using her shoulder harness but she received lethal injuries, probably
because of her proximity to the side of the fuselage that struck the
ground. ‘The pilot survived but had multiple trauma to the head and chest.

Figure 26

His inertia reel was mounted to the sidewall of the aircraft cabin (Figure 26).

Figure 27

The inertia reel pulled free of its mounting (Figure 27). This failure
may have resulted from the heavy lateral loading imposed by the nilot on
the shoulder restraint. However, even though the inertia reel failed,
it may have provided some protection to the pilot before it failed by
reducing his impact velocity against interior structures.

16


A most difficuit restraint problem is inherent in the use of side
facing seats. During a rapid deceleration, an occupant will be unrestrained
by the seat itself and, for the most part, will depend for restraint
entirely upon the laterally applied seatbelt.

Figure 53

The aircraft shown in Figure 58 landed long and ran off the end of the
runway. The structure remained intact and one would expect that the impact
was telatively mild, which it wes; the pilot was uninjured, three of the
four other occupants had only minor injuries.

Figure 59
However, the single occupant of the side facing bench seat (Figure 59) was

seriously injured, suffering iaternal bleeding from a rupture of the liver.
During the deceleration, the eccupant's body traveled sideways toward the

33


One of the women had 4

survived 20 hours and then died of exposure.
a fracture in the

compression fracture of a Lumbar vertebra; the other
forezrm. This was a severe but survivable accident.

Figure 15

The young man in the right front seat sustained a large, somewzat blunt,
penetrating wound of the chest (Figure 15), probably caused when his upper
torso was thrown forward against an “openTM yoke (control wheel}. A shoulder
harness may have prevented this fatal injury.

Figure 16

This aircraft (Figure 16> struck relatively level ground and some
willow trees. The pilot got out, walked several miles and was then taken
to a hospital emergency room. His only injury was a bruised chest.



Figure 33

This accident in Figure 33 illustrates the value of the lapbelt ir
keeping occupants in place. The aircraft: with three persons aboard made
a downwind takeoff, failed to gain altitude and crashed on top of a building

near the airport. The occupant in a rear seat had oniy a broken finger.

Figure 34

The right seat passenger (shown in Figure 34) had a small cut above his

eye. However, the pilot was found on top of the roof, dead from e crushed
skuli. Why was there this discrepancy in injuries to the occupants?
Investigators of accidents in which there are similar disparities in injuries
should satisfy themselves as to the sources of these differences.

20



CRASHWORTHINESS: AN ILLUSTRATED COMMENTARY ON OCCUPANT SURVIVAL
IN GENERAL AVIATION ACCIDENTS

INTRODUCTT!

Airworthiness refers to an aircraft's fitness to be operated safely
in the air; crashworthiness refers to its fitness to “safely” crash--the
abiiity to protect occupants from injury during a serviveble cype accident.
In a broad sense, crashworthiness includes such considerations as maintain-
ing the structural integrity of the fuselage; attenuating the crash forces
acting on the bodies of occupants; preventing items of mass from breaking
free and becoming injury producing missiles; providing exits for the escape
of occupants after the crash; and reducing postcrash fire, submersion, and
other hazardous conditions that may be encountered in an accident.

More than 30 years ago, a crash injury research program conducted at
Cornell University (where the term crashworthiness was coined) clearly
showed that automobiles and uircraft could be modified to reduce injuries
and to improve the chances of occupant survival in many moderate to severe
accidents.

Although meaufacturers have improved the crashworthiness of automobiles,
still over 35,000 lives are lost annusily on our highways in accidents
involving automobiles, pickup trucks, and vans. Some improvements also have
been made in the crashworthiness of light aircraft, yer about 1,500 persons
ate killed annually. A third or more of these probably could be saved if

state-of-the-art crashworthiness technology were implemented to spare occupants

the hazards of the crash. Improved means of exit, prevention of fire,
increasing the impact resistance of the airframe--all could improve crash-
worthiness, but the most economical and effective way cf seving lives is to
attenuate the impact forces acting on the occupants by use of energy
absorbing seats and improved restraint systems.

Some engineers have become knowledgeable in designing and building
systems for improved crash safety. It is hoped the material in this report
will be useful in raising the consciousness of pilots, accident investigators,
end others to the value of improved crashworthiness in general aviation.



into the shoulder harness will increase the lcading on the seat as well

and impart a forward rotary motion which will put great force on the front
toliers and axles. Further complicating this seat design is the fact thet
the fuselage tends to billow out during « crash, displacing lateraliy the

seat track channels and extending the axles, so that they may more readily
bend or break under the loads.

Figure 54

Such a seat attachment failure is shown in Figure 54, by the bent and
broken seat supports (arrows). As mentioned before, failure of the seats

leads to increased occupant injuries from secondary ‘impact and is a departure
from desirable occupant packaging principles.

