of these factors would include system reliability,
blast effects (over-pressures on the eardrum),
and other injury potentials, as well as engineering
factors still to be resolved.

Vv. Summary

The limited nature of this study suggests only
tentative conclusions which must be confirmed
by more extensive biomedical investigation.
Nevertheless, these tests have demonstrated :

A. Air Bag Restraint System:

1, Paired baboon subjects survived impacts
from 33 to 57 peak g. (64 mph impact velocity)
at an onset rate of 5,900 g./sec. for 0.079 second
total duration, Although evidence of lung,
pancreatic, and adrenal hemorrhage was pro-
duced in one animal impacted at 47g., and a
significant bladder hemorrhage and rupture in
a second animal impacted three times at 46, 46,
and 50 peak g. (accumulative), a third 47g. im-
pact resulted in no evidence of clinical trauma
whatever. Gross injury at 55 and 57g. was not
felt to be significant.

2. While injury was thus demonstrated to oc-
cur with this type of restraint, it must be pointed
out that the magnitude of force tested was in
excess of that which produced fatal injury (about
40g.) in other systems tested, and the maximum
protective tolerance level was not reached for
either nonreversible injury or survival.

3. Post-impact observation of three animals
for 4 to 12 weeks (of the paired tests, with one
at each level being terminated immediately post-
impact) suggested that biochemical changes con-
sistent with stress and tissue trauma occurred
but were not conclusive nor of a statistically
significant nature due to insufficient sample.

4, Dural congestion, evident in four of six
animals autopsied immediately post-impact in
air-bag tests and in all four yoke restraint tests,
was not observed in the two animals autopsied
4 weeks nor one animal autopsied 3 months post-
impact. This suggests that this brain injury
typically observed immediately post-impact is
reversible.

18

5. Belt loadings (of lap restraint) were half
normal loads occurring with lap belt and in no
cases were belt contusions evident.

6. Rebound effect may occur and the air bag
system exhaust deflation capability should be
considered.

7. All subjects moved within 10 seconds of
impact and were alert and active within 20
seconds of impact. In comparison, no other sys-
tem tested to date resulted in such immediate
subject recovery post-impact. This may have
important implications where immediate evacua-
tion is important, provided that the deflated bag
does not become an obstacle.

8, Kinematic review of the high-speed movies
suggests that a concave shape to the expanded
air bag might provide additional directional
stability as the subject is decelerated.

9, Future tests should be conducted in a closed
environment and directed toward investigation
of physiological effects of acoustics and blast
upon the organism.

B. Inertia-Locking Reel Inverted-Y Yoke
Torso:

1. The yoke restraint system with inertia reel
offered relatively better restraint than the lap
belt alone, the single diagonal belt, or the 3-point
system.

2. In the forward-facing position tests were
survivable (with reversible injury) at 438g., but
appeared marginal for survival at 49g. Marked
contusions from the webbing were observed.

3. The documentation of myocardial frag-
mentation (transverse rupture of muscle fibers)
observed in the 49g. level exposure, suggests a
rather significant departure from other types of
cardiac damage (microhemorrhage) in terms of
severity.

4, In all four tests conducted with this system,
the inertia reel locked satisfactorily at impact.
However, in two of the four tests the reel base
was deformed by the force of the impact and
made the reel inoperable until repaired.

5. Distribution of impact loads were nearly
equal between the lap and shoulder belts, thus
suggesting that upper torso webbing strength
should be as strong as lap belt webbing.


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just this during the crash landing of a B-25 in
April, 1951. This experience contributed to the
proposed design of a personnel restraint system**
to the Air Force in 1957 by one of the authors
(RGS), while at the Applied Research Labora-
tory of the College of Engineering, University
of Arizona, but which was rejected in favor of
the Chance-Vought system.**

The most vigorous proponent of this type of
restraint, Clark, who discovered advantages of
employing air-stop restraint in 1960, has con-
tributed substantially to the potentialities of this
system.*?> As in much other research, however,
a considerable amount of study and development
by independent investigators and organizations
has been involved, particularly in the past few
years, but which has not been published. The
current test series is a continuation of a long-
range investigation of the relative impact injury
protection and effectiveness of major restraint
systems utilized in general aviation aircraft and
in limited automotive use. The objective of these
tests was to determine how much protection these
advanced restraint concepts provided and to ob-
tain preliminary biomechanical and physiological
data under controlled impact conditions. In ad-
dition, it was hoped in this preliminary series of
experiments to provide an initial basis for di-
rection of future test requirements.

II. Method and Materials

Thirteen impact tests were performed using
eleven adult female Savannah baboons* (Papio
cynocephalus),** ranging in body weight from
151% to 3414 pounds. Four of these tests were
conducted using the yoke harness and inertia-
locking reel (three forward, one 90° side-facing),
with four different test subjects, and nine air-bag
restraint tests utilizing seven different subjects
(all forward facing). Animals were obtained
from the breeding colony of the Southwest
Foundation for Research and Education at San
Antonio, Texas, and from International Animal
Imports, Ferndale, Michigan. All were shipped
by air from 2 to 6 days prior to tests at Hollo-
man AFB.

“The animals used for these experiments were lawfully
acquired and treated in accordance with the Principles of
Laboratory Animal Care issued by the Animal Facilities
Standards Committee of the Animal Care Panel, U.S. Depart-
ment of Health, Education, and Welfare, Public Health Service,
Mareh 1963.

**Previously designated by primatologists as Kenya baboons
(Papio doguera), and so identified in previous papers.

Tests were run between May 29 and June 3,
1967, utilizing the Daisy Decelerator"* of the
6571st Aeromedical Research Laboratory at Hol-
loman AFB, New Mexico (Fig. 2). The seat
was an F-111 test frame, modified for baboons,
and mounted on the ARL Omni-directional Sled.
The 4,500 pounds tensile strength nylon lap belt
used in each test and the upper torso yoke web-
bing used in the Y-yoke tests were replaced after
each test. The lap belt was installed at a 55°
angle to the seat pan. Prior to each run, static
belt. tension for each side of the lap belt was
stabilized at 1.5 kg. (8.8 lb.). Each subject was
thus provided with the same degree of initial
belt tightness (tension).

Test conditions involved 0°-0°-0° forward-
facing (—Gx) seat orientation in all air-bag
tests and in three of the four Y-yoke tests. In
one Y-yoke test, 0°-90°-0° body orientation
(—G,) was utilized for a 90° side impact. (Ad-
ditional side impacts at 90°- and 50°-body
orientation were run concurrently with subjects
restrained by 3-point harnesses for comparison,
but these are not included in the above totals.)
The seat back was 18° from the vertical plane
in all tests, and shoulder harness angle for the
yoke harness tests was measured at 45° (relative
to the horizontal) over the shoulder in each case.

For the double-torso inverted-Y yoke system,
protocol was established for one run at 30g.
(sled avg. g.) in both forward-facing and side-
facing positions, one run at 43g., and one run
at 49g. An initial value of 30g. was selected as
this was the level at which impact injury was
evident in other types of restraint systems using
baboon subjects in similar deceleration patterns.
Sled g. was measured since this could be ac-
curately determined and compared to previous
tests. Subject decelerations, as measured by
chest or head accelerometers, had proven to be
extremely unreliable in previous tests due to
orientation and, in particular, mounting problems.

