DOT/FAA/AM-02/23

Scott M. Goldman

Edna R. Fiedler

Raymond E. King

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

December 2002

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, VA 22161.

General Aviation MaintenanceRelated Accidents: A Review of

Ten Years of NTSB Data Office of Aerospace Medicine

Washington, DC 20591
NOTICE

This document is disseminated under the sponsorship of

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

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page

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

DOT/FAA/AM-02/23

4. Title and Subtitle 5. Report Date

General Aviation Maintenance-Related Accidents: A Review of Ten Years of December 2002

NTSB Data

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

Goldman SM, Fiedler ER, and King RE

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

FAA Civil Aerospace Medical Institute

P.O. Box 25082

Oklahoma City, OK 73125 11. Contract or Grant No.

12. Sponsoring Agency name and Address 13. Type of Report and Period

Covered

Office of Aerospace Medicine

Federal Aviation Administration

800 Independence Ave., S.W.

Washington, DC 20591 14. Sponsoring Agency Code

15. Supplemental Notes

Work was accomplished under approved subtask AM-E-01-AAM-182.

16. Abstract

NTSB accident investigation reports for general aviation accidents occurring between 1988 and 1997 were

analyzed in order to provide a descriptive look at ten years worth of accident data. This sample included

1,503 reports, all of which indicated at least one maintenance-related issue as a cause or factor in the

accident. Initial analyses describe the frequency of occurrence for type of maintenance task and type of

aircraft. Accidents were compared on frequency of occurrence, number of fatalities, and number of serious

injuries. Odds for each variable resulting in a fatality or injury are reported. Results indicated that

installation errors were the leading maintenance-related cause or factor involved with the accidents. Since

installation errors were most common further analyses focused on a more detailed description of

installation error. Type of installation error, type of aircraft system involved in the installation, whether or

not the installation was inspected, credentials of the mechanic performing the installation, and the

operational impact of the installation error were investigated. Results indicate that reversed installation and

wrong part were the two installation errors most likely to cause death or injury in GA aircraft accident.

17. Key Words 18. Distribution Statement

General Aviation Maintenance, Human Error, Installation,

Inspection

Document is available to the public through

the National Technical Information Service;

Springfield, VA 22161

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22.

Price

Unclassified Unclassified 12

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

1

GENERAL AVIATION MAINTENANCE-RELATED ACCIDENTS:

A REVIEW OF TEN YEARS OF NTSB DATA

During the last several decades, improvements in

aviation safety have made commercial flying in the

United States the safest form of transportation. General Aviation (GA), however, has not enjoyed the same

safety record. From 1988 to 1997, the average rate of

accidents per 100,000 flight hours was 8.172 for GA

and .2267 for scheduled commercial airlines operating under 14 CFR 121 (NTSB, 2000a). Although GA

aircraft log almost twice as many flight hours as do the

airlines (for 2000: 30,800,000 and 17,170,000, respectively [NTSB, 2000b,c]), the accident rate per

100,000 flight hours for GA aircraft in 2000 is over

twenty times greater than the rate for commercial

aircraft (5.96 and .285, respectively, NTSB, 2000b,c).

To further delineate the differences in safety between

GA and commercial airlines, from 1988-1997 commercial airline accidents resulted in 1,493 fatalities

(NTSB, 2001b) while GA accidents accounted for

7,446 fatalities (NTSB, 2001c).

Historically, GA human factors research has placed

greater emphasis on the behavior of the pilot, his/her

judgment and decision making, and interactions with

air traffic control while paying limited attention to

the maintenance environment. Often, GA maintenance accident investigations end with the conclusion

that the cause of an accident was maintenance-related- without further investigating the details of who

performed the maintenance, why the maintenance

was necessary, and any possible human factors issues

underlying the maintenance error. Consequently, no

comprehensive database of GA maintenance-related

human factors incident data exists, and little information has been published in the scientific literature

regarding human factors issues in GA maintenance

operations.

While the literature regarding GA aviation maintenance human factors is rather anemic, recent studies

have helped to identify the severity of human error in

aviation maintenance. Maintenance-related errors have

been associated with up to 15% of major aircraft

accidents (Murray, 1998) and 16% of Naval Aviation

Class A Flight Mishaps (Schmidt, Schmorrow, &

Hardee, 1998). Despite this seemingly small percentage, Allan and Marx (1993) found that maintenance

errors are the second leading cause of fatal accidents in

aviation, exceeded only by pilot error. These statistics,

coupled with the relative age of the fleet of GA

aircraft, as well as predictions of increased air traffic,

suggest a strong need for a more complete understanding of the human factors issues in GA maintenance.

