cidents during 1966, A summary breakdown of
the data follows:

Frequency of Injury in 564 Fatal
General Aviation Aircraft Accidents
Resulting in Death to 522 Pilots During
1966

Body Region

Head and Neck --- 661

Upper Extremities 420
Chest

Abdomen

Pelvis ---- - 123
Lower Extremities - 519
Massive Injuries — - 60
Burns

Again, note the preponderance of injuries to the
head and neck, the extremities, and the chest.

Head, neck, chest, and abdominal injury are
most often critical to life. Gregg and Pearson *
have shown that 76 percent of the variation in
injury severity can be attributed to the severity
of head injury. Where immediate evacuation
ig necessary, such as to avoid drowning or a
post-crash fire, an injury to the extremities can
be critical. In many instances multiple injury
is sustained, although not shown in these data.
A ten-year study by Hasbrook** reported that
roughly one-third of the 389 people killed in 913
general-aviation aircraft accidents died un-
necessarily since the cabin structure was damaged
mnly slightly. Contact of the occupant with ob-
jects or structures within the cabin caused these
fatal injuries. The conclusion was reached that
n most cases the use of a shoulder harness prob-
ibly could have saved the occupant’s life.

The Bureau of Safety of the CAB, now part
of the National Transportation Safety Board, in
. letter to the FAA dated November 3, 1964,
tated that in many instances lives have been
reedlessly lost in general-aviation aircraft acci-
lents due to the non-utilization of shoulder
iarnesses. Through October 20 of calendar year
964, $26 fatalities were recorded. Of these 826
‘atalities, the Board indicated that approxi-
nately 200 lives could have been saved.

IV. Regulations Governing the Installation
of Shoulder Harnesses in Existing Air-
craft.

Shoulder harneses or equivalent means of pro-
tection from head injury are required by the
Federal Aviation Regulations to be installed in
normal, utility, and acrobatic category airplanes
manufactured under Approved Type Certificates
applied for after September 14, 1969. Amend-
ment 23-7 to Part 23, Airworthiness Standards:
Normal, Utility, and Acrobatic Category Air-
planes (effective: September 14, 1969) specifies:

23.785 Seats and berths

(g) Each occupant must be protected from
head injury by—

(1) A safety belt and shoulder harness that
will prevent the head from contacting any in-
jurious object:

(2) A safety belt plus the elimination of any
injurious object within striking radius of the
head ; or

(3) A safety belt plus an energy absorbing
rest that will support the arms, shoulder, head
and spine.

For those aircraft owners who would like to
install shoulder harnesses in their own aircraft,
FAA Advisory Circular No. 43, 18-2, Chapter 9,
Shoulder Harness Installations, contains the in-
formation necessary for an acceptable method of
installation, The following general conditions
must be met to provide a satisfactory restraint:

1. Utilize the original seat-belt attachments
and either the original or a new belt provided
with shoulder-restraint fittings.

2. Use webbing approved per TSO-C22e for
standard seat belts.

3. Use hardware approved per TSO-C22e for
use on seat belts.

4. Secure the lower end of the shoulder re-
straint to one side of the original seat belt or
belt anchorage.

5. Secure the upper end of the shoulder re-
straint to an aft or ceiling mount attached to
primary structure independent of the seat.

6. Test the added mount by applying a load of
500 pounds forward at the shoulder point.

7. Have the completed and tested installation
approved by a General Aviation Maintenance
Inspector or an Airplane and Powerplant
Mechanic holding an Inspection Authorization.





tight lap belt can be roughly defined as a sphere
nearly ten feet in diameter. Young,’ realizing
that this much clear space could not be made
available to each passenger, made functional
comparisons of basic restraint systems and was
able to demonstrate dramatically the lessening of
the space traversed by the head when various
types of shoulder harness were worn as compared
to use of the lap belt only. He found that the
maximum forward head travel was reduced to
approximately 20 inches from the seat reference
point when using a complete double parallel
shoulder restraint system with the upper attach-
ment fixed at the midline and the lower attach-
ment continuous as a seat belt. This is compared
with a 48 inch head travel when using a lap
belt only positioned forward of the seat back
plane. The efficiency of other uper torso re-
straint systems is almost as remarkable. A sys-
tem with a single diagonal belt with both the
upper and lower attachments fixed at the sides
effectively limited head travel to less than 28
inches.

