Piper COMANCHE PA-24-180 Service Manual page 658

PIPER COMANCHE SERVICE MANUAL
the short pointer in ten thousand feet. A field pressure window is located on the right side of the indicator
dil and is set by the knob located on the lower left corner of the instrument. The altimeter consiss of a
sealed diaphragm that is connected co the pointers through a mechanical linkage. The insrument cse is
vented to the stic air sstem and as stic air pressure decreases the diaphragm expands causng the
pointers to move through the mechanical linkage.
The rate )f climb indicator measures the rate of change in saric presure when the airplane is climbing
or descending. By means of a pointer and dial. this instrument will indicate the rate of ascent or descent of
the airplane in feet per minute.
11-5. Eletrical Instrumen. The urn and bank indicator is an elecrcal
instrument used for making
correctly controlled urns. The turn portion of the indicator is an electrically driven gyroscope. while the
bank portion is a ball sealed in a curved glas tube filled with dampening fluid. The electrical switch for the
turn and bank indicator is located on the switch panel under the left instrument panel.
The ammeter i mounted in the mrument cluster located on the intrument panel. This insmr
ent
meaures the amount of current received and the amount of current drain on the battery.
Two fuel quantirv gauges are used on the Comanche (PA-4-1SO, Serial Nos. 24-1 and up, and
PA-24-250, Serial Nos. 24-1 to 24-2843 inclusive) and are mounted in the cluster on the instrument panel.
These instruments are calibrated
in
fractional divisions of one fourth, one half. three fourths and full. A
transminer unit is installed in each fuel cell. This unit contains a resstance srip and a movable control arm.
The position of this arm is controlled by a float in the fuel cell and this position is transmitted electricall
to the indicator gauge to show the amount of fuel in the cell. If the luxiliary fuel system is installed. two
auxiliary fuel quantitn gauges will be installed in the instrlment cluster.
In the Comanche. PA-24-250. Serial Nos. 24-2844 and up. PA-24-260. and PA-24400. only one fuel
quantity gauge is incorporated m the system. This gauge will indicate the amount of fuel in the cell that s
selected. This arrangement is made possible by a selector switch mounted on the fuel selector valve. The
witch is located directly below the fuel selector place. An overnde system s incorporated so that it is
possible to check the amount of fuel available in the remaining cells without moving the selector handle to
that cell position. This accomplished by depressing the red bu..on (located on the fuel selector plate) under
the desired fuel cell position. The fuel gauge will indicate the amount of fuel available n that cell. When the
red burton is released the indicanng system wil return to its normal operation of mdicating the amount of
fuel in the tank selected.
The oil temverature indicator is mounted in the insrument cluster on the insrument
panel. This
instrument will provide a temperature indication of the engine oil in degrees Fahrenheit. The insrument
has a temperature bulb located in the oil screen assembly on the engine accessory section.
11-6. Miscellaneous Instrument. The magnetic compass installed in the Comanche is a self-contained
instrument and is mounted above the instrument panel on the windshield center strip. This instrument has
an individual light which is connected to the instrument lighting circuit. The compass correction card is
located in the card holder mounted on the instrument panel.
The clock is a hand wound. 8-day nme piece. It incorporates a stem wind with the knob at the lower
left-hand side of the dial. This knob, when pulled and turned. also adjusts the hands. In addition, two
dummy hands are controlled by a center knob and they function as elapsed time hands.
The tachometer is connected to the engine accessory section by a flexible cable, and provides an
indication of crankshaft speed in revolutions per minute. The instrument has a recording mechanism for
recording the time that the engine is in actual operation.
INSTRUMENTS
ISSUED: 8/18/72
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