. In 

many instances, the amount of space defines the accuracy requiremeDIS of a task, which may dictate the 

speed of performance Numerous investigations have found a speed/accuracy tradeoff in human 

performance; as accuracy requirements are increased (i.e., decreased space), performance becomes slower. 

Mathematical models have been developed which accurately describe the relationship between space and 

both discrete movement lime (e.g., WickeDs, 1992) and conlinuous movement time (e.g., Bottoms, 1982; 

Drury. et al., 1987). Disaete movement involves moving from one location to another without having to 

consider the path of movement, while the path of movement is critical in conlinuous movement which 

requires moving accurarely betwee8 two boullllaries without e:raw!ing a boundary. These models may 

be useful in describing and predicting the effects of restriction on movement control tasks in aviation 

maintenance and inspection. 

For example. moving the hand to an access hole may be modeled as a discrete control task. while moving 

the hand tbrough the access hole is a continuous motor control task, with performance time predicted 

based upon the accuracy requiied (i.e., the size of the access bole). Further changes in performance may 

be found dependeDt upon the posture adopled while the body part is restricted Wiker. Langolf, and 

Chaffin (1989) reviewed research which indicated that there are only minimal differences in manual 

performance for work belgbts up to shoulder level. However, they found position and movement 

performance to decrease pogressively wbell bands were poS"..Jred above sbou1der level, due to the 

production of movement with pretensed muscles which may serve to increase tremor and decrease 

maximum velocities. 

Likewise, tasks in which the wbole body is moved tbrough an access bole may also be modeled as 

colllinuous control tasks. Resnicted entries and exits have been found to affect ingress and egress times 

(Drury, 1985; Krenek and Purswell, 1972; Roebuck and Levedahl, 1961 ). as well as subjective assessments 

of accessibility (Bottoms, et al., 1979). 

These models indicate that the speed chosen by an Inspector inaea:ses until some limiting speed is 

reached 1be point at which increases in space no longer result in performance being affected is the 

performonce boundary (Drury, 1985). However, desiguing to this boundary does not ensure that increased 

operator stress, fatigue, or workload does not occur. 

5.2.1.3 

Search requires the senstng, perceiving, and attending to information. Visual search requires the head to 

be at a certain location to control the eyes and visual angle. Thus, restricted areas frequently force 

inspectors to adopt awkwant bead. neck and back angles which induce stress and fatigue. In many 

instances, inspectors are forced to eitller search an area at less-than-optimum viewing angles or indiJecdy 

using a mirror. Although bolh methods can be utilized to produce acceptable performance, inspector 

workload and stress are inaeased, and perfonnance is less efficient. These restricted space situations can 

occur fn completely c:onfiDi:d areas (Le., in an interval structure) or in an area in which tile space is 

physically lllllimlted, but tile !1111!1fdlate working space is restricted by the task demands (e.g., wing 

inspection). 

76 
lnvestigatibn of Ergonomic Factors Rellded to Posture and FlltigiH 

Manual tactile inspection and non-destructive inspection (NDI) techniques, such as Eddy Current or 

Ultrasonic, require precise motor control on the surface to be inspected. In other words, the task demands 

are restricting the movement control. In addition, the tooling and equipment associated with Eddy Current 

and Ultrasonic inspection can physically restrict the area. The motor control models discussed above can 

be related to these situalioru:. Specifica1ly, these models predict that motor control tasks will be performed 

less efficiently (i.e., speed and accuracy), as the space conditions and postures demanded become more 

extreme. 

5.2.1.4 Decision-Making 

Decision-making requires that potential defects located during search be evaluated to decide whether it 

should be reported based upon specified standards. Comparison standards, which allow direct comparison 

of the potential defect with a standard at the point of inspection, have been found to improve 

decision-making (Galaxy Scientific Corporation, 1992). However, restricted areas may prohibit any 

extraneous material from being easily accessible in the immediate working area (e.g., workca."ll 

illustration), thus forcing decisions to be made without comparison standards (increased memory load), 

or additional time to obtain information from the workcard (fairly rapid task), a manual (a longer task), 

or a supervising individual. Moreover, as described earlier, viewing angles may be less-than-optimum. 

further decreasing sensitivity and increasing the difficulty of decisions. Thus, restricted spaces can force 

the decision-making task to be more memory-intensive, longer, and more difficult. 

Conversely, pressures for cursory decision-making may occur, so that the operator can get out of the space 

quickly. Decision-making tasks exhibit a speed/accuracy tradeoff (SATO), with speeded performance 

associated with inaccurate decision-making However, inspectors are highly motivated to perform 

accurately (Shepherd, et al., 1991), thus it is predicted that accurate decision-making performance would 

not be compromised by even 1lle most extreme of space conditions, although the workload and stress may 

increase. 

5.2.1.5 Respond 

The respond task demands that detected defects be marked and documented. As discussed above, 

restricted areas may not allow additional material such as non-routine repair forms in the workspACe. 

Thus, the inspector must remember all defects within an area until they are later documented on the 

appmpriate forms. This situation can create a high memory load on inspectors and presents the potential 

for an inspector to forget to note a defect. 

5.2.1.6 Repair 

Many repair tasks require mechanics to be in a confined or restricted area for prolonged periods of time. 

Task duration, which forces longec periods of time in a !estrictive area, could psychologically affect the 

perception of space. Habitability literature, concerr A:! with the study of manned underwater vessels and 

space vehicles, indicates that internal space requirements vary as a function of duration (Blair, 1969; Price 

and Parker, 1971). Furthermore, Cameron (1973) indicates duration to be the primary variable associated 

with fatigue effects. 

77 
Chapter Five 

In addition. eXIreme space conditions only allow a limited number of inefficient postures to be adopted, 

thus physical working car>acity may be reduced in restrictive spaces, as indicated by research in tbe area 

of manual matedal handling (Davis and Ridd, 1981; Mital, 1986; Ridd, 1985; Rubin and Thompson. 1981; 

Stalhammer, et al., 1986). Under unlimited space conditions, operators are able to adopt efficient postures 

or switch postures and use other muscle groups, enabling primary muscle groups to be rested (Drury, 

1985). However, frequent brel!h from restrictive areas, common during maintenance/inspection activities, 

allow relief from sustained task performance and allow tbe primary muscle groups to be rested. 

5.2.2 The Envirodlllent 

The physical volume of space obviously alters the workplace. A majority of the research in this area has 

focused on investigating the effect of the amount of space on task performance and was discussed above 

in Section 5.2.1. 

Ughting (lfld surface condition may create extreme spatial conditions. For example, poor lighting can 

demand a certain posture to be adopted for task performance, by forcing a specific visual angle. An oily 

surface can act in much tbe same manner, by limiting the postures which an operator is willing to adopt 

to avoid oil-soaked clothing. Otber variables may act to exacerbate the perception of a restrictive 

environment (e.g., ex/i'eme temperatures, poor ventilation). 

Conversely, otber environmental characteristics may moderate the effects of a space, such as restrictions 

which provide ajfordances (i.e., support). For example, Davis and Ridd (1981), Ridd (1985), and Rubin 

and Thompson (1981) found tbat when restrictions acted as supports for manual material handling in 

restricted spaces, lifting capacity increased. Thus, given a restricted situation, interesting interactions may 

exist, for task performance may be aided by some restrictions and degraded by otbers. 

Social aspects of the environment may limit space. As the number of people within a given area increases, 

the amount of space for a single person decreases. Although a majority of the inspection work is 

performed by a single individual (Shepheld. et al., 1991 ), many maintenance tasks require more tban one 

person. If uncomfortably close spacing is required between individuals, tolerance to the environment may 

be limited. In addition, the acquaintance level, gender, and status level of individuals within the 

environment may mediate Ibis response (little, 1965). For example, a mechanic may experience a more 

intense reaction if an inspector is within the restricted space during task performance. If there are many 

individuals within the same area, performing the same tasks, the available resources may become limited, 

the space may be perceived to be more restrictive and people may become frustrated (e.g., specialized 

tooling not available, thus making the task more difficult). 

5.2.3 The Operator 

Body size may act to limit the amount of physical space, which in tum may increase tbe restriction. 

Roebuck and Levedabl (1961) found body dimensions to be somewhat predictive in the analysis of aircraft 

escape times tbtough restrictive door and window exits. Body dimensions may also indirectly affect 

postute, for smaller individuals may be able to adopt postures more conducive to space reduction. 

Restrictive spaces may force individuals to adopt unnatural postures; thus, smaller individuals may be 

more able to do Ibis. Bodily flexibility may also be associated with the ability to adopt unnatural postures 

caused by restricted spaces. 

78 
InJ1Uiigtltion of Ergonomic Foeton ReloWl Ill Posture tmd Fllllgru 

Age has been found to have an effect on task performance, primarily due to a deterioration in the pllysical 

and cognitive function of older individuals. However, this effect may be reversed wllen experience is 

important (Czaja and Drury, 1981). These effects may be particularly relevant in aviation inspection, since 

most inspectors are senior personnel. 

Experience, or familiarity with a situation, may act to moderate the stress response. Previous exposures, 

practice, or conditioning may rednce uncertainty, or influence the perceived dellill!lds, constraints, and 

strategy selections (Sutherland and Cooper, 1988}. Personal communication with inspectors has revealed 

that repeated exposures, as well as attitude, reduced the stress response during whole-body restrictions. 

Enduring personality characteristics and cognitive style do have an effect on some subtasks demanded 

during maintenance and inspection performance. Historically, there have been attempts to select personnel 

based upon personality scales and aptitude tests L'lought to be relevant to v3rious jobs. However, Wiener 

(1975) indicates that most of these effom have not been ftuitful and endorses job design, training, and 

motivation as better alternatives. 

5.3 PHYSICAL AND PERCEIVED SPACES 

The above factors can directly affect the spatial conditions. The workspace has physical characteristics 

which can be easily defined and investigated, but the pllysical space is also perceived by the operator. 

Thus, the effective workspace is partially created by pbysical elements and partially by perceived elements. 

Thus, the effective workspace within a fixed physical space is not necessarily constant but is dependent 

upon an individual's constantly-changing perceptions. The effects of this effective space must be inferred, 

as direct observation is not logically possible. 

5.4 STRESS 

It is logical to model these restrictive space effects within a traditional stress framework, where the 

extreme space conditions act as a stressor. Context-dependent examination of the space-affecting factors 

allows the specific stress-inducing situation to be defined. so that the subjects' perceptions may be 

determined to assist in interpreting behavior (Meister, 1981). Thus, field investigation is important for 

understanding the specific response to restricted spaces in aircraft maintenancermspection activities. 

However, controlled laboratory studies allow more precise data to be collected without disrupting the 

actual maintenancefmspection activities. Therefore, both field and laboratory studies will be needed to 

understand the effects of restricted space. In an effort to operationally define stress within the context of 

restrictive space, the following definitions will be employed (Alluisi, 1982; Pratt and Barling, 1988): 

Stressor - 1be environmental, operator, and task characteristics which comprise tile space and 

impinge on the individual. In this context. the physical and perceived spaces are the stressors. 

Stress- A state within the individual cansed by the perceived magnitude of the stressor. The 

existence and interaction of the various envi.romnental, operator, and task characteristics will 

dictate the intensity of the stress. 

Task performance in restrictive spaces normally includes both physical and cognitive demands; the stress 

induced by these demands will be differentiated w more clearly define and understand the various stress 

79 

' 

.I 
Chapter Fille 

responses. Physical stress is directly perceived by the involved physical subsystems Within tbe individual 

(e.g., biomechanical, physiological) due to a discrepancy between the environmentalltask demands and the 

individual's physical ability to meet the demands. It is perceived by an individual through a specific, or 

localized, experience of discomfort. Thus, response can be specifically aimed at eliminating, or 

alleviating, the stressor when possible. There Will also he an overall physiological response to bodily 

requirements caused by the restriction. For example, restriction may cause pcs+'..uriil :;tress and discomfort 

in various muscle groups, which results in increases in heart rate and blood pressure ( Astrand and Rodahl, 

1986). 

Cognitive stress creates a cognitive state resulting from an individual's perception of the discrepancy 

between the perceived environmental/task demands and their perceived ability to meet those demands 

(Cox, 1990, 1985). It is this mismatch which eventually determines the stress reaction, thus tbe operator 

perceptions play a key role. This stress is experienced as negative emotion and unpleasantness (Cox, 

1985; Sutherland and Cooper, 1988), and may be difficult to localize. 

It is hypothesized that whole-body confinements, as opposed to partial-body restrictions. are more apt to 

produce cognitive stress effects. Inspectors may feel that they have less control to adapt, or adapt to, the 

perceived space. For example, when totally enclosed Within an area, there may be fewer opportunities 

to eliminate the stressor (e.g., frequent rest breaks outside the space). Both whole-body and partial-body 

restrictions are hypothesized to cause physical stress effects, particularly postural, due to the body positions 

which are demanded. However, these physical stress effects Will most likely lead to cognitive stress 

effects, if task completion is compromised. In summary, the effects of stress on human performance 

provide the basis for investigation. These effects include increased arousal, increased processing speed. 

reductions in working memory, reduced attentional capacity and attentional narroWing, and changes in the 

speed and accuracy of performance (Hockey and Hamilton, 1983; Hockey, 1986; Reynolds and Drury, 

1992; Wickens, 1992). 

5.5 FATIGUE 

As discussed above, task performance under extreme spatial conditions can present both physical and 

cognitive stress, which in tum can induce physical or cognitive fatigue. Physical fatigue may be defined 

as a state of reduced physical capacity (Kroemer, et al., 1990). Work can no longer be continued because 

tbe involved physical subsystemS are not capable of performing the necessary functions. For example, 

a posture can no longer be maintained due to exceeding tbe endurance limit of the muscles (Rohmert, 

1973). 

Cognitive fatigue is a term normally associated with stress and may be broadly defined as a generalized 

response to stress over time. Tile effects may reside as a psychological state within the individual or 

extend to affect performance. Symptoms of fatigue include restricted field of attention, slowed or 

impaired perception, decreased motivation, subjective feelings of fatigue and task aversion, and decreased 

performance in the form of irregularities in timing, speed, and accuracy (Bartlett, 1953; Grandjean and 

Kogi. 1971). 

80 
5.6 OPERATOR RESPONSE 

'lbe operatOr response is a function of the pm:eived space. and the associated stress and fatigue effects. 

In most instances, this response cannot be desa:ibed by one variable but is manifested in various 

physiological, psychophysical and bebavioral pat" • us. 

An individual may respond to, or cope with, a stressful silllation in order to lessen tbe effect of. or 

eliminate, the SIIessot (Cox, 1985). A dependency may exist between the different modes of response 

(ie., psychophysical, physiological and behavioral). Any mode(s) of response may in tum elicit anothec 

mode(s) of response {Meister, 1981). For example. while pert"orming maintenanre or illspection in a 

cramped area of an aircraft, tbere may be an initial physiological response to the postwal demands such 

as lack of blood flow to the !eg muscles, which in tum causes a behavioral response (e.g., posture shlf"ting) 

andfor subjective response (e.g., perceived discomfort). In addition, in the context of restrictive space. a 

response may alleviate one component of the stress response, while causing anotber. Continuing the 

example, a change in posture may reduce the physiological response, but the new posture may make the 

task more difficult to paform, causing feelings of frustration. 

5.7 EFFECTS ON OPERATOR 

In order to descn"be, or possibly predict. the effects of oper.mr response on pen01 mane"' and workload, 

tbere is a need to understand tbe effects of stress and fatigue on the opaator. These effects were cited 

previously in tbeir respective sections (Sections 5.4 and 5.5). If pedi:u mance is affected, a specification 

of the affected subsystem and why it is affected may be possible. For example, perception may be 

affected by the inability to obtain an adequate visual angle, attention may be distracted by discomfort due 

to postural stress, or decision-nlakblg may be speetkd up in an efi'ort to finish the task and eliminate tbe 

SIIessot (i.e., leave the environment). 

5.8 A RESTRICTIVE SPACE FRAMEWORK TO MEASURE THE EFFECfS ON 

PERFORMANCE/WORKLOAD 

Performanre and workload will ultimalely be affected by any changes in opelaiOr function forced by the 

spatial conditions and as..<ueiated stress and fatigue. Drury (1985) advances a 3-level framework which 

atteq>ts to describe task performance with respect to physical space. 'lbe following proposed framework 

includes an additional zone to better predict the effects of space and awkward postures on inspector stress 

;md wo:ldoad as well as pefi()11IIanre 'Ibis framework presents four zones which specifically define 

performance, workload, and stress (Table 5.2). 

81 
Chapter Five 

Table 5.2 Pedi .onnance. (![ WI cuve 

ZONE PERFORMANCE WORKLOAD STRESS 

0 None possible WsO S=O 

1 Proportional to space w D~+mt • •to~ >HOC 

2 Acceptable w __ 

tair. + CC&i4* 1-n(a) 

0 talk+.,.... .... to~> HOC 

3 Acceptable i 7 (II} 5 

w_ D-<HOC 

5.8.1 Zone 0 • Anthropometrk:a Restricted Zone 

The task cannot be accomplisbed. as tile space rondilions, or postureS. are too extreme for tile operator 

to function. The boundary between zone 0 and zone 1 is llOOilally determinffl by antbropomettic data 

(i.e., human dimensions). These minimum criteria are only used if space is a critical commodity (e.g., 

aircraft). Under normal conditions, largex spaces are rerommended The limjtatjons in using this type of 

data are that it is normally based on static sitling/standing and does not account for IlOIIlllll working 

postures, does not include any allowance for special equipment, and rep.esents a you..--g population. 

Hence, anthropometrically.defiDIX!spacesmustunderestimateminimumspacerequi!ements(Drucy,l985). 

There are computer-aided systemS, such as CREWCHIEF (McDaniel and Hofmann 1990) which account 

for some of these limitations. However, one llliiiili1'actu, which has developed and utilizes a similar 

computer-aided human modeling system, admits that, 

... [these] systems [Dave} limits, andsomemock-upsstill will be required. "Humanmodels.. .. can't 

do all tbe interlace work," ... 

Nevertbeless. even if these 'minimum allowance models' could ensure that individllals can wert in a given 

spaca, tiley do not account for fatigue, workload. or sttess effects 

5.8.2 Zone 1 • Perfomumce Restricted Zone 

Task performance is possible, but pelformance is not optimum !Jecanse lbe spatial conditions/posture still 

intexfere with tbe task. This zone ranges from allowable access for task performance up to acceptable task 

pertimnance. As tbe space increases. perloonance increases. The total worldoad is~ to lbe workload 

associated with tbe task pins tbe workload associated with the operator compensations caused ~y the 

workspace. Similarly, there is increased sttess present in this zone, for the task demands exceed the 

operntor capabilities. Workload and sttess most likely decrease within the zooe, because as the spatial 

demands decrease. the compensatiOns should deaease. 

5.8.3 Zone 2 • Worldoad/Stress Restricted Zone 

Task pext(\Tli!artre is acceptable, at least in the sbort term, but operatOrs' workload and~ are increased 

because of compensati.llg for the limited space and/or extreme postures. As space increases within this 

zone, operator compensation(s) or responses should deaease, thus causing the total workload and stress 

to decrease. 

82 
5.8.4 Zone 3 - Unrestricted Zone 

This zone allows acceptable task perfonnance without additional operator compensation; thus. tbere is no 

additional workload or stress imposed by 1be spatial conditions. 

5.9 RESTRICTIVE SPACE METHODOLOGY 

Expetimentation will utilize 1be restrictive space model to assist in undei:stlmding and describing 1be 

relationships between 1be spatial conditions and 1be operator compeosations, faligue, stress. and ultimately 

per:M n•.mre and woddoad. The restrictive space framework will be used to guide 1be categorization of 

restrictive spaces and descnDe 1be effects on stress. workload, and pes:fUI:mance This research will include 

field investigation in conjuDction wilh a series of labor.ttory experimen!s to investigate 1be effects of 

restrictive space on visual inspection perfonnanre. wbich accounts for 90 pem:m of an inspection 

activities in airaaft inspection (Sbepbenl, et al., 1991). Ex1ensions to NDT inspection, wmdl mvolves 

lhe additional restriction of worldng wilh equipment, are possible at a late£ date. 

Knowledge of 1be effect of awkwaid postures and restrictive spaces on 1be human opeiatOI, reviewed in 

1be previous secf..ons, will be applied wilhin lhe following melhodology to give: 

1. A recognition guide wbidl allows users to predict wbidl tasks will bave a pes:fonnanre 

decrement and/or stress inc.rease due to tbe spatiallpostura demands 

2. A set of inte:ventions, keyed to task, operator, and environmental factors. wbicb will reduce 

1be spati2! demands and operator workload. stress, and fatigue. 

5.10 ON-SJTE EVALUATION 

5.10.1 Task Description 

The task analysis J:rocedure developed during Fbase I {Sbepbeid. et aL. 1991) will be adapted and applied 

for use in assessing restrictive spaces Detailed desaiptions of a represe!!lative sample of tasks wbich 

possess restrictions and awkwaro postures will be obtained. This step will include baving human faclms 

analysts WOik wilh inspectors dming 1be completion of worlccards. While oht2ining task descr!:plions, 

emphasis will be placed on dncumerong environmental, operator, and task factors identified ill 1be 

previous section wbidl aeate, or exacerbate, restricted spaces or extteme postnres. 

5.19.2 Bebavioral Measun!S 

Extreme spatial conditions can limit 1be munher of posiUreS adopted or furce nnnatnral postnres. An 

adapted version of Branton and Grayson's (1967} postural recording scheme will be 1lh1ired to measure 

whole body postnres. The number of postures adopted and 1be frequency of ead1 postnre will be obtained. 

These measmes bave been successfully applied to 1be ass: SJ•eut of postural demands in varions wad 

tasks (Bhatnager, et al., 1985; Branton and Giayson, 1967; Zhang, et aL. 1991) o1ber than airuaft 

inspection. 

83 
5.103 Psydlopbysical Measures 

Pbysi.ological monitoring. wbid:l presents many difflcnffies and limitations, will be Jjmjted to tbe 

laboratory, tlms an e:rnplmis will be placed on •lhlizing psydlophysica11edmiqnes in field SUJdie<: These 

teclmiqlles are atttactive. partiallarly fix field use,. fur tbey m:e unresttiUive. require minimal 

insii••n eattation, and 1bDs easy to useladminisla. and give valid and reliable - · · ' whim e-m be related 

to otller non-aviation tasks.. 

Feeliw Tooe Cb?cklist (FTC}, "Ibis scale 11-ill be J!hljzed to measure fatigue effects over time. It is an 

interval scale wbid:l has been found to be a valid and reliable measure of subjective fa:lings of fatigue 

(Pearson. 1957). 

Bodv Part Discomfol.t Chart {BPD). This is tbe most DOled tedmiqlle t!hli'rei! to obWn fKJSWlal discomfort 

data (Corlett and Bishop 1976). This chart C2legOriz.es the body into a nmnber of functional areas to allow 

tbe assessznent of individnai body areas. A 5-paint oolimll scale will be ut>ljzed to solicit operorors' BPD 

ratings. 

NASA - Task Lead Index (1LX)_ This is a multi-dimensional rating scale 'll<11idl measiJreS six 

workload-related factors (e.g.., mental demand, Jilyskal <kroand, tempOral tJemand, paformanre., effort. 

and frusttation) and their associa!Prl magnitudes to form a sensitive and diagnoslic WO!kload measure (Han 

and Staveland, 1988). 

