Figure 30.

Figure 31.
Figure 32.
Figure 33,

Figure 34.

Figure 35.

Figure 36.

Side view of vehicle showing crushing of front end during
deceleration
Right knee impact area
Left knee impact —---

Large diameter contoured steering wheel
Collapsible control column compressed by chest:
Padded sunvisor pushed through the windshield by head
impact ~----------------------------------------------
Comparison of test results of head impact tests against
the Piper Pawnee aluminum, 1 cylinder (Case 1), and one
of the common rigid instrument panels in general aviation
aircraft (Case 2) --------------------------------------

Page
97
97
9%

98



IL. Procedure.

Eight scientists of the Protection and Survival
Laboratory received extensive training (National
Aircraft Accident Investigation School) in acci-
dent investigation and were available on im-
mediate notification, day or night, to proceed to
the crash scene in a three-state area (Oklahoma,
Texas and Arkansas) and conduct and document.
an intensive investigation to rélate injury or
death to structural impact and/or failure in ef-
fectiveness of restraint devices and determine
escape and survival after ditching. The investi-
gator made a thorough study at the crash site to
determine angles of impact by trajectory and di-
rection occupants were thrown. Force of impact
was determined by measuring deceleration dis-
tances, gouge marks, and fuselage compression.
Portions of the aircraft impacted by various
parts of the human body could usually be de-
termined from deformation of aircraft structure,
presence of bits of hair, blood and/or tissue.
Special note was made of the failure of safety
equipment, seats, and cabin integrity. All infor-
mation at the crash site was documented by de-
tailed photography, notes, and diagrams. Sur-
vivors and witnesses were interviewed to
establish altitude, attitude, and flight path of the
aircraft just before impact. Photographs were
also made of external injuries of survivors in
hospitals and external and internal trauma of
the fatally-injured during autopsy at the morgue.
Complete medical records and autopsy reports
were obtained in each case.

Three categories of aircraft crashes were
usually not investigated: (a) very minor inci-
dents—no injuries, (b) crashes in which the
aircraft completely disintegrated _ (nonsurviv-
able), and (c) crashes where the fuselage was
consumed by fire after the crash since deforma-
tion of structure from body impact and/or crash
forces could not be identified.

Concurrently, a study is being made at CAMI
to correlate injuries to structural deformation
during body impacts in automobile accidents and
to evaluate recent structural design changes re-
sulting from automotive safety standards in
terms of reduction of fatalities and injuries.

Seventy general aviation accidents have been
investigated to date. While the original plan was
to accumulate at least three times this quantity
of data, analysis of these cases has shown so

clearly the glaring lack of progress in engineer-
ing design for crash survival in general aviation
aircraft that it was decided to present the results
of these in order to make the data available to the
aviation community.

On the other hand, the automotive industry is
continually redesigning to make their product a
safer vehicle for transportation and crash sur-
vival. A continued evaluation of their efforts is
warranted.

Il. Results.

DeHaven, in 1952, stated “Safe transporta-
tion of people in any type of vehicle must of
necessity apply the practical principles which are
used by every packaging engineer to protect
goods in transit.” There are four simply basic
packaging principles:

A. The shipping container should not open up
and spill its contents or collapse on its contents
under reasonable or expected conditions of im-
pact forces.

B. Articles contained in the packages should
be held and immobilized inside the container to
prevent movement and resultant damage against
the inside of the package itself.

C. The means of immobilizing the contents in-
side the container must transmit forces to the
strongest part of the contained articles.

D. The inside of the container must be de-
signed to cushion and distribute impact forces
over maximum surface area of the contents and
have yield qualities to increase deceleration time
in case it breaks loose from its restraint.

To evaluate the extent to which general avia-
tion design engineers have succeeded to date in
applying the basic packaging principles to the
safe transportation of people in light aircraft,
27 accidents will be presented and evaluated in
terms of these packaging principles. Each acci-
dent case presented includes a brief summary of
the crash circumstances, some photographs of a
similar* or identical aircraft before impact,

*These photographs are intended to give the reader a gen-
eral impression of the aircraft before it crashed. In some
cases it was not possible to find the same year aircraft and
even if the model and year are matched, the observant reader
may note variations in control wheel and instrument panel
design, even in the same year.