Air-bag tests were designed as duplicate tests,
from 30g. to 50g. (sled avg. g.), with one animal
terminated immediately post-impact (3-6 min-
utes), and the second, animal for each series
allowed to survive for chronic post-impact moni-
toring. Two of the latter were monitored for
4 weeks post-impact before being terminated to
allow for any possible trauma as a result of
impact to become evident. One subject impacted



ry

a

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11,

12,

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14.

bb.

. Anon.: The First Aeronaut.

REFERENCES

ANGEL, C., Kervan, F., BLortscHer, H., and Gorp, H.:
Proposed Program to Develop Techniques for Simu-
lation of Physiological Sensations of Re-entry and
Landing of Boost-Guide Vehicles. Report TAP-8935,
Goodyear Aircraft Corporation, Akron, Ohio, De-
cember, 1959.

Harpers New Monthly
Magazine, 8(46) : 521, 1854.

. Aviation Safety Engineering and Research of Flight

Safety Foundation: Crash Injury Evaluation. Per-
sonal Restraint System Study CV-2 DeHavilland
Caribou. Rept. AVCIR 62-16, 1964.

Backstrom, C.: Traffic Injuries in South Sweden
with Special Reference to Medico-Legal Autopsies
of Car Occupants and Value of Seat Belts. Acta
Chirurgica Scandinavica, Suppl. 308, 1963.

. Bareckt, C. J.: Auto Crash Safety Research Leading

to Optimum Protection for Automobile Occupants.
American Seating Company, Grand Rapids, 1957.

. Bareckr, C. J.: File of Car Crash Tests at Hollo-

man AFB, American Seating Company, 1958.

. Benrup, D, W.: 1960-61 as cited by Clark, Ninth

Stapp Car Crash Conference, Proceedings.

. Bertrann, H, A.: 1955 U.S. Patent 2,834,606 granted

18 May 1958 and U.S. Patent 2,834,609.

Cattaman, J.: U.S. Makers Select 2-Buckle Setup
for Lap-Shoulder Belts. Automotive News pp. 10,
17-18, 1967.

Cantyre, L.: Literature Survey on Alrerew Re-
straint. Report ES 29260, Douglas Aircraft Com-
pany, Inc. El Segundo, California, February, 1959.
Cuanpuer, R. F.: The Daisy Decelerator, Hollo-
man AFB, New Mexico, 657ist Aeromedical Re-
search Laboratory, Tech, Report ARI-TR-67-8,
1967.

Crank, C., et al.: Technical Proposal for a Universal
Couch Restraint System Concept Development.
Engineering Report 12434P, Martin Company, Balti-
more, Md., May, 1962.

Crarg, 0., Brecrscrmyr, C., and Jorpon, F.: Impact
Protection with the “Airstop’ Restraint System.
Eighth Annual Stapp Car Crash Conference, Detroit
October, 1964. Wayne State University Press, De-
troit, 1966. (Engineering Report 18670, Martin
Company, Baltimore, Md., October, 1964.)

Crark, C, and Brecuscuamr, C.: The Analytical
Performance of an Airstop Restraint System in an
Automobile Crash. Engineering Report 14005, Mar-
tin Company, Baltimore, Md., October, 1965.

Crank, C.: 1965 Human ‘Transportation Fatalities
and Protection Against Rear and Side Crash Loads
by the Airstop Restraint. Proceedings, Ninth Stapp

19

16.

17.

18.

19.

21,

22,

24.

25,

28.

29.

Cur Orash Conference,
Press, 1966.

Crospy, W. M., Swyper, R. G., Hanson, P., and Snow,
C. C.: Impact Injuries to the Pregnant Female.
I: Bxperimental Studies. Presented, Regional Meet-
ing Central Association for Gynecologists and Ob-
stetricians, Detroit, 16 Sept. 1967; FAA Report AM
68-6,

Dantet, R. P.: Explosive Charge Activation of Air
Bag. Patent Disclosure, Ford Motor Company,
Dearborn, 25 Jan. 1960.

be ZA Pena, A. and Gorpziener, J. W.: Clinical
Parameters of the Normal Baboon. The Baboon in
Medical Research, Proceedings, Vol. II, pp. 879-889.
First International Symposium on the Baboon and
Its Use as an Experimental Animal. (H. Vagtborg,
Hd.) University of Texas Press, 1967.

Federal Aviation Agency. Calculations of Loads in

University of Minnesota

Crash Landing of Boeing 727 Airliner. Unpublished
data. Aeronautical Center, 1966.
. Federal Aviation Agency, Commercial Airliner

Crash Tests, Phoenix, Arizona, 1964.

Federal Aviation Agency. Technical Standard Order
C22e, 3. 1, “Material.”

Federal Register 15CFR Part 9, 31 August 1966.
Also see Society of Engineers 1965 Handbook, J4c
SAE J4C Report of Motor Vehicle Seat Belt Com-
mittee, revised July 1965. (Technical Report Pre-
print in 1966 Handbook.)

. Fuasore, W. J.: 1957 U.S. Patent 2,938,570 filed

5 July 1957 and granted 31 May 1960.
Ford Motor Company, ‘Testing Operations Office,
(TSO) Reports of Car Crash Tests. Unpublished.
1967.

FREEMAN, H. B., Boyce, W. ©., McKinney, R., and
Apams, C. R.: Personal Restraint System, Progress
Report No. 2, Contract AF33 (600) 41418, Chance-
Vought Corporation, Dallas, Texas, September, 1960.

. Garrett, J. W.: A Study of Seat Belts in Wisconsin

Automobile Accidents. Cornell Aeronautical Lab-
oratory, Inc, Rept. No. VJ-1823-R3, 1963.

. Hasproox, A. H.: Crash Survival Study: National

Airlines DC-6 Accident at Elizabeth, N.J., on Feb-
ruary 11, 1952, Cornell University Medical College,
Crash Injury Research, New York, N.Y, 1953.

Hass, G.: An Analysis of Relations Between Force,
Aircraft Structure and Injuries to Personnel In-
volved in Aircraft Accidents with Recommendations
for Safer Principles in Design of Certain Types of
Aircraft. School of Aviation Medicine, Prof. 187,
Rept. N. 1, Randolph AFB, Texas, 1943.

Herrick, J, W.: 1952 U.S. Patent 2,649,311 filed
in August 1952, and granted 18 August 1953.