A tepresenll!!h-e sample of ailmft insredian tasks. which include bolh wbole-body and panial-body 

resiiictio1lS. will be srl! 1M fur fieki investigation. Postma! data will be collected tlln:Jugbout task 

pe:di 11 manre 1be FrC and BPD will be ;ytminjlffl:ed before, during and afu:r task parmmanre Ideally. 

tbe same jnspectoc; will be COmpaled across tasis; aJtbough. this may DOt always be possible dne to tbe 

sdJednling demands on tbe bangar floor. In addillon. tbe n.x will be administered after task 

petfuunaocg 

5.11 LABORATORY EVALUATION 

5.11.1 Experimems 

E.xpelimentatjoo will involve a series of studies in\'eS!igating single and multiple wbole-body restti.."'tiOilS. 

Investi.galion will fOOlS on examjnjng the effect of spatial resttictiO!llextteme tKJS~:Wes on pe:rformaDce, 

woc.kioad, stress. and fatigue. These experiments will focus on tbe effects of restrictions and their 

iD1etaclions in three planes: side-to-side (latel:al), bead-to-feet (vertical), and front-to-back (sagittal) 

resttictions. Eqrrimenmtion will be driven by the restrictive space framew(rt. to demonstrate tbe various 

resttictiw space zooes. Based upon this data. predictions can be made of tile effects of various spatial 

conditions on paf01manre. work:1oad. sttess. and fatigue. 

84 
l11111!Stigation of Ergonomic Ftu:lors Rellded to Posture and Fatigue 

5.11.2 Tasks 

An aircraft inspection task Will be used to simulate the inspection environment during laboratory 

investigation. In addition, a neutral inspection task will be nttlizffi to provide more easily-interpreted 

results, shorter training time, and more sensitive measures of search and decision-making. Both tasks are 

computer-based. 

Aircraft Inspection Task. The visual inspection task is simulawlon a SUN SPARC Station 1 Workstation. 

The task requires the inspector to search for multiple defects ftequently found on an aircraft, including 

missing~ damaged, pooched/dished,. and loose rivets, dents, and rivet cracks. The defects may be classified 

as critical or noncritical, dependent on the severity of the defect. 

This simulator includes a windowing function (Galaxy Scientific Corporation, 1992), which results in only 

a small area being folly illmninatffi, within a large inspection field. Only within this window can faults 

be detected and indicated. The entire inspection field is viewed by successive movements of this window. 

This windowing function forces what are known as field of view (FOV) movements (Drury, in press). This 

will allow the search strategy process measures described in Section 5.11.4 (e.g., fixation time, sequential 

distribution of fixation, etc.) fD be collected. This is an attractive alternative for the measurement of eye 

movement parameters, in contrast tn conventional teclmiques which require sophisticawl and restricting 

instrumentation fD be attached fD the subject. 

Neutral Inspection Task. The experimental inspection task will include a random arrangement of 

background and target charactels (Barnes, 1984). The task allows the two primary components of 

inspection, search and decision making, tn be measured separately. The software will be adapted tn 

include an inspection window so that eye movement parameters may be obtained. 

s..;.1..3 Independent variables 

The current research will focus on investigating the effect of a subset of restrictions described in the 

previous section (Table 5.1). 

The Environment. The physical CITIUJunt of space will be altered in order to determine the effects of 

various restrictive environments. The ajfordance of the various restrictions {Le., support prov'.ded) will 

be changed indirectly through volume/area alterations and be dependent upon the experimental space 

conditions. For example, some restriction{s) will be extteme eliOUgh that theY allow subjects fD lean 

against them during task perfonnance. These behaviors will be noted. 

The Operator. To control for body size, anthropometric measurements wm be utilized tn standardize the 

amount of space to each subject (e.g.. space is equivalent tn percentage of various body measurements). 

Thus. cleamx:e colldit:ions will be equivalent for each subject. In an effort to obtain face validity, a 

sample teptesentative of the current inspector population will be selected. Age will be used as a covariate 

to control foe any possible age effects. The level of experience in tbe restricted space will be controlled 

by uttlizing a between-subjects expe>imental design which ensures that each group of subjects is only 

exposed tn one restrictive environment. 

85 
Chapter Fwe 

Task specific pretests wbich measure different cognitive styles/personalities may provide some predictive 

power and partially explain !be inberent variability between individuals so that !be results can be better 

understood. Four pretests, which are relevant to tbe task context and environmental conditions, will be 

utilized in this study: Emhe<lded FiguteS Test (EFT), Matching Familiar Figures Test (MfFI), Locus of 

Control (LC). and a clallstrofjlobia screening test. 

The Task. 1be iru.1JeC!ion tasks will allow two operator demands !3 be investigated: search and 

decision-making Each experimentation period will include ba.'!eline, task, and recovery periods. to be 

described more fully in tbe experimental procedure section below (Section 3.3). In add!tion, the effects 

during !be baseline, task and recovery periods will be measured over time (Le., duration). 

5.11.4 Dependent Variables 

Beha•iGilll.. An adapted version of Branton and Grayson's (1967) postm:aJ recording scheme ""ill be 

utilized to measure whole body postures. A computerized vernon of this sys!elll will be devel~ 

posture will be indirectly observed (ie., videotape), and positions directly input. Thus, a continuous 

record of all positions, their frequencies. and durations can re obtained. This gross assessment does not 

provide data on tbe magnitude of tbe posror?J deviations, only tllat poSlml!l changes occur. Thus, the 

specific magnitude of the trunk, neck, and head angles will also be measured for ~h oosture. The 

frequency of each posture. fueir duration, and the number of posture changes will be me2SUred and related 

to postural severity and discomfort (Bbatnager, et a!., 1985; Branton and Grayson, 1967; Drury, et al., 

1988; and Zhang, et al., 1991). 

Physiological. Heart rate and respiration rate will be obtained. 11lese measures were chosen for the 

following reasons: (1) they present minimal intrnsion on task pe:rfonnanre, and (2) tbey are sensitive to 

changes in Jilysical stress (e.g.. Astrand and Rodalll. 1986), oognitive stress {e.g.. Kak, 1981), and 

workload (e.g., O'Donnell andEggemeler, 1986}. As indicated earlier, physiological monitoring possesses 

many limitations. Restrictive environments ~ rodilional inberent diffirolties. However, a limited 

number of measures will be obtained in an attempt to capture this primary srress response. 

Psychophysical. In addition to the FI'C, BPD and TLX descri'bed in Sect:on 5.113, a modified version 

of the Stress-Arousal Checklist (MSACL) (Mackay, et al., 1978) W':U be tmlizffi to measure stress and 

arousal levels experienced in restrictive spaces (Cruickshank 1984). 

Task Performance Inspection is a two-stage jXOCesS which demands search and dec:sion-making. VJSUal 

search proceeds as a series of fixations at specific points in the visual search field. These fixations are 

separated by saccades which occur when an individual moves llisi!Jer eyes to a new location. Factors 

which affect search performance include search sttategy, speed/accuracy tradeoff (SATO), and stopping 

policy. 

Search strategy is defined by tile overall pattern of eye movements, in our case FOV movements. The 

following parameters will be measured: fixation time, spatial distribution of fixations, sequential 

distribution of fixations, and intelfixation distances. These subtle process measures may be sensitive to 

the fatigue and stress effects described previously. These effects may be exhibited by a change in tbe 

number or rate of fixations or a more random search path (Latorella. et al., 1992). 

86 
Investigation of Ergonomic Factors Related to Posture and F •. :igue 

Speed/Accuracy Tradeoff (SATO) can be assessed by the performance measures: search time taken to 

detect a fault, search errors (ie., failing to locate a fault), and stopping time (i.e., time taken to search for 

a defect before giving up). There is evidence to suggest that individua!s change their operating point, with 

respect to speed and accuracy, under various stressful conditions (Hockey, 1986). 

Decision-making is required if a defect is detected. This decision process can be modelled by signal 

detection theory (SDT), which describes bow humans detect signals in noise (Wickens, 1992). Within this 

SDT structure, three factors can affect decision-making: sensitivity, criterion, and SATO. 

Sensitivity is a measure of discriminability, the perceived difference between the observed flaw and 

standard, and may be affected by tbe extraneous noise introduced by restrictive environments. 

Decision Criterion is tbe internal standard chosen by an inspector for reporting a fault and can be affected 

by the defect rate, cost of errors, and time on task (Galaxy Scientific Corporation, 1992). Shifts in 

criterion may be found as time on task increases due to missed signals and corresponding changes in 

signal expectancy. Moreover, criterion changes have been found to be caused by stress-inducing situations 

(Wickens, 1992). 

SATO is the amount of time taken to make a decision and can affect sensitivity. In restrictive 

environments, signal integration may be affected by speeded performance. Research was reviewed earlier 

which indie&ted that stress can cause a strategic change in performance resulting in an increase in speed 

and errors (e.g., Hockey, 1986). 

The following measures will be obtained in order to assess changes in sensitivity, criterion, and SA TO: 

decision time (i.e., time to make decision, after defect detected), misses (i.e., deciding not to indicate a 

defect which is classified as defective) and false alarms (i.e., deciding to indicate a defect which is not 

classified as defective). 

5.11.5 Experimental Procedure 

Subjects will perform tt.e inspection task under unrestricted and restricted space conditions in order to 

measure changes in performance between the two conditions. The task periods will be segmented into 

several portions and separated by breaks, which is characteristic of the maintenance and inspection task 

organization. A conventional stress design will be employed, thus allowing baseline measures to be 

obtained and any aftereffects assessed 

Performance measures will be obtained during each task period. In addition, videotape analysis allows 

the frequency, duration, and severity of each posture, and the frequency of posture changes to be obtained 

continuously. The BPD, MSACL. and FrC will be administered at the beginning and end of each task 

period, while the TLX will be obtained at the end of each task period. The physiological measures will 

be obtained throughout the baseline, task and recovery periods. 

87 
Chapter Five 

5.12 ANALYSIS UF RESULTS 

Tne results of the on-site evaluations and laboratory experiments will be combined and analyzed to derive 

operational definitions of the zone boundaries. This will allow the recognition and prediction of tasks 

which will have performmce decrements and/or workload/stress increases due to restrictive spaces or 

extreme postures. Knowledge of human factors models of human inspection and the functioning of 

individnal human subsystems (i.e., senses, perception, attention, memory, decision-making, feedback, and 

conttol) can be utilized to identify the subsystems affected by the identified restrictions. 

The additional demands/compensations forced by restrictions can be determined and the effects predicted 

and described by the restrictive spare framework J;RSellted in Section 5.0. An1bropometric models, and 

subsequently population peJ"CeDtlles, will be utilized to quantify and operationally define these effects in 

terms of absolute space dimensions within this framework. 

5.13 DEVELOPMENT OF CHECKLIST/INTERVENTION GUIDE 

Based upon the results, a recognition checldist will be developed which classifies and describes the effects 

of restrictive spaces and extreme postures on inspection tasks into one or more zones. Procedures aimed 

at alleviating the reduced performance and increased workload/stress in Zones 1 and 2 will be devised and 

compiled. The task demands, and associated compensations forced by restrictions, can be compared with 

known human capabilities to provide interventions aimed at the identified environmental, operator, and 

task restrictive space factors in on:ler to reduce operator workload/stress and improve performance. Thf:se 

intervention strategies will be used in the development of a guide. 

5.14 REFERENCES 

ADuisi, E.A (1982). Stress and stressors, commonplace and otherwise. In E.A ADuisi, and E.A 

Fleishman (Ed.), HumaTi performance and productivity, Vol 3: Stress and performance effectiveness. 

Hillsdale, NJ.: Lawrence Erlbaum Associates. 

Astrand. P. and Rodabl, K. (1986). Textboolc of work physiology. New York: McGraw-Hill. 

Barnes, R.E. (1984). Inspection performance of mentally retarded persons. Unpublisbed doctoral 

dissertation. State University of New York: at Buffalo. 

Batiiett, F. (1953). Psychological criteria of fatigue. In W .F. Floyd and A. T. Welford (Eds.), Symposiwn 

on faligue. London: H.K. Lewis and Co. 

Bhatnager, V., Drury, C.G. and Schiro, S.G. (1985). Posture, postural discomfon. and performance. 

HU11Ullt Factors, 27(2), 189-200. 

Blair, W.C. (1969). Human factors in deep submergence vehicles. Marine Technology Society Journal. 

3,(5), 37-46. 

88 
lnvestiglltion of Ergonomic Facwrs Related to Posture and Fatigue 

Bottoms, OJ., Barber, T.S. and Chisholm, C.J. (1979). Improving access to the tractor cab: An 

experimental study. Joumal of Agricultural Engineering Research, 24, 267-284. 

Bottoms, D.J. (1982). The tractor driver's steering control taslc. Ergonomics, 25, 31-39. 

Branton, P., and Grayson, G. (1967). An evaluation of train seats by observation of sitting behavior. 

ErgoP.omics, 10, 35-51. 

Cameron, C. (1973). A theory of fatigue. Ergonomics, 16, 633-648. 

Corlett, E. N. (1983). Analysis and evaluation of working posture. In Kvalseth, T. 0. (Ed.), Ergonomics 

of workstation design. London: Butterworths. 

Corlett, E.N. and Bishop, R.P. (1976). A technique for assessing postural discomfort. Ergonomics, 19, 

175-182. 

Corlett, E.N. and Bishop, R.P. (1978). The ergonomics of spot welders. Applied Ergonomics, 9, 23-32. 

Cox, T. (1985). The nature and measurement of stress. Ergonomics, 28, 1155-1163. 

Cox, T. (1990). 1be rea>gDition and measuremeut of stress: Conceptual and methodological issues. In 

J.R. Wilson, and E.N. Corlett (Eds.), Evaluation of human work. London: Tay101' and Francis. 

Cruickshank, P J. (1984). A stress and arousal mood scale for low vocabulary subjects: A reworking of 

Mackay, et al., (1978). British Joumal of Psychology, 75, 89-94. 

Czaja, S:. and Drury, C. G. (1981). Aging and pretraining in industrial inspection. Human Factors, 23, 

473-483. 

Davis, P. R. and Ridd, I. E. (1981). The effect of headroom on acceptable lifting capacity. Ergonomics, 

24, 239. 

Drury, e.G. (1985). Infiuence of restricted space on manual materials handling. Ergonomics, 28, 

167-175. 

Drury, C.G. ('m press). Exploring search strategies in aircraft inspection. In D. Brogan (ed.), Visual 

semch (2nd ed.). London: Taylor and Francis. 

Drury, C.G., Goonetilleke, R.S., and Maurice, M. (1988). Automation, stress, and performance in 

industrial inspection. Final Report on PHS Grant 5 R010H024, Impact of Automation on Industrial 

Inspector Stress. 

Galaxy Scientific Corporation (1992) (in press). Human Factors in Aviation Maintenance Pf>.ase Two: 

Progress Report. 

89 
Chapter Fh>e 

Drury, C. G., Montazer, M.A and Karwan, M.H. (1987). Self-paced pall! control as an optimization task. 

Systems, Man, and Cybernetics, 17, 455-464. 

Grandjean, E., and Kogi, K. (1971). Introductory rellllii'ks. InK. Hashimoto, K. Kogi, and E. Grandjean 

(Eds.), Methodology in human fatigue assessment. London: Taylor and Francis. 

Hart, S.G, and Staveland, L.E. (1988). Development ofNASA-1LX: Results and empirical and theoretical 

research. In P.A. Hancock and N. Meshkati (Eds.), HwruJri mental wor/doad. North Holland: Elsevier 

Science Publishers. 

Hockey, G.RJ. (1986). Changes In opentor efficiency as a function of environmental stress, fatigue, and 

circadian rbytluns. In K.R. Boff (Ed.), Handbook of perception and human perfo171111711:e (Vol2). New 

York: Wiley and Sons. 

Hockey, G.R.J. and Hamllton, P. (1983). The cognitive patterning of stress states. L1 R. Hockey (Ed.), 

Stress and fatigue in human performance. New York, NY: John Wiley and Sons. 

Hunting, W., Grandjean, E. and Maeda, K. (1980). Constrained postures in accounting machine opeottors. 

Applied Ergonomics, 11, 145-149. 

Kak, A. V. (1981 ). Stress: An analysis of physiological assessment devices. In G. Salvendy and M.J. 

Smith (Eds.), Machine pacing and occupational stress. London: Taylor and Francis. 

Krenek, R. F. and Purswell, J. L. (1972). Automobile escape worthiness-an app:oach to a predictlve 

model. Proceedings of the HwruJri Factors Society's 16th Annual Meeting, 46-51. 

Kroemer, K.H.E., Kroemer, HJ. and Kroemer-Elbert, K.E. (1990). Engineering Physiology (2nd ed.). 

New York: Van Nostrand Reinhold. 

Latorella, K.A., Gramopadhye, A.K., Prabhu, P.V., Drury, C.G., Smiih, M.A. and Shanahan, D.E. (1992). 

Computer-simulated aircraft inspeclion tasks for off-line experimentation. Proceedings of the Human 

Factors Society's 36th Annual Meering, 92-96. 

Little, K. B. (1965). Personal space. JOU17llll of Experimental Social Psychology, 1, 237-247. 

Mackay, C., Cox, T., Buaows, G., Lazzerini, T. {1978). An inventory for the measurement of 

self-reported sttess and arousal British Jountal of Socilll and Clinical Psychology, 17, 283-284. 

McDaniel, J.W., and Hofmann, M.A. (1990). Computer-aided ergonomic design tools. In H.R. Booher 

(Ed.), MANPRINI': An approach to systems integration. New York: Van Nostrand Reinhold 

Meister, D. (1981}. The problem of stress definition. In G. Salvendy and M.J. Smith (Ed.), Machine 

pacing and occupational stress. London: Taylor and Francis. 

90 
lm•estigation of Ergonomic Factors Relllled to Postwe and Fatigue 

Mital, A., (1986). Subjective estimates of load carriage in confinal and open ~'paces. In W. Karwowski 

(Ed.), Tre1ids in ergonomics/human factors Ill. North Holland: Elsevier, 827-833. 

O'Donnell, R.D., and Eggemeier, F.T. (1986). Workload assessment methodology. In K.R. Boff (Ed.), 

Handbook of perception and human perfo111UJ11Ce (Vol. 2). New York: John Wiley and Sons. 

Pearson, R.G. (1957). Scale analysis of a fatigue checklist. Journal of Applied Psychology, 41, 186-191. 

Pratt. LJ., and Barling, J. (1988). Differing between daily events, acute and chronic stressors: a 

framework and its implications. In JJ. Hurrell, L.R. Mwphy, SL. Santer, and CL. Cooper (Eds.), 

Occupational stress. issues and tkvelopments in research. London: Taylor and Francis. 

Price, H. E. and Parker, J. F., Jr. (1971). Forecast of human factors technology issues and requirements 

for advanced aero-hydro-space systems. (Contract #N00014-69-C-0327). Arlington, VA: Office of 

Naval Research. 

Reynolds, J.L., and Drury, C.G. (1992}. The effects of physical exertion on task performance in modem 

manufacturing: A taxonomy, a review, and a model. Paper submitted for publication in Ergonomics. 

Ridd, I.E. (1985). Spatial restraints and intra-abdominal pres~ure. Ergonomics, 28, 149-166. 

Roebuck, J.A., and Levedahl, B.H. (1961). Airaaft ground emergency exit design considerations. Hwnan 

Factors, 3, 174-209. 

Rohmert, W. (1973). Problems in determining rest allowances. Applied Ergonomics, 4, 91-95. 

Rubin, T. and Thompson, S. J. (1981). The effect of restricted workspaces upon maximal exertions ·in 

·~ the sagittal plane. Ergonomics, 24, 240. 

Shepherd, W. T., Johnson, W. B., Drury, C. G., Taylor, J. C. and Berninger, D. (1991). Hwnan factors 

in aviation maintenance phase 1: Progress report. (Repon No. DOT/FANAM-91/16). Springfield, 

VA: National Technical Information Service. 

Stalhammer, H. R., Leskinen, T. P. J., Kuoriillca, I. A. A., Gautreau, M. H. J. and Troup, J. D. G. (1986). 

Postural, epidemiological, and biomechaniclll analysis of luggage handling in an aircraft luggage 

compartment. Applied Ergonomics, 17, 177-183. 

Sutherland, V.J., and Cooper, C.L. (1988). Sources of work stress. In JJ. Hurrell, L.R. Murphy, SL. 

Santer, C.L. Cooper (Eds.), Occupazianal Stress - issues and tkvelopments in research. London: 

Taylor and Francis. 

Van Wely, P. (1970). Design and dls;;ase. Applied Ergonomics, 1, 262-269. 

Westgaard, R.H., and Aaraas, A. (1984). Postural muscle strain as a cansal factor in the development of 

musculoskeletal illnesses. Applied Ergonomics, 15, 162-174. 

91 
~ '. .. . ' ... 

Wickens, C.D. (1992). Engineering Psychology and Human Perfomumce (2nd eeL). New York: 

Harpec Collins. 

Wiener, E. L. (1975). Individual and group differences in Inspe.:tion. In Drury, C. G. and Fox, J. C. 

(Eds.), HllniGII reliability in quality controL London: Taylor & Francis, 19-30. 

Wiker, S.F., Langolf, G.D., and Chaffin, D.B. (1989). Arm posture and human movement capability. 

Human Facton, 31(4), 421-441. 

Zhang, L., Drury, C. G. and Woolley, S. M. (1991). CoDSlrained standing: Evaluating the footltloor 

interface. Ergonomics, 34, 175-192. 

92 
Evaluoting the Visual Environment in Inspection: A Methodology and a Case Study 

Chapter Six 

Evaluating the Visual Environment in Inspection: 

A Methodology and a Case Study 

6.0 INTRODUCTION 

Visual inspection accounts for almost 90% of all inspection activities; thus, it is imperative that the task 

be performed in the most suitable work environment. Studies in aircraft inspection have shown that poor 

illumination, glare and other a:lverse lighting conditions could be important reasons for "eye strain" or 

visual fatigue. Visual fatigue causes a OOterloratioo in the efficiency of human performance during 

prolonged work. The purpose of this study is to develop a methodology which allows adequate lighting 

equipment to be selected in order to provide an improved visual environment. 

Much of the recent literature on lighting requirements is concerned with costs of providing the light, 

whether purchase costs, operating costs or maintenance costs. However, the purpose of lighting is to allow 

rapid and effective human performance. The costs of persollllel time and the potential cost of even a 

single human error are orders of magnitude higher than the costs of providing the lighting. Thus, in this 

study, adequacy of lighting is the major criterion for lighting choice. 

The sections below provide an outline cf the sequence of steps which were followed to demonstrate and 

ultimately comprise the advanced methodology. Initially, the basic principles of lighting and lighting 

system design are related to aircraft inspection. Thereafter, through site visits, the existing visual 

en.,ironment in aircraft inspection is assessed. An evaluation was then undertaken at a single facility in 

order to acquire detailed data and to demonstrate how to perform a human factors investigation of a visual 

environment. This investigation included photometric evaluations of the ambli:nt and task lighting as well 

as input from inspectors at four different facilities. 

Concurrently, alternative portable and personal lighting sources were evaluated at the same facility and 

in the laboratory. Recommendations are then offered based upon the information obtained. This step 

illustrates the utility of using an organized approach to structure the various components which comprise 

a visual environment in order to allow adequate light sources to be suggested. Finally, the methodology 

which encompasses all the preceding steps is formally advanced. 

6.1 LIGHT CHARACTERISTICS/LIGHTING SYSTEM DESIGN 

Four fundamental light characteristics (i.e., light level, color rendering, glare and reflectance), the 

principles of specialized lighting. and the basic requiremeJllts of lighting design need to be considered in 

relation to aircraft inspection. 

