tance of fall from 46 feet) above 50 ft/sec, how-
ever, the feet-first {+Gz,) impacts had a sig-
nificantly higher survival incidence. Aside from
the two parachute failures, which are assumed
to be terminal-velocity impacts, four other cases
of survival occurred in the feet-first body ori-
entation [at 100, 102, 111, and 116 ft/sec (133
ft/sec standard velocity) ].

The upper survival limits of human tolerance
to impact velocity in water are evidently close to
100 ft/sec (68.2 mph) corrected velocity, or the
equivalent of a 186-foot free-fall. As is illus-
trated in Figure 3, there is a fairly constant
survival frequency distribution up to 100 ft/sec,
but survival incidence at higher levels drops off
abruptly and includes younger individuals only.
Regrouping these cases of survival by arbitrary
class intervals, as in Figure 4, shows this pattern
with an abrupt peak at a 100-ft/sec impact ve-
locity. Twenty-five percent of these individuals
survived extreme impact in water at from 90 to
100 ft/sec, while only 4.9% survived a greater
impact at any level.

Previous studies involving human impacts on
other surfaces, such as concrete, steel, and soil,
have demonstrated no clear-cut correlation be-
tween the distance of fall (and impact velocity)
and degree of resulting trauma. The 44 cases of
water impact studied in this investigation also
show no correlation of velocity (distance) with
injury. In one case, for example, serious injuries
occurred from a 55-foot free-fall (velocity 58 ft/
sec, or 39,5 mph), while in others of much higher
velocity, minimal contusions or no injuries were
reported. No clinical injuries were reported in
one case at 95 ft/sec (64.8 mph) impact and an-
other 178-foot feet-first fall impacting at 97-
ft/sec (or 66.1 mph) velocity.

Patterns of injury were found to vary with
the direction of force or body orientation. This
is shown in Figure 5, in which gross injuries
were summed up into four arbitrary classifica-
tions—no injury, external tissue injury, skeletal
injury, and injury to internal organs, tissues, and
systems. Of 34 cases of feet-first (+Gz) impact,
which was the most commonly survived body
orientation, 11, or 32.3%, had no associated
trauma clinically reported. In all other body
orientations, some injury occurred. The most
typical injury in feet-first impact involved con-
tusions to thighs and buttocks, compression frac-
tures (particularly to the twelfth thoracic and

first lumbar vertebra), shock, and hemorrhaging
of the lung.

Besides the high incidence of compression
fractures in this impact position bilateral mid-
shaft fractures to the tibia and fibia, femur, or
humerus occurred. In one case, a comminuted
fracture of the scapula and distal clavicle oc-
curred when the individual landed with one arm
down, forming a fulcrum against the impact
force. Fracture patterns in water are distinctly
different from those that occur on concrete,
steel, or soil surfaces since not one case of foot
or ankle injury was reported for the former,
while in the latter a high frequency of frac-
tured ankles in feet-first impacts has been found.
The midshaft fractures also differ from the pat-
tern most typical of impacting nonwater sur-
faces. This probably occurs as a function of
pressure changes as the body angles into the
water, literally snapping the long bones unless
the legs are kept together. Extensive internal
trauma occurred in only five individuals (14.4%),
but the lung, kidney, spleen, liver and bladder
appeared most susceptible to injury. One case,
although fatal 48 hours later, showed upon
autopsy a ruptured liver, spleen, and intercostal
artery. Often internal trauma of a more minor
nature, such as tearing of organ membranes,
may remain undiagnosed, as is indicated by
numerous autopies in our files. Other studies
of human water impacts have also confirmed the
high incidence of external skin lesions,*® and
noted the extensive injury to internal organs in
survivable impact, 1% 2 2 22

