Propeller Owner's Manual
136
DESCRIPTION AND OPERATION
61-00-36
Page 2-10
Rev. 2 Feb/17
(d) For pressure control, the pressure control unit
uses a pressure limiting configuration consisting
of a relief valve and a pressure relief compression
spring. The addition of a plunger to permit pilot input
of a different position and load on the pressure
relief compression spring, permits different/variable
oil pressure output selection during beta range
operation.
C. Propeller Governed Operation - Refer to Figure 2-2 and
Figure 2-3
(1) In flight the propeller is controlled by an engine speed
sensing device (governor) to maintain a constant engine/
propeller RPM by changing blade angle through the
supply or drain of oil through a hallow engine shaft to the
hydraulic piston of the propeller. The linear motion of the
hydraulic piston is transmitted to each blade through a
pitch change rod and an attached fork that engages a
pitch change knob on each blade. Each blade is supported
and retained by the hub at its root by a blade retention
bearing that permits the blade to rotate for pitch change
during propeller rotation.
(2) The governor uses an internal pump that is driven by
the engine through an accessory drive location. The
governor pump increases engine oil pressure for supply
to the propeller. Engine speed sensing hardware within
the governor controls the supply of oil to or the drain of oil
from the propeller as appropriate to change blade angle
to maintain constant engine speed (RPM). Increasing
the volume of oil within the hydraulic piston and cylinder
will decrease blade angle and increase propeller RPM.
Decreasing the volume of oil within the hydraulic piston
and cylinder will increase blade angle and decrease
propeller RPM. By changing the blade angle, the governor
can vary the load on the engine and maintain constant
engine/propeller RPM.