Due to recent interest in maintenance human factors

in Part 121 and 135 operations, several important issues

relevant to human performance in the maintenance

environment have been discussed. For example, Reason

(1998) suggests that outdated maintenance schedules

should be modified to prevent unnecessary human contact with the aircraft system. Due to technological advances, aircraft components have become more reliable

and, as such, require less-frequent “disassemble and

inspect” methods of maintenance that can often do more

harm than good. In this case, the human introduces risk

in the form of human error, which may not be justified

for what might be only a marginal increase in safety.

The current study provides an overview of a ten-year

sample of GA maintenance-related accident data obtained from the National Transportation Safety Board

(NTSB) GA accident investigation reports. Initially, we

present a comparison of GA fatal-accident rates with GA

maintenance-related fatal accident rates. The frequency

and severity (measured in fatalities and injuries) of

maintenance activities determined to be a cause or factor

in these accidents are also presented. Initial analyses

indicated that maintenance installation was cited in

enough investigation reports (20%) to warrant a closer

examination. Therefore, the second phase of this study

focused only on accidents involving maintenance installation in this sample. Frequency of the type of aircraft

system involved in installation, the type of installation

error, who performed the installation, and the operational result of the error were calculated. The odds of a

fatality or injury for each type of installation error and

aircraft system are presented as a measure of the risk.

METHOD

GA Accident Data

Final reports for all maintenance-related accident

investigations involving GA aircraft between 1988 and

1997 were obtained from the NTSB. The NTSB defined

GA aircraft as “all civil flying except revenue air carrier

(including all Part 121 and all Part 135 operations”; S.

Smith, personal communication, May 16, 2000). The

current sample of accident reports was obtained by

querying the NTSB database for accidents that included
2

either a maintenance subject code or a maintenance

personnel code. The NSTB defines an accident as “an

occurrence associated with the operation of an aircraft

that takes place between the time any person boards the

aircraft with the intention of flight and all such persons

have disembarked, and in which any person suffers death

or serious injury, or in which the aircraft receives substantial damage” (NTSB, 2001d). This study included

only NTSB accident reports; incidents were excluded.

Of the 20,884 NTSB General Aviation accident investigation reports available between 1988 and 1997, 1,474

(7.1%) reported at least one maintenance-related error as

a primary cause or factor in the accident.

Part 1: GA Accident Overview

Data Classification. NTSB accident reports categorize maintenance activities according to the following

taxonomy: maintenance, service of aircraft equipment,

inspection, compliance with Airworthiness Directive

(AD), annual inspection, adjustment, alignment, installation, lubrication, modification, replacement, major

repair, major alteration, service bulletin/letter, design

change, overhaul, major overhaul, and rebuild/

remanufacture. The NTSB identifies type of aircraft as

follows: airplane, helicopter, glider, balloon, blimp/

dirigible, ultralight, and gyroplane.

Analyses. The frequency of types of maintenance

activity, maintenance personnel, and type of aircraft are

the primary focus of the analysis. Categories are compared based on frequency as well as number of fatalities

and injuries.

Part 2: Installation Errors

Each of the 295 installation reports were reviewed and

coded by two researchers. A separate taxonomy was

developed for each variable of interest and discrepancies

in coding were mediated by discussion. The focus of this

study was to analyze the frequency of each error and

aircraft system occurring in this 10-year sample. Of

additional interest was the operational impact of the

accident and whether or not the AMT was properly

certified.

Installation Error Classification. The error classification utilized for this analysis was adapted from Graeber

and Marx’s (1993) installation error taxonomy. Categories of installation error included wrong part, reversed

installation, incorrect attachment, omission, and incorrect connection. Wrong part refers to the installation of

a part that does not comply with the manufacturers

specifications or any supplemental service bulletins. The

reversed installation category refers to the installation of

aircraft components that are cross-connected or reversed.

