Mary S. Reveley, Jeffrey L. Briggs, and Megan A. Thomas

Glenn Research Center, Cleveland, Ohio

Joni K. Evans

Alliant Techsystems, Inc., Hampton, Virginia

Sharon M. Jones

Langley Research Center, Hampton, Virginia

An Examination of Commercial Aviation Accidents 

and Incidents Related to Integrated Vehicle Health 

Management

NASA/TM—2011-217023

June 2011

AIAA–2009–7124
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Mary S. Reveley, Jeffrey L. Briggs, and Megan A. Thomas

Glenn Research Center, Cleveland, Ohio

Joni K. Evans

Alliant Techsystems, Inc., Hampton, Virginia

Sharon M. Jones

Langley Research Center, Hampton, Virginia

An Examination of Commercial Aviation Accidents 

and Incidents Related to Integrated Vehicle Health 

Management

NASA/TM—2011-217023

June 2011

AIAA–2009–7124

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Space Administration

Glenn Research Center

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NASA/TM—2011-217023 1 

An Examination of Commercial Aviation Accidents and Incidents 

Related to Integrated Vehicle Health Management 

Mary S. Reveley, Jeffrey L. Briggs, and Megan A. Thomas 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Joni K. Evans 

Alliant Techsystems, Inc. 

Hampton, Virginia 23681 

Sharon M. Jones 

National Aeronautics and Space Administration 

Langley Research Center 

Hampton, Virginia 23681 

Abstract 

The Integrated Vehicle Health Management (IVHM) Project is one of the four projects within the 

National Aeronautics and Space Administration’s (NASA) Aviation Safety Program (AvSafe). The 

IVHM Project conducts research to develop validated tools and technologies for automated detection, 

diagnosis, and prognosis that enable mitigation of adverse events during flight. Adverse events include 

those that arise from system, subsystem, or component failure, faults, and malfunctions due to damage, 

degradation, or environmental hazards that occur during flight. Determining the causal factors and 

adverse events related to IVHM technologies will help in the formulation of research requirements and 

establish a list of example adverse conditions against which IVHM technologies can be evaluated. This 

paper documents the results of an examination of the most recent statistical/prognostic accident and 

incident data that is available from the Aviation Safety Information Analysis and Sharing (ASIAS) 

System to determine the causal factors of system/component failures and/or malfunctions in U.S. 

commercial aviation accidents and incidents. 

Nomenclature 

AIDS Accident/Incident Data System 

AvSafe Aviation Safety Program 

ASIAS Aviation Safety Information Analysis and Sharing 

ASRS Aviation Safety Reporting System 

FAA Federal Aviation Administration 

FMC Flight Management Computer 

FMS Flight Management System 

GPWS Ground Proximity Warning System 

NTSB National Transportation Safety Board 

ILS Instrument Landing System 

ILS Inertial Navigation System 

IVHM Integrated Vehicle Health Management 

NASA National Aeronautics and Space Administration 

JPDO Joint Planning and Development Office 

SCFM System/Component Failure/Malfunction 

TCAS Traffic Collision Avoidance System 
NASA/TM—2011-217023 2 

TM Technical Memorandum 

VHF Very High Frequency 

VOR VHF Omni-directional Radio 

Introduction 

The need for integrated vehicle health management research for the purpose of improving aviation 

safety has been affirmed by leaders in the aviation community. The “Decadal Survey of Civil Aeronautics: 

Foundation for the Future”, (Ref. 1) cites integrated vehicle health management as being one of a group of 

the highest research and technology challenges for NASA aeronautics. The Joint Planning and Development 

Office’s “National Aviation Safety Strategic Plan” which defines national goals, objectives, and strategies 

for aviation safety improvements cites the improvement of vehicle systems health management as one of its 

recommended research strategies. (Ref. 2) The National Institute of Aerospace’s “Aviation Plan for 

American Leadership” report (Ref. 3) which identifies research and technology challenges for improving 

aviation safety recommends research in vehicle “health reliability and management”. Because of this well 

documented need for IVHM research, NASA initiated the IVHM Project. 

NASA’s IVHM Project conducts research to develop validated tools and technologies for automated 

detection, diagnosis, and prognosis that enable mitigation of adverse events during flight. (Ref. 4) 

Adverse events include those that arise from system, subsystem, or component failures, faults, and 

malfunctions due to damage, degradation, or environmental hazards that occur during flight. Determining 

the causal factors and adverse events that drive the need for IVHM technologies will assist in the 

formulation of research requirements. With limited funding available for IVHM research, it is important 

to identify those research areas that will have the most impact in addressing IVHM related causal factors 

and adverse events. The purpose of this study was to review statistical data to interpret and extract 

information about causal factors in aircraft incidents and accidents which are related to key research areas 

in the IVHM Project.

Technical Approach 

Two separate analyses are presented in this paper. The first analysis examines the publicly available 

National Transportation Safety Board (NTSB) and Federal Aviation Administration (FAA) accident and 

incident data. The second analysis is an examination of the Aviation Safety Reporting System (ASRS) 

incident reports. All of these data sources can be accessed using the Aviation Safety Information Analysis 

and Sharing (ASIAS) System. (Ref. 5) The focus of both analyses was the determination of the causal 

factors of incidents and accidents associated with failures and/or malfunctions associated with the various 

systems and/or components of commercial aircraft. 

