*MOTA OPIS OT ‘UIE “eT TENT

12

Appendix


attachment. A clamp of this type can be centered
behind the seated occupant if a double over-the-
shoulder restraint belt system is used and at-
tached to a single tie-down. In addition, dual
clamps can be properly spaced to connect each
belt separately if desired.

In the event a single diagonal shoulder belt is
chosen, excellent side attachments can be made by
utilizing the vertical frame posts formed at the
aft edge of each door (indicated by the black
arrow). These posts with circular cutouts form
a reliable attachment location with the use of
double plates bolted over the uppermost hole.
Rectangular shaped plates extending beyond the
edges of the cutout increase the structural
strength, and when bolted together through the
cutout center by an eyebolt, provide a convenient
ring attachment.

PIPER APACHE

Since this aircraft is basically a 6-place con-
figuration, a selection of three locations for re-
straint attachments was made, one each for the
forward, middle, and rear seats. In this type
configuration the number of usable locations is
decreased since overhead attachments for a for-
ward seat would possibly interfere with a rear
seat occupant. Therefore, ‘all attachment loca-
tions selected were upper side structures. In
Figs. 2 and 4 the outlined areas marked for
reference to Fig. 3 illustrate the intersection of
vertical and horizontal frame members which
form the frame of a window and door on the
right side and the partition between windows on
the left side. A triangular plate with attached
eyebolt (Fig. 3) secured to the intersecting frame
members by a series of sheet metal screws, can
provide a usable tie-down for both front row
seats. One additional location for the left front
seat is indicated by the white arrow in Fig. 4.
This structural partition separating the front and
rear windows can accommodate a “U” clamp at-
tachment, having the greatest structural strength
at the upper end.

Suitable tie-down points for the middle row of
seats are located on the rear, vertical portion of
the aft window frame as indicated by Fig. 5.
The use of a “U” clamp at a point just below the
intersection of the window and vertical support
frames can provide a satisfactory restraint tie-
down.

The welded tube frame that forms the rear
cabin boundary can be utilized as an attachment
location for the rear row of seats. The inter-
section of these tubes at the upper rear corners
(outlined in Fig. 2 and demonstrated in Fig. 6)
can be used to secure restraint connecting devices
by loops of steel cable or fitted steel rings.

ERCOUPE

This two-seated configuration has a number of
recommended structural locations for restraint
tie-down. In Figs. 7 and 8 a center line location
is outlined and one example of a tie-down is
illustrated. The use of this location requires
that a flat mounting plate be secured by one of
two methods to the wide center structure sepa-
rating the rear windows. The first, using a single
eyebolt, would penetrate the internal mounting
plate, the skin, and an external plate to distribute
the loads over this area. The eyebolt would serve
as the attachment device. Although this type of
installation would require some modification, it
may be advantageous or desirable for use. The
other method of mounting, requiring no modifi-
cation, would use a series of sheet metal screws
around the plate edges. An eyebolt or ring
welded to the plate surface would provide a con-
venient attachment point.

Side locations can also be used as indicated in
Figs. 9 and 10. They would, however, require
pentration of the skin with external backup plates
for mounting. The mounting technique is essen-
tially the same as in the center post situation. An
example of this tie-down demonstrated in Fig. 9
shows the eyebolt as both the mounting bolt and
attachment ring.

The remaining sites of attachment (Figs. 11
and 12) are located on a single horizontal struc-
ture to which the forward edge of the rear deck
is secured. This structure passes from side to
side, providing an infinite number of sites for
attachment devices. Since the structure is a single
thickness preformed channel, additional stiffening
is needed to provide adequate strength. This
structure can be strengthened by inserting a rigid
aluminum bar to fill the channel. A “U” type
clamp can then be fitted over the downward pro-
jection for selected attachment positions.

BEECH MODEL B

This aircraft configuration has two rows of
seats and all recommended attachments are lo-
cated on the frame structure of the rear window.



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“MOTA OPIS 1USY : equiooswy,

“SE aun

16

Appendix


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Appendix


APPENDIX.

“BUSSER)

“[ aang



In Fig. 18 the outlined areas indicate two possible
sites of restraint attachment. Each of these areas,
shown individually in Figs. 14 and 15, demon-
strates an example of a feasible restraint attach-
ment. Observe in Figs. 13 and 14 that a small
circular plate is indicated and was used as a point
of attachment when a steel ring was welded to its
surface. This plate, as standard equipment in
the aircraft, is normally held in place by two
machine screws and provides a readymade mount-
ing site requiring no modification to the structure.
These plates are available for use on both the
right and left sides of the cabin and provide
reliable attachment points for diagonal type re-
straint belts.

In Figs. 13 and 15 the outlined area suggests
the use of the window partition structure for
restraint attachment. The inboard projecting
ridge of this partition forms an excellent tie-
down location. A metal plate, bent to fit around
the back side of the ridge and project forward,
was held in place by sheet metal screws. This
location is not recommended for the right side,
since it would create a hazard to passenger move-
ments through the adjacent door.

