Propeller - Cirrus SR20 Pilot Operating Handbook

Section 7 Cirrus Design
Airplane and Systems Description SR20

Propeller

The airplane is equipped with a constant-speed, aluminum-alloy
propeller with a governor. The airplane is available with the standard
two-blade (76" diameter) propeller or an optional three-blade (74"
diameter) propeller.
The propeller governor automatically adjusts propeller pitch to
regulate propeller and engine RPM. The propeller governor senses
engine speed by means of flyweights and senses throttle setting
through a cable connected to the power (throttle) control lever in the
cockpit. The propeller governor boosts oil pressure in order to regulate
propeller pitch position. Moving the throttle lever forward causes the
governor to meter less high-pressure oil to the propeller hub allowing
centrifugal force acting on the blades to lower the propeller pitch for
higher RPM operation. Reducing the power (throttle) lever position
causes the governor to meter more high-pressure oil to the propeller
hub forcing the blades to a higher pitch, lower RPM, position. During
stabilized flight, the governor automatically adjusts propeller pitch in
order to maintain an RPM setting (throttle position). Any change in
airspeed or load on the propeller results in a change in propeller pitch.
7-42 P/N 21399-004
Revision A1