SPINAL INJURIES

Each of the two persons occupying rearward
facing seats—whose seat-backs failed — sus-
tained spinal injury; one had a compression
fracture of the 6th thoracic vertebra with anter-
jor wedging; the other sustained a complete
fracture through the body of the 3rd lumbar
vertebra with involvement of the right articular
process,

Of the other two persons who sustained spinal
injury—in forward facing seats—one had
compression fractures of the 8th and 9th
thoracic vertebrae with slight anterior wedging
and the second person sustained a compression
fracture of the 11th thoracic vertebra with
anterior wedging.

RECOMMENDATION

It is recommended that no field alterations be
made to any aircraft equipment, including seats,
without first obtaining approval of the manu-
facturer or authorized engineering personnel.

1 yo i }
'



Photographs 1, 2, and 3.

One rearward facing survivor who sustained
serious spinal injury reportedly was sitting in the
position shown, looking out the window toward
the No, 1 engine at the time of impact.

Seat-back “A” failed completely at its point of
attachment to the load bearing armrest (arrow
No. 1), Seat-back “B” although not failing, went
through its complete recline range, probably
due to inadvertent operation of the recline re-
lease lever (arrow No. 2).

There are several possible means of inad-
vertently unlocking the recline mechanism; (a)
the occupant many have had the fingers of his
left hand on the release lever at the time of
impact (arrow No. 2, photo No. 1) accelera-
tion of his hand could have caused the recline
lock to disengage; or (b) if the occupant’s leg
was in the position shown in photo No. 2 (in-
stead of up over the armrest) acceleration of the
knee up against the recline release lever (arrow,
photo No. 3) many have caused inadvertent
release,



re

-
PHOTO 9
The difference of appearance of the fittings is obvious in this rear view
. of “bare” seat-back structure; however, upholstery tends to hide this
aa difference.

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PHOTO 4

The armrest adjacent to, or below, the occupant’s left was
distorted and its cast support arms were fractured (arrow,
photo No. 4) in an outward (toward the aisle) direction.

* PHOTO 5 ;
Three longitudinal tubes (arrows, Photo No. 5) that car-
ried the major vertical load imposed by the éccupant during
the impact were distorted downward. :

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‘PHOTO 2
A

PHOTO 3



PHOTO 7 , / armrest. However, this boss was found to have
been filed- off to allow clearance for insertion

cast i
The seat-back/armrest attachment fitting (alu- into the load bearing armrest.

minum alloy casting) failed in two places; (a)
at the point where it is bolted to the steel seat- . The two armrest attachment fittings shown
back, tube, and (b) at the armrest pin, . in Photo 8 are dissimilar in strength and some-
(arrows ). This fitting is not designed to support what different in ‘appearance. The one on the
the seat-back loads Yinposed in a rearward di- right (arrow No. 1) is steel and is welded to
rection; it is only designed for use with a non- __ the lefthand steel seat-back tube. The one on
load bearing armrest. It should be noted that the left (arrow No, 2) is an aluminum alloy
this fitting normally has a boss of a width casting and is’ bolted to the righthand seat-
‘Which prevents attachment to a load bearing back tube. -

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PHOTO 12

Side view of steel fitting (arrow) to which load bearing armrest (con-
taining recline mechanism) should be attached,

PHOTO 13 ; we i
. :

|

|

| oe Proper installation of armrests is shown here; load bearing armrests “A”

| and “B” are attached to steel-welded fittings (arrows No. 1 and No, 2).

| Non-load bearing armrest “C’” is-attached to aluminum alloy fitting (arrow
No. 3).

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PHOTO 10

Difference of appearance of fittings (looking toward forward side of seat-
back) can be seen easily on “bare” seat-back frame; however, upholstery
makes close inspection necessary to note difference.

PHOTO #1

Side view of fractured aluminum alloy fitting (arrow) shows sharply
. defined edges on’ fitting; load bearing armrest is not supposed to be
. attached to this fitting. .

