The F-16 Onboard Oxygen Generating System: Performance Evaluation and Man Rating

Abstract

An onboard oxygen generating system (OBOGS) has been developed by Clifton Precision, according to U.S. Air Force School of Aerospace Medicine (USAFSAM) specifications, for a flight test demonstration in the F-16A aircraft. Prior to actual flight test, the system was certified at the USAFSAM as described in this report. Laboratory testing consisted of manned and unmanned tests at ground level, at altitude, during rapid decompressions, and during acceleration loading. System hardware consisted of a molecular sieve concentrator, breathing-gas regulator, selector valve, product gas composition controller, backup oxygen supply (BOS), and a breathing mask. These components replace current liquid oxygen (lox) components and eliminate the need to service lox converters, resulting in faster aircraft turnaround time, increased safety, and decreased cost. Laboratory test results indicated that the F-16A OBOGS was adequate for flight test and that the breathing-gas composition was physiologically capable of preventing hypoxia and reducing the occurrence of atelectasis. Furthermore, the OBOGS provided considerably less breathing resistance than current lox systems. The concentrator and BOS provided the ability and redundancy to protect the pilot throughout the operational envelope of the F-16A. (Author)

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Report
USAFSAM-TR-
83-27
THE
F-16
ONBOARD
OXYGEN
GENERATING
,
YSTEM:
PERFORMANCE
EVALUATION
AND
MAN
RATING
Thomas
C.
Horch,
Captain,
USAF
Richard
L.
Miller,
Ph.D.
John
B.
Bomar,
Jr.,
Ueutenant
Colonel,
USAF,
BSC
John
B.
Tedor,
Major,
USAF,
BSC
Ronald
0.
Holden,
B.A.
Kenneth
G.
Ikels,
Ph.D.
Paul
A.
Lozano,
B.A.
August
1983
Final
Report
for
Period
1
March
1982
-
31
December
1982
Distribution
limited
to
U.S.
Government
agencies
only;
test
and
evaluation;
27
June
1983.
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requests
for
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referred
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AMD/RDO.
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J
.".C
&%LECTE
SEP
3
0
1983
3
USAF
SCHOOL
OF
AEROSPACE
MEDICINE
Aerospace
Medical
Division
(AFSC)
Brooks
Air
Force
Base,
Texas
78235
8
.
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THOMAS
C.
HORCHl,
Captain#
USAF
1ICR7.
M`ILLER,
Ph.D.-
Project
Engineer
Supervi
sor
ROYCE
MOSER,
Jr.
Colonel,,
USAF,
MC
Commander

___.__
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NUMBER
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ACQESSION
0-ECIPIENT'S
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NUMBER
USAFSAM-TR-83-27
A_
4.
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(and Subtitle)
5.
TYPE
OF REPORT
&
PERIOD
COVERED
Final
Report
THE
F-16
ONBOARD OXYGEN
GENERATING
SYSTEM:
I
Mar
1982
-
31 Dec
1982
PERFORMANCE
EVALUATION
AND
MAN
RATING
6.
PERFORMING
ORG.
REPORT
NUMBER-
7.
AUTIOR(#)
T. C.
Horch,
Capt,
USAF;
R. L.
Miller,
8.
CONTRACT
OR
GRANT NUMBER(i)
Ph.D.;
J.
B.
Bomar,
Jr.,
Lt
Col,
IJSAF, BSC;
J.
B.
Tedor,
Maj,
USAF,
BSC;
R. D.
Holden,
B.A.;
K. G.
Ikels.
Ph.D.;
P_
A-
Lnzann.
R.A
9.
PERFORMING
ORGANIZATION
NAME AND
ADDRESS
10.
PROGRAM
ELEMEi4T.
PROJECT,
TASK
AREA
&
WORK
UNIT
NUMBERS
USAF
School
of
Aerospace
Medicine
(VNL)
Aerospace
Medical
Division
(AFSC)
63246F
Brooks
Air
Force
Base,
Texas
78235
27610003.
I1.
CONTROLLING
OFFICE
NAME
AND
ADDRESS
12.
REPORT
DATE
USAF
School
of
Aerospace
Medicine
(VNL)
August
1983
Aerospace
Medical
Division
3AFSC)
13.
NUMBER
OF
PAGES
Brooks
Air
Force
Base,
Texas
78235
58
14,
MONITORING
AGENCY
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&
ADDRESS(if
different
from
Controlling
Office)
15.
SECURITY
CLASS.
(of
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report)
SP
Unclassified
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FICATION/_DOWNGRADING
SCHEDULE
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(of
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Report)
Distribution
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test
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1983.
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17.
DISTRIBUTION
STATEMENT
(of
the
absfract
entered
in
Block
20,
if
different
from
Report)
IS.
SUPPLEMENTARY
NOTES
IS.
KEY
WORDS
(Continue
on
reverse
side
it
necessary
and
Identify
by
block
number)
Onboard
oxygen
generator
Hypoxia
Molecular
sieve
Oxygen
composition
controller
Liquid
oxygen
system
Breathing-gas
regulator
Man
rating
0.
ABSTRACT
(Continue
on
reverse
side
If
necessary
and
identify
by
block
number)
;n
onboard
oxygen
generating
system
(OBOGS)
has
been
developed
by
Clifton
Preci-
sion,
according
to
U.S.
Air
Force
School
of
Aerospace
Medicine
(USAFSAM)
specifi-
cations,
for
a
flight
test
demonstration
in
the
F-16A
aircraft.
Prior
to
actual
flight
test,
the
system
was
cýrtlfied
at
the
USAFSAM
as
described
in
this
report.
Laboratory
testing
consisted
of
manned
and
unmanned
tests
at
ground
level,
at
altitude,
during
rapid
decompressions,
and
during
acceleration
loading. System
hardware
consisted
of
a
molecular
sieve
concentrator,
breathing-gas
regulator,,.
DD
I
1473
EDITION
OF
I
NOV
65
IS
OBSOLETE
UNCLASSIFIE/
/
SECURITY
CLASSIFICATION
OF
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PAGE
(When
Date
Entered)
*. '
2§
A
.I

S
I
UNCLASSIFIED
1SECURITY
CLASSIFICATION
OF
THIS
PAGE(Whmn
Data
Entered)
20.
ABSTRACT
(Continued)
-seledtor
valve,
product
gas
composition
controller,
backup
oxygen
supply
(BOS),
and
a
breathinq
mask.
These
components
replace
current
liquid
oxygen
(lox)
com-
ponents
and
eliminate
the
need
to
service
lox
converters,
resulting
in
faster
aircraft
turnaround
time,
increased
safety,
and
decreased
cost,
Laboratory
test
results
indicated
that
the
F-16A
OBOGS
was
adequate
for
flight
test
and
that
the
breathing-gas
composition
was
physiologically
capable
of
preventing
hypoxia
and
"reducing
the
occurrence
of
atelectasis.
Furthermore,
the
OBOGS
provided
consid-
erably
less
breathing
resistance
than
current
lox
systems.
The
concentrator
and
BOS
provided
the
ability
and
redundancy
to
protect
the
pilot
throughout
the
operational
envelope
of
the
F-16A.
' -1
Accessi
on
For
"DTIC
TAB
Unannour~ad
i,•_
JUSt
if i
cat
ion__•
,-',
iDist
r'ibut
ion/
Availability
Codes
Avail
and/or'
Dist
Speciald/r
UNCLASSIFIED
SECURI
TY CLA
SSIFICATION
OF
THIS
PAGE
(M~ien
Data
Entered)

C
ON
T
ENTS
INTRODUCTION..
. . .
..................................................
............... .............
3
SYSTEM
DESCRIPTION........
............
.................... ...
*
.*.... 3
Connector
and
Mask.,
.................................................
...... o ..*. . . . .. 7
Monior . .... ... o . ........ ... ...
o........
7
Selector Valve.
...........
.*... ** **..****.......... o.......*****, 7
Backup
Oxygen System
....*................... 8
PEFOMndcEtr...
EAUTO...
.........
.... .......
........
.o ...... ... ...
0....
9
PEFRAC EVLAIN... .....
o..........
o..........
28
Ronentrator
..............
o...... .
o.o............o................
29
Selector.
...
eBO........
o ..
oo.........
o.......
........ .*...**.****..**..
44
Rapid
Decompression Testing
......
... *.*..*.*
...................
45
Acceleration
Testing.
..........
.. **.**.........
........
.. .. 45
Rapid
Decompression
Testing.
.................
..........
o........
..
47
Acce era ion ... ...
....
oo....
..
o..58
REOMEDTIN ......... 5
Co
c
nt
a o .. . ..... . . .................... 5
Re
u a o .. . . . ........... .. . . . ........... 5
Con rol er... .. ...
.. ... ..
... .. ... ..
... .. ...
.. ... .. ...
1

THE
F-16
ONBOARD
OXYGEN
GENERATING
SYSTEM:
PERFORMANCE
EVALUATION
AND
MAN
RATING
INTRODUCTION
The
U.S.
Air
Force
School
of
Aerospace
Medicine
(USAFSAM)
is
developing
equipment
to
replace
aircraft
liquid
oxygen
(lox)
breathing
systems
with
an
onboard
oxygen
generating
system
(OBOGS).
Prototype
OBOG
systems
have
been
designed
and
built
in
previous
research
and
development
efforts.
Now
USAFSAM
is
developing
a
preproduction
OBOGS,
including
hardware
development,
laboratory
testing,
and
flight
testing
in
an
F-16A
aircraft.
Clifton
Preci-
sion Instruments
and
Life
Support
Division,
of
LUtton
Industries,
has
developed
OBOGS
hardware
according
to
USAFSAM
specifications.
USAFSAM
conductci
laboratory
testing
before
completion
of
F-16
aircraft
modification
at
General
Dynamics
and
the
subsequent
flight
test
at
Hill
Air
Force
Base,
Utah.
This
report describes
the
F-16A
OBOGS
equipment,
laboratory
test
procedures,
and
data
and
results
obtained
during
the
OBOGS
performance
evaluation
at
USAFSAM.
Laboratory
testing
consisted
of
a
simulated-flight-
envelope
evaluation
of
all
OBOG
subsystems
to
determine
equipment
limita-
tions.
This
was
followed
by
man
rating
to
determine
the
equipment's
ability
to
sustain
human
physiological
requirements.
SYSTEM
DESCRIPTION
Components
of
the
F-16A
OBOGS
include
a
concentrator,
regulator,
oxygen
mask
and
connector,
monitor,
controller,
selector
valve,
backup
oxygen
supply
(BOS),
and
indicators
(Fig.
1).
The
system
was
designed
to
provide
a
physiologically
acceptable breathing
gas
for
all
flight
modes
of
the
F-16A
aircraft
(representative
of
current
USAF
high-performance
tactical
weapon
systems).
The
OBOGS
is
the
primary
breathing-gas
source
for
the
test
air-
craft
up
to
25,000-ft
cabin
altitude.
If
cabin
depressurization
should
occur
above
25,000
feet,
the
OBOGS
will
automatically
deliver
gaseous
avia-
tors'
breathing
oxygen--MIL-O-27210D,
type
1
(99.5%
purity)--to
the
pilot
via
the
backup
supply.
Descriptions
of
the
individual
components
follow.
Concentrator
A
molecular
sieve
concentrator
is
used
to
produce
an
oxygen-enrlched
breathing
gas.
The
concentrator
is
supplied
with engine bleed
air
from
the
aircraft
environmental
control
system
(ECS).
The
concentrator
(Fig.
2)
con-
tains
an
internal
nressure
regulator
which
reduces
concentrator
inlet
pres-
sure to
37.5
±
5
psig.
Engine
bleed
air
is
cycled
alternately
through
a
pair
of
molecular
sieve
beds
to
produce
an
oxygen-enriched
breathing
gas
having
a
maximum
oxygen
concentration
of
95%,
with
5%
argon.
The
oxygen
concentration
depends
upon
inlet
air
temperature
and
pressure,
exhaust pres-
sure
(altitude),
and
the
rate
of
product
flow
demanded
from
the
concentra-
tor.
Product
gas
is
supplied
to
the
monitor,
controller,
shuttle
valve,
A 3
• "I

