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TM 55-4920-400-13
2-11.
Pressure Bleed Down Knob.
Counterclockwise rotation of pressure down knob from
closed position opens a needle valve (10, fig. 1-1) allow-
ing system pressure to bleed off.CLOSE FOR PRES-
SURE UP.
2-12.
Pressure Up Knob.
Counterclockwise ro-
tation of pressure up knob from closed position opens a
needle valve allowing pressure in system to increase.
2-13.
Vacuum Down Knob.
Counterclockwise
rotation of vacuum Down knob permits system vacuum
to bleed off. CLOSE FOR VACUUM UP.
2-14. Vacuum Up Knob.
Counterclockwise rota-
tion of vacuum up knob opens a needle valve and pro-
vides increased vacuum in system.
2-15.
Case Leak Valve Levers.
The case leak
valve levers, located below calibration correction card
operates valves which provide for testing aircraft in-
struments and checking the master instruments on
tester for case leaks and/or calibration.
2-16. Rate-of-Climb Indicator.
The rate-of-
climb indicator records the rate-of-climb or descent in
feet per minute (fpm) according to the vacuum pro-
duced by the tester, 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 and
for descent on the lower half of the dial.
2-17. Altimeter.
The tester produces vacuum which
simulates altitude conditions and is recorded on the al-
timeter in feet. It has a range from 1,000 feet below to
Section III.
2-25. Preparation for Use.
To prepare the test
set for use proceed as follows:
a. Set test set on level bench or platform with a
source of dc or ac power available.
b. Look through window (9, fig. l-l) on right side
of test set and observe oil level in reservoir. Oil level
must be within points indicated for test set to operate
properly. If oil level is low, fill reservoir in accordance
with procedure given in paragraph 2-32.
80,000 feet above mean sea level. A barometric scale
which is operated by the correction knob is an integral
part of the altimeter which is used to test the accuracy
of aircraft altimeters.
2-18. Airspeed Indicator. The airspeed indica-
tor measures the differential between pitot and static
pressures created by the tester in a range between 20
and 250 knots and is used to test the accuracy of air-
speed indicators.
2-19. DELETED
2-20. Fill and Run Selector Valve Lever.
The
Selector valve lever is in the line between the oil reser-
voir and the pump under cover plate (fig. 1-1). The
lever has two positions for use as follows:
a. RUN, used when testing instruments.
b. FILL, used when filling reservoir with oil.
2-21. DELETED
2-22. External-Case Leak Valve Knob. The ex-
ternal case leak valve knob turned to its fullest extent
clockwise, closed, and counterclockwise, opens the ex-
ternal case leak valve which provides for case leak test-
ing of aircraft instruments.
2-23. Electrical System. The relation of the in-
struments and controls in the electrical systems to each
other is illustrated in figure 2-5.
2-24. Vacuum and Pressure System.
The in-
terrelation of the instruments and controls in the vacuum
and pressure systems is illustrated in figure 3-1.
OPERATION
Do not force-tighten needle valves.
c. Set power ON-OFF switch (12, fig. 1-1) to OFF,
close four Vacuum and PRESSURE needle valves (10
and 15) and set VACUUM and PRESSURE selector -
valves (7 and 16, fig. 1-1) to off.
2 -4
Change 2
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