Impacts in the five other positions identified
are reported but, since only one to three occur-
ences were obtained for each, the results must
be interpreted with caution. It does appear that
internal trauma is significantly more frequent in
any position of impact other than feet-first.
Only 1 (head-first) out of 10 cases of impact in
another position failed to result in internal in-
jury, with renal hematoma being most common.
Two individuals striking buttocks first, one at
near terminal velocity, were both injured, re-
ceiving similar injuries as those impacting feet-
first, except for one who landed on his buttocks
and right side, thus receiving a fractured second
lumbar vertebra transverse process and fracture
of 10 ribs,

Other data were secured in investigation of
each case, such as clothing worn, physical data,



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these theoretical values provide two divergent
lines, in most cases (except for trained profes-
sional divers), the minimum line will show sev-
eral peaks after initial impact and may even
rapidly approach the secondary maximum levels
due to change of body orientation after initial
impact.

In water impacts, factors not usually associ-
ated with ther types of surfaces may play an
important role in determining survival. For ex-
ample, the surface of the water may be smooth
and horizontal to the falling body or through
waves and throughs form a surface angle nearly
perpendicular and thus parallel to the body.
Even in inland waters, waves may be a- factor.
Velocity of the current, while a relatively minor

factor at impact, is immediately important to ©

survival. Meteorological conditions thus are
often of more importance to water impacts than
other impacted surfaces less subject to variation.
Additional forces acting in a water impact may
involve such factors as friction, tumbling, water
upslope, resultant forces, and even shear due to
current.

While most bridge-jumpers are attempting to
commit suicide, and others fall accidentally, it
should be noted that there are two further groups
of voluntary jumpers, both gamblers in a sense.
The first of these are those, usually young males,
who jump on a bet. Strangely enough, we have
only one case of a known “bettor” who has been
killed. But frustratingly enough, there are sel-
dom records of such cases, and the individuals
usually, presumably clutching their winnings,
elude official searchers. In recent cases of this
nature, a Rhode Island youth leaped 60 feet from
a bridge while his companion stood by yelling
encouragement, and another jumped 135 feet
and was last seen swimming to a pier. In Ohio,
a 17-year-old boy jumped 65 feet, and in New
York a 32-year-old man jumped 107-feet—for
the third time—from a bridge on which 67 other
jumpers have been killed.

There have also been several men who make
a somewhat precarious living as stunt-jumpers,
and their techniques may provide useful infor-
mation. In 1961, the present unofficial world
record for a still-water dive was made by one
such individual diving 109 feet 7 inches into the
Sea Circus pool at Pacific Ocean Park, Santa
Monica—the equivalent of an 11-story jump.
This same individual has jumped 155 feet into

moving water. Perhaps the champion voluntary
jumper was Ray Woods, who jumped all over
the place in the mid-thirties, jumping 165 feet
from the Aurora Bridge in Seattle in 1935 and
surviving, with back injuries that ended his car-
reer, a fantastic dive of 186 feet from the San
Francisco-Oakland Bay Bridge in 1937. A third
diver, during opening ceremonies of the Mt.
Hope Bridge at Portsmouth, Rhode Island, in
1927, jumped 154 feet, wearing a padded suit
and helmet.

In various parts of the world other high divers
frequently dive great distances. In Mexico, for
example, professionals regularly dive distances of
100 and 135 feet from a Pacific Ocean cliff at
Acapulco, Mexico. One of these has dived this
distance approximately 26,000 time in 25 years of
diving. A study by Schneider, Papo, and Al-
verez*? notes that no fatalities have occurred,
except to an American college diver who at-
tempted to duplicate this feat. Various injuries
have been incurred, however, including fractures
of the metacarpals or radius and ulna, caused by
the extremities striking the head on impact with
the water. Compression fractures were found in
four of six divers examined, involving the fifth
thoracic vertebra in three cases, the sixth thoracic
vertebra in two cases, and the second, third,
fourth, and seventh thoracic vertebra. Along
with well-developed neck muscles, their success is
attributed to either extending the arms or locking
the fingers so as to “strike so that their necks
are slightly hyperextended and the point of im-
pact is at the bregma.” ?’ In the “hands-apart”
impact the force was mainly taken on the head,
while with the hands locked cavitation resulted
in less force on the head.