AUTHOR’S COMMENT

All calculations of decelerative forces presented in this report are those
of the author and he readily concedes that the determination of exact decel-
eration “g” forces experienced by various portions of the vehicle during
different phases of its ground impact will be subject to debate and can only
be determined accurately by crash testing of numerous instrumented air-
craft. A knowledge of the exact decelerative forces in the cabin area
would be most useful for evaluating cabin integrity, seat tie-down require-
ments, and effectiveness of restraint devices. Cabin decelerations need not be
of great magnitude to produce injuries to the head and other portions of the
body flailing about during seat belt restraint as long as this deceleration is of
sufficient magnitude to overcome the strength of the human to brace against
flailing (214-3 “g”). Bodily injuries are more related to the velocity of the
body before impact, its velocity during secondary impact with the structures
inside the cabin, the yield characteristics of these structures, and the load
distribution of the impact over body area contours. During a study to
determine human facial tolerance to impact, the yield characteristics of 73
automotive dash panels were evaluated in terms of radius of curvature, “g”
force and time parameters of the impact, maximum depth and area of yield,
metal thickness, and head impact velocity. Head impact velocities were
varied from 14 to 48.7 ft./sec. and impact forces varied from 40 to 230 “g”.
Occupants producing these deformations in the actual crash vehicles should
have escaped without injury but instead many occupants received serious to
fatal head injuries since the areas of head contact were small and con-
centrated the loading above human tolerance limits. Appropriate padding
for load distribution over the contours of the head would have prevented most
of these injuries. Since certain portions of the anterior head have less toler-
ance to impact decelerations than others, and since any portion of the face
and/or forehead may be expected to contact the decelerative structure, the
author believes that engineers should design structures such that pressure
loads on the anterior head cannot exceed 100 Ibs./sq. in. during head impact
velocities of 50 ft./sec.

The author feels that these data (heretofore unpublished) may be most
useful to general aviation design engineers for redesigning light aircraft
instrument panels for better protection against head injury in future air-
craft and are being presented in this report as an appendix.

The author has combined a knowledge of structure deformation from
body impact, area of body contact, velocity of secondary impact injuries in-
flicted as related to established tolerances and strength of restraint webbings
to work backwards in establishing estimated cabin decelerations in most of
the crash cases presented in this report. These cabin decelerations, especially
at seat belt attachments, are not average decelerations but plateaus of maxi-
mum “g” forces for a duration of 20 to 100 milliseconds.



ACKNOWLEDGMENTS

The author wishes to acknowledge that all accidents presented in this
report, general aviation as well as automotive, were investigated by members
of his staff; namely: J. G. Blethrow, G. E. Braden, EB. D. Langston, D. L.
Lowrey, W. Reed, D. E. Rowlan, J. M. Simpson and T. F. Wallace. The
generous cooperation of Southwest Regional Flight Surgeon, Dr. L. C.
Barnes, Jr., representatives of the National Transportation Safety Board
from the Fort Worth Field Office, and General Aviation District Office
Inspectors in the Southwest Region has been deeply appreciated.


GENERAL AVIATION STRUCTURES DIRECTLY RESPONSIBLE
FOR TRAUMA IN CRASH DECELERATIONS

I, Introduction.

The title of this study may, at first, suggest to
the reader that this is a duplication of many re-
ports published in the past 25 years. The concept
of protecting occupants in crash circumstances
is not new. Statistics have been presented by
many authorsTM*® showing that in sudden de-
celerations the unrestrained or partially re-
strained (seat belt) occupant flails about in a
disintegrating cabin, striking various portions of
the body against objects which penetrate or
crush body structures during the “so-called”
secondary impact. The literature is full of
statistics **** showing that most deaths (75-
85%) and serious injuries in all transportation
vehicle crashes are a result of head impact.

Speaking of statistics, it is well known that
automotive deaths in the United States have
risen to an alarming figure of something over
55,000 per year and that the number of serious
injuries is more than ten times this figure.
The automotive death rate for each 100,000,000
passenger miles of travel is given as five. How-
ever, if only passenger automobiles and taxis are
included (excluding pedestrians, motorcycles,
bicycles, buses and trucks) this figure is reduced
from 5 to 2.4. On the other hand, the number of
fatalities in general aviation aircraft accidents is
only about 1,100-1,200 per year and the number
of serious injuries accompanying these deaths is
only slightly over 50% of the number of fatalities
or approximately 600.2> This comparison of
deaths and injuries in two transportation systems,
one (automotive) in which the serious injury
rate is 1000% greater than the death rate and
the other (general aviation) in which serious in-
juries are only about 50% of the death rate cer-
tainly arouses one’s curiosity and calls for some
explanation. Flight velocities of general avia-
tion aircraft are usually higher than automotive
speeds. However, most general aviation aircraft
land at speeds that are approximately the same as

those commonly found on interstate freeways.
The actual reasons for this peculiar inconsistency
will be made apparent in the text of this study.

