TM 55-4920-231-14
(3) Place case leak valve levers (3, 4, 5, 7,
(9) Turn case leak valve lever (3, figure
and 8, figure 8) in NOR position.
8) to ALT position and observe altimeter (3,
(4) Start the tester (paragraph 36).
table 3.)
(5) Slowly turn pressure INCREASE knob
(10) Slowly turn case leak valve lever (3,
(12, figure 7) to open valve, allowing pressure
to reach relief point (table 2) and observing
CREASE knob (17, figure 7) to close valve.
reading on manifold pressure gage (7).
(11) Turn vacuum DECREASE knob (19)
(6) Turn pressure DECREASE knob (11)
to provide a reading of 3,000 fpm on rate-of-
to provide a stabilized reading of 65 in. Hg on
climb indicator (2) and allow the instruments to
manifold pressure gage (7).
r e t u r n to their normal readings.
(7) Turn case leak valve lever (7, figure 8)
(12) Stop the tester (paragraph 37).
to CL position and observe manifold pressure
c. Negative Altitude Altimeter Tests.
gage (7, figure 7) while timing for leakage
(1) Place PRESSURE selector knob (10,
(table 3).
figure 7) in NEGATIVE ALTITUDE position
(8) Slowly turn case leak valve lever (7,
and turn knobs (11 and 12) to close valves.
(2) Place VACUUM selector knob (20) in
CREASE knob (12, figure 7) to close valve.
OFF position and turn knobs (17 and 19) to
(9) Turn pressure DECREASE knob (11)
open valves.
to open valve and allow reading on manifold
(3) Place case leak valve levers (3, 4, 5, 7,
pressure gage (7) to return to normal.
and 8, figure 8) in NOR position.
(10) Stop the tester (paragraph 37).
(4) Start the tester (paragraph 36).
e. Manifold Pressure Gage Vacuum Tests.
CAUTION
(1) Place VACUUM selector knob (20,
Do not exceed a rate of change in alti-
tude of +3,000 fpm while testing altim-
position and turn knobs (17 and 19) to close
eter as damage to the altimeter may
valves.
result Do not exceed +6,000 fpm during
(2) Place PRESSURE selector knob (10) in
this test as it will damage the rate-of-
OFF position and turn knobs (11 and 12) to
climb indicator. Do not allow altimeter
open valves.
reading to go below -1,000 ft. as it will
damage the instrument.
(3) Place case leak valve levers (3, 4, 5, 7,
and 8, figure 8) in NOR position.
(5) Slowly turn pressure INCREASE knob
(4) Start the tester (paragraph 36).
(12, figure 7) to open valve and provide a read-
(5) Turn vacuum INCREASE knob (17,
ing of l,000 ft. on altimeter (3). Stabilize
reading by adjusting pressure DECREASE knob
reach relief point (table 2) and observing read-
(11).
ing on manifold pressure gage (7).
(6) Turn case leak valve lever (3, figure 8)
to ALT position and observe altimeter (3, fig-
(6) Turn vacuum DECREASE knob (19)
ure 7) while timing for leakage. (Refer to
to provide a stabilized reading of 11 in. on
table 3.)
manifold pressure gage (7).
(7) Slowly turn case leak valve lever (3,
(6) Turn vacuum DECREASE knob (19) to
provide a stabilized reading of 11 in. on mani-
CREASE knob (12, figure 7) to close valve.
fold pressure gage (7).
(8) Turn pressure DECREASE knob (.11)
(7) Turn case leak valve lever (7, figure 8)
to provide a reading of 5000 fpm on rate-of-
to CL position and observe manifold pressure
climb indicator (2) and allow instruments to re-
gage (7, figure 7) while timing for leakage
turn to normal readings.
(table 3).
(9) Stop the tester (paragraph 37).
(8) Slowly turn case leak valve lever (7,
d. Manifold Pressure Gage Pressure Tests.
(1) Place VACUUM selector knob (20, fig-
CREASE knob (17, figure 7) to close valve.
ure 7) in OFF position and turn knobs (17 and
(9) Turn vacuum DECREASE knob (19)
19) to open valves.
to open valve and allow reading on manifold
(2) Place PRESSURE selector knob (10) in
pressure gage (7) to return to normal.
30''-75" MANIFOLD ABS PRESS position and
(l0) Stop the tester (paragraph 37).
turn knobs (11 and 12) to close valves.
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