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Figure 2-8.—Model 1172AS100 vacuum system | Up
Aircrew Survival Equipmentman 1 & C - Aviation theories and other practices | Next
FLOW MEASURING SYSTEM |
Figure 2-10.—Model 1172AS100 chamber bleed system.
ALTITUDE SENSING SYSTEM
This system (figure 2-9) senses the pressure
(less 1 atmosphere) in the altitude chamber or suit
simulator tank. In this case, we refer to atmos-
phere as a unit of pressure equal to 14.69 pounds
per square inch. Both the high-range and low-
range altimeters are operated by differential pres-
sure. The high-range altimeter (12) senses the
altitude inside the chamber through the chamber
reference port (N/N). When you place the pres-
s u r e s e l e c t o r v a l v e ( O ) i n t h e A L T I T U DE
CHAMBER position, the low-range altimeter
senses the altitude through the same chamber ref-
erence port (N/N). The low-range altimeter also
senses the pressure inside the suit simulator tank.
You must place the reference pressure selector
valve (O) in the SUIT SIMULATOR position and
open the suit simulator reference shutoff valve (R)
for the low-range altimeter to read this pressure.
PRESSURIZING THE ALTITUDE
SENSING SYSTEM
When you pressurize the altitude sensing
system, be sure the reference pressure selector
valve (O) is in the ALTITUDE CHAMBER
position and open the vacuum control valve (Bl).
When you open the control valve (Bl), ascend to
50,000 feet. The altitude will be indicated on the
high-range altimeter (12). Stabilize with control
valve B1 at this altitude and check for leaks. Open
chamber bleed valve (K) and return to sea level.
Close valve (K) when you reach sea level. If you
find that the test stand has no leaks at this point,
turn the reference pressure selector valve (O) to the
SUIT SIMULATOR position; then open the suit
simulator reference shutoff valve (R) fully. Place
the flow selector valve (M) in the SUIT SIMULA-
TOR position. Now you are ready to ascend to
altitude. Open the vacuum control valve (Bl) and
ascend to 35,000 feet. This altitude will be in-
dicated on the low-range altimeter (13). Again
stabilize with control valve (B1) and check for
leaks. Close the vacuum control valve (Bl) and
return to sea level. To setup the test stand for the
chamber bleed system test, close the chamber
bleed valve (K). Place the reference pressure selec-
tor valve (O) in the ALTITUDE CHAMBER
position; close the suit simulator shutoff valve (R)
and place the flow selector valve (M) in the
REGULATOR position. Leave all valves and con-
nections in their present position.
CHAMBER BLEED SYSTEM
The chamber bleed system shown in figure
2-10 is a very simple system used to introduce a
2-11
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