Mary S. Reveley and Jeffrey L. Briggs

Glenn Research Center, Cleveland, Ohio

Joni K. Evans

ATK, Hampton, Virginia

Carl E. Sandifer

Glenn Research Center, Cleveland, Ohio

Sharon Monica Jones

Langley Research Center, Hampton, Virginia

Causal Factors and Adverse Conditions of

Aviation Accidents and Incidents Related

to Integrated Resilient Aircraft Control

NASA/TM—2010-216261

November 2010
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Mary S. Reveley and Jeffrey L. Briggs

Glenn Research Center, Cleveland, Ohio

Joni K. Evans

ATK, Hampton, Virginia

Carl E. Sandifer

Glenn Research Center, Cleveland, Ohio

Sharon Monica Jones

Langley Research Center, Hampton, Virginia

Causal Factors and Adverse Conditions of

Aviation Accidents and Incidents Related

to Integrated Resilient Aircraft Control

NASA/TM—2010-216261

November 2010

National Aeronautics and

Space Administration

Glenn Research Center

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either expressed or implied, by the National Aeronautics and 

Space Administration.
NASA/TM—2010-216261 iii 

Contents 

Summary ....................................................................................................................................................... 1

1.0 Introduction ........................................................................................................................................... 2

1.1 Purpose of Study........................................................................................................................... 2

1.2 Overview of Study Contents ........................................................................................................ 2

2.0 NASA Analysis of National Transportation Safety Board and Federal Aviation 

Administration Accident and Incident Data ......................................................................................... 2

2.1 Types of Loss of Control Events .................................................................................................. 7

2.2 Causes of Loss of Control, Secondary to System/Component Failure/Malfunction (SCFM) .... 11

2.3 Causes of Loss of Control, Secondary to Aircraft Damage ........................................................ 13

2.4 Causes of Control Upset ............................................................................................................. 14

2.5 Accident and Incident Data Analyses Conclusions .................................................................... 23

3.0 NASA Analyses of Aviation Safety Reporting System (ASRS) Incident Data.................................. 24

3.1 Introduction ................................................................................................................................ 24

3.2 Primary Problems in Loss of Control Incidents ......................................................................... 25

3.3 Most Frequently Cited Aircraft Systems in Loss of Control Incidents ...................................... 27

3.3.1 Landing Gear ................................................................................................................ 27

3.3.2 Brakes ........................................................................................................................... 29

3.3.3 Air Flight Control ......................................................................................................... 29

3.3.4 Propulsion Systems ....................................................................................................... 29

3.3.5 Control Surfaces ........................................................................................................... 29

3.4 Aviation Safety Reporting System Data Analysis Conclusions ................................................. 31

4.0 Adverse Conditions Table .................................................................................................................. 32

5.0 Discussion and Conclusions ............................................................................................................... 33

References ................................................................................................................................................... 34

Appendix A.—Acronyms ........................................................................................................................... 35

Appendix B.—In-Flight Loss of Control Accidents in Part 121 and Scheduled Part 135 Flight 

Operations ........................................................................................................................................... 37

NASA/TM—2010-216261 1 

Causal Factors and Adverse Conditions of Aviation Accidents and 

Incidents Related to Integrated Resilient Aircraft Control 

Mary S. Reveley and Jeffrey L. Briggs 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Joni K. Evans 

ATK 

Hampton, Virginia 23681 

Carl E. Sandifer 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Sharon Monica Jones 

National Aeronautics and Space Administration 

Langley Research Center 

Hampton, Virginia 23681 

Summary 

The causal factors of accidents from the National Transportation Safety Board (NTSB) database and 

incidents from the Federal Aviation Administration (FAA) database associated with loss of control (LOC) 

were examined for four types of operations (i.e., Federal Aviation Regulation Part 121, Part 135 

Scheduled, Part 135 Nonscheduled, and Part 91) for the years 1988 to 2004. In-flight LOC is a serious 

aviation problem. Well over half of the LOC accidents included at least one fatality (80 percent in 

Part 121), and roughly half of all aviation fatalities in the studied time period occurred in conjunction with 

LOC. 

In about 30 percent of Part 121 LOC accidents, the LOC was secondary to a system/component 

failure/malfunction (SCFM), compared with 8 to 12 percent of the accidents in other flight operation 

categories. The most frequently cited components and systems were the engine and flight control system. 

Twenty-three percent of the Part 121 LOC accidents were secondary to aircraft damage (most often due to 

fire), compared with 3 to 8 percent of the accidents in other flight operation categories. As a result, for 

roughly 35 percent of the LOC accidents in Part 121, aircraft control was not possible, compared with 6 to 

9 percent of the accidents in other flight operation categories. In flights other than Part 121, 25 to 40 

percent of the LOC was caused by inadequate airspeed leading to an inadvertent stall. Icing (both 

preflight and in-flight) and adverse winds were the primary cause of a large number of accidents. Other 

frequently cited causes for LOC are inadequate preflight, improper planning or decisions, and flying in 

obscuration or at night. The accidents and incidents were divided into three groups: LOC secondary to 

SCFM, LOC secondary to aircraft damage, and LOC due to control upset. 

The Aviation Safety Reporting System (ASRS) incident database was examined for three types of 

operation (Part 121, Part 135, and Part 91) for the years January 1993 to May 2008. From the analysis of 

this data, five aircraft systems have been identified as critical in regards to the frequency of incidents they 

represent. These systems are landing gear, brakes, air flight control, propulsion systems, and control 

surfaces. 
NASA/TM—2010-216261 2 

Most accidents and incidents have more than one causal factor cited by accident and incident 

investigators. 

An adverse events table was updated to provide focus to the technology validation strategy of the 

Integrated Resilient Aircraft Control (IRAC) Project. The table contains three types of adverse conditions: 

failure, damage, and upset. Thirteen different adverse condition subtypes were gleaned from the ASRS, 

the FAA Accident and Incident database, and the NTSB database. The severity and frequency of the 

damage conditions, initial test conditions, and milestones references are also provided. 

1.0 Introduction 

1.1 Purpose of Study 

NASA’s Integrated Resilient Aircraft Control (IRAC) Project is one of four projects within the 

Agency’s Aviation Safety Program (AvSafe) in the Aeronautics Research Mission Directorate (ARMD). 

The IRAC Project, which was updated April 13, 2007, conducts research to advance the state of the 

aircraft flight control to provide onboard control resilience for ensuring safe flight in the presence of 

adverse conditions (faults, damage, and upsets). Adverse events include loss of control (LOC) caused by 

environmental factors and actuator and sensor faults or failures, and will expand toward more 

complicated damage conditions (Ref. 1). 

The purpose of this study is to review statistical data and literature from academia, industry, and other 

Government agencies to interpret and extract information about causal factors for aircraft incidents and 

accidents that are related to the key research areas in IRAC. From this information, a list of potential 

adverse conditions and initial test conditions was established against which IRAC technologies can be 

evaluated (Ref. 1). Outcomes of this study include 

(1) A report that documents causal factors related to LOC gleaned from the analysis of the incidents 

and accidents related to IRAC. 

(2) A list of potential adverse conditions and initial test conditions against which flight, propulsion, 

and mission adaptive control approaches can be evaluated. 

The results of this study are considered a “waypoint” to establish future requirements for the project. 

1.2 Overview of Study Contents 

The expected outcomes for this study are addressed in sequential order. Outcome 1 is addressed in the 

NASA Analyses of National Transportation Safety Board (NTSB) Accident Data and Federal Aviation 

Administration (FAA) Incident Data as well as the NASA Analysis of Aviation Safety Reporting System 

(ASRS) Incident Data sections. Outcome 2 is the focus of the adverse conditions table section. Finally, 

discussion and the conclusions that have been drawn are provided. Appendix A lists the acronyms used in 

this report and their definitions, and Appendix B presents accidents for Part 121 and Scheduled Part 135 

flight operations that were determined to include in-flight LOC. 

2.0 NASA Analysis of National Transportation Safety Board and Federal 

Aviation Administration Accident and Incident Data 

The first expected outcome of this study is a report that documents the results of an examination of 

the most recent statistical and prognostic incident and accident data that is available to determine the 

causal factors related to LOC in U.S. commercial aviation accidents and incidents. This section contains 

the results of two separate statistical analyses that have been conducted by NASA to address this expected 

outcome. The first statistical analysis examined publicly available NTSB and FAA accident and incident 
NASA/TM—2010-216261 3 

data. A second statistical analysis was conducted using ASRS reports as the data source. All of these data 

sources can be accessed using the FAA’s Aviation Safety Information Analysis and Sharing (ASIAS) 

System (Ref. 2).

In-flight loss of aircraft control contributed to less than 20 percent of U.S. aviation accidents between 

1988 and 2004, but these accidents were responsible for more than half of the aviation fatalities during 

that time period. The current analysis has examined the causes of LOC events across a 17-yr span (1988 

to 2004) within the four categories of operation (Part 121, Scheduled Part 135, Nonscheduled Part 135, 

and Part 91). In this analysis, “commercial” is defined as Part 121, Scheduled Part 135, and Nonscheduled 

Part 135 flights. Part 121 operations applies to major airlines and cargo carriers that fly large transportcategory aircraft, and 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 10 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” (Ref. 

3). A nonscheduled 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.” Part 91, also 

known as general aviation, refers to all aviation other than commercial (Ref. 3). The word “event” is used 

here to encompass both accidents and incidents that are defined as follows (Ref. 4): 

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. 

The source for accident data is the NTSB Aviation Accident and Incident Data System, and the 

source for incident data is the FAA’s Accident/Incident Data System. Although both databases contain 

both accident and incident data, the FAA has primary investigative responsibility for incidents and the 

NTSB is the authority for accident investigation. Appendix B lists all the accidents for Part 121 and 

Scheduled Part 135 flight operations that were determined to include in-flight LOC in this study. 

The accident data have previously been classified using the Commercial Aviation Safety Team/ 

International Civil Aviation Organization (CAST/ICAO) Common Taxonomy Team (CICTT) accident 

category taxonomy (Ref. 5). This taxonomy delineates LOC as being in-flight or on-ground. In-flight 

LOC was subsequently partitioned by general phase of flight (i.e., takeoff, approach/landing, or en route). 

Selection of LOC events from the incident data was accomplished using two methods. First, if in the 

data record, “FLTCNTL/AIR” was a primary or secondary cause, and second, if the words “control,” 

“stall,” or “spin” were found in the narrative text. All of these records were reviewed; more than 

95 percent were excluded. In a large percentage of the records with the word “control” in the text, that 

word was used in the context of specific flight controls, traffic control, or command of the aircraft (e.g., 

“the first officer was at the controls”). These were excluded, as were those involving on-ground or 

ground-effect LOC. Ground-effect LOC includes runway contact events (hard or bounced landings or 

wing, propeller, or tail strikes), undershoots, overruns, and runway excursions, and collisions with runway 

signs, markers, or lights. Essentially, the incidents included in this analysis occurred after flight was 

established in the takeoff climb and prior to the landing flare or during an aborted landing. This is 

consistent with the accident taxonomy. 
NASA/TM—2010-216261 4 

A summary of the number of LOC events can be found in Table 1. Data for total flight hours were 

obtained from tables published by the NTSB, which they based on data from the FAA. In Part 121 flights, 

LOC contributed to only 4 percent of all accidents, but 34 percent of fatal accidents, and 55 percent of all 

fatalities. Eighty percent of the LOC accidents were fatal. Fifty-seven percent of Part 91 fatalities (and 

55 percent of fatal accidents) were attributed to loss of aircraft control, and 53 percent of the LOC 

accidents were fatal. Among Part 135 accidents, LOC accounted for 15 to 18 percent of all accidents, 39 

to 44 percent of fatal accidents, and 41 to 49 percent of all fatalities. Sixty to sixty-four percent of Part 

135 LOC accidents were fatal. 

TABLE 1.—SUMMARY OF LOSS OF CONTROL (LOC) EVENT CHARACTERISTICS BY OPERATION CATEGORY 

Type of events 

Operation category 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 91, 135, and 

121 combined 

Total flight hours 251,751,143 25,353,146 49,588,000 441,207,000 767,896,289 

Total accidents 630 217 1115 24,473 26,435 

LOC accidents 26 (4% of total 

accidents) 

32 (15% of total 

accidents) 

198 (18% of total 

accidents) 

4961 (20% of total 

accidents) 

5217 (20% of total 

accidents) 

LOC accidents 

per million flight 

hours 

0.10 1.26 4.03 11.24 6.79 

Fatal accidents 62 (10% of 

total accidents) 

49 (23% of total 

accidents) 

293 (26% of total 

accidents) 

4815 (20% of total 

accidents) 

5289 (20% of total 

accidents) 

Fatal LOC 

accidents 

21 (81% of 

LOC accidents) 

19 (59% of LOC 

accidents) 

128 (65% of LOC 

accidents) 

2635 (53% of 

LOC accidents) 

2803 (54% of 

LOC accidents) 

Total fatalities 2165 328 698 9146 12,337 

Fatalities in LOC 

accidents 

1186 (55%) 161 (49%) 285 (41%) 5178 (57%) 6810 (55%) 

Total incidents 7808 2234 2201 29,520 41,763 

LOC incidents 38 5 8 81 132 

LOC incidents per 

million flight 

hours 

0.151 0.197 0.161 0.18 0.17 

In-flight LOC was considered a factor in less than 0.5 percent of all incidents. Twenty-nine percent of 

the LOC incidents occurred in Part 121 flights, and 61 percent were in Part 91. Part 121 is the only flight 

category with more LOC incidents than accidents. Outside of transport category aircraft, LOC is likely to 

result in a level of aircraft damage that will cause the event to be considered an accident, rather than an 

incident. In most of these incidents, control of the aircraft was regained prior to a collision with terrain or 

objects. 

Since 1988, there have been no more than eight LOC events each year in Part 121 flights, and about 

60 percent of those were incidents (see Fig. 1). From 1997 to 2004, there were a total of 7 LOC accidents 

and 21 incidents. 

With the exception of 1992, there have been no more than five LOC events each year in Scheduled 

Part 135 flights, but about 82 percent of the events were accidents (see Fig. 2). Seventy percent of the 

events occurred prior to 1997. 
NASA/TM—2010-216261 5 

Figure 1.—Frequency of Part 121 loss of control events per year. 

Figure 2.—Frequency of Scheduled Part 135 loss of control events per year. 