Figure 55

As discussed before, a seat that is rigid msy offer little
energy attenuation ~f occupant impact. Figure 55 shows ean aircraft with
an intact fuselage, yet the two occupants had severe spinal injuries—-out
ef proportion to the apparent severity of the accident. Whet caused the

.

eresh



in

:
:

Figure 28

An accident like the one shown in Figure 28 attests to the value of the
single strap diagonal upper torso restraint. This was judged to be a non-
survivable accident because the cabin structures coliapsed and partialiy
disintegrated; the pilot was killed. The occupant of the right seat, who
was wearing a shoulder harness, survived with numerous broken bones.
Apparently the shoulder harness provided protection for his head and chest,
saving him from lethal injuries.

Figure 29

The aircraft shown in Figure 29 had power failure on takeoff and
erashed into a dirt bank at relatively low velocity. One of the two
ij-year-olds in the rear seat was uninjured. The other had unexpected
internal injuries. Unrestrained cbjects in the baggege area struck the
back of the seat, driving it forward and causing the lapbelt to compress
the occupant’s abdomen. The right front seat occupant, who was not using
@ shoulder harness, received a fracture of the mandibie.



Figure 39

The failed lapbeit attachment is shown in more detail in Figure 39.

Note that it was pulled out from its anchorage. The pilot was dead from
head and neck injuries. An investigator should ask himself, "Is it
reasonable to expect the Lapbelt to hold in such an impact?" The engineer
should ask himself, "How can the system be strengthened with respect to ail
the other technical considerations that go into the design and manufacture
of an aircraft?" Since this accident, the manufacturer has strengthened the
lapbelt attachment in this aircraft model.

The belt webbing is strong; strong enough to adequately restrain occupants
in even severe crashes. It may be weakened and fail due to severe weathering,
exposure to uitraviolet radiation, chrenic abrasion, or chemical deteriora-
tion; but the hardware attachments are most likely to be the weakest part
of the restraint system.

Figure 40

A problem with restraint attachments is illustrated by the accident
in Figure 40. The engine was torn off but the cabin structure remained intact.

23



Lapbelts

In the very early days of aviation a aumber of persons were killed
when they feli from the aircraft during maneuvers or turbulence. The
obvious solution was to use a belt to strap the pilot or occupant to the
aircraft. Thus, the use of a lapbelt in aircraft was initially for security
in flight rather than for protection in a crash. Interestingly, more people
probably are spared injury in air carrier aircraft by use of lapbeits in
flight (to protect against injury in severe turbulence) than by their use
in crashes because of the rarity of air carries crashes.

The lapbelt applied to the pelvis implements the packaging principle of
applying the restraint to the strongest part of the body.

Figure 32

The person in Figure 32 was obviously held by his lapbelt as indicated by
the abrasicns of the skin over the pelvis.

In making crash injury correlations, accident investigators should
always look for bruises and abrasions left by the lapbelt or shoulder
harness--on both the dead and the living. A loose lapbeit; an improperly
positioned lapbelt; cr a seat which may bend downward or break and allow the
person to "submarine" (slide forward under the lapbelt) may cause the
lapbelt to ride high over the pelvis and compress the soft tissues within
the abdomen. If this occurs, it frequently causes internal bleeding from
tearing of blood vessels to the gut. There may also be rupture of the liver,
spleen, or bowel. A person so injured may die because he cannot be trans-
ported to a hospital in time for the required surgery or because the need
for surgery is not immediately recognized in the emergency room.

19


spinal injuries? A clue is the fact that the wing spar is a large rigid
metal tube extending through the cockpit between the floor and the seat
bottom.

Figure 56

This spar (with the seat removed} is shown in Figure 56.

A

Figure 57

Figure 57 portrays the seat installation. The seat cushion is composed of
about 3 inches of soft foam-rubber-like material and sits on a seat pan of
plywood. The seat is mounted by metal tracks right cn top of the main spar.
What degree of pretection is afforded by such an arrangement? In an acci-
dent, the downward moving lower torso “bottoms out" on the plywood and on

the rigid metai tube. The impact force is transmitted directly to the pelvis,
spine, and internal parts of the bedy. Such ea configuration provides little
or no attenuation of vertical forces.

32


the pilot to have survived this severe crash? If properly packaged he might
have survived an accident of this magnitude. Why did he receive fatal
injuries?

Figure 22

Gne possibie reason is illustrated by Figure 22. Notice that the two fuselage
tubes aft of the cockpit were bent slightly at the site where the shoulder
harness anchorage was located; the shoulder harness attachment brace broke
free at the welds, thereby denying the pilot the full protection of his upper
torso restraint. In packaging terms, the article in the package (the pilot)
was not held sufficiently immobile to prevent its movement against the inside
of the package. An observation of this type of failure might be enough to
lead to improvements in the restraint system.

Figure 23

Indeed, this was the case--the broken welds were reported to the manufacturer
who fabricated a much more substantial shoulder harness attachment bar
(Figure 23); a longer piece of metal was used, the metal wrapped around the

1g



Articles contained in the package (occupants) should be held immobilized
inside the container (cockpit or cabin) toe prevent novement (and resuitent
damage) against the inside of the package itself (Figure 6). In terms of
aircraft design, this calls for an effective restraint system that will hold
the occupant within the creshworthy cockpit/cabin du g the impact, Ideally,
the occupant should be encased in a suspended impact-resistant cocoon-iike
structure that will prolong the duration of the deceleration, thereby decreas-
ing the peak force of the impact. A modern, practical aircraft restraint
system consists of a lapbeit, a shoulder harness, and 2 seat that will
resist the force of the impact but will deform without breeking.