In these analyses, “commercial” is defined per the FAA’s Federal Aviation Regulation (FAR) 121, 

Scheduled Part 135, and Non-Scheduled Part 135 flight operations (Ref. 6). Part 121 operations applies to 

major airlines and cargo carriers that fly large transport-category aircraft while part 135 applies to 

commercial aircraft air carriers commonly referred to as commuter airlines. Prior to March 1997, Part 121 

operations included aircraft with 30 or more seats. In March 1997, the definition of Part 121 operations 

changed and now includes those aircraft with ten or more seats. Scheduled operation refers to “any 

common carriage passenger-carrying operation for compensation or hire conducted by an air carrier or 

commercial operator for which the certificate holder or its representative offers in advance the departure 

location, departure time, and arrival location. A non-scheduled operation refers to “any operation for 

compensation or hire in which the departure time, departure location, and arrival location are specifically 

negotiated with the customer”. 

Non-impact fires were included as a type of malfunction, even when the cause of the fire was not 

specified. 

 
NASA/TM—2011-217023 3 

The safety risk is based on both accidents and incidents. Accidents and incidents have been defined 

per the NTSB definition as follows: (Ref. 7) 

Accident—An occurrence associated with the operation of an aircraft, which takes place between the time 

any person boards the aircraft with the intention of flight and all such persons have disembarked, and in 

which any person suffers death or serious injury, or in which the aircraft receives substantial damage. 

Incident—An occurrence other than an accident, associated with the operation of an aircraft, which 

affects or could affect the safety of operations. 

NTSB and FAA Accident/Incident Data Analyses 

These analyses looked at the safety risk associated with failures or malfunctions of various systems or 

components of commercial aircraft during the period 1988 to 2003. The source for accident data was the 

NTSB Aviation Accident and Incident Data System, while the source for incident data was the FAA’s 

Accident/Incident Data System (AIDS). Although both databases contain accident and incident data, the 

FAA has primary investigative responsibility for incidents and the NTSB is the authority for accident 

investigation. The NTSB database contains information collected during an NTSB investigation of an 

accident or incident involving civil aircraft within the United States, its territories and possessions, and in 

international waters. AIDS contains data records for general aviation and commercial air carrier incidents 

since 1978. The information contained in AIDS is gathered from several sources including incident 

reports on FAA Form 8020-5. Data for total flight hours per year were obtained from tables published by 

the NTSB, which are based on data from the FAA. The abbreviation SCFM will be used throughout this 

paper to mean System/Component Failure/Malfunctions. 

TABLE 1.—SUMMARY OF SCFM EVENTS BY OPERATION CATEGORY 

Type of events Operation 

Part 121 Scheduled Part 135 Non-Scheduled 

Part 135 

Part 121 and 135 

combined 

Total flight hours 232,868,640 25,050,928 46,350,000 304,269,568 

Total accidents 600 213 1070 1883 

Accidents with SCFM 109 (18%) 33 (16%) 228 (21%) 370 (20%) 

SCFM accidents 

per million flight hours 

0.47 1.32 4.92 1.22 

Fatal accidents 60 (10%) 49 (23%) 278 (26%) 387 (21%) 

Fatal accidents with 

SCFM 

16 (27%) 5 (10%) 47 (17%) 68 (18%) 

Total fatalities 2151 328 664 3143 

Fatalities in accidents with 

SCFM 

777 (36%) 52 (16%) 109 (16%) 938 (30%) 

Total incidents 7497 2218 2081 11,796 

Incidents with SCFM 4957 (66%) 1557 (70%) 1218 (58%) 7,732 (66%) 

SCFM incidents 

per million flight hours 

21.29 62.15 26.28 25.4 

A summary of the SCFM events can be found in Table 1. For the three operational categories 

examined, between 16 percent and 21 percent of commercial accidents during the 1988-2003 period 

involved a SCFM. Scheduled Part 135 accidents had the lowest proportion of accidents (16 percent), fatal 

accidents (10 percent) and total fatalities (328) associated with SCFM. In Part 121 flights, 18 percent of 

the accidents, 27 percent of the fatal accidents and 36 percent of fatalities were associated with SCFM. In 

Non-Scheduled Part 135 flights, 21 percent of the accidents, 17 percent of the fatal accidents and 

16 percent of the fatalities were associated with SCFM. There is at least one fatality in 18 percent of all 

SCFM accidents. 
NASA/TM—2011-217023 4 

Between 58 and 70 percent of all incidents were caused by SCFM of system or component. Despite 

having the lowest percentage of SCFM accidents among the three flight operation categories, Scheduled 

Part 135 flights had the highest percentage of SCFM incidents. Non-Scheduled Part 135 flights had the 

highest percentage of accidents and the lowest percentage of incidents related to SCFM. 

In Part 121 flights, 21 SCFM occurred for each one million flight hours; the rate was even higher 

among part 135 flights. 

For each accident and incident, the system affected by the SCFM was determined (Tables 2 and 3). In 

some events multiple systems were affected, and in these cases the first system affected was selected. For 

example, if an electrical malfunction preceded an engine fire, that event was categorized under Electrical. 

