TM 55-1510-222-MTF
TROUBLESHOOTING GUIDE B -
INSTRUMENTS
CONDITION
B1.
B2.
PROBABLE CAUSE
Airspeed indicator reading remains fixed.
a. Pitot pressure line clogged with ice or debris.
b. Defective indicator.
Vertical velocity indicator inaccurate or inopera-
tive.
a. Static line clogged.
b. Leak in line or instrument case or loose fit-
tings.
B3.
c. Defective vertical velocity indicator.
Airspeed indicator reads incorrectly or fluctuates
excessively.
a. Pitot tube or pressure line partially restrict-
ed or leaking.
b. Static port or line clogged or static line leak-
ing.
B4.
c. Faulty airspeed indicator.
Magnetic compass inaccurate, sluggish, or errat-
ic.
a. Insufficient liquid.
b. External magnetic interference.
c. Defective compass.
d. Windshield heat on.
B5.
Turn-and-slip indicator inoperative or erratic.
a. Tripped turn-and-slip circuit breaker.
b. Defective turn-and-slip instrument.
B6.
Fuel quantity indicator fluctuates or reads low.
a. Defective pins in connector on harness that
mates with gage.
3-4
