Cirrus DESIGN SR22 Pilot Operating Handbook page 383

Cirrus Design Section 9
SR22 / SR22T Supplements
Stall Warning System
Stall warning is provided by the lift transducer, mounted on the leading
edge of the right wing and the stall warning computer located under
the cabin floor. The lift transducer senses the force of the airstream on
the vane, producing an electrical output to the stall warning computer.
When the stall warning set-point is reached, the stall warning
computer provides a signal to the avionics system to activate the stall
warning aural alert and CAS message. The stall warning computer
also provides the information used to generate the dynamic stall
speed awareness indication (red band) on the airspeed tape which
indicates the relative proximity to the aircraft stall speed based on the
wing loading (weight, angle of bank, etc). The stall warning computer
operates on 28 VDC supplied through the 5-amp STALL WARNING
circuit breaker on the ESS BUS 2.
Ice protection for the lift transducer is provided by two faceplate
heaters, one vane heater and one case heater using the PITOT HEAT
switch. To prevent overheating during ground operations, a signal from
the avionics is used to operate the heaters at 25% power during
ground operation or 100% power while in the air. The lift transducer
heat is powered by 28 VDC supplied through the 10-amp STALL VANE
HEAT circuit breaker on the NON-ESS BUS.
The stall warning computer receives an signal from the avionics
system to reduce nuisance stall warning while the aircraft is on the
ground. The stall warning is inhibited when ground speed is less than
30 knots or airspeed is less than 55 KIAS. To allow a preflight check of
the system, stall warning is enabled if RPM is less than 500 and flaps
are set to 100%.
Serials 22-3403 thru 22-3642 before Service Bulletin SB 2X-27-09: An
additional stall warning margin is added to the aircraft beyond the
required 5 KIAS to account for ice contamination on unprotected
surfaces. Although this ensures the required margin is maintained
during/after an icing encounter, it may be excessive when the aircraft
is not contaminated by ice shapes.
Serials 22-3643 & subs, 22T-0001 & subs, and Serials 22-3403 thru
22-3642 after Service Bulletin SB 2X-27-09: An IPS-ON discrete
signal is sent to the stall warning computer when the ice protection
system is set to ON. This adds additional stall warning margin to the
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Revision 05: 09-20-12