decompression time tables should serve as a basis
for selecting oxygen equipment for passengers
and crew flying in small pressurized aircraft.

Figures 5 through 7 present sequence pictures
of representative ejections of the four sizes of
dummies.

IV. Conclusions.
In view of the data presented in this study,

it is obvious that the volumes of even small
pressurized aircraft are sufficient to cause ejec-
tions from aircraft, fatal injuries from head
impact, concussion and unconsciousness, and in
some cases even lung rupture.

For these reasons considerations should be
given to equipping all pressurized aircraft, large
or small, with double-pane windows and plug-
type exits.

References

1, Lurr, Urricn C. and Bancrorr, Ricuarp W.: Trans-
thoracic Pressure in Man During Rapid Decompres-
sion, USAF School of Aviation Medicine, Randolph
AFB, Texas. Report 56-67, August 1956.

2, Swearincen, Joun J.: Protection of Passengers and
Air Crew from Air Blast Effects of Explosive De-
compression. Civil Aeronautics Medical Research
Laboratory, Aeronautical Center, Oklahoma City,
Oklahoma, Project No, 50-516, Report No. 1, August
1950.

3, SWEARINGEN, JoHN J, and McFavpen, E. B,: Studies
of Air Loads on Man, Civil Aeromedical Research
Institute, Aeronautical Center, Oklahoma City, Okla-
homa. Report No, 63-9, May 1963.

4, SWEARINGEN, JoHN J.: Tolerances of the Human Face
to Crash Impact. Civil Aeromedical Research Insti-
tute, Aeronautical Center, Oklahoma City, Oklahoma.
Report No. AM 65-20, July 1965.



CABIN VIEW EXTERNAL VIEW CABIN VIEW EXTERNAL VIEW

B

NUMBERS INDICATE SEQUENCE TIME IN SECONDS

Ficure 5. Representative sequence pictures of decompression ejections.

180-1b. dummy holding 13-Ib. infant near a 134 sq. in. window, 250 cu. ft. volume, 8.55 psi pressure differ-
ential, Infant ejected (.55 seconds).

180-lb. dummy holding 13-lb, infant and looking out of a 240 sq. in. window, 250 cu. ft. volume, 8.55 psi
pressure differential, Both ejected (.85 seconds).

8


8,000 —> 24,000 ft 8,000 —» 43,000 ft
5.20 p.si. Cabin Pressure Differential 8.55 p.s.i. Cabin Pressure Differential

CABIN VOLUME (ft)? CABIN VOLUME (ft)?
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DECOMPRESSION DANGER AREAS FOR CHILDREN
IN LIGHT AIRCRAFT

Froure 2, Safe and danger areas for infants, children, and adults in decompressions of small volume aircraft.

5



UNSAFE UNSA

AREA OF WINDOW (in)*

8,000 —= 24,000 ft 8,000 —> 43,000 ft
5.20 ps.i Cabin Pressure Differential 8.55 p.s.i. Cabin Pressure Differential

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DECOMPRESSION DANGER AREAS FOR ADULTS
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Ficure 1. Safe and danger areas for a 180-10. adult in decompressions of small volume aircraft.

4


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AM 67-14

AN EVALUATION OF POTENTIAL DECOMPRESSION
HAZARDS IN SMALL PRESSURIZED AIRCRAFT

John J. Swearingen, M.S.

Approved by Released by
= oe
le [USdgel 10
J. Roserr Diute, M.D. P. V. Srzcer, M.D.
Cmer, Civ, ArROMEDICAL Feperat Arr Surcron
Instirvts -

June 1967

FEDERAL AVIATION ADMINISTRATION
Office of Aviation Medicine



CABIN VIEW EXTERNAL VIEW

CABIN VIEW EXTERNAL VIEW

‘
2 be

NUMBERS INDICATE SEQUENCE TIME

IN SECONDS

Ficure 7. Representative sequence pictures of decompression ejections.

47-1b. 6-year-old child sitting 6 inches from a 274 sq. in. window, 500 cu. ft. volume, 8.55 psi pressure
differential. Child ejected (.40 seconds).

180-Ib. adult sitting 9 inches from a 500 sq. in. window, 700 cu. ft. volume, 8.55 psi pressure differential.
Dummy ejected (.94 seconds).