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Table II - Yoke Restraint Tests, Medical Data Summary: Pathology

G NUMBER GROSS MICROSCOPIC
30 3591 Dural Congestion Cardiac Hemorrhage
Lung Congestion and Edema
32 3589 Cranial Fracture Cardiac Hemorrhage
Dural Hemorrhage Cerebrum Hemorrhage
Abdominal Contusions Lung Edema and Hemorrhage
43 3593 Dural Congestion Lung Edema
Bilateral Contusions of Anterior Cardiac Hemorrhages
Axillary Folds and Adjacent Uterine Congestion
Deltoid Areas
Abdominal Contusions
Scapular Fracture
49 3605 Dural Congestion Adrenal Congestion and Hemorrhage
Pericardial Hemorrhage Myocardial Fragmentation
Broad Ligament Hemorrhage Pyknosis and Karyolysis of Nuclei of
Mesentery Hemorrhage Myocardial Fibers
Abdominal Wall Hemorrhage
Bilateral Avulsion of the Pectoralis
Major Muscles
Incomplete Bilateral Avulsion of the
Pectoralis Minor Muscles
Bilateral Contusions of Shoulder-Neck
Area
Incomplete Displacement of Humerus

Note body kinematics in a 30g. impact as shown
in Figure 4. Insufficient tests were made with
this restraint system to provide statistically sig-
nificant data. Yet, based upon relative compari-
sons with over 60 tests previously made with the
baboon subject, in identical deceleration patterns,
with various restraint systems, some valid gen-
eral inferences may be made (Fig. 5). The yoke-
restraint system tested has been demonstrated to
offer relatively better protection for the subject
than the lap belt alone, the European single
diagonal belt, or the current 3-point system.
This confirms previous studies conducted with
anthropomorphic dummies. It also appears to
be a more feasible restraint system than the seat-
attached double-torso harness either with or
without inertia reel retraction: in the first case
because of the structural seat changes necessary
due to the higher center of gravity loading, and
in the latter case because of the loss of unre-
stricted motion for the fixed restraint occupant.
In addition, the ease of placing and adjusting
the overhead restraint system on the occupant,
as well as comfort considerations (the torso belts

go over the shoulders but slope to the sides by
the lap belt, thus avoiding pressures or impinge-
ment over the breast area) and minimal distor-
tion of clothing, have been demonstrated by
previous human subjective tests, but were items
not within the scope of these tests.

B. Air Bag Tests: The physical data for the
nine air-bag tests conducted with seven baboon
subjects are presented in Table III. All tests
were in the forward-facing body orientation, with
seat pan 13° relative to the horizontal. Entrance
velocities varied from 71 to 94.2 ft./sec. (or 48
to 64 mph), and onset. rates from 3,300 g./sec. to
6,000 g./sec. Total deceleration time durations
of 0.059 second to 0.091 second were recorded.
These patterns were as close to the actual auto-
motive crash profiles as was possible to achieve
with this particular weight (4,500 lbs.) sled used
on the Daisy Decelerator.

As with the yoke series, initial tests were at
30g. (average). Each level of force magnitude
above this pattern was probed for subjective non-
reversible. tolerance effects prior to proceeding
to a higher level. In this regard, one Ippolito


Figure 8. Yoke-type restraint with subject in place

prior to run, Shoulder belt angle is 45° to inertia
reel. Note position of right shoulder belt strain
gauge.

It may thus provide some rearward motion pro-
tection (we did not test to what degree it could
offer hyper-extension protection in rear impact).
The yoke was attached overhead at a 45° shoulder
angle (relative to the vertical plane) to the in-
ertia reel, which was set at 0.8g. activation. A
new reel was used in the first three tests, one
reel being used twice.

Each subject was anesthetized with 1 mg./kg.
body weight of Sernylan® prior to each run.
The subject was removed from the cage after
the drug had taken effect and prepared for the
tests in an adjacent surgical room. Hands and
feet were covered with tape to provide improved
photometric kinematic targets. The animals
were muzzled to prevent injury to the tongue
during impact and for photometric usage. The
animal was next taken to the test sled, positioned,
and the seat-belt tension adjusted. Low-strength
masking tape was used to keep the legs and
thorax in proper position for the run; however,

this easily tore at impact and did not provide
additional restraint protection. In the air-bag
tests a loop of rope under the arms and attached
over the seat back supported the animal in an
upright position until mechanically released by
cable 0.6 sec. prior to impact. Muscle tonus was
carefully monitored to assure that all runs were
made at the same clinical level.

The strain gauges were fabricated for the
6571st Aeromedical Research Laboratory by
Land-Air Division of Dynalectron at Holloman
AFB. They were originally designed for the
standard 2-inch wide belt, but were modified to
the 1-inch webbing used in these tests. Gauges
were placed at each end of the belt, two for lap
belts and two additional gauges for the lower
ends of the torso yoke. Each strain gauge buckle
was instrumented with four strain gauges in
order to measure the bending moment due to the
force imposed upon the belt. When the belt was
stretched, the metal of the buckle was stressed
and deflected. Although each buckle contained
eight elements, it electrically appeared as a four-
active-arm bridge. Resistance of the electrical
elements changed as a result of changes of strain
on the metal, Calibrations were made by placing
a known force on the belt and measuring the
electrical output of the bridge.

Photographie coverage included use of a
Waddel 161A 2,000 fps camera for frontal view,
and two Ippolito Fastex 2,000 fps cameras for
lateral views, film from one of the laterals being
processed immediately and wet-viewed to examine
results of each test quickly prior to the succeed-
ing test. One each 16 mm, documentary color
film, 35 mm. still color film, and 4x5 still pho-
tography were also obtained. In addition, three
black and white Polaroid photos were obtained
for each run; pre-impact, during impact, and
post-impact. These served as useful working
references to note specific position, cross-check
run numbers and animals, and other details of
note.

Gross autopsy was conducted at the 657ist
Aeromedical Research Laboratories immediately
post-impact for the terminated subjects, and at
the facilities of Space/Defense Corporation,
Birmingham, Michigan, for the three terminated
4- and 12-weeks post-impact. Whole body post-
impact X-rays were taken prior to autopsy and
radiography was conducted at the FAA Civil
Aeromedical Institute, Oklahoma City, as was



Fieure 2, View of the Daisy Decelerator from the midpoint of the 120’ track. The omnidirectional sled used in

these tests is shown at the far end of the building housing an air gun accelerator.
eras are positioned on the tower located over the water brake.

animal quarters are to the left of this view.

at 38g. (avg. g.) was monitored for 12 weeks
post-impact. Time duration was to remain a
constant, but actually varied slightly from 0.045
to 0.060 sec, (plateau duration) and 0.073 to
0.094 sec. total duration for the yoke harness,
and from 0.040 to 0.060 sec. (plateau duration)
and 0.059 to 0.091 sec. total duration for the air-
bag tests. Entrance velocities varied from 73.6
ft./sec. (50 mph) to 94.4 ft./sec. (64 mph) for
the yoke tests, and from 71 ft./sec. (48 mph) to
94.2 ft./sec. (64 mph) for the air-bag tests. Rates
of onset ranged from 2,700 g./sec. to 6,100 g./sec.
for the yoke restraint, and from 3,300 g./sec. to
5,900 g./sec. for the air-bag tests. Table I pro-
vides a summary of these yoke data together with
belt loadings measured. (See Table 1 on page 7.)

The air-bag restraint system was scaled down
to be the same relative (14) size for the baboon
subject as the full-size version for humans,
previously tested in automobiles with anthropo-
morphic dummies. Each bag was folded into a
test instrument panel placed 1014 inches from

High-speed overhead cam-
Instrumentation and fire control buildings and

the subject’s chest: The top of the panel was
level with the subject’s nipple height (which is
proportionately lower in the human), and was
moved 2 inches lower in all subsequent tests. A
standard 1-inch lap belt was positioned on each
animal. Actuation of the system was initiated
by an electronic impulse as the sled probe pene-
trated the brake system and the bag was fully
deployed in 0.020 second. Energy dissipation
was accomplished ‘by deflating the bag as the
occupant moved into it.

