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Appendix

Freune A8. Seat G.

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Impact +2 was between the left and middle
seats with the seats in the upright position. Most
of the force (120g peak) was used in forcing
the seat backs to break forward. There was
little deformation of the seat structure, causing
the impact loads to be concentrated on a small
area of the head. This would have produced
fatal fractures. It is of interest that a steady
pull of only 10 to 12 pounds is needed to force
one of these seat backs forward.

Impact #3 against the center of the serving
tray in the left seat back (with the seat upright)
produced two peaks of over 100g: one when the
seat back was forced forward and the other when
the head subsequently struck the lower cross
member of the seat back. There was no de-
formation of the serving tray. Estimates of in-
jury potential presented in Table 1 are based on
@ previous report? and the area of contact of
structure with the head. For injury estimates
for the following figures, refer to Table 1.

Some seat-design engineers feel that under
actual crash conditions the “break-away” type
of seat back will fold forward from its own
momentum out of the way of the head. If this
is true, the head possibly will strike the lower
portion of the seat back or a tubular cross mem-
ber. Impact #7 simulates this condition. The
right seat back was impacted in the forward
position. In the graph for #7, the first small
peak of about 15g was produced in bending the
thin metal at the bottom of the seat before the
head made contact with the heavy tubular cross
member concealed beneath it. At that time a
very lethal, long-duration (20 milliseconds) force
of over 100g was applied to the head.

Impact #8 was against the top of the right
seat back (seat upright) at the top edge of the

serving tray. Note similarity of curves 3 and 8. .

Since the arms supporting the folding serv-
ing trays have broken off in some airline crashes
and caused serious injury, two impacts were made
on the unfolded trays of Seat A (Figure A2).
Impact #4 was centered in an area between the
Jeft and center trays, whereas impact #5 was
against the right edge of the left seat tray. The
tray support arms in both cases bent several
inches but did not fracture. The impacts pro-
duced long duration forces of about 40g or less.

In Figure A3, the dent left by the head im-
pact against the top tubular structure (Seat B)
is barely visible in the photograph. The sharp

rising 120g peak force applied to an area of not
more than 1 sq in. of the head would undoubtedly
have caused fatal injuries.

Impact #9 against the top edge of Seat C
produced a somewhat larger dent (Figure A4).
The g-force curve looks almost as severe as the
one in Figure A3; however, there is one impor-
tant difference. Since the metal did deform and
contour to the curvatures of the head, the pres-
sure in pounds per square inch on the head would
be much less than in the previous figure and the
danger of: injuries reduced accordingly.

Three impacts against Seat D in Figure A5
show that it is a fairly safe seat for head impact.
The top edge of the left seat back (test #10)
deformed 11 inches and contoured perfectly to
the head. Note that initial bending of the struc-
ture started at 20g and that the force is spread
out with a slow rise time and a peak of not
over 60g. Test +13 against the top rear surface
of, the right seat back shows a more desirable
pattern. The head did not experience over 40g;
however, test #11 against the tubular cross mem-
ber at the bottom of the right seat back produced
peak forces in excess of 80g. Throughout this
report this type of tubular structure is shown to
be very dangerous and undoubtedly causes a
large number of head and leg fractures. This
area of the seat requires additional safety-design
consideration.

Seat E in Figure A6 (mostly fabricated of
sheet aluminum) is shown by the force curves to
have very good deforming characteristics with
the exception of the lower tubular cross member,
which produced fatal impact forces of 180g.

Seat F (Figure A7) is constructed of aluminum
tubes and produced high forces during all im-
pacts. The most dangerous part of the seat, how-
ever, is the aft end of the rigid seat arm pro-
truding rearward between the seat backs. Test
#24 against one of these arms produced a peak
force of 250g.

Seat G (Figure A8), similar in construction to
that shown in Figure A4, produced low g-forces
on the upper structure but again pointed out the
danger of the rigid arm (test #30—180g).

Seat H has two heavy, square-edged, tubular
structures in the lower portion of the seat back.
Tests #31 (Figure A9) and #82 (Figure A10)
show unusually high g-forces when these rigid
structures are impacted. The top of the seat
back is also of square tubular construction and



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Appendix 8


APPENDIX

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produced 140g when impacted (#34, Figure
10).

III. Conclusions.

Impact tests against the. eight airline seats
studied show that portions of some have good de-
forming characteristics. The most lethal design
features were found to be tubular construc-
tion (round or square), nondeforming serv-
ing trays, rigid seat arms protruding rearward

. between the seats, and excessive break-over forces.
An analysis of this series of head impacts based
on earlier work? shows that 30% would have
been fatal, 80% would have produced facial frac-
tures, 97% would have rendered the passengers
unconscious, and only 8% would have produced
no injuries or unconsciousness.

This study shows that the following design
requirements are necessary to improve the crash-
safety design of seats:

a. Tubular construction should only be used
in areas where it cannot cause injury.

b, Serving trays and seat backs should be
molded of light aluminum sheet or other material
that will deform at loads less than 30g and con-
tour itself to the head and face.

c. All exposed areas should be padded with
sufficient slow-return foam to aid distribution
of the impact force over the contour of the face.

d. The forces necessary to break the seat back
forward should be reduced.

e. The lethal characteristics of seat arms
should be eliminated.

