CALIBRATE RATE-OF-CLIMB INDICATOR (CLIMB-DIVE)

TM 55-4920-416-13

Section IV

NAVAER 17-15C-539

Paragraphs 4-35 to 4-43

j. Stabilize the altimeter at the required check points by

NOTE

adjusting the VACUUM decrease control valve 1.

k. Stabilize the rate-of-climb indicator pointer at the

When tests have been completed, restore

required check points in the DIVE region by adjusting the

the original connections in the aircraft

VACUUM decrease control valve 1.

making sure that they are adequately

l. After completing all check points on the altimeter and

tightened so that they will not leak or

rate-of-climb indicator, throw power switch to OFF.

vibrate loose in flight.

m. Slowly open VACUUM control valves 1 and 2 until all

4-35. For tests of the complete aircraft pitot system, the

instruments return to normal.

VPT-7A is connected to the pitot tube itself by means of the

n. Turn VACUUM selector valve to OFF.

test hoses and special clamps and sleeves provide. (See

o. During this test, disregard any movement on the

figure 4 -4.) Connection procedures are as follows:

airspeed indicator.

a. Select the appropriate clamp, round or oblong, and fit

it carefully over the pitot tube so that the hole leading to the

4-39. CALIBRATE RATE-OF-CLIMB INDICATOR (CLIMB-

clamp fitting is in line with the static hole on the pitot tube, and

DIVE). Adjust VACUUM control valves 1 and 2 in accordance

tighten clamp securely.

with paragraph 4-38. Set the master rate-of-climb indicator at

b. Attach suitable length of test hose from the clamp to

each point shown on the rate-of-climb indicator calibration

the quick-connect nipple marked ALTIMETER AND RATE OF

card. Enter the readings of the instrument under test on the

CLIMB.

calibration test card provided. If necessary, adjust the rate-of-

c. Select appropriate sleeve, round or oblong, fit

climb indicator to exactly zero before beginning this test.

adjustable hose camp on sleeve, and push firmly over the end

of pitot tube. Tighten clamp.

4-40. CALIBRATE ALTIMETER, 0 - 50,000 FT AND 0 -

d. Connect appropriate length of test hose to sleeve and

80,000 FT. Adjust VACUUM control valves In accordance with

to quick-connect nipple marked AIRSPEED. If single hose is

paragraph 4-38. Set the master altimeter at each point shown

too short, couple two together.

on the calibration card up to and including 50,000 feet or

e. At conclusion of tests do not fail to remove sleeve and

80,000 feet depending on altimeter. Enter the readings of the

clamp.

instrument under test on the calibration test card provided.

4-36. OPERATIONAL TESTS

AND

CALIBRATION

4-41. CASE

LEAK

TEST

(RATE-OF-CLIMB

AND

INSTRUMENTS.

ALTIMETER).

a. If necessary, adjust the pointer to read exactly zero

4-37. ALTIMETER AND RATE OF CLIMB TEST, 0 - 50,000

on the rate-of-climb indicator being tested.

FT AND 0 - 80,000 FT. Connect the test set to the Instruments

b. Adjust VACUUM control valves in accordance with

to be tested as indicated in paragraphs 4-34 and 4-35.

paragraph 4-38 and stabilize the altimeter at 18,000 feet.

c. Close needle valve on hose assembly to instruments

4-38. PROCEDURE FOR ALTIMETER AND RATE-OF-

being tested.

CLIMB TEST, 0 - 50,000 FT AND 0 - 80,000 FT.

d. Observe the altimeter being tested. The pointer

a. Set barometric indicator on Altimeter to 29.92.

should not move more than 100 feet in 10 seconds. A reading

b. Set barometric indicator on instrum ent being tested or

in excess of this indicates a possible case leak and will

calibrated to 29.92.

necessitate removal of the instrument.

c. Set PRESSURE selector valve at OFF.

e. Observe the rate-of-climb indicator being tested. The

d. Open PRESSURE control valves 3 and 4.

point should not indicate more than 60 fpm DIVE. Any

e. Set VACUUM selector at ALT. & R.O.C. 0 - 50,000 FT

readings in excess of this indicate a possible case leak and will

or 0 - 80,000 FT for 80,000 foot altimeter.

necessitate the removal of the instrument being tested.

f. Close VACUUM control valves 1 and 2.

f. Slowly open needle valve on hose assembly to

g. Throw power switch ON.

instruments being tested.

h. Slowly open the VACUUM increase control valve 2.

g. Return instruments to normal position accordin g to

The altimeter pointer will, rotate clockwise indicating an

instructions in paragraph 4-38.

increase in simulated altitude. At the same time, the rate-of-

climb indicator will move into the climb region.

4-42. Remove test hose connections in accordance with

i. Open the VACUUM Increase control valve 2 until the

paragraphs 4-34 and 4-35.

rate-of-climb indicator pointer stabilizes at the required

checkpoint.

4-43. ALTIMETER AND RATE OF CLIMB TEST NEGATIVE

ALTITUDE. When calibrating altimeters, at a considerable

height above sea level, it is necessary to provide pressure to

CAUTION

simulate sea-level or below sea-level indications on the

altimeter.

For instance, NAS Denver, Colorado, is

Do not exceed 6,000 fpm during this test

as damage will occur to the rate-of-climb

indicator.