3. THE MEANS OF HOLDING AN OBJECT
INSIDE A SHIPPING CONTAINER MUST
TRANSMIT FORCES TC THE STRONGEST
PARTS OF THE CONTAINED OBJECTS.

“AE

Figure 7

A third principie ot packaging (Figure 7} is that the means (the
restraint system) of immobilizing the contents inside the container should
transmit forces to the strongest part of the contained article (occupant).
In this regard, the seat engages the muscularly padded bony pelvis from
below, supporting the body from vertical forces but aiso functioning to
attenuate (through friction) forward decelerative forces. The lepbeit
acts on the front and side of the pelvis, and the shouider harness acts on,
rather broadly, the shoulder(s) and the chest.

cr oe

POR Serer eres or ee

Figure 8

The cockpit of an older aircraft used for aerial application is
shown in Figure 8. Impact of the pilot with the levers and knobs shown
here--in 2 severe crash~~couvld result in fractures of bones or possibiy

in penetrating iniuries.



Figure 50

A typical failure in a cast alloy seat support is shown in Figure 50.
Although the metal is strong, it does not bend or yield progressively.
When it faiis, it fails suddenly, and potential energy absorption is lost.

Figure 51

Similarly, loading and twisting of the attachment of the seat to the track
can cause the brittle metal to fail (Figure 51) so that the seat and its
occupant are free to flaii about in the cabin.

The need for strong energy absorbing seats cannot be overemphasized.
Net often considered is the fact that, in a crash, the shoulder restraint
and the lapbelt will direct some of tle forward loading into downward
loading on the seat. Some restraint systems may depend entirely on the seat
for their basic strength.

28



Figure 44

This was an accident (Figure 44) in which there was heavy vertical
loading. The aircraft ran out of fuel and hit an overhead power line wire,
stalled, and pancaked into a wheat field. The aircraft dropped straight
down in a level attitude. None of the six occupants survived. They all
sustained severe spinal and internal injuries. Could impact attenuating
seats have prevented their deaths?

after before

Figure 45

The seats shown in Figure 45 were designed for increased impact attenuation.
The seat supports are of a tubular, ductile metal. They are designed with
an "S" (preformed bent configuration) so they wili bend without suddenly
fracturing. This has proved toe be an effective impact attenuating design
for aircraft seats.

26



Figure 2

When a seatbeit is worn, the belt will hold the peivis and keep the
lower torso from traveling forward (Figure 2). The upper torso, head, arms,
and legs will continue their forward motion. These flailing body parts may
strike the windscreen, instrument panel, fuselage structural parts, control
wheels, rudder pedals, and other components. This subjects the occupants
to impact force of high magnitude and can cause severe or fatal injuries.
The head is frequently stopped by the instrument panel, causing fractures
of the skull and facial bones, and lacerations of the brain. If the head
is stopped by impact with the interior, but the torso continues movement,
fracture or dislocation of the neck can occur, perhaps with spinal cord
involvement. The chest may impinge upon the control wheel or yoke, causing
crushing or penetrating injuries. The forward flexion of the unper torso
can be reduced to a large degree by the use of an upper torso restraint--a
shoulder harness. The legs and feet flail forward into the rudder pedals
or underneath the instrument panei. The vertical component of the decelera-
tion causes downloading on the seat which may fail the seat/floor attachments,
the seat legs or the seat pan. The floor may deform and cause seat attach-
ments te fail. In crash injury studies, it is important that the direction
of the impact and the magnitude and directions of deceierations experienced
by the occupants be investigated, reported, and analyzed to assess the
degree of protection provided by an aircraft and its restraint systems.

uae

Bre |



= ef\ &

> Forword

G. Vertical b. Forward ct
verticals

Figure 1

Crash Dynamics

Newton taught us that "Bodies in motion will remain in motion unless
acted on by an opposing force." The body mot-ion possesses energy; the
opposing force does work on the body to change its velocity.

As an aircraft crashes it stops, its motion is halted, usually over
a short distance by the opposing forces that crush, tear, bend, and
break structures. An occupant and ail other items of mass within the
aircraft will continue their motion along the initial direction of the
aircraft with the same velocity until restrained or stopped (acted on by
opposing forces) by the shoulder harness, lapbelt, and seat or by
striking interior structures.

An aircraft with little er no forward movement, such as in a flat spin,
will fall aimost vertically (Figure 12). As the aircraft comes to a hait
the structure and occupants will be subjected to decelerations over a short
distance in the opposite (upward) direction. Typically, the engine and wings
will tend to break down, the gear and lower portion of the hull will crumple,
anc the fuselage will billow out laterally. The motion of the occupants'
bodies will be stopped in a seated buttocks-to-head (vertical) direction.

