DOT/FAA/AM-96/21

Office ofAviation Medicine

Washington, D.C. 20591

Fatal General Aviation

Accidents Involving Spatial

Disorientation: 1976-1992

William E. Collins

Carolyn S. Dollar

Civil Aeromedical Institute

Federal Aviation Administration

Oklahoma City, Oklahoma 73125

August 1996

Final Report

19960913 118

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NOTICE

This document is disseminated under the sponsorship of

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

information exchange. The United States Government

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

1. Report No.

DOT/FAA/AM-96/21

2. Government Accession No.

4. Title and Subtitle

Fatal General Aviation Accidents Involving Spatial

Disorientation: 1976-1992

7. Author©

W.E. Collins and C.S. Dollar

9. Performing Organization Name and Address

FAA Civil Aeromedical Institute

P.O. Box 25082

Oklahoma City, OK 73125

3. Recipient's Catalog No.

5. Report Date

August 1996

6. Performing Organization Code

8. Performing Organization Report No.

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency name and Address

Office of Aviation Medicine

Federal Aviation Administration

800 Independence Ave., S.W.

Washington, DC 20591

13. Type of Report and Period Covered

14. Sponsoring Agency Code

15. Supplemental Notes

16. Abstract

The National Transportation Safety Board (NTSB) analyzes circumstances and data from general aviation accidents

and ascribes one or more causes and/or related factors to help explain each accident. The present study was

undertaken to (a) provide information regarding the circumstances surrounding fatal general aviation accidents

involving spatial disorientation, and (b) define demographic and behavioral characteristics of the spatiallydisoriented pilot. Computer retrievals of NTSB brief reports of all spatial disorientation accidents from 1976-92

were analyzed in terms of age and experience of pilots, actions of pilots, night or day, weather, and other

conditions. The computer search yielded 1,022 reports of spatial disorientation accidents, which for the 17-year

period resulted in 2,355 fatalities. Related causes and circumstances associated with the accidents were analyzed

and categorized. The frequency of spatial disorientation accidents during 1976-92 peaked at 97 fatal accidents in

1977 and generally declined thereafter. The proportion of involved pilots who held an instrument rating about

doubled when comparing 1976-83 to 1984-92, over 70% of the accidents were associated with instrument

meterological conditions, and about half of the accidents occurred at night. The proportion of fatal general aviation

accidents associated with spatial disorientation has declined significantly since an earlier study (1970-75).

17. Keywords

Spatial disorientation

General Aviation

Fatal accidents

18. Distribution Statement

Document is available to the public through the

National Technical Information Service

Springfield, Virginia 22161

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

15

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
FATAL GENERAL AVIATION ACCIDENTS INVOLVING

SPATIAL DISORIENTATION: 1976-1992

INTRODUCTION

In aviation, spatial disorientation refers to a false

perception of distance, attitude, or motion of the

pilot and the aircraft, relative to the plane of the

earth's surface (2). Over the years, there have been

various refinements of that definition based on a

continued interest in the phenomenon (9, 12); that

interest is rooted in the prevalence of spatial disorientation as a cause/factor in fatal aircraft accidents.

Historically, spatial disorientation has been identified consistently as a cause in about 15% of fatal

U.S. military aviation accidents. Similarly, during

the period from 1970-75, civil aviation statistics

showed spatial disorientation as a cause/factor in

15-16% of general aviation fatal accidents (10).

The present study examined the role of spatial

disorientation in fatal general aviation accidents

between 1976-1992 and explored possible demographic and behavioral characteristics of spatiallydisoriented pilots.

The data and approach presented here differ from

that of Mortimer (12) who recently provided analyses of the relationships of a variety of factors to

combined fatal and nonfatal spatial disorientation

accidents in general aviation grouped across the 9-

year block of 1983-1991. His analyses provide a

different and useful perspective on this historically

significant aspect of aviation mishaps. His assessments include types of aircraft, crash severity, environment, pilot certifications, and other pilot

characteristics such as profession, physical/psychological impairments, sex, and aspects of flying experience.