The leader of this group of divers noted that
in diving from less than 30 feet a diver should
remain relaxed; over 30 feet he “must be as rigid
as possible to take up the blow.”** Such stunt
dives do emphasize that a water impact can be
repeatedly made at velocities up to 86 ft/sec
with no or minimal injury if proper body ori-
entation is maintained. These individuals, how-
ever, are all young males, highly trained, and in
top physical condition.

Previous experimental water impacts with an-
esthetized guinea pigs, in an attempt to reproduce
trauma in free-fall of the two 1954 Comet Air-
line ruptures that spilled occupants into the sea,
resulted in the conclusion that severe internal in-



meteorological conditions (depth of water, wind,
current, and tide conditions), and whether the
subject had been intoxicated, under the sedation
of drugs, or had a psychiatric history. In three
cases, jump boots and other protective clothing
such as helmets, a water skier’s float, or heavy
clothing may have contributed to preventing fur-
ther injuries. Several individuals, however, care-
fully shed clothing prior to jumping. Although
it is felt that knowledge of the possible influence
of drugs, alcohol, or certain psychiatric condi-
tions would be useful for comparisons in their
relationship to impact survival, the clinical data
are not specific enough for a valid comparison.
Although 14 individuals were noted to be al-
coholics, intoxicated, or to have been drinking
prior to impact, in no case was a blood-alcohol
determination made that would allow more ob-
jective comparison with presumably sober
jumpers. In addition, 15 individuals, including
some of the intoxicated ones, were also diagnosed
to have various mental abnormalities, the most
common of which was schizophrenia. Although
previous work*® has suggested a relationship
between relaxed muscle tonus, as may occur in
the intoxicated individual, and impact. survival,
the data obtained to date in water impacts are
not felt to be adequate for inclusion.

IV. Discussion.

While it has generally been considered that the
wider the distribution of force over the body’s
surface, the less the unit force, and thus the
greater distribution of energy (and survival ca-
pability), this one factor by itself is somewhat
misleading, particularly in regard to water im-
pact. For example, practically everyone has
experienced the “belly flopper,” which is a dis-
tribution of force over a wide surface area. Yet
a clean dive or jump into water, representing a
much smaller surface area and thus greater con-
centration of force, leaves little or no sting. The
difference, of course, is in the deformation char-
acteristics of the water, and thus the distance
and time duration of deceleration. In the “belly
flopper,” the time duration of impact is. short,
and “braking action” due to the greater surface
area results in shorter stopping distance, while
in the clean dive the time duration of impact is
greater since there is less braking action due to
decreased body surface area and greater depth
penetration. While this may seem obvious and

elementary, it is a basic factor in water-impact
survival,

Velocity at impact is used in this study to
indicate magnitude of force because it can be
accurately calculated in unimpeded free-falls,
providing a valid basis of relative fall severity.
Unlike falls onto hard surfaces such as concrete,
however, the deformation characteristics of each
impact cannot be precisely determined since the
displacement is not known. Thus, time duration,
a most important factor in deceleration calcula-
tions, cannnot be accurately determined. In
general, the time duration, and rate of change
of velocity, in water impacts is of much longer
duration than in impacts on solid surfaces.

