N

November 2013 

NASA/TM-2013-218059 

Systems Analysis of NASA Aviation Safety 

Program: Final Report 

Sharon Monica Jones 

Langley Research Center, Hampton, Virginia 

Mary S. Reveley and Colleen A. Withrow 

Glenn Research Center, Cleveland, Ohio 

Joni K. Evans 

Analytical Mechanics Associates, Inc., Hampton, Virginia 

Lawrence C. Barr 

Volpe National Transportation Systems Center, Cambridge, Massachusetts 

Karen Leone 

Vantage Partners, LLC, Brook Park, Ohio 
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Space Administration 

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Hampton, Virginia 23681-2199 

 N

November 2013 

NASA/TM-2013-218059 

Systems Analysis of NASA Aviation Safety 

Program: Final Report 

Sharon Monica Jones 

Langley Research Center, Hampton, Virginia 

Mary S. Reveley and Colleen A. Withrow 

Glenn Research Center, Cleveland, Ohio 

Joni K. Evans 

Analytical Mechanics Associates, Inc., Hampton, Virginia 

Lawrence C. Barr 

Volpe National Transportation Systems Center, Cambridge, Massachusetts 

Karen Leone 

Vantage Partners, LLC, Brook Park, Ohio 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

Acknowledgments 

Thanks are extended to the members of the Joint Implementation and Data Analysis 

Team (JIMDAT), the Old Dominion University Department of Engineering Management 

and the managers and researchers of the NASA Aviation Safety Program. 
i 

Contents 

Executive Summary ....................................................................................................................................................... 1

1. Introduction ............................................................................................................................................................... 2

1.1 Background .......................................................................................................................................................... 2

1.2 Study Objectives and Deliverables ...................................................................................................................... 2

2. Aviation Statistical Data Analysis ............................................................................................................................. 3

2.1 Introduction ......................................................................................................................................................... 3

2.2 Methodology ........................................................................................................................................................ 4

2.3 Results and Discussion ........................................................................................................................................ 4

2.4 Conclusions from the Statistical Analysis Results ............................................................................................. 11

2.5 Statistical Analysis Medical Transport Accidents for the Period 19902008 ................................................... 11

3. Qualitative Future Safety Risk Identification .......................................................................................................... 14

4. Top-Down Systems Analysis .................................................................................................................................. 24

4.1 Top-Down Systems Analysis Methodology ...................................................................................................... 24

4.2 NASA AvSafe Program Goal and Objectives ................................................................................................... 25

4.3 Portfolio Assessment Criteria ............................................................................................................................ 27

4.4 Assessment of Current Portfolio ........................................................................................................................ 29

4.5 Set of Challenging Safety Issues ....................................................................................................................... 43

4.6 Research Alternatives ........................................................................................................................................ 44

5. Discussion and Conclusions .................................................................................................................................... 46

References ................................................................................................................................................................... 48

Appendix A. Aviation Occurrence Categories ............................................................................................................ 50

CICTT Categories .................................................................................................................................................... 50

Additional Categories .............................................................................................................................................. 52

Appendix B. Accidents, Injuries, and Incidents by Aviation Occurrence Category .................................................... 54

Appendix C. Total Accidents and Fatal Accidents by Aviation Occurrence Category ............................................... 59

Appendix D. Integrated Resilient Aircraft Control (IRAC) Technology List ............................................................. 63
ii

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1 

Executive Summary 

A three-month study (February to April 2010) of the NASA Aviation Safety (AvSafe) program was 

conducted. This study comprised three components: (1) a statistical analysis of currently available civilian 

subsonic aircraft data from the National Transportation Safety Board (NTSB), the Federal Aviation 

Administration (FAA), and the Aviation Safety Information Analysis and Sharing (ASIAS) system to 

identify any significant or overlooked aviation safety issues; (2) a high-level qualitative identification of 

future safety risks, with an assessment of the potential impact of the NASA AvSafe research on the 

National Airspace System (NAS) based on these risks; and (3) a detailed, top-down analysis of the NASA 

AvSafe program using an established and peer-reviewed systems analysis methodology. 

The statistical analysis of NTSB accident and FAA incident data from 1997 to 2006 identified the top 

“tall poles” based on four types of Federal Aviation Regulations (FAR) operations (Part 121, Part 135 

scheduled, Part 135 non-scheduled and Part 91). The data were categorized using the Commercial 

Aviation Safety Team/International Civil Aviation Organization (CAST/ICAO) Common Taxonomy. The 

only tall poles that were common to all four of the FAR operations were “Fire-Post Impact”, “Loss of 

Control – In Flight”, “System Component Failure or Malfunction (Powerplant)” and “System Component 

Failure or Malfunction (Non-Powerplant)”. 

Multiple external sources (e.g., the National Transportation Safety Board’s “Most Wanted List”) were 

used to develop a compilation of future safety issues/risks. The ten “tall poles” in future safety risk are as 

follows: 

x runway safety 

x approach and landing accident reduction 

x loss of control – in flight 

x icing/ice detection 

x super density operations (air traffic management under conditions of increased traffic volume) 

x human fatigue 

x increasing complexity and reliance on automation 

x aircraft mixed fleet equipage 

x inadequate protection 

x sharing and dissemination of safety data 

x enhanced survivability in the event of an accident. 

The top-down analysis of the NASA AvSafe program was conducted by using a modification of the 

Gibson methodology. The results of the aviation statistical data analysis, the qualitative future safety risk 

identification, the literature search, and additional input from subject matter experts were used to 
2 

summarize a top-down set of goals and objectives for the AvSafe program and to develop a set of criteria 

for evaluating the research portfolio. These criteria were used to draw the following conclusions: 

x The current NASA aviation safety research portfolio directly addresses all of the National 

Aeronautics R&D goals, with the exception of goal 3, “develop enhanced passenger and crew 

survivability in the event of an accident.” 

x The current portfolio, if successful, would indirectly impact over 50 percent of the historic and future 

safety “tall poles.” 

– Most of the current projects contain a large amount of research that is at the fundamental level. 

– Most of the research directly impacts Part 121 operations. The only research that is directly 

applicable to Part 91 is in the area of “system component failure.” 

Of the 17 challenging safety issues that were identified, 11 are directly addressed by the current 

AvSafe program research portfolio. 
2 

1. Introduction 

1.1 Background 

The NASA Aeronautics Research Mission Directorate (ARMD) is focused on performing cutting 

edge, fundamental research in traditional aeronautics research disciplines. According to the ARMD Web 

site (Ref. 1), this research is based on three key principles: 

“1. We will dedicate ourselves to the mastery and intellectual stewardship of the core 

competencies of aeronautics for the nation in all flight regimes. 

 2. We will focus our research in areas that are appropriate to NASA's unique capabilities. 

3. We will directly address the fundamental research needs of the Next Generation Air 

Transportation System (NextGen) in partnership with the member agencies of the Joint 

Planning and Development Office (JPDO).” 

The charter of the Aviation Safety (AvSafe) program in 2010 within the ARMD was to conduct 

research to improve “the safety of current and future aircraft operating in the National Airspace System” 

(Ref. 2). The ARMD management uses information from a variety of sources, both internal and external, 

to guide their technical, programmatic, and budgetary decisions. In 2010, the ARMD had a need for a 

detailed systems analysis of the AvSafe program to obtain additional information for their portfolio 

decision process. 

1.2 Study Objectives and Deliverables 

The overarching objective of this study was to identify a set of challenging safety issues that can be 

addressed in NASA’s aviation safety research portfolio. The results of this study could help NASA 

management better assess the potential impact of NASA’s research portfolio on aviation safety and 

identify any gaps between areas that were being worked and those that needed to be addressed. The study 

specifically comprises three components: (1) a statistical analysis of currently available civilian subsonic 

aircraft data from the National Transportation Safety Board (NTSB), the Federal Aviation Administration 

(FAA), and the Aviation Safety Information Analysis and Sharing (ASIAS) to identify significant and 

overlooked aviation safety issues; (2) a high-level qualitative identification of future safety risks, with an 

assessment of the potential impact of the NASA AvSafe research on the National Airspace System (NAS) 

based on these risks; and (3) a detailed top-down analysis of the NASA AvSafe program using an 

established and peer-reviewed systems-analysis methodology. 
3 

2. Aviation Statistical Data Analysis 

While many experts in the aviation community have often stated that the aviation events (accidents 

and incidents) in the past may not necessarily reoccur in the future, there is still the potential for some of 

these events to happen again in the future. This section contains an analysis of currently available civilian 

subsonic aircraft accident and incident data to identify to any significant or overlooked aviation safety 

issues. A detailed examination of medical transport aircraft data is also included in this section. 

2.1 Introduction 

The primary purpose of the analysis reported here is to identify the types of accidents with the greatest 

impact on the overall safety risk in U.S. civil aviation. The safety risk is here defined to include the 

number of total accidents, fatal accidents and incidents, and the number of total injuries and fatalities. 

The NTSB is an independent federal agency that investigates every civil aviation accident in the 

United States, as well as significant accidents in other modes of transportation. The NTSB also conducts 

special investigations and safety studies and issues safety recommendations to prevent future accidents. 

The information that is collected during these investigations resides in the NTSB Aviation Accident and 

Incident Data System. A copy of this database in Microsoft Access format was obtained from the ASIAS 

department of the FAA’s Office of Aviation Safety in April 2009. 

The NTSB database includes events that involve a wide variety of aircraft (e.g., airplanes, helicopters, 

hot-air balloons, gliders, and ultralight aircraft) operating under various FARs (e.g., Part 91: General 

Aviation; Part 121: Commercial Air Carriers; Part 129: Foreign Air Carriers; Part 135: Commuters and 

On-Demand Air Taxis; and Part 137: Agricultural Operations). In March 1997, FAR Part 121 was 

changed to be applicable to all commuter operations with 10 or more passengers. Previously, FAR Part 

135 regulations were applicable to commuter operations with less than 44 passengers, and FAR Part 121 

was applicable to operations involving 44 or more passengers. 

The NTSB considers each event to be either an accident or an incident, based on the following 

definitions (Ref. 3): 

Accident: An occurrence that is associated with the operation of an aircraft, which takes place between 

the time that any person boards the aircraft with the intention of flight and the time that all 

such persons have disembarked, and in which any person suffers death or serious injury or in 

which the aircraft receives substantial damage. 

Incident: An occurrence, other than an accident, that is associated with the operation of an aircraft and 

that affects or could affect the safety of operations. 

Any injury or aircraft damage that occurs when there was no intent for flight (e.g., high-speed taxi 

tests, movement of the aircraft around the airfield, or maintenance run-ups) is, by definition, an incident. 

The NTSB does not investigate all incidents; however, all incidents and accidents are reported to the 

FAA (which is an agency within the Department of Transportation) by pilots, airport personnel, and 

private citizens. The FAA maintains a database that contains the information that is received in these 

reports and obtained in any subsequent investigation. A copy of the FAA Accident/Incident Data System 

(AIDS) in Microsoft Access format was obtained from the ASIAS office in October of 2007. 
4 

2.2 Methodology 

All recorded accidents and incidents that involved commercially built fixed-wing airplanes operating 

under FAR Part 121, Part 135, or Part 91 were included in this analysis, regardless of the state of the 

investigation (i.e., a preliminary stage versus finalized) and the location of the event (i.e., whether it 

occurred within or outside the U.S.). Home-built or experimental aircraft were excluded, as were 

helicopters, ultralight aircraft, gliders, and balloons. Also excluded were sky-diving incidents in which the 

main issue involved the parachute or the parachutist rather than the aircraft that was carrying the sky 

divers or the pilot of that aircraft. 

Among the incidents in this analysis were some midair collisions and ground collisions between 

multiple aircraft. The AIDS database includes a record for each aircraft involved, unless the aircraft was 

parked and unoccupied. To reduce the analysis data set to one record per incident, each incident that 

involved multiple aircraft was reviewed, and the report for the passive aircraft (i.e., the aircraft that was 

hit during the collision) was eliminated. This procedure was not followed for the accident data. 

Each accident that is included this report was assigned an occurrence category based on the taxonomy 

(Ref. 4) that was developed by the CAST/ICAO Common Taxonomy Team (CICTT). The author added 

several additional categories to this taxonomy for nontransport accidents; the details for all categories are 

provided in Appendix A. Categories were assigned by means of a computer program based on the 

occurrence codes and causal factor codes from the NTSB database. During the assignment process, many 

of the more complicated accidents were reviewed by the authors, and all of the fatal accidents for Part 121 

and Scheduled Part 135 were reviewed by aviation safety program staff. Certain accidents were assigned 

multiple occurrence categories. 

One CICTT specification was not followed. This change was with regard to loss of control when a 

system/component failure or malfunction rendered an aircraft uncontrollable. The CICTT taxonomy states 

that the loss of control should not be considered a separate category in these cases. However, for the 

purposes of this analysis, the loss-of-control category was retained for all circumstances, regardless of 

cause, in order to capture all loss-of-control events, including those that followed a system/component 

failure/malfunction or other circumstances (e.g., incapacitation, weather) that might have rendered the 

aircraft uncontrollable. 

The incident data were not categorized according to the occurrence taxonomy. A single incident 

category was assigned to each incident to describe the primary occurrence. For example, if a 

system/component failure or malfunction occurred, the incident was classified according to the 

malfunctioning system, regardless of consequences (e.g., loss of control, gear-up landing, or runway 

excursion). Details regarding the incident classifications are available in another paper (Ref. 5). For the 

purposes of this analysis, the CICTT categories were mapped to the incident categories without additional 

review of the specific incident. 

2.3 Results and Discussion 

Figure 1 shows the accident rate (per 1 million flight hours) over time for each of the four types of 

flight operations. Data for total flight hours per year were obtained from tables published by the NTSB, 

which were based on data provided by the FAA. The lowest accident rates continue to be for Part 121 

operations (large transport aircraft), while the highest rates are for Part 91 operations (general aviation). 

The greatest rate of decline during this ten-year time period was in Non-scheduled Part 135 operations 

(on-demand air taxi), while the greatest variation was in Scheduled Part 135 operations (commuter 
5 

airlines). In general, these statements are also true for fatal accident rates (see Fig. 2) and incident rates 

(see Fig. 3). 

Figure 1. Accident rates for four categories of flight operations (1997–2006). 

Figure 2. Fatal accident rates for four categories of flight operations (1997–2006). 

Figure 3. Incident rates for four categories of flight operations (1997–2006). 
6 

Although both the total accident and fatal accident rates show some evidence of decline for every 

flight operations category, the rates have remained disturbingly high for Part 91 and Part 135 operations 

relative to Part 121 operations. Additionally, the data indicate an increase in the rate of incidents for 

Scheduled Part 135. The frequencies of occurrence for each CICTT occurrence category for each type of 

flight operations are shown in a series of tables given in Appendix B. 

The total numbers of accidents, incidents, and injuries for each category of flight operations also are 

provided in the tables. The percentages that are examined in this study are generated based on these totals. 

The reader is reminded that a particular accident may be assigned multiple occurrence categories (i.e., 

more multiple causes may have contributed to a given accident). The additional categories that are not 

part of the official CICTT taxonomy are denoted with an asterisk (*). Although the tables are organized 

by outcome (i.e., accident, incident, or injury), the discussion here is organized according to the flight 

operations under which the aircraft was operating at the time of the event. The most frequently occurring 

causes of the events within each category of flight operations were selected from each table. The actual 

number of categories that were selected varies, but in each case a clear demarcation in percentages exists 

to distinguish those that were selected from those that were not selected. Appendix C contains a number 

of charts that show the total number of accidents and fatal accidents for each type of occurrence (or cause) 

for each category of flight operations. 

Part 121 

The occurrence categories that were factors in more than 10 percent of Part 121 accidents were ground 

handling (26 percent) and turbulence encounter (25 percent). The following factors had the highest 

incidences of injuries: turbulence encounter (30 percent), post-impact fire (26 percent), and in-flight loss 

of control (21 percent). The largest numbers of fatal accidents occurred for ground handling (40 percent), 

post-impact fire (28 percent), in-flight loss of control (24 percent), and non-powerplant system/ 

component failure (20 percent). The largest numbers of fatalities occurred for in-flight loss of control (54 

percent), post-impact fire (48 percent), the terrorist attacks of 9/11 (35 percent), and abrupt maneuvering 

(35 percent). For Part 121 incidents, the only categories that were factors in more than 5 percent of the 

total number of incidents were non-powerplant system/component failure (44 percent), powerplant 

system/component failure (16 percent), and ground handling (11 percent). 

In summary, the following factors contributed the most to the overall safety risk for Part 121 

operations: abrupt maneuver, post-impact fire, ground handling, in-flight loss of control, powerplant 

system/component failure, non-powerplant system/component failure, security-related event, and 

turbulence encounter. 

Scheduled Part 135 

The categories that were factors in more than 10 percent of the total number of accidents that occurred 

for Scheduled Part 135 operations were runway excursion (18 percent), in-flight loss of control (14 

percent), abnormal runway contact (13 percent), controlled flight into or toward terrain (CFIT) (12 

percent), bird strike (10 percent), icing (10 percent), and non-powerplant system/component failure (10 

percent). The occurrence categories that included more than 20 percent of the total number of injuries were 

in-flight loss of control (49 percent), icing (35 percent), and post-impact fire (33 percent). The factors that 

had the highest numbers of fatal events and total number of fatalities were in-flight loss of control (53 

percent of fatal events and 76 percent of fatalities), CFIT (27 percent of fatal events and 18 percent of 

fatalities), icing (20 percent of fatal events and 59 percent of fatalities), and post-impact fire (20 percent of 

fatal events and 50 percent of fatalities). Among Scheduled Part 135 incidents, the categories that were 
7 

factors in more than 10 percent of the total number of incidents were non-powerplant system/component 

failure (37 percent), powerplant system/component failure (13 percent), and ground handling (12 percent). 

