Hartzell HC-82XF-1 Owner's Manual page 69

Propeller Owner's Manual
175
The lowest blade angle attainable by the governor is low
pitch. An external valve and internal valve hydraulically
control the low pitch stop and the blade angles between
low pitch and reverse. Beta refers to the blade angle range
between low pitch and full reverse blade angles.
In reverse mode of operation, the governor supplies oil,
to the reversing valve. In this mode, the pilot input to the
external reversing valve (through cockpit controls) will select
full reverse blade angle or low pitch blade angle (governing
mode).
Fundamental elements of this reversing system include
an external reversing valve, cockpit control cable (to the
reversing valve), internal valve (mounted inside the engine
shaft, interfacing internally with the propeller) and hydraulic
lines to connect between the governor, external valve, and
engine. Refer to Figure 2-10.
The propeller blade angle must be positioned at the low
pitch hydraulic stop, and the governor should be onspeed or
underspeeding to permit reverse blade angle selection.
Propeller blade angle is moved into the beta range by
manually repositioning the cockpit control to move the lever
on the external valve and move the valve spool to supply
oil from the governor pump to the propeller. If this lever/
cockpit control position is activated, the propeller blade
angle will move to full reverse. Propeller blade angle is
moved to low pitch blade angle by repositioning the cockpit
control to a position opposite that used to select reverse
blade angle. This will move a lever on the external valve to
position a valve spool, permitting propeller oil to drain from
the propeller to the engine sump and increase to low pitch.
The cockpit control must remain in this position for normal
governor control of blade angle above low pitch blade angle
and to prevent unwanted movement of blade angle below
the hydraulic low pitch stop.
NOTE: This reversing system will only select low pitch blade
angle or full reverse blade angle. Selection of intermediate
blade angles is not possible, as with other reversing
systems.
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DESCRIPTION AND OPERATION
Dec/05