Stopping distance will vary with the body or-
ientation at impact, being much greater in feet-
or head-first impacts, and less, because of the
greater surface area, in lateral or transverse im-
pacts. Evidence does seem to indicate, however,
that even from great heights velocity is rapidly
lost in water. *** 2° Experiments by Neuriter
and Trey, for example, showed that in head-
first dives into water from 238 em (7’9’’) dum-
mies (mass 3.38 kg, specific gravity 1.08) had
lost 71% of their velocity by a depth of only **
16 cm (6.8’’). 7

We intend to conduct further experiments and
try to duplicate with instrumented subjects spe-
cific conditions of free-fall in order to caluate
time duration sand estimate G forces acting upon
the body. Preliminary calculations involving
stagnation theory indicate that G forces upon
the body in water impact are five to seven times
greater in the prone (+Gx), supine (—Gx), or
lateral (Gy) body orientation than head-first
(—Gz) or feet-first (+Gz) impacts. Mathe-
matical estimates by Earley” predict a magni-
tude of force in feet or head-first impacts of ap-
proximately 3.5 G at 20 ft/sec, compared to 18.6
G in a flat. configuration, 6.0 G versus 40 G at
30 ft/sec, 16 G compared to 112 G at 50 ft/sec,
and 43 G compared to 300 G at 80 ft/sec. If cor-
rect, these approximate theoretical values sug-
gest a major reason why incidence of water-
impact survival is so much greater in head- or
feet-first. configurations. For the same distance
of fall and same velocity, an individual may
thus protect himself by roughly 50% to 70%
from G forces acting on the body by presenting
a minimal surface area at impaction.

It should also be noted that while plots of


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13.

14.

REFERENCES

Preston, G. M., and Pesman, G. J. NACA TN 4158.
Accelerations in Transport-Airplane Crashes. 1958.
Federal Aviation Agency. Crash Tests of Douglas
DC-7 and Lockheed 1649 Transport Aircraft (Un-
published data, 1964).

Snow, C. Human Factors in Aircraft Crash In-
vestigation. Amer. J. Phys. Anthrop., ns. 21(3) :428
(1962).

. Swearingen, J. J., McFadden, E. B., Garner, J. D.

and Blethrow, J. G. Human Voluntary Tolerance
to Vertical Impact, Aerospace Medicine 31(12):
989-998 (1960).

Coleman, T. L., and Walker, W. G. NACA TN 3871.
Analysis of Accelerations, Gust Velocities, and Air-
speeds From Operations of a Twin-Engine Trans-
port Airplane on a Transcontinental Route from
1950 to 1952. 1955.

Hunter, P. A., and Walker, W. G., NASA TN D-1925.
An Analysis of VG and VGH Operational Data
From A Twin-Engine Turboprop Transport Airplane.
1963.

Ragland, S., Chambers, R. M., Crosbie, R. J., and
Hitchcock, L., Jr, NADC-ML-6411, Simulation and
Effects of Severe Turbulence on Jet Airline Pilots,
Aviation Medical Acceleration Laboratory, Johns-
ville, Pa. 1964,

Hatch, H. G, NASA TN D-39,. Effects of Water-
Landing Impact on an Orbited Capsule From the
Standpoint of Occupant Protection. 1959.

Mueller, W. H., and Malakoff, J. L., Water Impact
of Manned Spacecraft, ARS Journal 31(12) :1751-
1760 (1961).

Donlon, . J., Project Mercury, Psycho-Physiological
Aspects of Space Flight, Symposium, School of Avi-
ation Medicine, USAF Aerospace Medical Center,
Texas. 1960.

Gould, G. M., and Pyle, W. L. Anomalies and Ouri-
osities of Medicine, p. 703, Philadelphia, Saunders.
1901.

Snyder, R. G., CARI Report No. 62-19. A Case of
Survival of Extreme Vertical Impact in Seated Posi-
tion, Civil Aeromedical Research Institute, Federal
Aviation Agency, Oklahoma City, Oklahoma. 1962.
Snyder, R. G., Human Tolerances to Extreme Im-
pacts in Free Fall, Aerospace Medicine 34(8) :695—
709. (1963).
Snyder, R. G.
ical Research

Infanticide and Aurora 7: Aeromed-
in Extreme Human Deceleration,

15.

16.

17.

18.

19.

20.

21.

22,

23,

24,

26.

27.

28.

29.