A large percentage of accidents with SCFM occurred due to failures or malfunctions in the engine system 

(33 to 49 percent) and landing gear system (21 to 30 percent). A large percentage of incidents with SCFM 

occur due to failures in the engine system (28 to 31 percent) and landing gear system (20 to 46 percent). 

TABLE 2.—ACCIDENTS WITH A SYSTEM AFFECTED BY SCFM BY OPERATION CATEGORY 

System Operation category 

Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 

Part 121 and 135 

combined 

Total accidents 109 33 228 370 

Engine 36 (33%) 12 (36%) 111 (49%) 159 (43%) 

Landing gear 23 (21%) 10 (30%) 64 (28%) 97 (26%) 

Flight control 10 (9%) 3 (9%) 9 (4%) 22 (6%) 

Electrical 8 (7%) 1 (3%) 12 (5%) 21 (6%) 

Fuel 4 (4%) 3 (9%) 13 (6%) 20 (5%) 

Hydraulic 9 (8%) 2 (6%) 7 (3%) 18 (5%) 

Structure 5 (5%) 1 (3%) 7 (3%) 13 (4%) 

Other 8 (7%) 1 (3%) 4 (2%) 13 (4%) 

Instrumentation/ 

communication/ 

navigation 

5 (5%) 0 (0%) 0 (0%) 5 (1%) 

Unknown 1 (1%) 0 (0%) 1 (0%) 2 (0%) 

TABLE 3.—INCIDENTS WITH A SYSTEM AFFECTED BY SCFM BY OPERATION CATEGORY 

System Operation category 

Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 

Part 121 and 135 

combined 

Total incidents 4957 1557 1218 7732 

Engine 1384 (28%) 486 (31%) 349 (29%) 2219 (29%) 

Landing gear 990 (20%) 509 (33%) 558 (46%) 2057 (27%) 

Other 615 (12%) 135 (9%) 47 (4%) 797 (10%) 

Hydraulic 414 (8%) 57 (4%) 45 (4%) 516 (7%) 

Flight control 431 (9%) 43 (3%) 28 (2%) 502 (6%) 

Fuel 215 (4%) 80 (5%) 54 (4%) 349 (4%) 

Structure 214 (4%) 80 (5%) 49 (4.0%) 343 (4%) 

Comfort systems 246 (5%) 54 (4%) 20 (2%) 320 (4%) 

Electrical 191 (4%) 64 (4%) 47 (4%) 302 (4%) 

Pressurization 174 (4%) 15 (1%) 8 (1%) 197 (2%) 

Instrumentation/ 

communication/ 

navigation 

83 (2%) 34 (2%) 13 (1%) 130 (2%) 

 
NASA/TM—2011-217023 5 

The NTSB database includes causal factors for each accident. The SCFM accidents presented in 

Table 2 were further grouped into four system sub-categories: engine or fuel, flight control or structural, 

landing gear or hydraulic, and other. The most frequent causal factors of the SCFM accidents that are 

linked to these four system sub-categories are presented in Tables 4 though 6. The entire list of causal 

factors is too extensive for presentation in this paper. Some of the causal factors specify the problem with 

the component (corroded, fractured, separated, etc.) and others address errors by individuals (maintenance 

personnel) or groups of people (manufacturer, the company or operator) or regulatory deficiencies (the 

FAA). Most events have more than one causal factor. Each table includes the number of accidents within 

the particular group of systems; the percentages given are based on the number of accidents, not on the 

number of causal factors. The entire listing of causes and failures can be found in the NASA Technical 

Memorandum (TM): Causal Factors and Adverse Events of Aviation Accidents and Incidents Related to 

Integrated Vehicle Health Management (Ref. 8). 

Of all the engine or fuel SCFM (Table 4) in commercial aircraft, 38 percent were related to 

maintenance errors. Some part of the engine or fuel system was said to have failed in 35 percent of the 

accidents and fatigue was noted in 23 percent of the accidents. 

Maintenance errors were involved in 46 percent of flight control or structural SCFM in commercial 

aircraft accidents (Table 5). Component failure was cited in 29 percent of the accidents. In 23 percent of 

the accidents a component separated. 

TABLE 4.—THE MOST FREQUENT CAUSES OF ENGINE OR FUEL SCFM 

ACCIDENTS BY OPERATION CATEGORY 

Cause of failure/malfunction 

Operation category 

Part 121 Scheduled 

Part 135 

Non-Scheduled 

Part 135 

Part 121 and 

135 combined 

Total engine or fuel SCFM 

accidents 40 15 124 179 

Maintenance related 17 (42%) 3 (20%) 49 (40%) 69 (38%) 

Component failure 18 (45%) 5 (33%) 39 (31%) 62 (35%) 

Component fatigue 8 (20%) 3 (20%) 30 (24%) 41 (23%) 

Component separated 6 (15%) 3 (20%) 16 (13%) 25 (14%) 

Component fractured 3 (8%) 1 (7%) 16 (13%) 20 (11%) 

Manufacturing/Design 9 (22%) 3 (20%) 8 (6%) 20 (11%) 

Component disconnected 3 (6%) 1 (7%) 15 (12%) 19 (11%) 

Oil deprivation 1 (2%) 1 (7%) 13 (10%) 15 (8%) 

