Propeller Owner's Manual
136
DESCRIPTION AND OPERATION
61-00-36
Page 2-17
Rev. 2 Feb/17
2. Pilot Operation of Propeller Blade Angle in Beta Range
(Low Pitch to Full Reverse Pitch) for Maneuvering
A. The blade angle selection is manually controlled by the pilot.
B. First, decrease throttle to idle to decrease RPM below
900 RPM to disengage the centrifugal locks in the low pitch
stop unit.
C. Second, the pilot must select maximum RPM on the
governor control.
D. Third, the pilot moves the pilot control cockpit lever past
the catch or detent into beta range. The pilot control is
connected to the plunger in the pressure control unit to
compress the pressure control spring and increase the oil
pressure supply to the propeller Refer to Figure 2-2.
E. Fourth, decrease blade angle to approximately neutral thrust,
i.e., no forward or reverse sensation in the aircraft.
F. Fifth, increase throttle (for power) to an RPM that is clearly
under the maximum RPM selected for governor control.
In this manner the pilot will be able to move only the pilot
control cockpit lever freely to higher positive pitch (lower oil
pressure) still less than low pitch or back through neutral
pitch and into reverse pitch (higher oil pressure). This
procedure will permit simple one lever control without fear of
an overspeed.
WARNING:
PROPELLER OVERSPEED WHILE IN
BETA RANGE WILL CAUSE SUDDEN AND
UNWANTED BLADE ANGLE MOVEMENT
THAT IS CONTROLLED BY THE
GOVERNOR AND NOT THE PILOT.
(1) Too much power selected when moving through neutral
pitch with the pilot control could cause an unwanted
overspeed that will prompt the governor to suddenly
drop oil pressure (drain oil) and move the propeller to a
blade angle higher than low pitch.
(a) If this occurs the RPM will probably be higher than
900 RPM and the centrifugal locks will re-engage a
groove in the barrel of the hub and prevent reversal
even if the pilot control cockpit lever is quickly
moved toward a reverse pitch (thrust) selection.