Amer J. Phys. Anthrop. ns, 21(3) :428 (1963).
Kienow, K. K., and Snyder, R. G. The Mechanics of
Collisions of Plastic Bodies Impacting Hlasto-Plastic
Material of High Velocities (In Prepration, 1964).
Early, J. C. Body Terminal Velocity. (Unpublished
the Velocity of Falling Human Bodies (unpublished
MS, 1964).

Cotner, J. S. Analysis of Air Resistance Effects on

data, 1964).
Balazs, G. igentunmliche Hautbe zunde nach
Sturz ins Wasser, Deutsche Zeitschrift fur die

gesamte gerichtliche medizin 21:515-519 (1983).
Merkel, H. Funren Absprunge aus Grosserer Hohe
ins Wasser zu Beschadigungen innerer Organe,
Deutsche Ztschr. F.D. Ges. Gerichtl. Med, 8 :517-
522 (1926).

Kernback, J., and Hurghisiu, V. Contributo allo
studio della caduta, Dell ‘Archivio di Antropologia
Criminale Psichiatria e Medicina Legale 57 :26-41
(1937).

Ziemke, E. Zum Tode Durch Sprung ins Wasser
aus Grosser Hohe, Deutsche Atschr. F. D. Ges.
Gerichtl. Med, 12:346-360 (1928).

Steward, W. D. Lung Injury by Impact With A
Water Surface, Nature 175:504-505 (1955).

Klose, A., and Neuriter, F. Zum Tode Durch Sturz
ins Wasser, Beitraege Zur Gerichtlichen Medizin
9 69-75 (1929).

Neuriter, F. V. Weitere Experimente zum Sturz ins
Wasser, Deutsche Zeitschrift Fur Die Gesamte Ger-
ichtliche Medizin 16:305-311 (1931).

‘Trilling, L. The Impact of a Body on a Water
Surface at an Arbitrary Angle, J. Appl. Phys. 21(1)
161-170 (1950).

Neuriter, F. V., and Trey, F. Zum Sturtz ins Was-
ser, Deutsche Zeitschrift fur die Gesamte Gericht-
liche Medizin 14:37-48 (1929).

Schneider, R. G., Papo, M., and Alvarez, ©. 8, The
Effects of Chronic Recurrent Spinal Trauma in
High Diving, A Study of Acapulco’s Divers, J. Bone
and Joint Surg. 44-A(4) :648-656 (1962),
Armstrong, J. A., Fryer, D. 1, Stewart, W. K., and
Whittingham, H. E. Interpretation of Injuries in the
Comet Aircraft Disasters, Lancet 268 (6875) :1143
(1955).

Stewart, W. K., Spells, K. E., and Armstrong, J. A.
Lung Injury by Impact With a Water Surface
Nature 175 :504-505 (1955).



AM 65-12

SURVIVAL OF HIGH-VELOCITY
FREE-FALLS IN WATER

Richard G. Snyder, Ph.D.

Approved by Released by
Stantey A MeNo-hlLe Wy d Wake
Srantey R. Monter, M.D. M. S. Wurre, M.D.
Drecror, CARI Feperat Arr Surcron
April 1965

FEDERAL AVIATION AGENCY

Office of Aviation Medicine
Civil Aeromedical Research Institute
Oklahoma City, Oklahoma



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juries may be expected in extreme water impact
and that the critical velocity for guinea pigs was
about 104 ft/sec.*® Critical incident velocities
for the mouse (118 ft/sec), guinea pig (99 ft/
sec), and man (94 ft/sec) were predicted in a
separate study.?? Both of these previous the-
oretical and animal impact studies are in general
agreement with the findings of these human free-
falls in water.