METHODS

Requests were made to the National Transportation Safety Board (NTSB) for computer print-outs

of report briefs of all spatial disorientation accidents

from 1976 through 1992. Although there have been

changes in format and content over time, these briefs

each contain certain standard information regarding

aviation accidents (statement ofcause, nature ofinjuries, etc.). The reports were examined and analyzed in

terms oftype ofaccident, age and experience ofpilots,

actions of pilots, night or day, weather, and other

conditions.

RESULTS

Tabulations over the 17-year period (1976-1992)

yielded a total of 51,444 accidents (11) of which

9,269 included fatalities (Table 1). Overall, the combined totals of all fatal and nonfatal general aviation

accidents increased from 1976-1978 and then declined regularly through 1992. The number of fatal

accidents also reached a peak in 1978 and declined

thereafter in a slightly irregular but consistent pattern

(Table 1). While "all accidents" declined by about

50% in number from 1978-1992, the number offatal

accidents declined by about 40%. That difference is

reflected in a pattern in which the percentage offatal

accidents to total accidents shows an internally irregular but step-like increase from a range of 16.5-17.2%

during 1976-80, to 17.9-18.7% during 1981-87, to

19.3-21.6% during 1988-92.

The peak year for number of fatalities in all accidents was also 1978 (1,556 deaths). The number of

fatalities has declined in a consistent but slightly

irregular pattern since that time to a total of 858 in

1992 - a 45% decline (Table 1). (The decline exceeded 50% in 1990 when there were 766 fatalities.)

The number of fatal accidents in which spatial

disorientation was a cause/factor peaked in 1977

(Figure 1) and has shown a steady if irregular decline

of about 70% through 1992 (Table 2). Thus, on a

proportional basis, the reduction from peak incidence

of fatal general aviation accidents involving spatial

Data in this report were presented at the annual meeting ofthe Aerospace Medical Association in May 1995. The assistance ofCarol Floyd,

NTSB, in providing data printouts is gratefully acknowledged.
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Spatial Disorientation (SD) as a Cause/Factor

in General Aviation Accidents

1976 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 1992

Year

Figure 1. Number of Fatal Accidents with Spatial Disorientation as the

Cause/Factor: 1976- 1992.

TABLE 2

Spatial Disorientation (SD) as a Cause/Factor

in Fatal General Aviation Accidents (Data column 1 is from reference 11)

Total Fatal SD SD Total SD %SD

Year Accidents Cause Factor Cause/Factor Cause/Factor

1976 662 87 0 87 13.1

1977 663 97 0 97 14.6

1978 719 89 1 90 12.5

1979 631 87 0 87 13.8

1980 618 78 1 79 12.8

1981 654 90 0 90 13.8

1982 591 64 2 66 11.2

1983 556 53 4 57 10.3

1984 545

498

40 11 51 9.4

1985 34 7 41 8.2

1986 474 36 6 42 8.9

1987 447 36 12 48 10.7

1988 460 41 10 51 11.1

1989 431 38 6 44 10.2

1990 442 22 9 31 7.0

1991 431 27 5 32 7.4

1992 447 28 1 29 6.5

Totals 9269 947 75 1022

% of Total io.2 0.8 11.0

Fatal Accidents
disorientation (about 70%) markedly outpaced the

reduction in the incidence offatal accidents in general

(about 40%) during this 1976-1992 time period.

Similarly, with regard to fatalities in spatial disorientation accidents (Table 1), the peak (223) occurred in

1977; that number declined irregularly to 83 (a 63%

reduction) in 1992 (and was as low as 60 - a 73%

decline from peak - in 1990).

As a proportion of all fatal accidents (Table 2), the

proportion attributable to spatial disorientation has

declined from a high of 14.6% in 1977 to a low of

6.5% in 1992 (a reduction of 55%). A similar finding

emerges from the data regarding the proportion of

deaths in spatial disorientation accidents to total

fatalities; that percentage declined from 17.4% in

1977 to 9.7% in 1992 -a 44% reduction -butwas as low

as 7.8% in 1990 - a 55% reduction (Table 1).

Spatial Disorientation and the Pilot

Table 3 provides the age distribution of pilots

involved in fatal spatial disorientation accidents. The

greatest incidence (29.9%) is in the fifth decade oflife

(ages 40-49); that coincides with the peak age group

for all active pilots (3,4). The vast majority of these

pilots (71.5%) held private pilot certificates, 12.1%

had commercial pilot certificates, and 7.2% were

student pilots.