When an aircraft with forward motion crashes into an chject, the
veiccity will be horizontal (Figure ib}, and the occupants will experience
front to back decelerations. in most accidenfis, occupants are subjected to
ene major deceleration. The deceleration of the occupant can be divided into
vertical and horizontal components just as can be the velocity of the aireraft
{Figure Ie).

EeLCet s

Wet ATR TEE



structural bar and welded more securely. Aliso, flanges were turned up on the
race to further strengthen it so it would resist bending.

It is desirable to have an inertia reel in restraint systems for one to
reach forward without restriction. In an accident the impact activates the
inertia locking mechanism and the reel keeps the shoulder harness straps
from playing owt, thus holding the upper torso away from the yoke and instru-
ment panel. Unfortunately, in some crashes the inertia reel has proved to be
the weakest part of the restraint system.

Figure 24

For example, Figure 24 shows an inertia reel that failed in a survivable
accident. The pilot wes severely injured but survived.

Figure 25

In the accident shown in Figure 25, the impact force was somewhat
from the right. The woman in the right front seat was said to have seen

i5



.
:

could have prevented such injury. The magnitudes of forces imposed during
a typicai severe but survivable accident of this type are very high and the
restraint system must do work on the occupant to reduce forces to a tclerable
level. An upper torso weighing SC pounds would exert a force equal to 160
pounds in a 2 G deceleration. At 10 G's, a deceleration which aimost any

. person can survive if properly restrained, the upper torso would have the
apparent weight of 800 pounds, requiring muck more work done to restrain it.
Without a restraint, the upper torse would continue forward, striking the
instrument panel and yoke. Deceleration would occur over a distance of a

; few inches, resulting in very high injury producing forces (G load) to

: the head and chest. Restraint systems--that is, seats, lapbelts, and

shoulder harnesses--shovld prevent secondary impacts in a crash and reduce
injuries.

q

Packaging of Occupants

Principles of attenuating the force of an impact on occupants have
been advocated since the early forties aud have found wide and successful
application in many modern automobiles, in agricultural airplanes, and in
several other type aircraft. De Haven, a pioneering engineer in vehicular
crashworthiness, compared the safe transportation of people in vehicles to
the application of principles used by packaging engineers.

PACKAGING PRINCIPLES OF LIGHT AIRCRAFT
DESIGN--DE HAVEN 1952 '

1. ....THE PACKAGE SHOULD NOT OPEN UP
AND SPILL ITS CONTENTS AND SHCULD NOT
COLLAPSE UNDER REASONABLE OR EXPECTED
CONDITIONS CF FORCE AND THEREBY EXPOSE
OBJECTS INSIDE IT TO DAMAGE.

Figure 5

The shipping container (cockpit or cabin) should not open up or spill
its contents (occupants) under reasonable or expected conditions of force
(Figure 5). Nor should it coliapse on the occupants. Thus, occupants
of a erashworthy aircraft shouid be surrounded by a strong envelope thet
will resist the force of the impact, but will deform slightly to attenuate
the forces generated during the crash.

2. ARTICITMS CONTAINED IN THE PACKAGE
SHOULD BL HELD AND IMMOBILIZED INSIDE
THE OUTER STRUCTURES BY--INTERIOR
PACKAGING--PREVENTS MOVEMENT AND
RESULTANT DAMAGE FROM IMPACT AGAINST
THE INSIDE OF THE PACKAGE ITSELF. :

Figure 6

‘



Figure 35

In this accident an investigator would ask “Wes the pilet wearing his lap-
beit?" Inspection of the floor of the aircraft revealed a slot (as shown
in Figure 35) where the right-hand lapbelt attachment had extended through
the carpet and was fastened to the underlying metal structures,

Figure 36

Tavestigation showed (as in Figure 36) that the lapbelt attachmert had pulled
free from its anchorage. During impact, suf. mt force was appiied to the
lapbeit (there were no shoulder harnesses) to break its attachment end the
pilot was thrown from the aircraft onto the roof of the building. The
resulting fatal head injuries were caused by the secondary impact.

Investigators should examine such a lapbelt attachment closely, cerhaps
even under magnification, to estimate the degree of deformity of eact
to Getermine whether cor not ail the rivets or bolts had been i
Did the restraint fail due co peor manufacture? Was there
in the materials or attechment configuration?



"!

PALM ANHB3-8

AN ILLUSTRATED COMMENTARY ON CCCUPANT

nS CRASHWORTHINESS :
SURVIVAL IN GENERAL AVIATION ACCIDENTS
z—
William R. Kirkhar
S. Marlene Wicks
Donalé Lee Lowrey
s--

Civil Aeromedical Institute
Federal Aviation Administretion
Oklahome City, Ckichoma

WAL3SGI

p

a
APPIL i983
Document is available to the public through the
National Technical information Service

Springfield, Virginia 22161
as Prepared for
& BD. S. DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration
fate? fice of Aviation Medicine
cond Washington, D.C. 25591
=
Be -
Bo
fe) e OS

88 oF 08 OS



John Paul Jones, an FAA test pilct, flew this aireraft on mam
eccasions to demonstrate its features. One day he got toc close to a pele,
struck it, and the aircraft crashed inverted (Figure 11). He was able to
get out of the cockpit and wave to onlookers to assure them he was uninjured.
The crashworthiness features built into the aireraft spared him serious
injuries. The dedication note on this picture says, "50 my very good friends
at crash injury research who designed the cockpit.”