The etiology of these falls, particularly in cases
involving mental disorder, alcohol or drugs, may
be of importance in evaluating each case of sur-
vival. As note previously, however, discrete data
as provided by most clinical histories do not pro-
vide objective enough data in these water im-
pacts to more than suggest a relationship. Many
more intoxicated schizophrenics, for example,
may survive extreme water impacts, but this
cannot be scientifically interpreted without
knowledge of the total incidence—do propor-
tionately more intoxicated schizophrenics jump—
and are proportionately more thus also fatally
injured? These are questions to be investigated
in subsequent analysis of our fatal cases and,
particularly, of the autopsy cases.

Vv. Summary.

Forty-four cases of free-falls survived by in-
dividuals impacting water environments under
conditions of high velocity (50 to 176 ft/sec)
have been intensively investigated and analyzed.
Ages varied from 7 to 80 years and the study
included 34 males and 10 females. The falls
occurred in 17 different states primarily over a
3-year period, and included attempted suicides,
accidental falls from high structures, and para-
chute failures in jumping or evacuating from
aircraft.

It was found that:

A. The most survivable body orientation, by
a factor of five to seven, is in a feet-first (+Gz)
impact with arms over the head, due to increased
time duration of deceleration caused by minimal
body-surface-area braking action.

B. Critical velocity for human survival of
water impact in the feet-first body position ap-
pears to be at about 100 ft/sec. Four cases
ranged from 100 to 116 ft/sec, and in two cases
terminal velocity was approached. The highest
impact velocity survived was 87 ft/sec, in the
lateral (—Gy) body orientation, 88 ft/sec in the

prone (—Gx) position, 93 ft/sec supine (+Gx),
and 97 ft/sec head-first (—Gz). (Note that ve-
locity calculations were corrected for aerody-
namic drag and thus are lower than standard

values.)

C. No correlation between velocity (or distance
of fall )and degree of trauma was found; rather,
injuries appeared to be more dependent upon
body position at all levels of force. Severe in-
juries (and fatalities )occurred at low levels
of velocity, while some cases of minimal or no
injury occurred at very high-impact velocities.

D. The pattern of impact injuries in the feet-
and buttocks-first position showed a high in-
cidence (68%) of fractures, with compression
fractures to the first lumbar and twelfth thoracic
vertebrae the most common single injury. Bi-
lateral midshaft fractures were also typical in
cases of fracture. Only 14% received internal
trauma, with lung hemorrhaging being most fre-
quent. Sixty-eight percent also received a dis-
tinctive pattern of contusions involving primar-
ily the thigh and buttocks area. Eleven indi-
viduals of thirty-four (33%) received no clinical
trauma in feet-first impacts. Contrary to impact
findings on solid surfaces, no injuries to the feet
or ankles occurred.

E. In lateral and transverse (prone and spine)
impacts in water, all individuals received in-
juries with 100% incidence of internal trauma
(with renal hematoma most prevalent single in-
jury )and 100% body contusions. Rib and
basalar skull fractures occurred in both lateral
impacts, and compression fracture of the first
lumbar and twelfth thoracic vertebrae occurred
in the supine position, with no fractures in the
one prone impact.

F. There was a distinct correlation of age with
survival as the level of velocity was increased,
with both sexes showing higher impacts survived
at ages 20 to 36; however, since fatal cases were
not included, this could also reflect a higher ex-
posure rate.

G. Sex did not appear to a factor in survival.
H. Other factors considered to be of varying
influence on water-impact survival included wind
direction and velocity, water condition and cur-
rent, protective clothing, physical condition, men-
tal condition, and influence of alcohol or drugs.



protection and survival of the individual involved
in abrupt deceleration occurences,

II. Materials and Method.

During the past 3 years, cases have been care-
fully documented of voluntary and involuntary
free-fall ,with particular emphasis upon survival.
12,1814 15 Of some 18,000 cases during this time
involving survived free-falls, and 7,000 fatal in-
cidents of which we have knowledge, 200 sur-
vived cases to date have been selected for more
intensive investigation. Forty-four cases of hu-
man impaction with water surfaces in unimpeded
free-falls of 55 feet (velocity of 52 ft/sec, or
35.5 mph), or higher, are included. In each
case, a site investigation was made, actual meas-
urement made of the distance of the fall, inter-
views conducted with the subject and witnesses,
photographs and police reports obtained, and the
complete medical history forwarded, including
copies of any x-rays. From these data, calcu-
lations of free-fall velocity and direction of
forces were obtained from analysis of the medi-
cal and biophysical evidence.