Between 1988 and 2004, there were no more than 16 LOC events each year in Nonscheduled 

Part 135 flights (see Fig. 3). The number of events has been generally decreasing over time, with a slight 

bump in 2004. 

LOC events in Part 91 have declined dramatically from 1988 to 2004 (see Fig. 4), but there are still 

more than 200 events each year. Nearly all of the Part 91 LOC events are considered accidents. 
NASA/TM—2010-216261 6 

Figure 3.—Frequency of Nonscheduled Part 135 loss of control events per year. 

Figure 4.—Frequency of Part 91 loss of control events per year. 

Table 2 shows the delineation of in-flight LOC accidents according to the phase of flight in which 

control was lost. In Part 121, the largest percentage of LOC events occurred during approach and landing, 

but takeoff LOC was the deadliest. In Part 135, LOC was least likely to occur en route, although among 

Nonscheduled Part 135, when control was lost en route, it almost always resulted in fatalities. In Part 91, 

en-route LOC was both the most frequent and the most often fatal. 

TABLE 2.—FREQUENCY OF LOSS OF CONTROL ACCIDENTS 

BY PHASE OF FLIGHT AND BY OPERATION CATEGORY

Phase of flight

Operation category 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 91, 135, and 121 

combined 

Total accidents 26 32 198 4961 5217 

Takeoff 7 16 73 1542 1638 

Fatal takeoff 7 (100%) 7 (443.8%) 30 (41%) 526 (34%) 570 (35%) 

En route 8 6 56 1784 1854 

Fatal en route 5 (62%) 4 (67%) 52 (93%) 1459 (82%) 1520 (82%) 

Approach/landing 11 10 69 1635 1725 

Fatal approach/landing 9 (82%) 8 (80%) 46 (67%) 650 (40%) 713 (41%) 
NASA/TM—2010-216261 7 

2.1 Types of Loss of Control Events 

To facilitate the examination of causal factors in these LOC accidents, the accidents and incidents 

were divided into three groups, which are defined below. 

1. LOC secondary to system/component failure/malfunction (SCFM).—In each of these events, 

LOC occurred secondary to a failure/malfunction. In some of these events, it may have been 

possible for the flight crew to maintain control, but in others the LOC was unavoidable. 

2. LOC secondary to aircraft damage.—In these events, LOC was secondary to some type of 

aircraft damage, and this group is further subdivided into the following causes of damage: 

 Fire and/or explosion 

 Mid-air collision with another aircraft, bird, or skydiver 

 Weather-induced damage (from turbulence, hail, or lightning) 

 Pilot induced (most often exceeding the designed stress limits of the aircraft) 

3. Control upset.—These events are further subdivided according to coexisting situations. 

 Pilot induced.—Control was lost due to the actions or inaction of the pilot, without other 

preceding or concurrent events. 

 Low-altitude operations.—In these accidents, control was lost in conjunction with some 

type of low-level maneuvering (aerobatics, aerial application, banner towing, evasive 

maneuvers to avoid a collision, sightseeing, scud running, etc.). 

 Severe weather.—In these events, the LOC was secondary to an encounter with severe 

weather—icing, turbulence, thunderstorm, or wind shear—or to inadequate ice/frost/snow 

removal prior to takeoff. 

 Other events.—The other events include loss of engine power, pilot incapacitation, or 

inadequate preflight inspections that resulted in open doors, gust locks that were not removed, 

or compromised Pitot systems. 

Table 3 shows 31 percent of these accidents were precipitated by an SCFM, 23 percent by damage to 

the aircraft, while 46 percent followed an event that caused control upset. The one en-route LOC accident 

that is considered to be secondary to pilot-induced damage is the Belle Harbor, New York, crash in which 

the pilot inappropriately manipulated the rudder controls, leading to an overload failure of the vertical 

stabilizer. The one approach/landing LOC accident secondary to other events involved an inadequate 

preflight (open baggage door) and the subsequent failure to make a successful precautionary landing after 

takeoff. 

TABLE 3.—FREQUENCY OF PART 121 LOSS OF CONTROL (LOC) 

ACCIDENTS BY ADVERSE CONDITIONS AND BY PHASE OF FLIGHT 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing 

combined 

Total system/component failure/ 

malfunction 

2 (29%) 1 (12%) 5 (46%) 8 (31%) 

Damage, fire 1 2 2 5 

Damage, pilot 0 1 0 1 

Total damage 1 3 (38%) 2 (18%) 6 (23%) 

Control upset, pilot 2 2 1 5 

Control upset, severe weather 2 2 2 6 

Control upset, other events 0 0 1 1 

Total control upset 4 (57%) 4 (50%) 4 (36%) 12 (46%) 

Total 7 (100%) 8 (100%) 11 (100%) 26 (100%) 
NASA/TM—2010-216261 8 

Among Scheduled Part 135 accidents during 1988 to 2004, there were 16 events with LOC during 

takeoff climb, 6 events with en-route LOC, and 10 events with LOC during approach or landing. Table 4 

shows that 9 percent of these accidents were precipitated by an SCFM, 1 percent was attributed to 

damage, and 88 percent followed encounters with a control upset. Severe weather was a cause in 38 

percent of all the Scheduled Part 135 LOC accidents. The two cases of control upset due to other events 

during takeoff involved an unsecured door and wake turbulence. The LOC accident due to pilot-induced 

damage during approach/landing involved scraping the aircraft on the runway following a failure to 

extend the landing gear, with a stall during the improperly executed aborted landing. 

TABLE 4.—FREQUENCY OF SCHEDULED PART 135 LOSS OF CONTROL (LOC) 

ACCIDENTS BY ADVERSE CONDITIONS AND BY PHASE OF FLIGHT 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing 

combined 

Total system/component failure/ 

malfunction 

1 (6%) 1 (17%) 1 (10%) 3 (9%) 

Total damage, pilot 0 (0%) 0 (0%) 1 (10%) 1 (3%) 

Control upset, pilot 7 2 4 13 

Control upset, low-altitude maneuver 0 1 0 6 

Control upset, severe weather 6 2 4 12 (38%) 

Control upset, other events 2 0 0 2 

Total control upset 15 (94%) 5 (83%) 8 (80%) 28 (88%) 

Total 16 (100%) 6 (100%) 10 (100%) 32 (100%) 

Among Nonscheduled Part 135 accidents during 1988 to 2004, there were 73 events with LOC on 

takeoff climb, 56 events with en-route LOC, and 69 events with LOC during approach or landing. As 

shown in Table 5, 12 percent of these accidents were precipitated by an SCFM. Of the en-route LOC 

events, 23 percent followed some sort of aircraft damage, and 25 percent occurred while operating at low 

altitude. Approximately 22 percent of the LOC events followed encounters with severe weather. One of 

the takeoff LOC due to other events involved an open door, and the other two had a loss of engine power. 

Of the two en-route LOC due to other events, one followed pilot incapacitation, and the other had a loss 

of engine power. One of the landing LOC due to other events involved an inadequate preflight (engine 

cowl plugs not removed), another followed pilot incapacitation, and eight had loss of engine power. 

TABLE 5.—FREQUENCY OF NONSCHEDULED PART 135 LOSS OF CONTROL (LOC) 

ACCIDENTS BY ADVERSE CONDITIONS AND BY PHASE OF FLIGHT 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing combined 

Total system/component failure/ 

malfunction 

11 (15%) 5 (9%) 8 (12%) 24 (12%) 

Damage, fire 0 2 1 3 

Damage, collision 0 6 0 6 

Damage, weather 0 4 0 4 

Damage, pilot 1 1 0 3 

Total damage 1 (1%) 13 (23%) 1 (1%) 15 (8%) 

Control upset, pilot 45 (62%) 12 (21%) 29 (42%) 86 (43%) 

Control upset, low-altitude maneuver 0 14 (25%) 0 14 

Control upset, severe weather 13 10 21 (31%) 44 (22%) 

Control upset, other events 3 2 10 15 

Total control upset 61(81%) 38 (67%) 60 (87%) 159 (80%) 

Total 73 (100%) 56 (100%) 69 (100%) 198 (100%) 
NASA/TM—2010-216261 9 

Among Part 91 accidents during 1988 to 2004, there were 1542 events with LOC on takeoff climb, 

1784 events with en-route LOC, and 1635 events with LOC during approach or landing. As shown in 

Table 6, 8 percent of these accidents were precipitated by an SCFM, and 6 percent of them were 

secondary to aircraft damage. More than half were attributed to pilot error, while 7 percent followed an 

encounter with severe weather. Thirty-five percent of the en-route LOC accidents occurred while 

operating at low altitude. Thirty-three accidents had LOC secondary to pilot-induced damage. The two 

during takeoff followed a propeller strike shortly after liftoff and the nine during approach/landing 

followed failures to extend the landing gear. In the 22 en-route accidents, the pilot operated the aircraft in 

a manner that exceeded the designed stress limits. Thirty-nine of the 177 takeoff LOC accidents occurred 

due to other events involved an inadequate preflight (doors not secured, gust locks not removed, or Pitot 

tubes not cleared), 7 followed pilot incapacitation, 7 followed abrupt maneuvering, and 124 followed loss 

of engine power. Of the 106 en-route LOC accidents due to other events, 65 of these followed pilot 

incapacitation, 40 followed loss of engine power, and the final involved an inadequate preflight (open 

door). Of the 363 approach/landing LOC accidents due to other events, 316 followed loss of engine 

power, 19 followed pilot incapacitation, 14 involved inadequate preflight errors (relative to doors, fuel/oil 

caps, and Pitot systems), 9 involved evasive maneuvers, and the other 5 involved problems with banner 

towing equipment. 

TABLE 6.—FREQUENCY OF PART 91 LOSS OF CONTROL (LOC) ACCIDENTS BY PHASE OF 

FLIGHT AND ADVERSE CONDITIONS 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing combined 

Total system/component failure/ 

malfunction 

112 (7%) 114 (6%) 157 (10%) 383 (8%) 

Damage, fire 2 17 12 31 

Damage, collision 11 125 62 198 

Damage, weather 0 29 0 29 

Damage, pilot 2 22 9 33 

Total damage 15 (1%) 193 (11%) 83 (5%) 292 (6%) 

Control upset, pilot 1164 (76%) 572 (32%) 921 (56%) 2657 (53%) 

Control upset, low-altitude maneuver 0 620 0 620 

Control upset, severe weather 74 179 111 364 

Control upset, other events 177 106 363 646 

Total control upset 1415 1477 1395 4287 

Total 1542 (100%) 1784 (100%) 1635 (100%) 4961 (100%) 

Among Part 121 incidents during 1988 to 2004, there were 4 events with LOC during takeoff climb, 

25 events with en-route LOC, and 9 with LOC during approach or landing. As shown in Table 7, about 

79 percent of these events were precipitated by either a SCFM or damage to the aircraft, while 20 percent 

followed encounters with severe weather. The one approach/landing control upset incident that is 

considered to be due to other events involved wake turbulence. 

TABLE 7.—FREQUENCY OF PART 121 LOSS OF CONTROL (LOC) INCIDENTS BY PHASE OF 

FLIGHT AND ADVERSE CONDITIONS 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing combined 

Total system/component failure/ 

malfunction 

1 21 (84%) 6 (67%) 28 (58%) 

Control upset, pilot 1 0 0 1 

Control upset, severe weather 2 4 2 8 (20%) 

Control upset, other events 0 0 1 1 

Total control upset 3 4 3 10 (21%) 

Total 4 (100%) 25 (100%) 9 (100%) 48 (100%) 
NASA/TM—2010-216261 10 

Among Scheduled Part 135 incidents during 1988 to 2004, there was one event with LOC during 

takeoff climb, and four events with en-route LOC (see Table 8). The one control upset incident that is 

considered to be due to other events involved wake turbulence. 

TABLE 8.—FREQUENCY OF SCHEDULED PART 135 LOSS OF CONTROL (LOC) INCIDENTS BY PHASE OF 

FLIGHT AND ADVERSE CONDITIONS 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing combined 

Total system/component failure/ 

malfunction 

1 (100%) 2 (50%) 0 3 (60%) 

Control upset, severe weather 0 1 0 1 

Control upset, other events 0 1 0 1 

Total control upset 0 2 (100%) 0 2 (40%) 

Total 1 (100%) 4 (100%) 0 5 (100%) 

Among Nonscheduled Part 135 incidents during 1988 to 2004, there were two events with LOC 

during takeoff climb, and six events with en-route LOC. As shown in Table 9, 75 percent of 

these events were precipitated by an SCFM. 

TABLE 9.—FREQUENCY OF NONSCHEDULED PART 135 LOSS OF CONTROL (LOC) INCIDENTS BY PHASE OF 

FLIGHT AND ADVERSE CONDITIONS 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing combined 

Total system/component failure/ 

malfunction 

1 (50%) 5 (83%) 0 6 (75%) 

Control upset, pilot 1 0 0 1 

Control upset, severe weather 0 1 0 1 

Total control upset 1 (50%) 1 (17%) 0 2 (25%) 

Total 2 (00%) 6 (100%) 0 8 (100%) 

Among Part 91 incidents during 1988 to 2004, there were 18 events with LOC during takeoff climb, 

35 events with en-route LOC, and 28 events with LOC during approach or landing, as shown in Table 10. 

One-third of these events were precipitated by an SCFM, while 15 percent followed encounters with 

severe weather. Four of the six incidents that are considered to be due to other events involved a loss of 

engine power; the other two had inadequate preflights (an inspection panel came loose and a door 

opened). 

TABLE 10.—FREQUENCY OF PART 91 LOSS OF CONTROL (LOC) INCIDENTS BY PHASE OF 

FLIGHT AND ADVERSE CONDITIONS 

Adverse condition leading to LOC 

Phase of flight when LOC occurred 

Takeoff En route Approach/landing Takeoff, en route, and 

approach/landing combined 

Total system/component failure/ 

malfunction 

4 (22%) 19 (54%) 4 (14%) 27 (33%) 

Control upset, pilot 11 5 20 36 (44%) 

Control upset, severe weather 1 9 2 12 (15%) 

Control upset, other events 2 2 2 6 

Total control upset 14 (78%) 16 (46%) 24 (86%) 54 (67%) 

Total 18 (100%) 35 (100%) 28 (100%) 81 (100%) 
NASA/TM—2010-216261 11 

2.2 Causes of Loss of Control, Secondary to System/Component Failure/Malfunction 

(SCFM) 

For LOC accidents in which SCFM was a cause, Tables 11 to 14 give more detailed information as to 

the specific system that suffered the SCFM. Table 11 provides this information for all phases of flight 

combined, while Tables 12 through 14 breaks out this information into the three phases of flight looked at 

in this study: takeoff, en route, and approach/landing. 