The yoke-restraint system (Fig. 3) consisted
of a single lap belt (scaled for baboon) of 1-inch,
4,500 pounds tensile strength nylon webbing, ad-
justed statically pre-run to 1.5 kg. (3.3 Ibs.)
tension. Strain gauges were mounted on both
sides to record belt. forces. The torso portion of
the harness was attached separately at each side
adjacent to the lap belt tie-downs and was equip-
ped with strain gauges. The yoke of the harness
came together behind the head at the occipital
protuberance, but did not touch the head or neck.


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17



Table I - Yoke Restraint Tests, Physical Data Summary

SLED PEAK BELT FORCE (LBS)
Test| Daisy |Baboon| Wet. |Body Orientation | Seat Back Time Duration
‘Test No| No, | (LBS) |Relative to Force| Orientation Entrance Vel. | Onset Rate|___(gecs) RT | eft | RT | Left
Direction (1) | (Angle) (2) | PeakG | Ave G| (ft/sec) (g/sec) [Plateau |Total | Lap Belt} Lap Belt Diagonal |Diagonal | Yoke
90 Left. °
1 | 3589 | 3346 | 30 0-90-0 13 sz { 3 15,2 4300 0.060} 0.093] 960 | 360 | 450 | 950
Forward °
2 | sso | 636 | 33.5) 0-00 13° go | 29 13.6 2700 0.054} 0,094 440 | 440 | 420 360 | ---
Forward °
3 | a593 | 2605 0-0-0 1s 43 | 43 88.0 5400 0.049] 0.083] --- | --- | --- ae
4 | 3605 | 2706 | 28 o-0-0 we 49 | a7 94.4 100 0,045] 0,073] 780 | 650 | 490 a0 | ---

()) Forward Facing (-G,)
(2) Relative to vertical

during impact into the plywood side panel, a
fatal artifact was introduced. Radiographic
studies revealed a comminuted fracture involving
the cranial vault, with multiple fracture lines
throughout the frontal-parietal area probably
extending to both sides of the midline. Some of
the fragments were separated by some 38 mm.
No gross trauma to the neck was observed, al-
though sub-clinical complaints could not be
evaluated. In previous similar side impact tests
at this level with both the European diagonal
belt and the’ 3-point belt, fractured necks re-
sulted from the impact. One might speculate
that the less rigid yoke system may decrease the
possibility of this type injury in side impact,
assuming package space is available to minimize
artifact.

The forward-facing yoke impacts were ini-
tiated at the 30g. level (where previous tests
with other systems had shown injury becoming
evident) and progressed to 49 peak g., far higher
than was survivable for the unrestrained torso
systems. In one forward impact at 43 peak g.
(88 ft./sec.) a transverse fracture of the neck of
the scapula, proximal to the glenoid process,
occurred, with slight displacement. As shown
in Table II, injuries were severe at 49g.

As expected, there was a general trend of in-
creasing number and severity of trauma with
increasing g. levels in this particular series. The
type and degree of trauma experienced by the
49g. subject is rather severe, both in systemic
function and integrity of supporting structures.
In this particular case, it appears that the exten-
sive structural trauma of the pectoralis muscles,
superficial contusions over the shoulder, and ab-
dominal areas and the partial dislocation of the

humerus, were the direct result of restraint belt
pressures produced at this relatively high g. level.
As evidenced by this series of tests, the yoke-type
restraint may cause distinctive injury patterns.

The occurrence of cardiac hemorrhage is of
interest since it occurs in all test subjects, in-
creasing in severity, like other injuries, with
increasing g. levels.

Lung edema and hemorrhage were observed
in all but one subject. Single cases of uterine
congestion and adrenal hemorrhage occurred.

Belt forces were measured according to the
technique previously described. These are listed
in Table I. In Daisy runs Number 3589 (32g.
side impact) and Number 3591 (80g. forward
impact) strain gauges were attached to the lower
portion of both lap belts and both torso belts.
In addition, for these tests, a strain gauge was
attached to the Y-yoke above the torso belt junc-
tion; however, due to the sensitivity of the in-
ertia reel, the slight additional weight created
belt slack and allowed the animal to slump for-
ward. In the subsequent tests a yoke tension
measurement was not attempted for this reason.
Note that in the left-side impact the force on
the right lap belt was nearly three times (960
Ibs.) that on the left lap belt (360 lbs.). This
corresponds with the ratios of the left-to-right
belt forces previously found in side-impact tests.
Note that in run Number 3591 (30g.) the lap-
belt and torso-belt forces were fairly close, al-
though in run Number 3065 (49g.) there was a
wider discrepancy. Subsequent dummy tests by
investigators at various laboratories, including
Ford, General Motors, and the National Bureau
of Standards, have also indicated that belt loads
are often close for both lap and torso harnesses.



AM 69-4

EXPERIMENTAL IMPACT PROTECTION WITH
ADVANCED RESTRAINT SYSTEMS:

Preliminary Primate Tests with Air Bag and Inertia Reel /Inverted-Y Yoke
Torso Harness

Richard G. Snyder, Ph.D.
Joseph W. Young, A.M.
Clyde C. Snow, Ph.D.

Approved by Released by
Mihi, (USege€ uo

J. Rozerr Diniz, M.D. P. V. Smcen, M.D.
Cuter, Civ, ArROMEDICAL Feperat Arr Sureron
Instrrore

February 1969

Department of Transportation

FEDERAL AVIATION ADMINISTRATION
Office of Aviation Medicine



© milliseconds
0. milliseconds
0 milliseconds

Ficure 4, A comparison of the body kinematics with
(A) lap belt only, (B) yoke harness, and (C) air-
bag restraint system at 30g. impact; at 0, 20, and
40 milliseconds of body deceleration time.

high-speed motion picture film was wet-read
immediately post-impact, and a physical exami-
nation was made of the subject. Paired tests
were made at 30g., 42g., and 50g. average sled
loads, with one subject immediately terminated
post-impact, and the other allowed to survive.
In the latter case two were observed for 4 weeks
prior to autopsy, and the third for 12 weeks.

Necropsy protocols were completed in each case
utilizing techniques of both gross anatomical
examinations by dissections and microscopic
analyses of histological samples. Table IV sum-
marizes the medical findings.

In general, it is extremely difficult to assess the
significance of observed pathology to evaluate
restraint functions. In previous studies a num-
ber of specific traumas have been observed to
occur and have no correlation with basic environ-
mental factors or changing environmental con-
ditions. There appears, however, to be a gen-

10

eralized trend of characteristic pathology that
corresponds to certain experimental conditions
of impact. This phenomenon has been demon-
strated, in part, during the course of this and
related studies using the baboon subject.