...
4
OVERBOARD
EXHAUST
DUMP
H
CONNECTOR
MASK
p
4
I.-
Figure
1.
F-16A
OBOGS
functional
diagram.
K
'9.
4
..-.
>.

T~
-,- -- -.-
U------
74
~
----
Figure
2..
F-16
OuuuS
concentrator.
i~5

breathing
regulator,
and
mask.
A
fiberglass
shroud
encloses
tV
concentra-
tor
to
reduce
heat
gain
or
loss
(Fig.
3).
NN
' t4'
Figure
3.
F-16
OBOGS
concentrator
with
shroud.
Regulator
The
pilot's
breathing-gas
regulator
reduces
inlet
gas
supply
pressure
to
a
level
suitable
for
human
respiration.
The
regulator
inlet
pressure
is
approximately
38
psig
when
the
regulator
is
supplied
from
the
concentrator,
and
approximately
60
psig
when
supplied
from
the
BOS.
(BOS
pressure
is
reduced
from
a
nominal
1800
psig
to
60
psig
in
the
selector
val
le.)
The
regulator
provides
a
positive
static
safety
pressure
of
approximately
1
inch-water-gauge
(in-wg)
at
all
cabin
altitudes
up
to
38,000
feet.
At
38,000-ft
cabin
altitude,
a
pressure breathing
feature
delivers
an
increased
positive
pressure
schedule
to
the
mask.
The
regulator is
a
100%
pressure
demand
regulator
and
does
not
dilute
the breathing
gas
with
cabin
air.
A
press-to-test
button
on
the
regulator
provides
17-in-wg
pressure
to
the
mask-to-test
mask
fit.
6

Connector
and
Mask
The
OBOGS
includes
a
standard
USAF
CRU-60/P
connector
as
well
as
stan-
dard
oxygen
hoses.
A
modified
United
Kingdom
type
P/Q
aviation
oxygen
mask
and
the
USAF
MBU-5/P
or
12/P
masks
will
be
used
in
the
flight
test
demon-
stration.
The
P/Q
mask
is
preferred
by
USAFSAM
because
of
its
reduced
breathing
resistance
when
compared
to
the
standard
MBU
5/P
or
12/P
mask.
Resistance
to
breathing
is
less
in
the
P/Q
mask
because
it
has
separate
inspiratory
and
expiratory
valves
versus
a
combined
valve
in
the
MBU
masks.
For
this
flight
demonstration,
the
P/Q
mask
was
modified
to
be
com-
patible
with
USAF
communication
systems
and
to
allow
the
mask
to
be
attached
to
the
standard
USAF
HGU-26/P
helmet
with
bayonet
receivers.
Monitor
The
OBOGS
incorporates
a
polarographic-type
oxygen
monitor
to
measure
the
partial
pressure
of
oxygen
(P02)
produced
by
the
concentrator.
This
monitor
provides
a
low-oxygen
warning
to
th.
pilot
and
automatically
acti-
vates the
BOS
if
the
concentrator
is
producing
an
insufficient
oxygen
par-
tial
pressure.
The
monitor's
output
is
an
adjustable
electrical
signal
which
is
linearly
proportional
to
P02.
This
signal
is
compared
with
an
internally
generated
reference
voltage.
When
the
monitor
output
falls
below
the reference voltage,
a
binary
signal
is
generated
which
activates
the
BOS
and
illuminates
an
OXY
LOW
caution
light.
The
reference
voltage
and
monitor
gain
are
adjusted
to
activate
the
BOS
and
to
illuminate
the
indicator
lights
whenever
the
concentrator
product
gas
P0
2
falls
below
195
mmHg.
A
system
press-to-test
button
on
the
regulator
activates
a
test
of
the
monitor
and
automatic
switchover
to
BOS.
When
the
test
is
activated,
ambient
cabin
air
is
delivered
to
the
monitor
and
produces
a
low P0
2
condition.
When
the
K.
press-to-test
is
released,
OBOGS
product
gas
is
delivered to
the
monitor
and
bleeds
overboard
through
the
monitor
case.
Controller
The
OBOGS
incorporates
a
controller
to
adjust
the
product
gas
composi-
tion.
Product
gas
oxygen
concentration
should
be
no
greater
than
70%
from
ground
level
to
17,000-ft
cabin
altitude.
The
product
gas
composition
is
controlled
by
bleeding
a
prescheduled
amount
of
product
gas
into
the
cabin.
The
amount
of
gas
(product
bleed
flow)
bled
into
the
cabin
is
a
function
of
cabin
altitude
and
is
also
affected
by
the
amount
of
product
gas
delivered
to
the
crewmember.
The
controller
is
strictly
a
pneumatic
device
and
does
not
incorporate
feedback
from
the
oxygen
monitor.
Selector
Valve
The
OBOGS
selector
valve
is
used
to
manually
and/or
automatically
select
the
breathing-gas
source
from
either
the
OBOGS
concentrator
or
the
BOS.
The
selector
valve
has
four
positions:
OFF,
OBOG,
NORMAL
AUTO,
and
BACKUP
OXY.
In
this
report
these
will
be
referred
to
as
OFF,
OBOG,
AUTO,
and
BU
respectively.
The
crewmember
can
at
any
time
manually
select
backup
oxygen
by
placing
the
selector
valve
at
BU.
With
the
valve
in
this
7

position,
stored
oxygen from
the
backup
supply
will
be
delivered
through
the
shuttle
valve
and
regulator
to
the
mask.
With
the
selector
valve
at
OFF,
the
BOS
bottles
are
mechanically
locked
out
and
cannot
supply
the
regula-
tor.
The
OFF
position
allows
the
system
test
to
be
completed
without
depleting
the
BOS
and
also
inactivates
the
BOS
when
the
concentrator
or
air-
craft
engine
is
not
operating.
With
the
selector
valve
at
AUTO,
the
system
will
automatically
switch
to
BOS
if
the
OBOGS
product-gas
oxygen
partial
pressure
falls
below
195
mmHg
or
if
cabin
altitude
exceeds
25,000
feet.
With
the
selector
valve
at
OBOG,
below
31,000-ft
cabin
altitude
the
pilot
can
manually
reselect
OBOGS
product
gas.
Above
31,000
feet,
the
system
automatically
reselects
the
BOS.
With
the
selector
valve
set
at
either
OBOG
or
AUTO,-
the
system
will
select
BOS
whenever
regulator
inlet
pressure
is
less
than
10
psig.
When
the
BOS
is
supplying
the
regulator,
the
shuttle
valve
will pneumatically
switch
back
to
OBOG
product
gas
when
the
BOS
bottles
are
depleted.
Backup
Oxygen
System
The
backup oxygen
system
consists
of
two
50-in
3
high-pressure
(2000
psig)
gaseous
oxygen
cylinders
having
a
combined
capacity
of
200
liters
NTP
(normal
temperature
and
pressure).
The
two
bottles
are
connected in
paral-
lel
with
the
necessary
fittings
to
allow
ground
filling.
A
high-pressure
hose
connects
the
BOS
bottles
to
the
selector
valve
which
reduces
the
pres-
sure
to
60
psig
and
delivers
backup
oxygen
to
the
regulator
when
selected.
Indicators
An
oxygen
pressure
gauge
(bailout-bottle
type)
indicates
the
pressure
remaining
in
the
BOS,
and a
yellow
caution
light
mounted
on
the
selector
valve
indicates
when
the
selector
valve
is
in
the
BU
position.
This
light
also
illuminates
if
the
cabin
altitude
is
above
31,000
feet (at
this
alti-
tude
the
system
automatically
selects
BOS)
or
if
the
selector
valve
is
in
the
AUTO
position
and
a
system
malfunction
causes
automatic switchover
to
the
BOS.
An
OXY
LOW
caution
light
illuminates
whenever
the
oxygen
monitor
detects
less
than
195-mmHg
P0
2
or
whenever
OBOGS
product
pressure
falls
below
10
psig.
Illumination
of
the
OXY
LOW
light
also
causes
the
resettable
aircraft
master
caution
light
to
illuminate.
The
system
press-to-test
button
causes
both
the
OXY
LOW
and
selector
valve
lights
to
illuminate.
A
cockpit-mounted
power
switch
controls
electrical
power
to
the
concentrator
and
activates
the
rotating
inlet
valve.
8