As shown in Table 11, in Part 121, of the eight LOC accidents, 62 percent involved flight control 

systems. Of these Part 121 LOC accidents, aircraft control was not possible in five out of the eight 

accidents, improper procedures were used in one accident (landing gear malfunction), spatial 

disorientation occurred in another (navigation instrument malfunction), and the data record does not 

specify a cause for LOC in the other accident (a catastrophic and uncontained engine failure). In the 

NTSB data analysis, “flight controls” as a category of SCFM, refers to the entire flight control system, 

including ailerons, elevators, rudder, horizontal and vertical stabilizers, and the control stick or yoke. 

Most of these are failures of connections, cables, screws, and fatigue cracks. Failures of the autopilot and 

flight management computer are classified as being a part of the navigation system by the NTSB. 

In Scheduled Part 135 flights, three LOC accidents followed SCFMs. Aircraft control was not 

possible in two of these accidents, and in the third, the pilot did not follow the proper emergency 

procedure following an engine failure. 

TABLE 11.—SYSTEM/COMPONENT FAILURE/MALFUNCTION (SCFM) FREQUENCY IN 

LOSS OF CONTROL (LOC) ACCIDENTS BY SYSTEM AND OPERATION CATEGORY 

SCFM system 

Operation category 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 91, 135, 

and 121 

combined 

Anti-ice/de-ice 0 0 0 2 2 

Electrical 0 0 3 12 15 

Engine 1 1 (33%) 11 (46%) 146 (38%) 159 (38%) 

Flight control 5 (62%) 1 (33%) 2 78 (20%) 86 (21%) 

Fuel system 0 0 3 39 42 (10%) 

Heating 0 0 0 1 1 

Inst/com/nav 1 0 0 23 24 

Landing gear 1 0 0 6 7 

Oxygen 0 0 0 2 2 

Pitot heat 0 0 0 1 1 

Pressurization 0 0 1 2 3 

Propeller 0 1 (33%) 1 20 22 

Structure 0 0 1 30 31 

Vacuum pump 0 0 2 21 23 

Total 8 (100%) 3 (100%) 24 (100%) 383 (100%) 418 (100%) 

In Nonscheduled Part 135 flights, 24 LOC accidents followed SCFMs. Fourteen of these involved the 

engine or fuel system; in 12 of these, a loss of airspeed led to a stall, while for the other 2 accidents, the 

cause of the LOC was not specified. In six of the accidents, the NTSB ruled that the loss of aircraft 

control could not have been prevented, including one accident in which all persons onboard were 

incapacitated following decompression. In the remaining four accidents, the LOC was caused by spatial 

disorientation (two accidents, both vacuum pump failures), diverted attention because of the electrical 

failure during takeoff, and a stall (from ice buildup because the anti-ice system could not operate due to 

an electrical malfunction). 

In Part 91 flights, 383 LOC accidents followed SCFM, 185 involved the engine or fuel system, and 

78 involved flight control systems. The engine/fuel system and flight control systems accounted for 

69 percent of Part 91 LOC accidents. 

As shown in Table 12, of all LOC takeoff accidents following an SCFM, 40 percent followed an 

SCFM of the engine, while 33 percent followed an SCFM of flight control. In en-route LOC accidents, 
NASA/TM—2010-216261 12 

the most frequent SCFM systems were structures, flight control, and the engine, as shown in Table 13. 

During approach/landing LOC accidents, an engine SCFM preceded LOC in a majority of the accidents 

(Table 14). 

TABLE 12.—SYSTEM/COMPONENT FAILURE/MALFUNCTION (SCFM) FREQUENCY IN LOSS OF 

CONTROL (LOC) ACCIDENTS DURING TAKEOFF BY SYSTEM AND OPERATION CATEGORY 

SCFM system 

Operation category 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 91, 135, 

and 121 

combined 

Electrical 0 0 1 1 2 

Engine 0 1 (100%) 6 (54%) 43 (38%) 50 (40%) 

Flight control 2 (100%) 0 1 39 (35%) 42 (33%) 

Fuel system 0 0 2 12 14 

Inst/com/nav 0 0 0 1 1 

Landing gear 0 0 0 3 3 

Propeller 0 0 1 7 8 

Structure 0 0 0 6 6 

Total 2 (100%) 1 (100%) 11 (100%) 112 (100%) 126 (100%) 

TABLE 13.—SYSTEM/COMPONENT FAILURE/MALFUNCTION (SCFM) FREQUENCY IN LOSS OF CONTROL 

(LOC) ACCIDENTS WHILE EN ROUTE BY SYSTEM AND OPERATION CATEGORY

SCFM system 

Operation category 

Part 121 Scheduled Part 135 Nonscheduled 

Part 135 

Part 91 Part 91, 135, and 121 

combined 

Anti-ice/de-ice 0 0 0 1 1 

Electrical 0 0 1 6 7 

Engine 0 0 1 18 (16%) 19 (16%) 

Flight control 1 1 0 19 (17%) 21 (17%) 

Fuel system 0 0 0 6 6 

Inst/com/nav 0 0 0 16 (14%) 16 

Oxygen 0 0 0 2 2 

Pitot heat 0 0 0 1 1 

Pressurization 0 0 1 2 3 

Propeller 0 0 0 2 2 

Structure 0 0 1 21 (18%) 22 (18%) 

Vacuum pump 0 0 1 20 (18%) 21 

Total 1 (100%) 1 (100%) 5 (100%) 114 (100%) 121 (100%) 

TABLE 14.—SYSTEM/COMPONENT FAILURE/MALFUNCTION (SCFM) FREQUENCY IN LOSS OF CONTROL 

(LOC) ACCIDENTS DURING APPROACH/LANDING BY SYSTEM AND SYSTEM AND OPERATION CATEGORY 

SCFM system 

Operation category 

Part 121 Scheduled Part 135 Nonscheduled 

Part 135 

Part 91 Part 91, 135, and 121 

combined 

Anti-ice/de-ice 0 0 0 1 1 

Electrical 0 0 1 5 6 

Engine 1 0 4 85 (54%) 90 (53%) 

Flight control 2 0 1 20 23 

Fuel system 0 0 1 21 22 

Heating 0 0 0 1 1 

Inst/com/nav 1 0 0 6 7 

Landing gear 1 0 0 3 4 

Propeller 0 1 0 11 12 

Structure 0 0 0 3 3 

Vacuum pump 0 0 1 1 2 

Total 5 (100%) 1 (100%) 8 (100%) 157 (100%) 171 (100%) 
NASA/TM—2010-216261 13 

In LOC accidents following an SCFM, the most common primary causes of the LOC were 

“inadequate airspeed and/or stall/spin” and “control was not possible” (Table 15). In 80 percent of the 

SCFM accidents the LOC due to inadequate airspeed and/or spin/stall was as a result of an engine or fuel 

SCFM. 

TABLE 15.—FREQUENCY OF PRIMARY CAUSES OF PART 91 LOSS OF CONTROL (LOC) ACCIDENTS 

SECONDARY TO SYSTEM/COMPONENT FAILURE/MALFUNCTION BY SYSTEM 

Primary cause of LOC 

System 

Engine or fuel Flight control Other systems All systems 

combined 

Control not possible 5 62 (80%) 40 (33%) 107 (28%) 

Inadequate airspeed and/or stall/spin 149 (80%) 6 26 (22%) 181 (47%) 

Spatial disorientation 0 0 26 (22%) 26 

Pilot incapacitation 7 0 4 11 

Diverted attention 5 1 5 11 

Procedural or decision errors 8 0 4 12 

Not specified 11 9 15 35 

Total 185 (100%) 78 (100%) 120 (100%) 383 (100%) 

2.3 Causes of Loss of Control, Secondary to Aircraft Damage 

In Part 121, six LOC accidents followed aircraft damage. Aircraft control was not possible in four of 

these accidents (67 percent), and the data record does not specify a cause for LOC in the other two 

accidents that occurred outside the United States in the Dominican Republic and Ecuador. 

In Scheduled Part 135, one LOC accident followed aircraft damage. As mentioned above, the pilot 

failed to extend the landing gear and scraped the aircraft along the runway, then stalled the aircraft during 

the improperly executed aborted landing. 

In Nonscheduled Part 135, 15 LOC accidents followed aircraft damage. Airspeed was not maintained 

after an engine fire, resulting in a stall. In two other fires, the data record does not specify the cause for 

the LOC. Six of the accidents were mid-air collisions with other aircraft, after which aircraft control was 

not possible. Four in-flight breakups occurred after encounters with severe weather, leaving the aircraft 

uncontrollable. Another in-flight breakup was caused by the pilot flying with excessive airspeed, after 

which aircraft control was not possible. In the final accident, the pilot did not maintain proper alignment 

on the gravel bar he was using as a runway and damaged the stabilator by hitting a tree. The aircraft then 

stalled into the river. Of these accidents, LOC was caused because aircraft control not possible in 11 of 

the accidents, stall in 2, and unknown causes in the final 2 accidents. 

In Part 91, 291 LOC accidents followed aircraft damage and the NTSB ruled that aircraft control was 

not possible in 251 of these (86 percent). Table 16 lists the causes of LOC in four groups defined by the 

cause of the damage. 

TABLE 16.—FREQUENCY OF PRIMARY CAUSES OF PART 91 LOSS OF CONTROL (LOC) 

ACCIDENTS SECONDARY TO AIRCRAFT DAMAGE 

Primary cause of LOC 

Cause of aircraft damage 

Fire Collision Weather Pilot induced All causes 

combined 

Control not possible 18 (58%) 181 (91%) 29 (100%) 23 (70%) 251 (86%) 

Inadequate airspeed 

and/or stall/spin 

2 2 0 6 10 

Spatial disorientation 1 0 0 0 1 

Pilot incapacitation or 

impairment 

2 7 0 0 9 

Diverted attention 2 7 0 9 

Not specified 6 1 0 4 11 

Total 31 (100%) 198 (100%) 29 (100%) 33 (100%) 291 (100%) 
NASA/TM—2010-216261 14 

2.4 Causes of Control Upset 

Control upset is defined here as being caused by pilot error and/or LOC due to occurrences that 

cannot be regulated via aircraft technology. In Part 121, 12 accidents were classified as “control upset.” 

Three accidents followed in-flight encounters with icing, and two followed inadequate ice and/or frost 

removal before takeoff. Each of the following primary causes was responsible for one of the seven 

remaining accidents: inaccurate weight and/or balance (cargo loaded improperly), improper use of 

controls (flaps and slats not properly configured prior to takeoff), inadvertent control interference 

(deactivation of autopilot and movement of control column), an inadvertent stall from inadequate airspeed 

during level-off, a wind shear encounter during a missed approach, impairment of the flight crew due to 

fatigue, and an improperly secured cargo door. 

In Scheduled Part 135, 28 accidents were classified as “control upset.” Six accidents were caused by 

inadequate ice and/or frost removal prior to takeoff. The primary causes of the other nine takeoff control 

upset accidents were three stalls from inadequate airspeed, one encounter with wake turbulence, one 

encounter with adverse winds (downdrafts), one premature liftoff from a wet runway, one improper 

decision to delay aborting the takeoff after the aircraft would not climb, one spatial disorientation during a 

low-visibility takeoff at night, and one inadequate preflight (improperly secured cargo door). Of the five 

en-route control upset accidents, one has no determined cause, one followed an encounter with icing, one 

followed an encounter with a thunderstorm, one was caused by spatial disorientation (flat lighting and 

snow-covered terrain), and the other was caused by an inadvertent stall from inadequate airspeed. There 

were eight control upset accidents during approach/landing. Two followed icing encounters, one followed 

an encounter with a thunderstorm, three were due to stalls, one was caused by the pilot’s failure to follow 

approved procedures for a single-engine approach, and one was caused by the improper use of controls 

(inadvertent activation of power levers). 

The primary causes of the control upset accidents in Nonscheduled Part 135 and Part 91 are listed in 

Tables 17, 18, and 19. In some cases the data record does not include any causes or factors (mostly for 

accidents occurring outside the United States). In other cases the only cause listed is a “failure to maintain 

aircraft control.” This cause has no more meaning than “unknown,” but when the aircraft is not equipped 

with a cockpit recorder, when the pilot was not in communication with a tower at the time of the accident, 

and when there are no witnesses to the accident, a more detailed accident cause is understandably difficult 

to determine. 

During takeoff, control upset in Nonscheduled Part 135 was most likely to be caused by adverse 

winds or inadequate ice/frost removal, and in Part 91, 40 percent of the control upset was caused by 

inadequate airspeed leading to a stall. En route, the most common cause of control upset in either 

category of operation was a stall. The next most common causes of control upset were icing (Part 135 

Nonscheduled) and visual flight rules (VFR) into instrument meteorological conditions (IMC) (Part 91). 

During approach and landing, the most common cause of control upset in either category of operation was 

also a stall. The next most common causes were icing (Part 135 Nonscheduled) and adverse wind 

conditions (Part 91). 

TABLE 17.—FREQUENCY OF PRIMARY CAUSES OF NONSCHEDULED PART 135 AND PART 91 LOSS OF CONTROL 

(LOC) ACCIDENTS DURING TAKEOFF FOLLOWING CONTROL UPSET 

Primary cause of LOC Operation 

Nonscheduled Part 135 Part 91 

Inadequate airspeed and/or stall 5 575 (40.6%) 

Inadequate ice/frost removal 13 (21.3%) 33 

Weather (WX), icing 0 4 

WX, thunderstorm 0 4 

WX, wind shear 0 21 

WX, adverse winds 18 (30%) 200 (14%) 

WX, obscuration 0 13 

Visual flight rules into instrument meteorological conditions 0 31 

 
NASA/TM—2010-216261 15 

TABLE 17.—Concluded. 