6.1.1 Light Level 

The recommended illumination depends upon the type of task and whether the visual task is of high or 

low contrast. General lighting requirements for different tasks can be found in Eastman Kodak (1983) 

and illuminating Engineering Society (JES) (1987). Vision can be improved by increasing the lighting 

93 
:·· 

ChapterSu 

level, but only up to a point, as tbe law of diminishing returns operates. ..o\lso, increased illumination 

could result in increased glare. Older persons are more affected by the glare of reflected light than 

younger people, and inspectors are often senior personnel within a maintenance organization. 

According to lES (1987), direct, focussed lighting is recommended for general lighting in aircraft hangars. 

Inspection of aircraft takes place in an environment where reflections from aiiplane structures can cause 

glare so that low brightness lumiuaries should be installed. Often. additional task lighting will be 

necessary wben internal work, or shadowed parts around the aircraft, result in Kow illumination levels. 

Table 6.1 presents the required illumination levels for aircraft maintenance and inspection tasks (IES, 

1987). Generally, most maintenance tasks require between 75 foot-candles (f-c) and 100 f-c, although 

more o:letailed maintenance tasks may requir.: additional illnminatiQn. General line inspections {e.g., easily 

noticeable dents) may only require 50 f-c; however, most inspection tasks demand much higher levels. 

From the site observations of actual defects, it is apparent that many difficult inspection tasks may require 

illumination levels up to or exceeding 500 f -c. Based upon the current lES standards, it is recommended 

that the ambient light level in a maintenance hangar be at least 75 f-c in order to perform pre- and postmaintenance/inspection operatio!lS and some general maintenancermspection tasks without the necessity 

for additional task lighting, Furthermore, adequate illumination levels may be obtained in a majority of 

in..<pection tasks and many maintenance tasks through the utilization of task lighting. 

Table 6.1 Levels of lll•Jmination Required in Aircraft Inspection/Maintenance 

(IES, 1987) 

TASK F-C 

Pre-/post-maintenance and inspection 30-75 

Maintenance 75-100 

Inspection 

Ordinary 50 

Detailed 100 

Fine 200 

6.1.2 Color Rendering 

Color rendering is the degree to which the perceived colors of an object illuminatro by various artificial 

light sources match the perceived colors of the same object wben illuminated by a standard light source 

(i.e., daylight). The color rendering of task lighting is important for inspection bec!l!'se "change in color" 

of sheet metal is often used as a clue to detect corrosion, wear or excessive heating. 'lbe difference in the 

spectral characteristics of daylight. incandescent lamps, fluorescent lamps, etc., have a large effect on color 

rendering. Such effects are described in detail in IES (1984). Table 6.Z presents some of the commonly 

us'-'<! lighting sources and their characteristics (adapted from Eastman Kodak, 1983). 

94 
Evaluating the VisUill Enviro11111ent in Inspeetion: A Methodology and a Case Study 

Table 6.Z Commonly Used Lighting Sources 

TYPE DF LIGHT 

SOURCE COLOR COMMENTS 

Incandescent good Commonly used, but prone to deterioration over 

time. High energy lost, but convenient and 

portable. Lamp rrfe about 1 year. 

Fluorescent fair to good The afficiency and color rendering capabilities 

vary greatly depending upon tube type. 

Problems of flicker may have an annoying effect 

while performing inspection. Can be dangerous 

with rapidly cycling machinery. Lamp life 5-8 

years. 

Mercury Vapor very poor to fair Green/blue colors are unusual, and output drops 

rapidly with age. Lamp life 9-12 years. 

High Pressure fair Monochromatic yellow light. High efficiency 

Sodium Lamp lamp ranging from 80-100 lumens per watt. 

Lamp life 3-6 years. 

Low Pressure Sodium poor Highly efficient light source but yellow in color. 

Lamp Lamp frfe 4-5 years. 

6.1.3 Glare 

Direct glare reduces an inspector's ability to discriminate detlil and is caused when a source of light .in 

the visual field is much brighter than the task material at the workplace. Thus, open hangar uoors, roof 

lights, or even reflections from a white object such as the workcard can cause glare. Glare can also arise 

from reflections from the surrounding surfaces and can be reduced by resorting to indirect lighting. The 

lighting system should be designed to minimize distracting. or disabling glare, using carefully designed 

combinations of area lighting and task lighting. 

6.1.4 Reflectance 

Every surface reflects some portion of the light it receives as measured by the surface reflectance. High 

reflectance surfaces increase the effectiveness of luminaires and the directionality of the illumination. 

Specular, or mirror-like, reflectance should be avoided as it produces glare. Diffuse reflection, for 

example, from a semi-matte surface is preferred. Thus, for an aircraft hangar, it is important that the walls 

and floors are of high diffuse reflectance (i.e., light paint. patterned plastics) so that tbey help in reflecting 

light and distributing it uniformly. This is more critical under the wings and fuselage where there may 

not be adequate lighting, due to aircraft shadows. Table 6.3 presents recommended surface reflective 

values to assist in obtaining an adequately uniform visnal environment. 

95 
Table 6.3 Recommended Diffuse Ref!Pdive Values 

(Arlapted from IES 1987} . • 

SURFACE REFLECTANCE 

Ceiling 80to90% 

Walls 40to60% 

Equipment ~to45% 

Floors not less than 40% 

6.1.5 Specialized Lighting 

During visual inspection of an aircraft fuselage the inspector is looking for multiple defects, including 

corrosion, ripples, hairline cracks in the metal components. dents in the fuselage. missing rivets, damaged 

rivets ("pooched," "dishedH rivets), and rivet cracks. 

It is possible that no one single lighting system is suitable for detl'ding all defects. Therefore, the use of 

spfodaliwJ lighting systems wbich make each class of defect more apparent may be neces•a,y. However, 

the use of special light systems implies !bat the area must be examined for each class of defects 

sequentially rather than simultaneously, wbich could involve time and expense. For example. the diffused 

nature of general illumination tends to wash out the shadows while surface grazing light relies upon 

showing shadows to empbasi:re objects that project above or below the surface. Task visibility is distinctly 

better for surface topography With grazing light even though a lower level of illumination is used. An 

example of this scenario is the inspection of the fuselage for ripples. Ripples are easier to detect using 

surface-grazing lighting hecanse general illumination tends to wash tbem out. However, normal-incidence 

lighting may mask important textural and color differences. lbe ligbting sbould be compatible with the 

visual objective regarding the form and texture of the task object. Grazing light reinforces an inqxession 

of the texture wbile normai incidellt ligbt allows the di.scriminatioo of color and surface, but minimi:res 

the perception of surface variations. 

6.1.6 Design Requirements For Ugbtfng 

literature on visual search has shown that the speed and accuracy With wbich tbe search process can be 

liCC(\mplishOO is dependent on the conspicuity of the defect which in tum is dependent on size of the 

defect, detect/background coutrast, and lighting intellsity (DI:ary and Fox. 1975). 

Ugbting design also has broader requirements to fulfill In order for the inspection to be successfnl, the 

lighting sbould be such that the following tasks can be perfOtmed satisfactorily and preferably optimally: 

inspecting (visual search) the aircraft structure for defects, reading the workcardrmstructions, moving 

around the aircraft (using the scaffolding, or equipment. e.g., cben)picter), and special purpose ligbting 

should not .interfere with any otbec parallel task (e.g., access or maintenance) in progress. 

96 
Evaluating the Visual Environment in Inspection: A Methodology and a Case Study 

The inspection task is frequently diflicult because of the heavy perceptual load present. In designing the 

lighting system, the objective must be to reduce visual fatigue caused by poor illumhation and poor 

contrast In designing lighting systems, one must consider the minimwa lighting requirements for each 

task and subtask, tbe type of artificial light sources that can be used to illuminate the work surface, lhe 

amount of task lighting that can be provided and the available metbods to minimize glare. These factors 

must be balanced witb implementation and operating costs (IES, 1987); however, the total cost of 

installing, running and maintaining lighting is a small fraction of tbe cost of eitber tbe employment of 

personnel or of rectifying lighting-induced human errors. 

6.2 THE EXISTING VISUAL ENVIRONMENT IN AIRCRAFI' INSPECI'ION 

6.2.1 Classification or Light Sources 

The lighting sources employed in aircraft inspection include ambient lighting which is comprised of 

daylight, area and specialized lighting (built into aircraft); and task lighting which includes portable 

lighting (set up at inspection site) and personal lighting (e.g~ flasblight). The ambient lighting represents 

tbe minimwn lighting level available iu a task while task lighting represents tbe maximwn lighting level, 

botb from lighting devices set up to cover an inspection area, and from personally-carried lighting. Note 

that to provide adequate lighting for any task it should be possible to reduce glare from ambient lighting 

and use tbe task lighting in a focussed manner to illuminate tbe task without causing unnecessary glare. 

6.2.2 Site Observations 

In tbe first phase of tbis research program many inspection/maintenance sites were visited (Shepherd, et 

al., 1991). Detailed Task Analyses were performed on nwnerous inspection activities, resulting in a list 

of examples of poor human factors design. Each example represents an opportunity to improve tbe 

hwnanlsystem fit, and hence., increase job performance witb decreased work stress. 

The conclusions to be drawn from these obserVations are that ambient lighting in some cases can range 

from inadequate to poor for performing inspection tests, which could result in visual fatigue and 

deterioration of performance. Moreover, task lighting was not adequate, lighting equipment was not 

always portable, and the lighting level was well below1he IES recommended level of75-100 f-c in most 

visual aircraft inspection tasks (IES, 1987). These conclusions are subS!antially the same as found by the 

FAA's Office of Flight Standards Aging Fleet Evaluation Program which measured tbe visual environment 

at nineteen sites performing "D" checks (Thackray, 1992). 

6.3 EVALUATION OF A VISUAL ENVIRONMENT 

As a demonstration of how to pet form a human factors study of lighting in a facility, an investigation of 

tbe visual environment at a representative maintenance hangar was performed. The hangar was due for 

closure, so that findings would be applied only in otl:lel" hangars. This study included an evaluation of the 

ambient lighting, task lighting, and perceived lighting characteristics based upon input from inspectors. 

97 
>'.'. 

6.:U Evamation Of Ambient Illmnirultion, Imninanre, 81111 Re!1ectance 

The evaluation measured the illumination and luminance levels JXO(!uced by the ambient ligbt SOIIlCel' 

only. lighting characteristics of the personal and portable ligbiing were considered separately. Procedures 

were performed according to the IES lighting Handbook (IES, 1984). The illumination leveis Indicate 

the amount of light falling over the area (in f-c), wbile lnminaoce levels rep-ese:nt the qwmtity of light 

reflected off the various SUifaces (in foot-Iamberts (f-1)). 

1be illumination and floor lmninance levels were obtained in two different airallft b&ys. bay #1 (with an 

aircraft present) and bay 412 ( witbont an aircraft preseut). Each bay area was divided intG zones and several 

readings were taken within each zone at night with the hangar dt>oo! dosed Average illmninatioD and 

luminance values were calculated by aircraft area (Figure 6.1). Floor retJectance values, the amount of 

light reflected off the floor 

compared to the amount of 

light falling on the floor. {i.e., 

floor luminancefillumination) IHumlnatlon (f-c} were calculated and given in 100-r.:.~.;:...;~;..;._.;;__:... _________ _, 

Figure 6.2. 

The average illumination 

levels varied dramatically ao+------------------1 

between areas. Figure 6.1 

indicates that the areas under 

the fuselage and wings had 

considerably lower 

illnmjmltion than the open 

areas (i.e., wbere no aircraft 

was present). 'Ibis is a 

concern. for many visual 

inspectioa tasks occur in 

these poorly lit areas (ie., 

under the wings and 

fuselage). The floors are 

presently a natural grey color 

(cement), thus resulting in 

low average floor Jnrninance 

and reflectance levels across 

all areas. The floors sbould 

be painted a lighter color 

(e.g., white), which would 

improve the overall 

illumination levels, especially Figure 6.1 Dlmnination by Alnr.lft 

under the wings and fuselage. 

However, any paint used should be non-glossy ro eliminate specular ref!ections from the floor SUifac:e 

For new hangars, or major renovations, lighter colored fJoodDg could be installed 

98 
Evalluzting the VlSlUil Environment in Inspection: A Methodology and a Clzse Stu4y 

6.3.2 Evaluation Of Task 

Illumination, 

Luminance, and 

Reflectance 

A representative sample of 

aircraft visual inspection tasks 

was selected ftom various 

locations on a Fok:ker F-100: 

air conditioning access (A/C), 

ca_rgo compartments (cargo}, 

exterior fuselage-nose, 

nosewell, and wheelVt-ell. A 

lighting evaluation (i.e., 

illumination, luminance, and 

reflectance levels} was 

performed with the results 

shown in Table 6.4. The 

light environment for each 

task includes the contribution Figure 6.2 

of the arnbient levels In 

Perceived Glare by Aircraft Area 

conjunction with any additional task lighting. 

Values were obtained ftom various locations in each task area under actual Inspection conditions; that is, 

while the task lighting of choice (i.e., personal/portable) was utilized. Generally, the average task 

illumination levels were adequate. with the exception of the nosewell. However,large variabilities existed 

in these levels within each area, primarily dependent upon whether it was possible to aim the lighting 

equipment at t.'le point of inspection. In many instances, areas were difficult to access with the lighting 

equipment, thus not allowing adequate levels of lighL Task lighting 'IN-as necessarily the primary light 

source in all task areas, for the ambient ilb,mination level> were inadequate. Thus. the accessibility of 

the area and the portability of the task lighting affected the ligbt level at a majority of inspection points. 

Table 6.4 Task Ught Environment and illumination by Task Area 

TASK CONOmONS 

AREA 

Light Environment Illumination (f-c) 

AJC 30-CeU Flashlight X = 115 80=138.0 

Cargo Headlamp plus General 182 80=72.4 

Fuselage-Nose 30-Ce:: FlR::>hligl'lt plus Genera! 97 50=46.0 

NoseweU 3D-Cell Flashlighi plus Genaral 42 80=22.6 

WheelweD 30-CeU Flashlight plus General 102.1 80=40.0 

99 
Cluzpter Six 

6.3.3 Inspector Perceptions 

In addition to the detailed measurements obtained at one facility, inspectors' perceptions of the visual 

environment were assessed at several other facilities within the partner airline. Psychophysical rating was 

obtained from 51 inspectors and maintenance personnel from four other sites, to allow a detailed 

assessment of the perceived quantity and quality of the general and task lighting. InspectoiS and 

maintenance personnel were asked to evaluate the lighting characteristics of the visual environment (e.g., 

contrast, glare, fiicker, color rendering), as well as tbe adequacy of the lighting equipment (e.g., ease of 

handling, light level and focns control). 

Psychophysical rating was obtained on the visual environment and combined by airJaft area: upper 

exterior areas (above wing chord line), lower exterior areas (below wing chord line), and interior areas. 

Generally, according to the frequency distributions, the perceived light levels and contrast ranged from 

adequate to good in the upper exterior areas, bnt there were many instances of perceived glare. 

Conversely, the perceived light levels and contrast were frequently rated as inadequate in the lower 

exterior and interior areas, but there was less perceived glare (Figures 6.3, 6.4 and 6.5). Color rendering 

was perceived to be adequate by most personnel, although this disttib 1tion was skewed towards inadequate 

in the lower exterior and interior areas (Figure 6.6). 

.u .......... o-- 1!?21 ... -

Figure 6.3 Perceived light Level by 

Aircraft Area 

100 

--- o--

Fignre 6.4 Perceived Contrast by Aircraft 

Area 
Evaluating the V'rsual Enviromnent in Inspection: A Methodology mula Cuse Study 

-

- - -

Figure6.5 Perceived Glare by Aireraft Area 

In 1he upper exterior areas. a majority of personnel 

indicated a reliance on primarily genecal lighting {over 

90% ), with a smaller depe• deuce on daylight and 

personal lighting (Figure 6.7). Ponllble ligbt:i!!g 

seems to be rarely used. In comrast, in the lower 

exterior and interior areas, personal ligbiing is the 

primary light soun:e (over 90% ), with genecal and 

portable lighting being utilized somewhat. Daylight 

c.ontributes millimally to tile visual environment in 1he 

lower exterior and interior areas. This is presumably 

the reason why color rendering was perceived to be 

worse in these areas for artificial light is tile primary 

source. 

A majority of personnel indicated that both personal 

and portable lighting equipment produoe adequate 

light levels. There were varied perceptions with 

respect to handling, 3lthough a majority felt personal 

lighting was adequate and portable lighting was 

inadequate. Likewise, a majority of personnel feel the 

focus ability of personal lighting was good, while the 

aiming ability of portable lighting was inadequare. 

101 

-

-

--- CJ--

- -

I?Z!I..__ 

Figure 6.6 Peroeived Color Rendering by 

Aircraft Area 

__ .__ -- -~ m~ CJ- -- Figure 6. 7 lighting Utilization by Aircraft 

Area 
These perceptions may indicate why personal lighting is relied on more than portable lighting (Figure 

6.7); it is easier w handle and oontmL A need exists for better portable lighting w decrease re!lanre on 

personal lighting in restricted spaces. 

Fmally, general comments and concerns related to personal and portable lighting systems and the visual 

environment were obtained. 'lbe comments are ranked according tD the frequency with wbieh inspectors 

and maintenance personnel indicated the importance of the various factors (Table 6.5). The major 

considerations fall within the categories of lighting, ease of handling, durability, work shift, hangar 

maintenance, flexibility, and miscellaneous attributes. 

light output/brightness of the visual environment was the biggest concern of personnel. The ability to 

control the light output w reduce glare were also of particular concern. Color rendering and contrast were 

of lesser importance. A few personnel indicated the need to investigate alternative light sources (e.g., 

lasers). Surprisingly, flicker normally associated with fluorescent lights was not indicated as a major 

concern, although fluorescent lighting was not the primary light source utilized across the population 

sampled. Specific to personal lighting, personnel indicated the effect of low-quality batteries and bulb 

type on the quality of light 

The ease with which equipment was handled was of particular concern. Personnel indicated that light 

sources wilich are difficult to use will not be u@zed, obviously affecting the visual environment. The 

weight/size of the lighting equipment was found to be the primary determinant of ease of handling, with 

accessories a secondary facwr. The set-up required for portable lighting was found to directly affect 

utilization. Electric-powered personal lighting, as opposed to battery-powered, was found to be less 

portable due to the need for power cords. Power sou.-ces, suCh as battery-packs, may be a promising 

alternative for improving the portability of electric-powered lighting equipment 

The general durability (i.e., daily wear and tear) of lighting equipment was a consideration, for it affects 

the visual environment For example. personnel indicated that if their tlashlight lens was scratclled, the 

light outpqt decreased. The safety requirements met by the lighting equipment [e.g., Occupational Safety 

Health Administration, (OSHA)] is another issue which was indicated, and becomes critical in hazardous 

areas (e.g., fuel tanks). lighting equipment wbich meets specialized safety requirements, as evaluated in 

this study (e.g., explosionlvapor-p-oot), needs continuous investigation to ensure oompliance with changing 

standards. 

Personnel indicated that the workshifts (i.e~ day/night) resulted in drastically different visual environments, 

possibly dictating different lighting needs. General hangar maintenance can also affect the visual 

environment For example, as discussed earlier, light paint on the floor, walls, and ceilings causes light 

to be reflected and creates a brighter work environment. Furthermore, these surfaces, in addition to the 

lights themselves, must be free of dirt and grime in order w reflect/produce adequate ligbt 

Often the flexibility of light sources is important for performing inspection, pmicularly with respect to 

specific task demands and fault types (e.g., light of grazing incidence may be necessary to highlight ripples 

wilile light perpendicular to the surface may be necessary for detecting other common faults). Flexibility 

is more easily provided by personal lighting equipment (e.g., flashlight and headlamps) rather than by 

portable and direct lighting which are more suited to meet general lighting requirements. 

102 
Evaluating the Visulll Environment in Inspection: A Methodology tuUl a Ctzse Study 

Table 6.5 Relevant Lighting Considerations Based Upon Inspector Perceptions 

CHARACTERISTICS PERSONAL PORTABLE FREQUENCY 

LIGHT 1. Output/brightness 1. Output/brightness 27 

2. Glare/brightness 2. Glare/brightness 6 

control control 

3. Distribution/focus 3. Distnbutionlaim 5 

4. Color rendering 4. Color rendering 1 

5. Contrast 5. Contrast 2 

6. Alternative 6. Alternative 2 

sources sources 

7. Ricker 7. Ricker 1 

8. Power source 4 

(battery type) 

9. Bulb type ~ Total 51 

EASE OF HANDLING 1. Weight/size 1. Weight/size 15 

2. Accessories 2. Accessories 2 

3. Set-up 3 

3. Power source g 

Total 22 

DURABILITY 1. General 1. General 5 

2. Safety 2. Safety 5 

requirements requirements 0 

3. Bulb life 3. Bulb life ! 

4. Battery rife Total 18 . WORK SHIFT 1. Light (day/night} 1. Light (day/night} 9 

2. Shiltwork 2. Shiltwork ...?. 

Total 11 

MAINTENANCE 1. Paint 1. Paint 7 

2. Hangar 2. Hangar g 

cleanliness cleanliness Total 9 

FLEXIBILITY 1. Task demands 1. Task demands 2 

2. Fault types 2. Fault types ...?. 

Total 4 

OTHER ATTRIBUTES ~- Cost 1. Cost 5 

2. Access 2. Access 4 

3. Availability 3. Availability 2 

4. Individual 4. Individual ..1 

differences differences Total 12 

Items such as cost were indicated to be a concern. For example, several personnel indicated that 

rechargeable flashlights are superior to other types of less expensive lights. Safe disposal of used batteries 

103 
Ch4pterSiz 

may become an increasingly important reason for choosing recbargeable lighting systems. In many 

situations personnel purchase tbeir own equipment, as opposed to using less adequate equipment supplied 

by the company. 

As discussed above (Section 6.3.2), access to an area can dictate the quality and quantity of light on a 

surface. There should be m effort not only to improve the portability of lighting equipment, but more 

importantly, to consider the human inspection process at the aircraft design stage. The availability of 

various lighting sources was a concern, and may be dependent upon the company supply, hangar design 

(e.g., availability of electric outlets around the aircraft), or accessibility. Finally, common to all inspection 

tasks, individual differences must considen:d. 

6.4 EVALUATION OF ALTERNATIVE LIGHTING SOURCES 

An evaluation of lighting sources was pedormed to identify systems which possess features which may 

contribute to the existing visual environment of aircraft inspection/maintenance operations. This evaluation 

included an investigation of available systems. and both laboratory and field evaluation of the selected 

sources. 

6.4.1 Laboratory Evaluation 

A number of both personal and portable lighting systems was selected to represent the typeS currently 

being used in inspection and alternative sources available in catalogs. Several attributes of these selected 

personal and portable lighting systems were investigated in a controlled environment (i.e., light source, 

weight, focusfaiming control, durability, safety requirements, accessories, and light output/distribution). 

The results of this investigation can be found in Reynolds, et al., 1992. 

6.4.2 Field Evaluation 

A sample of the lighting systems which appeared to hold promise in the laboratory evaluation are 

presented in Tables 6.6 and 6. 7, and were further investigated during actual task performance. 