TABLE 5.—THE MOST FREQUENT CAUSES OF FLIGHT CONTROL OR STRUCTURAL SCFM 

EVENTS BY OPERATION CATEGORY 

Cause of failure/malfunction 

Operation category 

Part 121 Scheduled 

Part 135 

Non-Scheduled 

Part 135 

Part 121 and 

135 combined 

Total flight control or 

structural SCFM accidents 15 4 16 35 

Maintenance related 8 (53%) 2 (50%) 6 (38%) 16 (46%) 

Component failure 3 (20%) 2 (50%) 5 (31%) 10 (29%) 

Component separated 4 (27%) 1 (25%) 3 (19%) 8 (23%) 

Manufacturing/Design 6 (40%) 0 (0%) 1 (6%) 7 (20%) 

Component jammed 2 (13%) 1 (25%) 4 (25%) 7 (20%) 

Component inoperative 2 (13%) 0 (0%) 3 (19%) 5 (14%) 
NASA/TM—2011-217023 6 

Maintenance errors were involved in 28 percent of landing gear or hydraulic system SCFM 

commercial accidents (Table 6). A component was said to have failed in 48 percent of the accidents. A 

component showed fatigue in 18 percent of the accidents and there was a loss of hydraulic fluid in 

15 percent of the accidents. 

Table 7 shows the most frequent causes of SCFM accidents in the other category. Maintenance errors 

were cited in 32 percent of the accidents, electrical failure was involved in 17 percent of the accidents and 

15 percent of the accidents cited wire chafing and arcing as a cause. 

Of interest is that the most frequent causal factors cited were maintenance errors in 35 percent of the 

SCFM accidents, (Table 8), followed by component failure in 34 percent of the accidents, and component 

fatigue in 17 percent of accidents. 

TABLE 6.—THE MOST FREQUENT CAUSES OF LANDING GEAR OR HYDRAULIC SCFM 

EVENTS BY OPERATION CATEGORY 

Cause of failure/Malfunction 

Operation category 

Part 121 Scheduled Part 135 

NonScheduled 

Part 135 

Part 121 and 

135 Combined 

Total landing gear or Hydraulic 

System SCFM accidents 32 12 71 115 

Component failure 18 (56%) 3 (25%) 34 (48%) 55 (48%) 

Maintenance related 8 (25%) 4 (33%) 20 (28%) 32 (28%) 

Component fatigue 7 (22%) 2 (17%) 12 (17%) 21 (18%) 

Hydraulic fluid loss 8 (25%) 3 (25%) 6 (8%) 17 (15%) 

TABLE 7.—THE MOST FREQUENT CAUSES OF OTHER* SCFM EVENTS BY OPERATION CATEGORY 

Cause of failure/Malfunction 

Operation category 

Part 121 Scheduled Part 

135 

Non-Scheduled 

Part 135 

Part 121 and 

135 Combined 

Total other* SCFM accidents 22 2 17 41 

Maintenance related 9 (41%) 1 (50%) 3 (18%) 13 (32%) 

Electrical failure 1 (4%) 0 (0%) 6 (35%) 7 (17%) 

Wiring chafed/arcing 3 (14%) 1 (50%) 2 (12%) 6 (15%) 

*Other includes Electrical, Instrumentation/Communication/Navigation, Anti-ice/De-ice system, APU, Cargo 

Fire, Galley, Heating, Oxygen, Pressurization, Warning Systems, Vacuum Pump and Unknown 

TABLE 8.—THE MOST FREQUENT CAUSES OF SCFM BY OPERATION CATEGORY 

Cause of failure/Malfunction 

Operation category 

Part 121 Scheduled 

Part 135 

Non-Scheduled 

Part 135 

Part 121 and 

135 combined 

Total SCFM accidents 109 (29%) 33 (9%) 228 (62%) 370 

Maintenance related 42 (32%) 10 (8%) 78 (60%) 130 (35%) 

Component failure 39 (31%) 10 (8%) 78 (61%) 127 (34%) 

Component fatigue 15 (24%) 5 (8%) 42 (68%) 62 (17%) 
NASA/TM—2011-217023 7 

Further analysis of SCFM accidents compared the severity in the four system categories. Two types 

of severity were analyzed: fatalities and aircraft damage. Table 9 compares the four system groups’ fatal 

accidents and fatality rates. Table 10 compares the four system groups’ aircraft damage sustained as a 

result of the accident. Although the Landing Gear or Hydraulic System category has 115 total accidents, 

only one was a fatal accident with five fatalities. In contrast, the Engine or Fuel System category has 179 

total accidents of which 44 were fatal accidents (25 percent) with 276 fatalities. The Flight Control or 

Structure Systems category has 35 accidents, yet twelve were fatal accidents (34 percent) with 297 

fatalities. Accidents involving SCFM of the Engine or Fuel System or the Flight Control or Structure 

Systems were more likely to result in destroyed aircraft (27 and 29 percent) than the Landing Gear or 

Hydraulics System Group Category (1 percent). Even though Flight Control or Structure SCFM accidents 

were less frequent than Landing Gear or Hydraulic System SCFM, the outcomes were far worse. 

The consequence of the SCFM in each of the four system groups is shown in Table 11. In Part 121 

and Scheduled Part 135 accidents, the flight control or structural SCFM were the most likely group to 

result in in-flight loss of control. Landing gear or hydraulic SCFM were the most likely type to occur with 

the aircraft on the ground, regardless of operation category. With an engine or fuel system SCFM, Part 

121 flights were most likely to make an uneventful landing, while Part 135 flights were most likely to 

make a complicated landing. 