Primary cause of LOC Operation 

Nonscheduled Part 135 Part 91 

Spatial disorientation 1 37 

Diverted attention 1 11 

Wake turbulence 0 7 

Inadequate preflight 2 48 

Incorrect weight/balance 8 64 

Incorrect or unsuitable runway 4 17 

All available runway not used 0 3 

Improper/premature liftoff 0 105 

Improper handling 0 5 

Improper use of controls 2 51 

Procedural or decision error 0 30 

Pilot incapacitation 0 7 

Pilot impairment 0 16 

Control interference 0 8 

Passenger interference 0 7 

Aircraft performance capability exceeded 0 28 

Lack of experience 0 16 

Aircraft control not maintained 5 58 

Unknown 2 16 

Total 61 (100%) 1415 (100%) 

TABLE 18.—FREQUENCY OF PRIMARY CAUSES OF NONSCHEDULED PART 135 AND PART 91 LOSS OF CONTROL 

(LOC) ACCIDENTS EN ROUTE FOLLOWING CONTROL UPSET 

Primary cause of LOC 

Operation 

Nonscheduled Part 135 Part 91 

Inadequate airspeed and/or stall 10 (26%) 530 (36%) 

Weather (WX), icing 5 (13%) 63 

WX, thunderstorm 3 68 

WX, turbulence 2 29 

WX, wind shear 0 8 

WX, adverse winds 0 33 

WX, obscuration 0 50 

WX, blizzard 1 0 

Visual flight rules into instrument meteorological conditions 2 211 (14%) 

Spatial disorientation 3 95 

Diverted attention 0 6 

Wake turbulence 1 3 

Inadequate preflight 0 3 

Incorrect weight/balance 0 7 

Improper use of controls 0 12 

Low-altitude maneuvering 3 83 

Pilot incapacitation 0 63 

Pilot impairment 1 55 

Procedural/decision error 0 5 

Control interference 0 9 

Passenger interference 1 11 

Aircraft performance capability exceeded 0 2 

Lack of experience 0 14 

Aircraft control not maintained 1 72 

Unknown 5 45 

Total 38 (100%) 1477 (100%) 
NASA/TM—2010-216261 16 

TABLE 19.—FREQUENCY OF PRIMARY CAUSES OF NONSCHEDULED PART 135 AND PART 91 LOSS OF CONTROL 

(LOC) ACCIDENTS DURING APPROACH OR LANDING FOLLOWING CONTROL UPSET 

Primary cause of LOC Operation 

Nonscheduled Part 135 Part 91 

Inadequate airspeed and/or stall 21 (35%) 675 (48.4%) 

Weather (WX), icing 11 (18%) 38 

WX, thunderstorm 3 4 

WX, wind shear 4 29 

WX, turbulence 0 2 

WX, adverse winds 3 267 (19%) 

WX, obscuration 6 20 

Visual flight rules into instrument meteorological conditions 0 18 

Spatial disorientation 1 52 

Diverted attention 0 8 

Wake turbulence 1 27 

Inadequate preflight 0 13 

Incorrect weight/balance 3 2 

Improper use of controls 2 54 

Improper handling 0 4 

Incorrect or unsuitable runway 0 1 

Procedural/decision error 0 33 

Pilot incapacitation 0 18 

Pilot impairment 1 12 

Control interference 1 0 

Passenger interference 0 2 

Aircraft performance capability exceeded 0 1 

Lack of experience 0 19 

Aircraft control not maintained 2 85 

Unknown 1 11 

Total 60 (100%) 1395 (100%) 

The incident data, unfortunately, seldom includes enough details to determine a cause for the LOC 

incidents. Thus no attempt is made to summarize causal factor data for the incidents. 

The accident data record often includes four or more causes, factors, or findings. In addition to the 

primary cause detailed above, Tables 20 to 22 list all of the recorded causes, factors, and findings relative 

to control upset for these accidents for takeoff, en route, and approach or landing phases of flight. 

Percentages are based on the total number of accidents in each operation category, not on the total number 

of causes, factors, or findings. For example, 51 percent of the Part 91 accidents with control upset during 

takeoff (1415 total accidents) list an inadvertent stall, spin, or mush as a cause/factor/finding in the data 

record. 

TABLE 20.—FREQUENCY OF ALL CAUSES/FACTORS/FINDINGS OF LOSS OF CONTROL UPSET 

ACCIDENTS DURING TAKEOFF FOLLOWING CONTROL UPSET BY OPERATION CATEGORY 

Causes/factors/findings 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 91, 135, and 

121 combined 

Total number of accidents 4 15 61 1415 1495 

Inadvertent stall/spin/mush 2 (50%) 5 (33%) 13 (21%) 722 (51%) 742 (50%) 

Inadequate airspeed 1 (25%) 3 (20%) 15 (25%) 548 (39%) 567 (38%) 

Weather (WX), winds 0 1 19 (31%) 344 (24%) 364 (24%) 

Aircraft control not maintained 0 2 12 (20%) 302 (21%) 316 (21%) 

Inadequate preflight 2 (50%) 3 (20%) 17 (28%) 211 233 (16%) 

Inadequate experience 0 0 3 162 165 

Improper (premature) liftoff 0 1 0 158 159 

High-density altitude 0 0 1 158 159 

Improper or inadequate compensation 

for wind conditions 

0 1 8 132 141 

Improper use of controls 2 (50%) 1 3 131 137 

Incorrect weight/balance 1 (25%) 3 9 119 132 

Improper climb 0 1 2 88 91 
NASA/TM—2010-216261 17 

TABLE 20.—Continued. 

Causes/factors/findings 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 91, 135, and 

121 combined 

WX, obscuration 0 1 4 73 78 

Wrong or unsuitable runway 0 0 4 74 78 

Light (night) 0 1 6 67 74 

Abort delayed or not performed 0 1 2 69 72 

Improper planning/decision 0 1 7 58 66 

Abrupt, evasive, or improperly executed 

maneuver 

0 0 1 62 63 

Spatial disorientation 0 0 1 58 59 

Inadequate WX evaluation 0 0 6 52 58 

Incapacitation or impairment 0 1 0 53 54 

Inadequate ice/frost removal 2 (50%) 6 (40%) 9 36 53 

Diverted attention 0 0 3 46 49 

Aircraft performance capability 

exceeded 

0 0 2 47 49 

Procedures and/or directives not 

followed 

2 (50%) 2 4 65 73 

Improper or inadequate supervision by 

certified flight instructor or pilot not 

flying 

0 0 0 38 38 

WX, icing 2 (50%) 2 8 25 37 

Improper aircraft handling 0 0 0 35 35 

Improper or inadequate remedial action 0 0 1 33 34 

Climb not possible 0 0 4 27 31 

Complacency, overconfidence, or 

ostentatious display 

1 (25%) 0 0 30 31 

Visual flight rules into instrument 

meteorological conditions 

0 0 0 31 31 

Runway condition 0 2 3 26 31 

WX, turbulence 0 0 1 29 30 

Checklist not followed 0 0 1 28 29 

WX, snow or rain 1 2 4 19 26 

Aircraft control not possible 1 (25.0%) 2 0 20 23 

Flight into adverse WX 0 0 1 22 23 

WX, wind shear 0 0 0 23 23 

Improper alignment 0 0 1 19 20 

Lack of certification or qualification 0 0 0 20 20 

No causes/factors/findings 0 0 3 16 19 

Company and/or operator deficiency 3 (75%) 3 (20%) 7 6 19 

Operation with known aircraft 

deficiency 

0 0 0 19 19 

Anxiety/depression/panic/pressure 0 1 1 16 18 

Improper altitude 0 1 0 16 17 

All available runway not used 0 0 0 15 15 

Improper or inadequate training 1 (25%) 0 1 13 15 

FAA deficiency 4 (100%) 2 1 7 14 

WX, thunderstorm or microburst 0 0 1 11 12 

Banner or glider tow flight 0 0 0 10 10 

Control interference 0 0 0 10 10 

Poor judgment 0 0 0 8 8 

Manufacturing deficiency 1 (25%) 1 0 6 8 

Fatigue 0 0 0 7 7 

Cargo shifted 0 0 2 5 7 

Wake turbulence 0 1 0 6 7 

Passenger interference 0 0 0 7 7 

Gust lock not removed 0 0 0 5 5 

Light (dusk or dawn) 0 0 0 5 5 

WX, high temperatures 0 0 0 4 4 

 
NASA/TM—2010-216261 18 

TABLE 20.—Concluded. 

Causes/factors/findings 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 91, 135, and 

121 combined 

Improper or inadequate air traffic 

control service 

0 0 0 3 3 

Improper or inadequate communication 

with air traffic control 

0 0 0 2 2 

Light (sun glare) 0 0 0 2 2 

Visual/aural perception 0 0 0 2 2 

Light (flat) 0 0 1 0 1 

Inadequate crew coordination 1 (25%) 0 0 0 1 

TABLE 21.—FREQUENCY OF ALL CAUSES/FACTORS/FINDINGS OF LOSS OF CONTROL (LOC) ACCIDENTS 

EN ROUTE FOLLOWING CONTROL UPSET BY OPERATION CATEGORY 

Causes/factors/findings 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, 

and 91 combined 

Total number of accidents 4 5 38 1477 1524 

Inadvertent stall/spin/mush 2 (50%) 2 (40%) 12 (32%) 644 (44%) 660 (43%) 

Aircraft control not maintained 1 (25%) 2 (40%) 12 (32%) 478 (32%) 493 (32%) 

Inadequate airspeed 2 (50%) 2 (40%) 13 (34.2%) 451 

(30.5%) 

468 (31%) 

Weather (WX), obscuration 0 0 9 (24%) 360 (24%) 369 (24%) 

Abrupt, evasive, or improperly 

executed maneuver 

0 0 7 295 (20%) 302 (20%) 

Spatial disorientation 0 1 (20%) 4 269 274 

Inadequate experience 0 0 4 246 250 

Visual flight rules into instrument 

meteorological conditions 

0 1 (20%) 3 223 227 

Light (night) 0 0 8 (21%) 183 191 

Flight into adverse weather 0 0 4 181 185 

Improper planning/decision 0 1 (20%) 6 168 175 

Incapacitation or impairment 0 0 5 163 168 

WX, snow or rain 0 2 (40%) 4 131 137 

Inadequate WX evaluation 0 0 5 125 130 

WX, icing 2 (50%) 2 (40%) 7 96 107 

WX, turbulence 0 1 (20%) 2 106 109 

WX, winds 0 0 3 102 105 

WX, thunderstorm/microburst 0 1 (20%) 4 83 88 

Inadequate preflight 0 0 1 73 74 

Improper or inadequate remedial 

action 

1 (25%) 0 1 68 70 

Complacency or overconfidence 0 0 0 64 64 

Improper or inadequate aircraft 

handling 

0 0 1 58 59 

High-density altitude 0 0 1 53 54 

No causes/factors/findings 1 (20%) 4 44 49 

Procedures/directives not followed 0 0 2 47 49 

Improper use of controls 2 (50%) 1 (20%) 44 47 

Incorrect weight/balance 0 0 0 44 44 

Improper or inadequate supervision 

by certified flight instructor or pilot 

not flying 

0 0 0 40 40 

Improper altitude 0 0 1 36 37 

Diverted attention 0 1 (20%) 35 36 

Anger/anxiety/depression/panic/ 

pressure 

0 0 2 34 36 

Poor judgment 0 0 0 31 31 

Lack of certification or qualification 0 0 0 29 29 

Ostentatious display 0 0 0 28 28 

 
NASA/TM—2010-216261 19 

TABLE 21.—Concluded. 

Causes/factors/findings 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, 

and 91 combined 

Aircraft control not possible 0 0 0 26 26 

Improper or inadequate training 0 0 2 21 23 

Fatigue 0 1 (20%) 1 19 21 

Improper or inadequate 

compensation for wind conditions 

0 0 0 18 18 

Banner or glider tow flight 0 0 0 18 18 

Lost and/or disoriented 0 0 0 18 18 

WX, wind shear 0 0 0 15 15 

Light (dusk or dawn) 0 0 0 13 13 

Operation with known aircraft 

deficiency 

0 0 0 12 12 

Control interference 1 (25%) 0 11 12 

Passenger interference 0 0 1 10 11 

FAA deficiency 1 (25%) 0 3 6 10 

Company/operator deficiency 0 0 2 7 9 

Visual/aural perception 0 0 0 8 8 

Aircraft performance capability 

exceeded 

0 0 0 8 8 

Pitot blockage 0 0 0 6 6 

Improper or inadequate air traffic 

control service 0 0 0 6 6 

WX information inaccurate or 

unavailable 0 0 0 5 5 

Manufacturing deficiency 1 (25%) 0 1 3 5 

Inadequate crew coordination 1 (25%) 1 (20%) 0 2 4 

Wake turbulence 0 0 1 3 4 

Climb not possible 0 0 0 3 3 

Improper alignment 0 0 0 2 2 

Improper climb 0 0 0 2 2 

Improper descent 0 0 0 1 1 

Light (flat) 0 1 (20%) 0 0 1 

Light (Sun glare) 0 0 0 1 1 

TABLE 22.—FREQUENCY OF ALL CAUSES/FACTORS/FINDINGS OF LOSS OF CONTROL (LOC) ACCIDENTS ON 

APPROACH/LANDING FOLLOWING CONTROL UPSET BY OPERATION CATEGORY 

Causes/factors/findings 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, 

and 91 combined 

All accidents 4 8 60 1395 1467 

Inadvertent stall/spin/mush 1 (25.0%) 5 (62.5%) 30 (50.0%) 716 (51.3%) 752 (51%) 

Inadequate airspeed 0 4 (50.0%) 23 (38%) 604 (43%) 631 (43%) 

Weather (WX), winds 0 0 9 (15%) 373 (27%) 382 (26%) 

Aircraft control not maintained 0 0 12 (20%) 363 (26%) 375 (26%) 

Inadequate experience 0 1 5 174 180 

Improper or inadequate compensation for 

wind conditions 

0 0 3 174 177 

Improper planning/decision 3 (75%) 4 (50%) 14 (23%) 128 149 

Improper use of controls 1 (25%) 1 4 137 143 

WX, obscuration 0 2 (25%) 15 (25%) 106 123 

Procedures/directives not followed 1 (25%) 2 (25%) 7 96 106 

Light (night) 0 1 7 86 94 

Abort delayed or not performed 0 1 4 89 94 

Abrupt, evasive, or improperly executed 

maneuver 

0 0 2 85 87 

Spatial disorientation 0 0 2 68 70 

WX, icing 1 (25%) 3 (38%) 15 (25%) 45 64 

 
NASA/TM—2010-216261 20 

Table 22.—Concluded. 