Figure 12

Modern agricultural aircraft embody many crashworthizess peinet iples
and are the nest crashworthy of general avistion aircraft. erestingly,
many of them, as shown here (Figure 12} are similar to the oz iginet Texas
A&M AG-1. Certainly, pilots engeged in such a hazardous commercial flying
activity deserve this tyre of protecti They frecuently walk away from
ts that would heve caused severe or Lethal injurie: te occupants of

accide:
other types of aircraft.

Caen’. eae

ODMH ET oor,

7.) hte

tt tet



Ee a ee

4, PACKAGING STRUCTURES MU

IST NCT BE
BRITTLE OR FRAIL, THEY SEGULD RESIST
FORCE BY YIELDING OR ABSORBING ENERGY.

Figure 9
A fourth packaging principle (Figure 9) is that the inside of the
container should be designed to cushion and distribute forces over the
maximum surface area of the contents and have yielé qualities which will

increase deceleration time. To accomplish this, some modern aeri:
application aircraft employ a relatively thin r ef ailumimm above the
instrument panel so that a broad impact mey result if the pilot’s head
or upper torso strikes the instrument panel during e crash. Also, in
these aircraft there are few protruding knobs, handles, corners, or other
rigid structures in the forward porticn cf the cockpit. A crash helmet
worn by the pilot can distribute decelerative forces over a broad area of
the head, thereby reducing the chance of skull fracture and brain damage.

Figure i0

Crashworthiness principles, as advocated by De Heven and Hasbrock,
were incorporated in the AG-i prototyse agricultural aircraft designed
and built in 1950 at Texas A&M University by Weick (Figure 10). in this
aircraft the pilot sat high above and behind the wing. There was a hopper
between the pilot and the engine. The structural members cf the cockpit
were strong--a sturdy outer package. The pilot was restrained by a lapbeit
and a double strap shoulder harness. He wore a helm there was 4
large roll of aluminum above the low positi: <1 panel—-te
distribute the force of any impact should th meve forward and

contact it during a crash.

y

*!

SORE. 5 Ln

SPARS

a



However, it also could cause lateral deflection of the vertebral column and
increase injury. Differential lateral bending of seat supports should not
be necessary in a properly designed complete restraint system.

Figure 48

Investigators noted that the six occupants of the aircraft shown in
Figure 48 received injuries out of proportion to the impact and severity
of damage te the fuselage. They also found that the cast alloy supports
of each seat had fractured (Figure 49).

Figure 49

This type of failure occurs suddenly and the occupant is subjected to
greater peak loading curing secondary impact with the cabin floor or
other structures.

28



Figure 46

The aircraft in Figure 46 failed to become airborne and during
takeoff struck a levee. The deceleration primarily was in a forward
direction and one would expect the front seat occupants to receive the
most severe injuries. On the contrary, the two occupants in the rear
seats sustained fatal injuries and the front seat occupants, who were
not using shoulder straps, had severe head injuries but survived.

Figure 47

One of the front seats is shown in Figure 47. It is of the tubular ductile
metal design previously described and it bent in a desirable manner. Although
this was primarily a forward loading accident, the bending of the seat frame
indicates there was significant downloading. An additional feature was that
the outboard seat support was of smaller diameter, and bent more readily

than the inboard support. The differential bending (lateral displacement)
could cause the occupant to roll into, rather than out of, the diagonal
shoulder harness.

27

Sy TT ee ee ee


Figure 3

A general aviation aircraft cabin structure undergoing deceleration
on an impact testing track is shown in Figure 3. This is one frame of 2
1,000-frames-per-second motion picture. The dummy, restrained by a lepbelt
only, has its head being driven intc the instrument panel by the force of
the deceleration. The unrestrained upper torso continues its forward
motion until stopped by the control wheel. This motion, resulting in the
head and chest striking forward structures, is typical of occupant dynamics
in an otherwise survivable accident--when the upper torso is not restrained.

Figure 4

The pilot shown in Figure 4 received near~fatal head and facial
injuries when his aircraft crashed; without an upper torso restraint, his

head moved forward and he was severely

ured. An upper torso restraint

&



Figure 30

This pilot's injuries illustrate the value of the shoulder harness
(Figure 30). The bandage on the head covers a large laceration. Notice
marks on his upper chest made when he struck the control wheel. He was
wearing the shoulder harness and lapbelt.