The best rear seat attachment locations were
found to be on the rear window frame indicated
by Figs. 16 and 17. Again, a metal plate bent to
conform to the frame contour with a mounted
attachment ring is used. This particular plate
is held in place by sheet metal screws.

LUSCOMBE SEDAN

Two structural locations for upper restraint
tie-down have been selected for recommendation.
Both can utilize the “U” type clamp without any
modification. Similar to the wing support struc-

ture in the Cessna configuration, this aircraft has
a continuous frame member passing along the
overhead from side to side which does not form
a closed and rigid channel. Selected channel
areas should be filled with metal plates to pro-
vide a solid base for clamp attachment. The
intersection of this structure and the vertical
door frame is structurally sound for restraint use
(Fig. 18). The other recommended location (Fig.
19) is the cabin frame member that intersects and
terminates at the upper surface of the rear win-
dow frame. The “U” type clamp when fitted to
this projecting structure is a reliable attachment
point.

IV. Summary.

Accident histories reveal that serious and fatal
injuries are occurring in general aviation aircraft
because of inadequate or incomplete body re-
straint. Specifically, the use of only a seat belt
cannot provide adequate protection to a seated
occupant, since the upper body components (e.g.
head) are free to move during abrupt decelera-
tions and strike surrounding structures.

Five in-service aircraft were dynamically tested
to determine the feasibility of restraint installa-
tion and to recommend structural locations and
methods for restraint attachment. Specific rec-
ommendations for these tested aircraft are con-
sidered valid and realistic under conditions of
abrupt deceleration peaks in excess of 20g’s.

These recommendations have been provided for
use by all individuals and organizations seeking
realistic solutions for improved personal protec-
tion. In the interest of acquiring and maintain-
ing adequate safety standards, additional studies
of this type to include all in-service aircraft must
be accomplished.


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“AOTA OPIS 143TH

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Appendix:



AM 66-33

RECOMMENDATIONS FOR SHOULDER RESTRAINT
INSTALLATION IN GENERAL AVIATION AIRCRAFT

Joseph W. Young, A.M.

Approved by Released by
Le. (Usege€ mo
J. Rosert Drie, M.D. P. V. Smexn, M.D.
Cuter, Crviz Arromepican IwstrruTe Feperat Arr Surceon

September 1966

FEDERAL AVIATION AGENCY
Office of Aviation Medicine



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“MOTA OPIS YS] rednoomy “OT sUNOLT

10

Appendix



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Appendix



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Appendix


Oklahoma City area, that were considered usable
and available within the scope of the current
program.

Each aircraft selected was inspected to assure
a complete and intact basic cabin structure, then
mounted on the acceleration track platform. Al-
though mounting details for each individual air-
craft varied, all were secured to the platform by
a system of adjustable tie-down cables and cradle
blocks, when necessary, to stablize the structure.

Concurrently, a seat was installed in a selected
position and a seat belt and both shoulder belt
configurations were mounted so they could be
efficiently interchanged in successive test runs
without removing the dummy and seat. <A test
dummy was then placed in the prepared aircraft
and secured by the seat belt in a normal sitting
position. Shoulder restraint belts were placed
over the appropriate body areas, extended over
the shoulders and aligned with structural sites
selected for attachment. At this time, all possi-
ble combinations of restraint configurations and
attachment points were observed and each com-
bination found acceptable was scheduled for dy-
namic testing.

As each potential attachment location was se-
lected for testing, a detailed examination of the
structural site was made to determine the most
efficient and reliable method of mounting attach-
ment hardware. A selection of two basic attach-
ment devices, requiring no structural modifica-
tion, was made. The first, a simple “U” shaped
clamp with a ring connector was sized to fit over
projecting structure (supporting frames, etc.)
and held in place by set screws. This type
mounting relies on a friction-torque action re-
quiring the direction of pull by the restraint belt
to be at an approximate right angle to the sides
of the “U” clamp. The second, a surface type
mounting plate with a welded ring connector, was
held in place by either a series of sheet metal
screws or machine screws with existing threaded
holes in the structure, and was sized and shaped
to fit the contoured surface. Both methods rely
primarily on attachment to the internal structure
without external penetration.

Every possible combination of standard seat
location, restraint configuration, and attachment
site was then subjected to abrupt deceleration
forces to determine structural integrity. All
tests were conducted under conditions of decelera-
tion levels in excess of 20g’s and shoulder belt

loads (single and double) greater than 500
pounds.

The facility for these dynamic tests included
an indoor acceleration track fitted with a special
bearing mounted platform. This platform has
a useful surface area 4 feet wide and 101% feet
long to which test: structures were secured.

The energy for accelerating this platform was
provided by dropping a suspended weight con-
nected to it by cables through a series of pulleys.
These pulleys have a mechanical advantage of 4,
thus, theoretically, the platform moved at a rate
4 times the velocity of the falling weight. When
the platform was pulled to a selected starting
position, the weight was raised and suspended
(the potential energy). Braking action of the
accelerating platform was accomplished by a pre-
positioned stopping block connected by a cable
to a pre-set hydraulic brake system. The stop-
ping (deceleration) distance of the platform after
impacting the stopping block, was adjusted by
varying the hydraulic pressure in the pre-set
brake. This, in effect, controlled the stopping
distance to achieve certain peak deceleration
loads. An electronic timing device was installed
next to the track to record the velocity of the
accelerating platform immediately before impact.