Dural congestion and/or hemorrhage was ob-
served in all yoke tests from 30 to 49 peak g.
exposures (Table II). Similarly, this condition
was observed in all air-bag restraint test subjects
that were terminated immediately post-impact
for autopsy procedures. Exposure levels for
these particular tests were 33 to 55 peak g. loads
and extended to 57g.’s for the entire air-bag
series. Two subjects from the air-bag series,
having no apparent clinical difficulties, were
placed under observation for a 4 week post-
impact period then terminated to complete nec-
ropsy protocols. It is interesting to note that
one subject demonstrated only questionable evi-
dence of dural trauma, while no evidence of
congestion or hemorrhage appeared in the other
even though these subjects had been exposed to
the higher 47 and 57g. loadings, respectively.
A third subject, impacted at 33g., and not ob-
served to have any injury, was monitored for
3 months prior to termination. Upon autopsy
no trauma (or dural congestion) was found.
Since we have observed a high frequency of
dural congestion and hemorrhage in previous
baboon impacts of 16g. to 55g. peak levels, we
may tentatively suggest that this condition is
typical but transient in nature. If our conclu-
sion is valid, this condition would not be a useful
criterion in restraint system evaluation.

The summary of medical data for the air-bag
restraint subjects (Table IV) relates the degree
of increasing trauma severity to increasing g.
levels. Dural congestion, as expected, was present
in all subjects terminated immediately post-
impact and the regional congestion of the lungs
and liver in one subject, which may or may not
be typical, was still apparent 4 weeks post-
impact. Identical lung and spleen pathology
was demonstrated in both subjects terminated
4 weeks post-impact : atelectasis with emphysema
and edema in the lungs and occurrence of pig-
ment-laden macrophages in the spleen. In addi-
tion, glomerulitis was apparent in the 47g.
subject. The bladder of a 46g. exposure subject.
was ruptured and another exposed to 47g. ex-
perienced hemorrhage in certain lung areas,
pancreatic, and adrenal tissues.


Table III - Airbag Restraint Tests, Physical Data Summary

SLED PEAK BELT LOADS (86) |
Wet. | Body Orientation | Seat Back PFime Duration]
(LBS) | Relative to Force | Orientation Entrance Vel. | Onset Rate | (secs RT LEFT
Direction (1) (Angle) (2) | Peak |AveG] (ft/sec) (g/oce) [Plateau] Total] Lap Belt | Lap Belt
Forward
1 | 9895 | 2675 | 33.5 | 0-0-0 13° 33 30 no 3300 | 0.060 [0,001 450 450
2 | ss97 [2075 | s4.0 | 0-0-0 13° 36 | 33 14.0 3700 | 0.056 |o.086) alo soot
a | 3598 |-@) | 15.5 | 0-0-0 1s a | oar 85.6 4900 | 0.047 Jo.o76] 10 375
4 | 3599 [-@) | 15.5 | 0-0-0 13° 46 | 37 85.1 4600 | 0,052 [0,081] 300 240
s | 3600 |-@) | 15.5 | 0-00 13° so | 39 86.0 5600 | 0.048 0.074] 330 300
6 | x60 |--- | 20.5 | 0-0-0 13° at | oar 85.4, 300 | 0.047 Jo.075| 360 20
7 | 3602 |--- | 25.0 | 0-0-0 13° ale 85.7 4900 | 0.046 |9.075] 600 005
8 | 3603 |---| 22.0 | o-0-0 13° 55 | 50 94.0 6000 | 0.040 |0.059] 640 600
9 | 3604 |--- | 26.5 | 0-0-0 13° st | 50 94.2 s900 | 0.051 Jo.o79] 540 sio(®)

() Forward Facing (-G,)

(2) Relative to vertical

(8) Same animal . .
(4) Allowed to survive 12 weeks post-impact prior to autopsy
(8) Allowed to survive four weeks post impact prior to autopsy

Table IV - Airbag Restraint Tests, Medical Data Summary: Pathology

G | NUMBER GROSS WCROSCOPIC
B 3595 DURAL CONGESTION
4 | 3598" OURAL CONGESTION BLADDER HEMORRHAGE
BLADDER RUPTURE
47 3601 DURAL CONGESTION LUNG HEMORRHAGE AND EDEMA
PANCREAS HEMORRHAGE
ADRENAL HEMORRHAGE
4) 3602 LUNG ATELECTASIS WITH EMPHYSEMA
FRAGMENTATION OF VENTRICLE
GLOMERULITIS
PIGMENT LADEN MACROPHAGES IN SPLEEN
55 | 3603 DURAL CONGESTION
BROAD LIGAMENT HEMORRHAGE
7 3604 LUNG CONGESTION PULMONARY EDEMA
LIVER CONGESTION LUNG ATELECTASIS WITH EMPHYSEMA.
PIGMENT LADEN MACROPHAGES IN LUNG & SPLEEN

* SUBJECT WAS IMPACTED THREE CONSECUTIVE TIMES AT THIS G LEVEL. PATHOLOGY IS ACCUMULATIVE.

9



pathological histology. Gross and microscopic
tissue study of the brain was complemented by
electron-microscopic examination for fibrinolytic
activity.

All animals were examined for external evi-
dence of trauma post-impact, and one of each
pair at each impact level was sacrificed post-run
with 650 mg. Nembutal. The surviving ani-
mals were held for observation for 1 week and
then shipped to Gasow Veterinary Hospital,
Birmingham, Michigan, where they were further
observed for post-impact effects and for weekly
blood analysis by Space/Defense Corporation.

Ii. Discussion

Although these tests have been conducted con-
currently the data have been treated individually
and will be discussed as separate systems in this
section.

A. Inertia-Locking Reel with Inverted-Y
Yoke Torso Harness: The lap belt combined
with a yoke harness has been demonstrated to be
the most effective belt restraint system devised
of those evaluated. It has been compared to the
lap belt alone (which offers no torso protection
against jack-knifing), to the single diagonal belt
(as used in many European vehicles and which
provides absolutely no pelvic restraint, allowing
the lower portion of the body to swing free and
rotate about the belt), and the 3-point harness
(which offers limited protection). However
when the torso harness is tightened, an operator
may not be able to reach controls on the instru-
ment panel, is not free to move the upper portion
of his body, or may be uncomfortable or become
fatigued, any of which might contribute to acci-
dent causation. Thus to assure a practical and
effective system, provision must be made for
relatively unrestricted upper torso motion during
normal driving activities; however, instant and
automatic “locking” of the torso restraint is de-
sired during emergency braking (“panic stops”)
and required at impact. An inertia-reel mech-
anism can fulfill this requirement. Reels have
been used successfully in aircraft for many years,
but there are two major and significant differ-
ences between aircraft and automotive use which
are not generally recognized: (1.) Since the air-
craft ‘is not normally subjected to the rapid
braking decelerations like the automobile, the
loadings at which activation occurs is greater.
Usually this is at about 2g. in the aircraft reel,

while in the automobile, reel activation must
occur at much more sensitive settings, varying
from 0.3 to 0.5g. (DOT Standard for inertia-
reel activation states that this must not be over
0.5g., thus most reel manufacturers design for
0.3g. quality control to insure compliance) ; (2.)
The state-of-the-art in achieving quality control
for mass production of such devices has appar-
ently not reached an accepted level of reliability.
The 8.5 million cars (current annual production)
for example, would require 30 to 40 million
reels (including replacement stocks), compared
to present aircraft needs of a few thousand,
almost all of which are for military type air-
craft. To date, no manufacturer has had ex-
perience in quality control for such mass pro-
duction. The upper restraint inertia-reel for
general aviation aircraft is still being evaluated
by the Federal Aviation Administration Flight
Standards Service. The aircraft type installa-
tion with the shoulder straps extending over the
top and down behind the seat imposes loads at
the top of the seat back, and would restrict ad-
justment and require major structural changes
in present automobile seats, tie-down, and en-
vironmental structure. This can be avoided in
automobiles by utilizing a roof attachment, but
also requires adequate roof support to take the
additional loadings.

