TM 55-4920-231-14
to record the rate-of-dive readings on calibration
CAUTION
card (8, figure 7).
The case leak valve levers must be in
(3) When tests have been completed, stop
these positions and the safety valve
the tester (paragraph 37).
closed, to isolate the airspeed indicator
from the vacuum source to prevent dam-
age to the instrument.
(5) Make test hose connections (paragraph
CAUTION
38).
Do nut allow the altimeter reading to
(6) Start the tester (paragraph 36).
go below -1000 f t or the rate-of-climb in-
dicator to exceed 6000 fpm as it will
CAUTION
damage the instruments.
Do not exceed +6000 fpm on rate-of-
a. 0 to 50,000 FT. Test.
climb indicator during tests as it will
(1) Perform the master instrument tests
damage the instrument.
(paragraph 39a).
(7) Turn vacuum INCREASE knob (17,
(2) Turn correction knob (22, figure 7) to
provide a 29.92 reading on barometric scale (4)
quired readings (figure 12) by adjusting vacuum
on altimeter (3) and altimeter being bested.
DECREASE knob (19, figure 7).
(3) Place PRESSURE selector knob (10) in
(8) Calibrate the instrument by observing
OFF position and turn knobs (11 and 12) to
the readings and timing the interval (figure 12)
open valves.
to record the rate-of-climb readings on calibration
(4) Turn VACUUM selector knob (20) to
c a r d (8, figure 7).
ALT & R.O.C. 0-50,000 FT position and turn
b. Rate-of-dive Test.
knobs (17 and 19) to close valves.
(1) Turn vacuum INCREASE knob (17,
CAUTION
The case leak valve levers must be in
CREASE knob (19) to provide the required
these positions, and the safety valve
readings (figure 12).
closed, to isolate the airspeed indicator
(2) Calibrate the instrument by observing
from the vacuum source and prevent
the readings and timing the interval (figure 12)
damage to the instrument.
(5) Place case leak valve lever (3, figure
in CL position, and turn knob (14, figure 4)
to close safety valve (13).
(6) Make test hose connections (paragraph
38) and start the tester (paragraph 36).
CAUTION
Do not exceed +3000 fpm while testing
altimeters, nor +6000 fpm while testing
rate-of-climb indicators. Exceeding these
limits will damage the instruments.
NOTE
Tap altimeter lightly to remove friction before
recording readings at all calibration points.
(7) Turn vacuum INCREASE knob (17,
(8) Stabilize the required readings on al-
timeter (3, figure 7) by adjusting vacuum DE-
CREASE knob (19).
(9) Observe reading on instrument being
tested at each check point and record on calibra-
tion card (8).