Stapp*® reported that a properly restrained
adult male is capable of tolerating 30 to 40 G
without sustaining serious injury in forward-
facing decelerations and at least 20 G in lateral
decelerations. Turnbow, et al® recommend that
restraint systems be designed to maintain their
integrity up to the force level where the oc-
cupant may be injured, but is not incapacitated
and is able to extricate himself from the
wreckage in time to avoid such post crash
hazards as fire and drowning.

Compression fractures of spinal vertebrae
have been reported as a result of eyeballs-down
(+Gz) accelerations of approximately 25 G@
sustained for approximately 100 milliseconds.
However, these fractures are not necessarily of
the nature to incapacitate the occupant and pre-
vent him from extricating himself from wreck-
age. Tolerance to vertical impact loads is greatly
reduced when the spinal column is in a flexed
position or is misaligned laterally, Since it is
possible for vertical impact loadings in light
plane crashes to exceed the longitudinal stresses,°
an important factor in tolerance to headwards
acceleration is the use of a tight shoulder harness
to hold the occupant’s shoulders tightly against
the seat back.

The human tolerance limit for eyeballs-up
(—Gz) acceleration is approximately 15 G for a
duration of 100 milliseconds.* In the limited
amount of research done on footward accelera-
tions, all restraint has been with both shoulder
harness and seat belts. Most experiments also
included a seat belt tiedown strap and the stated
tolerance is based on this configuration.

For forward-facing, eyeballs-out (—Gx) ac-
celerations, the human tolerance limit is approxi-
mately 45 G for a duration of 100 milliseconds or
25 G for 200 milliseconds.” Restraint used to
determine these limits was by means of a double
thickness, 3-inch wide shoulder harness, a seat
belt with thigh straps, and a chest belt. Some
debilitation and injuries can be expected at this
G level if less than this optimum restraint sys-
tem is used.

The human tolerance limit for rear-facing,
eyeballs-in (+Gx) acceleration has not been ac-
curately established. Obviously it is higher than
that for the forward-facing limit. The restraint
provided by a full-length seat back in this
configuration supports this assumption. Beeding
and Mosely ** reported a subject experiencing a
maximum of 83 G with a duration of 40 milli-
seconds in a backward-facing seat, However, the
subject was extremely debilitated, went intc
shock, and required on-the-scene medical treat-
ment following the test run.

Ill. Accident Investigation Findings.

De Haven? reported in a study of the pattern:
of injury of 800 survivors of light aircraft ac
cidents, that 704 of the survivors suffered heac
injury, 548 injury to the upper trunk, with 807
the next lower number, having injury to thi
lower third of the legs. A number of fatalitie:
occurred in this group of accidents, but data wa:
not presented in this study because of lack o
reliable autopsy data. It is probable that due t
the large number of head and chest injurie
among the survivors, death was most likely as
sociated with injuries to those body areas. Thi
assumption is supported by data compiled b;
Marrow * which shows head and chest injurie
responsible for 3387 of 342 fatalities in ligh
plane accidents. A recent tabulation  b;
Cierebiej and Stedman * indicates that multipl
injuries were responsible for the death of 52
pilots involved in 564 fatal general aviation ac


8, Have the approval recorded in the aircraft
log book.