Causes/factors/findings 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, 

and 91 combined 

Improper or inadequate supervision by 

certified flight instructor or pilot not flying 

0 0 0 68 68 

Improper or inadequate remedial action 1 (25%) 0 5 56 62 

Incapacitation or impairment 0 0 1 61 62 

Inadequate preflight 1 (25%) 0 2 57 60 

Improper alignment 0 0 1 52 53 

Flight into adverse weather 0 1 9 42 52 

Inadequate weather evaluation 1 (25%) 0 4 47 52 

WX, turbulence 0 0 4 44 48 

WX, snow or rain 0 0 6 34 40 

Improper or inadequate aircraft handling 2 (50%) 1 1 35 39 

Diverted attention 0 0 1 33 34 

Improper altitude 0 0 2 32 34 

High-density altitude 0 0 1 32 33 

WX, wind shear 1 (25%) 0 5 30 36 

Wake turbulence 0 0 1 27 28 

Visual flight rules into instrument 

meteorological conditions 

0 0 1 23 24 

Improper glidepath 0 0 1 21 22 

Complacency or overconfidence 0 0 0 20 20 

Wrong or unsuitable runway 0 0 0 18 18 

Improper climb 0 0 1 16 17 

Aircraft control not possible 0 0 3 16 19 

WX, thunderstorm or microburst 1 (25%) 1 4 13 19 

Incorrect weight/balance 2 15 17 

Company/operator deficiency 2 (50%) 3 (38%) 8 4 17 

Operation with known aircraft deficiency 1 15 16 

Improper or inadequate training 1 (25%) 2 (25%) 2 11 16 

Improper or inadequate air traffic control 

service 

1 (25%) 1 12 15 

Lost or disoriented 0 0 0 14 14 

No causes/factors/findings 0 0 1 11 12 

FAA deficiency 2 (50%) 2 (25%) 0 7 11 

Poor judgment 1 (25%) 0 2 7 10 

Control interference 0 0 0 10 10 

Anxiety/depression/panic/pressure 0 0 0 9 9 

Fatigue 1 (25%) 0 2 5 8 

Aircraft performance capability exceeded 0 0 1 7 8 

Improper descent 0 0 0 6 6 

Lack of certification or qualification 0 0 0 5 5 

Banner tow flight 0 0 0 5 5 

Visual impairment (not physical) 0 0 0 5 5 

Manufacturing deficiency 2 (50%) 0 0 2 4 

Climb not possible 0 0 0 4 4 

Passenger interference 0 0 0 4 4 

Light (dusk or dawn) 0 0 1 3 4 

Weather information inaccurate or 

unavailable 

0 0 0 3 3 

Light (Sun glare) 0 0 0 3 3 

Visual/aural perception 0 0 0 3 3 

Pitot blockage 0 0 0 2 2 

Improper or inadequate communication 

with air traffic control 

0 0 1 1 2 

Cargo shifted 0 0 1 0 1 

WX, high temperatures 0 0 0 1 1 

Light (flat) 0 0 0 1 1 

 
NASA/TM—2010-216261 21 

Table 23 provides all of the recorded causes, factors and findings for all control upset accidents by 

operation category, while Table 24 provides only the primary causes for all the control upset accidents by 

operation category. 

TABLE 23.—FREQUENCY OF ALL CAUSES/FACTORS/FINDINGS OF ALL LOSS OF CONTROL (LOC) 

ACCIDENTS FOLLOWING CONTROL UPSET BY OPERATION CATEGORY 

Causes/factors/findings 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, 

and 91 

combined 

All accidents 13 27 159 4287 4486 

Inadvertent stall/spin/mush 5 (38%) 12 (44%) 55 (35%) 2082 (49%) 2154 (48%) 

Inadequate airspeed 3 (23%) 9 (33%) 51 (32%) 1603 (37%) 1666 (37%) 

Aircraft control not maintained 1 4 36 1143 (27%) 1184 (26%) 

Weather (WX), winds 0 1 31 819 851 

Abrupt, evasive, or improperly executed 

maneuver 0 0 12 582 595 

WX, obscuration 0 1 13 433 477 

Spatial disorientation 0 1 7 395 403 

Improper planning/decision 3 (23%) 6 27 354 390 

Inadequate preflight 3 (23%) 3 20 341 367 

Light (night) 0 2 21 336 359 

Improper or inadequate compensation for 

wind conditions 0 1 11 324 336 

Improper use of controls 5 (38%) 3 7 312 327 

Incapacitation or impairment 0 1 6 277 284 

Visual flight rules into instrument 

meteorological conditions 0 1 4 277 282 

Flight into adverse weather 0 1 14 245 260 

Inadequate weather evaluation 1 0 15 224 240 

Procedures/directives not followed 3 4 13 208 228 

WX, icing 5 7 30 166 208 

WX, snow or rain 1 4 14 184 203 

Incorrect weight/balance 1 3 11 176 191 

WX, turbulence 0 1 7 179 187 

Abort delayed or not performed 0 2 6 158 166 

Improper or inadequate remedial action 2 0 7 157 166 

High-density altitude 0 0 3 243 246 

Improper (premature) liftoff 0 1 0 158 159 

Improper or inadequate supervision by 

certified flight instructor or pilot not flying 0 0 0 146 146 

Complacency, overconfidence, or 

ostentatious display 1 0 0 142 143 

Diverted attention 0 1 4 114 119 

WX, thunderstorm or microburst 1 2 9 107 119 

Improper climb 0 1 3 106 110 

Improper or inadequate aircraft handling 2 1 2 93 98 

Wrong or unsuitable runway 0 0 4 92 96 

Improper altitude 0 1 3 84 88 

No causes, factors, or findings 0 1 8 71 80 

Improper alignment 0 0 2 73 75 

WX, wind shear 1 0 5 68 74 

Aircraft control not possible 1 2 3 62 68 

Anxiety/depression/panic/pressure 0 1 3 59 63 

Aircraft performance capability exceeded 0 0 2 55 57 

Lack of certification or qualification 0 0 0 54 54 

Improper or inadequate training 2 2 5 45 53 

Inadequate ice/frost removal 2 6 9 36 53 

Poor judgment 1 0 2 46 49 

 
NASA/TM—2010-216261 22 

TABLE 23.—Concluded. 

Causes or factors or findings 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, 

and 91 

combined 

Operation with known aircraft deficiency 0 0 1 46 47 

Company/operator deficiency 5 (38%) 6 17 17 45 

Wake turbulence 0 1 2 36 39 

Fatigue 1 1 3 34 39 

Climb not possible 0 0 4 34 38 

FAA deficiency 7 (54%) 4 4 20 35 

Improper aircraft handling 0 0 0 35 35 

Banner or glider tow flight 0 0 0 33 33 

Control interference 1 0 0 31 32 

Lost or disoriented 0 0 0 32 32 

Runway condition 0 2 3 26 31 

Checklist not followed 0 0 1 28 29 

Manufacturing deficiency 4 (31%) 1 7 13 25 

Improper or inadequate air traffic control 

service 1 1 0 21 23 

Improper glidepath 0 0 1 21 22 

Passenger interference 0 0 1 21 22 

Light (dusk or dawn) 0 0 1 21 22 

All available runway not used 0 0 0 15 15 

Visual/aural perception 0 0 0 13 13 

Pitot blockage 0 0 0 8 8 

WX information inaccurate or unavailable 0 0 0 8 8 

Cargo shifted 0 0 3 5 8 

Improper descent 0 0 0 7 7 

Light (Sun glare) 0 0 0 6 6 

Gust lock not removed 0 0 0 5 5 

Inadequate crew coordination 2 1 0 2 5 

Visual impairment (not physical) 0 0 0 5 5 

WX, high temperatures 0 0 0 5 5 

Improper or inadequate communication with 

air traffic control 0 0 1 3 4 

Light (flat) 0 1 1 1 3 

TABLE 24.—FREQUENCY OF PRIMARY CAUSES FOR ALL LOSS OF CONTROL (LOC) 

ACCIDENTS BY OPERATION CATEGORY 

Primary cause of LOC 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, and 

91 combined 

Total primary causes 26 (100%) 32 (100%) 198 (100%) 4961 (100%) 5217 (100%) 

Inadequate airspeed and/or stall 1 8 (25%) 51 (26%) 1971 (40%) 2031 (39%) 

Weather (WX), adverse winds 0 1 21 500 522 

Aircraft control not possible 9 (35%) 2 17 358 386 

Visual flight rules into instrument 

meteorological conditions 

0 0 2 260 262 

Aircraft control not maintained 0 0 8 215 223 

Spatial disorientation 1 2 7 211 221 

Unknown 0 1 12 118 134 

WX, icing 3 3 16 105 127 

Improper use of controls 0 1 4 117 123 

Pilot incapacitation 0 0 0 108 108 

Improper/premature liftoff 0 1 0 105 106 

WX, obscuration 0 0 6 83 89 

Low-altitude maneuvering 0 0 3 83 86 
NASA/TM—2010-216261 23 

TABLE 24.—Concluded. 

Primary cause of LOC 

Operation 

Part 121 Scheduled 

Part 135 

Nonscheduled 

Part 135 

Part 91 Part 121, 135, and 

91 combined 

Pilot impairment 1 0 2 83 86 

Incorrect weight/balance 1 0 11 73 85 

WX, thunderstorm 0 2 6 76 84 

Procedural or decision error 1 3 0 80 84 

Inadequate preflight 1 1 2 64 68 

WX, wind shear 1 0 4 58 63 

Inadequate ice/frost removal 2 6 13 33 54 

Lack of experience 0 0 0 49 49 

Diverted attention 0 0 2 45 47 

Wake turbulence 0 1 2 37 40 

WX, turbulence 0 0 2 31 33 

Aircraft performance capability 

exceeded 

0 0 0 31 31 

Incorrect or unsuitable runway 0 0 4 18 22 

Passenger interference 0 0 1 20 21 

Control interference 1 0 1 17 19 

Improper handling 0 0 0 9 9 

All available runway not used 0 0 0 3 3 

WX, blizzard 0 0 1 0 1 

Overall, the most common cause/factor/finding of all upset-related accidents was inadvertent 

stall/spin/mush. 

Because of a combination of the small number of control upset accidents in Part 121 and the large 

number of causal factors implicated in each of these accidents, it is difficult to determine a few “most 

likely” causes in Part 121. However, accidents in Part 121 operations are more likely than those in other 

flight categories to have some blame placed on improper use of controls, icing, company/operator 

deficiency, manufacturing defects, and FAA deficiencies. In the NTSB accident data, “improper use of 

controls” involves a pilot error with the use of controls and not a failure of the control system. Examples 

are incorrect trim or flap setting for a flight attitude, or not using anti-ice/de-ice equipment, or not 

lowering landing gear. 

In Scheduled Part 135 accidents, the most likely cause, factor, or finding during takeoff was 

inadequate ice/frost removal. During the en-route phase of flight, the most likely causes of control upset 

were stall/spin/mush, inadequate airspeed, icing, and improper use of controls. During the 

approach/landing phases of flight, the most likely causes of control upset were stall/spin/mush. 

In Nonscheduled Part 135 accidents, the most likely cause, factor, or finding during takeoff was 

winds. During the en-route and approach/landing phases of flight, the most likely cause, factor, or finding 

of control upset was inadequate airspeed. 

In Part 91 accidents, the most likely cause, factor, or finding during takeoff was inadequate ice/frost 

removal. During the en-route phase of flight, the most likely causes of control upset were stall/spin/mush, 

inadequate airspeed, icing, and improper use of controls. During the approach/landing phases of flight, the 

most likely cause, factor, or finding of control upset was stall/spin/mush. 

In Part 91 accidents, the most likely cause, factor, or finding during all phases of flight was 

inadvertent stall/spin/mush. 

In looking at only the primary cause of the control upset accidents, in Part 121, aircraft control was 

not possible in more than one-third of all LOC accidents. In the other three flight categories combined, 

more than 39 percent of the LOC was primarily caused by inadequate airspeed and/or stall.

2.5 Accident and Incident Data Analyses Conclusions 

In-flight LOC is a serious aviation problem. Well over half of the LOC accidents included at least one 

fatality (80 percent in Part 121), and roughly half of all aviation fatalities in the studied time period 
NASA/TM—2010-216261 24 

occurred in conjunction with LOC. Due to the level of aircraft damage and injury that is likely to occur, 

LOC events are rarely considered incidents 

In Part 121, LOC was somewhat more likely to occur during approach and landing (as opposed to 

takeoff or en route), but during takeoff, a LOC was most likely to result in a fatality. In Part 135 flights, 

LOC was most likely to occur during takeoff, although when control was lost during approach/landing 

80 percent of the accidents resulted in fatalities. En-route LOC was both the most frequent and the most 

often fatal of the three phases in Part 91 flights. 

In 31 percent of Part 121 LOC accidents, the LOC was secondary to an SCFM, compared with 8 to 

12 percent of the accidents in other flight operation categories. Twenty-three percent of the Part 121 LOC 

accidents were secondary to aircraft damage (most often due to fire), compared with 3 to 8 percent of the 

accidents in other flight operation categories. As a result, for roughly 35 percent of the LOC accidents in 

Part 121, aircraft control was not possible, compared with 6 to 9 percent of the accidents in other flight 

operation categories. In flights other than Part 121, 25 to 40 percent of the LOC was caused by inadequate 

airspeed leading to an inadvertent stall. Icing (both preflight and in-flight) and adverse winds were the 

primary cause of a large number of accidents. Other frequently cited causes for LOC are inadequate 

preflight, improper planning or decisions, and flying in obscuration or at night. 

3.0 NASA Analyses of Aviation Safety Reporting System (ASRS) Incident 

Data 

3.1 Introduction 

This section examines the composition of LOC incidents as reported in the ASRS. ASRS is a 

voluntary, nonpunitive, self-reporting system administered by NASA Ames Research Center that includes 

incident reports submitted by members of the flight crew and other persons 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. 

The Integrated Resilient Aircraft Control (IRAC) Project is focused on technologies that allow aircraft to 

operate in adverse conditions including loss of aircraft control and weather-related events. A previous 

IRAC report dealt with the topic of aircraft icing (Ref. 6), while this report will focus on LOC. 

Data used in this analysis are from the years January 1993 to March 2008. While the ASRS online 

database includes incidents starting in 1988, information on the Federal Aviation Regulation (FAR) part 

is available only beginning in 1993. Since other flight operations, such as Part 91 (general aviation), may 

have substantially different data compared with Parts 121 and 135, it was decided to use only those years 

for which FAR part was known. During this time period, there were 61,479 incident reports for 

Part 121 operations, 6208 incident reports for Part 135 operations, and 27,977 incident reports for Part 91 

operations. Each ASRS incident report lists the primary problem (or cause), an if applicable, the 

component involved. While this categorization is performed by the experts at ASRS, the IRAC systems 

analysis team further categorized those components into groups based on aircraft subsystems. 