In 1967 the National Transportation Safety
Board (NTSB) reported ** 111,000 general avia-
tion aircraft flew an estimated 21,000,000 hours.
Assuming an average flying speed of 150 miles
per hour (which is probably on the high side),
this would represent 3.15 billion miles. The same
report states 12,298 occupants were on board
6,115 aircraft involved in accidents, indicating
the average occupancy for general aviation air-
craft is two. Multiplying total miles flown by
average occupancy gives 6.3 billion or 63(100,-
000,000) passenger miles. Based on 1,100 fatali-
ties, the rate for 100 million passenger miles
(17.5) is more than seven times that for automo-
tive accidents. Again we ask, why?

The purpose of this study is to present a de-
tailed analysis of aircraft structural components
directly responsible for human trauma during
sudden deceleration and, at the same time, by a
similar study of automotive accidents compare
advances in structural design for crash protec-
tion in the two modes of transportation in order
to explain why automotive transportation is
nearly seven times safer than general aviation
aircraft today. It is hoped that this report may
stimulate the manufacturers of general aviation
aircraft to make design changes in future aircraft
to utilize some of the crash safety design prin-
ciples developed in recent years by the automo-
tive industry as well as other structural changes
that will be necessary to improve crashworthiness
of small aircraft. Studies by DeHaven, Has-
brook, Patrick, Snyder, Swearingen, Stapp,
Beeding, and others describing tolerances of the
body to impact, body kinematics, effectiveness of
restraint equipment, and injury statistics are
well known.?***



TECHNICAL REPORT STANDARD TITLE PAGE
2. Government Accession No. 3. Recipient's Catalog No.

T. Report No.
FAA-AM-71-3

4. Title and Subtitle

5, Report Date

GENERAL AVIATION STRUCTURES DIRECTLY RESPONSIBLE January 1971
FOR TRAUMA IN CRASH. DECELERATIONS 6. Performing Organization Code
7. Author’)

8. Performing Organization Report No.

John J. Swearingen, D.Av.T.

9. Performing Organization Name and Address 10. Work Unit No.

FAA Civil Aeromedical Institute
P. 0. Box 25082

Oklahoma City, Oklahoma 73125

TI. Contract or Grant No.

S

Type of Report and Period Covered

12. Sponsoring Agency Name and Address
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W. 14.
Washington, D.C. 20590

15. Supplementary Notes

i. Sponsoring Agency Code

This work was performed under task AM-A-70-PRS-37.

16. Abstract

An analytical study of general aviation accident injuries is presented. Needs
for improvement of both the crash design of the interior of the cockpit and
the structural integrity of the cockpit itself are clearly illustrated. Crash
safety design in light aircraft has fallen so far -ehind that for the automobile
that death rates per 100,000,000 passenger mies in light aircraft are at least
seven times those for automotive transportation. The author concludes, after
many detailed analyses in this study, that many p ‘tent-day general aviation
aircraft with their rigid instrument panels studdec with heavy instruments,
protruding knobs and sharp edges, along with a lack of slow-return padding and
very inadequate restraint equipment, are producing fatal or very serious
injuries during low cabin crash decelerations with some as low as 3-4 "g".
Again based on the author's calculations, it is not uncommon for light aircraft
cabins to start to disintegrate and/or collapse on the occupants if the crash
forces exceed 9 or 10 "g'', And yet, some manufacturers have produced aircraft
for aerial application that have cockpits that can withstand up to 40 "g".
Engineering design changes can sharply reduce the death and injury rate in
general aviation accidents.

7. Key Words ]78, Distribution Statement
Crash Injury, Structural Parts, Avia- Availability is unlimited. Document may
tion Accidents, Aircraft Design, be released to the National Technical
Tolerances (Physiology), Impact Shock, | Information Service, Springfield,
Head, Aircraft Seats Virginia 22151, for sale to the public.
19. Security Classif. (of this report) 20. Security Classif. (of this page) i. Ne. of Pages | 22. Price
Unclassified Unclassified 207 $3.00

Form DOT F 1700.7 (e-69)



photographs of occupant injuries, and a table
listing injuries of each occupant and the aircraft
structure responsible for the injury.*

It was the intent of the author to select in-
dividual crashes to illustrate the degree that each
of the four packaging principles is being
utilized in present-day general aviation accidents,
but since all four principles are directly involved
in each impact, it was deemed necessary to dis-
cuss each accident from a standpoint of crash
survival packaging.

