TM 55-4920-231-14
(7) Allow altimeter (3), to reach release
to ALT position and observe altimeter (3, figure
point, observe reading and compare with sp
7) while timing for leakage. (Refer to table 3.)
ante listed in table 2.
(10) Slowly turn case leak valve lever (3.
(8) Slowly turn vacuum INCREASE knob
CREASE knob (17, figure 7) to close valve.
(17) to close valve and provide a reading of
(11) Turn vacuum DECREASE knob (19,
40,000 ft on altimeter (3), stabilizing the read-
ing by adjusting the vacuum DECREASE knob
the rate-of-climb indicator (2) and allow the in-
(19).
struments to return to their normal readings.
(9) Turn case leak valve lever (3, figure 8)
(12) Stop the tester (paragraph 37).
Table 2. Safety Relief Points
Tolerance
Relief Point
Instrument
+5,000 ft
Altimeter (0 to 50,000 ft)
50,000 ft
-0,000 ft
+8,000 ft
80,000 ft
Altimeter (0 to 80,000 ft)
-0,000 ft
Airspeed Indicator
+20 knots
250 knots
-O knots
Manifold Pressure Gage
+1 in. Hg
75 in. Hg
-1 in. Hg
+1 psig
Fuel Pressure Gage
25 psig
-O psig
50 fpm
Altimeter (negative altitude)
-1000 ft
250 fpm
40,000 ft
Altimeter (0 to 50,000 ft).
400 fpm
Altimeter (0 to 80,000 ft)
70,000 ft
6 kn/min
200 knots
Airspeed Indicator
Manifold Pressure Gage:
1/4 in. Hg/min
Vacuum
11 in. Hg
1 in. Hg/min
65 in. Hg
Pressure
1 psig/min
Fuel Pressure Gage
20 psig
CAUTION
b. 0 to 80,000 FT. Altimeter Tests.
(1) Place VACUUM selector knob (20,
Do not exceed a rate of change in alti-
tude of +3,000 fpm while testing altim-
tion and turn knobs (17 and 19) to close valves.
eters as damage to the altimeters may
(2) Place PRESSURE selector knob (10) in
result. Do not exceed +6,000 fpm dur-
OFF position and turn knob (11 and 12) to
ing these tests as it will damage the
close valves.
rate-of-climb indicator.
(6) Slowly turn vacuum INCREASE knob
CAUTION
(17, figure 7) to open valve and provide a read-
The airspeed indicator must be isolated
ing of 3,000 fpm on rate-of-climb indicator (2).
from the vacuum source to prevent dam-
age to the instrument.
(7) Allow altimeter to reach relief point
and observe reading (table 2).
(3) Place case leak valve lever (4, figure 8)
in CL position and turn knob (14, figure 4) to
(8) Slowly turn vacuum INCREASE knob
close safety valve (13).
(17, figure 7) to close valve and provide a read-
(4) Place case leak valve levers (3, 5, 7,
ing of 80,000 ft on altimeter (3). Stabilize the
and 8, figure 8) in NOR position.
reading by adjusting the vacuum DECREASE
knob (19).
(5) Start the tester (paragraph 36).
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