THRUSH AIRCRAFT, INC – MODEL S2R-R1340
AIRCRAFT MAINTENANCE MANUAL
4-18
Effective: 01/01/2008
PROPELLER GOVERNOR
The propeller constant speed control unit
(see Figure 4-7) is an engine-driven
governor of the flyweight type. It
incorporated a gear pump that takes oil
at engine supply pressure and boosts it
to the pressure required for propeller
operation, a pilot valve actuate by the
flyweights that controls the output oil
flow, and the speeder spring by means of
which the initial load on the pilot valve
can be changed ( through the governor
controls arrangement). The required
balance between the oil force in the
cylinder and the centrifugal force of the
propeller counterweights is maintained
by the governor which either meters to,
or allows oil to drain from the propeller
cylinder in the quantity necessary to
maintain the proper blade angle for
constant speed operation. The RPM at
which the propeller will operate is
adjusted in the governor head. The
operator can change this setting by
changing the position of the governor
rack through the governor cockpit
control. As the rack is lowered, the
compression in the speeder spring is
increased. This means the engine speed
necessary to maintain a balanced
relationship between the centrifugal force
of the flyweights and the speeder spring
lowers the RPM necessary to maintain
this balance, and lowering the rack
increases the RPM setting. The position
of the pilot valve with respect to the
propeller-governor metering port
regulates the quantity of oil which will
flow through this port to or from the
propeller.
PROPELLER GOVERNOR REMOVAL
To remove the propeller governor,
position workstand and proceed as
follows:
A. Disconnect control rod from governor
quadrant.
B. Remove the four governor mounting
nuts and washers.
C. Lift governor and gasket from
engine.
D. Install cover on governor mounting
pad.
PROPELLER GOVERNOR
INSTALLATION
To install propeller governor, position
workstand and proceed as follows:
E. Remove governor mounting pad
cover.
F. Install new gasket over mounting
pad studs. Do not use sealing
compounds.
G. Place governor over mounting studs.
Align governor and engine drive
splines. Install nuts and washers,
and torque to 20 foot-pounds.
H. Connect control rod to governor
quadrant.
Figure 4-7: Propeller Governor
PROPELLER GROUND TEST
Start the engine in the normal manner
with the cockpit propeller control in the
full low RPM (high pitch) position. With
the governor set in this positive high pitch
position, the propeller will operate as a
fixed pitch propeller and the engine will
be controlled by the throttle only. As