In summary, the following factors contributed the most to the overall safety risk for Scheduled Part 

135 operations: abnormal runway contact, bird strike, CFIT, post-impact fire, ground handling, icing, inflight loss of control, runway excursion, powerplant system/component failure, and non-powerplant 

system/component failure. 

Non-Scheduled Part 135 

The three categories that were most frequently factors in Non-Scheduled Part 135 accidents were inflight loss of control (17 percent), runway excursion (15 percent), and post-impact fire (13 percent). The 

factors for which more than 15 percent of the total number of injuries occurred were in-flight loss of 

control (33 percent), post-impact fire (30 percent), and CFIT (19 percent). Similarly, the three factors that 

had the highest percentages for both the total number of fatal events and the total number of fatalities were 

in-flight loss of control (46 percent of fatal events and 51 percent of fatalities), post-impact fire (41 percent 

of both fatal events and fatalities), and CFIT (26 percent of fatal events and 27 percent of fatalities). The 

categories that were factors for more than 10 percent of Non-Scheduled Part 135 incidents were nonpowerplant system/component failure (40 percent) and powerplant system/component failure (14 percent). 

In summary, the following factors contributed the most to the overall safety risk for Non-Scheduled 

Part 135 operations: CFIT, post-impact fire, in-flight loss of control, runway excursion, powerplant 

system/component failure, and non-powerplant system/component failure. 

Part 91 

The five categories that were most frequently factors in Part 91 accidents were runway excursion (20 

percent), in-flight loss of control (20 percent), on-ground loss of control (15 percent), abnormal runway 

contact (13 percent), and fuel-related loss of engine power (13 percent). The categories for which more 

than 10 percent of the total number of injuries occurred were in-flight loss of control (40 percent), postimpact fire (24 percent), collision with an object/obstacle during takeoff or landing (15 percent), fuelrelated loss of engine power (15 percent), and low-altitude operations (11 percent). The categories that 

had the highest number of fatal events and the highest number of fatalities were in-flight loss of control 

(55 percent of fatal events and 56 percent of fatalities), post-impact fire (36 percent and 38 percent), lowaltitude operations (18 percent and 16 percent), and CFIT (13 percent of both fatal events and fatalities). 

The most frequently occurring factors for incidents in Part 91 operations were non-powerplant 

system/component failure (27 percent), abnormal runway contact (25 percent), powerplant system/ 

component failure (10 percent), and runway excursion (9 percent). 

In summary, the following factors contributed the most to the overall safety risk for Part 91 operations: 

abnormal runway contact, CFIT, collision with object/obstacle during takeoff or landing, post-impact fire, 

low-altitude operations, in-flight loss of control, on-ground loss of control, fuel-related loss of engine power, 

runway excursion, powerplant system/component failure, and non-powerplant system/component failure. 

Table 1 summarizes the impact of each category that was found to be a top contributor to the safety 

risk within each flight operations category. The absence of summary statistics for a particular occurrence 

category within a particular flight operations category should not lead the reader to conclude that no 

events for that flight operations category occurred for the given occurrence category. Rather, the number 
8 

of events assigned to that occurrence category may not have been large enough for it to be considered a 

major contributor to the safety risk. The following abbreviations are used in the tables: 

TA: Total accidents 

TAI: Total accident injuries 

FA: Fatal accidents 

TF: Total fatalities 

TI: Total incidents 

Table 1. Most Frequently Cited CICTT Occurrence Categories (1997–2006) 

CICTT Occurrence 

Category Part 121 Scheduled 

Part 135 

Non-Scheduled 

Part 135 Part 91 

Abrupt maneuver 35% of TF 

Abnormal runway contact 13% of TA 13% of TA 

25% of TI 

Bird strike 10% of TA 

Controlled flight Into terrain 

12% of TA 

27% of FA 

18% of TF 

19% of TAI 

26% of FA 

27% of TF 

13% of FA 

13% of TF 

Collision with object during 

takeoff or landing 15% of TAI 

Fire – post impact 

26% of TAI 

28% of FA 

48% of TF 

33% of TAI 

20% of FA 

50% of TF 

13% of TA 

30% of TAI 

41% of FA 

41% of TF 

24% of TAI 

36% of FA 

38% of TF 

Ground handling 

26% of TA 

40% of FA 

11% of TI 

12% of TI 

Icing 

10% of TA 

35% of TAI 

20% of FA 

59% of TF 

 

Low-altitude operations 

11% of TAI 

18% of FA 

16% of TF 

Loss of control – in flight 

21% of TAI 

24% of FA 

54% of TF 

14% of TA 

49% of TAI 

53% of FA 

76% of TF 

17% of TA 

33% of TAI 

46% of FA 

51% of TF 

20% of TA 

40% of TAI 

55% of FA 

56% of TF 

Loss of control – on ground 15% of TA 

Power loss – fuel 13% of TA 

15% of TAI 

Runway excursion 18% of TA 15% of TA 20% of TA 9% 

of TI 

System component failure – 

powerplant 16% of TI 13% of TI 14% of TI 10% of TI 

System component failure – 

nonpowerplant 

20% of FA 

44% of TI 

10% of TA 

37% of TI 40% of TI 27% of TI 

Security related 35% of TF 

Turbulence encounter 25% of TA 

30% of TAI 
9 

One accident (AA587 on 12NOV01) with abrupt maneuvering (which led to failure of the vertical 

stabilizer and a total loss of control) was responsible for 35 percent of the Part 121 fatalities in this time 

period. This was the same number of persons as were killed earlier that month in four aircraft on 

September 11th. Even this one accident highlights the need for stringent and comprehensive flight 

training. 

Abnormal runway contact was a major contributor to the safety risk in Scheduled Part 135 and Part 91 

operations (based primarily on the percentage of total accidents), but it was also a minor contributor for 

Part 121 and Non-Scheduled Part 135 operations (9 and 11 percent of total accidents, respectively). 

Bird strikes appear to be a problem primarily for Scheduled Part 135 flights but also accounted for 3 

percent of accidents and 3 percent of incidents for Part 121 operations. 

Controlled flight into terrain (CFIT) was a major contributor to the safety risk for all flight operations 

categories except Part 121. Safety enhancements such as terrain awareness and warning systems (TAWS) 

and enhanced ground proximity warning systems (EGPWS) have been invaluable; more recent 

technologies such as synthetic vision are too new to have had an impact on these data. 

Collision with an object or obstacle during takeoff or landing was primarily a Part 91 phenomenon; 

within Part 91, this factor accounted for 10 percent of all of the accidents, 9 percent of all of the fatal 

accidents, and 8 percent of the total number of fatalities. 

Post-impact fire is one of four accident categories that presented as a major contributor in every flight 

operations category. Accidents with post-impact fires accounted for 20 to 41 percent of all fatal accidents 

and 38 to 50 percent of the total number of fatalities. 

Ground handling accidents were most common in Part 121 but were not absent from other flight 

operations. Eight of the ten Part 121 fatal accidents with ground handling as a contributing factor resulted 

in a total of one fatality. 

Icing was as factor mostly for Scheduled Part 135 flights. Interestingly, 83 percent of the Scheduled 

Part 135 accidents for which icing was a factor occurred in Alaska (65 of 78), compared with 8.5 percent 

(1123 of 13,246) across the other flight operations categories. Similarly, two-thirds of the Scheduled Part 

135 fatal accidents occurred in Alaska (10 of 15), compared with 4.1 percent across the other flight 

operations categories (101 of 2475). 

Low-altitude operation is another factor that affected mostly Part 91 flight. In general, the percentages 

of accidents and injuries that were attributed to low-altitude operations in Part 91 were nearly twice those 

for Non-Scheduled Part 135 and four times those for Part 121 and Scheduled Part 135 operations. 

In-flight loss of control was an important part of the safety risk more as a result of the number of 

injuries, especially fatal injuries, than to the total number of accidents. The impact on fatalities was fairly 

consistent across all categories of flight operations (51 to 76 percent), with a spike in the number of 

injuries for Scheduled Part 135 operations. In-flight loss of control was so likely to result in injury or 

substantial aircraft damage that it was rarely categorized as a factor for incidents. For those incidents that 

did include in-flight loss of control as a contributing factor, the loss of control was nearly always 

preceded by a system or component failure/malfunction or severe weather, and control was regained prior 

to a collision. 
10 

On-ground loss of control (mostly ground loop and nose over or nose down) was another contributing 

factor that occurred most often in Part 91 operations. These Part 91 accidents were rarely fatal. 

Fuel-related loss of engine power also contributed significantly to the safety risk for Part 91 

operations; the percentages were only slightly lower for Non-Scheduled Part 135 operations as well. The 

loss of engine power per se was not the main problem in these accidents, but rather the inability to 

successfully complete an off-airport landing with little or no engine power. 

Runway excursion accounted for 15 to 20 percent of accidents across all categories of flight operations 

except Part 121 (8 percent). However, runway excursion in Part 121 resulted in higher percentages of 

injuries (13 percent), fatal accidents (12 percent) and fatalities (8 percent) than were seen in other flight 

operations categories. 

Both powerplant and nonpowerplant system/component failure/malfunction contributed to the safety 

risk mostly in terms of incidents. However, 20 percent of the fatal accidents for Part 121 operations (with 

18 percent of all Part 121 fatalities), 10 percent of Scheduled Part 135 accidents, and 11 percent of NonScheduled Part 135 accidents were attributed to nonpowerplant system/component failure/malfunction. 

For Non-Scheduled Part 135 accidents, the percentages for powerplant system/component failure/ 

malfunction were remarkably similar to those for fuel-related loss of engine power. 

Although the security-related occurrence category manifests itself in Part 91 in terms of suicides and 

stolen aircraft, security was a major contributor to the safety risk only in Part 121 operations (35 percent 

of total fatalities). 

Similarly, encounters with turbulence account for less than three percent of any accidents or injuries in 

flight operations categories other than Part 121. However, in Part 121, turbulence is responsible for 25 

percent of accidents and 30 percent of injuries, making it the single largest cause of injuries in this 

operations category. 

These 17 accident categories collectively were assigned to 89 percent of the accidents that occurred 

during the period 1997–2006 (Part 121: 86 percent; Scheduled Part 135: 85 percent; Non-Scheduled Part 

135: 83 percent; Part 91: 90 percent), 94 percent of the fatal accidents (Part 121: 100 percent; Scheduled 

Part 135: 100 percent; Non-Scheduled Part 135: 92 percent; Part 91: 94 percent), and 84 percent of 

incidents (Part 121: 82 percent; Scheduled Part 135: 80 percent; Non-Scheduled Part 135: 82 percent; Part 

91: 85 percent). 

Because several occurrence categories were major contributors to the safety risk for only one flight 

operations category, Table 2 shows the percentage of accidents or incidents that have been assigned to the 

set of occurrence categories specific to that category of flight operations. 
11 

Table 2. Number of Events Assigned to at Least One of the Most Frequent CICTT Occurrence Categories Within 

Each Category of Flight Operations (1997–2006) 

Type of outcome Part 121 Scheduled Part 

135 

Non-Scheduled 

Part 135 Part 91 

Total accidents 319 (69.5%) 57 (73.1%) 313 (58.0%) 10849 (88.6%) 

Total injuries 1754 (89.7%) 128 (90.1%) 437 (74.7%) 8961 (91.0%) 

Fatal accidents 23 (92.0%) 13 (86.7%) 102 (83.6%) 2150 (92.4%) 

Fatal injuries 750 (99.7%) 77 (96.3%) 249 (85.3%) 4125 (91.0%) 

Incidents 2881 (76.8%) 143 (76.1%) 677 (60.6%) 10320 (80.8%) 

2.4 Conclusions from the Statistical Analysis Results 

This analysis has identified four groups of occurrence categories (with between 6 and 11 categories 

per group) that contributed greatly to the safety risk within each of the flight operations categories. 

Collectively, the occurrence categories in these identified groups represent 89 percent of accidents and 84 

percent of incidents. Individually, these groups represent 58 to 89 percent of accidents and 61 to 81 

percent of incidents. In general, the occurrence categories that were most important to the safety risk 

across all categories of flight operations were post-impact fire and in-flight loss of control. 

2.5 Statistical Analysis Medical Transport Accidents for the Period 19902008 

A separate examination of accidents involving medical helicopters in the United States was conducted. 

The primary purpose of this statistical analysis was to describe the characteristics of accidents that 

involve U.S. civil aviation helicopter medical transports in order to determine whether this area of 

aviation safety requires additional attention. 

Table 3 provides some basic statistics that pertain to helicopter accidents that are entered in the NTSB 

database. The first row gives the total number of helicopter accidents between 1990 and 2008. The second 

row gives these totals after amateur-built helicopters, military aircraft, and helicopters operated by 

persons and businesses based outside the United States have been excluded. The third row gives these 

totals for only those accidents that involved medical transport helicopters. Not all of these flights had 

patients on board at the time of the accident; some were en route to pick up the ill or injured persons, and 

others were traveling back to their home base after delivering the patient to a hospital. 
12 

Table 3. Description of Helicopter Accidents 

Number of 

accidents 

Accidents with 

any injury 

Accidents with 

a fatal injury 

Helicopter was 

destroyed 

All helicopter accidents 3910 2019 (51.6%) 793 (20.3%) 958 (24.5%) 

Commercially built, 

U.S.-based civil helicopters 3424 1692 (49.4%) 590 (17.2%) 757 (22.1%) 

Medical transport 156 98 (62.8%) 63 (40.4%) 62 (39.7%) 

Eighty-eight percent of the helicopter accidents that are recorded in the NTSB database for the given 

time period involved commercially built, nonmilitary U.S.-based aircraft. These accidents tend to have 

less severe outcomes (in terms of injuries, fatalities, and aircraft destruction) than other helicopter 

accidents in the database. This observation is not surprising given that the NTSB is more likely to be 

involved in foreign or military accident investigation when the outcome is severe. 

Less than 5 percent of the recorded helicopter accidents involved medical transport, but these 

accidents have significantly more severe outcomes than the general helicopter accidents. More than twice 

as many medical transport accidents resulted in a fatality than commercially built, U.S.-based civil 

helicopters as a whole. Medical transport helicopters were twice as likely to be destroyed. In addition, the 

number of medical transport accidents increased substantially during the given time period (see Fig. 4), 

whereas the total number of helicopter accidents and the number of accidents that involved commercially 

built, U.S.-based nonmilitary helicopters has remained relatively constant or even declined slightly. 

Figure 4. Number of helicopter accidents in three subsets (note that the plotted line for medical transport accidents 

uses the axis on the right). 

These 156 medical transport accidents were assigned occurrence categories based on the taxonomy 

that was developed by the CICTT. The author added several categories to this taxonomy for non-transport 

accidents. Details on all of these categories can be found in Appendix A. Certain accidents were assigned 

multiple occurrence categories. 
13 

Table 4 shows the number of medical transport helicopter accidents that were assigned to each 

occurrence category. The most frequent causal factors among all accidents were in-flight loss of control 

(34 percent), collision with an object on takeoff or landing (21 percent), abnormal runway contact (20 

percent), and system/component failure/malfunction – powerplant (16 percent). For fatal accidents, the 

most frequent causal factors were in-flight loss of control (56 percent), CFIT (30 percent), and postimpact fire (25 percent). 

Table 4. CICTT Occurrence Categories for Medical Transport Helicopter Accidents 

CICTT Occurrence Category Number of 

accidents 

Number of 

fatal accidents 

Total accidents 156 63 

Abrupt maneuver 1 (0.6%) 

Abnormal runway contact 31 (19.9%) 2 (3.2%) 

Controlled flight into terrain 21 (13.5%) 19 (30.2%) 

Collision with object – takeoff or landing 33 (21.2%) 4 (6.3%) 

Collision with terrain – approach/landing* 5 (3.2%) 1 (1.6%) 

Fire – nonimpact 3 (1.9%) 

Fire – post impact 20 (12.8%) 16 (25.4%) 

Ground collision 1 (0.6%) 

Ground handling or preflight 7 (4.5%) 1 (1.6%) 

Low-altitude operations 3 (1.9%) 3 (4.8%) 

Loss of control – in flight 53 (34.0%) 35 (55.6%) 

Loss of control – on ground 5 (3.2%) 

Midair collision 2 (1.3%) 2 (3.2%) 

Power loss – fuel 5 (3.2%) 2 (3.2%) 

Power loss – unknown reason* 4 (2.6%) 3 (4.8%) 

System component failure – powerplant 25 (16.0%) 8 (12.7%) 

System component failure – nonpowerplant 7 (4.5%) 2 (3.2%) 

Unintended flight into IMC 9 (5.8%) 4 (6.3%) 

Unknown or undetermined 4 (2.6%) 2 (3.2%) 

* Denotes occurrence categories not in the official CAST/ICAO taxonomy. 
14 

3. Qualitative Future Safety Risk Identification 

This section provides a high-level qualitative identification of future safety risks (i.e., future tall 

poles). These risks are the basis for assessing the potential impact(s) of NASA’s aviation safety research 

in these areas on the National Airspace System. This section contains qualitative descriptions of critical 

areas of future safety risk in the air transportation system. The information was compiled from a variety 

of sources, including: 

1. Decadal Survey of Civil Aeronautics (National Research Council, 2006) (Ref. 6) 

2. National Aeronautics Research and Development Plan, Biennial Update (National Science and 

Technology Council, 2010) (Ref. 7) 

3. Most Wanted Aviation Safety Improvements (National Transportation Safety Board, 2010) (Ref. 8) 

4. Safety Initiatives (Flight Safety Foundation, 2010) (Ref. 9) 

5. Joint Planning and Development Office (JPDO) Safety Working Group Safety Issues database, 2008 

(Ref. 10) 

6. Future Aviation Safety Team (FAST) Areas of Change, 2010. (Ref. 11) 

7. NextGen Implementation Plan (Federal Aviation Administration, 2009) (Ref. 12) 

8. Commercial Aviation Safety Team (CAST) Safety Enhancements, Joint Implementation 

Measurement Data Analysis Team (JIMDAT) Meetings, and Aviation Safety Information Analysis 

and Sharing (ASIAS) Directed Studies (Refs. 13, 14) 

The most critical future safety risk issues that were identified were those that were cited in several of 

these sources as an area of concern in terms of safety. 

