the Lewis flight Propulsion Laboratory
of the national advisory committee for
aeronautics has investigated the
problems of survival in light airplane
accidents because this type of accident
is responsible for many of the
casualties of civil aviation it was the
purpose of this work to determine how
people are injured during such crashes
in order to obtain the desired
information on crash survival several
small tamdan to place light airplanes
were crashed a stall spin accident was
chosen for study such an accident occurs
when an airplane stalls and enters into
a spin during a landing approach the
airplane is too close to the ground to
recover from the spin a survey made by
Cornell crash injury research indicated
that this type of accident is a frequent
source of fatalities in light airplane
crashes to simulate such a crash the
axis of the crash was rotated the ground
was simulated by a mound of Earth and
the airplane ran along the ground in a
level attitude to strike the mound of
earth the mound was located so that the
airplanes left wing tip left landing
wheel and the cell would strike at the
same time in the same manner as in the
stall spin accidents that were being
simulated two dummies were installed in
the airplane the dummy in the front seat
was a standard Air Force dummy used in
the testing of parachutes in the
construction of this dummy no attempt
was made to simulate the resilience of
the human body although the mass
distribution of the component parts was
similar to that of a human being an Air
Force anthropomorphic dummy was
installed in the rear seat this dummy is
a reasonable replica of the human body
in both mass distribution and resilience
of human tissues motion pictures were
taken from various vantage points around
the crash site these motion pictures
show how the dummy passengers moved
during the crash and how the airplane
structure deforms meanwhile the
telemeter transmitting station carried
in the airplane radioed the crash loads
measured on the passengers and in
not fit the transmitted data were
recorded by a receiving station at the
crash site three crashes were made in
this investigation the airplanes were
propelled by their own power along a
runway toward the crash barrier a
slipper mounted on a monorail guided
each airplane into the barrier the speed
of the airplane at impact in the three
crashes was 60 47 and 42 miles per hour
the motion pictures obtained verify that
most of the injuries that result from
light airplane accidents are caused by
the occupant striking part of the
airplane inside the cockpit these
injuries occur in two ways when the
airplane structure collapses and strikes
the occupant this happens to the
occupant in the front seat of this model
the occupant can also be injured when he
is improperly restrained and moves from
his normal position to strike objects in
the cockpit as illustrated here by the
occupant in the rear seat the next
motion picture sequence of the 60
mile-per-hour crash shows how the front
of the airplane collapses and crushes
the dummy in the front seat now watch
the dummy in the front seat the red
liquid that obscures the airplane in the
latter part of the pictures was used to
study the fuel spillage during a crash
there is little chance that the occupant
in the front seat would survive such a
crash the lower part of the dummy was
trapped in the collapsing airplane
structure the instrument panel moved
rearward and the dummy's head hit it
with sufficient force to leave a dent
even if the estimate panel is not pushed
rearward an improperly restrain document
may hit it with his head this is
illustrated in the next motion picture
sequence of a crash which takes place at
42 miles per hour even though the
fuselage force structure was not pushed
back into the front dummies lap the
dummy struck the instrument panel
because he was restrained only by a
seatbelt and his torso was
free to move again what's the dummy in
the front seat as before the dummy in
the front seat struck the instrument
panel the neck of the dummy in the rear
seat broke because of an imperfection in
its construction injuries of this type
are not likely in an actual crash here
is the dent in the instrument panel
these results explain why the survey
conducted by quenelle crash injury
research found so many head injuries in
actual crashes this survey found that
head injuries were inflicted in
eighty-eight percent of the accidents if
an occupant is not to be injured when
wearing only a seat belt for restraint
sufficient space must be clear ahead of
the occupant to allow him to flex over
the seat belt the occupant in this
airplane was restrained by only a seat
belt the front seat and rear control
stick were removed so that there was
sufficient room for complete flexure of
the dummy's torso the torso of the dummy
moved forward and downward until the
chest contacted the thighs it is
apparent that if injuries resulting from