PERFORMANCE EVALUATION
The
OBOGS
was
evaluated
to
determine
system
characteristics
and
oper-
ating
limitations.
Concentrator
inlet
pressure
and
temperature,
exhaust
pressure
(altitude),
and
product
flow
were
varied
while
product
gas
composi-
tion
and
pressure
were
measured.
Rapid
decompression
and
acceleration
test-
ing
were
also
accomplished.
A
description
of
the
tests
and
test
results
follow.
Concentrator
The
OBOGS
concentrator
was
tested
as
a
separate
component
to
ascertain
its
performance characteristics.
A
pressurized
air
supply
was
plumbed
through
a
circulation
heater
to
the
concentrator
inlet
port. The
concentra-
tor
was
located inside
an
"aircraft-altitude"
chamber
and
was
instrumented
to
monitor/record
inlet
air
temperature,
pressure,
and
flow;
exhaust
temper-
r
ature;
electrical
motor
current;
and
temperature
inside
the
concentrator's
shroud.
The
concentrator
exhaust
gas
was vented
to
this
chamber
while
produ!ct
gas was
plumbed
through
actual
F-16
oxygen system tubing
to
an
adjoining
"cabin-altitude"
chamber.
A
digital
controller
was
used
to
control
the
two
altitude
chambers
so
that
the
concentrator
would
be
main-
tained
at
aircraft altitude
with
the
product
gas
vented
to
cabin
altitude.
The
altitude
chambers
were
controlled
to
mimic
the
aircraft
pressurization
L
schedule.
A
metering
valve
at
the
end
of the
concentrator
product
gas line
controlled
output
flow,
and
instrumentation
recorded product
gas
composi-
ton, flow,
and
temperature.
A
series
of
ground-level
tests
were
made
to
determine
product
gas
com-
position
as
a
function
of
concentrator
inlet
pressure
and
outlet
flow.
Figure
4
illustrates
the
relationship
between
concentrator
inlet
pressure
and
product
gas
composition
at
a
steady
product
flow
of
20
1/mmn
and
with
concentrator
inlet
air
at
ambient
temperature
(230,
or
73'F).
The
oxygen,
nitrogen,
and
argon
curves
tend
to
flatten
out
above
40-psig
inlet
pressure
II.due
to
the
concentrator's
internal
pressure
regulator.
Note
that oxygen
concentration
is
considerably
lower with
low inlet
pressures;
however,
this
should
not
present
a
problem
in
the
F-16
because minimum
inlet
pressure
is
expected
to
be
40 psig.
Figure
5,
except
for
product
flow
of
50
1/mmn,
is
similar
to
Figure
4.
Figure
6
displays
oxygen
concentration
as
a
function
of
concentrator
inlet
pressure
and
product
flow. This
curve
(ground
level)
was
obtained
with
ambient
inlet
temperature
and
shows
product
flow
curves
for 20,
50,
and
100
!,'min.
Higher
product
flows
decrease
the
oxygen concen-
tration
in
the
product
gas.
Figure
7 is a
plot
of
product
gas
composition
versus
product
gas
flow. This
data
was
obtained
at
ground
level
with
the
inlet
pressure
set
at
40
psig
and
with
inlet
air
at
ambient
temperature.
At
this
time
it is
advantageous
to
explain
some
terminology
that
will
be
used
throughout
the
remainder
of
this report.
Concentrator
inlet
pres-
sure
was
always
gauge
pressure referenced
to
aircraft
(concentrator)
alti-
tude.
,
Thus,
at
ground
l
evel
,
40
ps
ig i
nl
et
pressure
was
40+14.4,
or
54.4
psia
(absolute);
and
at
10,000-ft
aircraft
altitude,
40
psig
inlet
pressure
was
4U+10.1,
or 51.1 psia;
and
product
flows
were
ATPD (ambient
temperature,
pressure, dry) liters
per
minute.
Therefore,
a
product
flow
of
50
1/min
at
10,000
feet
was
equivalent
to
a
ground-level
flow
of
5OX
(10.1/14.4),
or
35.1
1/mmn.
9

100
80
L
*J
ILI
0 6
cc
z
40
z
KZ Ca
20
0
20
40
s0
80
100
CONCENTRRTOR
INLET
PRESSURE
(PSIGS
Figure
4.
OBOGS
concentrator
only:
product
gas
composition
vs
concentrator
inlet
pressure,
at
ground
level,
with
20-1/min
product
flow
and
23
0C
inlet
temperature.
(0
=
oxygen,
N
=
nitrogen,
A
=
argon)
10

100
80
i soo
I
z60
ILi
z
"W 40
2
0I,,,,,
20
00 S
,-,0 20
40
60
80
1.00
CONCENTRATOR
INLET
PRESSURE
(PB1GsL
Figure
5.
OBOGS
concentrator
only:
product
gas
composition
vs
concentrator
inlet
pressure,
at
ground
level,
with
50-1/min
product
flow
and
23'C
inlet
temperature.
(0
oxygen,
N
nitrogen,
A
=
argon)
-t 11

"+I'
too
•
~90
'
80,,
5-
o s
I /
I
U 70
C.)
z
C.
prd50lw
o 0 0
ndI0Iri.
3•23
5,I=I0-
40
30
a 040
60
so
100
CONCENTRATOR
INLET
PRESSURE
(PSTGJ
Figure
6.
OBOGS
concentrator
only:
oxygen
concentration
vs
concentrator
inlet
pressure,
at
ground
level,
with
23*C
inlet
temperature
and
product
flows of
20, 50,
and
100
I/min.
(2
20,
5
SO,
1
100
I/mi
n)
12

400
:4
a
260
wOf
40
2.
20.
0
20 40
60 80
1O00:
PROOUCT
FLOW
(LITERS/MIN)
Figure'7.
OBOGS
concentrator
only: product
gas
composition
vs
product
flow
at
ground.
level,
with
23
0C
inlet
temperature
and
40-psig
inlet
pressure.
(0
oxygen,
N =
nitrogen,
A
argon)
13

71
o- ,
Oxygen
concentration
increased
with
increasing
altitude,
as
shown
in
Figure
8,
for
the
higher
product
flow
of
50
1/min
ATPD.
This
data
was
obtained
with
a
constant
inlet
pressure
of
40
psig
and
with
inlet
air
at
ambient
temperature.
As
aircraft
altitude
increased,
cabin
altitude
increased
according
to
the
F-16
aircraft
pressurization
schedule:
normo-
baric
altitudes
are
maintained
to
8,000
feet;
the
cabin
maintains
an
isobaric
altitude
of
8,000
feet
while
the
aircraft
climbs
to
23,000
feet;
and
above
23,000
feet
the
cabin
maintains
a
5
psi
differential
above
ambient
pressure
Except
for
simulating
an
unpressurized
cabin
(equal
aircraft
and
cabin
altitudes),
Figure
9 is
similar
to
Figure
8.
The
remaining
variable
that
affected
product composition
was
heat.
The.
primary
source
of
heat
in
the
F-16
is
heat
of
compression
in
the
engine
bleed
air.
Engine
bleed
air
in
the
F-16
is
conditioned
by
the
aircraft
environmental
control
system;
however,
concentrator
inlet air
temperature
remains
elevated
above
ambient
outside-air
temperature.
Aircraft
installa-
tion
was
simulated
in
the
laboratory
by
heating
the
inlet
air
temperature
and
allowing
the
concentrator
to
reach
equilibrium,
as
determined
by
moni-
toring
exhaust
temperature
and
temperature
inside
the
concentrator
shroud.
The
ground-level
effect
of
temperature
on
product
composition
is
shown
in
Figure
10.
This
data
was
obtained
with
concentrator
inlet
pressure
of
40
psig
and
indicates
that
oxygen
concentration
was
lower
at
80°C
(176
0F)
than
at
23*C
ambient
inlet
air
temperature.
Figure
11
shows
the
ground-level
relationship
between
oxygen
concentration
and
concentrator
inlet
pressure
with
80*C
inlet
air.
The
oxygen
concentration
at
altitude
is
shown
in
Figure
12
for
three
product
flows--20,
50,
and
100
I/min;
inlet
temperature
was
80'C
and
concen-
"trator
inlet
pressure,
40
psig.
Figure
13
compares
oxygen
concentration
at
altitude
for
20
and
80
0C
inlet
air
with
a
steady
product
flow
of
50
]/min.
After
concentrator
performance
was
determined,
the
cockpit-mounted
com-
ponents
were added
to obtain
system
performance.
14
'1**
-
2
2.'. .
2
..•.. ..

ito
95
,1
90
:2~
RIRC~RfFT
RLTITUDE
(THOUSAND
FEET)
:
*
FigureS8.
OBOGS
concentrator
only:
oxygen
concentration
vs
pressurized
-.
i
aircraft
altitude,
with
23
0C
inlet
temperature, 40-psig
inlet
-,
pressure,
and
product
flows
of
20
and
50
1/mai.
(2
=
20,
5
=
..
501/mmn)
Z
71
.z. .. -...
W
' 7 ' ..
,".'
.• - . ,.:
•.•,:
,.
•
;
:. • • •
,•
•• •• • •. ......

100
95
90
z
85
V "• z
• oso
z
z
70
":"
85
"'". I , I
0
to
20
30 40
50
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)
Figure
9.
OBOGS.concentrator
only:
oxygen
concentration
vs
unpressurized
aircraft
altitude,
with
23*C
inlet
temperature,
40-psig
inlet
".-'
pressure,
and
product
flows
of
20
and
50
I/min.
(2
=
20,
5 =
50
1/mln)
16
. . . . .

2a
100
90
80
ON
70
z
II
so
:
-60
50
40
30
0
20
40
60 80
100
K
PRODUCT
FLOW
(LITERS/HIN)
Fi
gure
10.
OBOGS
concentrator
only:
oxygen
concentration
vs
product
flow,
at
ground
level,
with
40-psig
inlet
pressure
and
23
and
80%C
inlet
temperatures.
( 2
=
23,
8
=
80*C)
17

-. .
* *(
60,
liti
so•
I A
"80
€l:1
z
go
70
h
20 40
so
so
Lao
l~i•,•
CONCENTRATOR
INLET
PRESSURE
(P$IG,
!i
Figure
11.
OBOGS
concentrator
only:
oxygen
concentration
vs
inlet
pressure,
.
Sat
ground
level,
with
80*C
inlet
temperature
and
product
flows
I!of
20
and
50
I/min
(2
=20,
5
=50
I/min)
118
k ,I!I.- -
p]

100
90
oe
0-z
I- 70
Z
Z
40
, , , , .. .
i_
0
10
20
30
40
so
so
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)1
Figure
12.
OBOGS
concentrator
only:
oxygen
concentration
vs
pressurized
aircraft
altitude,
with
800C
inlet
temperature, 40-psig
inlet
pressure,
and
product
flows
of
20,
50,
and
100
I/min.
2
=20,
5
=50,
1
=100)
z1

IIT,
100
90
I.o-
130
Zd
WW
Z
Li~
170
L60
50..
0
10
20
30
40
50
60s
RIRCRAFT
ALTITUDE
(THOUSAND
FEET)
"
Figure
13.
OBOGS
concentrator
only:
oxygen
concentration
vs
pressurized
aircraft
altitude,
with
40-psig
inlet
pressure,
50-1/min
product
flow,
and
inlet
temperatures
of
23
and
80
0C. (2
=
23,
8
=
80
0
C)
20
I• '
.
. .. . .