Runway Safety 

Despite a significant reduction in catastrophic airport accidents during the past two decades, runway 

safety is still one of the most significant safety concerns in commercial aviation. Runway safety 

encompasses runway incursions, runway excursions, and runway confusion (i.e., takeoffs/landings on the 

wrong runway or taxiway). 

The number of runway and taxiway incursions remains unacceptably high despite recent efforts to 

minimize their occurrence. While a number of initiatives have been undertaken to mitigate the risks that 

are associated with runway incursions, the trend remains flat in specific countries, most notably the 

United States. According to the International Air Transport Association (IATA), the majority of 

incursions are related to communications issues, which suggests that the use of standard International 

Civil Aviation Organization (ICAO) phraseology and improved proficiency in the use of aviation English 

are key factors to reducing the incidence of these events. Further, workload and distractions on the flight 

deck during the preflight phase have been identified as contributing factors. Improvements in airport 

surface markings and lighting, along with more accurate charting of airport infrastructure, have been 

implemented at many locations. Nevertheless, runway incursions are expected to remain a critical safety 

risk in the future. The NTSB considers runway incursions one of its top three aviation safety issues, 

noting that "these incidents continue to occur with alarming, and increased, frequency" (Ref. 8). The 

NTSB has recommended implementing a safety system for ground movement that will ensure the safe 

movement of airplanes on the ground and provide immediate warnings of probable collisions/incursions 

directly to flight crews in the cockpit. The NTSB has also proposed that operators be required to install 

cockpit moving map displays or automatic systems that alert pilots when a takeoff is attempted on a 

taxiway or runway other than the one intended. 
15 

The Flight Safety Foundation (FSF) conducted a project entitled Runway Safety Initiative (RSI) to 

address the challenge of runway safety. The RSI team consisted of about 20 organizations from around 

the world, including operators, manufacturers, air navigation service providers, pilot groups, and various 

other industry associations. After reviewing all areas of runway safety, the RSI team primarily focused on 

reducing the risk of runway excursions because 97 percent of runway accidents were found to be caused 

by excursions (Ref. 9). A runway excursion occurs when an aircraft on the runway surface leaves the end 

or the side of the runway surface. Runway excursions can occur on takeoff or landing and can be one of 

two types of events: a veer-off, in which the aircraft departs the side of the runway, and an overrun, in 

which the aircraft departs the end of the runway. The runway-excursion risk-reduction strategies that have 

been developed by the RSI team emphasize developing stabilized approaches and reducing the risk of 

flight crews landing long and fast with a tailwind on a contaminated runway. 

Runway excursions are a continuing safety concern. The Joint Implementation Measurement Data 

Analysis Team (JIMDAT) of the Commercial Aviation Safety team studied worldwide fatal and hull-loss 

accident data over the period from 1987 to 2008 and found that runway excursions have exhibited an 

upward trend. The FSF also found that over the 14 years preceding this study, nearly 30 excursions have 

occurred per year for commercial aircraft (i.e., over 25 percent of all accidents). The study also noted that 

although the percentage of excursions that included fatalities was low, the sheer number of excursions 

still resulted in a high overall number of fatalities. Independent of the FSF effort, the International Air 

Transport Association’s Safety Group had identified runway excursions as a significant safety challenge 

to be addressed. For this reason, runways excursions have been identified as a future aviation safety risk 

area. 

An increased number of aircraft in the air transportation system not only increases the aircraft density 

in the air but also on the ground. To address this increase, research is needed to develop systems that 

improve pilot and controller awareness of airport surface conditions (e.g., aircraft locations, ground 

vehicle locations, runway occupancy, and pavement conditions), particularly in low-visibility situations. 

Improving the situational awareness of flight crews and ground controllers is critical to reducing incidents 

and accidents on the ground (Ref. 7).

Approach and Landing Accident Reduction 

Approach and landing accidents include any landing or takeoff that involves abnormal runway or 

landing surface contact. This safety risk area also includes unstabilized approaches, that is, approaches 

where airspeed, rate of descent, aircraft attitude, aircraft configuration, or power settings do not meet 

stabilized approach criteria at the prescribed approach point. Events such as hard/heavy landings, 

long/fast landings, off-center landings, crabbed landings, gear-up landings (unless caused by a 

system/component malfunction), nosewheel-first touchdowns, tail strikes, and wingtip/nacelle strikes are 

also included in this category. These accidents often are manifestations of deficiencies that begin in the 

approach phase or even earlier. 

Approach and landing accidents often involve high-energy approaches. The most significant threats 

during approach are fast approach airspeed, high ground speed (e.g., not appreciating wind effects), and a 

high and/or steep approach above the desired flight path. These conditions combine to create a high 

energy approach, and early control of energy can reduce these threats. A stabilized approach provides a 

basis for a good landing. It provides the crew with the optimum conditions to flare, land, and stop the 

aircraft. An approach must be stabilized by 1,000 ft in instrument meteorological conditions (IMC) and 

by 500 ft in visual meteorological conditions (VMC). 
16 

The Flight Safety Foundation Approach and Landing Accident Reduction task force cited several 

important contributing factors to approach and landing accidents (Ref. 9): 

x Inadequate flight crew interaction with automatic flight systems. 

x Incorrect or inadequate ATC communication and instruction to the flight crew. 

x Failure in crew resource management (i.e., crew coordination, cross-check, and backup). 

x Unstabilized approaches that involve incorrect management of aircraft energy condition (i.e., 

approaches conducted too low/slow or too high/fast). 

x Failure to recognize the need for and execute a missed approach. 

x Spatial disorientation and visual illusions (visual approaches at night typically present a greater risk). 

Avoiding errors in situation awareness and situation assessment are key to preventing approach and 

landing accidents. The situation should be assessed on the basis of several parameters, including airspeed, 

altitude, runway length, runway surface conditions, wind, and visibility. Important situation cues for 

landing are: 

x The actual approach path and airspeed of the aircraft in comparison with the ideal flight path and the 

target air speed. 

x The runway conditions, friction, and the required level of braking. 

x The landing distance available for the ambient conditions and the weight and configuration of the 

aircraft. 

x Tailwind. 

The general aviation community has also identified approach and landing accidents as a significant 

safety risk. The National Business Aviation Association (NBAA), which promotes the aviation interests 

of organizations that use general aviation aircraft for business purposes, has stated that for decades 

approach and landing accidents consistently have accounted for approximately 50 percent of U.S. 

business aviation accidents, with no evidence of recent improvement (Ref. 10).

Loss of Control – In Flight 

Loss of control in flight involves accidents that occur during airborne phases of flight where aircraft 

control was lost. Loss of control can occur during either IMC or VMC. Occurrences that involve 

configuring the aircraft (e.g., setting of flaps, slats, on-board systems, and so on) are also considered loss 

of control. Loss of control during flight may occur as a result of a stall, an icing-related event, a severe 

atmospheric turbulence or wake vortex encounter, or a system/component malfunction or failure. 

Aircraft stall leading to loss of control can have a number of contributing factors, including failure of 

the flight crew to follow the approach-to-stall procedures as a result of inadequate training; lack of flight 

crew preparation for the post-stall recovery task; failure of the stick-shaker system to provide an adequate 

time margin between activation and stall; overemphasis of test standards on minimum altitude loss, which 
17 

can lead to negative training transfer; lack of regulatory requirements for post-stall recognition and 

recovery training; and inappropriate use or reliance on automation to recover from unusual attitude or inflight situations (Ref. 10). 

Loss of stability and maneuverability can result from an upset condition due to inadvertent encounters 

with hazardous weather conditions such as severe turbulence, convective weather, or icing. Recent 

incidents have highlighted new potential contributors to such upset conditions, including high ice water 

content atmospheric conditions capable of causing ice accretion on vital aircraft sensors and inside jet 

engines, at temperatures colder and altitudes higher than icing was previously known to occur (Ref. 7). 

Accidents due to a loss of control may also occur as a result of a lack of attitude awareness (spatial 

disorientation) or a lack of energy-state awareness on the part of the flight crew. Loss of attitude 

awareness is typically characterized by an initial “mismatch” that develops between the actual airplane 

attitude and the attitude that is perceived by the pilot, followed by a failure to resolve the mismatch, 

leading to a loss of control. Loss of energy-state awareness is typically characterized by a failure to 

monitor or understand energy-state indications (e.g., airspeed, altitude, vertical speed, or commanded 

thrust) and a resultant failure to accurately forecast the ability to maintain safe flight. Both types of events 

typically involve the failure of the flight crew to maintain an awareness of critical flight deck indications. 

Icing/Ice Detection 

Adverse weather conditions, including storms and icing conditions, significantly reduce the capacity 

and reliability of the air transportation system. Adverse weather also degrades system safety. 

Accumulations of snow, ice, freezing rain, or frost on aircraft surfaces and sensors that occurs in flight or 

on the ground (i.e., deicing-related) can adversely affect aircraft control or performance. This issue is 

important to both civil and military aviation. It is also a critical issue for all types of aircraft and is 

particularly important for turboprop aircraft. Research is needed to improve the ability to predict and 

monitor environmental conditions and develop aerodynamic designs and techniques that are robust to 

adverse conditions. Techniques to predict and mitigate the impact of adverse environmental conditions on 

the aircraft operation, including validation of icing prediction capabilities, should be improved (Ref. 6). 

The joint government/industry Commercial Aviation Safety team has recommended that 

manufacturers of new turboprop type designs adapt and implement systems that automatically detect the 

presence of icing conditions that exceed those for which the aircraft has been certified; monitor, if 

feasible, the accretion rate for advisory purposes; and provide annunciation to the flight crew. For current 

turboprop production aircraft and existing type designs, manufacturers should be requested to conduct a 

study to determine the feasibility of installing systems that automatically detect the presence of icing 

conditions and alert the flight crew. These recommendations apply to all turboprop aircraft that are 

operated in commercial passenger and cargo revenue service that have non-evaporative ice protection 

systems and non-powered flight controls (Ref. 13). 

The consequences that result from operating an airplane in icing conditions without first having 

thoroughly demonstrated adequate handling and controllability characteristics for that airplane under 

adverse weather conditions are severe in most cases. This fact alone warrants a thorough certification test 

program, including the application of revised standards to airplanes that are currently certificated for 

flight in icing conditions. Specific NTSB recommendations for reducing the dangers to aircraft flying in 

icing conditions include using current research on freezing rain and large water droplets to revise the 

manner in which aircraft are designed and approved for flight in icing conditions, applying revised icing 
18 

requirements to currently certificated aircraft, and requiring that airplanes with pneumatic deice boots 

activate the boots as soon as the airplane enters icing conditions (Ref. 8). 

Super Density Operations 

Expected growth in the demand for air transportation will require more efficient, denser en route and 

terminal area operations. This necessitates procedures that reduce minimum spacing requirements during 

all phases of flight and in all weather conditions, through an integrated approach that leverages a suite of 

emerging technologies such as performance-based navigation and automatic dependent surveillance 

broadcast (ADS-B). Performance-based navigation procedures, such as required navigation performance 

(RNP), area navigation (RNAV), optimized profile descents, and tailored arrivals for oceanic flights, are 

being developed to increase the capacity and efficiency of the National Airspace System, as well as to 

provide environmental benefits in terms of reductions in fuel emissions and aircraft noise. The National 

Science and Technology Council state that “reduced aircraft separation will require a move to trajectorybased operations, performance-based navigation, and a new allocation of responsibilities between air and 

ground and between humans and automation. In addition, planned advanced airspace design concepts that 

can be dynamically adjusted to meet demand requirements and to avoid hazardous weather conditions 

must be developed with safety in mind.” 

Increasing capacity will depend not only upon reducing lateral and longitudinal separation standards 

for arrival and departure operations but on efficiently managing the movements of greater numbers of 

aircraft on airport surfaces as well. To accomplish this while maintaining or improving safety, procedures 

will be needed to efficiently accommodate a large number and wide range of aircraft types through 

spacing and sequencing based on aircraft type and equipment rather than a common worst-case standard. 

New concepts of operation should be evaluated in terms of their technological, business, and human 

factors issues as well as their impact on capacity, safety, and the environment. Furthermore, safe, highcapacity operations in a complex future airspace environment will require innovative ATM procedures, 

such as simultaneous non-interfering operations, in which general aviation and rotorcraft are threaded 

through airspace that is unused by commercial air traffic (Ref. 6). 

Air traffic control is currently a labor-intensive process. FAA controllers, aided by radar, weather 

displays, and procedures, maintain traffic flow and assure separation by communicating instructions to 

aircraft in their sector of responsibility. In many busy terminal areas, system limitations constrain the 

capacity of the air transportation system, resulting in congestion-related delays. Initiatives to reduce 

aircraft separation by automating time-critical separation-assurance tasks and providing automated 

advisories to air traffic controllers and flight crews are being investigated. However, changing the role of 

the controller from tactical separation to traffic flow management and trusting automated systems to 

manage the tactical separation of aircraft is a source of potential risk in the NAS that will require 

resolution of major human factors, safety, and institutional issues (Ref. 6). 

The expected growth in air transportation demand will likely require operators to perform a wider 

range of tasks and to collaborate more closely with one another and rely more heavily on modern 

technologies. For example, pilots may begin to play a more active role in traffic separation or spacing and 

will need to coordinate their activities and intentions with other pilots and controllers. With the 

introduction of technologies like ASAS (Airborne Separation Assistance Systems) and ADS-B 

(Automatic Dependent Surveillance), future flight crews may be faced with increased responsibility for 

separation assurance during all phases of flight (Ref. 11). The need to interact and exchange information 

and to distribute more information in a timely manner will become increasingly critical. In order to 

provide increased utilization of the airspace, separation standards may decrease between runways, 
19 

between aircraft, between landing operations, and for vertical separation. The risk of runway incursions 

may also increase as a result. The reliability of the technologies and procedures that enable reduced 

separation must be assured. In addition, research into candidate concepts of operations and enabling technologies is needed for any change in separation responsibility from ground controllers to the cockpit. 

Human Fatigue 

Fatigue is a crosscutting issue that does not map to one particular accident category; rather, it can be 

an important contributing factor in all types of aircraft accidents. Generally speaking, fatigue is weariness 

from physical and/or mental exertion, which can often result in the degradation of human performance. It 

includes both human factors and human fatigue issues in design, operations, air traffic management, and 

maintenance, repair, and overhaul. Human fatigue can lead to a loss of situational awareness on the part 

of pilots or controllers, which in turn can lead to a lack of perception and comprehension of elements in 

the surrounding environment and a lack of projection of their status in the near future. Fatigue can result 

from many factors, including inappropriate prioritization of tasks, channeling of attention, or 

inappropriate allocation of tasks between humans and automation. Fatigue also can include loss of 

awareness of automation status, systems, terrain, traffic, and surrounding environment. Commercial 

airline pilots have identified sleep deprivation, high workload, and circadian rhythm interruption as the 

main factors that contribute to fatigue. The risk of increased fatigue of flight crews in future flight 

operations may occur as a result of the longer flight duty times that are associated with ultra long-range 

flights with minimum crew or the heavier workload that can be experienced in regional operations (Ref. 

11). 

Operating a vehicle without the operator’s having adequate rest, in any mode of transportation, 

presents an unnecessary risk to the traveling public. The NTSB has long been concerned about the effects 

of fatigue on persons performing critical functions in all transportation industries. In the aviation industry, 

this includes flight crews, aviation mechanics, and air traffic controllers. Their recommendations on the 

issues of human fatigue and hours-of-work policies have had a substantial effect on encouraging the 

modal agencies to conduct research and take action toward understanding the complex problem of 

operator fatigue in transportation and its effect on performance. However, the issue of fatigue has 

remained on the NTSB’s list of most wanted safety improvements since 1990. To reduce the number of 

accidents and incidents that are caused by human fatigue in the aviation industry, the NTSB has 

recommended that the FAA issue regulations that establish scientifically based duty-time limitations for 

air carrier maintenance personnel and flight crews. For air traffic controllers, the NTSB recommendations 

include revising controller work-scheduling policies and practices to provide adequate rest periods, 

modifying controller shift rotations to minimize fatigue, and developing fatigue awareness and 

countermeasures training programs for controllers (Ref. 8). 

