Cessna 182T 2001, Pilot Operating Handbook

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CESSNA SECTION 7
MODEL 182T AIRPLANE & SYSTEMS DESCRIPTION
The heated pitot system consists of a heating element in the pitot
tube, a 10-amp switch/breaker labeled PITOT HEAT, and associated
wiring. The switch/breaker is located on the lower left side of the
instrument panel. When the pitot heat switch is turned on, the
element in the pitot tube is heated electrically to maintain proper
operation in possible icing conditions.
A static pressure alternate source valve is installed above the
throttle, and can be used if the external static source is
malfunctioning. This valve supplies static pressure from inside the
cabin instead of the external static port.
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 heater/vents and
windows. Refer to Section 5 for the configuration applicable to the
use of the alternate static source and the correction charts.
AIRSPEED INDICATOR
The airspeed indicator is calibrated in knots and miles per hour.
It incorporates an internal, rotatable ring which allows true airspeed
to be read off the face of the dial. In addition, the indicator
incorporates windows at the seven and twelve o’clock positions. The
window at the seven o’clock position displays true airspeed, and the
window at the twelve o’clock position displays pressure altitude
overlayed with a temperature scale.
Limitation and range markings (in KIAS) include the white arc (41
to 100 knots), green arc (51 to 140 knots), yellow arc (140 to 175
knots), and a red line (175 knots).
To find true airspeed, first determine pressure altitude and
outside air temperature. Using this data, rotate the lower left knob
until pressure altitude aligns with outside air temperature in the
twelve o’clock window. True airspeed (corrected for pressure and
temperature) can now be read in the seven o’clock window. For
maximum accuracy the true airspeed should be read opposite the
calibrated airspeed value.
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