To our knowledge, the only automobiles cur-
rently utilizing a yoke-type double-shoulder torso
restraint with inertia reel are the specially modi-
fied Shelby Mustang GT 350 and GT 500 cars.
These restraints, which were originally devel-
oped by Ford, have not had previous biome-
chanical evaluation. To date there have been no
reports of accidents involving this type of har-
ness system in automobiles, thus our knowledge
is restricted to the anthropomorphic dummy
tests previously conducted, and the current ani-
mal study.

The tests conducted with the yoke restraint
consisted of three tests in the forward-facing
(—Gx) 0°-0°-0° body orientation at 30, 43, and
49 peak g., and one side-facing (lateral 90°) test
(—G,) 0°-90°-0° at 32 peak g. (Table I). Re-
spective entrance velocities ranged from 73.6
ft./sec. (50 mph) to 94.4 ft./sec. (64.5 mph),
onset rates from 2,700 to 6,100 g./sec., and titne
plateaus from 0.045 to 0.060 second.

The 90° lateral impact was at a severe level,
but due to the rebound of the subject’s head


30.

“31.

82.

33.

34,

35.

87.
38.

41

Jorpanorr, A.: Air Bag Restraint Design cited by
Clark, Stapp Car Crash Conference, 1952.
Kemmerer, R. M.: Air Bag—Passenger Restraint
System. Automotive Research Office, Impact Dy-
namics Department, Ford Motor Company, Rept.
No. S-67-3, 1967.

Konn, W. A.: Proposed Air Cushion Applications,
Disclosure, Ford Motor Company, Dearborn, 29
January 1957.

Lirz, J. 8., McCoy, L. E., Brran, M., and Prncz,
B. W.: Comparative Response of Live-Anesthetized
and Dead Embalmed Organisms Exposed to Impact
Stressing, Phase II: The Rhesus Monkey. Final
Report to Ford Motor Company. TR 67-107. Space/
Defense Corporation, Birmingham, Michigan, 1967.
Lister, R. D. and Miusom, B. M.: Car Seat Belts:
An Analysis of the Injuries Sustained by Car Occu-
pants. Practitioner 191: 332-340, 1963.

Lovetace, W. R., et al.: The Ejection Seat for
Emergency Escape from High-Speed Aircraft
(USAAF, ATSC, Wright Field) MR-TSEAL-3-696—
TAC, pp. 3, 1945,

MacVzan, S. S.: Seat Belt Usage and Vehicle Oc-
cupancy Data. Ford Motor Company Technical
Memo. PRM 66-26, 9 August 1966.

Manson, F. G.: U.S. Patent 2,057,687, 1985.

Nanum, A. M., Smet, A. W., and TracHTenseEra,
S. B.: Causes of Significant Injuries in Non-Fatal
Accidents. Proceedings, 10th Stapp Car Crash Con-
ference (Reprint SAE 660803), 1966.

Prnxet, J. I. and Rosenzerc, H. G.: Seat Design for
Crash Worthiness. NACA, Rept. 1332, 1957.

Snow, C. C., Snyper, R. G., Price, G. T., Sues,
T. K, and Parry, W. L. ‘rauma to the Urinary
System Caused by Abrupt Deceleration. Presented,
American Medical Association, Scientific Assembly
on Urology, Atlantic City, N.J., May 1967.

-Swyper, R. G., Crospy, W. M., Hanson, P., Snow,

©. C, Finee, J., and Omanprer, R.: Impact Injury
to the Pregnant Female and Fetus in Lap Belt Re-
straint. Presented, 10th Stapp Car Crash Confer-
ence, Holloman AFB, New Mexico; University of
Minnesota Press—SAH Paper No. 660801, 1967; FAA
AM 68-24,

42, Swyper, R. G., Crossy, W. M., Snow, ©. ©., Youne,
J. W., and Hanson, P.: Seat Belt Injuries in Impact.
Presented, University of Michigan Medical School,
Sesquicentennial Symposium on THE PREVENTION
OF HIGHWAY INJURY, Highway Safety Institute,
Ann Arbor, Michigan, 21 April 1967.

43. Snyper, R. G.: Design and Fabrication of a Re-
straint System for Advanced Manned Flight. Pro-
posal submitted to AMC Aeronautical Systems
Center, Wright Air Development Center (PR 96126).
Rept. 60-9-8, Applied Research Laboratory, College
of Engineering, University of Arizona, Tucson. 1960.

44, Syyper, R. G., SNow, ©. ©., Youne, J. W., Paice,
G. T. and Hanson, P.: Experimental Comparison
of Trauma in Lateral (—G,), Rearward Facing
(+G,) and Forward Facing (—G,) Body Orienta-
tions When Restrained by Lap Belt Only. Aerospace
Med. pp. 889-894, Sept. 1967. Presented, 38th Annual
Scientific Meeting, Aerospace Medical Association,
Washington, D.C., 10 April, as “Injury in Lateral
Impact (~G,) When Restrained by Aircraft Seat
Belt Only.” 1967.

45. Stoupt, H. W., Damon, A., McFartanp, R., and
Roserts, J.: Weight Height and Selected Body Di-
mensions of Adults, United States, 1960-1962. Wa-
tional Center for Health Statistics, Series 11, No. 8,
Washington, D.C. 1965.

46. United States Air Force. Handbook of Instructions
for Aircraft Design. AF SCM80-1 2.6 Acceleration
Loads. 2.6.1 Safety Belts and Harnesses. €.6-28A.

47, USAF MIL-W-4088. E Revision. Type 24 for
Safety -Seat Belts. (Replaces USAF Tech Order
18A 1-1-2, and Navy MIL-W-8630.)

48. U.S. National Advisory Committee for Aeronautics.
Accelerations in Fighter Airplane Crashes, Lewis
Flight Propulsion Laboratory, Cleveland. NACA
RM E57G@11, 1957.

49. Vrxuxat, H. D., Riowarp, G. P., and Srinnert, G.
W.: An Inter-Changeable Mobile Pilot Restraint Sys-
tem Designed for Use in High Sustained Acceleration
Force Fields. Aerospace Med. 33: 279-285, 1962.

50. Witson, ©. L.: (Ed.) Project Mercury Candidate
Evaluation Program, WADC Tech. Rept. 59-505,
p. 24, December 1959.


if inertia reels were used, some 35 million would
have been required’ — compared to the few thou-
sand produced currently for the aviation in-
dustry.

A related series of experiments on restraint
protection and impact injuries, using baboon
subjects on the Holloman AFB Daisy Decelerator
was conducted. The first of these, on the effect
of lap-belt restraint on the pregnant maternal
and fetal organism, was reported at the last
Stapp Conference,** and the final results in sub-
sequent medical meetings.**? Another study,
which compared the effectiveness of four basic
restraint systems used in automotive vehicles and
brought together related past studies, was re-
ported in April, 1967.*7 The present investiga-
tion was designed to provide a preliminary
evaluation of two advanced restraint concepts
which are being developed for possible future
automotive use, but which lacked biomechanical
evaluation.