104 

1 
Evaluating the Visrull Environment in Inspection: A Methodology lliUl a Case Study 

Table 6.6 Specifications of Selected Portable Ughting Equipment (center illumination measured at 

*O.Sm or **2.0m) 

WL Aiming Genwal Safety Ac-riUghtSource (la.) Control Du ..... irlty Requirements 

Handlamp FluOJ&scent 0.8 No Ad&quats NEC 11410- Hook 

13 Watts 35(a)(b).36. 

85 ,.,. 42(a)(b),44,45 

OSHA 

#1926.405(E)(F)(l) 

Olfoi)(iiij(A)(B)(V) 

UL listed 

Portable Auo..,scant 10 No Adequate NEC 11410. Hangars, 

Lamp 27Watts 35(a)(b),36, Magnets 

164 f-c .. 42(a)(b).44.45 

OSHA 

#1926.405(E)(F)(I) 

(j)foij(ii)(A)(B)(V) 

UL listed 

Standing Halogen 9 Yes Adeqlaate UL istacl for Hanclla 

Lamp SOOWatts indoor/outdoor use. Stand 

12001-cTable 6. 7 Specifications of Selected Personal Ughting Equipment (*center illumination measured at 

05m) 

WL Focua 

- Safety 

UghtSource (lba..) Control Dunobility Pow...- Requiram•nta Acc:111ories 

2[).Cell Krypton 1.5 Yes .~1ata Baltety Explosion-proof None 

flashlight Bulb MIL-ST0-810C 

340 f-c* 

3D-Cell Krypton 2.0 Yes Ad&quals &tlery Explosion-proof None 

flashroght Bulb MIL-sT0-810C 

1100 

1-<>* 

40-CaR Krypton 2.4 Yes Ade<JJals Battery Explosion-proof None 

flashfight BoJib MIL·ST0-810C 

1900 

f-c* 

Heacllamp lncan- 1.9 Vas Adequate Battery Nooo indicated Headband 

descent Bal!el'f clamp 

Bulb 

1500 

f-c* 

The following provides a summary of the results obtained from the laboratory and field evaluations. 

• There are two different kinds of lights: inspection and work lights. Inspection lights (i.e., dynamic 

sources) must provide easy handling, for inspection normally demands frequent movement in and around 

the aircraft. In addition, the lights must provide a focussed beam of light which can be controlled to 

105 
ChapterSi% 

reduce glare. Work lights (i.e., static sources) need not be as portable as inspection liglm, for they are 

normally used in one place for a period of time (i.e., generally 30 minutes or more). 

• The flashlights provide adequate light, durability, and focus control to reduce glare. They are also easily 

pcJttable, which suits most Inspection tasks. The light outputs and distributions of the flashlights increase 

with the size of the light (i.e., 20 to 40). The larger lights have more batteries; however. tbey are also 

heavier. The focus ability of the flashlights provides either an intense focussed beam or less illumination 

over a larger area. 

• The headlamp provides adequate light and focus control to reduce glare. It produces a comparable 

amount of light as the 4D-Cell flashlight, although it is lighter and allows hands-free portability. However, 

it m~ no additional saf.;:ty requirements, thus possibly limiting its use in some environments. The actual 

weight of the lamp is less than the indicate::i weight, for the batteries are separated ftom the light source 

(0.3 lbs.). 

• The handlamp is not well suited for many inspection tasks because the power cord reduces its portability 

and it does not provide a highly focussed beam. However, this light can serve liS a small portable light 

source. It produces less light over a smaller area than the other portable lights, but gives off minimal heat 

and can fit into small access areas. It is very durable and meets OSHA and National Electrical Code 

(NEC) safety requirements related to general electrical codes. 

• The portable lamp is a good static light source. It can be hung, using the provided strap or magnet, or 

placed (e.g., under a wing) in the work area for overall, beat-ftee light. Furthermore, these lamps meet 

OSHA and NEC safety requirements related to general electrical codes. 

• The standing lamp provides a large amount of light over a large area. It can be used to mumjnate large 

static work areas. However, it gi'lres off heat, and thus could not be used for interior Jnspections or in 

small areas, limiting its use to open, elrtedor areas. In addition, it is UL listed for indoor/outdoor use, 

possesses upfdown aiming control, is light-weight, and has a handle for easy portability and set-up. 

• The color rendering characteristics of the standard incandescent lamps (i.e., headlamp ), krypton lamps 

(i.e., flashlights), and halogen lamps (i.e., standing lamp) are superior. The fluorescent lights generally 

provide adequate color rendering characteristics, dependent upon the chemical composition of the liner, 

and are more energy efficient, producing less heat than incandescent lights. 

6.5 RECOMMENDATIONS 

Based upon the above evaluation of the visual environment at the tested facility and the selected sample 

of lighting sources, initial recommendations are presented. The task demands, the restrictiveness of the 

space to be inspected, the ambient light conditions, and the lighting fl'.quirements are considered (Table 

6.8). ·Recommendations are advanced for the specific task environments evaluated earlier (Section 6.3.2), 

and oniy consider the sample of lighting sources selected for detailed field evaluation (Section 6.4.2). 

Caution should b<! exercised in generalizing these recommendations to other task situations and light 

sources, although the methodology preser.!ed here can be used to determine the applicability of e.ach light 

source il'l new situations. As discussed previously (Section 6.3.2), the ambient illumination levels in all 

106 
Evalullting the Y"ISlUII Environment in Inspection: A Metlwdology and a Case Study 

the task areas were inadequate for satisfactory performance. Thus, there must be some reliance on 

personal or portable lighting in each area. 

For each task area, the task demands dictate the required illumination, the focus/aiming, and the required 

handling. A majority of inspection tasks require dynamic sources, to allow for frequent movement in and 

around the area; whereas, maintenance tasks may be adequately illuminated by static sources. Although 

inspection tasks are the primary focus in this study, recommendations will also be made for static sources 

for they can be useful in contributing to the ambient light level in many areas. 

Based on the task demands and corresponding illumination requirements, it is observed that each of the 

recommended lighting systems meets the illumination requirements as observed in Table 6.8 and Table 

6.6 through 6.7. Furthermore, personal lighting not only provides the necessary illumination but also 

greater flexibility in terms of maneuvering the light source (e.g., a flashlight can be used both at grazing 

incidence to detect ripples and at normal incidence to studY corrosion). 

The reStrictiveness of the area to be inspected was rated on a two-point scale (i.e., reslrictedfunrestricted). 

Thus, restricted areas (i.e., A/C access, nosewell, and wheelwell) require the light source to be manipulated 

around obstructions in a cramped area, in order to provide an adequate visual environment. As was 

discussed previously (Section 6.3.2), large variability existed in the light levels in these areas, dependent 

upon the accessibility of the light source. The cargo and exterior fuselage-nose an:-.as are considered 

unreStrictive, for the light source is not obstructed by the environment Any size personal lighting may 

be used here without compromising the visual environment. 

The inspection of the A/C access llfea requires a dynamic light source which possesses focus and aiming 

ability and provides an average level of 100 f-c of illumination. The 2D-Cell flashlight and the beadlamp 

are recommended for they meet these requirements and are small enough to be manipulated around the 

area. In addition, the handlamp is recommended as a static light to increase the general light level in the 

area in order to reduce the reliance on personal lighting. It is small and can be hm1g or placed in the area, 

and does not give off heat 

Similarly, inspection of the cargo and exterior fuselage-nose areas also require dynamic light sources with 

easy controllability. In addition, an avenge illumination level, when combined with the ambient light 

level, of 100 f-c in the cargo area and 200 f-c in the exterior-nose area is required. The areas are not 

restricted, thus any size flashlight or the headlamp could be used as a personal lighting source. The 

standing lamp could be aimed up from the outside of the aircraft, or the portable lamp could be 

hung/placed in the area, to provide overall light 

Finally, inspection of the nosewells and wheel wells requires dynamic, focussed average illumination levels 

of 100 and 200 f-c, respectively. The areas are somewhat reStrictive, thus requiring the smaller flashlights 

or headlamp for better handling. The handlamp and portable could be hung/placed in tight locations in 

these areas, while the standing lamp could be aimed up into these areas for general overall lighting. 

107 
Table u Ughling Recommendations fOC' Vallous Tasks Bued Upon lhc Tasl< Demands, the LlghtiDg Requirements, and The Size of the Area 

LIGHTING ftiQUHIIMINTI - AMDIINT 

AREA TASK DEMANDS IPAOI ILLUM. ........ tr· 'ac:uat H•ndllng ftECOMMINDf,TIOHI ,,..,, ., Aiming 

.NO Q!Od< lor lHb and oocurly clllomo Aollriclod 0 100 VOl/ ll)l1amlo :!Docotlluhlgllt 

v .. HNdlomp 

81ollo -p 

0.190 Q!Od< lor IOCUily ......... miMing 1-.oa, ~ 12 100 Yeo/ "'"""'~ Rolhl;hto 

opllogo end conollon, donJo, Clllck - v .. HNdlomp 

-lord-. lnopocllnlomol..-. hlngo 

O!Wit,llltlngo,....,. hotMilg. CM*Imeloflol 

- 8tondlng lomp 

•• ~:::, .. _ "'•llad1od "'olopl.lnopoct Porllblo limp 

lorMCU ... - ...... 

i -uo· Potiotmado-vlludlnopaollonoloiM lho- 44 200 Yeo/ Jlrnlm~ Fluhlghto 

- ~ lordofn.........,, miMingfeolonllo. v .. Hoodlomp 

S1allo 8tondlng lomp 

NoMwel lnopoct nceolilnllng goar lotqUO.Jnk contor !ar Ro- 2.11 100 VOl/ P/Mitllo 

--

RD,ao.Col ftuNghlo 

ploy, Chock lor HOUrily olltomo and looko. Yeo HNdlllnp 

81ollo -.. 

8tondlng lomp 

-limP 

WhootMI lnopoct moln .. ,clrig goor,landlnu goar Aollriclod 3 200 Voo/ "'"""'"' 2o,ID-Ooltluhlr#>t 

IIMmbiy, tor .. ......., end cracb.lnopocl tor 

-'rily ol jolnto; Mloly pin lor ""'"'·l*lgo• ot 

v •• HNdlomp 

deer fon ... or end play. 

- Hlndlomp. 

StMdli1g lamp 

Porllblo famp 

f 

~ 

I 

·---·--

.\ 

',\ .. s~·.·­

.1_! :' 
Evaluating the Visual Environment in Inspection: A Methodology and a Cose Study 

6.6 GUIDE FOR VISUAL ENVIRONMENT EVALUATION 

A methodology by which to evaluate and design a visual environment may be advanced based upon the 

techniques employed in the above demonstration project. A four-step methodology is presented below. 

I. Evaluate existing visual environment. The first step requires an investigation of the visual 

environment in order to obtain an understanding of the existing conditions and to focus the investigation 

on problem areas. Ambient and task lighting conditions and task analyses should be performed in order 

to determine the task demands and associated visual requirements. In addition, personnel should be 

consulted to obtain additional information regarding the light dlaracteristics and utilization and adequacy 

of the currently used lighting sources. 

2. Evaluate existing and alternative lighting sources. An evaluation of the existing and alternative 

lighting sources is performed in order to identify the cap2bilities of each source. Manufacturers' catalogs 

can be consulted to determine the current statns of lighting source technology. These alternative sources, 

in addition to the sources currently being used, can be evaluated. Evaluations performed to date, including 

the present one, have used various criteria to judge visual environments (e.g., light output, glare, 

luminance, etc.). There is a need for standard criteria which allow visual environments in aircraft 

maintenance/inspection operations to be evaluated in a consistent manner and which insure that important 

components of the process are not over-looked. An attempt bas been made to identify the most important 

components which need to be considered in the evaluation of an aircraft inspection/maintenance visual 

environment. Considering the operator perceptions and other factors discussed earlier (Sections 6.1 and 

6.3.3), a guide has been developed to indicate important considerations in the selection of adequate 

lighting sources (Table 6.9). Requirements are given for both personal and portable lighting. 

3. Selection of lighting sources. Once steps 1 and 2 are completOO, lighting sources can be selected 

based upon a comparison of the lighting requirements with the various lighting sources. An investigation 

of the existing visual environment (step 1 above) will allow the determination of the lighting requirements 

to be based upon the task dema!!ds. These results can be directly compared with the capabilities of the 

various lighting sources (step 2 above), to determine which lighting sources provide the most appropriate 

visual environment for each task analyzed. 

4. Evaluate and address general visual environment factors. In addition to atrending to the specific 

task conditions, there are factors relevant to the overall environment which need to be addressed. Based 

upon the operator perceptions and other factors discussed earlier (Sections 6.1 and 6.3.3}, a guide has been 

developed to indicate relevant considerations in the design of an adequate visual environment (Table 

6.10). The assesstnent of these considerations should result in additional improvements in the overall 

visual environment. 

This methodology does not provide guidelines which dictate how to design a visual environment. Instead, 

it provides a flexible process which may be followed to allow each practitioner to tailor the methodology 

to meet their individual needs. For example, this demonstration empbasizro consideration of lighting 

requirements, hatviling, and space restrictions in advancing recommendations. However, dependent upon 

each facility's needs and associated tasks, other factors identified in this study (steps 1 and 2) may be 

given stronger consideration (e.g., safety requirements, power sources). 

109 
Table 6.9 lighting Source Design Considerations 

CHARACTERISTICS PERSONAL PORTABLE 

LIGHT 1. Output/brightness 1. Output/brightness 

2. Glare/brightness control 2. Glare/brightness control 

3. Distribution/focus 3. DislributiorVaim 

4. Color rendering 4. Color rendering 

5. Contrast 5. Contrast 

6. Alternative sources 6. Alternative sources 

7. Flicker 7. Flicker 

8. Power source (battery 

type} 

9. Bulb type 

EASE Of HANDUNG 1. Weight/size 1. Weight/size 

2. Accessories 2. Accessories 

3. Power source 3. Set-up 

DURABILITY 1. General 1. General 

2. Safety requirements 2. Safety requirements 

3. Bulb life 3. Bulb fife 

4. Battery life 

flEXIBILITY 1. Task demands 1. Task demands 

2. Fault types 2. Fault types 

OTHER ATTRIBUTES 1. Cost 1. Cost 

2. Space 2. Space 

3. Individual differences 3. Individual differences 

Table 6.10 General Visual Environment Design Considerntions 

CHARACTERISTICS VISUAL ENVIRONMENT 

light 1. light !evei 

2. Glare 

3. Distribulion 

4. Color rendering 

5. Contrast 

6. Flicker 

Work Silift 1. light (day/night) 

2. Shiftwork 

Maintenance 1. Paint 

2. Hangar cleanuness 

Other Attributes 1. Access devices 

2. Availabllily of lighting sources 

110 
Evaluating the VlSlUZl Enviromnent in Inspection: A MetluJdology and a Cilse Study 

6.7 CONCLUSIONS 

This evaluation provides :> <nethodology by which various light sources can be matcbed to different tasks, 

based upon consistent criteria. This methodology includes an evaluation of the general and task lighting 

environments, the task demands, and alternative lighting sources. In addition, the major factors which need 

to be considered in the design of an adequate visual environment for aircraft inspection are identified in 

an initial attempt to standardize this evaluation process. The techniques utilized to assess the visual 

environment at a typical facility may be incOiporated into a formal methodology which may be utilized 

to investigate visual environments and guide selection of lighting equipment at other aircraft inspemon 

sites. 

6.8 REFERENCES 

Drury. C. G. and Fox. J. G. (Eds.) (1975). Human reliability in quality contro.. London: Taylor and 

Francis. 

Drury, C. G., Prabhn, P. V. and Gramopadhye, A K. (1990). Task analysis of aircraft inspemon 

activities: Methods and findings. Proceedings of the Human Factors Society 34th Annual Meeting, 

1181-1185. 

Eastrnan Kodak (1983). Ergonomic design for people at work (Vol. I). Besbmart, CA: Lifetime Learning 

Publications. 

illuminating Engineering Society (1987). IES Ughting handbook. a,uplication volume. New York: 

illuminating Engineering Society. 

illuminating Engineering Society (1984). IES ligl;ting handbook. reference volume. New York: 

illuminating Engineerlng Society. 

Reynolds, J. L., Gramopadhye, A and Drury, C. G. (1992). Design of the aircraft inspectionfmaintenanre 

visual em.ironment. Unpublished final report. (ColllraCt No. DlFAOl-92-R-08651). Federal Aviation 

Administration. 

Shepherd, W., Johnson, W. B., Drury, C. G., Taylor, J. C. and Berninger, D. (1991). Human factors in 

aviation maintenance, phase I: Progress report (Report No. DOT/FANAM-91/16). Springfield, VA: 

National Technical Information Service. 

Thackray, R. L (1992). Human factors evaluation of the work environment of the operators engaged in 

the inspection and repair of aging aircraft (Report No. DOT/FANAM-9713). Washington, D.C.: FAA 

Office of Aviation Medicine. 

111 
Chapter Seven 

Design of WOirkcards 

7.0 INTRODUCfiON 

The workcard is the primary document tbat controls an iDspedion task. It bas, 1hetefote, a great inCueJJce 

on inspection perfurmance. Costs, due to tmdetertable faults or faulty deteclion, wben weigbed against the 

cost of providing quality docnment'!lion, make a strong case for developing optimum documelltation am 

a melbodology (coupled with a set of guidelines) for designing such doQtmentation. This study develops 

such a methodology, based on the application of bmnan factors lmowledge to the analysis of silcraft 

inspection tasks, and demonstrates i:s use in two practical applicalions. The metbodology developed. being 

highly generic, can also b.! extended for design of information for portable computer-based workcards, 

as well as hypemledia-based OO<:umentatiQil fur inspection am majnten;mce tasks. The troject was 

perfoxmed in close coopecation with a partner airline to ensure tbat the results addressed airline concerns. 

7.1 A TAXONOMY OF ISStJES IN DOCUMENTATION DESIGN 

A taxonomy fur design of usable <Jocmnentation was developed using the inspection task analysis data 

from Phase 1 of this prognun (Siqlberd. et al., 1991) and tbe liteiatme on tbe bmnan factors of 

information presentation. This taxonomy has four basic c::ategorie& of design issu;;$; 

1. InfOillllltion Readability 

2 Infoonation Content 

3. InfOII!llltion Organization 

4. Pbysical Handling and EnvironmeDiaJ Facfors 

7.2 INFORMATION READABILITY 

Infoonation readability is the Cl1IX of any visually displayed material All 01ber issues become meaningful 

only after this primary issue has been addressed. Design issues affecting infoonation readability are tile 

typOgillpbic layout of the infmmation and tile language sttuciUie, namely,~ wools and lelteis. 

7.2.1 Typographic Layout 

Typogxapbic layout involves the use of vertical spacing. latenll positioning. paragraphing and heading 

positioning, etc. All the principles of typOgraphy cannot be satisfied wben tbe space available is limited. 

1n such cases, the use of secondary typOgiapbic and spatial cues becomes essentiaL Typographic cueing 

refers to use of variations in the appeaxance of the text in Older to provide a visual distinction, e.g.. 

boldfacing, italics. underlining, color coding. capital cueing, etc. Spa!ial cueing refers to the spatial layout 

of the typographic material, e.g •• juslification of margins, line spacing, etc. Advances in COIIlpllref 

technology and wOld processing provide us wilh new tools such as full justificalion of typogillphic 

material, Which improves reading speed CODSidaably as compared to an im!gular margin (Campbell, 

Marcbetti and Mewbort, 1981). 

113 
Chapter Se11en 

7.22 The Sentence, tbe Word and tbe Letter 

TI1e arrangement of print on paper supplies information about sentence, word and paragraph boundaries. 

E7ery printed language has conventions familiar to readers, and disruption of reading results when these 

conventions are violated (Haber and Haber, 1981). This finding suggests that readers routinely use print 

arrangement as a source of visual information. In addition to the co11text, the shape alone of the word itself 

may prove to be useful in word recognition! identification. Carroll. Davies and Richman (1971) 

demonstrated this using very high frequency words from text (e.g.; "the," "and," "it"). However, when 

the text is presented in all capitals, little or no word shape information is present, indicating a waste of 

an information resource. Since words are basically composed of letters, each of which has a distinct 

identity and name, a part of tbe visual information in reading must include the vi..snal features of tbe 

individual letters of the alphabet. Based on the feature description models, the entire English alphabet can 

be described by a total of eigllt feature descriptions (Haber and Haber, 1981). Type faces like Helvetica 

have no irrelevant features for visual processing wbere as type faces like Tm1es have redundant features 

like serifs which need additional proces3ing. 

73 DWORMATIONCO~ 

Information content refers to issues like ongm, appropriateness, accuracy, completeness and 

comprehension of both textual as well as graphical information. The workcard designer has to understand 

the way in which information on the workcard is going to be used and the influence it will have on user 

strategies. Two of the more important issues in this area concern the appropriate infonnation content and 

the presentation of graphic information. 

7.3J Appropriate Information Content 

To reduce and eliminate user strategy biases and consequently improve tbe usability, tbe information 

should incorporate tbe following qualities (Swander and Vail. 1991): 

• It should be accurate. 

• It should be complete, including information regarding: What is to be done, where, how, 

in what sequence, which specific items to pay attention to. 

• It should be up to date with revisions and updates. 

• It should be easy to use and comprebend. 

• It should be written in a consistent and standardized style and syntax. 

• It sbould be clear and unambiguous. 

• It sbould be specific and contextwil, e.g., pertaining to tbe particular aircraft being 

inspected. 

• It should be flexible. i.e., to suptmt botll the expert as well as the novice user. 

• It should use only approved and proper acronyms. 

• It should have logical and uncontradictory statements. 

114 
7 .3.2 Graphic Information 

Plain text can be uninviting to read and can, at other times. involve high wgnitive costs of intezprl't.ation. 

The same objective can be achieved at lower cognitive costs by use of grm;.Jlic information provided that 

the graphic infOl'lllJitlon is designed and presented in an appropriate IIIWI!::Z:. A1 times textual .information 

becomes difficult to comprehend, especially when conveying spatial infonnation. In such case.>, ,p;>hic:s 

can present the information more clearly. However, high fidelity graphics can involve high coglktiv<; .:osts 

of interpretation and may have negative effects due to clutter. Hence, items not relevant to the t.>sk st;•Juld 

be eliminated to avoid clune:-. 

7.4 INFORMATION ORGANIZATION 

'The primary rule of information organization is to classify information into relevant and clearly 

distinguishable categories (Sutton, 1991). Another imponant issue is the flexibility of information usage 

so that information can be used by bolh tbe novice as well as the expcrt. This aspect of information usage 

bas led to tbe concept of infornlation layering explained in the following sections. 

7 .4.1 Oassif'"IClltion of Information 

Information in any workcaid can be clearly classified as: directive information (proceaares and medJods 

for achieving certain goals), references to additional information, warnings, cantions 800 notes. These 

classes of information should follow a standard prioritized order "~~.ithin the OOcument itself, e.g., warning 

should precede cautions and notes. Since directive information forms the major portion of workcard 

information, it is explained below in more detail. 

Inaba (1991) suggests that directive information should I!Ot include more than two or three reliJted actions 

per step, keeping in mind the limitations of the human short term memory. All dhective information can 

be broken into three logical parts: the command verb, tbe objects, and the action qualifier. 1be command 

verbs used should have no synonyms, to reduce the level ~f ambiguity. The objects need to be broken 

down into further subgroups to prevent action slips. The action qualifier should be dib'tinct from the other 

two, and may begin with a standard article like "for. • Given below is the generic format plus a specific 

example of the three sub-groups differentiated by typeface: 

Generic Form 

Command Verb: 

Example 

-Object 1 

-Object 2 

-Object 3 

for action qunlifier 1. 

action qualifier 2 

and action qualifier 3 

115 

Check: - all hydraulic lines 

- control cables 

-pulleys 

for wear. fraying damage and 

corrosion 
Chapter Seven 

7.4.2 Information Layering 

A novice inspector may require elaborate information at every stage of inspection for an action qualifier; 

an expert, on the other hand, might require brief information. The information organization should be such 

that it caters to the needs of both. The prime goal is to make the information more flexible and more 

context sensitive (Jewette, 1981). 