The words survivable and nonsurvivable have
been used freely for a number of years to describe
aircraft accidents, but may be extremely mislead-
ing. Obviously, in accidents where the aircraft
flies into the ground at a very high velocity,
digging a huge crater in the earth and disinte-
grating into small pieces with a crash force
calculated to be 198 “g” (Case 1—1966 Beech
Baron 95C-55), or flies into a stone mountain at
full cruise velocity (328 “g” calculated) (Case
2—1956 Cessna 310D), or impacts a large tree on
the ground with sufficient force to allow the tree
to penetrate to the front edge of the front seat
(31 “g”) (Case 3—1964 Piper Cherokee PA
28-235), they would be classed as nonsurvivable
simply because a cabin structure cannot be
designed with sufficient strength to withstand
such impact forces and still be light enough to
fly. Even if such a cabin structure were feasible,
in Cases 1 and 2 the human body would not be
capable of withstanding the restraint forces. In
Case 8, the occupants could have tolerated the
restraint forces but would probably have been
fatally injured by the deep penetration of the
tree into the cockpit.

In other, less severe accidents, one may look at
the remains of the aircraft and say it was non-
survivable simply because the cabin structure
collapsed or disintegrated and, indeed, it was
probably impossible to survive the accident.
However, an analysis must be made to determine
whether the crash forces alone were sufficient to
cause a nonsurvivable accident, or whether they

*Abbreviations used in injury-structure correlation tables:
& And L. F, Left Front

© — Cervical Vertebra L. RB. Left Rear
(PF) Fatality Mult. Multiple
Hem. Hemorrhago R. F, Right Front
L% Lumbar Vertebra R.R. Right Rear
(l) Left 4R) Right

Survivor

Lac. Laceration (8)
Tr ‘Thoracic Vertebra

Lac’s. Lacerations

were of low magnitude and inadequate design of
the shipping container allowed it to collapse upon
its occupants and cause the fatalities.

In a normal landing (65 miles per hour with

- 600 feet stopping distance) the aircraft and its

occupants experience a deceleration of, about 14
“g” and the occupants have no difficulty maintain-
ing their seated posture with or without
restraint.

In Case Number 4 the pilot, flying a Piper
Cherokee PA 28-140 (1968), hooked some steel
telegraph wires and decelerated smoothly from
65 miles per hour to “0” in 55 feet. In this
instance the aircraft fuselage and occupants ex-
perienced approximately 14 “g” deceleration.
The aircraft cabin maintained its integrity and
the pilot bumped his head only slightly and
knocked off his glasses. Therefore, with only
seat belt restraint, the upper torso can be ex-
pected to jackknife forward, allowing the head
to strike the instrument panel when aircraft
deceleration forces exceed 1.5 to 2.0 “g”.

Swearingen ®* has adequately described the
kinematics of the body and the head strike areas
in numerous general aviation aircraft. Figure 1
shows head clearance area of the path taken by
the top of the head (5th to 95 percentile), when
the body jackknifes over a seat belt, superimposed
on scale size drawings of 11 popular general
aviation aircraft (A through K). The com-
posites shown in “L” indicate clearly that all the
instrument panels (vertical lines) and top of the
control wheels (circles) lie directly in the path
of the head. Figure 2 is another, more detailed
composite of the same group of aircraft showing
forward motion of the body (95th percentile)
with seat belt restraint along with ares swept out
by the head, arms, and legs during the flailing
motions that accompany crash deceleration. The
acceleration forces in these tests on unbraced
individuals were less than one “g” and yet the
head impact velocity at the point of instrument
panel impact exceeded 12 ft./sec.

Other investigators ** have shown that with
aircraft decelerations of 8 “g” with lap belt
restraint, the head strike velocity can easily reach
50 ft./sec. or more. Also, in recent tests con-
ducted by The Boeing Company at CAMI, a very
accurate study was made to determine head
strike velocity. The results confirmed those
given in Reference 56. A deceleration of 8.5 “g”
produced a head strike velocity of 53.9 ft./sec.





Case 21-1,
Case 22-1, Case 22-2, Case 22-3 __.