Recognizing that prior recommendations dealt primarily with flight- and duty-time regulations, the 

NTSB has recently recommended that the FAA oversee the implementation of a fatigue management 

system that would address the problems that are associated with fatigue in an operational environment 

and take a comprehensive, tailored approach to the problem of fatigue within the industry. A fatigue 

management system would encompass much more than just the establishment of guidelines or standards 

regarding duty, flight, and rest periods. As envisioned by the NTSB, a fatigue management system would 

incorporate various strategies to manage fatigue, such as scheduling practices, attendance policies, 

education, medical screening and treatment, rest environments, and commuting policies (Ref. 8). 
20 

Increasing Complexity and Reliance on Automation 

Automation, as a concept, is the allocation to machines of functions that otherwise would be allocated 

to humans. The term also is used to refer to the machines that perform these functions. Flight-deck 

automation, therefore, consists of machines on the commercial transport aircraft flight deck that perform 

functions that otherwise would need to be performed by pilots. Current flight-deck automation includes 

autopilot systems, flight-path management systems, electronic flight instrument systems, and warning and 

alerting systems. With the advent of advanced technology and the so-called "glass cockpit," as well as the 

transfer of safety-critical functions away from human control, pilots, scientists, and aviation safety experts 

have expressed concerns about the safety of flight-deck automation (Ref. 11). 

Commercial transport aircraft flight-deck automation has been well-received by pilots and the aviation 

industry as a whole. Accident rates for advanced technology aircraft are generally lower than those of 

comparable conventional aircraft. Nevertheless, pilots, scientists, and aviation safety experts have 

expressed some concerns about flight-deck automation, including fear that pilots may place too much 

confidence in automation, concern that pilots may lose manual flying skills, and concern that pilotautomation interfaces may be poorly designed (Ref. 11). Increasingly, aircraft systems are being designed 

to automatically reconfigure themselves in the event of system failures without notifying the crew of early 

trends that may indicate anomalous component performance. 

Increasing pressure to replace humans with automated systems may characterize future design 

philosophies. An increasing need exists to adequately design systems from the start to take advantage of 

human flexibility and creativity and to augment human abilities and limitations with automated systems. 

This has been (and is still) the focus of many activities (e.g., human-machine interface, cockpit design, 

autopilot, and Flight Management System certification criteria); methodologies are being developed by 

manufacturers with the participation of human-factors specialists. However, the likelihood exists that 

crews will unconsciously relinquish command responsibilities momentarily to automated systems. The 

unknown effects of aircraft/pilot coupling potentially could result in a perfectly normal flight suddenly 

taking on characteristics that the pilot has seldom or never encountered previously. 

The ever-increasing demand for air transportation, combined with the rapid pace of technological 

change, poses significant challenges for the effective integration of humans and automation. With the 

increasing reliance on and complexity of flight-deck automation, a better understanding of the causes of 

human error and of human contributions to safety is needed. In complex and highly automated aircraft, 

flight crews can lose situational awareness of the automation mode under which the aircraft is operating 

or may not understand the interaction between a mode of automation and a particular phase of flight or 

pilot input. Situations such as these can lead to the crew’s mismanagement of the energy state of the 

aircraft or to the deviation of the aircraft from the intended flight path for other reasons. Design guidelines 

should be developed that will help minimize the potential for design-induced error and facilitate positive 

human intervention in the event of system failure. The emphasis of air-carrier policies and procedures 

should be to help minimize the frequency with which flight crews induce automation errors and to help 

flight crews recognize and correct automation errors in a timely manner, regardless of the source of the 

error (Ref. 15).

Based on the National Research Council’s decadal survey of civil aeronautics (Ref. 6), research on 

human and machine integration technologies for vehicle applications should include the following: 
21 

x Development and testing of enabling technologies for pilot workload management and reduced crew 

operations (e.g., improved human and machine integration for a flight management system) that also 

maintain pilot awareness at the proper level. 

x Development of display concepts for maintaining operator situational awareness in the monitoring of 

highly automated processes. Demonstration of the ability of operators to rapidly and accurately 

intervene in the event of a system failure. 

x Development of technologies and display concepts that enable the effective fusion of information 

from multiple sources.

Aircraft Mixed Fleet Equipage 

Not all aircraft may have the same level of equipage in future “free flight” environments. This could 

lead to multiple modes of conflict resolution (e.g., air-to-air, air-to-ground) and to problems in maintaining 

situational awareness when significant gaps in knowledge exist regarding other aircraft (e.g., flight path 

intent information may be lacking, or even knowledge that other aircraft exist). Technologies and 

procedures to manage the mix of low- and advanced-technology aircraft within the airspace must be 

developed, or low-technology aircraft must be excluded from airspace that is used by advanced aircraft 

(Ref. 11). 

The operational capabilities of NextGen will provide air traffic controllers with improved tools to 

handle more complex traffic while improving service. Some of these capabilities will take advantage of 

existing avionics, such as RNAV and RNP, while others will require new avionics, such as ADS-B. The 

rate at which users equip for those capabilities that require new avionics will influence the magnitude and 

timeframe in which NextGen benefits are realized. 

While lesser equipped aircraft will still be accommodated in the NAS, ensuring that a significant 

portion of the aircraft fleet is appropriately equipped to take advantage of capacity, efficiency, and 

environmental improvements is a critical issue for NextGen. However, recognizing that all aircraft will 

not be similarly equipped adds complexity to the task of air traffic service providers and presents a future 

safety challenge for NextGen. The FAA has established a set of governing principles for an integrated 

avionics equipage strategy that is aimed at accelerating the NextGen operational capabilities in the midterm time frame (i.e., 20122018). These include (1) targeting equipage and associated capabilities to 

maximize operational benefits for the specific locations or airspace that require a higher performance 

level in order to elevate system performance and to satisfy demand and (2) providing a “best-equipped, 

best-served” priority in the NAS to early adopters of advanced avionics (Ref. 12). 

Inadequate Protection, Analysis, and Dissemination of Safety Data 

Through the collection, analysis, and dissemination of relevant data, decision makers throughout 

industry, air navigation service providers (ANSPs), and regulatory authorities will be able to proactively 

implement changes that have a positive effect on safety. Nonetheless, these organizations have 

historically collected a significant amount of data without having established common taxonomies or 

appropriate governance to facilitate the sharing of valuable safety data. Consequently, the industry as a 

whole is data rich and information poor. The IATA has been working with key airlines, ANSPs, and 

airport and regulatory authorities to create a global data-collection process to provide the ability to 

accurately measure and benchmark safety occurrences and, as a result, create effective mitigation 

strategies that are appropriate for airlines operating in specific regions. 
22 

Safety data provide the basis for discovering vulnerabilities in the air transportation system. The 

following issues must be addressed for future safety benefits to be attained by preventing potential 

vulnerabilities from becoming accidents (Ref. 10): 

x Inadequate dissemination of flight-critical information within the organization. 

x Failure to share significant data between airlines/operators. 

x Failure to disseminate critical information between manufacturers. 

x Lack of formalized, threat-free information reporting from operators to manufacturers. 

x Insufficient analysis of incidents. 

x Failure of regulators to disseminate critical flight safety information to flight crews. 

x Timely flight safety information not shared between validating authority and certificating authority. 

x Failure of the airline/operator and ATC processes to identify and stress the criticality of self-reporting 

of incidents and safety issues by operational personnel. 

x Assurance to operational personnel that the data they provide will be protected and not used for 

punitive action. 

The current air transportation system has reached a state in which low accident levels for commercial 

aviation, coupled with the traditional forensic investigation approach to aviation safety, are yielding fewer 

insights that significantly improve aviation safety (Ref. 7). Thus, traditional methods of historical or 

forensic review of accident data cannot be relied upon as the sole predictor of risk and future events. As 

the number of accidents and serious incidents decrease as a result of better design, better hazard 

elimination, and better risk mitigation, more attention will be needed on the identification of subtle 

system-level issues and anomalies in order to predict future safety issues before they lead to serious 

accidents or incidents. Advances in prognostic techniques enable insights into system safety through the 

examination of large numbers of normal operations as well as incident events. 

In the National Aeronautics Research and Development Plan, the National Science and Technology 

Council offers two data-analysis recommendations that are aimed at reducing accidents and incidents. 

These involve the identification of system-wide safety risks through the examination of prognostic 

methodologies that are capable of organizing, managing, and mining data from all users in the entire 

airspace system. The first recommendation is to develop advanced methods to automatically analyze 

textual safety reports and extract system performance information for prognostic identification of safety 

risks for system operators and designers. Secondly, fundamentally new data-mining algorithms should be 

developed to support automated data-analysis tools to integrate information from a diverse array of data 

resources (i.e., numeric and textual) to enable rapid prognostic identification of system-wide safety risks. 

These research objectives will organize and manage data from all users in the entire airspace system and 

mine those data to actively identify safety risks to the affected users, rigorously integrating both objective 

statistical techniques and operator reports of safety concerns. 

Proactive safety management and integrated safety cases allow the early identification of problems and 

the analysis of trends so that preventive measures are put in place before any accidents can occur. The 
23 

FAA’s ASIAS program provides a suite of tools that extract relevant knowledge from multiple, disparate 

sources of safety information. The ASIAS program also helps the FAA and industry in monitoring the 

effectiveness of safety enhancements (Ref. 14). The ASIAS team has suggested that as aircraft become 

more complex, a need exists for standard logical frame layouts in aircraft data. Further, the need exists for 

global sharing of data and for standardization of data collection and common taxonomies for textual data. 

Finally, improving the quality and dissemination/sharing of regional jet, rotorcraft, and general aviation 

data and safety information is needed. 

Enhanced Survivability in the Event of an Accident 

Enhancing and protecting the safety of passengers, crews, and ground personnel in the event of an 

accident is a key research challenge to improving aviation safety. The research can be broken into two 

categories: (1) improving crash survivability of aircraft structures and (2) improving evacuation and 

accident response procedures. At present, nearly half of the aircraft fatalities in impact-survivable 

accidents are due to the effects of smoke and fire (Ref. 7). Research into understanding and reducing 

flammability of aircraft interiors is essential to making impact accidents survivable for crew and 

passengers, and firefighters as well. Post-impact fire and evacuation were two safety concerns that were 

expressed by several organizations that provided input to the JPDO Safety Working Group Safety Issues 

Database (Ref. 10). Accidents and incidents that were related to emergency evacuation were defined as 

those occurrences for which person(s) were injured during the evacuation, an unnecessary evacuation was 

performed, evacuation equipment failed to perform as required, or the evacuation was a factor in the 

outcome. 

While significant progress has been made to mitigate the catastrophic effects of post-impact fires and 

structural damage to the aircraft, this remains an issue of concern for aviation safety. With the introduction 

of alternative fuel technologies and advanced composite and metallic materials, enhancing post-accident 

survivability will continue to be a safety risk area. Future aircraft will be made from advanced, novel 

materials in more complex configurations, with more technically advanced subsystems and avionics. When 

accidents do occur, the probability of survival for the passengers and crew on board must be as high as 

possible. Research into understanding the flammability of alternative fuels and smoke toxicity of advanced 

aircraft materials is needed. Restraint systems that are integrated into and as strong as the supporting 

aircraft structure offer the possibility of providing increased occupant survivability; further research into 

these systems is essential. Lastly, examination of current and future evacuation procedures and accidentresponse procedures will ensure that new aircraft are as safe as or safer than the aircraft of today (Ref. 7). 
24 

4. Top-Down Systems Analysis 

An established, peer-reviewed systems-analysis methodology was used to conduct a detailed, topdown (goal-oriented) analysis of the NASA AvSafe program. This section contains a description of the 

study methodology, the top-level goals and objectives for the NASA AvSafe program, the assessment 

criteria, and a discussion of the impact of the current AvSafe portfolio based on these criteria. 

4.1 Top-Down Systems Analysis Methodology 

The overall goal of this study was to develop a set of challenging safety issues that NASA potentially 

could address in its aviation safety research portfolio. The systems analysis methodology that was 

developed by John Gibson (Ref. 16) was selected as the basis for this study because it is a top-down, 

goal-oriented approach to systems analysis that also contains elements of sociotechnical systems (Ref. 17) 

concepts. The methodology that was used for the analysis of the NASA AvSafe program is summarized 

in Fig. 5. 

Figure 5. Methodology used for top-down analysis of NASA AvSafe program. 
25 

Data that were used in the study were collected from three sources: (1) aviation statistical databases, 

(2) subject-matter experts, and (3) literature review. The aviation statistical databases that were used in 

the study, as described in section 2, include those from the NTSB and the FAA. Input was obtained from 

various subject-matter experts, both internal (i.e., NASA researchers and management) and external to the 

agency. An exhaustive search of published literature, presentations, government and business plans, and 

other aviation-safety-related documents also was conducted. A complete listing of the documents that 

were reviewed in the study is given in the reference section. The results from the aviation statistical data 

analysis (given in section 2) were used to develop a set of current safety risks or “tall poles” for each of 

the three types of operations that were analyzed (i.e., FAR Parts 121, 135, and 91). Similarly, the 

qualitative safety risk identification (discussed in section 3) identified those issues that are likely to 

continue to pose a safety risk in the future. 

The step entitled “Identify Top Level Goal”, which is identical to the “Generalize the question” from 

Gibson’s goal development process, was used to identify the top-level goal for the NASA AvSafe 

program (see Fig. 5). The information that was obtained from the data collection and the risk 

identification processes was used to gain a clear understanding of the current aviation safety problem 

(“Descriptive Scenario”), determine some of the ideal safety issues in the future NAS (“Normative 

Scenario”), and identify values that are important to NASA and the stakeholders in the NAS 

(“Axiological Component”). In addition, an “Objectives Tree” was developed to graphically display the 

relationship between the top-level goal and other high-level goals and objectives. 

Based on all of this information, a high-level set of assessment criteria was generated, along with a list 

of research alternatives. Because of the time constraints on this study, the assessment criteria were used to 

evaluate only the current AvSafe research portfolio. This same set of criteria is recommended for use to 

assess any of the possible research alternatives that are not in the current portfolio. 

Although not explicitly shown in figure 5, the “Iteration” and “Validation” steps for the goaldevelopment process and the overall systems methodology were also conducted in this study. 

4.2 NASA AvSafe Program Goal and Objectives 

NASA AvSafe Research 

To begin the process of determining the top-level goal of the NASA AvSafe program, a review of 

publicly stated goals and objectives yielded the following results: 

x “To improve the safety of current and future aircraft operating in the NAS” (Ref. 2). 

x “To identify and develop tools, methods, and technologies for improving overall aircraft safety of 

new and legacy vehicles operating in the Next Generation Air Transportation System” (Refs. 2, 18). 

 “The AvSafe program will take a proactive approach to safety challenges with new and current 

vehicles and with operations in the nation's current and future air transportation system. In addition, 

the program will continue the effort to examine key challenges in verifying and validating flight 

critical systems” (Ref. 19). 

x “The aeronautics research portfolio is closely aligned with this national plan (for aeronautics R&D) 

and includes research content as the key areas called outreach plan [sic] of mobility, energy and 

environment, safety and national security” (Ref. 19). 
26 

Secondly, the following U.S. government aviation safety research plans were examined for their 

relevance to NASA’s AvSafe goals: 

x National Aeronautics Research and Development Plan (Ref. 7) 

x JPDO National Aviation Safety Strategic Plan (NASSP) (Ref. 20) 

x FAA Aviation Safety Fiscal Year 2010 Business Plan (Ref. 21) 

x FAA 2009 National Aviation Research Plan (Ref. 22) 

Finally, the aviation safety research plans or stated needs for the following agencies and organizations 

were reviewed to obtain information about planned or ideal future goals and research activities: 

x The Boeing Company 

x European Aviation Safety Agency (EASA) 

x EUROCONTROL 

x International Helicopter Safety Team 

x U.S. universities 

Following discussions with the current AvSafe program management staff, the top-level goal for 

AvSafe is defined as: 

To proactively identify and develop tools, methods, and t echnologies for improving 

overall aircraft safety of new and legacy vehicles operating in the Next Generation Air 

Transportation System. 

Both the NASA Strategic Plan and the NASA FY2011 Budget Request both imply that the goals of 

the AvSafe program should support, respectively, the Next Generation Air Transportation System and the 

National Plan for Aeronautics Research & Development. Therefore, the top-level AvSafe goal and the 

goals and objectives set forth in these two plans are connected in the high-level objectives tree (Fig. 6). 

Note that three of the NASSP objectives were not included in the objectives tree because they are not 

within the current charter of the NASA AvSafe program. The three objectives that were omitted are: 

x Objective 1A: Provide consistent safety management approaches that are implemented throughout 

government and industry. 

x Objective 3A: Encourage development and implementation of safer practices and safer systems 

worldwide. 

x Objective 3B: Establish equivalent levels of safety across air transportation system boundaries. 
27 

Figure 6. NASA AvSafe program objectives tree. 

4.3 Portfolio Assessment Criteria 

The set of assessment criteria is a means for evaluating the goals and objectives that were outlined for 

the AvSafe program and summarized in the previous section. The criteria are not performance indicators 

for the system. Performance indicators (Ref. 23, pp. 191193) should be developed at the start of the 

proposed projects by principal investigators and other key research leads. The current AvSafe portfolio is 

evaluated by using a rating system that is a combination of the definitions that were used in the 2008 

evaluation of NASA aeronautics research by the National Research Council (Ref. 24) and the interaction 

matrix concept (Ref. 16). Also, for the assessments that were conducted with these ratings, the 

technologies were assumed to be fully realized. The rating system is as follows: 
28 

D Direct impact 

I Indirect impact 

 Very little or no impact 

x Direct impact: NASA technology will directly impact the potential either for reducing the 

likelihood of a future occurrence of this accident category or risk area or for achieving a technical 

goal. This technology will significantly advance the state of the art. 

x Indirect impact: NASA technology will indirectly impact the potential either for reducing the 

likelihood of a future occurrence of this accident category or risk area or for achieving a technical 

goal. The research described, if successful, would make only moderate advances in the state of the 

art of relevant technologies, although the results would still be substantial. 

x Very little or no impact: NASA technology will have very little or no impact on reducing the 

likelihood of a future occurrence of this accident category or risk area or in achieving this technical 

goal. 

