Risk
Factors for Pilot Fatalities in General
Aviation Airplane Crash Landings
Paul
S. Rostykus, MD, MPH; Peter Cummings, MD,
MPH; Beth A. Mueller, DrPH
Context.
Most
pilots survive airplane crash landings in
small airplanes. Factors associated with
pilot death have not been well studied.
Objective. To
identify factors associated with
fatalities in general aviation airplane
crash landings.
Design. Case-control
study.
Setting. The
United States.
Subjects. All
pilots in general aviation crash landings
of airplanes with 10 seats or fewer, from
1983 through 1992.
Main Outcome Measure. Pilot
death.
Results. Pilots
died in 437 (5.2%) of 8411 crash landings.
A fire or explosion on the ground was
strongly associated with pilot death
(relative risk [RR], 20.4; 95% confidence
interval [CI], 15.5-26.9), adjusted for
pilot age, pilot flight hours, type of
landing gear, and the filing of an
instrument flight plan. Pilots who failed
to use both lap belt and shoulder harness
were more likely to die (adjusted RR, 6.8;
95% CI, 1.8-25.5), as were those who used
only the lap belt (adjusted RR, 1.7; 95%
CI, 1.3-2.2), compared with pilots who
used both restraints.
Conclusion. Pilots
may be able to reduce their risk of death
in a crash landing by using lap and
shoulder restraints.
JAMA. 1998;280:997-999
CIVIL (nonmilitary) flights are
classified as either general aviation or
air carrier operations. Air carrier
operations include passenger or cargo
transports for hire. General aviation
comprises recreational flying, flight
instruction, agricultural operations,
sightseeing, and business travel flown in
a variety of aircraft of all sizes and
types, including airplanes, helicopters,
balloons, and gliders. The majority of
civil aviation crashes, deaths, and
injuries are attributed to general
aviation operations.
Although general aviation airplane
crashes typically generate much media
coverage, they are infrequent occurrences.
In 1992 there were 39.6 million flight
departures and 2075 crashes.
1
In 78% of the crashes there were no deaths
and in 68% there were no injuries.2
Airplanes are designed with features that
can dissipate the kinetic energy of the
occupants and minimize injury in the event
of a crash landing. If a crash landing is
necessary, pilots are taught to keep the
plane under control, to land in an upright
position at the slowest possible speed,
and to avoid obstacles as much as
possible.
We examined data from a large number of
general aviation airplane crash landings
to identify pilot, airplane,
environmental, and crash factors
associated with pilot fatalities and to
estimate the relative risk (RR) of a pilot
fatality associated with these factors
after adjusting for potential confounders.
Methods
We analyzed data from computer tapes
containing the standardized findings of
National Transportation Safety Board
investigations of airplane accidents and
incidents. These tapes included data on
crashes only if they had occurred during
landing or takeoff and involved loss of
engine power, which we defined as crash
landings. Such events often involve an
attempt at a controlled landing. Thus, we
attempted to eliminate crashes where the
airplane hit a mountain, was torn apart in
a thunderstorm, or where aerobatics or
low-altitude cruise flight may have
occurred.
Crash landings in this study occurred
during 1983 through 1992 and were severe
enough to result in serious injury or
death within 30 days of the crash landing
to a pilot or passenger or caused
substantial damage to the airplane. Damage
to the wings, fuselage, rudder, elevators,
or cockpit that adversely affected the
ability of a crashed airplane to fly and
would usually require repair or
replacement is defined as substantial by
the National Transportation Safety Board
regulations.3
In contrast, damage to an airplane's
propeller, landing gear, or wing tips,
dents or small holes in the plane's skin,
or engine failure are considered minor.
A serious injury is defined as
one that results in a hospitalization of
more than 48 hours' duration; fractures
(except simple ones of the fingers, toes,
or nose); internal organ damage; severe
nerve, tendon, or muscle damage or
bleeding; or a significant second- or
third-degree burn. Only airplanes with 10
seats or fewer (98.8% of all the airplane
crashes) were selected because they
represent most general aviation activity
and have different characteristics from
other types of aircraft, ie, helicopters,
gliders, balloons, or larger airplanes.
Cases were defined as crash
landings in which the pilot died, while controls
were defined as crash landings in which
the pilot survived. Pilot, airplane,
environment, and crash variables related
to the event were categorized according to
Federal Aviation Administration
regulations,4
National Transportation Safety Board
regulations,5
or to the standardized reporting
categories of National Transportation
Safety Board accident and incident
investigations.6
Exposure to flying was defined
as pilot flight hours, ie, the total time
a pilot had flown any aircraft. The biennial
flight review is a Federal Aviation
Administration requirement that all pilots
receive theoretical and practical flight
training with an instructor at least every
2 years.7
Whether or not an instrument flight
rules flight plan was filed was used to
indicate a potentially high-risk flight
condition. An instrument flight rules
flight plan is required whenever the
flight is under instrument control, takes
place 5400 m (18000 ft) or more above mean
sea level, or when instrument flight rules
are to be followed, which may be due to
weather conditions or pilot preference.