Among new types of restraint systems being
considered for automotive vehicle occupant pro-
tection are the yoke harness with inertia-locking
reel and the air-bag restraint system. Inde-
pendently, each has had extensive development
by several engineering and research organiza-
tions. Originally, both systems were intended
for aircraft use, but neither has been utilized in
other than experimental tests.

The yoke harness with inertia reel (Fig. 1) is
a distinct variation of an aircraft torso harness
and reel system in that the torso harness is inde-
pendent of the seat back. In the new system
reported here, the reel is attached overhead,
rather than to the seat, thereby avoiding any
downward force on the shoulders (which may
contribute to the submarining action) and direct
loading to the top of the seat back (high cg.).
This system also differs in that the left and right
shoulder belts come together as a yoke (“in-
verted-Y”) behind the head, continuing upwards
to the reel as a single belt. In 1957, work by
Barecki of American Seating Company was an
early design of this type of system.’ In 1958,
several tests of this device were. conducted by
Col. Stapp at Holloman AFB, using cars which
were towed and snubbed to a stop.‘ In three
tests, human volunteers with heads positioned
forward (pre-flexion) were exposed to 18 (av-
erage) g. on the chest (26 peak g.).

Figure 1,

Inverted-Y yoke harness with inertia-locking
reel. The shoulder belts are attached to the floor
at the lower end, and the upper torso is free to
move until reel automatically locks at pre-set value
during braking or impact.

Air-bag restraint systems have been proposed
since at least 1935 when Manson filed a patent.
for a pneumatic airplane seat.*’ However, it
was not until 1952 that interest was again re-
gained and sporadic proposing, developing, and
testing was subsequently initiated by various in-
vestigators.°°* Despite this development work,
including tests with both anthropomorphic dum-
mies and human volunteers previously conducted
by various investigators for both systems, neither
air bags nor yoke restraints have had adequate
experimental biomedical evaluation under care-
fully controlled test conditions.

Although its actual origins may have been a
decade earlier in the occasional instance of some
aircrew member prematurely inflating his Mae-
West or life raft prior to a crash landing, several
members of the author’s (RGS) 7-man crew did


at the second week post-impact it would appear
that in this case the rise was due to bone tissue
damage and repair rather than to extensive blood
loss and consequent ionic shift. No consistent
pattern in acid photophatase is evident, though
a general elevation can be discerned. This ele-
vation might be the effect of the release of this
substance from RBC’s (where it is known to be
in high concentration) as a result of hemolytic
trauma. Alkaline phosphatase, an indication of
hard tissue change, is usually elevated in bone
diseases and injury. One possible reason for the
elevation noted is the extrusion of the enzyme
from the injured bone tissue. Another possibil-
ity is the over-production of the alkaline phos-
phatase enzyme in compensatory repair. Elevated
levels are seen in all animals in this series, per-
haps indicating that injury and repair to bony
tissue occurred. Bilirubin elevated levels in
trauma are evidence of either (or all) of the
following: RBC breakdown usually as a function
of hemorrhage; hepatic injury; destruction of
muscle tissue. The pattern observed in these
cases is not clear, since usually bilirubin is nor-
mally low pre-impact, and elevated post-impact.
This was observed only in animal Number 3597.

Lee-White coagulation times for the chronic
tests were high in each animal post-impact. By
3 weeks, post-impact coagulation times had de-
creased to normal range. Apparently the co-
agulation mechanisms were altered by the impact
stress, but what the modification was is not now
known. -As an indication of the inflammatory
stress reaction, one would expect white blood
cells to rise sharply post-impact. However, no
trend was discernible in the WBC data obtained
here. Changes in total plasma protein as a con-
sequence of trauma is due to release of fibrinogen,
RBC destruction, and soft tissue disruption.
Elevation of these values was observed in Number
3597 and Number 3604, suggesting such trau-
matic sequelae in these subjects. An unexplain-
able decrease was found in animal Number 3602.

These values have been compared to mean
hematology and blood chemistry values for 201
baboons studied by de la Peffa and Goldzieher,'*
but due to a number of differences in obtaining
blood samples between our series and theirs, no
conclusions may be drawn at this time.

Body kinematics during impact are of special
interest in restraint system evaluation. As shown
in Figure 4, in contrast to other restraint systems

13

tested, the upper thorax and head are pushed
back by the opening air bag while the lower
torso moves slightly forward. Figure 6 shows
one animal in position prior to the run. Note
that the restraint over the back of the seat was
released 0.6 second prior to impact by mechan-
ical means, and the masking tape used to hold
the animal in position also breaks at impact.
Figure 7 shows inflation of the air bag at the
moment of impact. Figures 8 and 9 show the
subject position immediately post-impact and
regaining an upright position by 20 seconds post-
impact. One important feature observed in the
use of this system in contrast to all other re-
straint systems previously tested, was that sub-
jects appeared to make almost immediate recovery
from impacts even up to 57g. Motion of the
arms was observed within 10 seconds, and within
20 seconds body response occurred, with the ani-
mal rapidly appearing alert. In contrast, sub-
jects appeared “stunned” by the impact at half
this force in other systems. In aircraft par-
ticularly, this feature might have critical evac-
uation implications. Analysis of individual
sequential frames of the high-speed 16 mm. mo-
tion picture films indicates clearly that the
subject is well restrained in an upright position
during the impact, although the air bag obscures
portions of the subject during the deceleration.
Rebound effect did occur in these tests, and in
several instances the animal’s head hyperextended
to the side of the seat as it rebounded back
against the seat, missing it partially to the right.
In an actual automobile seat this might be in-
consequential, and was not observed to produce
direct injury. It should be noted, in all fairness,
that although considerable research has gone into
volumetric requirements, gaseous compositions,
exhaust port sizing, and materials to produce
the most optimum air bag for human use, the
scaled-down versions used in these tests were
constructed in 48 hours prior to delivery and the
ports exhaust requirements were estimated. All
air bags in these tests performed as designed.

IV. Results

With regard to the air-bag study described
above, it must be emphasized that our tests have
only attempted to probe one aspect of this re-
straint’s effectiveness. There are a number of
unknowns for which data must be obtained be-
fore a realistic evaluation can be made. Some



uoyepuy pue jouduy] Jo JuEMOW 7B 489} JUIwIYSEI Beq-ITy *) BaNoTT

15



EXPERIMENTAL IMPACT PROTECTION WITH
ADVANCED RESTRAINT SYSTEMS:

Preliminary Primate Tests with Air Bag and Inertia Reel/Inverted-Y Yoke Torso Harness

I. Introduction

Protection and survival of motor vehicle oc-
cupants, as well as those of aircraft, spacecraft,
and other types of vehicles exposed to crash
impact forces, are dependent upon a number of
environmental factors. In any vehicle environ-
ment, however, the occupant restraint system is
of primary importance. Research to prevent or
reduce injury during impact, and to prevent
ejection in ground vehicle accidents is related
to similar problems first met in the air. Pos-
sibly the first use made of a restraint was by
Pilatre de Rozier—in the form of hanging
rather apprehensively onto a guy rope —in his
first tethered balloon flight in France in 1783."