To obtain statistical information, the ASRS Web tool was used to query the database. Our initial 

selection criterion was incidents in which the “anomaly” was “loss of control.” The Web tool allows the 

user to export the results to a Microsoft Excel (Microsoft Corporation) file, and relevant information such as 

“FAR part” and “Primary Problem” were kept. Since the Web tool’s data export function only includes 

those fields that can be queried using the tool, component information was later obtained through 

permission of the ASRS team at NASA Ames Research Center. These data were provided in a Microsoft 

Excel file with only the component and ASRS Incident Report Number (ACN), and were matched to the 

exported data using the ACN. After combining the data in one file, the aircraft system categorization was 

added. Statistical analysis system (SAS) software was then used to perform the statistical analysis. 
NASA/TM—2010-216261 25 

3.2 Primary Problems in Loss of Control Incidents 

For the years January 1993 to March 2008, there were 1285 LOC incidents in the ASRS database for 

Part 121, 282 LOC incidents for Part 135, and 2075 LOC incidents for Part 91. Three primary problems 

(causes) account for 972 (76 percent) of the Part 121 incidents, 244 (87 percent) of the Part 135 incidents 

and 1900 (92 percent) of the Part 91 incidents: flight crew human performance, aircraft, and weather. 

These areas will be the focus in this report. The total primary problem breakdown can be seen in 

Table 25. 

Because the IRAC Project is looking for technologies that can be incorporated in an aircraft, the 

specific areas of the aircraft that have been causing the most problems were more closely examined. 

Table 26 provides those LOC incidents that involved a component or system. For Part 121 incidents, an 

issue with air flight control was the most frequently cited (22 percent). Landing gear was cited most 

frequently in Part 135 operations (36 percent) and in Part 91 operations (24 percent.) 

A closer look is provided at those components and systems that were involved in the three most 

frequent primary problems: human performance, aircraft, and weather.

The human performance category includes the flight crew, air traffic control, cabin crew, and/or 

passengers. Looking at Table 27, the largest causes of human performance incidents are related to the 

human’s interaction with the landing gear, brakes, air flight control, and propulsion systems. These four 

systems account for over 68 percent of all LOC incidents related to human interaction with these systems. 

Later in the analysis, the top contributors to LOC incidents will be examined in more detail. 

TABLE 25.—FREQUENCY OF PRIMARY PROBLEMS IN LOSS OF CONTROL 

INCIDENTS BY OPERATION CATEGORY 

Primary problem 

Operation category 

Part 121 Part 135 Part 91 Part 91, 121, and 

135 combined 

Flight crew human 

performance 

338 (26%) 106 (38%) 1217 (59%) 1661 (46%) 

Aircraft 335 (26%) 96 (34%) 448 (22%) 879 (24%) 

Weather 299 (23%) 42 (15%) 235 (11%) 576 (16%) 

Airport 63 16 41 120 

Environmental factor 71 8 33 112 

Ambiguous 43 4 55 102 

Air traffic control human 

performance 

33 6 13 52 

Maintenance human 

performance 

27 3 17 47 

Company 40 1 4 45 

Other 18 0 6 24 

Airspace structure 6 0 3 9 

Federal Aviation 

Administration 

7 0 0 7 

Passenger human 

performance 

1 0 3 4 

Navigational facility 2 0 0 2 

Cabin crew human 

performance 

1 0 0 1 

Chart or publication 1 0 0 1 

Total 1285 (100%) 282 (100%) 2075 3642 (100%) 

 
NASA/TM—2010-216261 26 

TABLE 26.—FREQUENCY OF COMPONENTS OR SYSTEMS INVOLVED IN LOSS OF CONTROL (LOC) 

INCIDENTS BY OPERATION CATEGORY 

Component or system 

Operation category 

Part 121 Part 135 Part 91 Part 91, 121, and 

135 combined 

Landing gear 102 (19%) 47 (36%) 208 (26%) 357 (24%) 

Brakes 56 18 166 (21%) 240 (16%) 

Air flight control 117 (22%) 5 85 207 

Propulsion system 61 17 104 (13%) 182 

Control surfaces 73 15 56 144 

Monitoring 33 4 33 70 

Structures 6 5 14 41 

Electrical 9 2 14 25 

Miscellaneous 16 2 7 25 

Hydraulics 18 1 5 24 

Anti-icing 7 3 13 23 

Communications 3 2 14 19 

Navigation 8 0 10 18 

Fuel system 0 0 17 17 

Aircraft management 6 3 6 15 

Furnishings and equipment 7 3 5 15 

Weather systems 11 1 2 14 

Helicopter 4 1 8 13 

Environmental control 5 0 4 9 

Collision avoidance systems 2 0 0 2 

Navigation system 0 0 2 2 

Oil systems 0 0 1 1 

Total 544 (100%) 129 (100%) 790 (100%) 1463 (100%) 

TABLE 27.—FREQUENCY OF COMPONENTS OR SYSTEMS INVOLVED IN LOSS OF CONTROL 

INCIDENTS WITH PRIMARY PROBLEM: HUMAN PERFORMANCE BY OPERATION CATEGORY 

Component or system 

Operation category 

Part 121 Part 135 Part 91 Part 91, 121, and 

135 combined 

Landing gear 32 (19%) 10 (36%) 78 (26%) 120 (24%) 

Brakes 28 6 58 92 

Air flight control 39 2 47 88 

Propulsion system 20 5 57 82 

Control surfaces 12 5 32 49 

Monitoring 14 2 9 25 

Miscellaneous 9 0 6 15 

Structures 0 1 12 13 

Electrical 5 1 6 12 

Fuel system 0 0 12 12 

Navigation 5 0 6 11 

Anti-icing 2 1 6 9 

Communications 0 1 7 8 

Helicopter 1 1 5 7 

Furnishings and equipment 1 2 2 5 

Hydraulics 3 0 2 5 

Aircraft management 3 1 0 4 

Weather systems 8 1 0 9 

Environmental control 2 0 2 4 

Navigation system 0 0 1 1 

Total 178 (100%) 38 (100%) 349 (100%) 565 (100%) 
NASA/TM—2010-216261 27 

For aircraft-related LOC incidents seen in Table 28, the landing gear problems are the largest source 

of incidents. Incidents related to brakes, air flight control, control surfaces, and propulsion systems 

follow. The important thing to note about this list is that these incidents are caused primarily by aircraft 

problems, not human-related factors. So while we could dismiss the fact that landing gear was near the 

top of the list for incidents attributed to human performance errors, the fact that it is on top of this list is 

notable. 

TABLE 28.—FREQUENCY OF COMPONENTS OR SYSTEMS INVOLVED IN LOSS OF CONTROL 

INCIDENTS WITH PRIMARY PROBLEM: AIRCRAFT BY OPERATION CATEGORY 

Component or system 

Operation Category 

Part 121 Part 135 Part 91 Part 91, 121, and 

135 combined 

Landing gear 52 (21%) 36 (50%) 107 (30%) 195 (29%) 

Brakes 21 10 95 (27%) 126 (19%) 

Air flight control 56 3 29 88 

Control surfaces 50 8 17 75 

Propulsion system 20 9 41 70 

Monitoring 11 0 14 25 

Structures 3 2 12 17 

Hydraulics 12 1 3 16 

Aircraft management 3 2 5 10 

Electrical 3 1 6 10 

Furnishings and equipment 3 1 3 7 

Anti-icing 3 0 2 5 

Communications 1 1 3 5 

Helicopter 2 0 3 5 

Miscellaneous 3 1 1 5 

Environmental control 2 0 2 4 

Fuel system 0 0 4 4 

Navigation 2 0 2 4 

Navigation system 0 0 1 1 

Oil system 0 0 1 1 

Weather systems 1 0 0 1 

Total 248 (100%) 75 (100%) 351 (100%) 674 (100%) 

In LOC accidents with the primary problem of weather, the components or systems that were 

involved were much more varied than in the previous primary problem categories of human performance 

and aircraft (Table 29). In Part 121, the most frequent components or systems found to contribute to LOC 

incidents were air flight control and propulsion systems. Overall, the top four systems (air flight control, 

propulsion systems, monitoring, and control surfaces) account for 52 percent of all the primary problem 

LOC incidents in the weather category. 

After looking into the top three primary problems more in depth, the top five aircraft systems in terms 

of incidents caused have been looked at more closely. Landing gear, brakes, air flight control, propulsion 

system, and control surfaces together accounted for over 77 percent of the incidents that had components 

reported. In the following sections, we will highlight the individual components in each of these systems 

that account for the majority of LOC incidents caused. 

3.3 Most Frequently Cited Aircraft Systems in Loss of Control Incidents 

3.3.1 Landing Gear 

Landing gear was the most frequently cited system in LOC incidents. A breakdown of incident 

frequencies for all landing gear components can be seen in Table 30. Nose-wheel steering accounted for 

21 percent of these incidents. The top five most frequently cited landing gear components (nose-wheel 

steering, nose gear, main gear, antiskid system, gear extend/retract mechanism, and landing gear) account 

for over 75 percent of the landing gear incidents. (These five components are shaded in Table 30.) 
NASA/TM—2010-216261 28 

TABLE 29.—FREQUENCY OF COMPONENTS OR SYSTEMS INVOLVED IN LOSS OF CONTROL 

INCIDENTS WITH PRIMARY PROBLEM: WEATHER BY OPERATION CATEGORY 

Component or system 

Operation Category 

Part 121 Part 135 Part 91 Part 91, 121, and 

135 combined 

Air flight control 11 (20%) 0 6 17 (16%) 

Propulsion system 10 (19%) 2 (22%) 2 14 

Monitoring 4 1 8 13 

Control surfaces 5 22 (22%) 4 11 

Weather systems 8 1 0 9 

Anti-icing 1 22 (22%) 5 8 

Landing gear 5 0 3 8 

Brakes 2 0 5 7 

Structures 1 1 3 5 

Communications 1 0 2 3 

Environmental control 1 0 1 2 

Miscellaneous 2 0 0 2 

Navigation systems 0 0 2 2 

Aircraft management 0 0 1 1 

Collision avoidance system 1 0 0 1 

Electrical 1 0 0 1 

Furnishings and equipment 1 0 0 1 

Fuel system 0 0 1 1 

Total 54 (100%) 9 (100%) 43 (100%) 106 (100%) 

TABLE 30.—FREQUENCY OF LOC INCIDENTS RELATED 

TO LANDING GEAR COMPONENTS 

Landing gear component Frequency 

Nose-wheel steering 76 (21%) 

Nose gear 48 

Main gear 42 

Antiskid system 36 

Gear extend/retract mechanism 33 

Landing gear 33 

Main gear tire 20 

Wheels/tires/brakes 14 

Tail wheel 9 

Gear lever/selector 8 

Gear down lock 8 

Nose gear tire 6 

Nose gear wheel 4 

Tires 4 

Main gear wheel 3 

Wheel assemblies 3 

Nose gear door 2 

Gear float 2 

Gear ski 2 

Gear up lock 1 

Landing gear indicating system 1 

Main gear door 1 

Total 357 

 
NASA/TM—2010-216261 29 

3.3.2 Brakes 

Only three components were specified in brake-related incidents. The normal brake system accounted 

for just under half of these incidents, with brake system and parking brake accounting for the rest. (See 

Table 31 for actual percentages.) Since adaptive control technology is not likely to address these issues, 

the brake system might not be a focus of the IRAC project, but might be treated in a similar manner to 

landing gear. 

TABLE 31.—FREQUENCY OF LOSS OF CONTROL 

INCIDENTS RELATED TO BRAKE COMPONENTS

Brake component Frequency 

Normal brake system 132 (55%) 

Brake system 64 (27%) 

Parking brake 44 (18%) 

Total 240 (100%) 

3.3.3 Air Flight Control 

Looking into the air flight control system more in depth, the autopilot is the cause of over half of the 

LOC incidents (Table 32). Following this are the aeroplane flight control, autoflight system, and the flight 

management system/flight management computer. 

TABLE 32.—FREQUENCY OF LOSS OF CONTROL (LOC) INCIDENTS 

RELATED TO AIR FLIGHT CONTROL SYSTEM COMPONENTS 

Flight control system component Frequency 

Autopilot 104 

Aeroplane flight control 35 

Autoflight system 27 

Flight management system/flight management computer (FMS/FMC) 20 

Flight control computer (FCC) 5 

Mode control panel (MCP) 4 

Autoland 3 

Inertial navigation system (INS) inertial reference system (IRS)/inertial 

reference unit (IRU) 

2 

Flight augmentation computer (FAC) 2 

Full authority digital engine control (FADEC)/thrust control computer (TCC) 2 

Flight control unit (FCU) 2 

Altitude heading reference system (AHRS)/navigation display (ND) 1 

Total 207 

3.3.4 Propulsion Systems 

The propulsion system components that contribute to LOC incidents are much more varied than the 

other looked at in this study as shown in Table 33. The largest contributor to incidents in the propulsion 

system is the throttle/power level, with just over 15 percent of propulsion-related incidents. The next 

largest contributors were the engine, turbine engine, reciprocating engine assembly and the speedbrake 

spoiler. These components make up over 50 percent of propulsion-related incidents. These components 

are shaded in Table 25, and a full list of components that caused incidents relating to the propulsion 

system is available as well. 