TABLE 9.—ACCIDENT FATALITY CHARACTERISTICS BY SCFM SYSTEM GROUP AND 

BY OPERATION CATEGORY 

System group Fatality 

characteristics 

Operation 

Part 121 Scheduled 

Part 135 

NonScheduled 

Part 135 

Part 121 and 

135 combined 

Engine or fuel system Total accidents 40 15 124 179 

 Fatal accidents 4 (10%) 3 (20%) 37 (30%) 44 (25%) 

 Total fatalities 151 33 92 276 

Flight control or structure Total accidents 15 4 16 35 

 Fatal accidents 7 (47%) 1 (25%) 4 (25%) 12 (34%) 

 Total fatalities 279 14 4 297 

Landing gear or Hydraulic Total accidents 32 12 71 115 

 Fatal accidents 0 (0%) 1 (8%) 0 (0%) 1 (1%) 

 Total fatalities 0 5 0 5 

Instrument/Communication/ 

Navigation, Electrical, Other, 

Unknown 

Total accidents 22 2 17 41 

 Fatal accidents 5 (23%) 0 (0%) 6 (35%) 11 (27%) 

 Total fatalities 347 0 13 360 

 
NASA/TM—2011-217023 8 

TABLE 10.—ACCIDENT AIRCRAFT DAMAGE SEVERITY BY SCFM SYSTEM GROUP 

AND BY OPERATION CATEGORY 

System group Aircraft damage Operation 

Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 

Part 121 and 

135 combined 

Engine or fuel system Total accidents 40 15 124 179 

 Destroyed 5 (12.5%) 3 (20.0%) 41 (33.1%) 49 (27%) 

 Substantial damage 29 (72.5%) 11 (73.3%) 83 (66.9%) 123 (69%) 

 Minor damage 1 (2.5%) 1 (6.7%) 0 2 (1%) 

 No damage 5 (12.5%) 0 0 5 (3%) 

Flight control or structure Total accidents 15 4 16 35 

 Destroyed 5 (33.3%) 1 (25.0%) 4 (25.0%) 10 (29%) 

 Substantial damage 10 (67.7%) 2 (50.0%) 12 (75.0%) 24 (68%) 

 Minor damage 0 1 (25.0%) 0 1 (3%) 

 No damage 0 0 0 0 (0%) 

Landing gear or hydraulics Total accidents 32 12 71 115 

 Destroyed 0 1 (8.3%) 0 1 (1%) 

 Substantial damage 25 (78.1%) 11 (91.7%) 71 (100%) 107 (93%) 

 Minor damage 4 (12.5%) 0 0 4 (3%) 

 No damage 3 (9.4%) 0 0 3 (3%) 

Electrical, instrumentation, 

communication, navigation, 

other, unknown 

Total accidents 22 2 17 41 

 Destroyed 7 (31.8%) 0 6 (35.3%) 13 (32%) 

 Substantial damage 4 (18.2%) 2 (100%) 11 (64.7%) 17 (41%) 

 Minor damage 4 (18.2%) 0 0 4 (10%) 

 No damage 7 (31.8%) 0 0 7 (17%) 
NASA/TM—2011-217023 9 

TABLE 11.—CONSEQUENCE OF SCFM BY SYSTEM GROUP AND BY OPERATION CATEGORY 

System group Consequence of 

event 

Operation 

Part 121 Scheduled 

Part 135 

Non-scheduled 

Part 135 

Part 121 and 135 

combined 

Engine or fuel system Total accidents 40 15 124 179 

 On ground at 

time of event 

11 (28%) 2 (13%) 4 (3%) 17 (9%) 

 Uneventful landing 18 (45%) 1 (7%) 7 (6%) 26 (14%) 

 In-flight loss 

of control 

3 (8%) 2 (13%) 17 (14%) 22 (12%) 

 Complicated landing 8 (20%) 10 (67%) 96 (77%) 114 (64%) 

Flight control or 

structure 

Total accidents 15 4 16 35 

 On ground at time of 

event 

1 (7%) 0 1 (6%) 2 (6%) 

 Uneventful landing 5 (33%) 2 (50%) 3 (19%) 10 (29%) 

 In-flight loss of 

control 

5 (33%) 1 (25%) 3 (19%) 9 (26%) 

 Complicated landing 4 (27%) 1 (25%) 9 (56%) 14 (40%) 

Landing gear or 

hydraulics 

Total accidents 32 12 71 115 

 On ground at 

time of event 

20 (62%) 4 (33%) 21 (30%) 45 (39%) 

 Uneventful landing 0 1 (8%) 0 1 (1%) 

 In-flight loss 

of control 

1 (3%) 1 (8%) 0 2 (2%) 

 Complicated landing 11 (34%) 6 (50%) 50 (70%) 67 (58%) 

Electrical, 

instrumentation, 

communication, 

navigation, other, 

unknown 

Total accidents 22 2 17 41 

 On ground at time of 

event 

7 (32%) 0 1 (6%) 8 (20%) 

 Uneventful landing 9 (41%) 0 3 (18%) 12 (29%) 

 In-flight loss of 

control 

4 (18%) 0 6 (35%) 10 (24%) 