Controller
The
OBOGS
controller
adjusts
product
gas
composition
by
bleeding
product
gas
into
the
cabin
at
a
prescheduled
rate.
Therefore,
total
concen-
trator
product
flow
was
the
sum
of
pilot
inspiratory
flow
plus
controller
bleed
flow.
Figure
14
illustrates
the
desired
oxygen
concentration
band:
The
minimum
concentration
as
195
mmHg,
which
is
above
the
physiological
equivalent
to
breathing
air
at
sea
level,
and
the
maximum
concentration
was
intended
to
prevent
or
minimize
the
occurrence
of
acceleration-induced
atelectasis.
Figure
14
also
shows
the
concentration
that
would
be
delivered
to
the
pilot
with
minute
volume
flows
of
10
and
50
1/min
at
an
inlet
temper-
ature
(f 800C,
an
inlet
pressure
of
40
psig,
and
no
controller
bleed
flow.
100
71
100
0I /
--
80-
-00• ,J
70
R"
M
S~DESIRED
MAXIMUM
/
zg /
70
C I
I MWM~
040 .-
"CO
T
CONCENTRATION
20• I II I I l I
0
5
8
10
15
20
25
30
35
CABIN
ALTITUDE
(THOUSAND
FEET)
N
I
I
I I
0 5
82326.5
36.5
49
75
PRESSURIZED
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)
Figure
14.
Desired
concentration
range
and
OBOGS
uncontrolled
output
vs
altitude
with
product
flows
(Qp)
of
20
and
50
1/min.
21
p74

USAFSAM
personnel
had
the
opportunity
to
adjust
three
controllers
during
laboratory
testing.
For
reference
purposes,
one
will
be
called
the
USAFSAM
controller
(used
by
USAFSAM
for
system
testing);
one,
the
aircraft
controller;
and
the
third,
the
spare
aircraft
controller.
When
the
USAFSAM
controller
was
added,
bleed
flow
lowered
the
oxygen
concentration
as
shown
in
Figure
15.
Here
the
product
flows
were
10
and
50
1/min
(the
approximate
minimum
and
maximum
minute
volumes
expected in
flight),
the
concentrator
inlet
pressure
was
40
psig,
and
inlet
temperature
was
800C.
The
controller
was
set
to
bleed
approximately
33.5
1/min
at
ground
level.
As
altitude
increased,
bleed
flow
increased
to
approximately
70
1/min
at
12,000-ft
cabin
altitude,
then
began
to
decrease,
and
stopped
completely
at
22,000-ft
cabin
altitude.
100
USAFSAM
CONTROLLER
f --- -7
90
-
80
//
so
-z/
0
70
--- 0/
•.:.Z
0
5
810
15
000,3 3
60
-
8
2
S50
5
vs
altitude
for
product
flows
(Qp)
of
10
and
50
1/mi
with3
33.5-1/min
bleed
flow.
22
".•."'j•,•
.•
? ,I .,-- - - ,..
'..''V'
',*. .
*-."..-.-. . & . ' '.
.,, , ,"..?'• a••''- '',''•-';''''=-'''•' '' • .. ..

Ki
The
controller
had
a
provision
for
external
adjustment
of
the
bleed
flow
schedule.
Making
this
adjustment
simultaneously
affected
two
charac-
teristics
of
the
bleed
flow
schedule:
(1)
to increase
or
decrease
the
ground-level
bleed
flow
rate,
and
(2)
to
change
the
altitude
at
which
the
bleed
flow
began
to
decrease.
These
effects
are
illustrated
in
Figures
16
and
17.
Both
graphs
were
obtained
with
an
inlet
temperature
of
80°C
and
an
inlet
pressure
of
40
psig.
Figure
16
represents
a
product
flow
set
at
10
1/min;
and
Figure
17,
50
I/min.
The
traces
indicate
that
a
small
change
in
ground-level
settings
for
bleed
flow
created
a
more
noticeable
effect
in
oxygen
concentration
at
above
8,000-ft
cabin
altitude.
100
7
ioi /
Sz /
60
7o
50
/
60-40
L'
QB
=33.5
30
-
0
5 8 10
15
20
25 30
35
CABIN ALTITUDE
(THC
JSAND
FEET)
I I p I I
0
5
823
26.5
36.5
49
75
PRESSURIZED
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)
Figure
16.
OBOGS
output
with
"USAFSAM"
controller,
oxygen
concentration
vs
altitude,
with
10-1/min
product
flow
and
bleed
flows
(Qb)
of
32,
33,
and
33.5
I/min,
,,.23.

I
During
laboratory
testing,
the
controller
was
set
to
obtain
optimum
'j
performance;
i.e.,
bleed
flow
was
set
to
keep
the
oxygen
concentration
within
the
band
over
the
widest
range
in
altitude
and demand
flow.
Figure
17
indicates
that
with
a
product
flow
of
50
I/min,
a
bleed
flow
setting
of
34.0
l/
min
(ground
level)
caused
the
backup
to
activate
at
approximately
16,000
feet.
Figure
16
indicates
that
with
a
product
flow
of
10
1/min,
the
optimum
performance
was
obtained
with
the
bleed
flow
set
at
33.5
1/min
which
produced
results
as
shown
in
Figure
15.
100 - r
90I /
S780
/
040
70
-
0
5
810
15
20 25
30
35
I I I III:-
0
5
8
23
26.5
36.5
49
75-,
PRESSURIZED
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)-:"1
Figure
17.
OBOGS
output
with
"USAFSAM"
controller:
oxygen
concentration
vs'
altitude,
with
50-1./mmn
product
flow
and
bleed
flows
(Qb)
of
32,
,,
33,
33.5,
and
34
1/m.
224
Llq
C A
(
FEET)
0 5 823 26.5 36.5 49.7

The
USAFSAM
controller
was
set
as
shown
in
Figure
15;
the
aircraft
con-
troller,
as
in
Figure
18;
and
the
spare,
as
in
Figure
19.
The
same
proce-
dure
was
used
to
obtain
the
optimum
schedule
for
each
controller.
The
worst-case condition
was
40
psig
and
80%C;
this
was
the
minimum
pressure
and
maximum
temperature
expected in
the
F-16.
With
these
settings,
the
product
flow
was
set
for
50
1/min and
the
bleed
flow
was
adjusted
to
keep
the
P0
2
above
195
mmHg,
thus
keeping
the
BOS
off
during
normal
operations.
The
three
controllers
had
slightly
different
characteristic
curves
for
product
flows
of
10
and
50
1/min.
This
difference
is
believed
to
be
caused
by
slight
variations
in
the
springs
of
the
three
different
controller
diaphragms.
100
r
9
0
S80
.
zW7707
(L
60
60
'00
050
0
40
QP
60
0
5
8
10
15
20
25 30
35
CABIN
ALTITUDE
(THOUSAND
FEET)
!I I I I I
A
0
5
8
23
26.5
36.5
49
75
PRESSURIZED
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)
Figure
18.
OBOGS
output
with
"aircraft"
controller:
oxygen
concentration
vs
altitude,
wIth
27-1/min
bleed
flow
and
product
flows
(Qp)
of
5,
10,
50,
and
60
1/min.
25
..................

9o
I
I.,
100
-
90
/
8
j80
W/
70
I
20
10
.00
K0
5
8
10
15
20
25
30
35
CABIN ALTITUDE
(THOUSAND FEET)
I I I I I I
K0
5
8
23
26.5
36.5
49
75
PRESSURIZED
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)
Figre
9.
BOG
ouputwith
"spare
aircraft"
controller:
oxygen-
concentration
vs
altitude,
with
27-1/min bleed
flow
and
•
product
flows
(Qp)
of
10
and
50
1/min.
626
I,
Vz
Wq
*.~~~~~~4Q
*. -..
-
,-.
.
.!
20
0 5 10 5 2 25 0 3
•!•:.;:.:.•.•:`.?•`:.:;:.•;;:;::•:.:;.::.?:•÷;.`CAB..:;..IN
ALTITUDE
(THOUSAND
FEET):•:.•;c•.•..•.:/
.`•,:/...•°
:•`•`::•.`•`..:.••....:.

At
the
time
the
controllers
were
set,
the
inlet
air
temperature
to
the
OBOGS
on
the
aircraft
was
not
well
defined.
It
was
believed
that
the
maxi-
mum
temperature
would
not
exceed
80'C;
however,
normal
operating
tempera-
tures
would
likely
be
less
than
80
0C.
Figures
20
and
21
show
the
effect
that
inlet
air
temperature
had
on
oxygen
concentration
for
steady
product-
gas
flows
of
10
and
50
1/min,
respectively,
using
the
USAFSAM
controller.
Figure
21
indicates
that
the
BOS
would
be
activated
if
inlet
temperature
was
elevated
above
90°C
with
50
I/min product
flow.
However,
the
flight
test
program
was
not
expected
to
encounter
50
1/min
sustained
product
flows
or
high
inlet-air
temperatures
at
the
high
altitudes
where
the
P0
2
could
fall
below
195
mmHg.
1oo
-/
100[
1 1 52
904
s
80-oC
oC
.
S70
------o,¢
60
I
Tin
=00
S50
•
3
0
s • "
20
1
0
5
8
10
15
20
25 30
35
CABIN ALTITUDE
(THOUSAND
FEET)
I
I I I I
.I
A823
26.5 36.5
49
75
PRESSURIZED
AIRCRAFT
AL(ITUDE
(THOUSAND
FEET)
Figure
20.
OBOGS
output
with
"USAFSAM"
controller:
oxygen
concentration
vs
altitude,
with
10-1/min
product
flow
and
inlet
temperatures
(Tin) from
50
to
100
0C.
27
V .. "." "."
,;
••
,"•"-
•
,-"-
•. .. . , ......"," '" " " " " "-

*.oo-
rw 7
90
/
I /
.80
J
S
70
110 /
z
6
-5
J0
0C
0
0
C
*
S60 "
3
0
-.
20
I I I
0
5
8
10
15
20
25
30
35
CABIN
ALTITUDE
(THOUSAND FEET)
i
I
I
I I
0
5
82326.5
36.5
49
75
PRESSURIZED
AIRCRAFT
ALTITUDE
(THOUSAND
FEET)
Figure
21.
OBOGS
output
with
"USAFSAM"
controller:
oxygen
concentration
vs
altitude,
with
50-1/min
product
flow
and
inlet
temperatures
(Tin)
from
50
to
1000C.
Monitor
The
OBOGS
oxygen
monitor
output
was
compared
in
the laboratory
with
that
of a
Perkin-Elmer
respiratory
mass
spectrometer
and
found
to
be
lin-
ear.
The
monitor
output
voltage
was
externally adjustable
from
the
front
cover
of
the
regulator/monitor
package.
Removing
the
front
cover
exposed
electrical
terminals
that
let
the
monitor
output
voltage
be
read
and
allowed
air
to
enter
the
monitor
cavity.
A
potentiometer
was
adjusted
so
that
the
monitor
output
voltage
read
the
desired
voltage
as
calculated
by
the
formula
Desired
monitor
output
voltage
= (A X
B)/29.92
where
A =
the
local
barometric
setting
in
inHg,
and
B
=
percent
of
oxygen
in
gas
entering
the
monitor
cavity
(21%
for
air).
28