This population represents a highly select
group of individuals in that they had to have sur-
vived an extreme impact of over 50 ft/sec on a
water surface. Additionally, except for four
eases occurring prior to 1962, they represent a
high proportion (96%) of all known survivals
under these specific conditions during the past 3
years. It must be emphasized that the total
population that fell under these conditions is
not considered here since fatal cases are not in-
cluded. Therefore, the actual incidence of sur-
vival is not shown but rather a discrete analysis
of the micropopulation that did survive. The
following data must be used with this limitation
in mind.

IIL. Results.

The 44 falls investigated occurred in 17 differ-
ent states (Figure 1) with 9 in Washington, 7 in
Massachusetts, and 5 each in California and
New York. All but 4 cases involved falls from
bridges, with 24 of these being suicide attempts
(Figure 2).

Bridge construction and painting accounts for
a high incidence of falls from great heights into
water. Towers of the Golden Gate Bridge, for
example, jut 746 feet. over the San Francisco
Bay, while the towers of the New Verrazano-

©

Narrows Bridge between Staten Island and
Brooklyn are 690 feet over New York Harbor,
and other bridges (Glen Canyon Dam Bridge)
are even higher, providing constant exposure to
the hazards of free-falls for such workers. (Al-
though two cases of parachute failures were ob-
tained, including one involving an ejection from
15,000 feet over the Pacific Ocean and a second,
a female sky-diver falling 2,550 feet into a
pond, these are not included here since aerody-
namic drag could not be accurately determined
in either case.) In each case, measurement of the
distance of the fall allowed calculation of the
velocity. Note that standard velocity in each
case has been corrected for air drag at sea level
(standard pressure, assumed body terminal ve-
locity of 120 mph).

The calculated values used in this study are
thus lower, but more realistic than that provided
by the standard formula (V = ¥V 2g8) alone,
since preliminary tests and mathematical calcu-
lations have shown that clothing such as jackets
or skirts do provide additional drag. Correc-
tions by Earley *® are based upon Cotner’s””
closed-form solution for velocity at impact for
fall cases where body position and clothing was
observed to be constant. A mean body build of
4.7 CyS (drag coefficient X body surface area)
was utilized.

In Figure 3, velocity is plotted against the
variables of age, sex, and body orientation (di-
rection of force) at impact. There were 34 males
and 10 females in this study. Although age ex-
tremes of 7 to 80 years were involved, 69% of
the subjects were between ages 20 and 40, and
all of those surviving impacts greater than 100
ft/sec were between 7 and 26 years of age.
Seven, or 70%, of the females surviving these
extreme impacts were between ages 20 and 29.
There is thus some correlation with age, with a
greater number of younger individuals, both
male and female, having survived at the higher
impact velocities. This probably reflects physical
condition to some extent, although a subjective
assessment was not available; however, this does
not present the total incidence of survival, which
would show whether this could be due to greater
exposure at higher velocities.

Survival occurred in various body positions
up to 87 ft/sec lateral (—G,), 88 ft/sec prone
(—Gx), 93 ft/sec supine (+Gx), and 97 ft/sec
head-first (—Gz). At all levels of velocity (dis-


SURVIVAL OF HIGH-VELOCITY FREE-FALLS IN WATER

I. Introduction,

Protection and survival of the aviation popu-
lation involves many interrelated facets of vary-
ing interest to the design engineer, human-
factors specialist, and aeromedical scientist.
Progress in most of these areas eventually is
dependent upon basic knowledge of human capa-
bilities and tolerances to the varied, and often
hostile, environments imposed by flight. One
such area is that of human tolerances to impact
forces, in which considerable work has been done
involving the horizontal component at subin-
jurious levels. Relatively little is known, how-
ever, concerning human-tissue responses to ver-
tical forces, partially at the higher sublethal
levels.