V. Certain Problems with Shoulder
Harnesses

One of the most serious problems with
shoulder-harness and other restraint systems is
the difficulty in properly fitting all members of
the flying population. Injuries as a consequence
of wearing lap belts** can be attributed either
to improper wearing of the lap belt by the oc-
cupant or to improper fit (lap-belt angle is not
between 45°-55° from the horizontal and firmly
positioned over the pelvis). When the single
upper-torso belt rides along the side of the neck,
pressure or chafing can cause distinct discomfort
during normal flight operations and can create
pressure upon the nerves and blood vessels of
the neck which can be quite annoying to the user.
A belt resting against the neck can be directly
responsible for injury in a crash as demonstrated
experimentally by Snyder, et al.’ If the upper-
torso belt is positioned off the shoulder because
the upper belt attachment is too low or too far
forward relative to the seated occupant, the oc-
cupant may flex over it during a crash sequence
and slip out of it completely. He can also be
subjected to a simultaneous rotational torquing
motion which may be particularly injurious.
The optimum angle for the upper-torso belt rela-
tive to the shoulder is —5° to +80° from the
horizontal.

Even when wearing a harness that is properly
fitted, the user may have difficulty reaching cer-
tain cockpit controls unless the restraint system
incorporates an inertia reel or it is worn loosely
while in cruising flight.

The above-mentioned problems can be solved
if attention is given in the design of the re-

straint system to incorporate the maximum in
features for comfort, neatnes of appearance, ease
for storage, and ease of donning and escape.
People will use shoulder harnesses if these
criteria are met. Swearingen demonstrated this
in a study ** where over 90% of the test subjects
were motivated to utilize shoulder harnesses in
automobiles throughout a 2-year test period.
This rate contrasts with an estimated 3-5%
utilization of factory-installed shoulder harnesses
in over 10 million automobiles manufactured
since January 1, 1968.

VI. Summary of Benefits.

Research and accident investigation finding:
clearly indicate that if occupants of genera’
aviation aircraft would wear properly-designec
and installed shoulder harnesses, especially dur
ing the take-off and landing phases of flight, the
number of fatalities and major injuries from ac
cidents would be substantially reduced. It coule
be expected that more occupants would emerg
from accidents without injury, or, if injurie:
were sustained, they would be less serious. Th
survival of more people from currently “non
survivable” type accidents can be expected.

VIL.

It is concluded that if shoulder harnesses wer
installed in general aviation aircraft, consider
able benefit to the users of these harnesses woul
accrue. The user-occupant of older genera
aviation aircraft would then realize a level o
safety approaching that enjoyed by the user
occupant of normal, utility, or acrobatic categor.
eirplanes manufactured under Approved Typ
Certificates applied for after September 1+
1969.

Conclusion.


TECHNICAL REPORT STANDARD TITLE PAGE

T. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
FAA-AM-72-3
4, Title ond Subtitle 3. Report Date

February 1972

6. Performing Organization Code

THE BENEFITS OF THE USE OF SHOULDER HARNESSES IN
GENERAL AVIATION AIRCRAFT

7. Author(s) 8. Performing Organization Report No.

Joseph A. Sirkis, B.S, P.E.

9. Performing Organization Nome and Address 10. Work’ Unit No.

Office of Aviation Medicine

Federal Aviation Administration TI. Contract or Grant No.

800 Independence Avenue, S.W.

Washington, D.C. 20591 13. Type of Report and Period Covered
12. Sponsoring Agency Name and Address

Office of Aviation Medicine OAM Report

Federal Aviation Administration

800 Independence Avenue, S.W. 14. Sponsoring Agency Code

Washington, D.C. 20591

15. Supplementary Notes

16. Abstroct

The installation and use of shoulder harnesses is a practical and relatively
inexpensive solution to the problem of maintaining separation between man and
machine during an aircraft crash sequence. The addition of shoulder harness
to the tie-down chain of the general aviation aircraft occupant will increase
the probability of the user surviving a severe crash and minimize injuries
resulting from light-to-moderate crashes.

It is concluded that if shoulder harnesses were installed in all general
aviation aircraft, considerable benefit to the users of these harnesses would
accrue. The user-occupant of older general aviation aircraft would realize

a level of safety approaching that enjoyed by the user-occupant of normal,
utility, or acrobatic category airplanes manufactured under Approved Type
Certificates applied for after September 14, 1969.