Multiple levels can be built into t.'le information organization, for example, having the main ideas at the 

f"rrst level, followed by elaboration of each of the main ideas at the second level, and finally detailed 

descriptions at the lowest level. A numbec of methods can be adopted for presenting multi-layered 

information in hard copy format: use of distinctly separate layers (e.g., a checklist followed by a detailed 

information sheet); indented paragraphing (Jewette, 1981); use of color, graphical anchors or boxes; use 

of different print sizes and styles; use of symbolic nomenclatures, e.g .• • A, • "B," "1.1," etc. Also, at the 

lowest level, other tools such as italics, boldface, underlining, brackets, footnotes, appendices, etc., can 

be used 

In addition to the obvious advantages to the user in tenus of flexibility of usage, multi-level writing bas 

some distinct advantages to the writer. It is easy to write, as it bas a preset framework within which to 

write. It is less dependent on fancy phraseology. Sequencing and rearranging of information becomes an 

easier task, with less planning requirements. The amount of redundancy in the information too is 

considerably lower. Finally, multi-level writing involves the use of explicit statements of intenl:ion in a 

format dictated by the framework and is hence less error prone. 

7 .4.3 Other Organizational Issues 

Ideally speaking, both text and graphics should be presented on the same page or facing pages, but for 

reasons of cost effectiveness an;} system limitations this may not be feasible at all times. The page size 

should be treated as a naturally occurring module withln a document, i:l the physical sense, i.e., care 

should be taken to see that each page st1rts with a new task and that tasks do not carry forward across 

multiple pages). Each module bas all the information necessary to achieve a goal (i.e., completing a task 

or subtask). Tims, the inspector does not have to read across multiple page:; !" assimilate the information 

needed to complete the subtask. The information should be organized ~C<Jrding to a rational task order, 

which may either be the most rational way of doing that task or may be the order followed by most 

inspectors, due to practical reasons discovered during workcard usage. 

7.5 PHYSICAL HANDLING/ENVIRONMENTAL FACTORS 

A workcard which satisfies all of the above principles of infomllllion design but ;s not physically 

compatible with the task at hand will be of little use as people will be reluctant to use it Handling and 

usage is a critical factor and will remain so even with automated job-cards using pen-based or laptop 

computers. Providing a simple workcard holder can at times solve tl>ls problem. Depending on the tast, 

however, a specialized design of a workcard holder may be essential to improve the usability of the 

documentation. 

116 
Design of Wol"kcan& 

Non-compatibility with the working environment can encompass a number of factors: 

• 

• 

• 

• 

• 

physical handling difficulty due to unwieldy size 

excessively heavy, cannot be held oontinuously 

environmental degradation due to wind, rain and snow 

incompatl"ble with the other tools used ln the workplace, e.g., lighting equipment, hand 

tools, etc. 

impropec lighting conditions, need for a localized reading light 

7.6 SUMMARY AND GUIDELINES 

This taxonomy which is comprised of four basic issues that address the human factors concerns of 

information presentation (Sections 7 2 to 7 .S) provides us with a framework for design of usable 

documentation. This framework is generic and can be extended to a set of guidelines for design of paper· 

based documentation for aircraft inspection tasks as discussed below. 1be guidelines in Table 7.1 attempt 

to summarize the issues brought out ln the previous sections ln the form of assertive and usable 

statements. 

Table 7.1 Guidelines for Design of Paper·based Documentation for Aircraft Inspection 

1. INFORIIA110N READABILITY 

a. Typograp!lic Layout J 

1. Resort to usa of prim&IY lypojpphic spatial cuss like vertical spacing, lataral positioning, paragraphing and 

tt.cing positioning as much as possible. 

2. If space usege is p18111ium, tll8ll resort to usa of secondary cuaings; e.g., boldfacing, italics, underlining, color 

coding end capital cueing in a decraasing on:lar ot p111fllranca. 

3. Usa lull justificalian of the lllx1ual mal8rial. 

4. Usa a consistant typographic layout llvoughout the documanl 

b. Sentance, Word and l.alllor I 

5. Use of santanca 01l1111Cntions: 

• Bound&IY conventiOIIS 

• initial cepitalzation 

• final puncluation marks • <Odla spaoa 

• quaslion mlllk at end of question 

• exclamation mask 

• Oiract speech conventions • cp>lalion mallcs 

• pamgraphing for change cl speal<ar 

6. Uoa of word conventions: 

• Do not ,_ al CIIPilals lolllllll, .,.. bclh UP!* and lo-cue. 

• Hyphen incic:alaa word clivilion at end of ina . 

• st-e bafoN and-word. 

• Initial capitlolzation for Pft!PIIf nouns. 

7. Uoa cl l*r ccxw.~tions: 

• Usa a typalac8 lilot Hehoolica !hat has no nKiundant f<ialuiiiS. 

• Avoid using a genaric dllt-matri>c typeface. 

117 
Chapter Seven 

Table 7.1 Guidelines for Design of Paper-based Documentation for Aircraft Inspection cont. 

c. Printing Qualily S1andards I 

8. Develop end implement -n:ls for changing printsr nbbons, toner boxes, etc., to ansu111 a consistent print 

quafcy at an times. 

2. INFORMAOON CONTENT 

a. Appropriats Ccntsnt I 

9. Information proviclacl ohoulcl be supportiva of the inspecto(s ~nal goal to 'RiBd quicfcfy and alsc unclerstancl the 

inlonnaticn', to ansunt its usage and eliminate pelliCRIII biases. 

10. II should have carlain consislllnt and ccmmon elements to foster ganarali:zatians across ccntsxts. 

11. It shook! be accurate. 

12. It should be cornplet<>, i.e., it shcKMI inclucla information ntgllllling what is ID be dona? Whe111? How? In what 

on:larlsequenca? Which spac:ific Ianna to pay - ID? RelelllnCIIa ID additional sources of information? 

13. II should be up-- with ntVisions and upda!Ds. 

14. It should be easy 1o usa and CIDIIIJintherxl and hanCOI should be dear and unambiguous. 

15. It should be specilic end contextual, i.e., pertaining to the particular aircraft being inspectsd. 

16. II should be wrlll8n in a consislant and -..u.d syntax. 

17. II should be ftexibl& lor bolh a:cpart as wan as IIOYice inspaclors. 

18. Elimina19 usa of all illogicsi and salt cantnodiclory sialllmenls. 

19. Usa only certain approvad IICRiriY'I1S and proper nouns and provide a glossary if csikod lor. 

20. Toy to achiew a balance belwaan llllwily, elaboration and !GWn<lancy of information. 

b. Graphic lnfonnatian I 

21. All spatial inlonnation is to be pllisantad in graphicallonnat Avoid usa of textual lonna! lor p111senting spatial 

information. 

22 The tsxt should assist lhe gmphics and not vice versa. 

23. Avoid usa of high fidelity graphics to efiminats duttar. Simple f11e dlliwings are superior in most cssas. 

24. Usa a consislant format lor figure layout and numbering. 

25. Usa ordinary numbers, e.g., fina 1, 2, 3, ate., whan relarring to figures and avoid usa of compficsllld releranca 

numbers, e.g., T07-4032-Q01. 

26. Usa consistsnt lliew-<lireclion inlorma\ion, i.e., uss sillier the UP-AFT icon or the UP-FWD icon, not anything abe. 

27. The figure views should be as the i""""""" sees it, loom a fixed dislance/scale, e.g., 5 feet vi<lwing distance. 

Avoid usa of perspective part dmwings as figures. 

28. All figures end attachments sltould have back-references to lhe worlu:an:l pageltssk which originaily ralenad to the 

ligur&. 

29. Usa standard and correct technical dmwing terMinology, e.g., avoid uss of terms 'ssction' end 'view" 

intsrchangaebly. 

30. Use lypographic <fillerantiation ba-figure titles, psrt names, crack locetions, notss, eli::. This differentiation 

should highlight the irnpo-!hat one needs to sjva to each of lhesa, e.g., figura number, crack locetion, nola$. 

part names, etc., in <bcnlasing on:lar ol importance calls lor boldface cueing lor figure numbers. 

31. Use stenden:l drawing laycut conventions, e.g., location of sectional views with ralerenca to main lliews. 

32. Provide dillerent graphics lor spalially mimtr imaged tasks, to reduce the cognitive costs of image inversion, e.g., 

avoid usa of same graphics lor both left end right wing inspection !asks. 

33. Diflenontiate doss-up views fmm <istant views by giving apptapl'iats scsiing inlonnaticn. 

118 
Design ofWorkctlnls 

Table 7.1 Guidelines for Design of Paper·based Documentation for Aircraft Inspection cont. 

3. INFORMATION ORGANIZATION 

a. Classffication ollnlormation I 

34. Dislif9lish between diRICtive information, 18181111108 inlonnation, warnings. cautions. notss, procedu..,. and 

methcda. 

35. Thera should be a code for idontifying the importance ot a pal1icular cal8gory ol infonnalion over others, e.g., 

wamings, cautions, nol8s, procedu...,., IINIIhods, cillldlva infonnation, 18ferances in dacraasing order of 

imporlance. 

36. DiRICtive infonnation lhould be b-into the command verb (e.g., check), lhe objects (e.g., valves, hyd...,Jfc 

lin8S) and the acJion qualifiels (e.g., for_., ftays). 

37. Each chunk of ciRICtive information should not i-1110111 than 1M> or One nllabld actions par allop to oliminate 

action olipa (e.g., •........., 10 bella. ......,.... ..,.,..... ia accoplabla but 'check brakio valves, brakioo, ti..,. lnl Cllbles' 

is not accoplllble ao one clulk - c:aJJo for fur1hor bnoak down). 

38. The"' should be a dear cilfonmtialion between general and spacilic diRICtive in!onnetion for laslcs, e.g., ganend 

tasks usually cal for a less d1111iled inspeclion over a large but less cri- araa. 

b. lnfonnalion Layering I 

39. Prooride multiple levols of ilfonnalion to calar to the naods ot both axpart as wall as novice inspac!Drs, provicing 

mo"' elaborala infomultion for novices and mo.. ccncisa information for experts parfonning the """"' -. 

40. Davolop a slandan:l t.Mwo!k for distinguishing belwaan and writing multiple layaNd inlonnalion. Such a 

f...mework should eliminala clapandency on fancy phrasaolcgy for communication and piOIIicle a structu"' to wri1a 

into. 

c. Other Organizational ISSUIIS I 

41. The task infonnation should be ordered/S&qUIII1C8d in the natural order in which the tasks would bo carried out by 

most inspectors, e.g., according to the spatial location of the tasks as intemal tasks and extamal tasks. 

42. The page should act as a naluniJy occurring inlonnalion module, i.e., it should contain a fixed number ot tasks 

and avoid carryover of tasks acmss p&g8S. Each task that begins on a page should P"'ferably and on that page 

too. . 4. PHYSICAL HANDUNG AND ENVIRONMENTAL FACTORS 

43. The size of the workcard P89"" should be handy, e.g., avoid using large lllchnical drawings. 

44. The entire workcard should not be """""'""ely heavy. It should be such that it can be held continuously for an 

extended period by an avan~g~~ inspactDr. 

45. If the use demands expoou"' 1o environmen!al agents like wind, rain, snow or even harsh and oily floor oonditions. 

adaquate precautions should be taken to avoid excessive degradation. 

46. It should be compatibla with the othar IDols that an inspactor uses in the workplace, e.g., hand IDols, borosoopa, 

lighting equipment, etc. 

47. PIOIIicle a localiZJO<I N8cing light in poor lighting concilions. 

48. PIOIIicle a specialized WOikcard holder lD enable wiring in most positions. 

49. Provide slandan:l writing IDols (pans, pancils. etc.) 1hat anable writing in al positions, even against vertical 

ourfacas. 

7.7 CASE STUDIES IN WORKCARD DESIGN 

Aircraft inspection checks are scbeduled at periodic intervals, ranging from routine flight line checks and 

overnight checks, through A·, B- and C-cbecks, to the hea1'iest, the D-check. Among these, two extreme 

representative conditions were considered as demonstration case studies. 1be A-check is a more frequent 

119 
Chapter Seven 

but less detailed inspection, while the C-cbeck is a less frequent but more detailed inspection. The 

taxonomy for document design was used to develop workcards for both these inspection tasks. 

7.8. A-CHECK CASE STlfuY 

7 .8.1 Task Description 

The maintenance supervisor assigns the A-cbeck workcard to the technician. Normally two technicians 

are assigned to an aircraft, and inspection is canied out in the open, often under poor and varyitlg 

environmental conditions. Normally, the maintenance tecbnician completes a number of the inspection 

and testing tasks before begilllling work on reported discrepancies. The technician has to perform and sign 

off each of the 201 items mentioned in the workcard, in !be scheduled time. A sample page from the 

current workcard is shown in Flgu:e 7.1. 

03FEB92 07,51 WORK CONTROL CARD 

REV DATE: 09-04-90 MFG PIN: J07-3310-21-<l2.001 M&E PIN: 07-521+0017 

PAOC, AIC, 3200,1J7ZT, ATA32, IJ\Nl!oG GEIA 

·----·------------------------------------------------- .108 DESCRIPTION 'MECW *INSP' 

··------------------------------------------------------------------- ' 01 • TITLE: LANDING GEAR 

··----·------------------------------------------------·- • ATTACHMENTS: T07-3240-1.0001, T07-a:!-1-(l()()5 NJA N/A 

• ·-------------------------------------·------·------------· 

• 

• 

1. CHECK SYSTEMS CONDITION 

A LANDING GEAR AND WHEEL WELLS 

(1) CHECK FOR GENERAL CONDITION, DAMAGE AND 

EVIDENCE OF FLUID LEAKS NIA 

··---------------------------------------------------------- (2) CHECK FOR BROKEN ALDEL CLAMPS ON HYDRAUUC UNES IN THE WHEEL WELLS AND ON 

• THE LANDING GEAR ASSEMBLIES AND CHECK FOR CHAANG HYDRAULIC 

LINES. 

• NOTE: DISCREPANCIES IN THE ABOVE ITEM SHOULD BE CORRECTED PRIOR TO DISPATCH 

• OF THE AIRCRAFT. NIA 

··----------------------------------------------------- • 

• 

(3) CHECK BRAKE DEB00ST VALVES, BRAKES AND TIRES .FOR BEING WITHIN LIMITS. 

NOTE : SEE ATTACHMENT fOR PEX EFFECTED ,AQFT 'DE!!OOST\IALVE <CHEC«. N/A 

·-----------------------------------------------------

Figure 7.1 Sample Page from !be "Cuneln Wor.kcafd 

The maintenance technicians who perform the A-checks range in age from 23 to 55 years, with experience 

on A-checks varying between 1 year to 25 years. All 201 signoffs within the A-check can be classified 

into 18 subtasks, which fall into two general categories of tasks: "inspection tasks" and "testing tasks." 

The inspection taslrs are those of visual inspection, to ascertain conformance to predetermined standards. 

Testing, on the other band, involves determination of the proper functioning. Both inspection and testing 

can be further classified into "internal" and "external" tasks, depending on whether the task is to be 

performed on the interior or elttel:ior of the aircraft. 

120 
----------

Design of Workcards 

7.8.2 Methods 

Field "isits were conducted at various A-check inspection sites. These visits included direct observations 

of the task, observational interviews, and personal interviewing of inspectors (inexperienced as well as 

experienced), technicians, and supervisors. Inspector perception regarding workcard usability was obtained 

from various A-check inspection sites within the airline. 

7.8.3 Results 

The taxonomy for documentation design was used to identify the issues relating to the current workcard 

design for the A-check as JreSeDted in Table 7.2. 1bis case study demonstrates how such a taxonomy can 

be used to analyze existing documentation and points out the key issues that need improvement. What 

emerges from the inspector responses about workcard usage is a moderate level of satisfaction with the 

current workcard, but a number of users who need different information. There was a substantial 

agreement that the current ordering of information was incorrect and that the sign-off procedure was not 

performed after every step. Table 7.3 summarizes the conclusions from inspector responses. 

This study indicated that the technicians had strong views and were willing to report them when given a 

formal opportunity. An analysis of the task sequence preferences obtained from the inspector responses 

was undertaken. Based on these responses, an optimal task sequence was developed, which again is in 

agreement with the four basic task divisions of the A-check (inspection/test, intemallexternal). 

7.8.4 Workcard for A-Check: Proposed Design 

Based on the issues identified in Table 7.2 and the taxonomy, a design for the workcard for A-checks has 

been proposed. This design comprises two parts: the design of the information! paperwork, and the 

design of a workcard holder. The proposed workcard for the A-check has a two l<:vel hierarchical layering 

of information, as discussed The top level is in the form of a checklist (Figure 7 .2a), with brief task 

descriptions for each of the 201 signoffs, a place for the signoff itself and comments. 1bis is the part that 

forms the work completion document. At the lower level is the detailed information in the form of a 

bound copy (Figure 7.2b), whicb remains the satne until a new revision or update comes up. The directive 

information is broken into the command verb, tile objects, and the action qualifier as illustrated. Note that 

identification information, rarely used by the inspector, is located on the far right. 

A design was proposed for the workcard holder using the issues of Table 7.2 under the heading of 

"Physical Handling/Environmental Factors." The top layer holds :he checklist portion (19 pages) which 

can be clipped on every time before goiag out for an inspection, and the inner compartment holds the 

detailed ittformation sheets, which remain in there until revised. The top layer opens on a hinge which 

houses a srnilil reading light to allow rea!ling in poor lighting conditions. The holder also has paper 

retainer clips which aid usage in windy conditions. The prototype is shown in Figure 7 .3. 

121 
Clulpter Seven 

Table 7.2 A-Check Workcard: Issues Identified Within the Taxonomy 

f. INFORMATION READABIUTY 

A. Typographic Layout • no consistent typographic layout 

• layout clscontinuous, braeks within pages 

• no usaiJII of oecondary typographic aJeing. e.g., boldfaca, ell:. 

• no u• of lull juslficaliM of typographic material 

B. S..ntsnce, word, and let!IOr • non-contonnability with printing canwnlions 

• use ol al capitals lonna!, IUUlting in a low ..ading opead 

• use of a 5>(1 clot matrix typefaoll, h.,os no choice of any standeld ~ 

2. J..,;:-~RIIIATION CONTENT 

A. Appn:pria18 contant • 101M -18Cy in ... infonneliCMI 

• ;ooa,.,-iooloooMiion lor C8il8in lliSks 

•language ~to .... end compnohend 

• ¥llilr nol-.dZIOd 

• ciNClw inlonnalion ... biguous 

• geneoalizalion IICIOU llin:ndt types is a cau• of c:on!usion 

• not flexible lor use by both novice and -ot i""f'"C'Dr.i 

• use of dilficuR acn>nyms 

•lo{j<:al-rs and contmcictory -~~ • nodundancy end !8J)8tition 

• not consistant wilh user training 

• does notloolar IJIInsoalizations IICIOSS liislcs, as """'Y !ask is 

descnbold cille...,tly 

B. Graphic Information • system unSippootive of graphics 

• spatial inlonnatian conveyed llorocqo leX!, IUSUits in !!o<l use of 

complex end konglhy sen-which ... clllicult to compoahand 

3. INFORMATION ORGANIZATION 

A. lnfonnation Classifi<:alion • no C818garizalion or classilicalion of lliSks 

• nol8s, cautions, melhods, clin>e:ions, ell:. not in any priooHized order 

• no deoooaft:alion - dhaclive infonnalion, 18feoences, notes, 

mGOihods. etc. 

• clnoctiw infonnafion is not booken up iniD command veob, objects. and 

action qualifiers 

• cl-inlonnalion incluchs more than two or"'""' oalaltd actions 

per step 

• geneoal as wall as specific inlonnalion chunkad togather 

• _,.,al as well as inamal lllsks not pmpeoty demar::atod. rnblad 

B. lnfonnation Layering • no layering of inlomoalion 

• not concklcive to axpart as ...,. as novice usage 

• clllic:ulty in writing such unstnl<:lunod infonnation 

C. Other organizational issues • no use of naturaly OCQOrring p111J11 rnou'ules lor fitting in inlonnation 

• impmper SllqiiM!Cing ollallks 

4. PHYSICAL HANOUHG & ENVIR. 

• physical handing difficult duGO lo <mwiel<tf sia 

• excessively heavy, cannot be held continuously 

• usage in extoame envi101V11911ts diffiCUlt 

• not compati>le with the olher lools used along with, cllring the task 

• inadaqualllliglting conditions 

• no holder or~ for holding the ""'""card whils usage 

• all - factors forca lhem to carry out !he extemal inspaction 

without the woofo::aod, llllying only on mamooy 

122 
.,1 

I 

Design of Workcllrds 

Table 7.3 A-check Workcard Usage: Inteq>retations of Inspector Responses 

. Q.No. lnierprelalion 

1. • 66% of the inspaciDrs find the prasent workcald a useful soun:e of infonnation. 

2. - 60% of the inopactors nafer fo Ifill wortcard while doing Ifill A-chac:k, either usually or always. 

3. - Most people feel that the raadabilily of the curnant workcan:l is either lair or good. 

4. - Thena is no unanimous opinion amongst the inspectors, as to whether they pnafer a concise 

or dr;lailed workcard. 

G. - Almost half the inspectors pnafer a smaller size workcan:l, while the other hall feelthet the 

curnant size is about right 

6. - Most inspactDrs lasl that the infonnation provided on lha workcan:l is only IOIIII>timas 

suffic:m1t 1o cany out the A-dlack !ask. 

7. - Almost 50% of the inspsctors faal that tha curnant workcard is moderalllly aasy to 

undelstand. 

8. - Most inspactDrs face problams either sometimes or always in physically using lhe workcal<l 

while working. 

9. - 65% of the inspectors do not carry out the A-check activities in Ifill same way as listed out in 

the workcan:l. 

10. - 80% of the inspsctors say 1hatlhey have fek 1he need for mono information that was not 

provided on the workcard, either sometimes or always. 

11. - There Is no unanimous opinion amongst the inspsctors, "" to whether they usa 1he A-check 

accountability list provided altha beginning of the curnant workcard. 

12. - 50% of the lnspsctors sign off the complellld tasks on the workcard at lhe and of 1ha en im 

inspection. 

S./1 Description PI Slgnolf Com-t 

A Landing gear and wheel wells - - -- 1. General concfllion, damage, fluid leaks 5 

2. Whaei walls, landing gear assemblies, hydraulic lines 5 

3. Brake cleboost valva limits 5 

4. Brake limits 6 

5. Tinls, lor wear, damage, fluid leaks II 

6. Nose -1 cap aliached boks 6 

7. Nuts lor bottoming of last lr8ad 7 

8. Shock struts lor. normal extension, general condition, leaks 7 

B Tire p....ur. check - - - 1. Tinl pnassuna 7 

c Main gear doors - - - 1. Doors, operating cable, cranks & arms, general condition 8 

D Main gear wheel well down lock viewing windows - - - 1. Indicator stripes for clarity and legibility 8 

~•gu.re ·1.:.~.a YIDposeo uestgn ror A- worKcaro: st 

123 
Chapter Seven 

-------------------------------------------------------------------------------------------- 2A&B LANDING GEAR (Nose & Mtiin} 

Check oystarns condition 

A. Landing gelll' Md Wlletf ...... 

(1) Check: ll"""ral c:andtion damage and avidence of tluid laaks 

(2) ChBCk: • """"' Willis 

·lancing gear """"mbliea 

• chafing of hydnwlic ~-

lor broken aldal clamps on h]lllraulic lines on lhe 

Note : Diocnopancies an lha -· ibm must be 

conacted prior to lha dispatch of 118 ain:hlft. 