III. Conclusions and Recommendations.
Recommendations of specific structural areas
for restraint attachment are given for each of the
five tested aircraft. Examinations of in-service
aircraft similar to those used in this study, reveal
that only small upholstery modifications are
necessary to make proper attachment installa-
tions. Each recommendation is referenced to a
series of photographic figures that illustrate these
areas and possible attachment installations. The
five aircraft used in this study include (1) Cessna
Model 140, (2) Piper Apache, (3) Ercoupe,
(4) Beech Model B, and (5) a Luscombe Sedan.

CESSNA MODEL 140

There are two primary structures in this air-
craft that can be considered as reliable tie-down
points for upper restraint belts. In Fig. 1, (All
figures, 1 through 19, are in the Appendix.) both
structures are outlined and an example of at-
tachment hardware is demonstrated. The poste-
rior wing support passing along the overhead
from side to side forms’ a continuous structural
projection (area indicated by white arrows) that
can accommodate a “U” clamp for restraint


Frieure 15. Beech: Left side view.

Fieure 14. Beech: Left side view,

18

Appendix



Appendix

Fieve 17,

Beech :

Right rear window.

15



RECOMMENDATIONS FOR SHOULDER RESTRAINT INSTALLATION
IN GENERAL AVIATION AIRCRAFT

I. Introduction.

There is a critical need for the improvement
and use of restraint systems in general aviation
aircraft. This need is indicated by the docu-
mentation of significant increases of serious and
fatal injuries sustained in potentially survivable
accidents, and occurring under unstable in-flight
conditions. Potentially survivable accidents are
classified as those accidents in which (1) the
surrounding cabin structure remains intact, with-
out serious deformation, and (2) the level of im-
pact forces is below expected human tolerances.

One of the many contributing factors of these
injuries is the direct result of using inadequate or
incomplete restraint equipment. This clearly dem-
onstrates that the current practice of using only
a seat belt to restrain vulnerable parts of the body
cannot provide the necessary protection. In the
event of sudden exposure to abrupt impact forces
or even extreme conditions of buffeting during
flight, the vulnerable portions of the body (e.g.
head and neck) are free to move as a pendulum
and impact the surrounding structures. In ad-
dition, a proper flight control function may be
impaired or impossible during a situation of
severe buffeting, if the arms and hands are used
to aid in restraining excessive body movement.

This study was designed to provide realistic
solutions of how and where to install restraint
attachments, Specific recommendations for these
installations do not require major structural
modification,

In addition, a documentary movie was prepared
for safety program lectures and discussions to
demonstrate and explain the needs and use of
restraint equipment.

Il. Discussion and Procedures.

To provide reliable and realistic solutions of
installation methods for upper body, restraint
systems (shoulder harness or belts), it is necessary
to understand the functional characteristics of
the complete system. Specifically, the belt sys-

tem should be studied with respect to its basic
configuration, relative position over the-body sur-
faces, and the spatial relationships of the attach-
ment end to the shoulder, neck, and head areas.
Most restraint systems are designed in such a
way that each individual component (belt sec-
tion) conforms and maintains a certain relation-
ship to a designated body structure or area. In
a similar manner, the attachment end of a re-
straint belt must maintain a certain relative posi-
tion (angle and spacing) to the head and neck
surfaces as it projects posteriorly or laterally over
the shoulder and away from the body. This
position must provide sufficient freedom to ac-
commodate normal body movements of the seated
occupant without head-neck contact or visual in-
terference. This demonstrates that the areas
available for restraint attachment are limited by
(1) the imposed restrictions of restraint design
features, and (2) the actual structures considered
acceptable for use.

The basic restraint configurations under con-
sideration in this study consisted of a single
diagonal chest belt and a double over-the-
shoulder belt system. These specific types were
used in the testing procedures since they represent
two primary shoulder harness configurations cur-
rently in service and available commercially. No
attempt was made to evaluate the functional
characteristics of either restraint system, except
to indicate that certain models of tested aircraft
could utilize one type of configuration more ef-
fectively due to the limitations of acceptable at-
tachment locations.

A survey of in-service general aviation air-
craft was made to determine the number and
make of basic cabin structures and variations of
each type. This information forms the primary
selection criteria to identify and describe certain
structural locations that can be considered as
potential restraint attachment points.

The survey resulted in a selection of five
wrecked aircraft, located within the immediate



ACKNOWLEDGMENTS

The author wishes to thank Mr. John J. Swearingen for his assistance in
planning and monitoring this study and for his personal direction of the
test facility design and construction. In addition, my sincere appreciation
to the technical staff of this laboratory for their support throughout all
testing procedures.

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.


vadnooig “gq qano1g

‘adnooag “TE aanorg

11

Appendix



Appendix

Figure 16. Beech: Right rear window.

4