Incorrect attachment refers to improper installation of

parts that have the sole function of attaching two or more

components of the aircraft (e.g., nuts, bolts, washers,

brackets and harnesses). Omission refers to an installation

that did not include a required component. Incorrect

connection refers to installations of aircraft components

that serve a function beyond simply attaching two or

more parts of the aircraft. An example of an incorrect

connection would be a fuel line that is accidentally

crimped during installation. Although the fuel line does

attach the fuel tank to the fuel intake system, the fuel line

also has the additional function of transporting fuel

between the fuel tank and the fuel intake system.

Aircraft System Classification. The aircraft system

taxonomy adapted and modified the NTSB aircraft

system classifications (1998) used to code the system

implicated in the accident under investigation. The

aircraft system categories are: flight controls, powerplant, landing gear, flight/navigation instruments, electrical system, fuselage, rotor system, wing (vertical and

horizontal), fire warning system, AC/heat/pressurization/oxygen, and anti-ice/de-ice system.

Certified Mechanic. Each report was coded to indicate whether the personnel who performed the installation on the accident aircraft was a licensed Airframe and

Powerplant (A&P) mechanic. Only two categories were

utilized; certified mechanic and non-certified mechanic.

Operational Impact. To determine operational impact, a taxonomy developed by Veinott and Kanki

(1995) was utilized. This taxonomy categorizes accident

outcomes based on whether the aircraft was flown to the

intended destination, returned to the departing airport,

or made an emergency landing.

Analyses. Frequency of each installation error, aircraft system, and operational impact are reported. Contingency tables were constructed and the odds of each

category resulting in a fatality or injury were calculated

to compare risk. A chi-square analysis was performed to

determine if type of error, type of system, presence of a

certified mechanic, and operational impact were statistically independent of the presence of a fatality or injury.

Cramer’s V is reported with all significant chi-square

analyses to indicate the strength of association.

RESULTS

Part 1: GA Accident Overview

Table 1 presents the frequency of accidents for each

type of aircraft. Airplanes were involved in more maintenance-related accidents than any other type of aircraft

(n = 1,262; 85.7%). Helicopters were the next most

frequently occurring aircraft in this sample with 182

(12.4%) involved in maintenance-related accidents. Less

than 2% of the maintenance-related accidents involved
3

other types of GA aircraft. The number of maintenancerelated accidents and fatalities per year are provided in

Table 2. The year with the highest number of maintenance-related accidents (1989, n = 176) also accounted

for the most fatalities (n = 84). The next highest year was

1992, with 73 fatalities resulting from 151 maintenancerelated accidents.

Figure 1 depicts the ten-year trend of the percentage

of accidents that result in a fatality for all GA accidents

compared with maintenance-related accidents. The percentage of all maintenance-related accidents that involved a fatality was quite variable across the ten-year

time frame, with peaks observed in 1989 and 1994 when

27% and 22% (respectively) of all maintenance-related

accidents resulted in fatalities. The year with the lowest

percentage of maintenance-related accidents resulting in

a fatality was 1988 (13%). Fourteen percent of all

maintenance related accidents in 1997 were fatal. Fatalities occurred, on average, in 18% of the maintenancerelated accidents annually.

Table 1

Frequency of Type of Aircraft Involved in a

Maintenance-Related Accident, 1988-1997.

Type of Aircraft Frequency Percent

Airplane 1,262 85.7

Helicoptor 182 12.4

Glider 9 0.6

Balloon 7 0.5

Gyroplane 7 0.5

Blimp/dirigible 3 0.2

Ultralight 2 0.1

Total 1,472 100.0

Table 2

Number of Maintenance-Related

Fatalities and Accidents by Year.

Year Fatalities Accidents

1988 21 132

1989 84 176

1990 34 146

1991 54 160

1992 73 151

1993 39 123

1994 52 122

1995 48 134

1996 51 159

1997 48 171

Total 504 1474

10%

15%

20%

25%

30%

88 89 90 91 92 93 94 95 96 97

Year

Percent of All Accidents 

Fatal Maintenance-related Accidents

Fatal GA Accidents

Figure 1. Percent of All Accidents That are Fatal: All GA Accidents Compared With

Maintenance-Related Accidents.
4

Type of Maintenance Activity. Table 3

presents the frequency and percent of each

maintenance activity identified as a cause or

factor in the NTSB accident reports.