Figure 31

The abrasions around the waist and the upward abrasion in the middle of

the abdomen (Figure 31} attest tc the use of the restraint system. This

pilot made enough contact with the control wheel to abrede the skin, yet the
shoulder restraint prevented a more injurious impact. Had he not used the
upper torso restraint, he probably would have received multiple chest
injuries, compression and contusion of the heart and lungs, and possibly
lethal tears in the heart and large biood vessels. Without the shoulder
harness, this survivable accident would probably have resulted in fatal
injuries in the pilot.


Figure 61

During the deceleration, the upright seat backs were apparently
overloaded by the weight of the occupants end failed where the seat back
attached to the seat pan (Figure 61}. Note the torn hinge metal where the
back was attached. Because of this failure, the two occupants slid forward
(toward the front of the aircraft) from under their beits and sustained
fatal neck injuries in secoendery impacts. The lapbeits at the other seats
(forward facing) kept the cccupants in places. This accident illustrates
the differences in occupant dynamics and the need for careful engineering
cesign when aft facing seats are used.

Figure 62

CONCLUDING REMARKS

Since the Wright brothers showed thet
aviation has been an exhilerating experi
Christen Eagies in their exhibitien flyir

= the skies,
ness

ines

Ww
ue



and air cargo operators attest to the practical use of the skies for
commerce. Aviation will continue to grow. It is safe but we must make

it safer. To do this we should do what we can te prevent accidents.
Secondly, because accidents can and do occur, we shouid assure good crash
protection that the state-of-the art can provide. The latter can be done
by improving the crashworthiness of our aircraft. Crash injury investiga-
tion can identify areas in which improvements in crashworthiness are needed.

Figure 63

Even the Wright brothers had trouble (Figure 63). During a flight by
Orville and Lt. Self-idge, the propeller became entangled in a wing strut
cable and the plane “ell from the sky. Lt. Selfridge was the first person
to die in a United States military aircraft accident. He died of a skull
fracture when he wes thrown cut of the Wright biplane during the crash.

Figure 64

Hap Arnold (Figure 64}, noting
greater crasnworthiness protectio;

happened to Lt. Selfridge, wanted
- So he wore his West Point footbail

He
5

36


Figure 41

The pilot (Figure 41) sustained a long vertical laceration on his
forehead. Accident investigators found a corresponding vertical cieavage
in bis helmet. By absorbing most of the energy of the head impact, the
helmet probably saved this pilot's life. One experienced in crash injury
correlation would seek to explain the unusual injury pattern.

Figure 42

Examination of the aircraft revealed that the windshield was broken and

that the vertical wire cutter bar in front of the windshield was bent

forward (Figure 42). Here, then, was the most probable explanation for

the vertical cleavage in the helmet and corresponding laceration of the
pilot's scalp--the pilot had been thrown forwerd, striking the wire cutter bar
with his head. There was also a broad concavity in the instrument panel
showing that it had been struck by the pilot's chest. Analysis provided the
erash injury correlation but the question remained, "Since the pilot wore a
double shoulder harness and lapbelt, why did he trevel far enough forward
during the crash to strike forward structures in such a ‘mild’ crash?"

24


Availability odes —
‘Ac@il and/or

Preface toy | |
| \
{

Starting with Hugh De Haven, who established the Aviation Crash

Injury Research Project at Cornell University Medical School in

the forties, the crashworthiness of civil aircraft has been a subject
of interest for relatively few accident investigators and laboratory
researchers. However, there has been continuing research at the
Federal Aviation Administration (FAA) Civil Aeromedical Institute
{CAML} directed at learning about crash impact and improving postcrash
survival in civil aviation accidents. ‘Some safety groups in government
and industry also have realized the need to implement improved crash
protection for aircraft occupants. Those aware of the state-of-the-art
technology for occupant protection recegnize that the installation

and use of improved restraint systems in general aviation aircraft would
go a long way toward increasing the chance of survival in many crashes.
Because of this, the FAA has mandated the installation of upper torso
restraints (along with seatbelts) in certain categories of aircraft

and has required their use by crewmembers during takeoffs and landings.

The data and photographs used in this report were ccllected by several
accident investigaters and researchers. Some of the findings have
been used in the past in training courses for aircraft accident investi-
gators, accident prevention specialists, eviation medical examiners,
and others. In response to numerous requests for illustrative material
for use in accident prevention and pilot education, we have made the
photographs in this report (as projection slides) evailable to the
Aeromedical Education Branch of the Civil Aeromedical Institute for use
in its programs. This report, then, represents a somewhat general and
simplistic lecture on crashworthiness that may be used in conjunction
with the material in the slide sets. It aiso can stand slone as @
source material for readers with en interest in aviation safety.

As stated above, some of this material was collected by others. The
efforts of these contributors are appreciated and we hope that they
will approve of the manner of use of their findings in this report.



Figure 17

The right front seat occupant, on the other hand, was found dead in the
aircraft due to a penetrating wound of the chest and heart (Figure 17).
Although this was a survivable accident (pilot survived) the right seat
occupant died because of one specific injury. What caused such an injury?