(3) ChBt:/c:. Brake daboost valves 

lor being wilhin limi!s 

Hoi&: See attachmant for PEX elladllcl ACFT debooal 

valve c:hec:k 

Wodr 

Conttol 

Cturl: 

Landing 

a..-

SC1CIAAC 

03Fflb92 07:51 ,., dale 090490 

No. 02189 ftiFG PIN:./07 

3200-21..Q20.«11 

Prot;, AIC 3200, B727, ATA32, 

M&EPIN: 

07.0SZ1· 

HJD77 

~5 

·---------·-----·-------------------------------------

Figure 7.2b Proposed Design for A-Check WorkcarQ: Detailed Information 

124 
Design ofWorkclutfs 

7.9 C-CHECK CASE STUDY 

7.9.1 Task Description 

A typical C-cbeck workcard consists of seven item groups. Most items refer- to attachments which must 

be procured prior to inspection, these being figures to be referred to during the tasks. Unlike the A-check 

which is performed by just one maintenance technician (overnight), the C-check is a task which extends 

across shifts, involving a number of inspectors, working simultaneously on various tasks. The C-check is 

usually carried out in a hangar, unlike the A-check: the task lighting does, however, vary depending on 

the task. The time scale is typically not as short as tlJat involved in an A-check. 

The inspectors performing C-checks range in the age between 25 to 60 years, with a 1 to 35 years of 

experience on C-checks. Also, since only a portion of the C-check task is given to an inspector at a time, 

inspectors are expected to perform different portions of the C-check at various times depending on what 

has been scheduled for them. This demands a total expertise on all tasks, but with some time elapsing 

between repetitions of a specific task. Considering the number of tasks involved in a typical C-check, it 

was decided to analyze and demonstrate particular portions representative of most inspection tasks. After 

discussions with inspectors and supervisors, two tasks wer-e selected for this case study: Left Wing 

Inspection and the Right Wing Inspection. 1be current C-check workcard is very similar in layout to the 

A-check workcard shown in Figure 7.1. 

7.9.2 Methods Used for the Study 

A field visit was conducted at a C-check inspection site. Visits included direct observations of the left 

and right wing inspection VJsk, observational interviews, and personal interviewing of both experienced 

as well as inexperienced inspectors, technicians, and mpeivisors. Inspector perception about the current 

C-check workcard was obtained from all C-check inspection sites within the airline. 

7 .9.3 Results 

The taxonomy for documentation design was used to identify some of the issues relating to the current 

C-check workcard as presented in Table 7 .4. The information readability and organization issues are very 

similar to those for the A-check. The information content issue, however, is different as far as the 

requirements of graphic information are concerned. Table 7.5 summarizes the conclusions. As with the 

A-check, most C-check inspectors seem to be troubled with the issue of information content, pointing at 

a scarcity in the information and need for more and better quality graphic information. As far as the issue 

of information organization was concerned, mos1: users felt that there was no clear differentiation between 

general and specific infoonation. 

125 

•. :.; :'' 
Chapter Seven 

Table 7.4 C-Cbeck Workcard: Issues Identified within the Taxon11my 

1.1NFORMA110N READABIUTY 

A Typographic Layout • no consistent typographic layout 

• layout ciscontinuous, breaks witlln pages 

• no usage of S&CXIndary typographic cueing, a.g. boldface. etc. in both text and graphics 

• no use of lull justilicalion of typographic material 

B. Sentance, Word, and Lelt8r • non-conlonnabilily with some of the printing conventions. 

• use of all capitals folmat IUUiting in a low .-irlg spMICI 

• no 100m lor selecling !Ill appropriale typefaea 

• use of a 5x7 dot matrix typefaea 

2. IHFORMAllON CONTENT 

A. Appropriate contant • -level of inal:cuiiiCY in""'·-

• inccmplate information for C811M!Iasks and lack at informalian en spatial 1ocaticn 

•language cfollicult 1o ...., and compnhend 

• synlliX not standsldzild 

• dimc:live lnlonnation ambiguous 

• ge.~elllfozaticn across ain:lllft types is a oause of confusion 

• use of dillicuR acmnyms 

•losjcalerrors and contnllic:tory -ants 

• radundancy and nopeli!ion 

• does not foslar generalizations QCIDS$1asks, as ewry 1aSk is described ciffe11111tfy 

B. Graphic lnfomtaticn • no figu111 numbering, ewonlhough lha ~ raters to opacilic figu111 nurnbefs, 

• fosters guessing and speculation for intarprelalion 

• no consistent layout at figui8S, use of a mixed layout and no doman:ation 

• no consistency in view dimclional infonnation (e.g., U$8 at bot> UP-AFT & UP-FWD) 

•IIOIHlOillexiUa ligulll views, or views as lha inspll(:lor-it, just ~ pert 

dlawin;s 

• no lnlom!alicn ID aid spatial location of palts 

• nc back nole<ancas lo 1M ,..,rkcard pageo'lask which 111fers lo lha 191111 • imptrlplw usage ofl8c:hnk:al dlawing 18fms (e.g., ._,. and "viaw" used intarchangaably) 

• nc typographic diff818111iation ~ figulll titles. part names. cmdllocations. 

notes, etc. 

• no use of standsrd dl1lwing conV8111ions (e.g., locelion of sedional views) 

• same gmphics for both left and rilt>t wing 1&sks, mentally inverting the figuROS 

causes hi!#! cognitive -rtdoad 

• some figu"'" use high lidelity QRIPhics, causes confusion and cluitlor 

• no ccnmstency of scaling in QRIPhics, dose up views not-from .distant views 

3.. INFORMAllON 

ORGANIZAllON 

A. Information Classification • no catagorization or classific:ation of !aSks 

• notas, cautions, methods, directionS, Oilc. not in any prioriliad order 

• no demarcation '*-n dinactiva infannalion, l1lfenlnces, notas, m81hcds, ate. 

• diRICtiva information is not brobn up into command Y8lb, objoacls, and action qualifiers 

• <iiiiCiive informafion indudes rno111 titan I'M> or fllrea related actions per step 

• both general as wei ao specific information c:hunklld together 

• general and specific-.: not properly cleman:afad 

B. lnfomtation layering • no laysring of inlonnalion • net concluc:ive to axpert as well as novice usage 

• dilticuRy in writing such unstruclunKI inlormation 

C. Other organizational issues • no use of naturally occurring page modules for fitting in information 

• improper ~cing of -.: • no consisl&ncy in lha number of signoffs across lha -

4. PHYSICAL HANDLING & • size of the attachments <ifferant from tha wodc:card size, causes inconvenience in usage 

ENVIR • inadequate 6ghting con<fotions in certain »olk amas 

• no holder or place for holding lha -rkcard while usage 

126 
Design of WorkeanLr 

Table 7.5 C-Check Workcard: Interpretations of Inspector Responses 

Q.No ln ... Pflillllan 

1. • 48% of lhe inspec:IDrs find .,. P"'""nt woikcard a UOIIfuloouiCil of infoomdon. 

2. • 93% of the inspaclors ~&fer ID the """""""' while doing the C<heck. eilher uoualy or always. 

3. • 4<!% of 1he people fael1hat .,. ..adabi!ily of 1he CUinll1l wodu:aod is ....., t.ir G< good. 

4. • Th<o"' is no unanimous opinion amongst l1e insper:.an, aiD..,._,. tNy......, a c:oncile or 

detailed woikcard, 55% of.,. people plllfor morB detailed illonlolllon. 

5. • 75% of the inspac:..'Oia fHI 1hat the physical size of.,. a.omont -':aiJd is eout 191t 

6. • 42% inspectors INI1hat the infarmalion pnMdecl on IN wodu:aod is -lllllic*ot ID cany om 

""' Cchecl< Wk. 

7. • 40% of toe inspeciDrs IMI1hat th& a.o....m wootu:ard is""' '*allly ..,.ID Wll»>oland. 

8. • 60% inspectors faced pRIINms IOIMiimes in physically using .,. wodald while .,. ramainiog 

WIIIB equaly divided in 1heir views. 

9. • 33% of 1he inspec:IDrs do nat cany out toe C-c:heck actilliliGa in .,. 1811111 way M lisllld out in 1ha 

woikcald. 

10. • 98% of toe il~ at loa! they haw 1111 the need .,, mol& inlonnalion 1hat was not pnMdecl 

on toe -'<cald, ei!har aometimoos or always. 

11. • Thel8 is no unanimous opinion amongst th& inspiiCID!s, asiD _.,.,a..,. ,_ 1ha ~ 

IICCOUillabolity list pnMdecl at l1e beginning of 11M> .::unnt woikcard. 

12. • 42% of 1he inspaclors left that """" ....,,., IDo many signolls on the cumont ~ but 30% felt 

lhat1hel9 -too few. 

13. • 88% of tha ins:>SC(Drs had missed noticing wookt:ait! ~&visions....., SOIIIQiimes or d least on . soma 1818 occasions. 

14. - Only 32% of the inspectors li!Jtotf each compleled l:lst inciWloaly a.'llr it is daM. 

7.9.4 Workcard for C-check: Proposed Design 

The issues highlighted by the inspector responses and tbose identified io Table 7.4 were used to produce 

with a demonstration design for the left and right wing inspection tasks of the C-cbeck. Unlike that of 

the A-checks, the workcard for the C-check calls for a single layered design with an additional set of 

figures and graphics in the form of attachments. Figures 7.4a and 7.4b show tile proposed design for the 

left wing inspection task. Witbin the main workcard itself (Figure 7.4a), information is organized in a 

format eDCOmpassing three tasks per page, each task desa.ij)tion consisting of two parts, graphic :md text. 

The graphic is an iconic representation of the wing with the loa.tion of tile body stations at which the task 

is to be carried out. The text part is the directive information, broken up into the rommand verb. the 

objects and the action qualifier. 

Figure 7 .4b illustrates the basic layout for redesign of the gr.q:;bics attacbments. It ccnsists of an 1conic 

representation of the wing in the top right comer with the location of the task ro be carried out. Also 

shown are the body stations and a footnote containing the di.-ective infonnation from the workcard. 1be 

directive information refers to that particular figw-e and the page number on which it appears. Even 

though there is an attachment number, each figure has a single digit figure llU1Ilbe£ for ease of referencing. 

The actual figure is a low complexity graphic representation of the portion being inspected in a view as 

the inspector would see it, rather than the isometric part views as presented in the existing attachments. 

Use of typographic differentiation between figure titles, part names, crack locations, notes.. etc., is also 

127 
included A consistent scale has been 

used for all primary grapbics, USing a 

viewing distance of around 4 to S feet 

from the inspector. Also, different 

figures are provided for both the left 

and the right wing inspection tasks, 

unlike the present attachments which 

use the same figures for both. This 

allows proper body station number.ing 

on the figure and also beJps in 

reducing the cognitive workload of 

having to mentally invert the figures 

before interpreting them. 

7.10 FIELD EVALUATION OF 

PROPOSED DESIGNS 

FOR C-CHECK 

WORK CARD 

UJT'Bfi:I'ISIECIJOl'l 

Z.Cioork ._. ... - .. 

c.Qooll;;w.ca .... sor• 

--paotioaorlloo __ ...,_ l':!:..;._J 

llcWwllo-oiporllo- .. 

--... ..-or.-

_.,_4&Sk--or- .-("IUS-S110.1-ID!Il 

1Cioork --bllltilllmtaf'...W .... --.. 

- -Y-6.s..--or-

_..(11lS$110.l-lllllt) 

-------- !!..!!!P.e 

·-----

LQodc·-

·- ........ 

... BbwEtmal .-.---- bspl . . . 

To test the validity of the issues Figure 7 .4a 

identified and the proposed taxonomy. 

C-Check Workcard: Proposed Design 

an empirical evaluation was caaied 

out with the airline partner to 

evaluate the proposed design of the 

C-cbeck workcard in relalion to tbe 

CUIIeDt computer-geoerated C-cbect 

workcard. 

7.10.1 ElqJerimental Design 

The eight inspec::tom used for this 

experiment were asked to perform 

two tasks from the wing inc;pectlon 

portion of tbe C-dleck. One of the 

tasks involved using the CUIIeDt 

computer-generated workcards and 

the other involved using the proposed 

design of the C-cbeck workcard. In 

all, four combinations of the 

workcard were used, one combination 

A.TJ'M;JG MIS 

___ 

f'II5.S7la.l.-l : .............. ....... 5 

..., 

I ... 

-

.,. \ ~ ~ 

~ (fic5) \x. ~-~ !60 

0.1 ( ]/~ "(0 ' ( I (t-A'-' X.:JS7 

C:Z.·tbo-,-oftbola-

_ ............ _ .... _ ... ., .... ___ far_ .. 

opo.&4-(ps5) 

-- .... -.. 

r:y !A ..L 

I nlo I I\ r OITIB_j ~ ~ ~ 

-- l '-typi:ol...t. 

.._ typio<l<*k 

-.... lrawU'J (lie 5) lrawl60(11c4) 

for the left and the other for the right Figure 7.4b 

wing inspection. Table 7 .fJ lists the 

C-Check Workcard: Proposed DesignGraphics Attachments 

order in which the experiment was 

carried out After each task the 

inspector was asked to rate the workcard used for that task on 14 issues, each relating to those brought 

out in the taxonomy. The sanie set of issues was used for both the tasks. 

12& 
••• _ ••• 0' 

Design ofWo7kco.rb 

Table 7.6 Experimental Demgn 

Inspector I Task1 Task2 

11 Current W/C - Left Wmg Proposed W/C - Righi Wmg 

12 Current W/C - Left Wing Proposed W/C • Right Wing 

13 Current W/C - Right Wing l'roposed W/C - Left Wing 

14 Current W/C - Right Wing Proposed W/C - Left Wing 

15 Proposed W/C - Right Wing Current W/C - Left Wing 

16 Proposed W/C • Right Wing Current W/C - Left Wing 

17 Proposed W/C - Left Wing Current W/C - Right Wing 

18 Proposed W/C • Left Wing Current W/C • Right Wing 

7.10.2 Results 

The inspector responses to the rating task were analyzed using Wilcoxon Matched-Pairs Signed-Ranks Test 

for two Related-Small Samples, since each subject acted as bislha" own control. Table 7.7 summarizes 

the results along with the average rated scores fur the current and the proposed wor' . .:ards. 1be results 

point in favor of the proposed design on each of the 14 points. One of the issues addressed the more 

general matter of whether separate attachments for b'le left and the right wing inspection tasks would be 

useful. Most inspectors thought that Sllch a fermat would be extremely useful. 

7.11 RECOMMENDATIONS AND CONCLUSIONS 

Both the A-check and the C-cbeck case studies showed that substantial redesign of the existing workcards 

is required. This is true whether they are to be replaced by new hard-copy workcards, or by a portable 

compute£ system. The taxonomy of documentation design presented here provides the framework required 

for investigating documentation in field conditions, using direct observation and user feedbllCk in a 

structured manner to develop improved designs. 'lbi; results of the in-field empirical evaluation of the 

proposed C-check workcards proves the validity of the methodology as well as the proposed taxonomy. 

At present, sample workcards are being prepared for other tasks by the airline partner to e11sure that the 

benefits are applied as widely as possible. 
Table 7. 7 Summary of the Results 

I.Polnt Rating Scale 

End-points 

Q,f · lsauo oddre11od 

0 I 

1 ReadabUity ot lheWDrtccaid Torrllle excotlonl 

2 Conllnully ot lnlonnallan tlow Torrlllo Excollont 

3 Ease of lnl<>nnllllon locallon VV'/ dllflcul Voryouy 

4 Chanco of mlsolng lnlotmatlon /Uwaya Never 

~ 

5 Eoee of undlrstandlng 'lory dilllcul Vorjeaay 

6 Ease of lcJCatlon.w.r.t. body·statlons Vwydllflcul Vorylaay 

7 Ease of relating figUre numkro Vorydntlcuft Voryouy 

8 . . Amount of lnlorma1lon provldld Too fktll Too much 

9 East of readabllll)i ot attochmento - T•niblo Poor .. 10 Relating graphics wfth wing atroc1ura Vory dllflcuft VtWY eaoy 

11 Cooslal!tney of preuntallon Ttrrllle Poor 

12 Compalbllty of altachmOIU with Workcaid Tarrllll Poo• 

13 Amount of g!IIPhlcto proWled on lho 8lleCIImenla Too 111111 . Toomuch 

14 . OVolllll ...., of ucaiiMity of lhe Workceid Terrtile Excolllnt 

CurnntW/C Propoood 

moon rllllna W/C mtl>l! 

(liD) mlng (liD) 

4.0 (1.2) 6.8 (0.7) 

3.4 (1.1) 6.0 (1.0) 

2.6 (1.0) 4.7 (1.0) 

4.8 (1.1) &.8 (0.8) 

2.7 (0.7) 5.8~~-!L. 

2.2 (1.3) li.5 (U) 

3.4(U) 11.1 (1.1) 

4.2 (1.8) 3.6 (0.7) 

4.1 (1.4) 6.4 (U) 

2.8 i0.9) . 6,1 (1.7) 

4.0 (1.4) 8.8 (0.8) 

3,7 (1.8) 0.1 (0.7) 

2.5 (1.0) 4.0 (0.6) 

:u (0.9) 6.8 (0.4) 

Wilcoxon 

lllllltclled f'oln 

Slgntd-«anka Till. 

p <O.OOS 

pcO.OI 

p <O.OOS 

p <0.G25 

pcO.OOS 

p cO.OOS 

pcO.OI· 

n.e . 

P<0.025 

p <0.026 

p < 0.01 

p <0.G25 

pc0.026 

pc0.006 

i 

~ 

~ 1: 
Design of Wo'*-'11 

7.12 REFERENCES 

Campbell, A. J., Marchetti, F. M. and Mewhort, D. I. K. (1981). Reading speed and text production: A 

note on night-justification techniques. Ergonomics, 24, 633-640. 

Carrol, J. B., Davies, P. and Richman, B. (1971). The american heritage word frequency boolc. Boston: 

Houghton-Miftlin. 

Drury, C. G. (1989). Information Environment in aircraft inspection. Proceedings of the Second 

International Conference on Human Factors in Aging Aircraft, 92-109. 

Haber, R N. and Haber, L R (1981). Visual components of the reading process. V"uible Language XV, 

2, 147-182. 

lllli!Ja, K. (1991). Converting technical publications into maintenance performance aids. XYZYX 

Information Corporation. 

Jewette, D. L. (1981). Multi-level writing in theory and ptaetice. Visible Language, XV, 1, 32-40. 

Prabhu, P., Gtamopadhye, A. and Drury, C. G. (1991). Human factois in workcard design: an initial 

presentation of the issues. Unpublislled technical report prepared for Galaxy Scientific 

CorporationiFAA/OAM. 

Shepherd, W. T., Johnson, W. B~ Drury, C. G., Taylor, J. C. and Berninge£, D. (1991). Human factors 

in aviation maintenance, phase I: Progress report. (Report No. DOT/FAA/AM-92/16). Springfield, 

VA: National TilChnical Iilformation Service. 

Sutton, I. S. (1991). Writing operating procedures. International Conference on HtJTJUd Identification 

and Risk Analysis, Human Factors and Human Reliability in Process Safety, 293-308. 

Swande£, A. J. and Vail, R. E. (1991). Building procedures for repeatability and consistency in job 

petfonnance. Intemational Conference on Hauud Identification and Risk Analysis, Human Factors 

and Human Reliobi/Uy v. Process Safety, 339-352 

Wright, P. (1991). Qua1ity: An excellent idea? Conference on Quality in Documentation. Centre for 

Professional Writing: U.K., 11-24. 

131 
Trtdning for VISual Inspection of Aircraft Structures 

Chapter Eight 

Training for Visual Inspection of Aircraft Structures 

8.0 INTRODUCTION: THE STATE OF VISUAL INSPECTION TRAINING 

Although mucb has been written about training for aircraft maintenance in the past several years (e.g., 

Shephe!"d and Parker, 1990}, very little applies directly to the acquisition and enhancement of visual 

i.llspection skills. Typically papers concern either the overall structure of training program (Skinner, 1990; 

Desormiere, 1990) or the technology of training delivery systems (Payne. 1990; Kurland and Huggins, 

1990; Goldsby, 1991; Rice, 1990). Visual inspection has skill, rule and knowledge-based components and, 

as such, is less amenable to rule-based diagnostic procedures. Such procedures have received widespread 

study in avionics (Johnson, 1990; Johnson, et al., 1992) and nuclear power (Kello, 1990) and can represent 

the technological leading-edge of training delivery. However, for visual inspection, visits by the State 

University of New York (SUNY) team to many airlines have revealed a relatively uniform approach. 

Training content is seen as either knowledge or skills, with knowledge imported in the classroom and 

skills through on-the-job training (OJT). Despite the overall effectiveness of inspection, our site visits 

have revealed a strong desire to find enhanced ways to implement visual inspection training. 

Examples of high quality inspection training can be seen in many airlines, but in all there is the same 

classroom/OJT split of delivery methods. 

• On-the-job training (OJT) is the preferred way of imparting training to new inspectors. Most of the 

classroom training targets pre-flight checks, non-destructive test (NDT) or orientation. One airline 

(Lutzinger, 1989) has such a program wbere 5% (approximately 15-17) of their inspectors are trained 

daily. They also have a program called C-3 under which. when a supervisor discovers an aircraft 

discrepancy missed during an earlier inspection, be codes this item C-3. These C-3 items are used to point 

out to inspectors what kinds of discrepancies are being mi•sed during aircraft checks. 

• An aircraft manufacturer has developed a "task analytic training system" model to address training needs 

for NDT (Walter, 1990). However, elements of this model are generalizable to visual inspection. This 

method consists of performing a job task analysis to identify training needs and job instruction training 

to impart knowledge. This methodology also emphasizes a team appmach to developing the training 

modules. A design team. an approval team. and a team facilitator comprise the personnel creating a 

module. An iterative procedure involving the work force is utilized. An annual audit assesses the status 

of each training module. 

• Another airline combines orientation training with on-the-job training (OJT). There is a new inspector 

orientation training called Q.C. transition orientation which lasts for 16 hours over two days. 1be 

inspector is then put on a 40 hour OJT at the end of which he/she is Required Inspection Item (R.Il.) 

certified. The airline has instituted an inspection research request program. Under this, inspectors who 

detect a problem with inspection procedures, workcards, documentation, etc. can submit a request to the 

quality control analyst for a review. In:.--pectors also have available information on inspection alerts that 

are generated by engineering. When a new aircraft arrives, Q.C. denotes one of its foremen as a training 

instructor. 1be training instructor visits the manufacturer Pnd gets information to set up a training program 

133 
Clulptu Eight 

for inspectors. Quality control then initiates traiDiDg for tlle wbole department to famlllarize lbem wilh 

the new aircraft 

There are, however, drawbacks to 1be classroom/OJT approach. These have been identified by proposas 

of simulation as a delivery intervention (e.g., Johnson, 1990; Lesgold, 1990; Kello, 1990) wbo show that 

classroom/OJT is not an optimum way to train. 

Shepherd and Parker (1990) recognize both the content and 1be delivery system as crucial to training. 

Content bas been defined for maintenanre in terms of knowledge, skills and abilities (KSA) sinre tlle 

Allen report in 1972. Currently, tbe KSA's for mainteamv:e are being redefined for Part 147 schools, but 

again there is little on visual inspection. A recent compilation of training research and practice (Patrick, 

1992) can be used to define 1be cum:nt status of training and the issUes involved. These lead to 

experimental evaluations of particular training interventions for visual inspection, which in turn provide 

the basis for enhanced training programs. 

8.1 CURRENT METHODS IN TRAINING: AN OVERVIEW OF RESEARCH 

Training design deals with the issue of translating training content into a training program. Patrick (1992) 

identifies training content, training medlods and trainee charactedstics as the three main components of 

a well-designed training program. Wilh the advent of computer ·based training (CBT) and mnlli-media 

approaches, we should add training delivery systems as another "'OIIponellt. 