3.3.5 Control Surfaces 

The actual components listed that fall under the control surfaces aircraft system are a little less 

concentrated than the previous two systems as presented in Table 34. The rudder, aileron, and elevator 

control systems account for 44 percent of all control-surface-related LOC incidents. The various control 

systems may be areas of research that the IRAC project could contribute to. 
NASA/TM—2010-216261 30 

TABLE 33.—FREQUENCY OF LOSS OF CONTROL INCIDENTS RELATED 

TO PROPULSION SYSTEM COMPONENTS 

Propulsion system component Frequency Propulsion system component Frequency 

Throttle/power level 28 (15%) Engine electric starter 1 

Engine 23 (13%) Engine starting system 1 

Turbine engine 15 Engine torque indication 1 

Reciprocating engine assembly 15 Exhaust manifold 1 

Speedbrake/spoiler 13 Inverter 1 

Turbine engine thrust reverser 11 Main rotor 1 

Propeller blade 9 Main rotor hub 1 

Rudder 9 Powerplant fuel control 1 

Engine control 7 Powerplant fuel distribution 1 

Thrust reverser control 4 Propeller assembly 1 

Carburetor 4 Propeller brake 1 

Powerplant fuel control unit 4 Propeller control 1 

Propeller pitch change mechanism 4 Propeller ice system 1 

Vacuum system 3 Propeller reversing 1 

Carburetor heat control 3 Reverse actuator 1 

Spoiler system 2 Reverser clamshell door 1 

Powerplant mounting 2 Supercharger 1 

Propeller 2 Switch 1 

Propeller synchronization 2 Vacuum pump 1 

Auxiliary engine turbine 1 

Combustor assembly 1 Total 182 

TABLE 34.—FREQUENCY OF LOSS OF CONTROL INCIDENTS 

RELATED TO CONTROL SURFACE COMPONENTS 

Control systems component Frequency 

Rudder control system 24 (17%) 

Aileron control system 20 (14%) 

Elevator control system 19 

Elevator trim system 18 

Elevator 8 

Horizontal stabilizer trim 7 

Trailing edge flap 6 

Pitot/static ice system 5 

Aileron 5 

Rudder pedal 5 

Trailing edge flap control 5 

Elevator control column 4 

Rudder trim system 4 

Flap/slat control system 3 

Horizontal stabilizer control 3 

Aileron control column 2 

Horizontal stabilizer 2 

Aileron trim system 1 

Elevator feel system 1 

Elevator tab 1 

Gust lock 1 

Total 144 

 
NASA/TM—2010-216261 31 

3.4 Aviation Safety Reporting System Data Analysis Conclusions 

Of the 1463 LOC incidents for Part 91, 12, and 135 identified with a system or component problems 

in the ASRS database, over 210 systems or components are identified as contributing to the incident. The 

most frequent of these components or systems are provided in Table 35. These 24 components account 

for 63 percent of all LOC incidents attributed to component or system failures or malfunctions. 

Looking at the analysis from a slightly higher level, five aircraft systems have been identified as 

critical in regards to the frequency of incidents they represent. These systems are landing gear, brakes, air 

flight control, propulsion systems, and control surfaces. 

TABLE 35.—FREQUENCY OF THE TOP SYSTEMS OR COMPONENTS 

RELATED TO LOSS OF CONTROL INCIDENTS 

System or component Frequency 

Normal brake system 132 

Autopilot 104 

Nose-wheel steering 76 

Brake system 64 

Nose gear 48 

Parking brake 44 

Main gear 42 

Antiskid system 36 

Aeroplane flight control 35 

Gear extend/retract mechanism 33 

Landing gear 33 

Throttle/power level 28 

Autoflight system 27 

Autothrottle/speed control 26 

Rudder control system 24 

Engine 23 

Aileron control system 20 

Flight management system/flight 

management computer 

20 

Main gear tire 20 

Elevator control system 19 

Attitude indicator 18 

Elevator trim system 18 

Hydraulic main system 15 

Turbine engine 15 

Total 920 

 
NASA/TM—2010-216261 32 

4.0 Adverse Conditions Table 

The purpose of the adverse conditions table found in the IRAC technical plan is to provide focus to 

the technology validation strategy. The adverse conditions are those events that lead or contribute to LOC 

incidents or accidents. These adverse condition types are categorized into three types: failure, damage, 

and upset. The failure adverse condition is defined as a system/component that does not work properly 

including degradation of performance. Damage is defined as a structure or component that is broken. 

Upset consists of pilot error and/or LOC due to occurrences that cannot be regulated via aircraft 

technology. 

The IRAC Systems Analysis Team has updated the initial adverse conditions table by collecting 

accident and incident data gleaned from findings within the ASRS, FAA, and NTSB databases. The intent 

was to call attention to damage conditions that occur frequently while providing insight on their severity 

and frequency. Primarily, the majority of the accidents were derived from the NTSB database, and the 

incidents were extracted from the ASRS database. 

Thirteen adverse conditions subtypes of significance were found. Suggested initial test conditions are 

provided in the table for each of the adverse condition subtypes. The severity and frequency of each 

subtype is provided also as a means of prioritizing the example damage conditions. Finally, applicable 

IRAC milestones are referenced. Table 36 is the updated adverse conditions table. 

TABLE 36.—ADVERSE TEST CONDITIONS 

Adverse 

condition 

Adverse condition 

subtype 

Severity and 

frequency 

Initial test conditions Milestone references 

Failure: System/ 

component does 

not work 

properly. 

Includes 

degradation of 

performance. 

1. Landing gear 

• Nose-wheel steering 

• Main gear and tire 

• Antiskid/braking 

system 

• Gear extend/retract 

mechanism 

Accident (1) 

Incident (597) 

• Use of a landing gear test 

facility to perform dynamometer 

testing of aircraft wheel and 

brake assemblies 

• Structural testing on strength 

and fatigue of body and wing 

landing gear (F–15) 

• Baseline F–15 

adaptive control 

assessment/validation 

• IRAC 4.1.1 

• Systems analysis/data 

mining for test 

condition refinement 

• IRAC 4.2.2 (leverages 

integrated vehicle 

health management 

(IVHM) data-mining 

expertise) 

• Requirements and test 

criteria 

• IRAC 2.5.2.2 

Simulation evaluation 

of test conditions 

• IRAC 3.1.1.1, 3.2.1.1, 

and 4.1.2.1 

• Full-scale F/A–18 

assessment/validation 

• IRAC 4.1.2.2 

2. Avionics 

• Autopilot/flight 

• Flight 

management/monitoring 

system 

• Weather radar 

Accident (1) 

Incident (347) 

Use of flight simulators to test 

numerous challenges using real 

flight data configuration, winds, 

terrain, and runway info 

3. Electrical 

• Auxiliary power unit 

• Radar 

• Actuator wire breaks 

• Wire chafing 

Accident (3) 

Incident (25) 

Physics of fault modeling at the 

component level and accelerated 

aging tests to characterize 

degradation 

4. Hydraulics Accident (0) 

Incident (24) 

Experimental testing of 

monitoring approach on a 

representative actuator subjected 

to nominal and accelerated wear 

conditions 

5. Static and dynamic 

actuator failure effects 

(single actuator and 

multiple actuator 

failures) 

Accident (n/a) 

Incident (n/a) 

• Locked stabilator (F–15) 

• Stabilator driven to local 

angle-of-attack (F/A–18) 

6. Environmental 

Control System 

• Pressurization system 

Accident (1) 

Incident (9) 

Perform pressurization 

diagnostic tests by means of 

actual or simulated flight (F–15) 

 
NASA/TM—2010-216261 33 

TABLE 36.—Concluded. 

Adverse 

condition 

Adverse condition 

subtype 

Severity and 

frequency 

Initial test conditions Milestone references 

Damage: 

Structure/ 

component is 

broken. 

7. Propulsion system 

• Throttle/power level 

system 

• Engine 

 -fire 

 -engine icing 

• Fuel system 

Accident (20) 

Incident (182) 

Use of an aircraft engine test 

facility to perform testing on all 

necessary components in 

addition to thrust measurements 

• Baseline F–15 

adaptive control 

assessment/validation 

• IRAC 4.1.1 

• Systems analysis/data 

mining for test 

condition refinement 

• IRAC 4.2.2 (leverages 

IVHM data-mining 

expertise) 

• Requirements and test 

criteria 

• IRAC 2.5.2.2 

• Simulation evaluation 

of test conditions 

• IRAC 3.1.1.1, 3.2.1.1, 

and 4.1.2.1 

• Full-scale F/A–18 

assessment/validation 

• IRAC 4.1.2.2 

8. Control surfaces 

• Rudder, aileron, and 

elevator 

Accident (8) 

Incident (144) 

9. Aerodynamic and 

structural damage 

(wing and/or tail) 

Accident (1) 

Incident (41) 

• Destabilizing angle-of-attack 

feedback to the canards, wing 

damage simulation (F–15) 

• Locked flaps (F/A–18) 

Upsets: 

Consists of pilot 

error and/or loss 

of control due to 

occurrences that 

cannot be 

regulated via 

aircraft 

technology. 

10. Electrical Accident (3) 

Incident (25) 

Physics of fault modeling at the 

component level and accelerated 

aging tests to characterize 

degradation 

• Systems analysis/data 

mining for test 

condition refinement 

• IRAC 4.2.2 (leverages 

IVHM data-mining 

expertise) 

• Requirements and test 

criteria 

• IRAC 2.5.1.1 

• Simulation evaluation 

of test conditions 

• IRAC 3.1.2.1 and 

3.2.2.1 

11. Severe weather 

• Icing 

• Winds 

• Poor evaluation of 

weather 

Accident (56) 

Incident (n/a) 

Analytical study of icing physics 

and winds; experimental testing 

of propulsion icing/winds in 

available facilities 

12. Inadequate 

attitude/airspeed, and/or 

stall/spin 

Accident (36) 

Incident (n/a) 

• Elevated angle of arrival (prestall) 

• Stall 

13. Pilot 

• Improper use of 

controls 

• Inadequate 

training/experience 

Accident (104) 

Incident (n/a) 

• Use of Ames Research 

Center’s “Human Factors 

Research” to further investigate 

testing procedures 

5.0 Discussion and Conclusions 

In-flight loss of control (LOC) is a serious aviation problem. Well over half of the LOC accidents 

included at least one fatality (81 percent in Part 121), and roughly half of all aviation fatalities in the 

studied time period occurred in conjunction with LOC. 

In Part 121, LOC was somewhat more likely to occur during approach and landing (as opposed to 

takeoff or en route), but during takeoff a LOC was most likely to result in a fatality. In Part 135 flights, 

LOC was least likely to occur en route, although when control was lost en route in Nonscheduled Part 135 

it almost always resulted in fatalities. 

In about 31 percent of in-flight Part 121 LOC accidents, the LOC was secondary to a 

system/component failure/malfunction, compared with 8 to 12 percent of the accidents in other flight 

operation categories. Twenty-three percent of the in-flight Part 121 LOC accidents were secondary to 

aircraft damage (most often due to fire), compared with 3 to 8 percent of the accidents in other flight 

operation categories. As a result, for roughly 35 percent of the inflight LOC accidents in Part 121, aircraft 
NASA/TM—2010-216261 34 

control was not possible, compared with 6 to 9 percent of the accidents in other flight operation 

categories. 

While the ASRS database includes over 210 components that contributed to LOC incidents in 

Parts 121, 135 and 91 flights, nearly 63 percent of all incidents were attributed to a component 

malfunction or failure related to about 24 components or systems. Five aircraft systems have been 

identified as critical in regards to the frequency of incidents they represent. These systems are landing 

gear, brakes, air flight control, propulsion systems, and control surfaces. The top five most cited systems 

or components in LOC incidents were normal brake system, autopilot, nose-wheel steering, brake system, 

and nose gear. 

The adverse conditions types were categorized as failure, damage, and upset. Thirteen separate 

adverse conditions subtypes were found. In the “failure” category, landing gear/brakes, avionics, 

electrical, and hydraulic systems account for the majority of LOC incidents. The propulsion system, 

control surfaces, and aerodynamic and structural damage account for the majority of LOC accidents and 

incidents in the “damage” category, while severe weather, inadequate attitude/airspeed, stall/spin, 

electrical, and pilot error account for the majority of “upset” LOC accidents. 

References 

1. Krishnakumar, Kalmanje; Viken, Sally; and Nguyen, Nhan: Integrated Resilient Aircraft Control. 

NASA Aeronautics Research Mission Directorate Aviation Safety Program, 2009. 

http://www.aeronautics.nasa.gov/nra_pdf/irac_tech_plan_c1.pdf Accessed July 15, 2010. 

2. Federal Aviation Administration: Aviation Safety Information Analysis Sharing (ASIAS) System. 

2010. http://asias.faa.gov Accessed July 15, 2010. 

3. National Transportation Safety Board: U.S. Air Carrier Operations Calendar Year 1999. Annual 

Review of Aircraft Accident Data, NTSB/ARC–02/03 (PB2002–109241), 1999. 

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

Accident Synopses. 2002. http://ntsb.gov/Info/gils/gilssyn.htm Accessed July 15, 2010. 

5. Commercial Aviation Safety Team/International Civil Aviation Organization Common Taxonomy 

Team: Aviation Occurrence Categories Definitions and Usage Notes. 4.1.4, 2008. 

http://www.intlaviationstandards.org/Documents/CICTTOccurrenceCategoryDefinitions.pdf Accessed 

July 15, 2010. 

6. Jones, Sharon Monica, et al.: Subsonic Aircraft Safety Icing Study. NASA/TM—2008-215107, 2008. 

 
NASA/TM—2010-216261 35 

Appendix A.—Acronyms 

ACN ASRS Incident Report Number 

ARC abnormal runway contact 

AHRS altitude heading reference system 

AMAN abrupt maneuver 

ARMD Aeronautics Research Mission Directorate 

ASIAS Aviation Safety Information Analysis and Sharing 

ASRS Aviation Safety Reporting System 

ATM air traffic management 

AvSAFE Aviation Safety Program 

CAST/ICAO Commercial Aviation Safety Team/International Civil Aviation Organization 

CICTT CAST/ICAO Common Taxonomy Team 

FAA Federal Aviation Administration 

FAC flight augmentation computer 

FADEC full authority digital engine control 

FAR Federal Aviation Regulation 

FCC flight control computer 

FCU flight control unit 

F–POST fire post impact 

FMC flight management computer 

FMS flight management system 

ICE icing 

Inst/Com/Nav instrumentation/communication/navigation 

IMC instrument meteorological conditions 

INS inertial navigation system 

IRAC Integrated Resilient Aircraft Control 

IRS inertial reference system 

IRU inertial reference unit 

IVHM integrated vehicle health management 

LOC loss of control 

LOC–I loss of control, in-flight 

MCP mode control panel 

NASA National Aeronautics and Space Administration 

ND navigation display 

NTSB National Transportation Safety Board 

RAMP ground handling 

SAS Statistical Analysis System 

SCFM system/component failure/malfunction 

SCF–NP system/component failure/malfunction, nonpowerplant 

SCF–PP system/component failure/malfunction, powerplant 

 
NASA/TM—2010-216261 36 

TCC thrust control computer 

UNK unknown 

VFR visual flight rules 

WSTRW windshear or thunderstorm 

WX weather 
NASA/TM—2010-216261 37 

Appendix B.—In-Flight Loss of Control Accidents in Part 121 and 

Scheduled Part 135 Flight Operations 

The tables in this appendix list the accidents in Part 121 and Scheduled Part 135 flight operations that 

were determined to include in-flight loss of control. In each table, the following information is provided: 

 National Transportation Safety Board (NTSB) report number 

 Event date 

 Commercial Aviation Safety Team/International Civil Aviation Organization (CAST/ICAO) aviation

occurrence categories determined for this accident

 If the accident included a system/component failure/malfunction (SCFM) of either the powerplant 

(SCF–PP) or non-powerplant (SCF–NP), the specific system involved is listed under “System.”