Regulator
The
F-16A
OBOGS
regulator
is
a
low
inlet
pressure,
nondiluting,
pressure-demand
regulator
that
delivers
approximately
1-in-wg
positive
static
safety
pressure
at
all
altitudes
from
ground
level
to 38,000-ft
cabin
altitude,
where
pressure
breathing
begins.
The
regulator
was
designed
to
reduce
resistance
to
breathing
and
to
provide
pressure
breathing
for
alti-
tude
protection
up
to
50,000
feet.
Regulator
evaluation
consisted
of
both
static
and
dynamic
testing.
Figure
22
depicts
mask-cavity
pressure
observed
for
various
product
flows
under
steady
flow
conditions
(all
tests
were
performed
with
a
P/Q
mask
unless
otherwise
stated).
The
regulator
delivered
up
to
50
I/min
static
flow
and
maintained
1-in-wg
safety
pressure
with
inlet
pressures
as
low
as
20
psig.
Above 50
1/min
steady
product
flow,
higher
inlet
pressures
improved
regulator
performance.
A
continuous
flow
of
200
1/mmn
was
obtained
with
inlet
pressures
above
30
psig.
A
breathing
machine
that
produced
a
sinusoidal
breathing
pattern
was
used
to
test
dynamic
regulator
performance.
Figure
23
indicates
the
maximum
and
minimum
mask-cavity
pressures
observed
when
peak
inspiratory/expiratory
flow
was
varied
from
30
to
200
1/mmn.
Regulator
performance
was
a
function
of
inlet
pressure
(set
at
40
psig
in
Fig.
23),
outlet
peak
flow,
and
rate
of
change
in
outlet
flow.
The
breathing
machine's
tidal
volume
and
frequency
were
first
set
to obtain
a
breathing
pattern
of
30
1/mmn
peak
inspiratory
flow
(Q
peak),
with
a
maximum
rate
of
change
in
inspiratory
flow
(Q
dot
max)
of
3
1/sec4.
Different
settings
were
then
used
to
obtain
peak
flowý,
and
corresponding
makimum
rate
of
change
in
flo
Ys,
of
110
I/min,
11
1/sec4;
1i0
I/min,
15
I/sec4:
and
200
I/min,
20
I/sec
.
Thus,
Q
dot
max
(in
I/sec
)
equals
Q
peak/1O (in
1/min).
Mask-cavity
pressure
swing,
shown
in
Figure
24,
was
the
difference
between
maximum
inspiratory
and
expiratory
mask-
cavity
pressure.
As
cabin
altitude
increased
to
approximately
20,000
feet,
resistance
to
breathing
decreased
as
indicated
in
Figures
25
and
26.
Figure
25
displays
the
mask-cavity
mlnimum-and
maximum-pressure
curves
with
a
breathin
demand
(minute
volume)
of
30
1/min
peak
flow
and
a
Q
dot
max
of
3
I/sect.
With
breathing
demand
at
200
1/mmn
(Fig.
26),
resistance
to
breathing
was
greater
than
with
demand
at
30
1/min.
As
cabin
altitude
went
above
38,000
feet,
the
regulator
pressure
breathing
schedule
increased
the
mask-cavity
pressure.
Figure
27
shows
this
relationship
with
a
steady
flow
of
50
1/min.
Figure
28
data,
obtained
with
dynamic
breathing
peak
flow
of
30
1/
min, shows
the
minimum
and
maximum
mask
pressure;
the
average
of
these
pressures
is
shown
in
Figure
29.
Figures
30
and
31
are
similar
to
Figures
28
and
29
but
with
peak
flow
set
at
110 1/mmn.
29
• • ' •,• ; ., • '. •, " ' , ' , .,.
, ,.' ,
,,'
../ ..•. , -., ' -.•" ... ., .. .-, ..- • , .- ,.. ., , ., .• , .' .' .-.." •.
.. -.. ' ,.

3
-0
1.5
S~z
to
cc-
-
"•'P
• 3-3
-4.5
0
40
so
120
160
200
FLOW
(LITERS/MIN)
Figure
22.
Concentrator,
regulator,
and
P/Q
mask:
mask-cavity
pressure
vs
steady
flow
at
ground
level,
with
inlet
pressures of
20,
30,and
40
psig.
(2
=
20,
3
30,
4
=
40
psig)
30

4
z
W 2
cc
12
0 0so1016 0
PEKISPRTR FO LTESMN
-31

7
?j
.4
3
2
0
1j
0
. .. II
0
40
so
120
ISO
200
PEAK
INSPIRATORY
FLOW
(LITERS/MIN•)
Figure
24.
Concentrator,
regulator,
And
P/0
mask:
mask-cavity
pressure
swing
vs
dynamic
flow
at
ground
level,
with
40-psig
inlet
pressure.
W 32
•."

3 '
2.51
2
z
CLJ
1;4
cc
an
3-/ef1dtmx
337
1'

BSI
6
"
5
7'
3
W
W 2
-2
w
S.-
b-a
F-1
Ii
-2
0
5
10
15
20
25
CABIN
ALTITUDE
(THOUSAND
FEET)
Figure
26.
Concentrator,
regulator,
and
P/Q
mask:
mask-cavity
pressure
vs
altitude,
with
40,-psig
inlet
pressure,
200-1/mmn
dynamic
Q -
peak,
and
20-1/sec
2 Q
dot
max.
34

S,
--S S
°
-
o
--.-S '
17
15
'Si 13
z
.IU 7
cc
iJ.i"
40 s0
0
10
20
30
4
CABIN
ALTITUDE
(THOUSAND
FEET)
Figure
27.
Regulator
pressure breathing
schedule"
mask-cavity
pressure
vs
inpressurized
cabin
altitude,
with
40-psig
inlet
pressure
and
50-1/min
steady
flow.
4 35
.......
........
.............

20
i-
14
z
1.4]
0-I 12
10
10
p8j
(II
"44
2t
:'-1
E SO
CABIN
ALTITUDE
(THOUSAND
FEET)
Figure
28.
Regulator
pressure
breathing
schedule:
mask-cavity
pressure
vs
unpressurized
cabin
altitude,
with
40-psig
inlet
pressure
and
~
30-1/mmn
dynamic
Q
peak.
(A
maximum,
B =minimum
pressure)I
36
Fl
I
,. -
p
~ - . .
..
J

20
14
z
W 12
'IL
10
L-
Uj 8
4
2
Figt~re
29.
Rcyulator
pressure
breathing
schedule:
average
mask-cavity
pressure
vs
unpressurized
cabin
altitude,
with
40-psig
inlet
pressure
and
30-1/mmn
dynamic
Q
peak.
37

20
18
18
14
z
Z"12
10
i,-
>
8
(gJ
Uj
4
2
0~4 s
o
.. _ ..
30
35
40
45
CRBIN
ALTITUDE
(THOUSAND
FEET)
Figure
30.
Regulator
pressure
breathing
schedule:
mask-cavity
pressure
vs
unpressurized
cabin
altitude,
with
40-psig
inlet
pressure
and
110-1/min
dynamic
Q
peak.
(A -
maximum,
B
=
minimum
pressure)
38
t - .' ,• ' ' , " ,. :' . T, . " ," • ' . ' . ,. ' , " • "
. . " " , "'. , " . " , "' , " . ' . " , - . " . '. , " . -" . - . ' " , . " " . .- ." .- , .-. - . . - ., ' . - " -_• . " - '.. " ..

20
18
18
0 14
z
W 12
C,,
eL
.1r
 4
0.
J
2.
30
35
40 45
50
CABIN
ALTITUDE
(THOUSAND
FEET)
Figure
31.
Regulator
pressure
breathing
schedule:
average
mask-cavity
pressure
vs
unpressurized
cabin
altitude,
with
40-psig
inlet
pressure
and
110-1/min
dynamic
Q
peak.
39

-. .
w '
As
the
inlet
air
pressure
cycles
through
the
concentrator
beds,
the
OBOGS
product
pressure
simultaneously
cycles.
Peak
pressure
at
the
regula-
tor
inlet
was
approximately
38
psig,
while
the
minimum
pressure
varied
with
product
gas
flow.
Prior
to
OBOGS
laboratory
testing,
there
was
concern
that
minimum
product
pressure,
or
regulator
inlet
pressure,
might
be
insufficient
to
operate
the
regulator.
Also, if
regulator
inlet
pressure
dropped
below
10
psig,
the
BOS
might
be
activated.
Regulator
inlet
pressure
was
a
func-
tion
of
(1)
OBOGS
outlet
gas
pressure,
(2)
the
length,
diameter,
and
routing
of
the
connecting
line
between
the
concentrator
and
regulator,
and
(3)
product
gas flow.
Figure
32
shows
the
regulator
outlet
(product
gas)
flow,
mask-cavity
pressure,
and
regulator
inlet
and
outlet
pressure
when
the
peak
concentrator
inlet
pressure
was
40
psig.
With
peak
product
flow
of
approxi-
mately
150
1/min,
the
regulator
received
sufficient
inlet
gas
pressure
(23-38
psig)
to
operate
correctly.
A
mask-cavity
pressure
swing
from
-1.0
to
+4.5
in-wg
corresponded
to
a
comparable
swing
in
regulator
outlet
pres-
sure.
As
the
OBOGS
concentrator
flow
alternated
from
bed
to
bed,
the
regu-
lator
inlet
pressure
cycled
from
38
to
23
psig
due
to
the
intermittent
pressurization
of
the
beds.
As
product
gas
was
delivered
to
the
mask,
corresponding
reductions
occurred
in
the
regulator
inlet
pressure.
When
these reductions
synchronized
with
minimum
concentrator
outlet
pressures,
the
resultant
regulator
inlet
pressure
was
at
a minimum.
The
synchronizing
effect
is
also
demonstrated
in
Figure
33,
where
peak
product
flow
was
set
at
200
1/min.
On
every
fourth
breath,
product
demand
synchronized
with
minimum
concentrator
outlet
pressure.
When
this
happened,
regulator
inlet
pressure
dropped
to
15
psig,
which
was
sufficiently
low
to
affect
regulator
performance.
As
the
regulator
attempted
to
deliver
a
200-
1/min
breath
in
synchrony
with
minimum
concentrator
outlet
pressure,
the
inspiratory
mask-cavity
pressure
(-4
vs
-3
in-wg)
increased
slightly.
This
occurred
because
the
regulator
diaphragm
had
opened
farther
than
usual
to
compensate
for
the
reduced
regulator
inlet
pressure.
The
subsequent
expira-
tion
therefore
required
an
increase
in
mask-cavity
pressure
to
overcome
the
product
gas flow
and
open
the
expiratory
valve.
The
result
was
an
increase
in
expiratory
resistance
from
6
to
19
in-wg,
and
a
reduction
in
peak
flow
for
these
"restricted"
breaths
to
about
185
1/min.
The
synchronizing
effect
between
product
gas
flow
and
concentrator
out-
let
pressure
did
not
degrade
regulator
performance
with
peak
product
flow
up
to
150
1/min.
Only
the
highest
product
flow
(200
1/min)
produced
a
notice-
able
change
in
mask-cavity
pressures.
Also,
mask-cavity
pressure increased
only
when
the
peak
product
flow
coincided
with
minimum
concentrator
outlet
pressure.
Our
considered opinion
is
that
this
will
occur
infrequently
during
normal
operation;
and
even
if it
should
occur,
the
pilot
may
feel
only
a
harmless,
transitory
puff of
pressure
in
the
mask
cavity
during
expiration
and
may
notice
only
a
very
mild
restriction
of
inhalation
for
a
single
breath.
40
......................