8.2 TRAINING CONTENT 

Training content pertains to identifying the knowledge and skills neMed to paform the set of tasks that 

define a job. For example, Wirstload (1988) ld<mifies knowledge categories (e.g., layont knowledge). 

knowledge objects (documeDls, etc.) and deptb of knowledge as a way of identifying job training 

requirements. 

A systematic analysis of tbe task is necessary to identify tbe traiDiDg 0' nt~ Patrick (1992) classifies 

analysis techniques into (a) task-oriented analysis and (b) psycbological techniques. Task-oriented 

techniques use task-oriented data to derive tbe needs, objective and content of the training program. 

Examples are Task Analytic Training (e.g~ Walter, 1990), hierarchical task analysis, HTA (Drury, et al., 

1990), critical incidents technique (Flanagan. 1954) lllld task inventory (e.g., USAF Task Taxonomy, 

Christal, 1974). Psychological approaches typically use taxonomies that categorize aspects of the ta&k in 

terms of human motor/perceptuallcognithoe processes. lbis can help tbe analyst understand tbe 

psychological elements tbat need to be addressed (e.g., decision making skills, rellSOning, etc.) by specific 

training methods. 

8.3 TRAINING METIIODS 

Training methods deal with techniques that can belp transfer the training contents to the trainee in an 

effective man.'!«. Some of the common/popular methods (Patrick, 1992; Drury and GriUIIOpadbye, 1990) 

are discussed below. 

134 
Training for Visllllllvpection of Aircraft Stna:tures 

8.3.1 Pre-Training 

Pre-training provides the trainee with information concerning objectives and scope of the training program. 

Pretests can be used to measure (a) level at which trainees are entering the training program. and (b) 

cognitive or perceptual abilities that can be later used to gauge training perfwmance/progress. Advanced 

organizers or overviews, which are designed to provide the trainee with the basics needed to start the 

training program, have been found to be useful. The elaboration theory of instruction (Reigeluth and 

Stein, 1983) proposes that training should be imparted in a top-down manner where a general level is 

taught first before proceeding to specifics. Overviews can fultill this objective by giving the trainee an 

introduction to the training program and facilitating assimilation of new training material. 

8.3.2 Knowledge of Results 

Knowledge of the results is probably the most common and effective method of training. Drury and 

Kleiner (1990) suggest that baining programs start with rapid, frequent feedback which is gradually 

decreased until "working" level is attained Additional feedback beyond the end of training will help to 

keep the inspector calibrated (Drury and Gramopadhye, 1992). Gramopadhye (1992) classifies feedback 

as performance and prooess feedback. Performance feedback for inspection typically consists of 

information on search limes, search enors and decision errors. Process feedback, on the other hand, 

informs the trainee about the search process, i.e., areas not covered, inter-fixation distance, number of 

fnations. Research (explained in the next sections} supports the beneficial effects of process feedback on 

inspection performance. Another type of feedback called "cognitive feedback" has emerged :li:om the area 

of social judgement theory. Cognitive feedback is the information to the trainee of some measure of the 

output of his or her cognitive processes. It is suggested that cognitive feedback allows the trainee to 

perceive the error in their judgement as weD as why the judgement was in error (Hammond and Summers, 

1972; Doherty and Balzer, 1988}. 

8.3.3 Guidance or Feeclforward 

Guidance or feedforward provides the trainee with information prior to action, concerning how to carry 

cut part or all of the task. For example, an experienced inspector can tell the novice how he looks for 

evidences of corrosion in the cargo compartment. Guidance could be physical (for acquisition of motor 

skills), demonstrations, verbal advice (e.g., prompting), and cueing (telling when and what signal occurs 

in perceptual detection tasks). Feedforward can also be by informing the inspector what to expect in a 

certain area that he is going to inspect next. Feedforward should provide the trainee with clear and 

unambiguous information which can be translated into performance. 

8.3.4 Part-Task Training 

Part-task training constitutes partitioning or simplifying the whole task into parts and then teaching these 

parts to the trainee. Part-task methods are classified '~y the manner in which parts are practiced. Isolated 

parts training consists of learning each part separately for either a fixed number of trials or to some 

criterion, and then doing the whole task togetlter. <'rogressive part training teaches components of the job 

to criterion, md then successively larger sequeno:es of the components (Drury and Gramopadhye, 1990). 

Repetitive part training involves practicing one part. then parts one and two, then parts one, two and three 

135 
CluzpUr EighJ 

and so on {Patrick, 1992). In general, part task training his been found to be belleficial for complex tasks. 

Drury (1990) reported good results in induslrial inspection tasks when using progressive part training 

methods. 

8.3.5 Whole-Task Training 

Whole-task training involves the trainee on the task as a whole instead of breaking it into parts. Naylor 

and Briggs (1963) have postulated that for tasks of relatively high organization, as task complexity is 

increased. whole-task training should become relatively more efficient 1han part-task training methods. 

This is an intuitively appealing principle because as parts of the task become more interdependent the 

trainee might have a harder time integrating perfonna.t~~:e on the whole task if trained on part task. Wholetask training also becomes necessary when it is not possible to identify task parts having natural 

segmentation wilh relation to the task as well as the skills needed from the trainee. 

8.3.6 Adaptive Training 

Adaptive training tries to accommodate the cbaracteristics of the trainees. This method comes from a 

recognition that individual differences exist in the skills, knowledge, abilities and aptitude« 1hat trainees 

possess. Bartram (1988) bas reported a study involving operators at a post office. in which adaptive 

training methods were used to train the operators to sort mail at an avenge time per item of 1.8 seconds 

or less and error rate of less than 1%. Adaptive training involves measurement of the trainee's 

performance and making changes in the programlmethod as a function of the trainee's perfomlance. 

8.3.7 Active Tralllfng 

Wben the trainee his to actively discover information or cues. and make a physical response, learning is 

enhana:d (Czaja and Drury, 1981). A good passive tr;ining scheme, where the information is metely 

presented to the ttainee, Is often inferior to an equivalent active scheme, where a response is reqnired at 

each step. 

8.4 TRAINING DELIVERY SYSTEMS 

Training can be delivered to the trainee through a variety of media. With the .inaeasing use of computers 

and the advances in multi-media technologies, the choices in delivery systems are varied and tbe task of 

selecting one is non-trivial. We can classify training delivery systems under the following broad 

categories. 

3.4.1 On-tbe-Job Training (OJT) 

On-tbe-job training is a much maligned word in tbe area of training and much of the literature is full of 

exatnples of its inadequacies. While this is true, there is a case to be made for structured orr 

supplemented by adequate classroom instructions. This is especially true in cases where realistic 

simulators cannot be developed or are too expensive. 

136 
Training for VISual Inspection of Aircraft Structures 

8.4.2 Traditional or Convention&} Training 

In this system we have the traditional method of instructors tutoring to trainees using slides, blackboard, 

and paper and pencil methods. Further embellishments include using video and TV media anc! even 3-D 

projectioD.s (Rice, 1990) to ~lain instructions or provide concept training. Training aids can include 

prototypes or models of objects used in the actual task. AD the principles of training design can be used 

to varied extent in this system. In a review of training systems in the U.S. military, Orlansky and String 

(1979) found trainee achievement using conventional training and computer-based training about 

equivalent. However, with the advent of better and more powerful computer systems with higher quality 

graphics and computer-based training (CBT) methods thst utilize more training design principles, the 

balance might be tilting in favor of CBT systems. 

8.4.3 Computer-Based Training (CBT} Systems 

Training systems of this type are also called computer-aided instruction systems (CAI). Patrick ( 1992) 

identifies four main roles for computers in training: (a) provision of training, (b) development of tr&lning, 

(c) management of training, and (d) research in training. CBT systems typically are used to fulfill the frrst 

and third roles, in which the computer is used to present training material to the student and schedule 

him/her through various training exercises, recor!l progress, administer rests and provide progress 

summaries to the instructor. Boeing has produced a series of maintenance training CBT lessons on the 

767 airplane (Lukins, 1990). They are also investigating the area of instructCJr-led CBT used in a 

classroom environment. 

8.4.4 Intelligent Tutoring Systems (ITS) 

Computer-based tutoring sySiems attempt to create interactive learning environments in which the 

learner/trainee can carry out simulated tasks. Typically, an ITS contains (1) an explicit model of the 

domain, (2) an expert program that solves problems in this domain, (3) a model of the student that 

explains what the student undezstands, and ( 4) a tutoring model that provides instructions {Clancey and 

Soloway, 1990). 

SOPHiE-ill {Brown, Burton and deKieer, 1982) is an intelligent simulation training system that supports 

interactive training by estimating and responding to student needs. SHERLOCK (Lesgold, Lajoie, Bunzo 

and Eggan, 1992; Lesgold, 1990) is a practice environment for learning troubleshooting a complex device 

on the F-15 manual avionics test station. It analyzes inferred student models with respect to expert models 

and emphasizes refinement of mental models. 'The Integrated Information Management System (llMS) 

developed by the U.S. Air Force has imbedded training systems that include such features as multi-level 

representations for expert, novice and trainee, preview of little used tasks, and troubleshooting simulations 

(Johnson, 1990). The Environmental Control Sysiem (ECS) Tutor is an intelligent simulation that provides 

appropriate feedback and advice tc the student based on observed interaction (Norton, 1992). 

8.5 EXPERIMENTAL EVALUATION OF TRAINING INTERVENTIONS 

Combining tbe literature oa training for visual inspection with the demonstrated need for new techniques 

of inspector training, it is apparent that there are major issues in need of testing. Both visual search and 

137 
CluzpUrEight 

decision-lllllldng aspects {)f the task require assistance if we are to acbieve and maintain bigh levels of 

inspector effectiveness within a visually-complex. but often repetith-e. visual inspection task. 1bese is.."lleS 

can be classified as: 

• Visual Search Issues 

• 

1. Can training improve defect conspicuity? Specifically, can the visual lobe size be 

increased. and if so, does tllis increase generalize across different defects? 

2. How effective is feedback in cllanging search strategy? Specifically, should feedback be 

about the inspector's performance, or about the inspector's strategy? 

3. How effective is cueing or feedforwdfd in changing search strategy? Specifically, do 

inspectms perform better with genetal.izOO information or specific recommendations? 

Decision-Making ISS'.Ies 

I. Perception of multiple defect attributes: is an active training sclieme better than the 

equivalent passive scheme? 

2. Integration of multiple defect attributes: is an active training scheme better than the 

equivalent passive scheme. 

Note that these issues are ones suggested by tbe literature on industtial inspection, but untested in the 

airfratne inspection context. Note also that is..<rues have been cOOl!en which do not imply the need for 

particular delivery systems, even though the evaluation of each issue was carried out on a computer-based 

simulation. 

Each of the £ssues above defines a training intervention wbich was evaluated using a consistent 

me!hooology. Each test was aimed at detemrlning whether a particular intervention bad an impact on 

improved performance. Because these needed controlled con:litions, often with many repetitions of similar 

faults, actual airframes and inspectonl were oot logically possible. For example. the hundreds of cracks 

and dents required for the visual lobe training would nev« be available to an inspector. Thus, a visual 

inspection simulator was developed, using a SUN workstation computer to reproduce the essential aspects 

of the visual inspection task. 

In this task the inspector searches for multiple defect types and classifies them into different severity 

categories. The seven possible fault types are missing rivet, damaged rivet, poochedldished rivt.t, loose 

rivet, rivet cracks, dents and corrosion. 

The enlire inspection task is a series of search areas where each search area is that portion of the task 

which is shown on one screen. A part of the aircraft fuselage (one search area) is presented to the subject, 

whose task is to locate the fault in the search area and indicate its discovery by clicking the left mouse 

button on the fault. The layout of the multi-window simulated inspection task is as shown in Figure 8.1. 

The function of each window is as follows: 

138 
Training for VlSlUlllnspectitJn of Aircraft Struetures 

Figure 8.1 Screen of Visual Simulation 

1. Inspection Window. The area currently being inspected is shown in the left (large) window. To 

simulate tbe use of local lighting, such as a flashlight beam, only a smaller winclow within tllis 

area is fully l1luminafed. Within tbis smallec window, or "viewer", faults can be seen and 

responded to by clicking them using the left mouse button. The entire area of the inspeclion 

window can be viewed by successive movements of the viewer. 

2. Search Monitor Window. This is a monitoring device which helps the inspector keep track of tbe 

window movement in tbe inspection window. 'The viewec in the inspection window is represented 

by a tile in tbe search area window. As the viewec is moved, so does tbe tile, which bas a 

different color from its illnminatM background area. Tilt; darkest shade of the tile is tbe point of 

previous fixation so that tbe sequence is given by the shade of tbf: color -lighter shades indicate 

earliec fixations in sequence while darker shad~ indicate latec fixations. 

3. Macro View Window. This window represents tbe entire task to be inspected, and provides 

information to the inspector about his current position with reference to the entire task. 

The visual inspection simulation generates an output data file of subject perfurmance cousisting of both 

individual statistics for each search area, and summary statistics averaged over all search areas. Both 

perfoiJllance and process measures are collected. The performance measures include: tbe num"Oec of faults 

located, tbe time to detect each fault, tbe stopping time, the number of hits, misses, and false alarms, and 

139 
Chaprer Eight 

the average time spent in each search area's nine zones. lbe process measures collected include: the 

percentage of search area covered by the viewer, the number of viewer fixations used to search the area, 

the interfixation distance, the percentage overlap of the viewer fixations, and the pattern of viewer 

movements. A set-up program allows fault types to be assigned to different •ivets, and information such 

as feedforward and feedback to be added Obviously, not all features of the simulation were used in all 

experiments. 

In all of the experiments, engineering student subjects were used, as these represent well the 

technically-fluent, but inexperienced, labor pool from which the aviation mechanics (who will eventually 

become insp.!ctors) are drawn. 

The five intervention issues were tested in five experiments. All five measured performance by many 

measures, using statistical tests to determine whether each intervention had the predicted impact on each 

measure. It is not tile intention of this report to provide exhaustive experimental details, but rather to 

demonstrate the main results, interpret these results in terms of training of airframe inspectors, and outline 

any still-umesolved issues in terms of future evaluation needs. Full details are available elsewhere 

( Gramopadhye, 1992). and will eventually be publisbed as a sequence of individual technical papers. This 

sequence has already begun with the visual lobe training evaluation (Latorella, et al., 1992; Drury and 

Gramopadhye, 1992). 

8.6 VISUAL SEARCH TRAINING EVALUATIONS 

IIL a visual search task, the inspector's eyes move across the inspected area, fixating subareas with tile eye 

stationary and jumping rapidly between fixations. The area within which a target can be detected during 

a fixation is ilie visual lobe. lbe size of this visual lobe is important as it determines how thoroughly an 

area will be searched in a given time period, and hence directly determines the probability of defect 

detection. Search strategy is the sequence of fixations used by the inspector and determines the total 

coverage of the area. An effective and efficient strategy is one which covers the whole area with the 

minimum overlap between fixations and the minimal back-tracking. 1be first issue concerns the visual 

lobe size, while the second and third issues evaluate strategy. 

3.6.1 Can Tnlinlng Improve Defect Conspicuity? 

The objectives of this experiment were to determine the relationship between visual lobe and search 

performance, relate changes in lobe size to search performance, and to evaluate the effectiveness of lobe 

training. In particular, lhe experiment measured whether crossover effects exist in visual lobe training. 

It used two types of rivet faults (cracks and loose rivets) and two types of area faults (corrosion and dents) 

to determine whether visual lobe training on one fault would generalize to other faults of the same or 

different classes. 

The experiment consisted of a familia.-ization training followed by four visual search tasks, each consisting 

of 20 examples of one fault type. Following these tasks, each of the four groups of six subjects undertook 

different training schemes based on a visual lobe task which presented a fault for 0.3 seconds at one of 

six positions around a central fixation point. The four groups received the following training: 

140 
Rivet Group: 

Area Group: 

Neutral Group: 

Control Group: 

Training for Ywurllnspeciion of Aircraft Structures 

Five lrials of 120 m-ual lobe screens containing loose rivets. 

As Group 1 except using dents. 

As Group 1 except using a fault (cross) which was irrelevant to the search task. 

An equivalent time on a word processing task on the same computer. 

Following training, the four visual search tasks were repeated for all groups. 

To detennine wllether the visual lobe increased in size during the training, an ANalysis Of V Arial!ce 

(ANOV A) was conducted for the lobe size for the three groups (1, 2 and 3) receiving lobe training. Over 

the five training lrials significant effects of group (F (2,15) = 11.05, p < 0.0011) and training trial (F 

(4,60) = 13.46, p < 0.001) v.ere found. To test wbetller the visual lobe training transferred to the visual 

search task, ANOV As were performed on the mean search times for e;ch fault type. For all four fault 

types, the patterns of the ANOVA results were similar. There were no group main effects (p > 0.15 in 

all cases), significant IIial effects (p > 0.05 in all cases) and significant group x trial interactions (p < 0.05 

for all cases except Rivet Crack where p < 0.10). Table 8.1 shows the percentage improvements 

following training (ie., the group x IIial interactions) for e;ch fault type. It can be seen that the two faults 

trained in the visual lobe training had the largest improvement. For the faults 1!Q! tr~lled by visual lobe 

training, the improvement was greater where there was more similarity to the viSW'1 iote fault. Neutral 

training had a smaller amount of transfer, while no training, ie., spending equivalellt lime on another 

computer task, had no beneficial effect. 

Table 8.1 Percentage Improvement in Mean Search Times After Training for the Four Training Groups 

Rivet faults Area Faults 

Group loose Rivet Rivet Crack Dent Co!TOsion 

1. Loose Rivet Training 50.6 41.4 15.0 15.8 

2. Dent Training 13.8 13.0 41.6 482 

3. Neutral Training 5.8 18.5 16.3 262 

4. No Training 3.9 5.0 -4.9 -12.7 

Providing training, even just repeated practice, in rapidly detecting a fault in peripheral vision, did indeed 

increase the size of the area in which that fault could be detected in a single glimpse, i.e., the visual lobe. 

This increased visual lobe was not merely a result of increased familiarity with the experimental visual 

lobe task, as it transfers to a more realistic inspection task, visual search. For each fault type there was 

a 20-30% increase in lobe size over just five practice lrials. There was a close correspondence between 

the training on actual faults (Groups 1 and 2) and improvement in search times, and even some 

improvement for training on a neutral fault, i.e., one which did not appear in any search tasks. No 

training, as expected, produced no effect. 

141 
. . -. -.. , : . ,~ 

-

Chapter Eight 

8.6.2 How Eff'ective is Feedback in Changing Search Strategy? 

The objectives of tbis experiment were to evaluate the effc:ctiveness of providing different types of 

feedback on the inspection search strategy. Performance feedback is lraditional, i.e., bow many defects 

were detectOO, or bow long it took to detect an of the defects, but it is possible to giv~ feedback on the 

process, or strategy, by which the inspe<."tor achieved these results. lbis may or may not help the 

inspector: evaluation is needed. Within this "cognitive" feedback, there are different ways in whic.'l the 

information can be presented to the inspector. Here we compared p-ocess measure feedback (e.g., how 

much of the area was covered; what percentage of fixations overlapped) to visual feedbliCk of the scan 

path used by the inspectOr. The former gives hard numbers, the latter a visual pattern. The literature is 

silent on which is the better form of cognitive feedback, or wbethec either is better than traditional 

performance feedback. 1bus, fiuthec evaluation is required. 

All 24 subjects received f2Jlliliarization toaining followed by a visual search task (Trial 1) which consisted 

of 15 search areas, each with either zero, one or two of the four faults (rivet crack, loose rivet, dent, 

corrosion). FoUowing this visual search task the s-.Jbjects were assigned to one of four groups: 

Control Group 'Three trials of 25 search areas with IlL feedback 

Process Group Three trials of 25 search areas with f~ack or process measures after each trial 

Visual Group Three trials of 25 search areas with on-line visual feedback of search patterns 

during each trial. 

Performance Group Three trials of 25 search areas with feedback on speed and accuracy after each 

trial. 

After these training interventions, subjects were given a second visual search task (Trial 2) of 15 search 

areas with no feedback. Colllp"'..rison of Trial 1 with Trial 2 allowed an evaluation of the relalive 

improvement with either practice only (conttO: group) or the various rypes of feedback. 

Both process measures and performance measures were analyzed for the four groups on the two tlials. 

For all of the process mea;,~~res, there was a group x trial ioteraction, sl!owing that certain groups improved 

more than others. Table 8.2 sllows !he percentage changes for each group from Trial 1 to Trial 2. 

None c" the changes for the comrol group were significant, showing that more practice did not change 

search strategy. The process group showed less fixations more widely spaced, and with less overlap, but 

the area covered decreased. The visual group showed a similar, if smaUer, effect but one which did not 

result in a decreased coverage. Finally, the performance group showed no change in interfixation distance 

or area covered, but did give a reduced number of fixations more widely spaced. Oearly, cognitive 

feedback had the major effect on search strategy. 

142 
Training for Visual Inspection of Aircraft :,iTUCtllres 

Table 8.2 Percentage Changes in Process Measures after Training for Feedback Experiment 

CONTROL PROCESS VISUAL PERFORMANCE 

GROUP GROUP GROUP GROUP 

Number of FIXations +6.6 -54.1 -30.9 -27.8 

lnterfixation Distance -5.2 +15.3 -6.8 0 

Percentage OVerlap +5.7 -55.1 -50.5 -18.0 

Percent of Area Control +2.1 - 7.0 + 1.9 -0.9 

PerfOflllliDCe measures, in contra~ showed trial effects for search times and stopping times but not for 

percentage defects detected. Table 8.3 shows the percentage changes in each measure for each grol».). 

Table 8.3 Percentage Performance Changes by Group for Feedback Experiment 

CONTROL PROCESS VISUAL PERFORMANCE 

GROUP GROUP GROUP GROUP 

Search Tune 0 -26.0 -15.2 -37.1 

Stopping Tune -4.9 -50.4 -35.4 -51.1 

Percent Detected -1.2 -8.1 + 1.6 - 1.0 

As with process measures, the control group showed no effect of their practice. The process group was 

considerably faster at search, but appeared to reduce their stopping time too much, giving a decrease in 

defects detected. The visual group had smaller reductions in search and stopping times, and no change 

in percent defects detected. The performance group was able to speed up the most, and reduce their 

stopping times the most without sacrificing accuracy. Oearly, performance feedback enhances 

performance. 

When feedback, or knowledge of results, was provided, behavior and performance changed in predictable 

ways. Subja:ts responded to the feedback given by improving most those aspects of the task included in 

the feedback. Thns, cognitive feedback helped subjects optimize their search strategy, while performance 

feedback gave the largest performance gains. All feedback groups changed their strategy in a similar 

manner, by having less fixations with less overlap. However, the dangers of feedback were illnsttated 

when the process group made dramatic changes in strategy, resulting in slightly reduced coverage. This 

meant that their speed increase was not achieved with constant detection performance like the other 

groups, but with poorer detection performance. (A current extension of this ell:peliment is evaluating the 

combination of feedback types to determine whether provision of both cognitive and performance teroback 

will yield larger improvements). Fmally, it should be noted that more practice without knowledge of 

results (the control group) gave no improvements in strategy or performance. Only practice with feedback 

makes J.'effect. 