It is naive, however, to consider that aircraft
restraint developments can be simply transferred
into automobiles with the same degree of success.
While it is true that the major research efforts
and system advances were by the aircraft. in-
dustry during the past 25 years, (probably dating
back to the first ejection seat experiments in
Germany in 1939)* it should be noted that there
are significant differences, often overlooked, in
application, requirements, and environments as
well as in respective populations for which they
are designed. An Astronaut couch, for example,
is specifically designed for a narrow range of
healthy young males, representing only the 25th-
80th percentile American male stature,**? while
the automobile occupant population covers a
wide range from infants to the very elderly and
those with disabling infirmities.

The hypothesis behind most restraint studies
is that the majority of deaths and injuries in

‘The work reported in this study was supported by the Civil
Aeromedical Institute, Federal Aviation Administration, De-
partment of ‘Transportation, Oklahoma City, utilizing the
facilities and cooperation of the 6571st Aeromedical Research
Laboratory, Holloman AFB, New Mexico. ‘The opinions ex-
pressed are those of the authors, and do not necessarily reflect
the official viewpoints of the several organizations concerned.

accidents could be prevented or considerably de-
creased by safely restraining the occupant if the
accident could not be prevented, (# #4 ethers)
Some of the major differences between aircraft
and automotive restraint systems are as follows.
In aircraft, the direction of applied force (body
orientation) is rarely in direction(s) other than
forward (—Gx) application, while in automo-
biles protection against rear and side impacts
also must be considered. The forces of impact.
are often greater in an automobile* than in many
survivable aircraft crashes*?* with a much
shorter vehicle deceleration distance, time dura-
tion, and resultant higher loads and onset rates
on the occupant. Seat-belt webbing in civil air-
craft tensile strength requirements are 2,250
pounds for single occupancy but only 1,500
pounds single occupancy strength for whole belt
assembly.*t Military (Air Force and Navy)
webbing requirements are now 5,500 pounds
minimum tensile strength,‘**" although in prac-
tice most aircraft in the field still have the 2,000
pounds webbing previously required.*? In con-
trast, automobile seat belt tensile strength, re-
quired by regulation to meet 6,000 pounds tension
loads,?? usually exceeds this by a significant
margin, and sometimes 8,000 pounds is observed
in actual crash tests.** In aircraft, military and
civil, few would think of not fastening the safety
belt, yet in automobiles in which seat belts are
available, numerous studies have shown that
fewer than 30%***3+ and probably closer to
15-20%** bother to use the restraint provided.
The most effective aircraft restraint systems
are found in military aircraft having cockpits
designed to withstand 40g. impact. Another
critical difference between the aircraft and auto-
motive restraint system is mass-production qual-
ity control: for 1968 automobiles alone, 352
million feet, of webbing were required for 16
million torso belts and 48 million lap belts, and



ACKNOWLEDGMENTS

The authors wish to acknowledge the cooperation of the following individuals and
their direct contribution through engineering, biomedical and scientific assistance to this
study: Richart Chute and Richard Saul of Eaton, Yale and Towne, Inc., Southfield,
Michigan, suppliers of the experimental air bag system; George Johannessen and David
Lang, Hamill Mfg. Co., for providing the inertia reels; Richard Chandler and Capt.
Peter Hanson, USAF 6571st Aeromedical Research Laboratory, Holloman AFB, New
Mexico; Ool. G. Townley Price, D.V.M., U.S.A. (RET) and Miss Mackie Allgood, Civil
Aeromedical Institute, Federal Aviation Administration, Department of Transportation,
Oklahoma City, Oklahoma; Allan A. Katzberg, Ph.D., Chairman, Department of Anatomy,
Southwest Foundation for Research and Education, San Antonio, Texas; Professor
Warren M. Crosby, M.D., University of Oklahoma School of Medicine, Oklahoma City,
Oklahoma; Jeffry Life and Bruce Pince, Space/Defense Corporation, Birmingham,
Michigan; and Gaither Bynum, New Mexico State College. Particular recognition is
given for the generous efforts of Land-Air Division technical team who sacrificed per-
sonal time and worked under difficult conditions to complete this study. Finally the
authors wish to thank Raphael Cilento, M.D., for neurological examination for brain
trauma; and F. Ross Burkhill, M.D., Dearborn, Michigan, for radiographic analysis.

AUTHORS:

Richard G. Snyder, Ph.D., Highway Safety Research Institute, Institute of Science
and Technology, University of Michigan, Ann Arbor, Michigan.

Joseph W. Young, A.M., Civil Aeromedical Institute, Federal Aviation Administra-
tion, Oklahoma City, Olkahoma.

Clyde C. Snow, Ph.D., Civil Aeromedical Institute, Federal Aviation Administration,
Oklahoma City, Oklahoma.

Qualified requesters 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.


1500

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TIME (SECONDS)

Ficure 5. Comparison of belt loads in baboon subjects;

The significance of these injuries is probably
related to the g. exposure levels since gross
structural damage, internally and superficially,
was not evident. It is interesting to note that
subject Number 3598, exposed to 46g. was ex-
posed to this g. level in three consecutive impacts
at 60- and 45-minute intervals. Although this
subject sustained a ruptured bladder, which is
considered serious, the only other pathology was
the typical dural congestion. Anterior-posterior
and lateral view radiographic studies of the
thorax, abdomen, pelvis, neck, skull, and ex-
tremities revealed no evidence of skeletal injury.

To reinforce the macroscopic and microscopic
autopsy data, brain tissue was further studied
at the cellular level through electron-microscopy,
which confirmed the trauma indicated in Table
Iv.

To search for further biochemical indicators
of impact stress or damage to body tissues as a
result of these tests, blood samples were taken
from 5-10 minutes prior to impact, 5-15 minutes
post-impact, and in the case of the three animals
observed 4 and 12 weeks post-impact, at 7-day
intervals for 1 month. The hematology is sum-
marized in Table V. Specific techniques em-
ployed are those provided in detail in the study
of Life,** and general methods are as previously

11

80g. impact with six restraint systems.

noted in the materials and methods discussion.
Although the sample was too small to be sta-
tistically significant, some trends should be
pointed out.

Glucose is grossly elevated in stress as a result
of sympathetic mechanisms. The three animals
observed for 1 to 8 months post-impact clearly
reacted to the pre-impact handling as a stressful
event; gluclose was greatly elevated over its
normal level of about 100 mg. percent. After
impact it went even higher, to fall again sharply
post-impact. The abnormally high-CHO figures
for the other blood determinations are probably
an artifact of the time involved in shipment of
these particular blood samples, since a dilution
error was not probable.

In the three animals observed long term,
hemoglobin (mg. %) values were observed to
rise post-impact, and it is hypothesized that this
is a compensatory event secondary to traumatic
injury. Red blood cells in this series were re-
duced post-impact, except for a rise observed in
one animal (Number 3597), which might be
attributed to a compensatory release of RBC’s
from reserves. Changes in circulatory ionic
calcium (as a result of trauma) may be produced
either by blood loss or trauma to hard tissue.
Since the elevation in blood calcium seems highest



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