200
REG
OUT
100
-
(1MIN)
-*
-
-...
.......
MASK
0
(IN-WG)
________
i
-25
______________
'50
_ _ _ _ _
_
+E
N
25
T-1luLi.:i___
(PIN-G)
I .
-25
presur
Ond
15
1/m-
dynam-
pea
fo
m
inum
nlet
I.-25
41

C.., 74
200
REG
OUT
100
.::. .....
:1
(1MIN)
+25
7'zr m
P
K(IN-WG)......
-25
5PI
)0
111
:
:-6
T_______.
... ....
.. .-
A.n
-..
--
-E
N
25
I "T 11
Figure~~~~~~~~~~~~~~~:
337ocnrtr
euaoadms
efrac
ih201m
+252

Mask
Three
masks--the
United
Kingdom
P/Q
and
the
USAF
MBU-5/P
and
MBU-12/P--
were
tested
with
the
other
OBOGS
components.
Dynamic
tests
included
flow
rates
from
20
to
200
I/min
as
indicated
in
Figure
34. Each
mask
gave
simi-
lar
pressure-swing
characteristics
at
the
20-1/mmn
flow
rate.
However,
as
peak
flow
increased,
the
P/Q
mask
exhibited
a
much
lower
resistance
to
breathing.
Up
to
100
I/min,
the
expiratory
mask-cavity
pressure
was
similar
for
all
masks;
however,
the
inspiratory
pressure
was
much
less
in
the
P/Q
mask.
At
higher
flow
rates
(such
as
those
experienced
during
speech
or
M-1
maneuvers),
the
P/Q
mask
gave
a much
lower
pressure
swing
than
did
the
MBU-5/P
or
12/P
mask.
"16
I.-.
I
l12i 12
9
4,
t5
11
20....
.. I
O18.
t2C
S/
'. I-I 1.2
-'. ' O
,~ue3.
Compariso
ofte-Qakwt
th
M:J12-
ndMBI-/P
msks
...... :
' , .
• .ii. ..4 * ... .
2' ' " !1
i ' " i... .. ... ..
FLO
(. / I
N).
•
Sfigure
34.
Comparison
of
the
PIQ
mask
with
the
MBU-121P
and
MBU-5/P
masks.
• 43

Selector
Valve/BOS
The
OBOGS
selector
valve
was
tested
to
verify
proper
operation
during
manual
and
automatic
switching
between
OBOG
and
BOS.
During
this
test,
the
oxygen-low
and
selector-valve
lights
were
monitored
and
the
mask-cavity
pressure
and
product
gas
composition
were
recorded while
various
malfunc-
tions
were
simulated.
Results
of
this
test
are
shown
in
Table
1.
Manual
and
automatic
switching
of
the
selector
valve
functioned
as
specified
under
all
conditions.
Caution-light
symbology,
however,
was
not
completely
straightforward.
When
the
selector
valve
was
in
the
backup
position,
the
SV
yellow
caution
light
stayed
lst
after
the
backup
bottle
was
depleted
(case
4C,
Table
1).
Also,
when
the
selector
valve
was
in
the
OBOG
position,
the
SV
caution
light
did
not
illuminate
when
the
system
pressure
was
below
10
pslg
even
though
the
BOS
was
supplying
the
breathing
gas
(case
2C).
The
selector
valve
regulated
BOS
pressure
from
1800
to
60
psig
in accordance
with
the
OBOGS
specification.
Therefore,
whenever
the
BOS
was
selected,
mask-cavity
pressure
was
not
affected.
TABLE
1.
F-16A
ONBOARD OXYGEN
GENERATING
SYSTEM
SWITCHOLOGY
Selector
Lights
Gas
valve
OXY
SV
source
Condition/Mal
function
1 A
OFF
--
OBOG
Normal;
Bottle
empty;
DC
off
B
ON
ON
OBOG
Low
P02;
Low
pressure;
Press-to-Test
2
A
OBOG
--
OBOG
Cabin
a+.
<
31K;
Bottle
empty;
D
off
B
ON
BOS
Cabin
alt
>
31K
C
ON
-
BOS
Low
pressure
D
ON
-
OBOG
Low
P02
3 A
AUTO
OBOG
Cabin
alt
<
25K;
Bottle
empty;
DC
off
B
ON
BOS
Cabin
alt
>
25K
C
ON
ON
BOS
Low
P0;
Low
pressure
4
A
BU
-
ON
BOS
Normal
B
ON ON
BOS
Low
P02;
Low
pressure
C -
ON
OBOG
02
bottle
empty
D - -
BOS
DC
off
.
44

Rapid
Decompression
Testing
Rapid
decompression
testing
was
conducted
with
the
concentrator
main-
tained
at
aircraft
altitude
and
the
cockpit-mounted
components
at
cabin
chaberanda
large
accumulator
opened
quickly
to
allow
rapid
decompres-
sion.
Decompression
time
was
controlled
by
adjusting
the
orifice
size
between
the
two
chambers.
The
deirompression
time (delta
t)
was
measured
from
when
the
cabin
altitude
started
to
rise
until
90%
of
the
final
aircraft
altitude
was
reached.
Decompression
testing
was
conducted
with
a
breathing
p..
machine,
brass
mannequin
head,
and
a
P/Q
mask,
together
with
the
cockpit-
mounted components.
During
the
decompression,
peak
mask-cavity
pressure
was
recorded
and
plotted
against
1/delta
t
(Fig.
35).
During
unmanned
testing,
rather
large
peak
mask
pressures
occurred
due
to
the
experimental
setup.
Aj
leakproof
putty compound
sealed
the
mask
to
the
mannequin
head,
thus
preven-
ting
the
expanding
gas
from
venting
around
the
mask
seal.
Also,
the
breathing
machine
and
associated
plumbing
did
not
adequately
represent
the
this
type
of
experimental
setup
was
useful
to
verify proper
operation
of the
Vregulator
during
rapid
decompressions.
With
a2ekro
rnslms
el
expanding
gases
in
the
regulator
and
mask
supply
hoses
were
forced
to
escape
backward
through
the
regulator
relief
port,
reducing
the
regulator
outlet
pressure
until
the
compensated
mask
expiratory
valve
could
open
and
vent
K
expanding
gas
in
the
lungs
and
mask
cavity.
Figure
35
illustrates
the
linear
relationship
between
duration
of
decompression
and
peak
mask-cavity
pressure.
This
relationship
did
not
depend
on
initial
and
final
altitude
because
all
decompressions
represented
a 5
psi
differential
between
the
cabin
and
aircraft
pressures.
Acceleration
Testing
gThe
entire OBOGS
was
mounted
in
the
USAFSAM
centrifuge
and
tested
with
gloads
up
to
+10
Gz,
using
both
steady
and
dynamic
product
flows.
The
con-
centrator,
selector
valve,
and
regulator package were
independently
orien-
ted
with respect
to
the
Gz
vector
while
system parameters
were
recorded.
The
only
component
that
demonstrated
anyGz
effect
was
the
P/Q
mask
which
:
tended
to
leak
around
the
expiratory
valve
under high-GZ loads.
This
effect
was
strictly
a
mask
phenomenon'
and
did
not
degrade OBOGS performance.
No
other
adverse
effects were noted
during
acceleration
testing.
I.
.4
451

80
I.W.
70
Iz
8O
CLC
141
La1%50
0)
DIN
I.-
30
20
10
p
i
.. .
0
1
2
3
4 5
1 /
DELTA
T
(SECmu-1)
Figure
35.
Unmanned
rapid
decompression
testing:
peak
mask-cavity
pressure
vs
decompression
time
(1/delta
t),
with
40-psig
inlet
pressure.
(initial/final
altitudes
(K
ft):
A ;
12/30,
B
=
16.8/40,
C
=
8/
20)
46