 Complicated landing 2 (9%) 2 (100%) 7 (41%) 11 (27%) 

Aviation Safety Reporting System Incident Analysis 

The Aviation Safety Reporting System (ASRS) is a voluntary, non-punitive, self reporting system 

administered by NASA Ames Research Center that includes incident reports submitted by members of the 

flight crew and other people working in the aviation industry. The ASRS reports do not represent an 

unbiased sample of aviation incidents, and the results presented here should not be considered statistically 

representative, but rather informational in nature. Data used in this analysis are for the period January 

1993 through March 2008. While the ASRS online database includes incidents starting in 1988, 

information on the FAR Part Flight Operations is available only beginning in 1993. Since other flight 

operations, such as Part 91 (general aviation), may provide substantially different data compared with 

Parts 121 and 135, it was decided to use only those years for which the FAR Part Flight Operations are 

known. During this time period there were 60,380 incident reports for Part 121 operation and 6,151 

incident reports for Part 135 operations resulting in a total of 66,531 reports for commercial aircraft. Each 
NASA/TM—2011-217023 10 

ASRS incident report lists the primary problem (or cause), and, if applicable, the component involved. 

While this categorization is performed by the experts at ASRS, the analysis presented in this paper further 

categorized those components into groups based on aircraft subsystems. 

ASRS identifies the most significant factor of the incident and includes it under the category “Primary 

Problem.” Of the 13,390 incident reports listed as having “Aircraft” as the primary problem or cause, 

12,395 can be attributed to “Equipment Problems” as shown in Table 12. During some incidents, multiple 

components failed in succession. Separately and combined, equipment problems account for 

approximately 93 percent of incidents whose primary factor was “Aircraft” for both FAR Parts 121 and 

135. Subcategories from within this primary problem are presented in Table 13. 

To provide an alternative approach to research, the SCFMs were further grouped by aircraft system. 

Then the components were ranked in order of frequency within the new subcategories. It must be noted 

than some incidents had more than one type of aircraft system failure, therefore the total of the Aircraft 

System SCFMs is actually greater than the Equipment Problem total shown in Table 12. Shown in 

Table 13, the top four systems cause 65 percent of all aircraft equipment failures during incidents. Those 

systems are Avionics, Propulsions Systems, Landing Gear, and Environmental Controls System. The top 

eight systems cause 88 percent of all aircraft SCFM during incidents. The top eight systems are expanded 

to include Control Surfaces, Structures, Electrical Systems, and the Hydraulic System. 

TABLE 12.—SYSTEM AFFECTED BY SCFM BY OPERATION CATEGORY 

Subcategory Incident frequency of operation 

Part 121 Part 135 Part 121 and 135 combined 

Equipment problem 11268 1127 12395 

Non-adherence 164 31 195 

Airspace violation 5 0 5 

Altitude deviation 203 11 214 

Cabin event 44 1 45 

Conflict 77 10 87 

Excursion 2 1 3 

Ground encounter 4 0 4 

Incursion 2 1 3 

Inflight encounter 62 9 71 

Maintenance problem 15 0 15 

Other anomaly 325 20 345 

Other spatial deviation 8 0 8 

Total 12179 1211 13390 

TABLE 13.—FREQUENCIES OF SCFM GROUPED BY SYSTEM 

Aircraft system Frequency of failure/ 

malfunction 

Avionics 3208 

Propulsion system 2424 

Landing gear 1378 

Environmental control system 1247 

Control surfaces 996 

Electrical 669 

Hydraulics 657 

Structures 605 

Fuel System 278 

F & E- furnishings and 

equipment 

263 

Oil system 246 

Brakes 196 

Anti-Icing 110 

Miscellaneous 438 

Total 12715 
NASA/TM—2011-217023 11 

Avionics 

While hardware features have extensive background research and testing of failures, avionics failures 

may be harder to predict and test. Information given by United Airlines in reference to Boeing 777 

aircraft indicates that health monitoring significantly reduces mechanical problems, but increases software 

problems (Ref. 9). More research is needed to insure that mechanical problems are not replaced by 

software problems. Because of the extremely high frequency of failures for avionics, along with the 

complexity of the system, further subcategories were developed for this study. 

Avionics failures were sorted into the subcategories in Table 14 and the distribution of failures is 

illuminating. While some subcategories, like Weather Systems, are negligibly small, others are very 

significant. Monitoring mainly includes indicators of health of individual systems such as landing gear or 

engine temperature, and it is nearly twice as large as any other subcategory. Included in Table 15 are the 

most frequent specific component failures of the avionics system. These failures account for 62 percent of 

all avionics failures. 

