Airspeed Indicator; Airspeed Tubes And Indicator Troubleshooting - Piper PA-24 Comanche Service Manual

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PIPER COMANCHE SERVICE MANUAL
11038. Airspeed Indicator.
11-39 Genen.l. The ..inpeed indicator provides a means of indicatinl the speed of the aitl'lanc passin,
through the air. The airspeed indication is the differential preuure rcadi", bftwftn rieot air pressure and
stanc air pressure. This instrUment has the diaphrapn vented to the pitoe air sollrce and the cue is vemed
to the static: air system. As the airplane inC"l'CUCS speed. the pitot air pressure increases. eausin, the
diaphragm to txrand. A mechania.l linkage picks up this motion and moves the instrUment pointer to the
Indicated speed. The instrument dial is calibrated in knou and miles pet' hour. and also has the neceaary
operating range markinp for safe operation of the airplane.
11.....0.
Removal And Replacement. Refer to Parqraph 11·18 of this section.
11..... 1. Troublcshooanl'
TABLE XI·V]. AIRSPEED TUBES AND INDICATOR
Trouble
<:aUM
Remedy
Tube does not heat or Circuit breaker popped.
Reset.
clear itself of icc with
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switch "ON". (Heated
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PltOt tubes onlv.)
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Tube docs not heat or
Open circuit. Repair.
clear itself of ice with
switch "ON". (Heated
?ltOt tubes onlv.)
Excessive VOltage drop
Check voltage at pitot
between banery and head.
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pitot head.
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Hea~in,
clement bllmcd out.
Replace pitot head.
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Poin"',
0'
"or" in.",,'
Leak in instrUment case or Check for leak and
SC:t.1.
menu do not Indicate in. piece lines.
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properlv.
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POinter of instrument
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Leak In instrument cue.
Check for leak and
seal,
oscillates.
INSTRUMENTS
ISSUED: 8/18/72
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