10


CABIN VIEW EXTERNAL VIEW CABIN VIEW EXTERNAL VIEW

NUMBERS INDICATE SEQUENCE TIME IN SECONDS

Fieure 6. Representative sequence pictures of decompression ejections.

81-lb. 38-year-old child sitting near a 132 sq. in. window, 190 cu. ft. volume, 8.55 psi pressure differential.
Child ejected (.35 seconds).

18-Ib, infant sitting 5 inches from a 274 sq. in. window, 190 cu. ft. volume, 8.55 psi pressure differential.
Infant ejected (.15 seconds).



900 aaa

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IN| SECONDS

Ficure 8, Experimental decompression times for 4 volumes of light aircraft with various window sizes (8,000 ft.

to 23,500 ft., 263mm Hg differential pressure).

6


ejection and head impact injuries. Four anthro-
pomorphic dummies (a 18-pound infant, a 31-
pound 38-year-old child, a 47-pound 6-year-old
child, and a 180-pound adult) were placed various
distances from each size window under different
test conditions and relative danger determined
from accelerometer readings and study of the
motion pictures. Cabin volumes were varied
from 100 to 700 cu. ft. to cover the range of the
present fleet of small pressurized aircraft. Air-
craft with volumes larger than 700 cu. ft. are
probably regulated by Federal Aviation Regula-
tions, Part 25, and required to have double-pane
windows. Window areas tested ranged from
100 to 900 sq. in. The largest windows in present
use have areas of 350 to 500 sq. in. However,
most windows in present use have areas of 250
sq. in. or less, but larger areas were evaluated
to determine effects of exit, door, and windshield
failures.

Because of the great number of tests required
to evaluate all variables in combination, only
two pressure differentials were evaluated: 5.2 psi
(270mm Hg) simulating aircraft flying at 24,000
ft. with cabins pressurized to 8,000 ft., and 8.55
psi (442mm Hg) simulating flight altitudes of
43,000 ft. with cabins pressurized to 8,000 ft.
Some small jets are presently certified to fly at
45,000 ft.

In addition, flow tests were conducted for all
test conditions to determine decompression times
without the dummies in place to serve as a basis
for determining time available for donning pro-
tective oxygen equipment and possible harmful
effects of R.G.E. (Relative Gas Expansion).

HI. Results.

As might be expected, small light-weight indi-
viduals were affected more by a given wind blast
situation than heavy adults. Figures 1 and 2
summarize the results of all decompression tests
in terms of safe and unsafe distances from the
“window.” The test condition was considered
unsafe if the vectored force of head impact read
from the triaxial accelerometers exceeded 80g*
and/or the dummy was completely ejected from
the aircraft. Danger areas are shown to the
left of each of the family of volume curves for
two pressure differentials with area of the open-
ing plotted on the ordinate and distance from
the opening on the abscissa. Danger areas for

the 180-pound dummy only are plotted in Figure
1 while Figure 2 shows the additional distances
necessary to protect infants and small children.
From Figure 1 it may be determined that adults
would not expect to receive fatal injuries sitting
next to a “window” during decompression if the
volume of the aircraft is not in excess of 350
cu. ft. and the pressure differential is less than
5.2 psi. Also, the same protection may be af-
forded for up to 5.2 psi differential pressure in
500 cu. ft. and 700 cu. ft. aircraft by designing
opening sizes with areas less than 500 sq. in. and
250 sq. in. respectively.

As previously stated, most present window
opening areas are below 250 sq. in. and the larger
openings are most applicable to emergency exits,
doors, and windshields. Referring again to
Figure 1, safe distances for adults in a 700 cu. ft.
aircraft flying with 5.2 psi cabin pressure dif-
ferential are 5 inches for a 500 sq. in. opening
and 8 inches for a 900 sq. in. opening. Since it
is not a general practice to place seats within
these distances of doors and windshields, only
failure of emergency exits (area of approxi-
mately 500 sq. in.) would probably be hazardous
to large adults in small volume aircraft limited
to altitudes of 24,000 ft.