~'
7-1-
7-
.4
MAN
RATING
OBOGS
nian
rating
consisted
of
having
human
subjects breathe
from
the
system
during
altitude-chamber
flights,
rapid
decompression
test-Ing,
and
acceleration
testing.
Altitude
Testing
Five
subjects
were
used
for
OBOGS
altitude
tests.
The
altitude
profile
included
breathing
at
ground
level,
first
while
the
subjects
were
at rest
and then
while
talking.
The
subjects
also
exercised
at
light
and
medium
work
loads
on
a
bicycle ergometer,
in
silence
and
then
with
speech.
The
rest
/exerc
ise/speec
h
protocol was
repeated
at
8,000-ft
altitude.
Normal
breathing
with
speech
was
repeated
at
22,000
feet
and
at
40,000
feet.
Cabin
altitude
was
then
reduced
to
10,000
feet,
where
M-1
maneuvers
were
performed.
During
these
tests,
mask-cavity
pressure
and
product
gas
composition
and
flow were
recorded
in
addition
to
several
other system
and
physiological
parameters.
The
concentrator
was
supplied
with
80
0C
inlet
air
at
40
psig.
Product gas
composition
stayed
within the
specified bounds
(Fig.
36),
and
the
system
automatically
switched
to
BOS
as
cabin
altitude
exceeded
25,000
-
feet.
Between 25,000
and
31,000
feet,
the
subjects
could
manually
select
OBOGS
product
gas
via
the
selector
valve;
above
31,000
feet,
BOS
gas
was
automnatically
delivered
to
the
subjects.
Figure
37
is
a
scatter
diagram
that
indicates
mask-cavity
pressure
as
a
function
of
peak
Inspiratory
flow
and
altitude.
As
expected,
.mask-cavity
pressures
increased
with
increasing
product
flows. The
variation
in
mask
pressure
at
any
one
product
flow was
due
to
the
different
breathing
patterns
and
rates of
change
in
flow
for
different
subjects,
which
resulted
from
different
types
of
activities;
i.e.,
rest,
exercise,
speech,
and
M-1
maneuvers.
Variation
in
mask
pressure
was
also due,
in
part,
to
the
I
synchronizing
effect
between
the
concentrator
and
product-demand
flow.
SIRapid
Decompression
Testing
Four
subjects were
used
for
rapid
decompression
testing..
The
subjects
were
placed
in
a
decompressible
altitude chamber
with
the
OBOGS.
regulator,
selector
valve,
and
BOS.
The
concentrator
was
placed
in
an
altitude
chamber
that
was
maintained
at
aircraft
altitude.
Two
subjects underwent
rapid
decompressions
from
8,000
to
23,000
feet,
and
two from
16,800
to
40,000
feet.
These
results
are
plotted
in
Figure
38.
A
comparison
of
manned
-v
s-unmanned
rapid
decompressions
revealed
that
mask-cavity
pressures
for
decompressions
of
similar
duration
were
much
lower
in
the
manned
decompressions
and
were
well
within
the
desired
mask-cavity
limits.
Because
of
human-safety
considerations,
the
manned
decompressions
were
of
much
less
duration
than
many
of
the
unmanned
decompressions.
47...........................
-.

100
j
I
II
90
8C
I,.-1
U
B-.
-
70
Z3
* I
cc
I-- 2:1
U
60
z
C
40
4o
I
30
,
a
0
a
8
s
24 32
40
CRBIN
ALTITUDE
(THOUSAND
FEET)
Figure
36.
Human
breathing:
oxygen
concentration
vs
cabin
altitude
with
40-psig
inlet
pressure,
80
0C
inlet
temperature,
and
minute
volumes
of
0-20,
20-40,
and
40-60
1/min.
(1
=
0-20,
3 =
20-40,
5
40-60)
48
..................................
".,.................•,1

20
18
12
12P
Q 4 0
too
to
2
00
S
0
0
o
'
osS,
00
000
L
0
•€ 2
cc
p..
-12
-2
0
-8 2
4
I4
-124
"-20
a a I
0
40
80
120 180
200
PERK
PRODUCT
FLOW
(L/MINi
Figure
37.
Human
breathin~g:
peak
mask-cavity
pressure
vs
peak
product
grun
level
and
8K,
22K,
and
40K
feet.
(0
=
8K,
2
:22K,
4r ~ =.. ...
.lw
wih4-sg4neOKrsur)n
ai
attd
tK

13
12
I--
10
9 9
7I
0
9
i1.2 "
1/DELTA
T
(SEC**-j)•
Figure
38.
Human
rapid
decompression
testing:
peak
mask-cavity
pressure
vs
decompression
time
(l/delta
t),
with
40-psig
inlet
pressure
and'
initial/final
aircraft
altitudes
(K
feet)
of
8/23
and
16.8/40.
(A
8/23,
B
16.8/40)
/ 5
DET
50

Acceleration
Testing
Four
subjects were
used
for
manned
acceleration
testing.
All
cockpit
components
were
mounted
in
the
centrifuge
in
the
normal
cockpit orienta-
tion.
The
concentrator
was
not
installed
in
the
centrifuge
because
of
space
14kl
limitations.
The
regulator
was
supplied with
a
bottled
gas
supply.
The
subjects
were
experienced
centrifuge
riders
and
were
asked
to
perform
M-1
straining
maneuvers
as
necessary
to
prevent
grey-out.
Data
from
three
sub-
jects
(Figs.
39-41)
indicate
that the
higher
Gz
loads
required
more
forceful
M-1
manuevers
and
created
sharper
and
deeper
inhalation patterns
with
high
rates of
change
in
flow
that resulted
in
more
negative
mask-cavity
pres-
sures.
This
does
not
imply
that
higher
Gz
loads
affected
the
regulator.
Comparing
these data
with
human
altitude
data
(Fig.
37)
indicates
that
similar
peak
product
flows
produce
similar
minimum mask-cavity
pressures.
For
example,
acceleration
testing
of
the first two
subjects produced
inspi-
ratory
mask
pressures
of
-4
to
-11
in-wg
for
product
flows
of
approximately
170
1/mmn.
Altitude testing produced
inspiratory
mask
pressures
of
approxi-
mately
-2
to
-16
in-wg
for
similar
product
flows.
The
variation
in
mask
pressures
(more
noticeable
with
altitude
testing)
was
due
to
the
variation
inrate
of
change
in
flow.
The
fourth subject
in
acceleration
testing
was
akdto
breathe
from
the BOS
supply.
No
difficulties
were
encountered,
and
mask-cavity
pressures
were
well
within specified
limits.
RECOMMENDATIONS
During laboratory testing
of
the
F-16A
OBOGS,
spiveral
items
of
interest
were
noted
and
will be
reported
here
with
the
intent that
they
be
ccnsidered
as
recommendations
for
future
improvements.
Some
suggestions
would
not
be
costly
to
incorporate
into
future F-16 OBOGS.
The iUeas
presented
in
this
section
are
not
necessarily
afterthoughts:
some
suggested
features were
intentionally
not
incorporated
in
the
flight
demonstration
program
in
order
to
minimize
aircraft
modifications.
Concent
rator
Overall,
the
F-16A
concentrator
performed
in
a
satisfactory
manner.
*The
most
severe
problem
encountered
in
laboratory
testing
was
failure
of the
rotary
valve's
electric-motor
phasing
capacitor.
This
nonstandard capacitor
had
to
be
replaced
with
a
hermetically
sealed
capacitor
rated
at
115
VAC
at
400
Hz.
In
this
single-phase
system,
the
capacitor
induced
a
phase
differ-
ence
between
the
motor
windings which
produces torque.
The
capacitor
could
be
eliminated
by
modifying
the
aircraft
to
make
three-phase
power
available
for
the
concentrator
and
by
using
a
three-phase motor
on
the
concentrator
inlet
valve.
While
an
electrical
modification
of
this
type
would
be
econom-
ical
in
the
short
term,
longer
term
consideration
should
be
given
to
replac-
ing
the
electric
motor with
a
pneumatic
valve
assembly
to
drive
the
rotary
valve
with
bleed
air
pressure.
51
.N
...

0
44
-1.5
4 4
7
-3
4
z
-4.5
cc 7
E!
M
-74*5s
LU'
U,.
-9
I-...
P P:
E
1:12E
-.9
-10,5
- 1
2
,,ai a
70"5
100 125
150
1'75
200
PERK
PRODUCT
FLOW
(L/t1!N)
Figure
39.
Human
acceleration
testing
(subject
No.
1)
with
G
levels
of
1,
4,
and
7
Gz:
mi-nimum
mask-cavity
pressure
vs
peak,
product
flow.
52

I0
4
3
7 1
.-
1.5
6*
-3 ~
;JJ
F11
cc
-4.5
-9
z
a
II
I
-I A,,"
5100
125
IS
175
200
PERK PRODUCT
FLOW (L/MIN)
V
Figure
40.
Human
acceleration
testing
(subject
No.
2)
with
G
l
evel
s
of
1,
3, 5, 6, 7 ,
and
8 G
minimum
mask-cavity
pressure
vs
peak
product
flow.
53
:'i I O 5 .• :-

,•I
,N
. i
H
77
-;)
77
-3'
0z
-4.5
ca
I-
-10.
z i:
-12
!--9
so
75
100 125
150
175
200
PERK
PRODUCT
FLOW
(L/MIN)
Figure
41.,
Human
acceleration
testing
(subject
No.
3)
with
G
levels
of
4
and
7
Gz:
minimum
mask-cavity
pressure
vs
peak
product
flow.
54
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The
F-16A
concentrator
did
not
have
a
vent
in
the
inlet
air
supply.
Placing
a
vent
in
the
inlet
filter
housing
would
allow
any
accumulation
of
moisture
to
escape overboard
without
entering
the
molecular
sieve
bed.
This
vent
should
be
incorporated
in
future
OBOGS
concentrators
to
prevent
water
loading
of
the
zeolite
beds,
which
slowly
depresses
oxygen
output.
Coordi-
nation
with
the
aircraft
manufacturer
can
ascertain
if
a
drain
line
should
be
added
to
dump
moisture
outside
the
aircraft.
The
product
gas
line
diameter
was
minimally
acceptable
for
concentrator
inlet
pressures
of
40
psig.
The
combination
of
low
inlet
pressure
and
high
product-gas
consumption
may
affect
regulator
performance
by
increasing
breathing
resistance.
Increasing
the
product
gas
line
diameter and/or
add-
ing
a
plenum
in
the
cockpit,
functionally
located
just
prior
to
the
regula-
tor
inlet
port,
can
reduce
this
effect.
This
modification
appears
mandatory
for
the
F-16B
OBOGS
to
adequately
supply
two
crewmembers.
Regul
ator
Regulator
performance
was
satisfactory
if
concentrator
inlet
pressure
remained
at
or
above
40
psig.
The
test-mask
feature
delivered
17-in-wg
pressure
which
was
considered
high
by
the
test
subjects
and
somewhat
uncom-
fortable.
Reduced
test
mask
pressure
(12
in-wg)
would
improve
comfort
with-
out degrading
the
test
procedure.
Also,
from
an
operational
point
of
view,
the
system
test
button
on
the
regulator
package
could
be
improved.
The
button
must
now
be
held
fully
depressed
for
20
seconds
to
complete
the
test.
When
wearing
gloves,
the
pilot
cannot
easily
determine
if
the
button
is
fully
depressed,
and
20
seconds
is
considered
too
long
to
dedicate
for
this
test
during
preflight.
The
button
should
be
replaced
with
a
detent-
type
button
which
the
pilot
can
lock in
the
test
position.
The
pilot
can
then
make
other
preflight
checks
and,
when
the
indicator
lights
illuminate,
can
press
the
button
again
to
return
the
system
to
normal.
A
lighted
indi-
cator
might
also
be
incorporated
to
verify
switch
position.
Another
feature
of
the
regulator
that
warrants
improvement is
the
safety
pressure.
Now
the
pilot
must
turn
the
selector
valve
off
to
remove
the
mask
without
activating
the
BOS.
This
is
an
unsafe
practice
as
the
pilot
could
forget
to
turn the
selector
valve
back
to
normal
after
redonning
the
mask.
A
provision
on
the
regulator
to
turn
off
the
safety
pressure
would
allow
the
pilot
to
remove
the
mask
inflight
without
activating
the
BOS.
It is
unrealistic
to
ask
the
pilot
not
to
remove
the
mask
inflight;
consequently,
a
selectable
safety
pressure
switch
is needed
on
the
regulator.
Controller
In
the
laboratory
test
program,
the
controller
had
to
be
adjusted
several
times
to
obtain
the
desired
product
gas
composition.
Adjusting
the
controller
is
an
iterative
trial-and-error
process.
Multiple-adjustment
features
would
be
desirable:
one
to adjust
the
ground-level
flow
rate;
one
to
adjust
the
altitude
at
which
the
bleed
flow
begins
to
decrease;
and
one
to
adjust
the
rate
of
bleed
flow
shutdown.
These
features
may
be
techni-
cally
difficult
to
achieve,
and
some
may
not
be
necessary
if
the
flight
test
program
provides
a
realistic
range
of
concentrator
inlet
parameters.
55
i
p
I