REFERENCES

1, Swearrncen, J. J., HasBroox, A. H., Snyper, R. G.,
and McFappen, H. B.: Kinematic Behavior of The
Human Body During Deceleration. CARI Report
62-18, FAA, Oklahoma City, Okla., June 1962.

2, Sweanincen, J. J.: Tolerances of The Human Face to

Crash Impact. OAM Report AM 65-20, FAA, Okla-
homa City, Okla. July 1965.

8. Studies of high speed movies taken of dummy flailing
in the 1964 FAA-AVSER crash test of a DC-7 aircraft.


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TIME IN SECONDS

Fieure A8. Seat B.

Appendix



AM 66-18

EVALUATION OF HEAD AND FACE INJURY POTENTIAL
OF CURRENT AIRLINE SEATS DURING
CRASH DECELERATIONS

John J. Swearingen, M.S.

Approved by Released by
Bild ile. [USagek 0
J. Rosert Diniz, M.D. P. V. Sreczn, M.D.
Cuter, Crvit ArroMEpIcaL InstITUTE Feprra, Am Surczon
June 1966

Office of Aviation Medicine
FEDERAL AVIATION AGENCY



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Ficure A6. Seat E.

10

Appendix


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Figure A5. Seat D.

Appendix



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Fieure 42. Seat A.

Appendix


Taste 1. Summary of estimated injury potential of airline seats in head impact,

resist fracture during impact against deformable
structures.

Impact velocities for all tests were held con-
stant at 30 ft/sec in order to compare the forces
required to deform various portions of the seats.
This is about 10 to 15 ft/sec less than may be
expected in severe but survivable crashes.*

Table 1 summarizes the author’s evaluation
of injury and state of consciousness for each
impact as applied to different parts of the face
and head. In airline crashes it is important
for the passengers to remain conscious so that
they can escape rather than be asphyxiated or
burned to death even though otherwise uninjured.

Five impacts of the dummy head were made
against Seat A at the points shown in Figure Al

(L=lethal F=fractures U=unconscious S—=safe)
Seat Test No. Forehead Zygomatic Nose Teeth Mandible
1 S U F U F U S) U F oU
2 F L F F F F
3 F L F F F F
A. _----------------- 4 s 8 U F U F U F U
5 8 8 U F U F U F U
7 iS) U F U F U F U F U
8 F U F U F U F U F U
7 s U F U F U F U F U
6 F L F F F F
10 8 F U F U 8 U F U
O..--2--------------- u s U F U F U F U F oU
13 8 s U F U 8 U F U
D..-..--------------- 9 F U F U F U F U F U
18 s s U 8 U 8 U $s U
E_..----------------- 19 s Ss U F U F U F U
20 8 F U F U F U F U
21 F L F F F U F
22 F L F F F F
23 F L F F F F
F___.-.-------------- 24 F L F F F F
25 F L F F F F
26 Ss 8 F 8 8
27 8 8 8 Ss 8
G_-.----------------- 28 8 U F U F U F U F oU
29 F U F U F U F U F oU
30 F L F F F F
31 F L F F F F
H.._----------------- 32 F U F F F F
34 F U F F F F

(Figures Al through A10 are in the Appendix.)
by numbers 1, 2, 3, 7, and 8. Corresponding “g”
time-force curves are presented. Impact #1 (on
the top of the middle seat) produced a sizeable
deformation in the soft metal structure. The
metal deformed readily and contoured to the
head, distributing the force over a large area of
the skull. The peak force was about 70g with
a slow rise time (20 milliseconds). The decelera-
tion extended over 40 milliseconds. Referring to
Figure 1, we would expect this impact to produce
no bony injury if struck by the forehead or teeth-
maxilla areas, but it would be of sufficient force to
fracture a single zygomatic (cheek bone), nose,
or mandible (jaw bone). In all five instances,
however, the passenger would be rendered un-
conscious.”


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Appendix 13



EVALUATION OF HEAD AND FACE INJURY POTENTIAL OF CURRENT
AIRLINE SEATS DURING CRASH DECELERATION

I. Introduction.

A large percentage of deaths in commercial-
airline crashes is produced as the body and lower
limbs flail around the seat belt. According to a
previous study,’ a 10-foot-diameter sphere of
clear area would be necessary to prevent a person
from striking some portion of his body against
surrounding structures. This study is concerned
primarily with head impacts that may occur
against most portions of the seats. Thirty-five

impact studies were made with an instrumented
dummy head against various portions of eight
different makes of airline seats to determine the
“g time-force parameters of metal deformation
and seat break-over.

II. Discussion.

Figure 1 reproduces summary data? showing
the tolerances of the human face and head to

Fieune 1. Summary of maximum tolerable impact forces on a padded deformable surface.

1



Qualified requestors may obtain Aviation Medical Reports from Defense Documentation
Center. The general public may purchase from Clearinghouse for Federal Scientific and
Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151


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Appendix



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57-9018

14

Appendix