Of the 1,474 NTSB maintenance-related

GA accident reports analyzed, 295 (20.0%)

cited installation as a primary cause or factor

in the accident. The next three most frequently

occurring maintenance activities included

maintenance (n = 217, 14.7%), maintenance

inspection (n = 202, 13.7%), and annual inspection (n = 124, 8.4%). Maintenance activities that accounted for less than 4% of the total

were combined into the Other category. Some

of these maintenance activities include compliance with an AD, replacement, major repair,

design change, and major overhaul. As a result of

the method in which the sample was obtained,

some reports contained NTSB subject codes that

were not “maintenance” codes. These are included in Table 3 as Non-maintenance.

Figure 2 presents the number of fatalities

and non-fatal injuries for each maintenance

activity. Installation problems were not only the most

frequently cited maintenance issue; they also resulted

in the most severe consequences. Accident reports

citing installation problems accounted for 100 fatalities

Table 3

Frequency of Maintenance Activity for all GA MaintenanceRelated Accidents

Maintenance Activity Frequency Percent

Installation 295 20.0

Maintenance 217 14.7

Maintenance Inspection 202 13.7

Annual Inspection 124 8.4

Service of Aircraft 91 6.1

Adjustment 82 5.5

Modification 62 4.2

Overhaul 59 4.0

Other 312 21.1

Non-maintenance a 30 2.0

Total 1,474 100.0

a

 Non-maintenance refers to codes used in the NTSB

accident reports that are not labeled as "maintenance."

Some examples include landing gear, tailwheel lock, flight

manuals, and radar assistance to VFR aircraft.

and 210 injuries. Installation problems, maintenance,

and maintenance inspection accounted for over 50%

of the fatalities in this sample.

0 20 40 60 80 100 120 140 160 180 200 220

Non-maintenance

Other

Overhaul

Service of Aircraft

Modification

Adjustment

Annual Inspection

Inspection

Maintenance

Installation

N

Injuries

Fatalities

Figure 2. Total Fatalities and Injuries by Type of Maintenance Activity for GA Maintenancerelated Accidents From 1988 to 1997.
5

Part 2: Installation Errors

Fatality or Injury. One hundred twenty-two (41%)

of the 295 installation accident reports cited no injuries

or fatalities. One hundred seventy-seven accident reports

(59%) cited injuries, fatalities, or both.

Type of Error. Table 4 presents the frequency and

percentage for each type of installation error. Table 5

presents the odds for each type of error resulting in a

fatality or injury. Two hundred ninety cases contained

sufficient information to supply a valid code for Type of

error. Five reports did not include enough information to

classify type of installation error; these cases were excluded from analysis. Incorrect attachment was the most

frequently occurring type of installation error in this

sample, n = 83. Installing the wrong part, however,

resulted in a greater likelihood of injury. This type of

error was 1.882 times more likely to result in a fatality or

injury than to result in no fatality or injury. Omitting a

component during the installation was the third most

frequently cited installation error in this sample (n = 63).

While the odds of an installation error producing an

injury or fatality range from 1.882 for installation of a

wrong part to 1.172 for an omission, the presence or

absence of a fatality or injury was not statistically dependent on the type of installation error, χ2

(4, N = 288) =

1.83, p > .05.

Table 4

Installation Accidents: Frequency and Percent for Type of Error, Type of System, Inspected On time,

Certified Mechanic, Operational Impact, and Fatality or Injury.

Installation Variable Level Frequency Percent

Incorrect Attachment 83 28.6

Incorrect Connection 64 22.1

Type of Error Omission 63 21.7

Wrong Part 49 16.9

Reversed Installation 29 10.0

Total 290 97.3

Powerplant 163 56.2

Flight Controls 39 13.4

Landing gear 30 10.3

Type of System Rotor System 31 10.7

Electrical System 15 5.2

Wing 6 2.1

Fuselage 3 1.0

Flight/Navigation Instruments 3 1.0

Total 290 99.9

Yes 31 91.2 Certified Mechanic No 3 8.8

Total 34 100.0

Emergency Landing 253 85.8

Operational Impact Fly to Destination 32 10.9

Return to Departure Airport 9 3.1

Total 294 99.8

Yes 175 59.3 Fatality or Injury No 120 40.7

Total 295 100.0
6

Type of System. Table 4 presents the frequency

and percentage for each type of aircraft system involved in the installation procedure. Table 5 presents

the odds of an installation error for each type of system

resulting in a fatality or injury. Two hundred and

ninety cases contained enough information to assign

a code for type of aircraft system. The remaining five

cases were excluded from analysis. The largest proportion of errors were committed during powerplant

installations (n = 163, 56.2%). Installation errors

associated with the flight controls were the second

most frequent category of aircraft systems (n = 39,

13.4%). Installation errors on the electrical system

were reported in 15 (5.2%) of the accidents. Only

three reports (1.0%) cited installation errors on the

flight/navigation instruments.

