9.2-7 AIRPLANE & SYSTEMS DESCRIPTIONS
PROPELLER
For water operations, it may be undesirable to feather the propeller when
the engine is stopped after landing the aircraft. If the engine is subsequently
started with the propeller in the feathered position, residual thrust
complicates docking and handling of the aircraft.
To prevent feathering the propeller, as during normal engine shutdown, this
propeller incorporates spring-energized latch pins, called auto high pitch stop
units. Two units are installed on the propeller cylinder. When the propeller
RPM is approximately 800 or above, centrifugal force disengages the latch
pins from the piston allowing it to move as needed between the reverse and
feather stops. When the RPM falls below this value, a spring in each auto
high pitch stop unit overcomes the centrifugal force on the latch pin, causing
it to retract into the cylinder and engage the piston, preventing it from moving
in the feather direction. To engage the stop units upon engine shutdown,
the power control must be placed into the reverse thrust position before
stopping the engine. Upon stopping, a large spring in the propeller moves it
toward the feathered position, but as the RPM decays below approximately
800, the retracted latch pins engage the piston, preventing the propeller from
feathering.
Upon starting the engine, the propeller is already in at pitch. What little
thrust is generated while starting the engine does not present a handling
problem for the aircraft. To disengage the latches before taxi and ight, the
power lever must be placed momentarily in the reverse thrust position while
at low power. This removes the lateral friction force from the latch pins and
prevents them from being damaged by application of power. After adding
sufcient power to advance the RPM above 800, the latch pins move to an
outward position and remain there, allowing full control of the propeller.
Other than the operations utilizing the pitch latch pins, the propeller operates
identically to the standard HC-E4N-3P / D9511FSB propeller. Consult the
basic Pilot’s Operating Handbook and FAA Approved Airplane Flight Manual
for a brief description of the propeller’s functional characteristics.
9.2-8 HANDLING, SERVICE & MAINTENANCE
Refer to Hartzell Manual No. 149 “Propeller Owner’s Manual” for general
maintenance applicable to this propeller.
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