The criteria that will be used to evaluate the current NASA AvSafe program portfolio are as follows: 

x Expected impact on historic Part 121 “tall poles” 

x Expected impact on historic Part 135 “tall poles” 

x Expected impact on historic Part 91 “tall poles” 

x Expected impact on future safety risk “tall poles” 

x Expected impact on JPDO NextGen “NASA-related” safety objectives 

x Expected impact on National Aeronautics R&D Plan safety-related goals 

The rationale for using this set of criteria is to evaluate the impact that the current NASA AvSafe 

portfolio will have on current safety risks (i.e., historic tall poles), future safety risks (i.e., future safety 

risk tall poles) and NASA’s high-level goals and objectives (i.e., both from National aeronautics R&D 

programs and the JPDO safety objectives). 

Other criteria were considered but could not be used in this assessment as a result of the three-month 

time constraint for the study. For example, given the current limitations in the U.S. budget, one suggested 

criterion was the “uniqueness” of the research. Three suggested ratings for this criterion were: (1) totally 

unique to NASA (i.e., only one U.S. researcher), (2) collaboration with the FAA or other U.S. agency, 

and (3) duplication of other U.S. research without collaboration. Another suggested criterion that 

addresses the axiological component was the “correlation of the research activities to the NASA skill set.” 

Finally, given that the assessments that were conducted in this study did not account for impediments to 

successful completion of these research activities, the following additional criteria were also 

recommended for future assessments of the NASA AvSafe Research portfolio (Refs. 23, 25): 
29 

x Technology readiness level (TRL) 

x Technical development risk (TDR) 

x Implementation risk (IR) 

x Cost 

x Expected implementation cost 

x Programmatic cost 

Note that some categories of aviation accidents can continue long after mitigating technologies have 

been developed due to slow adaptation rates. For example, one researcher suggested that we not invest in 

research that addresses problems that have essentially been solved (e.g., CFIT) with modern equipage. 

Thus, if historic tall poles are used for portfolio evaluation, these criteria should only be used in 

combination with other criteria with a more future-oriented vision. Conversely, however, a totally 

forward-looking vision may overlook some long-established trends that continue to pose a safety risk. 

4.4 Assessment of Current Portfolio 

The AvSafe program research portfolio in January 2010 (Ref. 2) consisted of the following four 

projects: 

x Integrated Vehicle Health Management (IVHM) 

x Integrated Intelligent Flight Deck (IIFD) 

x Integrated Resilient Aircraft Control (IRAC) 

x Aircraft Aging and Durability (AAD) 

Information that was used to assess these projects was obtained from several sources, including 

projects plans (Ref. 2), conference documents, internal presentations and white papers, informal 

discussions with NASA internal personnel, and prior knowledge of systems analysis team members. In 

the justification for each rating, a reference for a specific project milestone or subtopic (IIFD and IVHM), 

challenge problem (AAD), or technology number (IRAC) was provided. A list of technologies for the 

IRAC portfolio was previously developed for use in an FY2010 milestone by several of the authors of this 

document prior to the beginning of this study. This technology list also was used in this study in the 

evaluation of the IRAC portfolio and is included in Appendix D. 

4.4.1 Expected Impact of Current Portfolio on Historic Part 121 Tall Poles 

Table 5 contains a mapping of expected impact of the current AvSafe portfolio on the historic Part 121 

tall poles. 
30 

Table 5. Impact of Current AvSafe Portfolio on Part 121 Tall Poles 

Part 121 tall pole 

Aviation safety project 

IIFD IRAC IVHM AAD 

Abrupt maneuver D I 

Fire – post impact 

Loss of control – in flight I 

D 

I 

I 

System/component failure/malfunction – 

powerplant D D D 

System/component failure/malfunction – 

nonpowerplant I D 

I 

D 

Turbulence encounter I I 

Abrupt Maneuver (AMAN) 

 This category is defined as the intentional abrupt maneuvering of the aircraft by the flight crew to 

avoid a collision with terrain, objects/obstacles, weather, or other aircraft (Ref. 4). Two research subtopics 

(SS.1 and SS.2) for the IIFD project address this CICTT occurrence category and, thus, will have a direct 

impact. Within the IRAC project portfolio, proposed research in maneuvering envelope identification 

algorithms (IRAC-2), aerodynamic modeling of off-nominal flight conditions (IRAC-4), and flight 

dynamic models of unsteady aerodynamics (IRAC-5) were classified as having an indirect impact. 

Fire – Post Impact (F-POST) 

 This category is defined as “fire/smoke resulting from impact” (Ref. 4). None of the research areas in 

the current AvSafe portfolio address this occurrence category. 

Loss of Control – In Flight (LOC-I) 

 This category is defined as loss of aircraft control or a deviation from the intended flight path in flight 

(Ref. 4). Note that in the CICTT definition of this category, if the loss of control is the direct result of a 

system/component failure or malfunction, then the event is classified solely as a system/component 

failure/malfunction rather than as a loss-of-control event. Given this restrictive definition of loss of 

control, the only research areas that were determined to have a direct impact on this occurrence category 

were within the IRAC portfolio; these include development of adaptive control algorithms (IRAC-1), 

development of maneuvering envelope identification algorithms (IRAC-2), development of emergency 

trajectory and flight-planning guidance algorithms (IRAC-3), aerodynamic modeling of off-nominal flight 

conditions (IRAC-4), flight dynamic modeling of unsteady aerodynamics (IRAC-5), and modeling of 
31 

real-time full-envelope flight dynamics (IRAC-7). The remaining research within the IRAC portfolio (i.e., 

initiatives related to icing (IRAC 6 and 9) or to enabling technologies (IRAC 8 and 10)) was classified as 

having an indirect impact on this occurrence category. Hazard detection research within the IIFD project 

(e.g., forward-looking interferometric sensing) and the IVHM project (milestones 1.1.1.9 and 2.2.1.1) 

were also classified as having an indirect impact on the occurrence category. Note that loss of control due 

to icing is categorized under “Icing.” 

System Component Failure or Malfunction – Powerplant (SCF-PP) 

 This category is defined as the failure or malfunction of an aircraft system or component that is related 

to the powerplant (Ref. 4). This category includes failures or malfunctions that are maintenance related 

but excludes problems that are attributed to carburetor and induction icing or fuel problems (e.g., fuel 

starvation, fuel exhaustion, or fuel contamination); thus, IRAC icing research (IRAC-9) is not applicable 

to this category. All of the research in the AvSafe portfolio that does address this occurrence category 

would have a direct impact on these types of events. These specific AvSafe research areas include IRAC 

technology 10 (engine performance, usage, and prognostic modeling), the IVHMPropulsion Health 

Management element, and AAD challenge problems 5, 6, and 7. 

System Component Failure or Malfunction – Non-Powerplant (SCF-NP) 

 This category is defined as the failure or malfunction of an aircraft system or component other than the 

powerplant (Ref. 4). The proposed research in IVHM element 2.1 (aircraft systems) and in AAD 

challenge problem 8 (wiring degradation and faults) directly impacts this occurrence category. The faulttolerant system modeling research within the IIFD project (IM.3) and the AAD challenge problems 

(problems 1, 2, and 4) also impact this category, but the impact is expected to be indirect. Note that the 

airframe structural failure research within both the AAD and the IVHM projects (element 2.2: Airframe 

Health Management) and the verification and validation research of flight critical systems that is currently 

being conducted within both the IVHM project (element 2.4: Software Health Management) and the 

IRAC project were determined to have little no impact on this category because these types of 

malfunctions were not in the data set that was examined.

Turbulence Encounter (TURB) 

 Any in-flight encounters with turbulence, including clear air, mountain waves, and wake vortices are 

included in this category (Ref. 4). The research within the IIFD project that involves the detection of 

various external hazards, including turbulence (IIFD milestones SS.1–SS.3) and the IRAC project 

research that addresses recovery from encounters with turbulence (IRAC-2, -4, -5, and -7) will have an 

indirect impact on this occurrence category. 

4.4.2 Expected Impact of Current Portfolio on Historic Part 135 Tall Poles 

Table 6 contains a mapping of expected impact of the current AvSafe portfolio on the historic Part 135 

tall poles. 
32 

Table 6. Impact of Current AvSafe Portfolio on Part 135 Tall Poles 

Part 135 tall pole 

Aviation safety project 

IIFD IRAC IVHM AAD 

Abnormal runway contact I I 

Bird strike 

Controlled flight into terrain I I 

Fire – post impact 

Icing 

I 

D D 

D 

Loss of control – in flight I 

D 

I 

I 

Runway excursion I 

SCF – powerplant D D I 

SCF – nonpowerplant I D 

I 

D 

Abnormal Runway Contact (ARC) 

This category is defined as any landing or takeoff that involves abnormal runway or landing-surface 

contact (Ref. 4). Specific types of events that are included in this category include tail strikes, hard/heavy 

landings, and gear-up landings. The research in the AvSafe portfolio that will have an indirect impact on 

this occurrence category includes emergency trajectory and flight-planning guidance algorithms (IRAC3), aerodynamic modeling of off-nominal flight conditions (IRAC-4), and remote sensing and imageprocessing research (IIFD milestones SS.1–SS.2). 

Bird Strike (BIRD) 

This recently added category includes occurrences that involve collisions or near collisions with birds 

and other types of wildlife during any phase of flight. None of the research areas in the current AvSafe 

portfolio address this occurrence category. 
33 

Controlled Flight Into Terrain (CFIT) 

Controlled flight into terrain is defined as an in-flight collision or near collision with terrain, water, or 

obstacle without the indication of loss of control (Ref. 4). IIFD project research in external hazard 

characterization (IIFD SS. 3.1) and multimodal interface technologies (IIFD MM.1–MM.3), in addition to 

IRAC project research regarding emergency trajectory and flight-planning guidance algorithms (IRAC-3), 

will have an indirect impact on this occurrence category. 

Fire – Post Impact (F-POST) 

As previously mentioned under Part 121, none of the research areas in the current AvSafe portfolio 

address this occurrence category. 

Icing (ICE) 

Icing is defined as the accumulation of snow, ice, freezing rain, or frost on aircraft surfaces that 

adversely affects aircraft control or performance (Ref. 4). This category includes events such as 

windshield icing that restricts visibility and ice accumulations on antennae and other external surfaces; 

however, carburetor and induction icing events are excluded from this category and are coded in the 

category for fuel-related issues. AvSafe research initiatives that directly impact this occurrence category 

are as follows: remote sensing and characterization of icing (IIFD SS.4), modeling of airframe and engine 

icing (IRAC-6 and IRAC-9), ice crystal sensing in high-density icing environments (IVHM milestone 

1.1.1.2) and developing a real-time iced aerodynamic degradation detection system for flight envelope 

protection (IVHM milestone 1.1.1.13). Because the research within the IIFD project (SS.1–SS.3) is 

expected to detect some icing-related hazards (e.g., icy runways and in-flight icing conditions), this 

portion of the IIFD portfolio will indirectly impact this occurrence category. 

Loss of Control – In Flight (LOC-I) 

The research in the AvSafe portfolio that is applicable to this occurrence category under Part 135 is 

identical to the previously mentioned activities for this category under Part 121, except for the deletion of 

the IVHM research that is related to milestone 2.2.1.1 (i.e., the development of technologies for the 

detection of possible damage to or degradation of airframe structural components).

Runway Excursion (RE) 

A runway excursion is defined as “a veer off of or an overrun of the runway surface.” This category is 

only applicable for events that occur during takeoff or landing. The IIFD project milestones for sensing, 

signal processing, and hazard characterization (IIFD SS.1–SS.3) will have an indirect impact on this 

category. 

System Component Failure or Malfunction – Powerplant (SCF-PP) 

The results for Part 135 are identical to the results that were previously described for this occurrence 

category under Part 121, except that the research that is being conducted for AAD challenge problems 5, 

6, and 7 will have an indirect rather than a direct impact on this occurrence category. 
34 

System Component Failure or Malfunction – Nonpowerplant (SCF-NP) 

Results for Part 135 are identical to the results that were previously described for this occurrence 

category under Part 121. 

4.4.3 Expected Impact of Current Portfolio on Historic Part 91 Tall Poles 

Table 7 contains a mapping of expected impact of the current AvSafe portfolio on the historic Part 91 

tall poles. 

Table 7. Impact of Current AvSafe Portfolio on Part 91 Tall Poles 

Part 91 tall pole 

Aviation safety project 

IIFD IRAC IVHM AAD 

Abnormal runway contact I I 

Controlled flight into terrain I I 

Collision with object – takeoff or landing I 

Fire – post impact 

Low-altitude operations I 

Loss of control - in flight I I I 

Loss of control – on ground I 

Power loss - fuel 

Runway excursion I 

SCF – powerplant D I 

SCF – nonpowerplant I D I 
35 

Abnormal Runway Contact (ARC) 

The research activities in the AvSafe portfolio that are applicable to this occurrence category for Part 

91 are identical to the activities that are applicable to Part 135 for the same category, with the exception 

of IRAC-4 (aerodynamic modeling of off-nominal flight conditions). As defined in the current IRAC 

portfolio, the research activities for IRAC-4 involve transport aircraft only. 

Controlled Flight into Terrain (CFIT) 

 The results for Part 91 are identical to the results that are previously described for this occurrence 

category under Part 135. 

Collision with Object(s) – Takeoff or Landing (CTOL) 

 The CICCTT defines this category as a collision with obstacle(s), during takeoff or landing, while 

airborne. The IIFD project includes research that examines hazards in the terminal area (IIFD SS.3.1) 

which will have an indirect impact on this occurrence category. 

Fire – Post Impact (F-POST) 

 As previously mentioned under Part 121, none of the research areas in the current AvSafe portfolio 

address this occurrence category. 

Low-Altitude Operations (LALT) 

 This category is defined as a collision or near collision with obstacles/objects/ terrain while 

intentionally operating near the surface, excluding takeoff and landing phases. The types of low-altitude 

operations that are included in the category are aerobatics, search-and-rescue operations, demonstration 

flights, and sightseeing. The multimodal interface research within the IIFD program (IIFD subtopics 

MM.1–MM.3) will have an indirect impact on this occurrence category. 

Loss of Control – In Flight (LOC-I) 

Several research areas in the AvSafe portfolio have a direct impact on in-flight loss of control. 

However, for Part 91 operations, all of the AvSafe research that is applicable to this occurrence category 

will have only an indirect impact. These specific research areas include the development of adaptive 

control algorithms (IRAC-1), the development of maneuvering-envelope identification algorithms (IRAC2), the development of emergency trajectory and flight-planning guidance algorithms (IRAC-3), flightdynamic modeling of unsteady aerodynamics (IRAC-5), hazard detection research within IIFD (e.g., the 

development of forward-looking interferometric sensing), and the development of lightning-strike sensors 

for avionics on composite-based aircraft (IVHM milestone 1.1.1.9). 

Loss of Control – Ground (LOC-G) This occurrence category is defined as the loss of aircraft control 

while the aircraft is on the ground. The loss of control can result from contamination on the runway or 

taxiway, including rain, snow, or slush. The IIFD remote-sensing and image-processing research (IIFD 

subtopics SS.1–SS.2) will have an indirect impact on this occurrence category. 

Power Loss – Fuel (FUEL) 
36 

 Events in this category are defined as having one or more powerplants with reduced or no power 

output due to fuel exhaustion, fuel starvation/mismanagement, fuel contamination/wrong fuel, or 

carburetor and/or induction icing.” None of the research in the current AvSafe portfolio will have any 

impact on this category. 

Runway Excursion (RE) 

 The results for Part 91 are identical to the results that were previously described for this occurrence 

category under Part 135. 

System Component Failure or Malfunction – Powerplant (SCF-PP) 

The research within the Propulsion Health Management element of the IVHM project will have a 

direct impact on this occurrence category for Part 91 operations. In addition, AAD research for challenge 

problem 6 (durability of engine superalloy disks) will have an indirect impact on this occurrence category. 

System Component Failure – Nonpowerplant (SCF-NP) The results for Part 91 are identical to the 

results that were previously described for this occurrence category under Part 135. 

4.4.4 Expected Impact of Current Portfolio on Future Safety Risk Tall Poles 

Table 9 contains a mapping of expected impact of the current AvSafe portfolio on the future safety 

risk tall poles. 

Table 8. Impact of Current AvSafe Portfolio on Future Safety Risk Tall Poles 

Future safety risk tall pole 

Aviation safety project 

IIFD IRAC IVHM AAD 

Runway safety D 

Approach and landing accident reduction D D 

Icing/ice detection 

D 

D D 

I 

Loss of control – in flight I 

D 

D 

I 

I D 

Super density operations D 

Human fatigue I 

Increasing complexity and reliance on automation D D D 
37 

Aircraft mixed fleet equipage 

Inadequate protection, analysis, and dissemination 

of safety data D D 

Enhanced survivability in the event of an accident 

Runway Safety 

Runway safety, as previously defined in section 3, contains three components: runway excursions, 

runway incursions, and runway confusion. A large portion of the entire IIFD research portfolio (e.g., 

hazard detection and characterization, and so on) will have a direct impact on this area of future risk. 

Approach and Landing Accident Reduction 

According to the Flight Safety Foundation, the key to preventing these types of accidents is to avoid 

errors in situation awareness and situation assessment. Various research activities (e.g., robust 

automation-human systems, multimodal interfaces, and so on) within the IIFD portfolio will have a direct 

impact on preventing these types of errors. Additionally, three current IRAC technologies also will have a 

direct impact: maneuvering-envelope identification algorithms (IRAC-2), emergency trajectory and 

flight-planning guidance algorithms (IRAC-3), and flight dynamic models of unsteady aerodynamics 

(IRAC-5). 