Figure 18

When the control wheels in Figure i8 were examined, two different breaking
patterns were noted. The one on the left (pilot's) broke close to the
hub as the pilot jackknifed forward and hit the wheel. This resulted in
dliunt trauma to his chest. The right seat occupant, also jackknifed for-
ward, striking the yoke vith his chest and the yoke broke in such 4 way

that a sharp spike remained protruding from the hub. Microscopic exemination

of a brown film on this spike showed it contained red blood celis, fragments
of skin, and pieces of miscle. This "spike" portion of the control wheel

be
te



Figure 2¢

Interestingly, the shoulder harness attachment brace (Figure 20) was found
to be bent forward in the shape of a V and the welds were cracked, showing
that the force imposed by the pilot against his shoulder harness wes of
high magnitude. The shoulder harness attachment was bent and apparently
near the point of failure, but it remained intact and the pilot was spared
serious injury.

Figure 21

Another aireraft of the same make and model is shown in Figure 21. It
struck powerlines, nesed inte the ground, and then tumbled end-over-end for
about 65 feet. The engine was forced beck onto the hopper, the empennage
was torn off and the wings tern loose. The crashworthy cockpit--the outer
container--was intact. The collapse of the exterior structure showed good
energy management and the long deceleration distance indicates that the
© level should be low. Substantial tumbling of the cockpit took place efter
initia} impact with the ground and the pilot fiailed about violently in
the ccckpit. The pilet died of the injuries received. Could one expect

i3



Technical Report Documentation Pege

1. Report No. | 2. Government Accession No ] 3 Recipient s Ceralog Ne. 1
|
FAA-AM-83-8 fr: piso 192 ;
%. Title and Subntie 1S. Repo-t Dare
CRASHWORTHINESS: AN ILLUSTRATED COMMENTARY ON i APRIL 1983

OCCUPANT SURVIVAL IN GENERAL AVIATION ACCIDENTS [6 Performing Organization code

&. Performing Organization Report No

; 7. Avkor's’ Witiiam R. Kirkham, S. Marlene Wicks, and
Donald Lee Lowrey

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| 9 Performing Orgenzatien Name end Address
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12 Work Unit No + TRAIS)
FAA Civil Aeromedical Institute
P.d. Box 25082

Oklahoma City, Oklahoma 73125

TI Contreet of Gront No.

13° Type of Report ond “eriod Covered

1 42. Sponsoring Agency Name and Address
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W. \
Washington, D.C. 20591 |

1S. Supplementary Notes

This work was performed under task AM-B-83-TOX-45

Ta Sponsonag Agency Cade

6. Abstrect y

-As-the title implies, this‘is an illustrated commentary on crash survival in general
aviation aircraft. Photographs, drawings, and discussion present some basic concepts
of crash forces; mechanisms of injury to cccupants; and the roles of shoulder
harnesses, lapbelts, and seats in attenuating crash forces. Findings in a number

of accidents relate seats and restraints to the fate of the occupants.
~~

“this report is designed to inform the reader of the valve of good restraints in
erashes of general aviation aircraft. Also it will serve to orient Federai
Aviation Administration (FAA) personnel and cthers to a set of projection slides
that may be used wholly or in part in safety presentations to pilots and aviation
groups. The projection slides, duplicates of the photographs and drawings in this
report, are available from the Aeromedical Education Branch of the FAA Civil
Aeromedical Institute. 4

17. KeyWords Crashworthiness, Restraint | 18. Drstribunien Storement

Systems, Aircraft Accidents, Pilot | Document is available to the public {
Education, Occupant Survival. | through the National Technical Information
| Service, Springfield, Virginia 22161 :

|
L j

i 79. Secunty Classif. (of this report! ] 2. Security Class:t. -of thes page! i 21. No. of Foges | 22. Puce 3
: i j i H

t Unclassified } i H

; H Unclassified i 37 \ {
Form DOT F 1700.7 ‘8-72) Reproduction of compieted poge cuthorized

ifit

I GE ERD GLa fama ss.



front of the aircraft. He slid along the seat and wes restrained only by a
lapbelt, which rode up over the pelvis into the abdomen, compressing and
rupturing the liver. For best effect a lapbelt should be pulled down tightly
on the pelvis and thighs; a lease belt can move easily over the pelvis and
injure organs in the abdomen.

Many people, after an analysis of crash injuries, suggest that passenger
seats be turned around to give greater occupant protection. Since the maior
éeceleration is forward in most accidents, the seat back, by cradiing the
upper torso and head, could afford better protection; but this is true only
if the seat and seat tiedown is specifically designed for such loading. The
body with its weight and high center of gravity will put additional stress
on the seat back at its attachment to the seat pan. The seat will tend to
rotate or pitch toward the front of the aircraft; this will cause the front
seat leg attachments (aft in aircraft) to be pulled upward end the rear
(forward in aircraft) legs to be compressed downward. The dynamics are
unique; therefore, the engineering must be unique.