17. Key Words T8, Distribution Statement
Shoulder Harnesses, Restraint Systems, | Availability is unlimited. Document may
Safety Harness, Survival, Aviation be released to the National Technical
Accidents Information Service, Springfield, Virginia

22151, for sale to the public.

19. Security Classif, (of this report) WH. Security Classif. (of this page) 21. No. of Pages | 22. Price

Unclassified Unclassified 5 $3.00

Form DOT F 1700.7 (2-69)



e

bad

»

REFERENCES

. Cierebiej, A., and Stedman, V. G.: A Tabulation of

Injuries to 522 Pilot Fatalities in 564 Fatal General
Aviation Aircraft Accidents for the Year 1966.
Compiled accident data, Office of Aviation Medicine,
Federal Aviation Administration, Department of
Transportation, Washington, D.C. Interal Office
Communication.

De Haven, H.: The Site, Frequency, and Dangerous-
ness of Injury Sustained by 800 Survivors of Light
Plane Accidents. Department of Public Health and
Preventative Medicine, Cornell University Medical
College, July 1952.

Marrow, D, J.: Analysis of Injuries of 1942 Persons
in 1422 Light Plane Accidents. Unpublished data,
CAA Medical Service Records, Washington, D.C.,
1949.

Swearingen, J. J.: General Aviation Structures Di-
rectly Responsible for Trauma in Crash Decelera-

tions. Federal Aviation Administration, Office of
Aviation Medicine Report No. FAA-AM-71-3,
January 1971.

Wallace, T. F., and Swearingen, J. J.: Crash Injury
Severity as Related to Aircraft Altitude During
Impact, SAE National Business and Utility Aircraft
Meeting, Wichita, Kansas, March 1971.

Swearingen, J. J.; Hasbrook, A. H.; Snyder, R. G.;
McFadden, E. B.: Kinematic Behavior of the
Human Body During Decelerations, Federal Aviation
Administration, Office of Aviation Medicine Report
No. AM 62-13, June 1962.

Young, J. W.: Functional Comparison of Basic Re-
straint Systems. Federal Aviation Administration,
Office of Aviation Medicine Report No. AM 67-13,
June 1967.

Stapp, J. P.: Design Criteria for Occupant Restraint
Systems. Proceedings of the Seminar on Design
Aspects of Occupant Survivability in Aircraft, Fed-
eral Aviation Administration, Flight Standards
Service, Oklahoma City, Oklahoma, February 11-15,
1963.

9. Turnbow, J. R.; Carroll, D. F.; Haly, J. L, Jr;
Reed, W. H.; Robertson, 8. H.; Weinberg, L. W. T.:
Crash Survival Design Guide, USTTVLABS Tech-
nical Report 67-22, U.S. Army Aviation Materiel
Laboratories, Fort Eustis, Virginia, July 1967.

10, Hasbrook, A. H.: Crash Load Vectors in Severe but
Survivable Light Plane Accidents. Presented at the
National Busines Aircraft Meeting, Wichita, Kansas,
March 1969, SAE Paper No. 690336.

11. Shaw, R. S.: Human Tolerance to Negative Accelera-
tions of Short Duration. Journal of Aviation
Medicine, 19(1) :39-44, February 1948.

12, Stapp, J. P.: Effects of Mechanical Force on Living
Tissues I—Abrupt Deceleration and Windblast.
Journal of Aviation Medicine, 26(4) ;268-288,
August 1955.

13, Beeding, Jr., E. L, and Mosely, J. D.: Human De-
celeration Tests, AFMDC-TN-60-2, USAF Missile
Development Center, Holloman Air Force Base, New
Mexico, January 1960.

14, Gregg, L. W. and Pearson, R. G.: Factorial Strue-
ture of Impact and Damage Variables in Light
Plane Accidents. Human Factors, 3 :227-244, 1961.

15. Hasbrook, A. H.: Crash-safe Design can Make Many
Accidents Survivable. Aerospace Engineering, 79-
80, 82, 87. September 1960.