Icing/Ice Detection 

Icing and ice detection is an area of future risk that was identified by several groups, including the 

National Research Council, the Commercial Aviation Safety Team, and the National Transportation 

Safety Board. The types of research that are needed to address this future safety risk are the same as those 

that address historic icing issues; thus, the results for this future risk are identical to those that were 

identified for the Part 135 Icing category. 

Loss of Control – In Flight 

As opposed to the CICTT definition of loss of control, the definition of loss of control in terms of 

future risk also encompasses the causes of these types of accidents, such as severe atmospheric turbulence 

and system/component malfunctions and failures. Therefore, the AvSafe research that will impact this 

area as a future risk is identical to the assessment results that were identified under Part 121 for Loss of 

Control – In Flight, with some minor modifications. The research in the IVHM portfolio will now have a 

direct impact on this risk category due to the large amount of system-component-failure research in the 

portfolio (e.g., health management, validation and verification of software, and so on). Similarly, because 

the AAD research portfolio also addresses system component failures, especially those that may occur as 

a result of the use of composite materials, all of the challenge problem areas (except challenge problem 1) 

will have a direct impact on this future risk area. The research in AAD challenge problem 1 (i.e., damage 

methodology for metallic airframe structures) will have only an indirect impact because it is not expected 

to significantly advance the state of the art in loss-of-control or system/component failure research. 
38 

Super-Density Operations 

The future, as envisioned by the JPDO when the Next Generation Air Transportation System is 

implemented, is one in which more aircraft can safely travel closer together than in today’s NAS. 

Technologies that address separation assurance and coordination of information between pilots and 

controllers will be critical in this future environment. Several subtopics (SS.1–SS.3) and milestones in the 

IIFD portfolio will directly impact this area of future risk. 

Human Fatigue 

Fatigue is an issue that impacts not only flight crews operating in the future NAS, but air traffic 

controllers and maintenance personnel as well. This risk area is closely aligned with both “super-density 

operations” and “increasing complexity and reliance on automation,” but has been identified as a specific 

future safety concern by both the NTSB and the FAST. Many of the proposed solutions to this safety risk 

area are regulatory in nature and, therefore, under the charter of the FAA. However, research in the IIFD 

portfolio that examines the impact of fatigue on operator performance (IIFD milestone OC 3.4) will have 

an indirect impact on this area of future risk. 

Increasing Complexity and Reliance on Automation 

With the expected increased usage of more complex and automated technologies, concerns exist 

regarding future safety risks due to issues such as pilot and air traffic controller information overload and 

the potential failure of automated systems. IIFD research in the appropriate use of automation in the 

cockpit (milestone IIFD OP.2), along with IRAC/IVHM research in verification and validation of flight 

critical systems, will have a direct impact on these issues. 

Aircraft Mixed-Fleet Equipage 

The ability to safely move more aircraft in the NextGen Air Transportation System is contingent upon 

the use of more advanced equipment such as ADS-B, but not all aircraft will acquire these new 

technologies at the same time. Research that addresses this future safety risk is not in the current AvSafe 

portfolio. 

Inadequate Protection, Analysis, and Dissemination of Safety Data 

Global collection and sharing of data among stakeholders (i.e., operators, manufacturers, and 

regulators), data-mining algorithms to support automated data analysis, and prognostic identification of 

safety risks are some of the issues that fall within this area of future risk. The data-mining research in 

IVHM (i.e., research area 1.3: data mining and complex systems) and the IIFD predictive human 

performance modeling (milestone IIFD.IM.2) will have a direct impact on this future risk area. 

Enhanced Survivability in the Event of an Accident 

The goal of this future risk area is to reduce the likelihood of fatalities and serious injuries in the event 

of aviation accident. Specific research issues include reducing the possibility of post-impact fire/smoke, 

improving crash survivability of aircraft structures, and improving evacuation and accident response 

procedures. This area of future risk is not currently addressed in the current AvSafe research portfolio. 
39 

4.4.5 Expected Impact of Current Portfolio on NextGen NASA-Related Safety Objectives 

The expected impact of the AvSafe portfolio was evaluated against the NASA related objectives and 

strategies within the NASSP (ref. 20). As previously stated, Objectives 1A, 3A and 3B were omitted 

from the evaluation because these objectives do not fall within the current charter of the NASA AvSafe 

Program. Table 9 contains a mapping of expected impact of the current AvSafe portfolio on the NASA 

related Next Gen safety objectives. Tables 10-13 contains a mapping of the current AvSafe portfolio to 

each of the NextGen NASA related safety objectives and strategies. 

Table 9. Expected Impact of Current AvSafe Portfolio on NextGen NASA-Related Safety Objectives 

NextGen NASA-related safety objective 

Aviation safety project 

IIFD IRAC IVHM AAD 

Provide enhanced monitoring and safety analysis 

of the Air Transportation System [1B]. D 

Provide enhanced methods for ensuring safety is 

an inherent characteristic of the Next Generation 

Air Transportation System [1C]. 

D D 

Provide risk-reducing system interfaces [2A]. D 

Provide safety enhancements for airborne systems 

[2B]. D D D 

Provide safety enhancements for ground-based 

systems [2C]. 

Table 10. Mapping of Current AvSafe Portfolio to NextGen Objective 1B and Strategies 

Objective 1B: 

Provide enhanced monitoring and safety analysis of the Air Transportation System

Strategy AvSafe 

project Technology area or milestone 

Increase data access for safety risk management IVHM Data mining 

(IVHM research area 1.3) 
40 

 Table 11. Mapping of Current AvSafe Portfolio to NextGen Objective 1C and Strategies 

Objective 1C: 

Provide enhanced methods for ensuring safety is an inherent characteristic of the Next 

Generation Air Transportation System 

Strategy AvSafe 

project Technology area or milestone 

Advance capabilities for integrated 

safety assessment IIFD 

Predictive modeling of human 

interaction performance 

(IIFD subtopic IM.2) 

Enhance the focus on safe operational 

procedures IIFD 

Multimodal interfaces 

(IIFD research area MM) 

Information and interaction modeling 

(IIFD research area IM) 

Advance complex system validation 

and verification methods in support of 

operational use 

IVHM Verification and validation 

(IVHM research area 1.4) 

IRAC Verification and validation methods 

(IRAC research area 1.3) 

Table 12. Mapping of Current AvSafe Portfolio to NextGen Objective 2A and Strategies 

Objective 2A: 

Provide risk-reducing systems interfaces 

Strategy AvSafe 

project Technology area or milestone 

All four strategies within objective 2A IIFD Entire portfolio 
41 

Table 13. Mapping of Current AvSafe Portfolio to NextGen Objective 2B and Strategies 

Objective 2B: 

Provide safety enhancements for airborne systems 

Strategy AvSafe 

project Technology area or milestone 

Improve the reliability and airworthiness of 

aircraft 

IRAC Entire portfolio 

IVHM Entire portfolio 

AAD Entire portfolio 

Improve vehicle systems health management IVHM Entire portfolio 

Increase the reliability and accuracy of 

airborne systems data and information 

IIFD 

Information collection and management for 

reliability and integrity of service 

(IIFD subtopic EA.1) 

IRAC Verification and validation methods 

(IRAC research area 1.3) 

IVHM Verification and validation 

(IVHM research area 1.4) 
42 

4.4.6 Expected Impact of Current Portfolio on National Aeronautics R&D Plan Safety Goals 

Figure 7 contains a listing of the safety goals within the National Aeronautics R&D Plan. The NASA 

AvSafe projects that are expected to have an impact on the safety goals in the National Aeronautics R&D 

Plan are contained in Figure 8. 

Figure 7. Aviation Safety R&D Goals and Objectives 

(source: National Aeronautics R&D Plan, February 2010, p. 36). 
43 

Figure 8. Expected impact of current research portfolio on NASA AvSafe objectives tree. 

4.5 Set of Challenging Safety Issues 

All of the goals, objectives, and tall poles that were identified through the use of the systems analysis 

methodology (see Fig. 5) were used to develop the set of challenging safety issues that are given below in 

table 14 
44 

Table 14 Challenging Safety Issues 

GOAL 1: 

“Develop technologies to reduce accidents and incidents through enhanced vehicle design, structure, and 

subsystems.” 

Mitigate the consequences and hazards that are associated with in-flight loss of control. 

Improve technologies for ice detection and operation in icing conditions. 

Improve the reliability and airworthiness of aircraft. 

Improve vehicle systems health management. 

Increase the reliability and accuracy of airborne systems data and information. 

Ensure aircraft conformance to more stringent operational requirements. 

GOAL 2: 

“Develop technologies to reduce accidents and incidents through enhanced aerospace vehicle operations on 

the ground and in the air.”

Improve technologies and procedures for addressing the increasing complexity of and reliance on automation. 

Improve the protection, analysis, and dissemination of safety data. 

Mitigate the consequences and hazards that are associated with runway safety. 

Develop technologies and procedures to manage aircraft mixed fleet equipage in NextGen.* 

Develop technologies and procedures to manage super-density operations. 

Mitigate the consequences of human error and fatigue.* 

Mitigate the consequences and hazards that are associated with approach and landing accidents. 

Understand and mitigate the potential safety issues that are associated with unmanned aircraft systems 

(UAS).* 

GOAL 3: 

“Develop enhanced passenger and crew survivability in the event of an accident.” 

Mitigate the consequences and hazards that are associated with post-impact fire/smoke/toxic fumes.* 

Improve crash survivability of aircraft structures.* 

Improve evacuation and accident response procedures.* 

*Indicates a safety issue that is not currently being addressed in the AvSafe research portfolio. 

4.6 Research Alternatives 

Six of the safety issues that are given in table 14 are not currently being addressed in the AvSafe 

research portfolio. Note that human fatigue was included in this list because the IIFD research effort in 

the current portfolio that supports this safety issue is extremely limited and is not expected to have a 

direct impact on this in the future. For these six research areas, possible research alternatives that have the 

potential to address these safety issues were identified (see table 15. These research alternatives were 
45 

derived primarily from input that was obtained from NASA AvSafe researchers and project management 

but are also based on suggestions from external sources (e.g., CAST JIMDAT). These research 

alternatives have not been evaluated against the assessment criteria, nor have their technical merits been 

thoroughly evaluated. 

Table 15. Unaddressed Challenging Safety Issues and Corresponding Research Alternatives 

Challenging safety issue Research alternative(s) 

Develop technologies and procedures to manage 

aircraft mixed-fleet equipage in NextGen. Develop voice-free air traffic control systems. 

Mitigate the consequences of human error and fatigue. 

Research ‘smart’ systems that detect operator lapses in 

attention, such as vigilant crew members. 

Develop systems to monitor and detect pilot fatigue. 

Understand and mitigate the potential safety issues that 

are associated with unmanned aircraft systems (UAS). 

Manage and reduce risks from UAS accidents to other 

vehicles, persons, and property on the ground. 

Enable safe UAS operations by developing sense-andavoid capabilities for autonomous vehicles. 

Mitigate the consequences and hazards that are 

associated with post-impact fire/smoke/toxic fumes. 

Develop materials and structures that are fire resistant 

and do not emit significant smoke. 

Improve fuel-containment methods and create reduced 

volatility fuels to prevent fires and explosions. 

Develop improved cabin materials for reduced 

flammability and develop automated fire 

detection/protection systems. 

Develop passenger-safe fire suppression systems. 

Improve crash survivability of aircraft structures. 

Develop materials and structures that fail in a 

predesigned manner to maximize energy absorption 

(similar to automobiles). 

Improve crash simulation capabilities for evolving 

composite structures and assess crashworthiness under 

various accident scenarios. 

Improve evacuation and accident response procedures. 

Conduct egress research for more efficient cabin 

evacuation. 

Investigate the effectiveness of extremely rapid fuel 

dump (automated at/near impact). 

Develop inflatable, floating shelters for survivability 

after water landings. 
46 

5. Discussion and Conclusions 

Recall that the objectives tree for the National Aeronautics and Space Administration (NASA) 

Aviation Safety (AvSafe) program was organized to support both the safety goals of the National 

Aeronautics Research and Development (R&D) Plan and the safety-related objectives in the Joint 

Planning and Development Office (JPDO) National Aviation Safety Strategic Plan (NASSP). The current 

NASA AvSafe research portfolio, if successful, directly addresses all of the National Aeronautics R&D 

safety goals except goal 3 (i.e., develop enhanced passenger and crew survivability in the event of an 

accident). The fact that the NASA portfolio does not address this goal is not a major concern because, 

according to published reports (Refs. 21 and 22), the Federal Aviation Administration (FAA) is spending 

approximately $7.2 million in support of their Fire Research and Safety program. This FAA program is 

investigating technologies and procedures to (1) prevent accidents that are caused by in-flight fires and 

fuel-tank explosions and (2) improve the survivability of a post-crash fire. Note, however, that much of 

the FAA research portfolio is focused on reliability and on certification tools and methodologies, and that 

the FAA relies on collaboration with NASA in the following areas of research: 

x Aircraft icing, turbulence, wake turbulence, and weather technologies 

x Continued airworthiness 

x Catastrophic engine failure 

x Flight deck, maintenance, and human factors 

x Data mining and satellite data 

In regard to the JPDO NASSP safety objectives, the current NASA AvSafe research portfolio directly 

impacts all of the NASA-related safety objectives in the plan, except for objective 2C (i.e., provide safety 

enhancements for ground-based systems). However, many of the research goals that are contained in 

objective 2C actually fall under the charter of NASA’s Airspace Systems program. According to the 

NASA Airspace Systems program Web site (Ref. 1), the primary roles of each of the research initiatives 

within the Aeronautics Research Mission Directorate (ARMD) are as follows: 

x Airspace Systems program: operational aspects of the airspace system 

x Fundamental Aeronautics program: vehicles 

x AvSafe program: vehicle safety 

Because the charters of the Airspace Systems and Fundamental Aeronautics programs do not 

specifically include vehicle safety, the expectation is that the AvSafe program is responsible for this area 

of research. 

The evaluation of the NASA AvSafe research portfolio against both historic and future areas of 

significant safety risk indicates that the current AvSafe research portfolio will have no direct impact on 

three areas of future risk (i.e., human fatigue, aircraft mixed-fleet equipage, and enhanced survivability in 

the event of an accident), as well as no direct impact on the following historic areas of significant safety 

risk: 
47 

x Fire – post impact 

x Turbulence 

x Abnormal runway contact 

x Bird strikes 

x Controlled flight into terrain 

x Collision with object – takeoff or landing 

x Low-altitude operations 

x Loss of control – on ground 

x Power loss – fuel 

x Runway excursion 

Most of these research gaps in addressing the historic areas of safety risk are for Part 135 and Part 91 

operations. In fact, the majority of the research in the current AvSafe research portfolio is solely 

applicable to Part 121 operations. The only research in the current portfolio that is expected to directly 

impact Part 91 is in the area of system/component failure/malfunction (i.e., the IVHM project). Overall, 

the current portfolio, if successful, would have an indirect impact on more than 50 percent of the historic 

and future areas of significant safety risk; however, most of the current AvSafe program initiatives 

include research that is primarily at the fundamental level. 

Finally, of the 17 challenging safety issues that were identified, the current AvSafe program research 

portfolio directly addresses 11 of these issues. Of the six unaddressed issues, three can be categorized 

under National R&D goal 3 (i.e., develop enhanced passenger and crew survivability in the event of an 

accident). Another of these safety issues (i.e., mitigate the consequences of human error and fatigue) is 

categorized as unaddressed because the IIFD research effort in this area is extremely limited and is not 

expected to have a direct impact on this safety issue in the future. Additional resources would be needed 

to make a significant impact in this area. The remaining two unaddressed safety issues (i.e., (1) develop 

technologies and procedures to manage aircraft mixed-fleet equipage in NextGen and (2) understand and 

mitigate the potential safety issues associated with unmanned aircraft systems) generally fall more under 

the charters of the Airspace Systems program and the proposed Unmanned Aircraft Systems (UAS) 

research within the Integrated Systems Research program, respectively. The appropriate assignment of 

responsibility for this and other aviation safety research initiatives within the NASA ARMD should be 

based on some subset of the assessment criteria that were used in this study. A suggested rule of thumb is 

that any research effort that is subsequently funded within the Aviation Safety program should, at a 

minimum, indirectly address one of the identified current or future areas of significant safety risk. 
48 

References 

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September 30, 2009. http://www.aeronautics.nasa.gov/programs.htm Accessed March 2, 2010. 

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http://www.aeronautics.nasa.gov/programs.htm Accessed April 23, 2010. 

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Aircraft Accident Data, NTSB/ARC-02/03, PB2002-19241, 2002. http://ntsb.gov/publictn/2002/arc0203.pdf. 

Accessed June 14, 2010. 

 4. Commercial Aviation Safety Team/International Civil Aviation Organization (CAST/ICAO) Common 

Taxonomy Team: Aviation Occurrence Categories: Definitions and Usage Notes, version 4.1.4, October 2008. 

http://www.intlaviationstandards.org/ Accessed March 2, 2010. 

 5. Evans, J.K.: “A Description of Aviation Incidents During the Years 1985-2006,” ATK internal white paper, 

March 2009. 

 6. National Research Council (U.S.): Decadal Survey of Civil Aeronautics: Foundation for the Future, The 

National Academies Press, Washington, DC, 2006. 