 The phase of flight for the initiating event of the accident. 

 The level of aircraft damage: destroyed, substantial, or minor. 

 The highest degree of injury associated with the accident (fatal, serious, minor, or none), and the 

number of fatalities, if any. 

 The primary cause for the loss of control. If the listed cause is “Not possible,” then the NTSB 

determined that under the circumstances (usually component failure or damage), it was not 

possible for the pilot to maintain control of the aircraft. 

Explanation of the CAST/ICAO aviation occurrence categories cited in the tables is provided below 

(Ref. 5). 

Common Taxonomy Team Aviation Occurrence Categories Definitions found in Tables 37 to 42 

AMAN (abrupt maneuver).—The intentional abrupt maneuvering of the aircraft by the flight crew 

ARC (abnormal runway contract).—Any landing or takeoff involving abnormal runway or landing 

surface contact 

ATM (ATM/CNS).—Occurrences involving air traffic management (ATM) or communications, 

navigation, or surveillance (CNS) service issues 

F–NI (Fire/smoke (nonimpact)) 

F–POST (Fire/smoke (post-impact)).—Fire/smoke resulting from impact 

ICE (icing).—Accumulation of snow, ice, freezing rain, or frost on aircraft surfaces that adversely 

affects aircraft control or performance 

LALT (low-altitude operations).—Collision or near collision with obstacles/objects/terrain while 

intentionally operating near the surface (excludes takeoff or landing phases) 

LOC–I (loss of control–in-flight).—Loss of aircraft control while or deviation from intended flight path 

in flight 

RAMP (Ground handling).—Occurrences during (or as a result of) ground handling operations 

RE (runway excursion).—A veer off or overrun off the runway surface 

SCF–NP (system/component failure/malfunction (non-powerplant)).—Failure or malfunction of an 

aircraft system or component, other than the powerplant 

SCF–PP (system/component failure/malfunction (powerplant)).—Failure or malfunction of an aircraft 

system component related to the powerplant 

TURB (turbulence encounter).—In-flight turbulence encounter 

UNK (unknown or undetermined).—Insufficient information exists to categorize the occurrence 

WSTRW (windshear or thunderstorm).—Flight into windshear or thunderstorm 

 
NASA/TM—2010-216261 38 

TABLE 37.—LOSS OF CONTROL (LOC) ACCIDENTS IN PART 121 (1988 TO 2004) FOLLOWING SCFM 

NTSB report 

number 

Event 

date 

CAST/ICAO 

aviation 

occurrence 

categories 

System Phase of 

flight 

Aircraft 

damage 

Highest 

injury 

(fatalities) 

Cause of LOC 

DCA00MA026 2/16/2000 SCF–NP, LOC–I, 

F–POST 

Flight control Takeoff Destroyed Fatal 

(3) 

Not possible 

DCA03MA022 1/8/2003 SCF–NP, RAMP, 

LOC–I, 

F–POST 

Flight control Takeoff Destroyed Fatal 

(21) 

Not possible 

DCA00MA023 1/31/2000 SCF–NP, LOC–I Flight control Cruise Destroyed Fatal 

(88) 

Not possible 

DCA94MA076 9/8/1994 SCF–NP, LOC–I, 

F–POST 

Flight control Approach Destroyed Fatal 

(132) 

Not possible 

MIA96FA059 1/7/1996 SCF–NP, LOC–I Landing gear Takeoff Substantial Minor Improper 

procedure or 

decision 

DCA92MA022 2/15/1992 SCF–NP, LOC–I, 

F–POST 

Inst/Com/ 

Nav 

Missed 

Approach 

Destroyed Fatal 

(4) 

Spatial 

disorientation 

DCA91MA023 3/3/1991 SCF–NP, LOC–I, 

F–POST 

Flight control Approach Destroyed Fatal 

(25) 

Not possible 

DCA89MA063 7/19/1989 SCF–PP, LOC–I, 

F–POST 

Engine Cruise Destroyed Fatal (111) Not specified 

TABLE 38.—LOSS OF CONTROL (LOC) ACCIDENTS IN PART 121 (1988 TO 2004) FOLLOWING DAMAGE 

NTSB report 

number 

Event date CAST/ICAO 

accident 

categories 

System Phase of 

flight 

Aircraft 

damage 

Highest 

injury 

(fatalities) 

Cause of LOC 

MIA97RA011 10/22/1996 F–NI, 

LOC–I 

None Takeoff Destroyed Fatal (340) UNK 

DCA96MA054 5/11/1996 F–NI, 

LOC–I 

None Climb Destroyed Fatal (110) Not possible 

DCA96MA070 7/17/1996 F–NI, 

LOC–I 

None Climb Destroyed Fatal (230) Not possible 

DCA02MA001 11/12/2001 AMAN, 

SCF–NP, 

LOC–I, 

F–POST 

Flight 

control 

Takeoff Destroyed Fatal (265) Not possible 

MIA95RA162 6/27/1995 F–NI, 

LOC–I 

None Maneuvering Destroyed Fatal (2) UNK 

ANC96FA102 7/20/1996 SCF–PP, 

F–NI, 

SCF–NP, 

LOC–I 

Engine, 

wing 

Cruise Destroyed Fatal (4) Not possible 

TABLE 39.—LOSS OF CONTROL (LOC) ACCIDENTS IN PART 121 (1988 TO 2004) FOLLOWING 

CONTROL UPSET 

NTSB report 

number 

Event date CAST/ICAO 

accident 

categories 

System Phase of 

flight 

Aircraft 

damage 

Fatalities Cause of 

LOC 

DCA88MA072 8/31/1988 LOC–I, 

F–POST 

None Takeoff Destroyed Fatal 

(14) 

Improper use 

of controls 

DCA91MA021 2/17/1991 ICE, 

LOC–I, 

F–POST 

None Takeoff Destroyed Fatal (2) Inadequate 

ice removal 

DCA92MA025 3/22/1992 ICE, 

LOC–I 

None Takeoff Destroyed Fatal 

(27) 

Inadequate 

ice removal 
NASA/TM—2010-216261 39 

TABLE 39.—Concluded. 

NTSB report 

number 

Event date CAST/ICAO 

accident 

categories 

System Phase of 

flight 

Aircraft 

damage 

Fatalities Cause of 

LOC 

DCA97MA059 8/7/1997 RAMP, 

LOC–I, 

F–POST 

None Takeoff Destroyed Fatal (5) Weight and 

balance 

MIA94FA169 6/29/1994 LOC–I None Cruise Minor Serious Control 

interference 

DCA95MA001 10/31/1994 ICE, 

LOC–I 

None Maneuvering Destroyed Fatal 

(68) 

Icing 

DCA97MA049 5/12/1997 LOC–I None Descent Minor Serious Airspeed/ 

stall 

DCA01MA031 3/19/2001 ICE, 

LOC–I 

None Cruise Substantial None Icing 

CHI89MA057 3/15/1989 ICE, 

LOC–I, 

F–POST 

None Descent Destroyed Fatal (2) Icing 

DCA89MA035 3/18/1989 RAMP, 

LOC–I, 

F–POST 

None Takeoff Destroyed Fatal (2) Inadequate 

preflight 

DCA93RA060 8/18/1993 LOC–I, 

F–POST 

None Approach Destroyed Serious Pilot 

impaired 

DCA94MA065 7/2/1994 ATM, 

WSTRW, 

LOC–I, 

F–POST 

None Missed 

approach 

Destroyed Fatal 

(37) 

Windshear 

TABLE 40.—LOSS OF CONTROL (LOC) ACCIDENTS IN SCHEDULED PART 135 (1988 TO 2004) 

FOLLOWING SCFM 

NTSB report 

number 

Event date CAST/ICAO 

accident 

categories 

System Phase of 

flight 

Aircraft 

damage 

Highest 

injury 

(fatalities) 

Cause of 

LOC 

DCA88MA059 5/24/1988 SCF–PP, 

LOC–I, 

F–POST 

Engine Takeoff Destroyed Serious Improper 

procedure or 

decision 

DCA91MA052 9/11/1991 SCF–NP, LOC–I, 

F–POST 

Flight 

control 

Descent Destroyed Fatal (14) Not possible 

DCA91MA033 4/5/1991 SCF–PP, LOC–I, 

F–POST 

Propeller Approach Destroyed Fatal (23) Not possible 

TABLE 41.—LOSS OF CONTROL (LOC) ACCIDENTS IN SCHEDULED PART 135 (1988 TO 2004) 

FOLLOWING DAMAGE 

NTSB report 

number 

Event date CAST/ICAO 

accident 

categories 

System Phase of 

flight 

Aircraft 

damage 

Highest 

injury 

(fatalities) 

Cause of 

LOC 

ANC00MA125 9/18/2000 ARC, 

SCF–NP, LOC–I, 

F–POST 

Landing 

gear 

Landing Destroyed Fatal (5) Airspeed or 

stall 
NASA/TM—2010-216261 40 

TABLE 42.—LOSS OF CONTROL (LOC) ACCIDENTS IN SCHEDULED PART 135 (1988 TO 2004) 

FOLLOWING CONTROL UPSET

NTSB report 

number 

Event date CAST/ICAO 

accident 

categories 

System Phase of 

flight 

Aircraft 

damage 

Fatalities Cause of LOC 

DCA88MA032 2/19/1988 LOC–I, 

F–POST 

None Takeoff Destroyed Fatal 

(12) 

Spatial 

disorientation 

ANC90LA076 5/24/1990 LOC–I None Takeoff Substantial None Adverse 

weather, winds 

ANC92LA052 3/24/1992 LOC–I None Takeoff Substantial Minor Airspeed or 

stall 

ANC92LA057 4/2/1992 ICE, RAMP, 

LOC–I 

None Takeoff Substantial None Inadequate ice 

removal 

ANC92LA140 8/22/1992 LOC–I None Takeoff Substantial None Improper 

procedure or 

decision 

LAX93LA019 10/27/1992 TURB, LOC–I None Takeoff Destroyed Fatal (3) Wake 

turbulence 

ANC93FA034 2/20/1993 ICE, LOC–I None Takeoff Destroyed None Inadequate ice 

removal 

LAX93FA287 7/12/1993 RAMP, LOC–I, 

F–POST 

None Takeoff Destroyed Fatal (3) Inadequate 

preflight 

ANC96LA012 11/3/1995 ICE, LOC–I None Takeoff Substantial None Inadequate ice 

removal 

ANC98MA008 11/8/1997 ICE, RAMP, 

LOC–I 

None Takeoff Destroyed Fatal (8) Inadequate ice 

removal 

ANC98LA056 5/21/1998 LOC–I None Takeoff Substantial None Premature 

liftoff 

NYC99FA220 9/5/1999 LOC–I None Takeoff Substantial Fatal (3) Airspeed or 

stall 

ANC00LA021 12/24/1999 ICE, LOC–I None Takeoff Substantial Minor Inadequate ice 

removal 

SEA02FA002 10/3/2001 RAMP, LOC–I None Takeoff Substantial Fatal (3) Airspeed or 

stall 

DCA02MA003 10/10/2001 ICE, LOC–I None Takeoff Destroyed Fatal 

(10) 

Inadequate ice 

removal 

ANC91LA021 1/18/1991 LALT, LOC–I None Maneuvering Substantial Serious Airspeed or 

stall 

ANC92FA083 12/13/1991 LOC–I, F-POST None Cruise Destroyed Fatal (1) UNK 

MIA92FA067 1/23/1992 WSTRW, LOC–I None Descent Destroyed Fatal (2) Thunderstorm 

FTW93MA143 4/29/1993 ICE, LOC–I, 

SCF–PP, RE 

Propeller Climb Substantial Minor Icing 

ANC99FA047 4/14/1999 LOC–I None Cruise Destroyed Fatal (1) Spatial 

disorientation 

DCA90MA011 12/26/1989 ICE, ATM, 

LOC–I, F–POST 

None Approach Destroyed Fatal (6) Icing 

DCA91MA042 7/10/1991 WSTRW, 

LOC–I, F–POST 

None Approach Destroyed Fatal 

(13) 

Thunderstorm 

MIA92MA131 6/7/1992 LOC–I None Approach Destroyed Fatal (5) Controls 

DCA94MA027 1/7/1994 LOC–I, 

F–POST 

None Approach Destroyed Fatal (5) Airspeed or 

stall 

ANC94LA031 2/8/1994 LOC–I None Approach Substantial None Airspeed or 

stall 

DCA95MA006 12/13/1994 LOC–I, 

 F–POST 

None Approach Destroyed Fatal 

(15) 

Improper 

procedure or 

decision 

DCA97MA017 1/9/1997 ICE, LOC–I, 

F–POST 

None Approach Destroyed Fatal 

(29) 

Airspeed or 

stall 

ANC00LA009 10/28/1999 ICE, LOC–I None Cruise Substantial None Icing 
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Causal Factors and Adverse Conditions of Aviation Accidents and Incidents Related to 

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14. ABSTRACT

The causal factors of accidents from the National Transportation Safety Board (NTSB) database and incidents from the Federal Aviation 

Administration (FAA) database associated with loss of control (LOC) were examined for four types of operations (i.e., Federal Aviation 

Regulation Part 121, Part 135 Scheduled, Part 135 Nonscheduled, and Part 91) for the years 1988 to 2004. In-flight LOC is a serious 

aviation problem. Well over half of the LOC accidents included at least one fatality (80 percent in Part 121), and roughly half of all aviation 

fatalities in the studied time period occurred in conjunction with LOC. An adverse events table was updated to provide focus to the 

technology validation strategy of the Integrated Resilient Aircraft Control (IRAC) Project. The table contains three types of adverse 

conditions: failure, damage, and upset. Thirteen different adverse condition subtypes were gleaned from the Aviation Safety Reporting 

System (ASRS), the FAA Accident and Incident database, and the NTSB database. The severity and frequency of the damage conditions, 

initial test conditions, and milestones references are also provided.

15. SUBJECT TERMS

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