Piper Comanche PA-24 Service Manual page 811

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PIPER COMANCHE SERVICE MANUAL
1 H8. Ainpecd Indicuor.
11·39 General. The airspeed indicator provides a means of indicann. the speed of the airplane pusin,
chrou,h the air. The ainl'eed Indication is the differential pressure readinl between ricot air pressure and
static air pressure. This Insaumeftt has the diaphragm vented to the pitot
air
source and the cue is vented
to the stacc air system. As the airplane innases '1peed. the pirot air pressure increun.
auSltl!J
the
diaphngm to eXl"and. A mechanical linkqe
~icks
up this motion and moves the instrUment rOlnter to the
indlca.ted speed. The instrument dial is calibrated in knou and miles per hour. and
also
hu the ncccssar'"
Ol'ftating
ranlc markinp
for safe operation
of
the a.irpLane.
1140 Remo'" And Replacement. Ref." to
P.ragra~h
IH8 of this section.
11-41. Troublcshootinl.
Trouble
Tube does not heat or
dear iaclf of ice with
switch ·'01'1·' (Heated
pitOf
rubn only.)
Tube docs
nOf
heat or
clear itself of icc "Nith
SWitch ·'ON" (Heated
pi tOt rubcs only)
POinten of static instrU-
menu do not indicate
!,ro!,crly
I
POinter of Instnlment
osclllatC5.
INSTRUMENTS
ISSUED: BI1Sn2
TABLE XI-VI. AIRSPEED TUBES AND INDICATOR
Cause
Remedy
Cimm bro&ker popped. Resot.
Open cirCUit.
Repair.
Exccssive volt~c drop Check voltage at pUOt
between battery and head.
?itot head.
Hea~lng
eleme:tt burned
OUt.
Replace pitot head.
LC2.k in insmlment case or Check for leak and se.ll
in. picot lincs.
Leak in inStrument case. C!'1eck for leak and seal
3
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