Figure 60

In the accident shown in Figure 60, twe of the passenger seats were
aft facing. The pilot, with five passengers aboard, failed, before flight,
to remove the pin that locked the flight controls. He attempted but was
unable to remove the pin during the takeoff roli and the airer- ~ ran off
the end of the runvey. The nose wheel went down into a smali ditch ard the
aircraft flipped forward ontc its back. The crumpled nose of the aircraft
indicates the severity of the forward impact. Of the six persons on board,
two were killed; beth died of similar neck fractures. The fatalities were
in the only aft facing seats in the aircraft. Why this difference in
injuries?

34



Figure 37

Similar questions should be asxed in an accident such
Figure 37.
landing.

as that shown in
The aircraft hit electric wires during an attempted emergency
Most of the aircraft's forward velocity was dissipated by a large
cable; the aircraft then fell upside-down to the ground.

Would one expect
the pilot to survive this fall? The cabin was intact. Would the lapbelt
hold the pilot against the seat and prevent his impact against the inverted
top of the aircraft cabin?

=

Investigation showed that the
from its attachment as shown

belt was hanging with one end free
n Figure 38.

w
ix)


NOTICE

This document is disseminated under the sponsorship of the
Department of Transportation in the interest of information
exchange. The United States Government assumes no liability
for its contents or use thereof.

:



Lapbelts attached to the seat (rather than to the aircraft frame) require
that the seat withstand the entire loading of the occupent as transmitted
by the seatbeit.

Figure 52

Figure 52 shows a seat with the shoulder harness leading through the seat
back and attaching to an inertia reel at the bottom of the seat back. For
full protection during an impact this seat back must not fold forward and
the seat suspension must bear the occupant loading into the shoulder
harness.

Figure 53

In addition, this particular restraint-seat design (Figure 53) is
complicated by the suspension of the seat on axles with roliers in
channels on the sidewall and center pedestal as depicted. The integrity
ef the seat and the restrai.t system depends on these axles and side
channels bearing the crash ioads. During an impect an occupant's loading

30



Figure 43

The answer appeared from inspection of the restraint system (Figure 43).

The lapbelt ends were attached to wire cables. The cables extended through
a bulkhead behind the pilot and were attached te the rigid aircraft frame.
The shoulder harness cable led over a pulley behind the pilot's seat and was
attached to an inertia reel. The photograph shows all three cables broken.
The lapbelt cables had wires which had broken by repeated bending during
normal use. The shoulder harness cable wires had broken in a similar manner.
Other aircraft of the same model were found to have cables with broken wires.
The manufacturer, subsequentiy, changed the cables and the configuration

of the attachments to prevent weakening of the restraint system.

Seats

One may not think of the seat as being part of the restraint systen,
yet it can be an extremely important crash energy absorber. A geod seat
absorbs vertical and, to some degree, forward icads. A crashworthy seat
should carry loads to a certain level without bending or failing; with
additional loading, it should progressively deform without breaking. This
deformation distributes forces cover a longer time period reducing the peak
loading. A seat can be too rigid. For example, if one were sitting on an
unyielding structure, such as a concrete block, when the aircraft crashed,
the block might withstand high loading generated in supporting the body,
but the crash force would be transmitted directly to the body, and serious
injuries could result. Aliso, if a seat or ite supports break suddenly during
impact, the occupant and seat will "bottom out" and decelerate abruptly on
the aircraft floor. The stopping distance is unusually short in this type of
secondary impact, and the G-loading is high, creating the potential for severe
spinai and internal injury.

25


ee ee 3 Ra.

Figure 13

The most economical and effective way te improve crashworthiness of
general aviation aircraft is to provide a strong restraint system for each
occupant. In its simplest form this includes a lapbelt fit properly to the
pelvis, 2 shoulder harness (preferably double strap) and a seat that will
yield but not break (Figure 13).

Shoulder Restraints

Daal
Figure 14
The aircraft shown in Figure 14 struck trees and fell nose down on

the side of a mountain. The two young couples were on their way to a ski
holiday. A downdraft drove the plane into a $,900 foot ridge. The pilot



had penetrated the victim's chest inflicting the lethal wound. The use of
an upper torso restraint probably could have prevented this lethal injury.
A mere ductile contrel wheel that bends but doesn't break could help
eliminate the problem illustrated in this accident.

These two accidents demonstrate the importance of upper torso restraint.
Pilots should heed such findings concerning the value of shoulder harnesses
in crashes. The FAA requirement that crewmembers wear shoulder harnesses
(if available) on takeoffs and landings is a rule designed to provide these
crews with crash safety protection during critical phases of aircraft
operations. Accident investigators should carefully document if shoulder
restraints were used and the postcrash condition of each. They, also,
should document the injuries and determine their correlation (if any)
with the performance of the restraint systems. Such observations can lead
to improved crashworthy design of occupant protection devices.

Figure 19

The agricultural aircraft in Figure 19 ran out of fuel, stalled, and
struck the ground in a 45° nosedown attitude. The plowed ground tended
to attenuate the impact forces. The pilot was provided additional stopping
distance by structural crushing, which ended with the engine displaced aft
and somewhat above the hopper. Although the pilot had conspicuous shoulder
harness and lapbelt contusions and abrasions, he sustained minor injuries.

12