King Air C90GTi, Pilot Training Manual

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The propeller pitch is controlled by engine
o i l p r e s s u r e b o o s t e d t h r o u g h a g ove r n o r
pump integ ral within the propeller gover-
nor. Centrifugal counterweights and feath-
e r i n g s p r i n g s m ov e t h e p r o p e l l e r bl a d e s toward high pitch and into the feathered po-
sition. Without oil pressure to counteract
the counterweights and feathering springs,
the propeller blades would move into feather.
An oil pump, which is par t of the propeller
governor, boosts engine oil pressure to move
the propeller to low pitch and reverse. The
propeller feathers after engine shutdown.
Propeller tiedown boots (Figure 7-26) are
provided to prevent windmilling at zero oil
pressure when the air plane is parked.
Low pitch propeller position is determined
by the primary low pitch stop, which is a me-
chanically actuated hydraulic stop. Blade an-
gles are controlled by the power levers in the
Ground Fine and Reverse ranges.
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
7-27
FOR TRAINING PURPOSES ONLY
7
POWERPLANT
Figure 7-26. Propeller Tiedown Boot
Installed
Figure 7-25. Propellers