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Of the three armrests normally installed on
these (two passenger) seats, two (2) are load
bearing units, i.e, rearward acting loads on
each seat-back are transmitted from one side

(arrows No, 1 and No. 2) of the seat-back
structure to the main seat-bottom frame through
the load bearing armrest (which also includes
the recline mechanism).

PHOTO 6

The thied armrest (not shown in photo) is sup-
posed to be a non-loa earing unit (it merely
articulates with the seat-back) and provides no
support for loads imposed against the seat-back
by, the ‘occupant. Normally, it is installed at
“as

However, in the seat shown in photo No, 6, the
load bearing armrest had been removed from
its required position in the center of the seat
and re-installed in place of a non-load bearing
armrest at position “A.” The seat-back/armrest
attachment fitting at “A” failed (arrow) during
the crash.

—5H



FAILURE OF REARWARD FACING
SEAT-BACKS AND RESULTING INJURIES
IN A SURVIVABLE TRANSPORT ACCIDENT

A. Howard Hasbrook
John C. Earley

ABSTRACT

Photographs with captions showing seat-back failures and their causes and a description
of the injuries sustained in a relatively low force transport accident are presented,

THE ACCIDENT

While making a night ILS-GCA approach, a Convair 340 struck a
shallow embankment at about 85 knots, slid across a railroad track and a
macadam road, struck another shallow embankment and slid to a gradual
stop, jyst short of the intended runway. All landing gears were collapsed
and both engines were torn free; there was no fire. \

Despite extensive damage to portions of the belly structure, the cabin
floor and fuselage remained intact with the exception of a circular tension
tear extending from the floor (at the wing's forward spar station) on both
sides up through the walls and ceiling structure.

All passenger seats remained attached to the floor fittings; however,
some of these seats, as well as the crew seats, sustained component failure.
Galley equipmiynt in the'rear of the aircraft tore free, obstructing a rear
exit a ' .

fi
Of' the twelbe occupants aboard — all of whom survived — five were
uninjured, five sustained non-dangerous injury, and two had minor injury.
Four¥of the fivg non-dangeropisly injured persons had spinal infuries — two
of these were sitting in req;
backs collapsed. '

wd facing seats (Row-No. 1), whose seat-

. 1



FOREWORD

“Murphy’s Law” says in effect that if a unit is capable of being in-
stalled in an aircraft in both a correct and an incorrect manner, sooner or
later it will be installed incorrectly, possibly with dire results.

Although the seat manufacturer designed the seats (mentioned in this
report) to thwart “Murphy’s Law,” slight dimensional changes made by
the aircraft’s operator permitted full exercise of the “Law.”

‘tn the case described here, modification of attachment fittings and in-
correct installation of several sets of armrests on rearward facing seats
rmitted failure of the seat-backs in a moderate force accident. This
ailure reduced the desired degree of occupant protection and restraint
and probably was a factor in producing the spinal injuries sustained by
several occupants of the aircraft.

A detailed report providing a complete analysis of the force vectors
and other pertinent factors involved in this accident is being prepared and
will be released at a later date.

‘



FAILURE OF REARWARD FACING
SEAT-BACKS AND RESULTING INJURIES
IN A SURVIVABLE TRANSPORT ACCIDENT

A. Howard Hasbrook
Chief, Crash Safety .

John C. Earley
Chief, Dynamics Research

FEDERAL AVIATION AGENCY
CIVIL AEROMEDICAL RESEARCH INSTITUTE
AERONAUTICAL CENTER
OKLAHOMA CITY, OKLAHOMA
April, 1962



PHOTO 14

The aluminum alloy fittings, as originally delivered with the seats, are
shown by arrows No. 1 in photos 14 and 15. The protruding boss on
the original fittings is indicated by arrows No. 2, This boss is of
sufficient width to prevent insertion‘ into a load bearing armrest (arrows
‘No. 3).

PHOTO 15

Field modification — filing — of these fittings (arrows No. 4) was ap-
parently undertaken to permit attachment to the load bearing armrests.

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