While powerplant installations were a cause or

factor in over half of the accidents in this sample,

installation errors on the flight controls or electrical

system were more likely to result in an injury or death

(odds = 2.250 and 2.750, respectively). The odds of

an installation error producing an injury or fatality

ranged from 0.200 for an installation error on the

landing gear to 2.750 for installation errors on the

electrical system. Chi-square analysis on the type of

system by fatality or injury versus no fatality or injury

Table 5

Installation Accidents: Crosstabulation and Odds for Fatality or Injury by Type of Error, Type of

System, Certified Mechanic, and Operational Impact.

Installation Variable Level Fatality or Injury Involved?

Yes No Odds

Incorrect Attachment 50 33 1.515

Incorrect Connection 36 28 1.285

Omission 34 29 1.172

Wrong Part 32 17 1.882

Type of Error

Reversed Installation 18 11 1.636

Total 171 119 1.436

Powerplant 101 62 1.629

Flight Controls 27 12 2.250

Rotor System 16 15 1.066

Electrical System 11 4 2.750

Landing gear 5 25 0.200

Wing 6 0 0.000

Flight/Navigation

Instruments

3 0 0.000

Type of System

Fuselage 1 2 0.500

Total 170 120 1.416

Yes 19 12 1.583 Certified Mechanic No 1 2 0.500

Total 20 14 1.428

Emergency Landing 165 88 1.875

Operational Impact Fly to Destination 7 25 0.280

Return to Departure Airport 2 7 0.285

Total 174 120 1.450
7

cross tabulation resulted in a significant test of independence χ2

(7, N = 290) = 33.43, p < .005. Cramer’s

V coefficient was also significant, φc

 = .340, p < .005.

Thus, the presence of a fatality or injury is statistically

dependent on the type of aircraft system involved in

the installation error. The significant Cramer’s V

coefficient suggests a moderately strong relationship

between fatality or injury and type of aircraft system.

Certified Mechanic. Only 34 out of the 300, or

11.3%, of the installation accident reports indicated

whether a certified mechanic performed the installation work. Of these 34, 31 (10.3%) verified that a

certified mechanic performed the installation. Three

cases reported that the mechanic performing the installation was not certified. Two hundred sixty-six

cases were coded with a missing value. A chi-square

analysis was not performed due to the small cell sizes.

Operational Impact. Table 4 presents the frequencies for the operational impact categories. Two hundred ninety-four reports contained sufficient

information to assign a value for operational impact.

In the vast majority of the cases (85.8%), the pilot had

to execute an emergency landing. Only nine (3.1%) of

the aircraft were able to return to the departure airport. Thirty-two (10.9%) of the aircraft were successfully flown to the intended destination.

Table 5 presents the odds of the operational impact

resulting in a fatality or injury. Aircraft returning to the

departure airport after experiencing an in-flight problem

greatly reduced the chance of a fatality or injury (odds =

0.285) as did aircraft flying to the intended destination

(odds = 0.280). Aircraft making an emergency landing

were 1.81 times more likely to produce a fatality or injury

than no fatality or injury. The chi-square analysis for

operational impact by fatality or injury versus no

fatality or injury was significant at χ2

(2, N = 294) =

27.34, p < .005. Cramers V coefficient was also

significant, φc

 = .305, p < .005.

DISCUSSION

Recent studies that have assessed the frequency of

maintenance-related commercial, naval, and GA accidents have found an accident rate close to 20% (see

Murray, 1998; Schmidt, Schmorrow, & Hardee,

1998). The current study found that 7.05% of all GA

accidents occurring between 1998 and 1997 were

attributed to a maintenance-related cause or factor.

Due to the method used to obtain the sample in this

study, the authors believe that 7.05% is a conservative

estimate of GA maintenance-related accidents during

this period. NTSB accident investigators report the

probable cause of an accident with a subject code.