16, Snyder, R. G.; Crosby, W. M.; Snow, C. C.; Young,
J. W.; and Hanson, M. $.: Seat Belt Injuries in
Impact Federal Aviation Administration, Office of
Aviation Medicine Report No. AM 69-5, March 1969.

17. Snyder, R. G.; Snow, C. C.; Young, J. W.; Crosby,
W. M.; and Price, G, T.: Pathology of Trauma
Attributed to Restraint Systems in Crash Impacts,
Federal Aviation Administration, Office of Aviation
Medicine Report No, AM 69-8, February 1969.

18, Swearingen, J. J.: Public Acceptance of Various
Upper Torso Restraints. Federal Aviation Admin-
stration, Office of Aviation Medicine Report No.
FAA-AM-T1-12, February 1971.

21962





THF BENEFITS OF THE USE OF SHOULDER HARNESS IN GENERAL
AVIATION AIRCRAFT

I. Introduction.

It is fully within the state of the art for a gen-
eral aviation aircraft manufacturer to produce
and market an aircraft that will protect its oc-
cupants from death or serious injury in the event
of a moderate to severe crash landing if known
bioengineering data are incorporated in the
design of the aircraft. Data compiled from in-
vestigations of survivable general aviation air-
craft accidents *?*** clearly indicate that serious
and fatal injuries occur most frequently to the
occupants as a result of the unprotected head
and neck or chest flailing in contact with the air-
craft controls, instrument panel, or exposed, un-
padded structure.

The most casual observer will notice, upon
examination of a typical light aircraft interior,
the rigid instrument panel studded with heavy
instruments, protruding knobs with sharp edges,
toggle switches with sharp points, exposed, un-
padded structure, and a seat belt assembly that
can only be described as meeting some minimum
requirements. Sitting on the ground or in
normal flight on a turbulence-free day, these
items are harmless. During the dynamic crash
anvironment, however, these objects become
vicious. They stab, tear, rip, and break the
‘issues, protoplasm, and bones of the unfortunate
vuman bodies that are forced in contact with
‘hem during the milliseconds of sheer terror that
secur when the forward motion of the aircraft
s abruptly retarded and deflected by impact with
zround objects during an emergency landing
ittempt.

Several approaches are possible to prevent the
nteraction of human protoplasm and potentially
langerous aircraft hardware and _ accessories.
Jne way of reaching this objective is by the

Mr. Sirkis is an engineer in the Aeromedical Applica-

ion Division, Office of Aviation Medicine, Federal
aviation Administration, Department of Transporta-
ion, Washington, D.C. 20590.

elimination of all rigid structures within the
passenger cabin that can produce puncture
wounds. This approach requires definition of
the flailing envelopes of the cabin occupants and
the removal or modification of all sharp,
elongated, brittle, pointed or otherwise dangerous
objects within these envelopes. Implementation
of this method is probably restricted to new air-
craft designs since the cost of incorporating this
in present designs would be substantial.

Another way to reduce injuries would be the
installation of energy absorbing structure or slow
return padding behind surfaces likely to be
struck by the head or chest during impact so that
deceleration distance is provided by the re-
arrangement of the structure or deflection of the
padding, rather than the painful rearrangement
of human tissue. This concept of energy absorp-
tion, which also includes automatically inflating
air bag restraint systems, seems again to be more
appropriate for incorporation in new designs
rather than in existing aircraft.

The installation and use of shoulder harnesses
is a practical and relatively inexpensive solution
to the problem of maintaining separation be-
tween man and machine during a crash sequence.
This solution is applicable to existing aircraft
as well as new designs. The addition of shoulder
harness to the tie down chain of the general avia-
tion aircraft occupant will increase the prob-
ability of his surviving a severe crash and
minimize injuries resulting from light to
moderate crashes.

Il. Research Findings.

Swearingen, et al® present a detailed descrip-
tion of the space which may be traversed by the
human head, trunk, and appendages during
flailing motions when exposed to crash impact
forces with lap belt restraint only being used.
‘These researchers reported that the flailing
envelope for a single individual restrained by a