Pitot Heat Switch - Cirrus SR20 Pilot Operating Handbook

Cirrus Design
SR20
Pitot-Static System
The Pitot-Static system consists of a single heated Pitot tube mounted
on the left wing and dual static ports mounted in the fuselage. The
Pitot heat is pilot controlled through a panel-mounted switch. An
internally mounted alternate static pressure source provides backup
static pressure should that the primary static source becomes blocked.
Water traps with drains, under the floor in the cabin, are installed at
each Pitot and static line low point to collect any moisture that enters
the system. The traps should be drained at the annual inspection and
when water in the system is known or suspected.

Pitot Heat Switch

The heated Pitot system consists of a heating element in the Pitot
tube, a rocker switch labeled PITOT HEAT, and associated wiring. The
switch and circuit breaker are located on the left side of the switch and
control 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. The Pitot heat system operates on 28 VDC
supplied through the 7.5-amp PITOT HEAT circuit breaker on the
NON-ESSENTIAL BUS.
Pitot Heat Annunciation
Illumination of the PITOT HEAT FAIL Caution indicates that the Pitot
Heat switch is ON and the Pitot heater is not receiving electrical
current. Illumination of PITOT HEAT REQD Caution indicates the
system detects OAT is less than 41°F (5°C) and Pitot Heat Switch is
OFF. A current sensor on the Pitot heater power supply wire provides
current sensing.
Alternate Static Source
An alternate static pressure source valve is installed on the switch and
control panel to the right of the pilot's leg. 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 turned on. Pressures within
the cabin will vary with open heater/vents. Whenever the alternate
static pressure source is selected, refer to
Data for airspeed calibration and altitude corrections to be applied.
P/N 21399-004 P/N 21399-004
Revision A1
Airplane and Systems Description
Section 5: Performance
Section 7
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