TABLE 3

Age of Pilots in Fatal Accidents with Spatial Disorientation as a Cause/Factor

Year

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

Totals

%

<20

Age in Years

20-29 30-39 40-49 50-59

N=1017 - the ages of 5 pilots were not recorded

4

60-69

2 13 25 26 19 2

3 20 19 29 19 5

0 13 25 22 26 4

2 19 16 22 22 6

2 25 17 22 11 2

2 12 22 31 19 3

1 12 16 20 11 4

0 8 16 20 10 1

0 13 9 16 10 2

0 4 15 9 8 5

0 5 17 12 3 4

0 6 7 17 9 8

0 5 11 17 9 8

1 1 8 14 12 6

0 5 6 8 7 2

0 5 9 8 7 3

0 3 5 11 6 3

13 169 243 304 208 68

1.3 16.6 23.9 29.9 20.5 6.7

70-79 80-89

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With regard to flying experience, 48.2% of the

pilots had 500 or more total flight hours (Table 4).

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greatestincidence (16.3%) was in the category of 100-

199 hours of flying experience. For the number of

hours each pilot had logged in the type of aircraft

being flown during the accident, two categories (50

hours or fewer and 51-200 hours in type) each comprised about 25% ofthe total pilots; that translates to

approximately 35% in each of the two categories

based on the known hours logged (Table 5) since

about 30% of the cases were recorded as unknown.

Historically a significant proportion ofspatial disorientation accidents occurs in adverse weather. "Instrument Meteorological Conditions" (IMC) as

opposed to visual meteorological conditions (VMC)

most often describe the weather in such accidents.

Table 6 indicates that the proportion of pilots with

instrument-ratings has increased by about 50% over

the 1976-1992 time span, while the proportion of

private pilots to total pilots has remained about the

same and number of accidents has declined (6,7,8).

The extent to which "altered states" ofthe pilots, as

evidenced by the presence of alcohol and other drugs,

were associated with fatal spatial disorientation accidents was assessed (Table 7). Overall, 7.0% of the

accidents involved some drugs (and 1 case of hypoxia). Alcohol was the most prevalent drug involved

at 5.6% over the 17-year span. However, the rate of

alcohol involvement averaged less than 2% from 1987-

1992 and averaged greater than 7% for the preceding

11 years. These rates ofalcohol involvement in spatial

disorientation accidents are somewhat lower than the

rates obtained for all fatal accidents in general (1), where,

for example, the rates ranged from 5.5 to 8.2% during

1987-1992.

TABLE 5

Experience of Pilots in Fatal Accidents with Spatial

Disorientation as a Cause/Factor

Hours in Type of Aircraft

Year < or = 50 51-200 201-500 501-999 = or > 1,000 Unknown

1976 32 22 8 3 2 20

1977 21 32 12 3 2 27

1978 23

21

26 16 1 4 20

1979 20 14 3 5 24

1980 20 17 10 4 1 27

1981 24

12

19 5 2 3 37

1982 22 8 0 2 22

1983 17 16 5 0 1 18

1984 11

11

12 5 0 7 16

1985 10 6 1 2 11

1986 5 11 9 2 1 14

1987 12 8 8 5 2 13

1988 9 15 6 3 0 18

1989 10 11 7 2 5 9

1990 9 5 5 2 3 7

1991 5 8 6 1 4 8

1992 5 6 3 1 3 11

Totals 247 260 133 33 47 302

% 24.2 25.4 13.0 3.2 4.6 29.5
Weather and Spatial Disorientation

Inclement weather and spatial disorientation interact in a significant fashion to produce fatal accidents.

To examine this interaction more clearly, various

features offatal accidents in which spatial disorientation and weather were cause/factors are summarized

in Table 8. Flight was initiated into adverse weather

in 21.3% ofthese accidents; flight was continued into

adverse weather in 41.3%. At the time of accidents,

VMC weather conditions existed only 17.9% and

IMC conditions 80.2% of the time (1.9% not reported).

By far the greatest proportion of accidents, 85%,

occurred as a result of collision with the ground,

water, or a structure, but inflight breakup occurred in

14% (Table 9). No weather briefing was recorded in

37.3% ofthe fatal flights; briefings were recorded in

51.7% of the cases and partial briefings (usually "cut

short by pilot") in 1.2% (10% were missing data or

"unknown").