143 
Chapter Eight 

8.6.3 How Effective is Feedf'orward in Changing Search Strategy? 

Guidance or feedforward (Section 8.3.3) is a powerful tool in helping the trainee concentrate on the 

appropriate visual cues in the task. In airframe inspection, it comes from two sources: (1) general 

knowledge of the physics of aircraft structures and the enviromnental conditions which act to cause faults, 

and (2) specific guidance (e.g., on workcards, from co-workers) on which faults to expect in which parts 

of the structure. However, there is a danger with alerting an inspector to one type of defect and/or one 

area: other defects and areas may be de-empbasized giving poorer performance. The objective of this 

experiment was to evaluate general specific and combined feedforward in an aircraft inspection task. To 

measure whether improved pedormance on the cued defect was being obtained at the expense of other 

faults, two scenarios were devised. one emphasizing corrosion defects and the other emphasizing rivet 

defects. 

Twenty-four subjects were given the familiarization training and then performed one visual search task 

under each sceilario (Trial 1). Each task consisted of searching 55 search areas for the same four defects. 

The subjects were divided into the following four groups: 

Control Group No feedforward information 

Prescriptive Guidance Specific, prescriptive information on both scenarios, i.e., which type of defect was 

most common 

Descriptive Guidance General, descriptive information on both scenarios, i.e., the recent history of the 

aircraft's use 

Combined Guidance Both types of guidance 

Scenario 1 emphasized corrosion defects, either by naming specific areas where corrosion was expected 

(lower part of fuselage) or by general history (aircraft employed carrying chemicals, and based at coastal 

airport). Scenario 2 emphasized rivet defects, but without any more detailed information on the location 

of the rivet defects. After dlis information, subjects inspected 55 more areas under each scenario (Trial 

2). 

The results sh!>wed no significmt group or trial differences, or interaction, for the process measures for 

Scenario 1 and only a trial effect for percentage area covered for Scenario 2. As this latter change was 

less than 2%, there were essemially no effects of feedforward on search strategy. 

For performance measures, there were group, trial and interaction effects on search time for Scenario I, 

and group and trial effects for search and stopping times in Scenario 2. Table 8.4 shows the percentage 

changes between Trial 1 and Trial 2. 

144 
Trtzining for Visual Inspection of Aircraft Structures 

Table 8.4 Percentage Performance Changes by Grcup for Feedforward Experiment 

Control Prescriptive Descriptive Combined 

Group Group Group Groups 

Scenario 1 

SsarchTime +14.8 ·23.4 -23.7 -30.8 

Stopping Time + 7.3 ·10.6 ·6.5 ·31.1 

Percent Detected • 4.7 • 9.3 + 1.6 + 2.1 

Scenar!o2 

Search Time ·13.5 ·11.3 ·13.4 + 0.7 

Stopping Time ·28.8 ·15.2 -17.1 -14.4 

Percent Detected 0 + 1.6 + 2.8 + 9.8 

For Scenario 1, performance improved in terms of speed for all groups except the control group, wbile 

accuracy remained constant except for a decrease by the prescriptive group. This decrease was almost 

entirely due to reduced detection of the rivet defect, i.e., the one which was not cued. Scenario 2 gave 

peJ:nliar results. Not only did the control group show the largest speed gains, but the combined group was 

the only condition to post improvements in accuracy. Even this awJrllCY gain was for the non-cued area 

faults! 

It appears 1llat feedforward information is difficult for subjects to use effectively. Strategy cbanges were 

almost all nonsignificant, while performance changes, even though significant, were mixed. Speed may 

impmve, but accuracy may get worse (Scenario 1) or better (Scenario 2) for defects which are specifically 

called out Much more needs to be known about the effects of feedforward on aircraft inspection before 

it em be recommended with any confidence. Even the calling out of specific defects on workcards, long 

thought to be a pre-requisite to effective inspection (e.g .• Drury, et al., !990) may need to be evaluated 

more closely. 

8.7 DECISION MAKING ISSUES 

When a defect has been located (visual search) a decision must be made as to its severity to determine 

the correct response (ignore, record for later repair, record for illllllediate tepair). This decision is 

sometimes as simple as judging the ftee play in a control linkage, but more often it is a complex 

judgement. For example, a dent must be judged for size, deplh and position, or corrosion for location, 

extent and severity. Inspectors gradually develop a mental picture (schema) corresponding not to any 

particular defect previously seen, but rather to a prototype of a defect at 211 action level. 1be two 

experiments reported here used a progressive part-training scheme to class'.fy rivets (Section 8.7.1) or 

corrosion (Section 8.7.2). In each case there was a comparison between active and passive training. In 

each case a determination was made also as to whether the learning transfer from a decision task to a more 

complete illspection task involving both search and decision. The experiments differed in 1llat the first 

concerned the accurate perception of each separate attribute of a defect, while the second examiDPit 

integration of attributes into an overall schema of the defect 

145 
Cluzpter EighJ 

8.7.1 Perception of Multiple Defect Attributes: Active or Passive Training? 

The experimental objective was to compare well-designed active and passive training schemes for the task 

of correctly classifYing individual attributes of a defect. The task was to judge rivets on a panel, where 

each rivet could have two levels of severity on each of three attributes: edge smoothness, out-of-round, 

and flatness. Eight combinations (combinations of two levels of each of three attributes) plus the six 

single-attribute defects gave a total of fourteen different defects. 

Twelve subjects were assigned to one of two groups for training: 

Passive Group 

Active Group 

Subjects saw each defect five times in the center of the screen. followed by 

progressively more combinations of defect attributes, witb the couect 

classification sbown beside each defect. 

As for passive group, except tbat subjects had to enter the classification of eacb 

defect (witb immediate feedback) rather than merely reading the classification. 

After trainlng, each subject was presented witb fifteen examples of each defect (210 total defects). The 

defective rivet appeared in the center of the screen. witb a classification response required of the subject. 

Following tbis decision task. an inspection task was given, again witb 210 defects. Jn the inspection task, 

tbe subject first had to locate the defective rivet among the other rivets in a search area, and then give the 

classification response. 

Significant differences between active and passive training for the percentage correct decisions were found 

for both the decision and inspection tasks, as sbown in Table 85. 

Table 85 Percent Correct Decisions for Attribute Perceptions 

PASSIVE TRAINING ACTIVE TRAINING 

Decision Task 79.0 83.8 

Inspection Task 71.0 85.5 

The active training scheme produced a clear advantage in accuracy in botb tasks. 1ndeed, it gave a greater 

advantage when the decision was embedded in a more complex inspection task involving search and 

decision. Analysis of the search times in the inspection task showed no difference between the two 

training schemes, indicating tbat decision training does not improve search performance, only decision 

performance once search for the defective rivet has been completed. 

Clearly, an active training scheme is preferred. even when compared to an equally well-designed 

progressive-part passive scheme. 1be inspector's active involvement in learning is essential. 

8.7.2 Integration of Multiple Defect Attributes: Active or Passive Training? 

In addition to merely classifYing each attribute of a defect correctly, inspectors often need to combine 

information from more than one attribute when making a judgement. The objective of tbis experiment 

146 

. ···.···1 

·-.'·· 

' " 
Training for V"rsutlllnspection of Aircmft Struetuns 

was to stndy the development of such schema. or combinations of attributes, under active and passive 

training schemes. 

The task used areas of corrosion. each of which had three attributes: density, quantity and color. Density 

and color could be at three levels on the computer display, while quantity could be at two levels, giving 

eighteen combinations in all. Subjects had to reach an overall judgement of severity as low, moc:lt%ate or 

high depending upon the particular combinations of levels of the attributes. 

As in the previous experiment, two groups of six subjects each wece used: 

Passive Group Subjeds saw each of the 18 defects five times in the center of the saee'l, 

followed by combinatious of defect attributes. The correct classification (L, M 

or H) was shown beside each defect. 

Active Group As for passive group except that subjects has to entl% L. M or H for each 

defect, with immediate feedback. 

The decision task consisted of 120 defects, each shown in the center of the screen. with the subject 

responding L, M or H after each defect. For the inspection task, each of the 120 defects was embedded 

in a screen consisting of the same rows and columns of rivets used in the previous experimeot. Again, 

the subject had to first locate the defect and then classify it as L, M or H severity. 

There were significant group differences on both decision and inspection tasks for percentage correct 

responses, and for information transmitted in bitslresponse. As in the previous expeciment. there was no 

significant group effect on search times in the inspection task. Table 8.6 shows the mean values. 

Table 8.6 Performance by Group, Integration Experiment 

PASSJVE TRAINING ACTNE TRAINING 

Percent Correct, Decision 77.4 87.8 

Percent Correct, Inspection 73.5 86.3 

Information Transmitted, Decision 0.76 1.06 

information Transmitted, Inspection 0.74 0.99 

Active training was again significantly better on all measures, but here there was no extra improvement 

on the more complex task. In both decision and iDSpection. errors were roughly halved wben the actively 

trained group was compared to the passively trained group. Clearly, active participation of the inspector 

is a key element in learning to integrate information from many attributes. 

147 
Chllpter Eight 

8.8 TRAINING METHOD FOR AJRCRAFI' STRUCTURAL INSPECTION 

In this section we outline a general training method that uses the key conclusions of the research and 

indicates how it can be applied to enhance training on a particular inspection task. The conclusions can 

be summed up as: 

1. Visual lobe training improves mean search times and is generalizable across all faults within a 

fault seL 

2. Feedback of process and performaDce measures can improve search strategy and reduce search 

time. 

3. Feedforward information helps modify search strategy. 

4. Active and progressive part-training help improve classification performance. 

Figure 8.2 describes a genecal methodology for developing training programs for aircraft inspection. This 

section elaborates on the "training method" part of the methodology, giving as an example, the inspection 

task during a B-cbeck on a DC-9. 

This training methodology uses: 

1.. A mix of classroom and structured OJT 

2. Visual lobe training for specific faults 

3. Feedback of JroCeSS and performance measures 

4. Feedforward information 

5. Active training for defect classification. 

The methodology is explained using a section of a B-check for nose landing gear and wheel well 

inspection. There are three major components to this inspection: 

1. Wheel wen, doors, adjacent components 

2. Nose gear assembly and installation 

3. Nose gear tire and wheel assembly. 

Table 8.7 presents a condensed overview of this entire B-cbeck. The entire inspection has been broken 

down into two parts: structure and defects. The structure explains the compollent to be inspected, and 

the defect column lisrs the non-conformities to look for. This allows us to identify (a) the aircraft 

knowledge that the inspector should have, and (b) the defects that are being looked for. 

8.9 CLASSROOM TRAINING 

This should consist of the followi11g components: 

1. Information on Area. The trainees should learn the names and locations of all relevant parts of 

the area (listed under the structure coluum in Table 8.7) to be inspected. Active training methods 

used should make the trainee name and locate all the relevant parts/areas. This training should 

148 
Training for YISuallnspeCIWn of Aircraft Strudures 

also include functiolllil knowledge about the various components, combined with adequate 

feedback on performance. 

2. Information on Workcard Usage. This part should familiarize the trainees with the workclo..rd 

Steps include showing them how to use the workcard, knowledge of various procedures, e.g., 

checking depth of nicks or digs, releasing of nose steering bypass, etc. Information should be 

imparted on how to write non-routine repair cards. Again, an active training method is 

appropriate. 

3. Exaronles of Defects in Each Area A defect list must he generated from the workcard, giving 

a listing of an the defects that an inspector using the workcard must look for (Table 8. 7). An 

effort should he made to collet samples, photographs, video tapes of an defects. An active 

training method wbele the trainee Jdentifies, aDd classiiies, each defect should be followed 

Cognitive feedback should he provided dming the training. 

4. Visual Lobe Training. Visuallohe training can he provided on a simulator, similar to the one 

used in the evaluatious (Section 8.6) for some of the visual defects like corrosion. vLoual damage, 

fluld leaks aDd worn parts. Now that actual photographs can he scanned readily into computer 

systems, defects can be placed easily in many places on the scanned visw.; image of the area to 

he inspected. lbus, creating a realistic simulator for visual lobe training is possible. 

8.10 STRUCTURED ON· THE-JOB TRAINING 

A structured on-the-job training methodology imparts a controlled training atmosphere In a work setting. 

Since it is expensive to produce a realistic simulator of the whole inspection task, we are constrained to 

have some training done on the job. The OJT method should involve the show-tel!-do routine that 

includes demol'lstration by the expert inspector on 'Ill efficient way to inspect followed by the trainee 

inspecting the am:raft with subsequent feedback from the experienced inspector. This needs to have both 

performance and cognitive aspects, i.e., whether the search was successful, and whether it was performed 

using the most effective strategy. The experienced inspector should also provide feedforward on each area 

to the trainee in terms of what defects to look for, defect criticality, past history, etc. 

In the space available in this report, more depth cannot be included concerning the detailed application 

of the research findings to aircraft inspection. However, the level chosen for presentation here does 

demoDStrate the principles involved and how they can be applied with minimal hardware requirements. 

149 
Chapter Eight 

•• •• 

r-' .. 'S 

if~c .n 

r- ._! 

• • 

11 11) i 

~ Jri i ~~-~J Ji !'~p -~· .,.1 I! i~J - ~~~::all 

·~~- ~ I i I I 1 1 • • 

• • • • • • 

.. --- --, 1 

---

I .. 

I ;-I J 

l 1 t 

I 

I 

.. • 

-II 

.! 

1.. . • I : •• .!:' 

•II 

li:i 

• • • 

Figure 8.2 Model for Training Program Development in Commerdal Aviation 

150 
... 

"' .... 

Table 8. 7 Nose L!llldlng Gw and Wheel Weii lru.-pection (B·Oie<'.k) 

WHIEL WELL, DOORS, NOSE OleAR ASS EMIL"! I. 

ADJACENT COMPONENTS INSTALLATION 

ltruc:&ura Defee~ Structure D•f.cts 

1.Yolloolwol • Condition 1. NLG ohoel< oiout, b-. t-

"1"1-tU>Ing • Cam>lion arm, gi'OI.M'1d 111nllilg mecheniam, 

·-Ill Ykull damage 

- • Fluid leokage cobloo, actuotllg cylnder, llnkageo, • nlckl&dhgs .. 

opmgo •ftuldleoka 

...... .., 

a.-..wol •condition 2. Londing II"'- otrut • cAwck tor nonnst •*filion -.~n~~ogo. • vioull domogo 

oprlngo, ..... •corrolion ··- • ·-................ ol plolon •biN,- . .....,.., .... rod hr<frallc .. & wlpo dry 

ovdo and hinge• 

3.- •genorol S.NoH-rl!gmoehorlom ·JMr~mg<o condition 

·-

•loolcago .......... ·--

• - ol--.lng ... 

• poollon - ffllll'v ...-.. ~ 

4. N.G <ilgr!inonl ·- 4. Torquo llnkl 

~ 

• - lrUII*Igo&-

• - buol1lngo • -

1. NLa IUIIIQhl ·•anini• 6, i.Mir*lg goor 1ac1c piw & rod ...,jng 

• tlllmlrll 

-.. ·-f HQUrll e' '11111\1 of~ 

.. -

lolaclcpN . .....,..,of •langYlof ---bo -mblf 244ll'long. 

e.t&.G doora ·--

IN ololed 

·--

ftiW &DCUIW 

._...,roet<en 

7 ................ • condition 

-kinO placord 'IICUr1tj 

'l>catlon glvon 

e. NoH IN • condition ,.._ pkcord • ucurtty 

'ioclltlon given 

e. Uplook llfJd • oondltlon·c:!oan 

.,.,.may dooftlook _ .. Wne~,;"ry •ucu 

NOSE GEAR TIRES a 

WHI!EL AIIIMILY 

&tructurw Def.cta 

t. Wheel hubo 

voU...tltbolt ·-.......... 

2. n ... •e*"'tt!vewur 

• oiiOiildng ·--·onlf -2 ... ol pOrl*lg ·-wllht.il.anlf 

3.WIIIr- ....... ........., • ......, of lnolrllatlon 

.. 4:/JIX/51 ..... O.CIOti.CU1311lorv4-

&pUrl 

- notflin8 ong. 

J 

...... 

.. 

;s; I 

i 

i-

;a 

oi\ 

~ i 

i ll 
·- ·.· ~. 

Chapter Eight 

8.11 CONCLUSIONS 

This research program has used observations of the current training of visual inspection, and the principles 

of effective training to deli ve experimental evaluations of specific interventions. The experiments had 

(generally) highly successful outcomes, showing that many of the interve&tions can indeed be applied to 

visual inspection training. An example is provided which outlines how these findings can be applied to 

an existing task. The next challenge is to devise and implement detailed inspection training programs 

based on these findings and evaluate these new programs on the hangar floor. As a side-benefit of the 

research, a simulation program is now availaiJle to allow rapid evaluation of other training interventions 

without disruption of on-going inspection activities. 

8.12 REFERENCES 

Bartram, D. (1988). The design and evaluation of a computer-based training system for foreign 

destination coding desk operators. In Pallick, 1. and Duncan, E. D. (Eds), Training, J..unum decision 

making cmd controL Amsterdam: Elsevier. 

Brown, J. S., Burton, R. R. and DeKleer, J. (1982). Pedagogical, natural language and knowledge 

engineering techniques in SOPHIE I, II and ID. In Sleeman, D. H. and Brown, J. S. (Eds.), 

Christal, R. E. (1974). The United States Air Force occupalional research project. (Tech. Rep. No. 

AFHRL-Tr-73-75). Texas: Air Force Human Resources Laboratory, Occupation Research Division. 

Clancey, W. J. and Soloway, E. (Eds.). (1990). Artificial inteUigence cmd learning environments. 

Cambridge, MA: Bradford/MIT Press. 

Czaja, S. I. and Drury, C. G. (1981). Training programs for inspection, Human Factors, 23, 4, 473-484. 

Desormiere, D. (1990). Impact of new general aircraft on the maintenance environment and work 

procedures. Proceedings of the Fifth FAA Meeting on Human Factors in Aircraft Maintenance and 

Inspection, 124-134. 

Doherty, M F.. and Balzer, W. K. (1988). Cognitive feedback. In Brehmer, B. and Joyce, C. R. B. (Eds.), 

Hwnanjudgement: The SJT view. New York: North Holland, 163-195. 

Drury, C. G. (1990). Visual search in industrial inspection. In Brogan, D. (Ed.), Visual Search. London: 

Taylor & Francis, 263-276. 

Drury, C. G. and Gramopadhye, A. K. (1992). Training for visual inspection: Controlled studies and field 

implications. Proceedings of tt.e Seventh FAA Meeting on Human Factors Issues in Aircraft 

Maintenance and Inspection, 135-146. 

Drury, C. G. and Gramopadhye, A. K. (1990). Training for visual inspection. Final Report of the Third 

FAA Meeting on Human Factors Issues in Aircraft MainteiUJIIce cmd Inspection, 149-164. 

152 

. 

. '1 
Drury, C. G. and Kleiner, B. M. (1990). Training in indus1rial environments. Proceedings of the 23rd 

Annual Conference of the Human Facwrs Associlltion of ClJ111lda, 99-108. 

Drury, C. G., Prabhu, P. V. and Gramopadhye, A K. (1990). Task analysis of aircraft inspection 

activities: methods and findings. Proceedings of the Human Facwrs Society 34th Annual Meetfilg, 

1181-1185. 

Flanagan, J. C. (1954). The critical incident technique. Psychological Bulletin, 51, 327-358; 

Goldsby, R. P. (1991). Effects of automation in maintenance. Proceedings of the Fifth FAA Meeting on 

Human Facwrs Issues in Aircraft Maintenance and Inspection, 103-123. 

Gramopadhye, A. K. (1992). Training for VISUal Inspection. Unpublished doctordi dissertation, State 

University of New York at Buffalo. · 

Hammond, K. R. and Summers, D. (1972). Cognitive Control. Psychological Review, 79, 1, 58-61. 

Johnson, W. B. (1990). Advanced technology training for aviation maintenance. Final Report of the Third 

FAA Meeting on Human FacUJrs Issues in Aircraft Maintenance and Inspection, 115-134; 

Johnson, W. B., Norton, J. E. and Utsman, L. G. (1992). New technology for the scboolhouse and 

flightline maintenance environments. Proceedings of the Sevi?A.th FAA Meeting on Human Factor Issues 

in Aircraft MaintenCUice CUid Inspection, 93-100. 

Kello, J. {1990). The role of simulation in technical and team-skills training. Proceedings of the FAA 

Training Technology Symposium, 133-148. 

Kurland, L. and Huggins, A. W. F. (1990). T;"aining trouble-shooting using advanced AI-based training 

technology. Proceedings of the FAA Training Technology Symposium, 133-!48. 

Latorella, K. A., Gramopadhye, A. K., Prabhu, P. V., Drury, C. G., Smith, M.A. and Shanahan, D. E. 

(1992). Computer-simulated aircraft inspection tasks for off-line experimentation. Proceedings of the 

Human Facwrs Society 36th Annual Meeting, 92-96. 

Lesgold, A. M. (1990). Intelligent computer aids for practice of complex troubleshooting. Proceedings 

of the FAA Training Technology Symposium, 116-132. 

Lesgold, A M., Lajoie, S. P., Bunzo, M. and Eggan, G. (1992). SHERLOCK: A coached practice 

environment for an electronics troubleshooting job, In Larkin, J., Chababy, R. and Scheffic, C. (Eds), 

Computer assisted instruction CUid intelligent tutoring systems: Establishing communication and 

collaboration. Hillsdale, NJ: Lawrence Erlbaum. 

Lukins, J. (1990). Automation and maintenance trailling. FAA Training Technology Symposium, 66-12. 

153 
Lutzinger, R. T. (1989). Day-to-day problems in air canier maintenance and inspection operations. Final 

Report on FAA Meeting on HIIIMII Factors Issues in Aircraft Maintellmlce and Inspection, A-17- A25. 

Naylor, J. C. and Briggs, G. E. (1963). Effects of task complexity and task organization on tlJe relative 

efficiency of part and whole training methods. Journal of &perimerltal. Psychology, 65, 217-224. 

Norton, J. E. (1992). Intelligent simulator for maiDtenanre trail!ing. Proceedings of the Seventh FAA 

Meeting on Human Factor Issues in Mrcraft Maintenance and Inspectiml, 101-Hl6. 

Orlansky, J. and String, J. (1979}. Cost-effectiveness of computer-based in.stmction in military training 

(IDA Paper P-1375). Arlington, VA: Institute for Defense Analyses and Technology Division. 

Pattick J. (1992). Training Research ond Practice, New York: Academic Press. 

Payne, H. E. (1990). Army training 21: Concepts of the future. Proceedings of the FAA Training 

Technology Symposium, 174-179. 

Reigeluth, C. M. and Stein, F. S. (1983). The elaboration theory of inslruction. In Reigeluth, C. M. (Ed), 

Instructionai design theories and models. An overview of their current stat-JS. Hillsdale, NJ: Lawrence 

Erlbaum. 

Rice, J. W. (1990). Use of 3-D presentations in mainlenance training. Final Report of the Third FAA 

Meeting on HIIIMII Factors Issues in Aircraft Ma.intenonce and Inspection, 135-139. 

Skinner, M. (1990). Aviation maintenance praclicea at British Airways. Proceedings of the Fourth FAA 

Meeting on Human Factors Issues in Aircraft Maintenance and Inspection, 143-153. 

Shepherd, W. and Parker, J. (1990). Human factors issues in aircraft maintenance and inspection "Training 

issues." Final Report of the Third FAA Meeting on Human Factors Issues in Aircraft Maimenance and 

Inspection. 

Walter, D. (1990). An innovative approach to NDT inspectOr training at Boeing. Final Report of the 

Third FAA Meeting on Human Factor Issues in Aircraft Maintenance and lnspectiml, 52-71. 

Wirstaad, J. (1988). On knowledge struaures for process operators. In Goodstein, L. P .• Andersen, H. 

P. and Olsen, S. E. (Eds.), Tasks, errors ond menttil models. New York: Taylor & Francis, 50-69. 

154 
I -