 7. National Science and Technology Council: National Aeronautics Research and Development Plan, February 

2010. http://www.whitehouse.gov/sites/default/files/microsites/ostp/aero-rdplan-2010.pdf. Accessed June 14, 

2010. 

 8. National Transportation Safety Board: Most Wanted List 2010. 

http://www.ntsb.gov/recs/mostwanted/aviation_issues.htm. Accessed June 14, 2010. 

 9. Flight Safety Foundation: Current Safety Initiatives, 2010. http://flightsafety.org/current-safety-initiatives. 

Accessed June 14, 2010. 

10. Morello, Samuel A.; and Ricks, Wendell R.: “Aviation Safety Issues Database” National Aeronautics and Space 

Administration, NASA TM-2009-215706. 

11. Future Aviation Safety Team: Areas of Change. http://www.nlr-atsi.nl/fast/search.php. Accessed June 14, 2010 

12. http://www.faa.gov/about/initiatives/nextgen/media/ngip.pdf. Accessed June 14, 2010. 

13. Commercial Aviation Safety Team: Safety Enhancements. http://www.castsafety.org/pdf/safety_enhancements_completed.pdf. Accessed June 14, 2010. 

14. Federal Aviation Administration: Aviation Safety Information analysis and Sharing System (ASIAS). 

http://www.asias.faa.gov/portal/page/portal/ASIAS_PAGES/ASIAS_HOME. Accessed June 14, 2010. 

15. Commercial Aviation Safety Team: Safety Enhancement 30 Revision-5, Mode Awareness and energy State 

Management Aspects of Flight Deck Automation Final Report, August 2008. http://www.castsafety.org/pdf/cast_automation_aug08.pdf. Accessed June 14, 2010. 

16. Gibson, John E.; Scherer, William T.; and Gibson, William F.: How to Do Systems Analysis, John Wiley & 

Sons, Inc., Hoboken, New Jersey, 2007. 
49 

17. Scott, W.R.: Organizations: Rational, Natural and Open Systems, 5th Edition, Prentice Hall, Upper Saddle 

River, NJ, 2003. 

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http://www.nasa.gov/pdf/142302main_2006_NASA_Strategic_Plan.pdf Accessed June 14, 2010. 

19. National Aeronautics and Space Administration: FY2011 Budget Request. 

http://www.nasa.gov/pdf/428150main_Aeronautics_Research.pdf Accessed June 14, 2010. 

20. Joint Planning and Development Office: National Aviation Safety Strategic Plan Version 1.0. August 8, 2008. 

21. Federal Aviation Administration: government and Industry Affairs Fiscal Year 2010 Business Plan. 

http://www.faa.gov/about/plans_reports/media/AGI%20Business%20Plan%20with%20Cover.pdf. Accessed 

June 14, 2010. 

22. Federal Aviation Administration: National Aviation Research Plan (NARP), April 26, 2010. 

http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/nextgen/research_tech_dev/research

_planning/narp/. Accessed June 14, 2010. 

23. National Aeronautics and Space Administration: NASA Systems Engineering Handbook, Revision 1, December 

2007, NASA SP-2007-6105. 

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National Academies Press. 

25. Jones, Sharon Monica; and Reveley, Mary S.: “An Overview of the NASA Aviation Safety Program Assessment 

Process,” Proceedings of the AIAA 3rd Annual Aviation Technology, Integration and Operations (ATIO) Forum, 

Denver, CO, November 2003. 
50 

Appendix A. Aviation Occurrence Categories 

The CAST/ICAO Common Taxonomy Team (CICTT) was jointly chartered by the International Civil 

Aviation Organization (ICAO) and the Commercial Aviation Safety Team (CAST) and was charged with 

developing common taxonomies and definitions for aviation accident and incident reporting systems. (For 

additional information, see http://www.intlaviationstandards.org/.) The occurrence categories that were 

used in this study are listed below, with a brief description of each category. The information is taken 

from a document that is dated October 2008. 

CICTT Categories 

Abnormal runway contact (ARC): Any takeoff or landing that involves abnormal contact with the 

runway or landing surface. Included are hard/heavy landings, long/fast landings, crabbed landings, nosewheel-first touchdowns, tail strikes, wing/nacelle strikes, and gear-up landings. 

Abrupt maneuver (AMAN): Occurrences that involve the intentional abrupt maneuvering of the aircraft 

(in flight or on the ground) by the flight crew to avoid a collision with terrain, objects, weather, or other 

aircraft. 

Aerodrome (ADRM): Occurrences that involve aerodrome design, service, or functionality issues. The 

aerodrome includes runways, taxiways, ramp areas, parking areas, buildings and structures, lighting, 

signage, and crash/fire/rescue (CFR) services. 

ATM/CNS (ATM): Occurrences that involve air traffic management (ATM) or communication, 

navigation, or surveillance (CNS) service issues. 

Bird strike (BIRD): Occurrences that involve collisions or near collisions with bird(s) or other wildlife. 

Cabin safety events (CABIN): Occurrences that involve significant events in the passenger cabin related 

to carry-on baggage, supplemental oxygen, missing or non-operational emergency equipment, the 

inadvertent deployment of emergency equipment, or the medical emergency (not caused by turbulence 

encounters) of persons other than the flight crew or medical evacuation patients. 

Collision with obstacle(s) during takeoff and landing (CTOL): Occurrences that involve collision with 

an object or obstacle during airborne phases of takeoff or landing. 

Controlled flight into or toward terrain (CFIT): Occurrences that involve an in-flight collision or near 

collision with terrain, water, or obstacle without indication of loss of control. Excludes intentional lowaltitude operations, intentional flight into terrain, and runway undershoot/overshoot. 

Evacuation (EVAC): Occurrences that involve one or more of the following: an unnecessary evacuation 

was conducted; person(s) were injured during the evacuation; evacuation equipment failed to perform as 

required; or the evacuation was a factor in the outcome. 

Fire/smoke nonimpact (FI-NI): Occurrences that involve fire or smoke in the aircraft (in flight or on the 

ground) which was not the result of an impact. 

Fire/smoke impact (FI-POST): Occurrences that involve fire or smoke resulting from impact. 
51 

Fuel related (FUEL): Occurrences that involve one or more powerplants experiencing reduced or no 

power output due to fuel exhaustion (i.e., no usable fuel on board), fuel starvation (i.e., usable fuel is not 

available to the engine), fuel contamination (i.e., by water, sand, dirt, bugs), wrong fuel, or carburetor 

and/or induction icing. 

Ground handling (RAMP): Occurrences during (or as a result of) ground operations, including preflight 

configuration errors that lead to subsequent events (such as improperly latched doors, pitot tube 

contamination, or weight/balance issues). 

Ground collision (GCOL): Occurrences that involve collision with an aircraft, person, animal, ground 

vehicle, building, and so on while taxiing to or from a runway in use. 

Icing (ICE): Occurrences that involve the accumulation of snow, ice, freezing rain, or frost on aircraft 

surfaces to the extent that aircraft control or performance is adversely affected. 

Loss of control – ground (LOC-G): Occurrences that involve the loss of aircraft control while the 

aircraft is on the ground, which may result from a contaminated runway, evasive action due to a runway 

incursion, or the failure or malfunction of a system or component. 

Loss of control – in flight (LOC-I): Occurrences that involve the loss of aircraft control while in flight; 

may occur in instrument meteorological conditions (IMC) or visual meteorological conditions (VMC). 

Low-altitude operations (LALT): Occurrences that involve collision or near collision with 

terrain/objects/obstacles while intentionally operating near the surface (excludes landing and takeoff 

phases). Includes aerobatics, sightseeing, aerial photography, aerial application, scud running, and flying 

in close proximity to mountains or box canyons where the aircraft aerodynamic capability is not sufficient 

to avoid impact. 

Airprox/TCAS alert/loss of separation/near midair collision/midair collision (MAC): Occurrences 

that involve airprox, TCAS alerts, or loss of separation, or involve a near collision or collision between 

aircraft in flight. 

Other (OTHER): Any occurrence not covered under another category. 

Runway excursion (RE): A veer off the side or overrun off the end of the runway. 

Runway incursion – animal (RI-A): Occurrences that involve collision with, risk of collision with, or 

evasive action taken by an aircraft to avoid an animal (other than birds) on the runway in use. 

Runway incursion – vehicle, aircraft, or person (RI-VAP): Occurrences that involve the incorrect 

presence of an aircraft, vehicle, or person on the protected area of a surface designated for takeoffs or 

landings. 

Security related (SEC): Occurrences that involve criminal- or security-related acts such as hijacking, 

aircraft theft, flight control interference, sabotage, or suicide. 

System/component failure or malfunction – Non-powerplant (SCF-NP): Occurrences that involve 

failure or malfunction of an aircraft system or component other than the powerplant. 
52 

System/component failure or malfunction – Powerplant (SCF-PP): Occurrences that involve failure 

or malfunction of an aircraft system or component that is related to the powerplant. 

Turbulence encounter (TURB): Occurrences that involve in-flight encounter with turbulence; includes 

clear-air or cloud turbulence, mountain wave, and wake vortex. 

Undershoot/overshoot (USOS): Occurrences that involve a touchdown off the runway surface but in 

close proximity to the runway; excludes off-airport emergency landings. 

Unknown or undetermined (UNK): Occurrences for which insufficient information exists to categorize 

the accident; includes missing aircraft. 

Wind shear or thunderstorm (WSTRW): Occurrences that involve flight into wind shear or 

thunderstorm; includes hail and heavy rain. 

Additional Categories 

Many of the following categories were added in order to completely capture an event sequence. For 

example, an emergency landing is required for most cases in which a system/component fails or 

malfunctions and engine power is lost, and also may be performed after an encounter with adverse 

weather; furthermore, this type of landing is not likely to be without further incident. Control of the 

aircraft may be lost; hard or bounced landings may occur; terrain that is unsuitable for a proper landing 

may be encountered; the aircraft may collide with power lines, fences, or ground vehicles during an offairport landing; or the aircraft may be unable to avoid rising terrain due to degraded performance. The 

single category of “Loss of engine power” is not sufficient to explain why the aircraft was destroyed. 

Several categories (e.g., collisions with terrain or objects and loss of control) were further subdivided 

by general phase of flight (i.e., ground, takeoff, in flight, approach/landing) because either the root cause 

or the consequences of the occurrence differ by phase of flight. 

Collision with object – ground (CWO-G): Occurrences that involve a collision with an object or 

obstacle on the ground away from an airport environment. 

Collision with terrain – approach/landing (CWT-AL): Occurrences that involve a collision with 

terrain during the approach to land or during a go-around/missed approach. CFIT (i.e., controlled flight 

into terrain) is not an appropriate category in these cases for one of two reasons: a system/component 

failure/malfunction or nonmechanical loss of engine power necessitated the landing or the pilot did not 

maintain sufficient altitude above high vegetation. This code was also used in cases where the pilot 

ditched the aircraft in water. 

Encounter with terrain – ground (EWT-G): Occurrences that involve an encounter with terrain on the 

ground away from an airport environment, causing damage to the aircraft. 

In-flight break up (IFBU): Occurrences that involve separation of multiple surfaces of the aircraft, 

resulting either from loss of control or from forces associated with severe weather. 
53 

Pilot incapacitation or severe impairment (INCAP): Occurrences that involve the pilot becoming 

incapacitated (due to illness or fatigue) or severely impaired (due to illness, alcohol or illegal drugs). Does 

not include minor impairment caused by fatigue or the use of unapproved prescription medications. 

Loss of engine power – fuel related (PL-FUEL): Occurrences that involve the loss of engine power due 

to fuel exhaustion (i.e., no usable fuel on board), fuel starvation (i.e., usable fuel is not available to the 

engine), fuel contamination (e.g., by water, sand, dirt, or bugs), wrong fuel, or carburetor and/or induction 

icing (see FUEL above). 

Loss of engine power – other reasons (PL-OTHER): Occurrences that involve the loss of engine power 

due to other nonmechanical reasons. Reasons include foreign object damage (e.g., bird strikes), ice 

ingestion, improper simulated engine-out procedures, or other improper procedures. 

Loss of engine power – unknown reasons (PL-UNK): Occurrences that involve the loss of engine 

power for which the exact cause is undetermined. 
54 

Appendix B. Accidents, Injuries, and Incidents by Aviation Occurrence 

Category 

Table B-1. Number of Accidents by CICTT Occurrence Category (1997–2006) 

CICTT occurrence category Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 Part 91 

Total accidents 459 78 540 12247 

Abrupt maneuver 16 (3.5%) 1 (0.2%) 48 (0.4%) 

Abnormal runway contact 43 (9.4%) 10 (12.8%) 57 (10.6%) 1577 (12.9%) 

Aerodrome 8 (1.7%) 3 (3.8%) 20 (3.7%) 132 (1.1%) 

Air traffic management 7 (1.5%) 7 (1.3%) 72 (0.6%) 

Bird strikes 14 (3.1%) 8 (10.3%) 5 (0.9%) 27 (0.2%) 

Cabin safety or pilot incapacitation 5 (1.1%) 5 (0.9%) 155 (1.3%) 

Controlled flight into terrain 2 (0.4%) 9 (11.5%) 51 (9.4%) 384 (3.1%) 

Collision with object – on ground* 12 (2.6%) 3 (3.8%) 31 (5.7%) 1225 (10.0%) 

Collision with object – takeoff or 

landing 2 (2.6%) 28 (5.2%) 1209 (9.9%) 

Collision with terrain – 

approach/landing* 2 (0.4%) 2 (2.6%) 32 (5.9%) 495 (4.0%) 

Encounter with terrain – on ground * 1 (0.2%) 6 (7.7%) 32 (5.9%) 815 (6.7%) 

Evacuation 28 (6.1%) 1 (1.3%) 1 (0.2%) 

Fire – nonimpact 15 (3.3%) 2 (2.6%) 9 (1.7%) 130 (1.1%) 

Fire – post impact 14 (3.1%) 4 (5.1%) 69 (12.8%) 1137 (9.3%) 

Ground collision 30 ( 6.5%) 1 (1.3%) 23 (4.3%) 223 (1.8%) 

Ground handling or preflight 121 (26.4%) 4 (5.1%) 29 (5.4%) 279 (2.3%) 

Icing 2 (0.4%) 8 (10.3%) 31 (5.7%) 148 (1.2%) 

In-flight breakup* 5 (0.9%) 78 (0.6%) 

Low-altitude operations 1 (0.2%) 2 (2.6%) 17 (3.1%) 686 (5.6%) 

Loss of control – in flight 8 (1.7%) 11 (14.1%) 94 (17.4%) 2390 (19.5%) 

Loss of control – on ground 1 (0.2%) 5 (6.4%) 53 (9.8%) 1813 (14.8%) 

Midair collision 3 (0.7%) 1 (1.3%) 9 (1.7%) 152 (1.2%) 

Power loss – fuel 1 (0.2%) 43 (8.0%) 1561 (12.7%) 

Power loss – other reason* 5 (1.1%) 5 (0.9%) 105 (0.9%) 

Power loss – unknown reason* 1 (0.2%) 1 (1.3%) 27 (5.0%) 708 (5.8%) 

Runway excursion 36 (7.8%) 14 (17.9%) 79 (14.6%) 2434 (19.9%) 

Runway incursion (Animal, vehicle, 

aircraft, or Person) 5 (1.1%) 7 (1.3%) 139 (1.1%) 

SCF – powerplant 15 (3.3%) 3 (3.8%) 42 (7.8%) 776 (6.3%) 

SCF – nonpowerplant 40 (8.7%) 8 (10.3%) 59 (10.9%) 877 (7.2%) 

Security related 4 (0.9%) 38 (0.3%) 

Turbulence encounter 116 (25.3%) 2 (2.6%) 5 (0.9%) 87 (0.7%) 

Thunderstorm or windshear 6 (1.3%) 8 (1.5%) 112 (0.9%) 

Undershoot or overshoot 2 (0.4%) 3 (3.8%) 17 (3.1%) 239 (2.0%) 

Other 1 (1.3%) 4 (0.7%) 30 (0.2%) 

Unknown or undetermined 2 (0.4%) 8 (1.5%) 103 (0.8%) 
55 

Table B-2. Number of Injuries in Accidents by CICTT Occurrence Category (1997–2006) 

CICTT occurrence category Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 Part 91 

Total injuries 1956 142 585 9846 

Abrupt maneuver 299 (15.3%) 1 (0.2%) 43 (0.4%) 

Abnormal runway contact 44 (2.2%) 19 (6.3%) 16 (2.7%) 355 (3.6%) 

Aerodrome 6 (0.3%) 0 (0.0%) 1 (0.2%) 24 (0.2%) 

Air-traffic management 9 (0.5%) 4 (0.7%) 77 (0.8%) 

Bird strikes 2 (0.1%) 0 (0.0%) 3 (0.5%) 6 (0.1%) 

Cabin safety or pilot incapacitation 5 (0.3%) 11 (1.9%) 257 (2.6%) 

Controlled flight into terrain 18 (0.9%) 33 (17.5%) 112 (19.1%) 750 (7.6%) 

Collision with object – on ground* 144 (7.4%) 1 (0.7%) 23 (3.9%) 437 (4.4%) 

Collision with object – takeoff or landing 1 (0.7%) 43 (7.4%) 1448 (14.7%) 

Collision with terrain – Approach/Landing* 2 (0.1%) 8 (5.6%) 57 (9.7%) 591 (6.0%) 

Encounter with terrain – on ground* 0 (0.0%) 6 (4.2%) 19 (3.2%) 421 (4.3%) 

Evacuation 253 (12.9%) 8 (5.6%) 6 (1.0%) 

Fire – nonimpact 104 (5.3%) 0 (0.0%) 14 (2.4%) 81 (0.8%) 