However, as the pressure differential is in-
creased to 8.5 psi, as shown on the right of Figure
1, adults will be in danger of fatal head impacts
and/or ejection even in very small aircraft (190
cu. ft.) with very small windows (100 sq. in.).
Figure 2 shows that infants and small children
will be ejected from and/or receive fatal head
injuries in any aircraft with a volume of 190
cu. ft. or greater equipped with windows in ex-
cess of 100 sq. in. area and flying with cabin
pressure differentials of 5 psi or more. Also, as
might be expected, the critically safe distances
from the window increase as window area, vol-
ume, or pressure differential are increased. A
previous study? has shown that the proper use
of seat belts will prevent ejection from aircraft
but will not prevent head injury during a de-
compression,

Decompression or flow times are plotted for
all test conditions in Figures 3 and 4. According
to Luft and Bancroft? a pressure change of
slightly over 400mm Hg in 4/10 of a second or
less will produce possible lung rupture. This
danger area has been indicated on Figure 4 for
the test conditions studied. In addition, these


AN EVALUATION OF POTENTIAL DECOMPRESSION HAZARDS
IN SMALL PRESSURIZED AIRCRAFT

I. Introduction.

Military records of World War II bomber
flights list numerous examples of ejection of crew
members from these large volume pressurized
aircraft caused by wind blast during decompres-
sion following a blister or window failure. Also,
a few ejections of passengers from early pres-
surized commercial aircraft before the advent of
double windows and plug-type exits have been
reported. AJl United States pressurized civil
transports and U.S. business jets now have double
(or multiple load element) windows and most
have plug-type doors. This type of construction
has been shown to be very reliable. Decompres-
sion tests were conducted in the late 1940’s** to
establish danger areas around various size win-
dows of large aircraft and to develop and prove
the safety values of the double-pane window.
On the other hand, fighter pilots in very small
aircraft have lost their entire canopy without
being ejected. These experiences would lead one
to theorize that there is a break-over point some-
where on the safety curve as the volume of the
aircraft is decreased. The number of small busi-
ness type pressurized aircraft with volumes
ranging from about 150 to 900 cubic feet (some
with single-pane windows) is rapidly increasing
in the United States. The Flight Standards
Service Washington Office requested a study be
made to answer the question, “Would wind blast
effects be sufficient to eject passengers or cause
serious injury following a window failure in
these small volume aircraft ?”

The injurious effects of decompression wind
blast depend on a number of variables: (1)
cabin volume, (2) area of the opening, (3) cabin
pressure differential, (4) the distance a passenger
js sitting from the opening, (5) weight and body
size of the passenger, and (6) type of clothing
being worn.

The study was conducted to attempt to an-
swer the above question and to provide design

engineers with information. which will aid them
in designing safe configurations.

II. Procedure and Discussion.

Decompression tests were conducted in a low
pressure chamber equipped with the usual lock
and main chamber and an unusually large ac-
cumulator tank (15,000 cu. ft.) connected to the
main chamber by a 8-foot diameter tube. A
specially designed door was constructed to hold
a thin sheet of plastic representing the various
simulated window and other openings and se-
cured to the lock wall to separate the lock from
the main chamber and accumulator. Aircraft
cabin volumes and pressures were simulated in
the lock while the remaining portions of the sys-
tem were evacuated to simulate ambient external
air pressures. This arrangement of a small lock
volume compared with a large accumulator
volume (ratio=approximately 1/100 for the
small aircraft) allowed decompression testing
with very little drop in cabin flight altitude,
simulating closely actual flight conditions. Ac-
cumulator volumes (16,700 cu. ft.) were held
constant for all tests while variations in cabin
volumes (190 to 700 cu. ft.) were made by add-
ing fill materials to reduce the volume for simu-
lating smaller aircraft. Rupture of the simu-
lated window membrane was accomplished at
the desired time by a simple swinging knife re-
leased by an electromagnetic solenoid.

Instrumentation and recording equipment con-
sisted of triaxial Statham accelerometers mounted
in the dummy heads along with appropriate
amplifiers and recorders for recording head im-
pact. forces, motion picture coverage from both
sides of the window of wind blast effects on the
dummies during decompression, and closed cir-
cuit television monitoring of all tests.

In all, three hundred and thirty-eight tests
were conducted to determine danger areas around
windows of small volume aircraft in terms of



ACKNOWLEDGEMENTS

The author acknowledges the diligent assistance of Mr. Gary E. Wullen-
waber, FAA Flight Standards, and the staff of the Protection and Survival
Laboratory of the Civil Aeromedical Institute,

Qualified requestors may obtain Aviation Medical Reports from Defense Documentation
Center. The general public may purchase from Clearinghouse for Federal Scientific and
Technical Information, U.S, Dept. of Commerce, Springfield, Va, 22151