High vertical forces are most often encountered
during crash landings,'? evaculation from the
aircraft after it has stopped,** or during ex-
treme turbulence in flight. %% "Such forces are
often unintentionally encountered by parachutists
who are unfortunate enough to be dependent upon
ailing equipment. They may also be anticipated
in VTOL-type-aircraft launch and landing ac-
cidents.

Quite often the material impacted in high-
velocity vertical impact consists of a water sur-
face; thus, both the general incidence and pe-
ouliar characteristics of water survival merit
study in greater detail. One immediate applica-
tion for such knowledge is in the impact survival
of astronauts exposed to extremely abrupt de-
celerations upon water impact due to retro-
braking equipment failure. In re-entry a drogue
failure may result in a splash-down of 180 ft/
sec (88.6 mph) or more. Impacts in water
of 25,000 G/sec, with a peak of 60 G, *° or
100 G land impacts * for the Mercury capsule
have been predicted. In this regard it is im-
perative to know the design limitations of the
human body to such forces before a judgment
can be made as to “how great an impact is sur-
vivable.” This is far from a simple question

to answer and dependent upon a number of inter-
related and variable conditions. This study is
one attempt to initially define some of these vari-
ables and find means of predicting human sur-
vival in water impact.

Human falls into water from great heights
have been recorded throughout history. These
have not always been successful, and perhaps the
mythical fall of Icarus into the sea as he at-
tempted to escape from Crete with his father,
Daedalus, was the first. Although early medical
references, such as Gould and Pyle’s Anomalies
and Curiosities of Medicine of 1901," provide
several cases of “Remarkable falls” into water,
including that of a sailor who survived a fall
of 120 feet from the topgallant of an East India
merchant vessel, early falls do not compare with
the much greater heights man commonly falls
from today. Man himself has provided the
means in constructing tall bridges, towers, air-
craft, and other suitable structures from which
he daily jumps, falls, or is pushed. These inci-
dents may provide valid scientific information
that is unobtainable through laboratory experi-
mentation ‘because of the obvious limits human
voluntary subjects can be exposed to in impact.
On the other hand, free-fall cases may present
involuntary experiments in which the subject
greatly exceeds these laboratory limits. In se-
lected cases, in which investigation results in
documentation of the major variables, certain
conclusions are valid. As this study progresses
and sufficient cases occur to reproduce and rein-
force the evidence to date, definite patterns of
trauma should become evident, as well as discrete
indications of the major variables influencing
human survival of extreme impact. forces.

There is apparently a wide, overlapping, and
variable area between human limits of minimal
injury as found in the laboratory and the ex-
treme limits of survival. Although this has been
explored to date to only a limited extent, knowl-
edge of the variables and problems involved
should be of considerable application to increased



ACKNOWLEDGMENTS

The author gratefully wishes to acknowledge the generous assistance
provided in this study by Joseph W. Young, A.M., and Clyde Snow, MLS.,
Physical Anthropology Laboratory, CARI; John C. Earley, Chief, Dynamics
Engineering Laboratory, CARI; Robert Dille, M.D., Regional Flight Sur-
geon, Western Region, FAA; Jim Scow, M.D., Langley Research Center,
National Aeronautics and Space Administration; John Ice, Technical Editor,
Acceleration Program, CARI; Laura Newell, Ph.D., Dept. of Anthropology,
University of Washington; and Capt. T. F. Parnow, California Highway
Patrol. In addition, this study would not have been possible without the
extensive cooperation and assistance provided by individual physicians,
federal, state, and local police agencies, witnesses, and the subjects themselves.