TABLE 14.—FREQUENCY OF SCFM 

FOR AVIONICS SUBCATEGORY 

Avionics 

subcategories 

Frequency of 

SCFM 

Monitoring 1174 

Navigation system 561 

Air flight control 451 

Communications 344 

Aircraft 

management 

337 

Collision 

avoidance system 

309 

Weather systems 32 

Total 3208 

TABLE 15.—FREQUENCY OF SPECIFIC AVIONICS COMPONENT SCFM 

Component Subcategory Frequency of SCFM 

FMS/FMC Navigation 267 

Autopilot Air flight control 241 

Indicating and warning - landing gear Monitoring 142 

GPWS Collision avoidance systems 120 

VHF Communications 103 

Traffic Collision Avoidance System (TCAS) Collision avoidance systems 96 

Fire/Overheat warning Aircraft management 95 

ILS/VOR Navigation 94 

Cargo compartment fire/Overheat warning Monitoring 86 

Door warning system Aircraft management 83 

Fuel quantity-pressure indication Monitoring 81 

Transponder Communications 79 

Power plant fire/Overheat warning Monitoring 77 

Auto throttle/Speed control Monitoring 72 

Air/Ground communication Communications 68 

Oil pressure indication Monitoring 65 

Air data computer Aircraft management 57 

TCAS equipment Collision avoidance systems 55 

INS (Inertial navigation system) Air flight control 54 

Altimeter Monitoring 52 

Total 1987 

 
NASA/TM—2011-217023 12 

Propulsion Systems 

The propulsion systems category was also large and complex, so subcategories were developed to ease 

the analysis of its SCFMs. The Unspecified Engine subcategory contains the “turbine engine” and “engine” 

components illustrating the lack of uniformity of information detail provided in the ASRS incident reports. 

Some reports contain a great deal of detail, while others are very nonspecific. Many of the SCFMs of the 

propulsion system stated no more detail than “engine failure.” Table 16 shows the frequency of the 

propulsion sub-category SCFMs. Included in Table 17 are the most frequent specific component failures of 

the Propulsion System. These failures account for 60 percent of all Propulsion System failures. The two 

components with the greatest number of failures are the “Engine” and “Turbine Engine” components, which 

are fairly vague categories. The rest of the propulsion failures were actually remarkably specific and diverse, 

so unlike avionics, individual components did not have high rates of failure. Without “engine” and “turbine 

engine,” most of the propulsion components do not fail a significant amount of times. Specific engine 

components failures are not always clearly reported in ASRS. 

Landing Gear 

The landing gear system also contributed to a significant number of failures. Its component problems 

were less varied than those of avionics or propulsion. The most problematic component was the gearextend/retract mechanism followed by the main gear tires. There were several other important 

components that bear further consideration in Table 18. These failures account for 75 percent of all 

landing gear failures. 

TABLE 16.—FREQUENCY OF SCFM FOR 

PROPULSION SYSTEMS SUBCATEGORY 

Propulsion subcategory Frequency of 

failure/ 

malfunction 

Unspecified engine 1011 

Power plant 376 

Auxiliary systems 329 

Propeller engine system 199 

Compressor 135 

Turbine 129 

Exhaust/Nozzle 86 

Nacelle/Cowling 67 

Turbofan system 57 

Engine starting 33 

Combustor 2 

Total 2424 

TABLE 17.—FREQUENCY OF SPECIFIC PROPULSION SYSTEM SCFM 

Component Subcategory Frequency of failure/ 

malfunction 

Turbine engine Unspecified engine 752 

Engine Unspecified engine 259 

Power plant lubrication system Power plant 91 

Compressor Compressor 73 

Throttle/Power level Power plant 69 

Power plant fuel control Power plant 55 

Circuit breaker/Fuse/ 

Thermocouple 

Power plant 54 

Cowling Nacelle/Cowling 50 

Turbine assembly Turbine 48 

Total 1451 
NASA/TM—2011-217023 13 

TABLE 18.—FREQUENCY OF SPECIFIC LANDING GEAR SYSTEM SCFM 

Component Frequency of failure/malfunction 

Gear extend/Retract mechanism 174 

Main gear tire 165 

Nose gear 128 

Landing gear indicating system 98 

Antiskid system 90 

Nosewheel steering 90 

Leading edge slat 77 

Generator drive 76 

Main gear 68 

Main gear door 58 

Total 1024 

TABLE 19.—FREQUENCY OF SPECIFIC ENVIRONMENTAL CONTROLS SCFM 

Component Frequency of failure/malfunction 

Pressurization system 351 

Air conditioning and pressurization 192 

Pressurization control system 162 

Air conditioning distribution system 130 

Aircraft cooling system 76 

AC generator/Alternator 71 

AC generation 68 

Total 1050 

Environmental Controls 

The environmental control system had the fourth highest impact on the incidents reported from 1993 

to 2008. Like the landing gear system, the environmental control system was less varied. A few 

components contributed to most of the total of 1247 SCFM. The pressurization system, air conditioning 

and pressurization components accounted for a large portion of the SCFM. The top failures in Table 19 

account for 84 percent of environmental controls failures.

Results/Key Findings 

NSTB Accident/FAA Incident Data Analyses 

Between 1988 and 2003, twenty percent of all U.S. commercial aircraft accidents involved SCFM, 

and 18 percent of those accidents included at least one fatality. In addition, 66 percent of incidents during 

the same time period consisted of a SCFM. 

Of the 370 accidents affected by SCFM, 48 percent involved the engine or fuel systems, 31 percent 

involved the landing gear or hydraulic systems, 9 percent involve flight control or structural systems, and 

11 percent involved other aircraft systems. A total of 35 percent of all SCFM accidents had been caused 

by maintenance errors. The next most frequent causes of SCFM accidents in the research time period 

were component failure, 34 percent, and component fatigue, 17 percent. 