NTSB accident reports that contain a subject code not

classified as a maintenance code (e.g., “22000-Landing Gear”) would not have been included in this

sample but may have been involved in a “maintenance-related” accident. As a result, there are probably many more maintenance-related accident reports

in the NTSB Database that were not included in this

study because they were not designated with a maintenance code.

The most frequently occurring maintenance activity in this sample was installation. Accident reports

that identified installation as a cause or factor accounted for more fatalities than any other maintenance activity. Maintenance and maintenance inspection

were the second and third (respectively) most frequent maintenance activities. In addition, installation, maintenance, and maintenance inspection

accounted for more than 50% of the fatalities in this

sample. Since installation is the most ubiquitous maintenance activity (most maintenance activities could

be described as an “installation”), rigorous study of

the underlying human behavior is needed. The various categories associated with installation errors (incorrect attachment, omissions, wrong parts, etc.)

suggest that the human factors of these events may

span a broad range of concerns. For example, omissions may involve attentional lapses, distractions,

complex installation instructions, or incomplete training. To better understand the importance of these

other human factors, more extensive data are needed

regarding the specific maintenance activities. Future

studies could look at the behavioral and cognitive

factors involved in the day-to-day successful execution of installation procedures.

Maintenance inspection is typically the last line of

defense in an aircraft maintenance operation. Maintenance inspections and annual inspections together

were cited in 22% of the fixed-wing accidents. Thus,

it is surprising that so little information is included in

the accident reports concerning the maintenance and

inspection history of each aircraft. Indeed, most of the

reports in this sample contained no maintenance or

inspection history at all. The effectiveness of current

inspection practices is difficult to assess without a

prior maintenance history. The relatively high frequency of accident reports citing inspection as a

probable cause may suggest that the training GA

inspectors receive —as well as the regulations guiding

inspection practices— may need to be reevaluated.
8

The maintenance activity categorized as “Maintenance” is difficult to interpret due to the ambiguous

name. The authors speculate that this code is used

either to refer to routine maintenance activities (e.g.,

an oil change) or when the accident was determined to

be maintenance-related, but information regarding

the specific maintenance activity was not discovered

during the course of the investigation. The ambiguity

of this category of maintenance activity is somewhat

troubling since it is the second most frequently cited

maintenance activity in this sample.

Fixed-wing aircraft were involved in the majority

of accidents (85.7%) from 1988-1997. This is not

surprising since fixed-wing aircraft are the most common type of GA aircraft (in 1996, 86% of GA aircraft

were fixed-wing airplanes; FAA, 1996). However,

helicopters, which in 1996 comprised only 3% of GA

aircraft (FAA, 1996), were involved in 12.4% of the

maintenance-related accidents. Helicopters, which

are already well known for their high maintenance

requirements, may be especially prone to maintenance-related accidents. However, the type of maintenance activities reported as causal factors in this study

were identical to those found for fixed-wing aircraft,

installation and inspection. This suggests that the

maintenance errors being committed are aircraft-independent and efforts to manage human error in

installation and inspection could greatly increase safety

for all types of aircraft. Other GA aircraft such as

gliders, gyroplanes, balloons, and ultralights, comprised such a small portion of this sample that no

conclusions could be made.

Maintenance installation errors such as reversed installation and omission have been cited in other studies

(Graeber and Marx, 1993; Hobbs & Williamson, 2001)

as common errors in the maintenance environment. The

current study found that incorrect attachment and incorrect connection were the most frequent categories of

installation errors in this sample. The distinction between a connection and an attachment may seem slightly

ambiguous, but the underlying human behaviors may be

quite different. For instance, an incorrect attachment

could be the result of a lapse in concentration or incomplete documentation in the manual. An incorrect connection may occur because of damaging one part of an

aircraft (e.g., a fuel line) while attempting to service

another part of the aircraft. These differences may require separate strategies for study and intervention.

Installation of components can be required in any

of the numerous aircraft systems, and some systems

are more critical to safety than others. In fact, the

significant chi-square test for type of system by fatality or injury versus no fatality or injury suggests that

the outcome of the accident (fatality or injury) is

dependent on the type of system upon which the

installation error was committed. Powerplant installation errors were the most prevalent in all accidents.

