Airspeed Indicator; Airspeed Tubes And Indicator Troubleshooting - Piper PA-44-180 SEMINOLE Maintenance Manual

CHART 3402. TROUBLESHOOTING (ALTIMETER) (cont)
Trouble
Altimeter changes reading
as aircraft is banked.
Altimeter requires resetting
frequently.
When any connections in the static system are opened for check, system must be
rechecked per Part FAR 23.1325.

AIRSPEED INDICATOR.

The airspeed indicator provides a means of indicating the speed of the airplane passing through the air. The
airspeed indication depends on the differential pressure between pitot air pressure and static air pressure. This
instrument has the diaphragm vented to the pitot air source and the case is vented to the static air system. As the
airplane increases speed, the pitot air pressure increases, causing the diaphragm to expand. A mechanical linkage
picks up this motion and moves the instrument pointer to the indicated speed. The instrument dial is calibrated in
knots and miles per hour, and also has the necessary operating range markings for safe operation of the airplane.
CHART 3403. TROUBLESHOOTING (AIRSPEED TUBES AND INDICATOR)
Trouble
Pointers of static instru-
ments do not indicate
properly.
Pointer of instrument
oscillates.
Instrument reads high.
Instrument reads low.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
Cause
Water in static line.
Temperature compensator
inoperative.
— Note —
Cause
Leak in instrument case or
in static lines.
Defective mechanism.
Pointer not on zero.
Leaking static system.
Pointer not on zero.
Leaking static system.
Pitot-static head not aligned
correctly.
2I23
Remedy
Remove static lines from all
instruments, and blow line
clear from cockpit to sensor.
Change instrument.
Remedy
Check for leak and seal.
Replace instrument.
Replace instrument.
Find leak and correct.
Replace instrument.
Find leak and correct.
Realign pitot-static head.
Revised: May 15, 1989
3 4 - 1 3 - 0 0
Page 34-05