contact with solid structure are to be
avoided when using only a seat belt for
restraint a distance of about 45 inches
ahead of the seat must be free of any
solid objects this much of a clear space
is seldom available in an airplane this
dangerous movement is reduced to safe
values when the occupant is properly
restrained by a seatbelt and the
shoulder harness the dummy in the rear
seat in the next crash for a seat belt
and a shoulder harness this dummy moved
forward and out of his seat about eight
to ten inches the forward movement was
limited by the harness in the most
forward position the torso is about
vertical notice this action in these
slow motion pictures of the crash what's
the dummy in the rear seat
here again the Donnie lost his head due
to a weakness in the next structure of a
dummy this would not have happened to a
human occupant
if a harness is made of material that
stretches excessively the occupant may
still strike objects inside the cockpit
the harness restraining the rear dummy
in the 60 mile-per-hour crash stretched
sufficiently to allow the dummy's head
to strike the back of the dummy in the
front seat this situation was aggravated
by the collapse of the structure between
the front and rear seats this moved the
front dummy rearward again watch the
dummy in the rear seat unfortunately the
fuel missed obscured the actual impact
of the dummy's head with the front dummy
however a post-crash inspection revealed
a dent in the dummies helmet
here is the position of the dummy's head
when it struck the front dummy it has
been shown that some of the benefits of
a shoulder harness are lost if the
harness stretches excessively in the
crash if the restraining harness is to
serve its purpose it must not break in
order to tell the designer how strong to
make this harness the forces in these
traps were measured in the crashes to
obtain this information tensiometer
zeeeee were located at each end of the
seatbelt and on the common juncture of
the shoulder harness the sum of the
forces on each end of the seatbelt and
the force measured in the shoulder
harness in the 60 mile-per-hour crash
for the dummy in the rear seat are
plotted against time after the impact
with the barrier the seatbelt
restraining force has two peaks one of
four thousand pounds and a second of
3,200 pounds the major seatbelt forces
endured for about one tenth of a second
the combined pole on both shoulder
harness traps is approximately equal to
half that of the seatbelt showing that
the seatbelt supported most of the load
the restraining forces in the seatbelt
were higher when the passenger was
restrained by a seatbelt only even when
the impact speed was reduced from 60 to
47 miles per hour during the 47
mile-per-hour crash in which the dummy
was restrained only by a seatbelt peak
seatbelt forces were 4,400 pounds and
3,000 pounds as compared to a peak of
4,000 pounds for the seat belt for the
60 mile-per-hour crash seatbelts and
harness capable of withstanding these
dynamic loads can be comfortable and
light in weight to summarize the
information presented so far has shown
that injuries and crashes result one
from the cockpit collapses and the
occupant is crushed by the airplane
structure to when the seatbelt in
shoulder harness stretch excessively
under the crash loads and three when the
occupant is restrained by only a
seatbelt even if the structure remains
in
act both seatbelt and shoulder harness
are necessary in small cockpits if
serious body blows are to be avoided the
information presented here has also
indicated the loads produced in the
restraining harness during a crash even
if the occupant is properly restrained
during a crash he may still be injured
by the deceleration she encounters the
severity of the injury received from a
deceleration depends on the magnitude of
the deceleration the rate at which it
increases commonly called the rate of
onset and the duration of the
deceleration these conclusions were
reached from the work of lieutenant
colonel staff in the report entitled
human exposures to linear deceleration
in this study by staff tests were made
with human beings carefully supported by
specially designed seatbelt shoulder
harness and leg straps under such
conditions the experimenter subjected
himself to a deceleration that had a
maximum of forty seven G's the
deceleration endured 4.2 28 seconds and
had a rate of onset of 735 G's per
second the resulting injuries were minor
when the rate of onset increased from
735 to 1550 G's per second signs of
shock were observed to obtain an
indication of the injuries that may
result from the decelerations
encountered in these experimental
crashes the deceleration zuv the rear
dummies chest were measured these
decelerations had about the same
duration and the magnitudes were very
little higher than those reported by
staff a maximum deceleration of 50 G's
was measured in the rear dummies chest
in the 60 mile-per-hour crash the