This could be because of the central role played by the

powerplant, its complexity, or other factors such as

limited access to engine components inherent in aircraft design, particularly small aircraft. Although occurring less frequently, the odds of a fatality or injury

increased when the installation error involved flight

controls or the electrical system.

GA maintenance technicians must perform many

different maintenance tasks across a wide array of

aircraft types to keep them airworthy. Understanding

which maintenance activities pose the greatest risk is

crucial to developing an effective error management

and prevention program. While we are not necessarily

advocating the total adoption of Operational Risk

Management (ORM) techniques as used by the military services (for example, see Air Force Pamphlet 90-

902, 14 December 2000, available: http://

afpubs.hq.af.mil), it seems reasonable to develop guidance to aid maintainers on the inherent risks of

maintaining various general aviation aircraft. These

guidelines could be empirically developed, informed by

accident and incident event data. Thus, a comprehensive

database of maintenance error data becomes crucial.

 Marx (1997) has proposed that the aviation industry move towards 100% error reporting in maintenance. Marx’s reasoning is that nearly every mechanical

failure is investigated and archived so that the failure

rate of a specific type of component can be analyzed

and precisely tracked. However, the same investigative and analytical resources are not applied to cases of

human error in the maintenance shop. Marx suggests

that a major obstacle to 100% error reporting in

maintenance is the punitive work environment so

pervasive industry-wide. Many aviation maintenance

technicians (AMTs) may hesitate to report their own

errors for fear of reprisal from management or government. Therefore, any maintenance-error reporting

system will likely require some level of immunity to

disciplinary action to be successful. These essential

issues will require consideration as a comprehensive

maintenance human factors program and errorreporting system are developed and implemented.
9

REFERENCES

Allen, J. & Marx, D. (1993). Maintenance Error Decision Aid Project (MEDA). Proceedings of the Eighth

Conference on Human Factors Issues in Aircraft

Maintenance and Inspection, Washington, D.C.

Federal Aviation Administration (1996). Statistical Handbook of Aviation. Available: http://api.hq.faa.gov/

handbook96/TOC96.HTM.

Graeber, R.C. & Marx, D.A. (1993). Reducing human

error in aircraft maintenance operations. Paper presented at the Flight Safety Foundation 46th Annual

International Air Safety Seminar, Kuala Lumpur,

Malaysia.

Hobbs, A. & Williamson, A. (2001). Aircraft Maintenance Safety Survey— Results Department of Transport and Regional Services, Australian Transport

Safety Bureau. Available: http://www.basi.gov.au/

sprog/mntcsur.htm.

Marx, D.A. (1997). Moving toward 100% error reporting

in maintenance. Proceedings of the Eleventh Conference on Human Factors Issues in Aircraft Maintenance and Inspection, Washington, DC. Available: http://hfskyway.faa.gov.

Murray, B. (1998). Psychology is key to airline safety at

Boeing. APA Monitor Online, 29(5). Available:

http://www.apa.org/monitor/may98/

homepage.html.

National Transportation Safety Board (2001a). Accidents, fatalities, and fates, 2000 preliminary statistics. Available: http://www.ntsb.gov/aviation/

Table1.htm.

National Transportation Safety Board (2001b). Accidents, fatalities, and rates, 1982 through 2000, for

US air carriers operating under 14 CFR 121, scheduled and nonscheduled service. Available: http://

www.ntsb.gov/aviation/Table5.htm.

National Transportation Safety Board (2001c). Accidents, fatalities, and rates, 1982 through 2000,U.S.

General Aviation. Available: http://www.ntsb.gov/

aviation/Table10.htm.

National Transportation Safety Board (2001d). Reporting an Accident to the NTSB. Available: http://

www.ntsb.gov/aviation/report.htm.

National Transportation Safety Board (1998). Aviation

Coding Manual. Available: http://www.ntsb.gov/

avdata/codman.pdf.

Reason, J. (1998). Broadening the cognitive engineering horizons: more engineering, less cognition and

no philosophy of science, please. Ergonomics, 41(2),

150-2.

Schmidt, J.K., Schmorrow, D. & Hardee, M. (1998). A

preliminary analysis of naval aviation maintenance

related mishaps. Society of Automotive Engineers,

107, 1305-9.

Veinott, E.S. and Kanki, B.G. (1995). Identifying human factors issues in aircraft maintenance operations. Proceedings of the Human Factors and Ergonomics Society 39th Annual Meeting, USA, 950.