The most prevalent weather condition involved fog

(47.8%) with rain the next most frequent (Table 10).

Low ceilings were involved in a major proportion

(54%) of these accidents. Also, 40.9% of the accidents occurred during daylight hours, 50.6% at night,

5.3% at dusk, and 1.8% at dawn (1.5% unknown or

not given).

DISCUSSION

The number of fatal general aviation accidents in

which spatial disorientation was attributed to be a

cause or factor has declined considerably since

1977. That decline parallels declines in total accidents

TABLE 6

Prevalence of Private Pilots and Instrument

Rated Pilots in the Airman Population

(Data columns 1, 2, and 4 are from references 6, 7, and 8)

Year

Total Pilots Private Pilots

% Private

Pilots

Instrument

Rated Pilots

% Pilots

Instrument Rated

1976

1977

1978

744,246

783,932

798,833

309,005

. 327,424

337,644

41.5

41.8

42.3

211,364

226,334

236,312

28.4

28.9

29.6

1979 814,567 343,275 42.1 247,096 30.3

1980 827,071 357,479 43.2 260,461 31.5

1981 764,182 328,562 43.0 252,535 33.0

1982 733,266 322,091 43.9 256,073 34.9

1983 718,004 318,643 44.4 254,271 35.4

1984 722,376 320,086 44.3 256,584 35.5

1985 709,540 311,086 43.8 258,559 36.4

1986 709,118 305,736 43.1 262,388 37.0

1987 699,653 300,949 43.0 266,122 38.0

1988 694,016 299,786 43.2 273,804 39.5

1989 700,010 293,179 41.9 282,804 40.4

1990 702,659 299,111 42.6 297,073 42.3

1991 692,095

1992 682,959

293,306

288,078

42.4

42.2

303,193

306,169

43.8

44.8

Totals 12,496,527 5,355,440 4,451,142

% of Total Pilots 42.9 35.6
TABLE 7

Incidence of Alcohol/Drugs/Hypoxia

in Fatal Spatial Disorientation (SD) Accidents

Altered States

Year

Total SD

Accidents Alcohol

Marijuana/

Cocaine Prescription

Mixed

Alcohol/Druq Hvpoxia

%of SD

Accidents

1976

1977

1978

87

97

90

87

79

90

7

5

6

4

4

8

0

0

0

1

0

0

0

0

0

0

0

0

9.2

5.2

6.7

1979

1980

1981

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

4.6

5.1

10.0

1982

1983

1984

66

57

51

41

42

48

2

7

2

5

5

0

0

0

0

0

0

0

3.0

12.3

3.9

1985

1986

1987

0

1

0

1

0

0

1

0

1

0

0

0

17.1

14.3

2.1

1988

1989

1990

51

44

31

32

29

1

0

1

0

0

0

1

0

1

0

1

1

1

1

0

0

0

0

0

5.9

4.5

6.5

1991

1992

1

1

0

0

1

0

9.4

3.4

Totals 1022 57 3 8 3 1

% of SD accidents 5.6 0.3 0.8 0.3 0.1 7.0

and fatal accidents in general over the same time

period, but the reduction has been proportionately

greater for spatial disorientation.

In the 1970-1975 period, spatial disorientation

accounted for 15% of general aviation accidents, only

15% of the pilots involved had instrument ratings,

and about 88% of the accidents involved "initiating

or continuing flightinto adverse weather" (10). Those

proportions changed dramatically over the 17 subsequent years. For example, during the 1984-1992

period, the proportion of fatal spatial disorientation

accidents ranged from 6.5-11.1% of all fatal accidents, pilots involved in those accidents who had

instrument ratings ranged from 33.3-54.2%, and the

proportion involving "flight into adverse weather"

ranged from 43.9-59.1 %. Moreover, the latter decline

from 1970-1975 levels is largely attributable to a

sharp reduction in the incidence ofcontinuing flight

into adverse weather.