Logistic regression was used to adjust
for the effects of potential confounders.8
Only variables for which the data were at
least 90% complete and might be logically
related to pilot death were examined.
Adjustments were made only for variables
that altered the risk estimates by at
least 10%. Odds ratios, estimated by the
maximum-likelihood method, were used to
approximate RRs and were adjusted for
pilot age, pilot flight time, airplane
landing gear category, and the filing of
an instrument flight plan. Other variables
examined, but not adjusted for, included
pilot characteristics of sex, principal
profession, certification, airplane
rating, and medical certificate; airplane
characteristics of certificated maximum
gross weight, engine horsepower greater
than 200, airplane hours of use, and
whether or not the airplane was owned by
the pilot; and environmental and crash
characteristics of instrument
meteorological conditions, night time,
number of occupants, and flight purpose.
Results
Study Crashes
There were 8411 eligible crash landings
during 1983 through 1992; the number of
crash landings decreased from 1235 in 1983
to 681 in 1992. One third of the crash
landings occurred in the summer, one
quarter in the spring, one fifth in the
fall, and one fifth in the winter. Most
crash landings occurred in daylight
(85.1%), with no restriction of visibility
(88.7%) and no weather precipitation
(94.2%). A pilot fatality occurred in 437
(5.2%) of the crash landings. In 69.1% of
the crash landings there was no pilot
injury reported, a minor injury in 17.2%,
and a serious injury in 8.3%. The airplane
was destroyed in 15.2% of the crash
landings, suffered substantial damage in
84.6%, minor damage in 0.1%, and no damage
in 0.1%.
Relative risks were adjusted for pilot
age, pilot flight hours, airplane landing
gear type, and the filing of an instrument
flight plan, except that the estimates for
each of these 4 variables were adjusted
only for the other 3 variables. Relative
risk estimates showed little change with
further adjustment for other variables.
Crash Characteristics
A fatal pilot injury was most strongly
associated with destruction of the
airplane (RR, 42.6) or an airplane fire or
explosion on the ground (RR, 20.4) (Table
1). Failure to use both a lap belt and
shoulder harness and failure to use a
shoulder harness were associated with an
increased RR of death compared with use of
both a lap belt and shoulder harness (RR,
6.8 and 1.7, respectively). The RR of
pilot death was also increased if the
crash site was not on an airport or
airstrip (RR, 3.2).
Airplane Characteristics
The RR of pilot death in an airplane with
retractable tricycle landing gear was
about twice that in one with fixed
tricycle landing gear (RR, 2.2).
Multiengine planes were associated with an
elevated RR of pilot death (RR, 1.9).
Pilot Characteristics
Older pilots were more likely to die; for
the 11% of pilots aged 60 years or older,
the RR of death was 2.9 (95% confidence
interval [CI], 1.7-4.9); for the 19% of
pilots aged 50 to 59 years, the RR for
death was 1.9 (95% CI, 1.1-3.2), compared
with the 6.8% of pilots younger than 25
years. The RR of death was twice as great
among pilots without a current biennial
flight review, a requirement established
to attempt to ensure periodic pilot flight
training.
Comment
We found that general aviation airplane
crash landings were usually survivable,
with pilot fatalities occurring in only 5%
of the crashes we examined.
The increased risk of fatal injury
associated with failure to use restraining
belts is consistent with other studies of
both motor vehicle and aircraft crashes.9,
10 Federal
Aviation Administration regulations
require that restraints be used during
takeoff and landing,11
and it is possible that some pilots who
survived may falsely claim that they used
restraints; restraint use by fatally
injured pilots might be less likely to
suffer from this bias. If this occurred,
it would exaggerate the strength of the
association that we found when we compared
pilots who used no restraints with those
who used both lap belts and shoulder
harnesses. However, this should not
explain the difference in survival when we
compared pilots who used lap belts only
with those who used both lap and shoulder
belts, since both types of restraints meet
the legal requirements.
Our finding that crashes that occurred
off an airport or airstrip were more
deadly seems plausible, due to the
obstructions that would be encountered in
many such landings. The increased RR of
death associated with destruction of the
airplane was expected because of the large
amount of kinetic energy that is involved
in such a crash. We found that the type of
landing gear best controlled for airplane
size characteristics of certificated
maximum gross weight, engine horsepower,
number of engines, and type of landing
gear. The presence of multiple engines may
increase the risk of death because planes
with more than 1 engine have to land at a
higher velocity, resulting in the
potential for transferring more energy to
the occupants during a crash landing. Some
of the increase in mortality associated
with fire or explosion may reflect more
forceful crashes that might have been
lethal even without thermal or blast
injuries.
