TM 55-4920-231-14
(2) Case leak (CL) provides for case leak
ment in the tester is used to test the accuracy of
test and/or calibration of fuel pressure gage (5,
aircraft manifold pressure gages.
figure 7) on tester.
The fuel pressure gage (5, figure 7) measures
The rate of-climb indicator (2, figure 7) re-
the pressure produced by the tester in a range
from 0 to 25 pounds per square inch (psi) and
cords the rate-of-climb or descent in feet per
is used to check the accuracy of aircraft fuel
minute (fpm), according to the increase or de-
crease of the vacuum produced by the tester,
pressure gages.
and is used to test the accuracy of aircraft rate-
of-climb indicators. It is graduated from 0 to
6000 fpm for climb on the upper half of the dial
The selector valve lever (5, figure 9) operates
the selector valve (4) which is in the line be-
and for descent on the lower half of the dial.
tween the oil reservoir (3) and the pump (2).
The lever has three positions as indicated on se-
24. ALTIMETER.
lector valve instructions (15, figure 4) for use as
The tester produces vacuum which simulates
follows:
altitude conditions and is recorded on the altim-
a. FILL, used when filling reservoir with oil.
eter (3, figure 7) in feet. It has a range from
b. RUN, used when testing instruments.
1,000 feet below to 80,000 feet above mean sea
c. DRAIN, used when removing oil from
level. A barometric scale (4) which is operated
reservoir.
by the correction knob (22) is an integral part of
the altimeter which is used to test the accuracy
of aircraft altimeters.
The safety valve knob (14, figure 4) turned
to its fullest extent clockwise, closes, and
counterclockwise, opens the safety valve (13). It
prevents excessive vacuum from damaging the
The correction knob (22, figure 7) provides
airspeed indicator.
for correcting the barometric scale (4) on the
altimeter (3) to the ambient barometric pressure.
The external case leak valve knob (8, figure
The airspeed indicator (6, figure 7) measures
and counterclockwise, opens the external case
the differential between pitot and static pres-
leak valve (10) which provides for case leak test
sures created by the tester in a range between
ing of aircraft instruments.
20 and 250 knots and is used to test the accuracy
of airspeed indicators.
The relation of the instruments and controls
in the electrical system to each other is illustrated
The manifold pressure gage (7, figure 7)
in figure 10.
measures the absolute pressure in inches of
mercury over a range from 10 in. to 75 in. with
30 in. Hg representing mean sea level. When
The interrelation of the instruments and con-
used at sea level, a reading below 30 in. Hg
trols in the vacuum and pressure system is illus-
represents vacuum and a reading above 30 in.
trated in figure 11.
Hg represents pressure in the tester. The instru-
