Cirrus SR22 Pilot Operating Handbook page 439

Cirrus Design Section 9
SR22 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%.
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 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.
Ice-Inspection Lights
To provide visual verification of icing conditions and confirmation of
fluid flow, ice inspection lights are flush mounted to the RH and LH
fuselage skin just aft of the engine cowling. The bi-directional
P/N 13772-150 47 of 50
Original Issue: 02-01-13