The reasons for the association of a
pilot death with some of the other factors
examined are less apparent. The increased
risk of pilot death associated with
airplanes that had more than 1 engine or
had retractable tricycle landing gear may
be related to flight complexity. We
adjusted for the filing of an instrument
flight plan as a surrogate measure of
flight complexity. The filing of an
instrument flight rules flight plan, which
may be done because of flight conditions
or for pilot convenience, does not
necessarily describe flight complexity.
Other measures of flight complexity, such
as total duration of flight or weather
conditions during flight, were not
available in the data. These measures
might be related to pilot fatigue and
therefore might affect the ability of a
pilot to cope with a crash landing. The
lack of a current biennial flight review,
associated with a 2-fold risk of pilot
death, may indicate pilots lacking the
skills needed for a crash landing or
pilots prone to risk-taking behavior.
Previous analyses of aviation crashes
have examined a number of risk factors for
aircraft crashes.12
A recent investigation of commuter and air
taxi aircraft crashes found that the
characteristics of multiengine aircraft,
off-airport crash site, night flights,
instrument meteorological conditions,
nonuse of shoulder restraints, and fire or
explosion after the crash were associated
with a greater risk of pilot fatality,
although pilot age, sex, and flight
experience were not.10
Some of the risk factors identified are
more amenable to change than others.
Certain characteristics associated with
fatal pilot injury during crash landings,
such as travel in airplanes that land at a
high velocity, have multiple engines or
retractable tricycle landing gear, or
travel in complex flight conditions may be
difficult to alter. Stricter enforcement
of the Federal Aviation Administration's
requirement for a biennial flight review
might decrease the likelihood of pilot
death in some crash landings. Federal
Aviation Administration regulations
require that starting in 1978, new
aircraft must have shoulder harnesses for
pilots as well as seat belts13;
however, a large proportion of general
aviation aircraft were manufactured before
that year, as the average date of aircraft
manufacture is 1969.14
Retrofitting restraints is technically a
fairly easy process but costs $300 to $800
per seat. Pilots who wish to reduce their
risk of death in a crash landing should
ensure that their airplanes are equipped
with lap and shoulder restraints.
Author/Article
Information
From the Department of Epidemiology,
University of Washington School of Public
Health and Community Medicine (Drs
Rostykus, Cummings, and Mueller); and the
Harborview Injury Prevention and Research
Center, University of Washington (Drs
Cummings and Mueller), Seattle. Dr
Rostykus is now with the Emergency
Department, Ashland Community Hospital,
Ashland, Ore.
Corresponding author: Paul S. Rostykus,
MD, MPH, 132 8th St, Ashland, OR 97520
(e-mail: sherpa@mind.net).
REFERENCES
1.
Aircraft Owners and Pilots Association.
AOPA's 1994 Aviation Fact Card.
Frederick, Md: Aircraft Owners and Pilots
Association; 1994.
2.
National Transportation Safety Board.
Annual Review of Aircraft Accident
Data; U.S. General Aviation; Calendar Year
1992.
Washington, DC: National Transportation
Safety Board; 1994. Document
NTSB/ARG-94/02.
3.
Definitions, 49 CFR §830.2 (1991).
4.
Federal Aviation Regulations, 14 CFR
(1992).
5.
National Transportation Safety Board
Regulations, 49 CFR (1991).
6.
National Transportation Safety Board.
Factual Aviation Report, NTSB Form
6120.4.
Washington, DC: National Transportation
Safety Board; 1993.
7.
Flight Review, 14 CFR §61.56 (1992).
8.
Breslow NE, Day NE.
Statistical Methods in Cancer Research,
I: The Analysis of Case-Control Studies.
Lyon, France: International Agency for
Research on Cancer; 1980.
9.
Baker SP, O'Neill B, et al.
The Injury Fact Book.
Lexington, Mass: Lexington Books; 1984.
10.
Li G, Baker SP.
Crashes of commuter aircraft and air
taxis: what determines survival?
J Occup Med.
1993;35:1244-1249.
MEDLINE
11.
Use of safety belts, shoulder harnesses
and child restraint systems, 14 CFR
§61.107, §91.107 (1992).
12.
Li G.
Pilot-related factors in aircraft crashes:
a review of epidemiologic studies.
Aviat Space Environ Med.
1994;65:944-952.
MEDLINE
13.
Powered civil aircraft with standard
category U.S. airworthiness certificates:
instrument and equipment requirements, 14
CFR §91.205 (1992).
14.
General Aviation Manufacturers
Association.
General Aviation Statistical Databook.
Washington, DC: General Aviation
Manufacturers Association; 1997.