However,
the
ECS
tap
point,
and
thus
concentrator
inlet
temperature,
may
change
when
the
F-16
OBOGS
goes
into
production.
Also,
the
manufacturing
process
must
maintain
sufficient
quality
control
in
producing
controller
diaphragm
springs
to
insure
accurate
oxygen
concentration
between
control-
lers.
Therefore,
a
provision
on
the
controller
to
satisfactorily
adjust
the
product
gas
composition
is
recommended.
The
controller
used
in
this
system
is
an
almost
completely
pneumatic
device.
Other
approaches
should
be
investigated.
Perhaps
using
an
elec-
tronic
device
or
a
mix
between
electronic
and
pneumatic
devices
may
be
advantageous.
Selector
Valve
Interpreting
the
selector-valve
switch
positions
was
difficult.
This
valve
could
and
probably
should
be
simplified
to
avoid
confusion
for
the
user.
Two
possibilities
are
available.
The
first
method
involves
using
a
two-position
selector
valve
switch
and
a
weight-on-wheels
(touchdown
bypass)
switch.
The
two
positions
on
the
selector
valve
would
be
labeled
OBOG
and
BOS.
In
the
BOS
position,
100%
oxygen
would
supply
the
mask
at
all
times,
including
ground
operations,
as
long
as
the
BOS
bottles
were
not
depleted.
In
the
OBOG
position,
concentra-
tor
product
gas
would
supply
the
mask
unless
P02
fell
below
195
mmHg,
or
regulator
inlet
pressure
fell
below
10
psig,
or cabin
altitude
rose
above
31,000
feet.
On
the
ground,
the
weight-on-wheels
switch
would
prevent
the
BOS
from
activating
during
a
system
test.
With
this
method,
as
well
as
the
next,
a
normally
closed
solenoid
switch
could
be
used
downstream
of
the
BOS
bottles
to
prevent
BOS
leakage.
The
solenoid
would
need
manual/nonelectri-
cal
override
for
ground
or power-off
operations.
The
second
and
preferred
method
of
simplifying
the
selector
valve
involves
replacing
the
weight-on-wheels
switch
with
a
third
position
on
the
selector
valve,
called
the
BOS
OFF
position
(Fig.
42).
With
the
selector
valve
in
the
OFF
position,
the
BOS
would
be
disengaged,
thus
allowing
the
system
test
to
be
activated
on
the
ground
without
consuming
BOS
gas.
The
OFF
should
be
a
push-to-turn position
to
prevent
its
inadvertent
use
in
flight.
In
the
current
OBOG
position
the
selector
valve
will
not
automatically
switch
the
BOS
if P0
2
falls
below
195
mmHg.
In
this
case
if
the
pilot
does
not
switch
the
selector
valve
to
AUTO
or
BOS,
and
if P0
2
falls
significantly
below
195
mmHg,
the
pilot
may
become
hypoxic.
In
other
switch
positions the
system
automatically
switches
to
BOS;
therefore,
to
be
consistent,
the
sel-
ector
valve
should
switch
to
BOS
if P0
2
falls
below
195
mmHg
in
the
OBOG
position.
As
with
the
controller,
perhaps
a
mix
of
electronic
and
pneumatic
devices
may
simplify
construction
of
the
selector
valve.
56
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Indicators
Several
shortcomings
were
noted
with
the
indicator
lights.
First,
in
conjunction
with
the
selector
valve
nomenclature,
is
the
interpretation
of
the
indicators.
The
meaning
of
an
illuminated
indicator
light
is
difficult
to
completely
translate
(reference
Table
1).
The
light
on
the
selector
valve
should
be
known
as
a
BOS
light
and
should
illuminate
only
when
100%
oxygen
is
supplied
to
the
mask.
The
BOS
light
should
not
illuminate
just
because
the
selector
valve
is
in
the
BOS
position,
i.e.,
when
the
selector
valve
is
at
BOS
but
the
BOS
bottle
is
empty.
Also,
if
100%
oxygen
is
being
supplied
to
the
pilot,
the
light
must
always
illuminate
(contrary to
the
present
condition
when
the
selector
valve
is
in
the
OBOG
position
and
cabin
altitude
is
above
31,OuO
feet).
A
magnetic
switch
placed
on
the
shuttle
valve
to
sense
BOS
flow
could
activate
the
BOS
light.
Also,
the
BOS
light
on
the
selector
valve
needs
to
be
relocated.
The
selector
valve
is
located
behind
the
control
stick,
so
the
light
is
not
visible
to
the
pilot;
it
also
interferes
with
the
knob
on
the
selector
valve.
Mounting
the
BOS
light
directly
above
the
BOS
pressure
gauge
would
direct
the
pilot's
attention
toward
BOS
pressure
when
the
light
illuminates.
This
would
reinforce the
need
to
monitor
BOS
pressure
when
it is
in
use.
The
F-16
instrument
panel
has
ample
room
for
the
light
in
this
position.
The
OXY
LOW
light
should
be
relabeled
as
OBOG,
to
indicate
an
OBOG
problem.
This
light
now
illuminates
due
to
low
PO2
or
low
regulator
inlet
pressure.
A
single
light
cannot
indicate
which
malfunction
exists;
perhaps
two
lights
may
be
necessary.
During
the
press-to-test
system,
all
indicators
should
illuminate.
Miscellaneous
As
the
flight
test
program
proceeds,
several
other
recommendations
may
become
apparent.
Any
change
must
not
interfere
with
the
integrity
of
the
BOS.
The
BOS
must
be
made
leakproof,
which
may
require
hard
line
tubing
in
lieu
of
flexible
tubing
from
the
BOS
manifold
to
the
selector
valve.
The
selector
valve
must
be
able
to
seal
the
BOS
and
preclude
its
frequent
servicing.
CONCLUSIONS
The
F-16A
OBOGS
is
a
successful
system
which
promises
to
overcome
all
lox
shortcomings--the
hazards
of
storing
and
handling,
the
expense
and
logistics
inherent
with
lox,
the
cost
of
stockpiling
and
replacing
lox
con-
vertors
and
ground
carts,
the
unacceptable
service
delays
which
increase
turnaround
time
in
wartime
environments,
and
possible
limits
in
mission
dur-
ation
due
to
the
limited
onboard
quantity
of
lox.
Laboratory
testing
proved
the
equipment,
built
by
Clifton Precision
according
to
USAFSAM
specifications,
to
be
adequate
for
flight
testing.
Adoption
of
the
laboratory
test
and
flight
test
recommendations
will
ensure
that
OBOGS
will
further
enhance
the
mission
of
the
F-16
aircraft.
58
-. >
-*I.-
' - - ..

DEPARTMENT OF
THE
AIR
FORCE
ARMSTRONG
LABORATORY
(AFMCJ
BROOKS
AIR
FORCE
BASE.
TEXAS
5Feb97
MEMORANDUM
FOR
DEFENSE TECHNICAL
INFORMATION
CENTER
(DTIC)
FROM:
AL/XPPL
2509
Kennedy
Circle
Brooks
AFB
TX
78235-5118
SUBJECT:
Change
in
Distribution
Statement
for
USAFSAM-TR43-27,
AD-B076
849
1.
The
document listed above
has
been
reviewed
by
the
Public Affairs
Office,
Brooks
Air Force
Base,
Texas
and
has
been changed from
limited
distribution
to distribution
A,
unlimited
release
(see
attachment,
AL/XPPL
21
Jan
97
Ltr).
2.
Please
change the
distribution
statement
at
DTIC
and
make
available
to
NTIS.
JUDY'A.
BRYANT
AL
STINFO
OFFICER
Attachment:
AL/XPPL
21
Jan
97
Ltr
,9...0o°

DEPARTMENT OF
THE
AIR
FORCE
ARMSTRONG
LABORATORY
(AFMC)
BROOKS
AIR
FORCE
BASE
TEXAS
21
Jan
97
MEMORANDUM
FOR
AL/XP
(Dr. Miller)
AL/XPPL
IN
TURN
FROM:
AL/XPPL
SUBJECT:
AL/AO
Request
for
Release
of
Document to
Czech
Republic
1.
AL/AO
is
requesting
to
release
the
attached
report
(USAFSAM-TR-83-27
to
the
Czech
Republic.
This
report
has
a
Distribution
limitation
(as
of 1983);
however,
the
information
may
no
longer
need
protection
since
it
is
14
years.
At
the
time
of
its
publication,
Capt
Thomas
Horch
was
project
engineer
and
Dr.
Richard
L.
Miller
was
his
supervisor.
2.
As
former
supervisor
of
the
original
project
engineer, request
your
review
of
this
report and
recommendation
for
its
release
to
the
Czech
republic.
Request
you
also
review for
possible
downgrading
from
"Unclassified-Limited"
(export
controlled) to
"Approval
for
public
release." If
you
wish
to
downgrade
it,
we
will
send it
to
Public
Affairs
for
review and
approval.
Please
try
to
complete
your
review and
return
by
7
Feb
97.
.. If
you
have questions,
please
call--ext
5495.
Thank
you,
JUDY
A.
BRYAN
Foreign
Disclosure
Officer
Atch:
USAFSAM-TR-83-27
APPROVED FOR
RELEASE
TO
CZECH
REPUBLIC
or
NOT
RELEASABLE
RICHARD
L.
MILLER,
PhD
Deputy Director,
Plans
"PPROVED
FOR
DOWNGRADING
TO
PUBLIC
DOMAN
or
NOT
TO
BE
DOWNGRADED
RICHARD
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MILLER,
PhD
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Plans
(You
can
approve
both
if
you wish.)
i
,
7-