Aircraft destruction followed SCFM in twenty percent accidents. One possible contributing factor is 

that in-flight loss of control followed only about 12 percent of the SCFM. Among Part 121 accidents, 

65 percent of the SCFM either occurred while the aircraft was on the ground or resulted in an uneventful 

landing, whereas 69 percent of the Part 135 SCFM resulted in a complicated landing. 

In general, SCFM of either the landing gear or hydraulic systems result in less severe outcomes 

(fewer fatalities and less aircraft destruction) than other systems. This may be in part because these SCFM 

were the most likely type to occur while the aircraft was on the ground. Similarly, SCFM of either the 

structure or flight control systems result in more severe outcomes, perhaps because these were more likely 

to lead to in-flight loss of control. 
NASA/TM—2011-217023 14 

ASRS Incident Data Analysis 

Of the 66,531 commercial incident reports contained in the ASRS system for the time period 1993 to 

March 2008, 20 percent or 13,390 incidents were grouped in the “Aircraft” Primary Problem category. 

During some incidents, multiple components failed in succession. Separately and combined, equipment 

problems (12, 395 incidents) accounted for approximately 93 percent of incidents whose primary factor 

was “Aircraft” for both FAR Parts 121 and 135. The most frequent systems cited in the equipment 

problems subcategory were: avionics (26 percent), propulsion systems (20 percent), landing gear 

(11 percent), and environmental control systems (10 percent). 

Of Avionics systems SCFM, the most common subsystem cited was the monitoring subcategory with 

1174 SCFM. Monitoring includes indicators of the health of individual systems and components such as 

the landing gear or engine temperature. Avionics and software failures are among the most frequent 

factors in incidents reported to ASRS, validating the importance of the performance, robustness, and 

reliability of software used in IVHM. Unfortunately, often the propulsion system SCFM were not clearly 

defined in the reports. The most frequently cited propulsion system component to have a SCFM was 

“turbine engine”. 

References 

1. Steering Committee for the Decadal Survey of Civil Aeronautics, National Research Council, 

Decadal Survey of Civil Aeronautics: Foundations for the Future, The National Academies Press, 

Washington D.C., 2006. 

2. The Joint Planning and Development Office, National Aviation Safety Strategic Plan, V8.0, 2008. 

3. The National Institute of Aerospace, Aviation Plan for American Leadership, 2006 Periodicals 

4. Srivastava, A., Mah, R., and Meyer, C., Integrated Vehicle Health Management Project Technical 

Plan, Version 2.02, National Aeronautics and Space Administration December 8, 2008. 

http://www.aeronautics.nasa.gov/nra_pdf/ivhm_tech_plan_c1.pdf. Accessed July 20, 2009 

5. Federal Aviation Administration Aviation Safety Information Analysis Sharing (ASIAS) System, 

http://asias.faa.gov. Accessed September 28, 2008. 

6. National Transportation Safety Board. Annual Review of Aircraft Accident Data US Air Carrier 

Operations, Calendar Year 1999, NTSB/ARC-02/03, PB2002-109241, November 13, 2002, page 1. 

http://www.ntsb.gov/publictn/2002/arc0203.pdf. Accessed Aug 11, 2009 

7. National Transportation Safety Board. “Government Information Locator Service (GILS): Aviation 

Accident Synopses World Wide Web Page.” GILS: Aviation Accident Synopses, November 18, 2002. 

http://ntsb.gov/Info/gils/gilssyn.htm. Accessed July 30, 2009. 

8. Reveley, M.S., Briggs, J.L, Evans, J.K., Jones, S.M., Kurtoglu, T., Leone, K., Sandifer, C, “Causal 

Factors and Adverse Events of Aviation and Incidents Related to Integrated Health Management,” 

NASA TM submitted for publication, 2009. 

9. Zuniga, Fanny Allison, Douglas C. Maclise, Dennis J. Romano, Nicholas N. Jize, Philip F. Wysocki, 

and David P. Lawrence. “Integrated Systems Health Management for Exploration Systems.” AIAA, 

1st Space Exploration Conference: Continuing the Voyage of Discovery, 30 Jan. 2005, Orlando, 

Florida. American Institute of Aeronautics and Astronautics. AIAA. 12 Aug. 2008. 

<http://www.aiaa.org/content.cfm?pageid=406>able=paper&gid=30833>. 
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An Examination of Commercial Aviation Accidents and Incidents Related to Integrated 

Vehicle Health Management 

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14. ABSTRACT

The Integrated Vehicle Health Management (IVHM) Project is one of the four projects within the National Aeronautics and Space 

Administration’s (NASA) Aviation Safety Program (AvSafe). The IVHM Project conducts research to develop validated tools and 

technologies for automated detection, diagnosis, and prognosis that enable mitigation of adverse events during flight. Adverse events 

include those that arise from system, subsystem, or component failure, faults, and malfunctions due to damage, degradation, or 

environmental hazards that occur during flight. Determining the causal factors and adverse events related to IVHM technologies will help in 

the formulation of research requirements and establish a list of example adverse conditions against which IVHM technologies can be 

evaluated. This paper documents the results of an examination of the most recent statistical/prognostic accident and incident data that is 

available from the Aviation Safety Information Analysis and Sharing (ASIAS) System to determine the causal factors of system/component 

failures and/or malfunctions in U.S. commercial aviation accidents and incidents.

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Aircraft safety 

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