RATE-OF-CLIMB INDICATOR.

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.

28. FUEL PRESSURE GAGE.

23. RATE-OF-CLIMB INDICATOR.

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-

29. SELECTOR VALVE LEVER.

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

30. SAFETY VALVE KNOB.

of aircraft altimeters.

The safety valve knob (14, figure 4) turned

to its fullest extent clockwise, closes, and

25. CORRECTION KNOB.

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.

31. EXTERNAL CASE LEAK VALVE KNOB.

26. AIRSPEED INDICATOR.

The external case leak valve knob (8, figure

4) turned to its fullest extent clockwise, closes,

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.

32. ELECTRICAL SYSTEM.

The relation of the instruments and controls

27. MANIFOLD PRESSURE GAGE.

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

33. VACUUM AND PRESSURE SYSTEM.

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-