Textron Aviation Cessna 172S NAV III Skyhawk SP, Information Manual

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SECTION 7 CESSNA
AIRPLANE AND SYSTEM DESCRIPTION MODEL 172S NAV III
KAP 140 AUTOPILOT
U.S.
PITOT-STATIC SYSTEM AND INSTRUMENTS
The pitot-static system uses a heated total pressure (pitot) head
mounted on the lower surface of the left wing, external static port
mounted on the left side of the forward fuselage and associated
plumbing to connect the air data computer and the conventional pitot-
static instruments to the sources.
The heated pitot system uses an electrical heating element built in the
body of the pitot head. The PITOT HEAT control switch is found on the
switch panel below the lower left corner of the PFD. The PITOT HEAT
circuit breaker is found on the circuit breaker panel at the lower left side
of the pilot panel.
A static pressure alternate source valve (ALT STATIC AIR) is located
adjacent to the throttle control. The ALT STATIC AIR valve provides
static pressure from inside the cabin if the external static pressure
source becomes blocked.
If erroneous instrument readings are suspected due to water or ice in
the pressure line going to the standard external static pressure source,
the alternate static source valve should be pulled on.
Pressures within the cabin will vary with open heaters/vents and
windows. Refer to Section 5, Figure 5-1 (Sheet 2), for the Airspeed
Calibration, Alternate Static Source correction chart.
172SPHAUS-05
7-64
For
Training
Purposes
Only