Fire – Post impact 498 (25.5%) 47 (33.1%) 175 (29.9%) 2348 (23.8%) 

Ground collision 13 (0.7%) 0 (0.0%) 0 (0.0%) 58 (0.6%) 

Ground handling or preflight 107 (5.5%) 11 (7.7%) 47 (8.0%) 423 (4.3%) 

Icing 0 (0.0%) 50 (35.2%) 33 (5.6%) 206 (2.1%) 

In-flight breakup* 9 (1.5%) 192 (2.0%) 

Low-altitude operations 0 (0.0%) 4 (2.8%) 35 (6.0%) 1086 (11.0%) 

Loss of control – in flight 405 (20.7%) 69 (48.6%) 195 (33.3%) 3941 (40.0%) 

Loss of control – on ground 0 (0.0%) 1 (0.7%) 25 (4.3%) 408 (4.1%) 

Midair collision 3 (0.2%) 5 (3.5%) 14 (2.4%) 344 (3.5%) 

Power loss – fuel 2 (0.1%) 74 (12.6%) 1443 (14.7%) 

Power loss – other reason* 0 (0.0%) 11 (1.9%) 108 (1.1%) 

Power loss – unknown reason* 0 (0.0%) 1 (0.7%) 26 (4.4%) 669 (6.8%) 

Runway excursion 244 (12.5%) 12 (8.5%) 39 (6.7%) 653 (6.6%) 

Runway incursion (animal, vehicle, aircraft, 

or person) 1 (0.1%) 1 (0.2%) 45 (0.5%) 

SCF – powerplant 17 (0.9%) 12 (8.5%) 72 (12.3%) 738 (7.5%) 

SCF – nonpowerplant 319 (16.3%) 14 (9.8%) 26 (4.4%) 398 (4.0%) 

Security related 265 (13.5%) 40 (0.4%) 

Turbulence encounter 580 (29.7%) 4 (2.8%) 3 (0.5%) 96 (1.0%) 

Thunderstorm or windshear 121 (6.2%) 17 (2.9%) 167 (1.7%) 

Undershoot or overshoot 23 (1.2%) 0 (0.0%) 11 (1.9%) 120 (1.2%) 

Other 0 (0.0%) 5 (0.9%) 24 (0.2%) 

Unknown or undetermined 0 (0.0%) 29 (5.0%) 190 (1.9%) 
56 

Table B-3. Number of Fatal Accidents by CICTT Occurrence Category (1997–2006) 

CICTT occurrence category Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 Part 91 

Total fatal accidents 25 15 122 2328 

Abrupt maneuver 1 (4.0%) 15 (0.6%) 

Abnormal runway contact 1 (6.7%) 23 (1.0%) 

Aerodrome 1 (0.1%) 

Air-traffic management 3 (2.5%) 40 (1.7%) 

Bird strikes 1 (0.1%) 

Cabin safety or pilot incapacitation 5 (4.1%) 121 (5.2%) 

Controlled flight into terrain 1 (4.0%) 4 (26.7%) 32 (26.2%) 302 (13.0%) 

Collision with object – on ground* 2 (8.0%) 2 (1.6%) 28 (1.2%) 

Collision with object – takeoff or 

landing 1 (6.7%) 5 (4.1%) 209 (9.0%) 

Collision with terrain – 

approach/landing* 1 (4.0%) 1 (6.7%) 7 (5.7%) 80 (3.4%) 

Encounter with terrain – on ground* 1 (0.8%) 9 (0.4%) 

Evacuation 1 (4.0%) 1 (6.7%) 

Fire – nonimpact 2 (1.6%) 16 (0.7%) 

Fire – post impact 7 (28.0%) 3 (20.0%) 50 (41.0%) 831 (35.7%) 

Ground collision 3 (0.1%) 

Ground handling or preflight 10 (40.0%) 2 (13.3%) 4 (3.3%) 88 (3.8%) 

Icing 3 (20.0%) 14 (11.5%) 62 (2.7%) 

In-flight breakup* 5 (4.1%) 78 (3.4%) 

Low-altitude operations 1 (6.7%) 9 (7.4%) 412 (17.7%) 

Loss of control – in flight 6 (24.0%) 8 (53.3%) 56 (45.9%) 1276 (54.8%) 

Loss of control – on ground 13 (0.6%) 

Midair collision 4 (3.3%) 104 (4.5%) 

Power loss – fuel 1 (4.0%) 8 (6.6%) 164 (7.0%) 

Power loss – other reason* 10 (0.4%) 

Power loss – unknown reason* 1 (6.7%) 6 (4.9%) 105 (4.5%) 

Runway excursion 3 (12.0%) 1 (0.8%) 33 (1.4%) 

Runway incursion (Animal, vehicle, 

aircraft, or person) 4 (0.2%) 

SCF – powerplant 1 (6.7%) 8 (6.6%) 110 (4.7%) 

SCF – nonpowerplant 5 (20.0%) 2 (13.3%) 6 (4.9%) 78 (3.4%) 

Security related 4 (16.0%) 25 (1.1%) 

Turbulence encounter 1 (4.0%) 2 (1.6%) 31 (1.3%) 

Thunderstorm or windshear 1 (4.0%) 5 (4.1%) 55 (2.4%) 

Undershoot or overshoot 1 (0.8%) 4 (0.2%) 

Other 2 (1.6%) 12 (0.5%) 

Unknown or undetermined 7 (5.7%) 88 (3.8%) 
57 

Table B-4. Number of Fatalities by CICTT Occurrence Category (1997–2006) 

CICTT occurrence category Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 Part 91 

Total fatalities 752 80 292 4535 

Abrupt maneuver 265 (35.2%) 23 ( 0.5%) 

Abnormal runway contact 5 (6.3%) 34 (0.7%) 

Aerodrome 1 (0.0%) 

Air-traffic management 2 (0.7%) 73 (1.6%) 

Bird strikes 2 (0.0%) 

Cabin safety or pilot incapacitation 11 (3.8%) 199 (4.4%) 

Controlled flight into terrain 13 (1.7%) 14 (17.5%) 79 (27.1%) 596 (13.1%) 

Collision with object – on ground* 12 (1.6%) 2 (0.7%) 49 (1.1%) 

Collision with object – takeoff or 

landing 1 (1.3%) 5 (1.7%) 358 (7.9%) 

Collision with terrain – 

approach/landing* 1 (0.1%) 2 (2.5%) 10 (3.4%) 124 (2.7%) 

Encounter with terrain – on ground* 1 (0.3%) 16 (0.4%) 

Evacuation 1 (0.1%) 2 (2.5%) 

Fire – nonimpact 2 (0.7%) 30 (0.7%) 

Fire – post impact 367 (48.4%) 40 (50.0%) 119 (40.8%) 1742 (38.4%) 

Ground collision 3 (0.1%) 

Ground handling or preflight 34 (4.5%) 11 (13.8%) 14 (4.8%) 200 (4.4%) 

Icing 47 (58.8%) 17 (5.8%) 133 (2.9%) 

In-flight breakup* 9 (3.1%) 191 (4.2%) 

Low-altitude operations 2 (2.5%) 24 (8.2%) 730 (16.1%) 

Loss of control – in flight 402 (53.5%) 61 (76.3%) 148 (50.7%) 2543 (56.1%) 

Loss of control – on ground 17 (0.4%) 

Midair collision 14 (4.8%) 300 (6.6%) 

Power loss – fuel 1 (0.1%) 31 (10.6%) 270 (6.0%) 

Power loss – other reason* 14 (0.3%) 

Power loss – unknown reason* 1 (1.3%) 9 (3.1%) 193 (4.3%) 

Runway excursion 61 (8.1%) 1 (0.3%) 58 (1.3%) 

Runway incursion (Animal, vehicle, 

aircraft, or person) 6 (0.1%) 

SCF – powerplant 2 (2.5%) 20 (6.8%) 237 (5.2%) 

SCF – nonpowerplant 133 (17.9%) 6 (7.5%) 11 (3.8%) 145 (3.2%) 

Security related 265 (35.2%) 29 ( 0.6%) 

Turbulence 1 (0.1%) 3 (1.0%) 66 (1.5%) 

Thunderstorm or windshear 11 (1.4%) 10 (3.4%) 123 (2.7%) 

Undershoot or overshoot 1 (0.3%) 6 (0.1%) 

Other 3 (1.0%) 15 (0.3%) 

Unknown or undetermined 25 (8.6%) 166 (3.7%) 
58 

Table B-5. Number of Incidents by CICTT Occurrence Category (1997–2006) 

CICTT occurrence category Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 Part 91 

Total incidents 3752 188 1117 12773 

Abnormal runway contact 61 (1.6%) 12 (6.4%) 85 (7.6%) 3164 (24.8%) 

Air-traffic management 2 (0.1%) 1 (0.0%) 

Aerodrome 52 (1.4%) 1 (0.5%) 18 (1.6%) 185 (1.4%) 

Bird strikes 128 (3.4%) 5 (2.7%) 20 (1.8%) 86 (0.7%) 

Cabin safety or pilot incapacitation 60 (1.6%) 1 (0.5%) 3 (0.3%) 13 (0.1%) 

Collision with object – on ground* 61 (1.6%) 9 (4.8%) 57 (5.1%) 434 (3.4%) 

Collision with object – takeoff or 

landing 10 (0.3%) 3 (1.6%) 15 (1.3%) 175 (1.4%) 

Evacuation 9 (0.2%) 

Fire – nonimpact 156 (4.2%) 10 (5.3%) 36 (3.2%) 155 1.2%) 

Ground collision 10 (0.3%) 6 (0.5%) 45 (0.4%) 

Ground handling or preflight 427 (11.4%) 23 (12.2%) 94 (8.4%) 525 (4.1%) 

Icing 2 (0.1%) 9 (0.8%) 21 (0.2%) 

Low-altitude operations 1 (0.5%) 25 (0.2%) 

Loss of control – on ground 35 (0.9%) 2 (1.1%) 25 (2.2%) 560 (4.4%) 

Midair collision 29 (0.8%) 2 (1.1%) 7 (0.6%) 110 (0.9%) 

Power loss – fuel 22 (0.6%) 3 (1.6%) 15 (1.3%) 721 (5.6%) 

Power loss – other or unknown 

reason* 2 (0.1%) 1 (0.5%) 9 (0.8%) 214 (1.7%) 

Runway excursion 74 (2.0%) 13 (6.9%) 70 (6.3%) 1156 (9.1%) 

Runway incursion (Animal, vehicle, 

aircraft, or person) 29 (0.8%) 1 (0.5%) 3 (0.3%) 37 (0.3%) 

SCF – powerplant 592 (15.8%) 25 (13.3%) 159 (14.2%) 1220 (10.0%) 

SCF – nonpowerplant 1650 (44.0%) 70 (37.2%) 448 (40.1%) 3474 (27.2%) 

Security related 129 (3.4%) 1 (0.5%) 1 (0.1%) 12 (0.1%) 

Turbulence encounter 83 (2.2%) 1 (0.5%) 6 (0.5%) 8 (0.1%) 

Thunderstorm or windshear 25 (0.7%) 11 (5.9%) 2 (0.2%) 10 (0.1%) 

Other weather 5 (0.1%) 3 (0.3%) 25 (0.2%) 

Undershoot or overshoot 3 (0.1%) 1 (0.5%) 4 (0.4%) 69 (0.5%) 

Other 65 (1.7%) 1 (0.5%) 13 (1.2%) 237 (1.9%) 

Unknown or undetermined 31 (0.8%) 2 (1.1%) 9 (0.8%) 91 (0.7%) 
59 

Appendix C. Total Accidents and Fatal Accidents by Aviation Occurrence 

Category 

Figure C-1. Number of accidents by CICTT occurrence category for Part 121 operations (1997–2006). 

Figure C-2. Number of fatal accidents by CICTT occurrence category for Part 121 operations (1997–2006). 
60 

Figure C-3. Number of accidents by CICTT occurrence category for Scheduled Part 135 operations (1997–2006). 

Figure C-4. Number of fatal accidents by CICTT occurrence category for Scheduled Part 135 operations (1997–

2006). 
61 

Figure C-5. Number of accidents by CICTT occurrence category for Non-Scheduled Part 135 operations (1997–

2006). 

Figure C-6. Number of fatal accidents by CICTT occurrence category for Non-Scheduled Part 135 operations 

(1997–2006). 
62 

Figure C-7. Number of accidents by CICTT occurrence category for Part 91 operations (1997–2006). 

Figure C-8. Number of fatal accidents by CICTT occurrence category for Part 91 operations (1997–2006). 
63 

Appendix D. Integrated Resilient Aircraft Control (IRAC) Technology List 

TECHNOLOGY NAME DESCRIPTION

1 – Adaptive Control Algorithm Development

This control technology would be used in response to the unanticipated as well as anticipated flight 

anomalies. Adaptive control technologies will augment stability augmentation systems to make 

automatic modifications to the control system of an aircraft operating under adverse flight conditions to 

improve the closed-loop stability margins of the aircraft. Seven specific approaches are being examined: 

(1) hybrid direct-indirect, (2) L1, (3) direct, (4) linear quadratic (LQ) optimal, (5) robust composite, (6) 

adaptive loop recovery and (7) M-MRAC (Modified Model Reference Adaptive Control). 

2 – Maneuvering Envelope ID Algorithms

All flight plans are based on “healthy aircraft” however, if there is damage, failure or degradation to the 

aircraft, the aerodynamics will not behave as designed. Given such an aircraft, this technology uses 

system ID and sensor output to predict new feasible trim states and to calculate a safe operation 

envelope. This information enables the pilot to make better decisions instead of relying solely on the 

flight controller. This technology feeds into #3 (Emergency Trajectory & Flight Planning Guidance).

3 – Emergency Trajectory & Flight Planning 

Guidance Algorithms

This technology would be used by an aircraft in an emergency situation that needs to land immediately. 

Emergency planning uses mathematical optimization techniques to assist the pilot in finding the best 

airport to land and trajectory planning does the analysis to determine the path to get the aircraft to this 

identified airport. Sources of inputs for the algorithm include the pilot and the output of technology #2 

(Maneuvering Envelope ID Algorithms). This technology could be used on both commercial and GA 

aircraft.

4 – Aerodynamic Modeling of Off-Nominal 

Flight 

The primary objective of this technology is to model the flight dynamic characteristics of a transport 

aircraft in damaged or failure conditions. The results of this research will enable a better understanding 

of how an aircraft will fly under extreme off-nominal conditions. For example, one specific research 

experiment in this area examines the impact of losing a significant portion of the wing on aerodynamic 

stability and control.

5 – Flight Dynamic Models of Unsteady 

Aerodynamics

This technology will enable a better understanding of the stability and control characteristics of aircraft 

under upset or adverse conditions. The primary objective of this technology is to develop dynamic and 

physics based models of unsteady aerodynamics. Research in this area consists of collecting wind 

tunnel data, conducting corresponding flight tests and comparing these results to see if there are 

correlations or discrepancies. 

6 – Airframe Icing Modeling

The outputs of the research in this technology are airframe related icing models that examine: (1) how 

does ice accumulate and (2) what are the effects of icing on aircraft stability and control. Specific 

research steps in the development of this technology include an examination of the physics of ice 

accretion on a swept wing and updates to a 3D ice accretion code (LEWICE3D). 
64 

TECHNOLOGY NAME DESCRIPTION

7 – Real Time Full-Envelope Flight Dynamic 

Modeling

The end result of this technology is the development of a 6 DOF full-envelope simulation model rapidly 

from flight data. One step in the creation of this model is the development of a real-time dynamic 

model from flight data. The overall goal of this research is the ability to estimate aircraft stability and 

control derivates in real time. The results of this technology will enable realistic flight mission 

rehearsal and pilot training.

8 – C-MAPSS Enhancements

C-MAPSS (Commercial Modular Aero-Propulsion System Simulation) is a tool for the simulation of a 

realistic large commercial turbofan engine. The code is a combination of Matlab (The MathWorks, Inc.) 

and Simulink (The MathWorks, Inc.). It is a generic engine simulation that is intended for general 

release to the public for research purposes. Proposed research includes an effort to collect engine 

dynamic data at altitude to understand the true engine capability as well as stall margin behavior 

during the transients. In addition, data will be analyzed by an engine company to model the engine 

dynamic performance. The results of these research efforts will be used to calibrate the C-MAPSS2 

model

 9 – Engine Icing Modeling

Ice can accrete inside an aircraft engine during flight into a cloud of ice crystals/water droplets, 

resulting in engine surge, stall, roll back, or flameout. The output of this technology is engine icing 

formation models that enable a better understanding of engine icing conditions, which could be used to 

design controllers that alleviate ice formation.

10 – Engine Performance, Usage & Prognostic 

Modeling

This technology could be helpful to pilots in determining the potential for failure of an engine while in 

flight. The modeling in this research examines: (1) engine performance at various operating conditions 

which are not normally included in engine baseline simulations (high angle of attack engine 

performance model and engine dynamic performance models) and (2) engine life monitoring and 

prognosis (stochastic component life models, engine "life meter" for monitoring life usage, prognostic 

model to predict risk). 

11- Probabilistic Based Tool Suite for 

Quantitative Assessment of Adaptive Control 

Systems

Despite more than 5 decades of research, the robustness of adaptive control is not well understood. 

This technology is key to the implementation of technology #1 (Adaptive Control Algorithm 

Development). The results of this research will be used in the assessment and certification of adaptive 

control technologies. 
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A three-month study (February to April 2010) of the NASA Aviation Safety (AvSafe) program was conducted. This study comprised three components: (1) a 

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