The decline in fatal spatial disorientation accidents

clearly has a relation to the overall reductions in the

following: the number of active airmen, the number

ofhours flown, the number oftotal accidents, and the

number offatal accidents. However, the proportionately larger reduction in fatal spatial disorientation accidents over the same time period requires additional

analysis. One factor - a general increase in the proportion of pilots holding instrument ratings and the

(perhaps) seemingly paradoxical increase in the incidence ofpilots with instrument ratings being involved

in fatal spatial disorientation accidents - may be

relevant. Instrument proficiency provides a remedy

for the well-known interaction of weather and IMC

conditions with spatial disorientation. The sharp

reduction in the proportion of spatial disorientation

fatal accidents which included "continued flight into

adverse weather" may reflect the greater ability of

pilots to handle these weather conditions because of
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their instrument training. Another possibility is an

improvement in pilot decision-making regarding the

advisability of flight into weather.

Other potential positive influences include:

(i) the FAA's Accident Prevention Program and the

Pilot Proficiency Award Program (Wings) (5)

which have recorded increasing participation by

pilots in recent years. Of particular relevance are

the "Back to Basics" seminars introduced in 1986

as part ofthe Accident Prevention Program; these

seminars specifically address the 12 most prevalent causal factors in aviation accidents.

(ii) the educational material and vertigon training

provided by the Civil Aeromedical Institute's

Aeromedical Education Division at air shows

and accident prevention classes around the

country. The vertigon (the newest version is

called Gyro-I) provides an impressive spatial

disorientation experience in a safe, groundbased device and specifically promotes the need

for instrument proficiency in IMC and weather

conditions. The device has been "ridden" by thousands of pilots since its introduction in 1970.

CONCLUSION

The proportion of fatal general aviation accidents

attributed to spatial disorientation has declined significantly. Along with that decline has been a large

reduction in the proportion ofspatial disorientation

accidents that were associated with "continuing flight

into adverse weather." The relative incidence ofIMC

conditions in those accidents has not changed.

Improvements in the accident rate for spatial disorientation appears distally related to general reductions in flight hours, total accidents, and fatal accidents

and more proximally related to an increase in the

. proportion of pilots with instrument ratings, FAA

training programs, and improved decision-making on

the part of general aviation pilots.

REFERENCES

1. Canfield, D. Alcohol Related Accidents, 1977-

1994. Personal communication.

2. Collins, W.E. Effective approaches to disorientation familiarization for aviation personnel. FAA

OAM Report No. 78-13, 1978.

3. Department of Transportation, Federal Aviation

Administration, 1992. Aeromedical Certification Statistical Handbook, 1992. Civil Aeromedical Institute, Oklahoma City, OK.

4. Department of Transportation, Federal Aviation

Administration, 1981. Aeromedical Certification Statistical Handbook, 1981. Civil Aeromedical Institute, Oklahoma City, OK.

5. Department of Transportation, Federal Aviation

Administration, 1991. Pilot Proficiency Award

Program, Advisory Circular No. 61-91F, (AFS20), March 6, 1991, Washington, DC.

6. Department of Transportation, Federal Aviation

Administration. U.S. Civil Airmen Statistics:

Calendar Year 1981. Washington, DC.

7. Department of Transportation, Federal Aviation

Administration. U.S. Civil Airmen Statistics:

Calendar year 1991. Washington, DC.

8. Department of Transportation, Federal Aviation

Administration. U.S. Civil Airmen Statistics:

Calendar Year 1992. Washington, DC.

9. Gillingham, K.K. and Wolfe, J.W. Spatial orientation in flight. USAFSAM-TR-85-31. USAF

School ofAerospace Medicine, Brooks AFB, TX,

1985.

10. Kirkham, W.R., Collins, W.E., Grape, P.M.,

Simpson, J.M., and Wallace, T.F. Spatial disorientation in general aviation accidents. FAA OAM

Report No. 78-13, 1978.

11. Matthews, R. GA accidents, fatalities, and rates:

1973-1994. FAA Office ofAviation Safety, Washington, DC, 1995.

12. Mortimer, R.G. General aviation airplane accidents involving spatial disorientation. In Vol. I:

Proceedings ofthe Human Factors and Ergonomics Society 39B Annual Meeting, pp. 25-29, Santa

Monica, California, 1995.

12

&U.S. GOVERNMENT PRINTING OFFICE: 1996 - 760-082/40005