Case 23-1, Case 23-2, Case 23-3, Case 23-4
Case 24-1, Case 24-2, Case 24-8, Case 24-4

Case 25-1,

Case 26-1,
Case 27-1,

Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.

Figure 6.
Figure 7.

Figure 8.

Figure 9.

Figure 10.
Figure 11.

Figure 12.
Figure 13.

Figure 14.
Figure 15.

Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.

Case 21-2

Case 25-2 _.------------------.
Case 26-2, Case 26-3, Case 26-4
Case 27-2, Case 27-8, Case 27-4, Case 27-5 __-

LIST OF ILLUSTRATIONS
Minimum head clearance as related to 11 popular personal
type aircraft ____----_---------------------------------
Area of forward flailing (95th percentile) with seat belt
restraint, superimposed on scale drawings of 11 general
aviation aircraft --
Subject wearing seat belt in 1968 Cessna 150 __
Dummy with seat belt attached straight down over thighs
before crash test -_____-__-----------------------------
Position of dummy after crash test. Extreme forward
motion is allowed by improper seat belt installation .____-
Automotive accident of a calculated 3 “g” impact force ----
Automobile accident in which driver was subject to 7 “g”
forward deceleration ~...---.--_-----------------------
Automobile accident that subjected driver to 9 “g”
deceleration --
Effects on occupants in a 10.5 “g” automotive crash -
Driver impact against right door and dash in a 12 “g” in-
tersection crash -
Automobile collision of. 4 ‘g” magnitude in forward
direction
Tolerances of the human head to crash impact —_.
Full-face (maximum area) crash test exceed 300 ug”
deceleration -_-~.--_-------_--------------------------
An example of a padded dash panel in a late-model
automobile ~_-____------------------------------------
Steel ribbon design of dash structure under padding has
good yield characteristics
Automobile accident—calculated 19 “g”
19 “g” impact
20 “gy
Deceleration =22 “g”
Deceleration =23 “g”
Deceleration =23 “g” __.
Deceleration =24 “g” __
Deceleration =26 “g”
Deceleration =26 “g”
Deceleration =38 “g” __
Deceleration =42 “g”
Knee impact area in late-model automobile
Safety release bulletin—Beech Aircraft Corporation —
Trajectory of an automobile traveling at high velocity

after it ran off the freeway -....-----------------------

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105
110
114
118
120
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14
15
32
382

32
33

34

35
36

37

38
39


TABLE OF CONTENTS

ABSTRACT
ACKNOWLEDGMENTS
AUTHOR’S COMMENT
INTRODUCTION -

CRASH CASES:
Non-Survivable (Aircraft) --
Minor—2 to 7 “g” (Aircraft)
Minor—3 to 12 “g” (Automobile)
Severe—19 to 42 “g” (Automobile) -
Moderate—8 to 10 “g” (Aircraft) -.
Severe—10 to 19 “g” (Aircraft) —-.
Very Severe—50 “g” (Automobile) -
Unusual crashes (Aircraft) ----
Very Severe—40 “g” (Aircraft)
Vertical Forces (Aircraft) -

CONCLUSIONS
REFERENCES
APPENDIX --.

LISTING OF CASE PLATES (for Report AM-71-3)

Case 1-1, Case 1-2
Case 2-1, Case 2-2
Case 8-1, Case 3-2, Case 3-3
Case 4-1, Case 4-2, Case 4-3
Case 5-1, Case 5-2, Case 5-3 -
Case 6-1, Case 6-2, Case 6-3, Case 64
Case 7-1, Case 7-2, Case 7-3 -
Case 8-1, Case 8-2, Case 8-3
Case 9-1, Case 9-2 --.
Case 10-1, Case 10-2
Case 11-1, Case 11-2, Case 11-3 --.
Case 12-1, Case 12-2, Case 12-3, Case
Case 13-1, Case 138-2, Case 13-8 ----------
Case 14-1, Case 14-2,.Case 14-3, Case 14-4
Case 15-1, Case 15-2, Case 15-3, Case 15-4 -
Case 16-1, Case 16-2, Case 16-3, Case 16-4, Case 16-5, Case 16- 6 - --
Case 17-1, Case 17-2, Case 17-3 ----------.
Case 18-1, Case 18-2, Case 18-3, Case 18-4
Case 19-1, Case 19-2, Case 19-3, Case 19-4
Case 20-1, Case 20-2, Case 20-3, Case 20-4 -.

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184

BSRESSb oan