maximum full of the 47 mile-per-hour
crash was 40 60 s and the maximum for
the 42 mile-per-hour crash was 32 Gees
from the standpoint of magnitude and
duration these decelerations are within
the tolerable limits established by
steps worked however the rate at which
the deceleration increases in these
light airplane crashes
buried from 2200 jeez per second for the
60 mile-per-hour crash to 950 for the 42
mile-per-hour crash it's expected that
these high rates of onset would cause
momentary unconsciousness it may be
concluded therefore that the
decelerations measured in these crashes
are not large enough to fatally injure
the occupant in the rear seat oddly
enough the deceleration of the occupant
during a crash is often higher than that
of the fuselage floor this effect is
shown in the following motion picture
sequence in which the action is slowed
to about one sixtieth of normal graphs
of the deceleration of the chest and
floor are superimposed over the motion
picture these graphs developed in phase
with the airplanes action notice that
during the period that the seatbelt and
harness stretch the dummy decelerates
less than the fuselage floor under him
during this period the dummy acquires
velocity relative to the local airplane
structure when the seatbelt and harness
stretch is complete the passenger is
decelerated rapidly to the speed of the
airplane this causes the dummy to have
larger peak decelerations than the
fuselage floor the deceleration of the
fuselage floor had a peak of 35 G's
whereas the peak for the chest was 50
G's this increase in the chest
deceleration over that of the fuselage
floor was also found in the 47
mile-per-hour crash when the dummy was
restrained only by a seatbelt this
amplification of peak decelerations
maybe even greater if the seatbelt in
shoulder harness our slack when the
crash occurs the slack and stretch in
these members may cause failure of the
seatbelt and harness as a result of the
high crash deceleration loads produced
the deceleration imposed on the occupant
and his restraints depends on the
deceleration of the fuselage floor the
deceleration of the fuselage floor in
turn depends on the strength of the
airplane structure and the distribution
of the airplane wait in the 47
mile-per-hour crash shown at about 140
eighth of normal speed notice how the
deceleration of the fuselage floor
reaches successive Peaks
every time a main structural element
supports the crash load a peak
deceleration occurs when the loaded
structure breaks the deceleration drops
the maximum deceleration of the cockpit
therefore depends directly on the
strength of the structure as long as the
cockpit has not collapsed completely
this is illustrated by a comparison of
the maximum decelerations measured in
the 60 and 47 mile-per-hour crashes with
those of the 42 mile-per-hour crash the
maximum deceleration in all cases is
about the same ranging between 26 and 33
jeans these decelerations represent the
maximum load that the airplane structure
can support the higher kinetic energy of
the higher speed crash is dissipated by
more extensive crushing of this fuselage
force structure this increase in the
crumpling of the fuselage for structure
increases the time during which the
cockpit decelerations exist the extent
to which the crumpling of the fuselage
force structure reduces the deceleration
applied to the cockpit floor can be seen
by comparing the deceleration of the
engine with that of the fuselage floor
in the 60 mile-per-hour crash notice in
the next motion picture sequence that
the engine deceleration Rises
immediately upon impact whereas the
floor deceleration Rises gradually until
extensive crumpling of the fuselage for
structure has taken place this crumpling
of the fuselage absorbs a considerable
portion of the crash energy when the
force structure has crumpled and the
load is applied directly to the fuselage
floor the engine and floor decelerate at
about the same rate the pig deceleration
of the engine was 62 jeez while the
floor had a peak of only 35 G's for this
reason it's desirable to place as much
of the airplane as possible forward of
the cockpit this arrangement has two
principal advantages first it places
much of the airplane structure in front
of the cockpit to crumple and cushion
the crash flow and second it places much
of the airplane mass
front of the cockpit by reducing the
mass behind the cockpit the load on the
cockpit structure is reduced and failure
of this structure is less likely in a
crash it may be concluded therefore that
the chances of surviving a crash are
better if both the seat belt and the
shoulder harness of proper design are
used the chances of impact survival are
also better if the airplane has much of
its structure and mass ahead of the
cockpit the information presented in
this motion picture is reported in NAC a
technical note 2991 entitled
accelerations and passenger harness
loads measured in full-scale light
airplane crashes