Hartzell HC-E4 3 Series Owner's Manual page 79

Propeller Owner's Manual
147
It is undesirable to feather the propeller when the engine is
stopped after landing the aircraft. This propeller type is
normally installed on a fixed shaft engine that causes the
propeller to rotate during an engine start process. If the
propeller is in feather position, an overload on the electric
engine starter will occur.
To prevent feathering during normal engine shutdown, the
propeller incorporates spring-energized latch pins, called
start locks. Two start locks are installed on the cylinder. If
propeller rotation is approximately 800 RPM or above, the
start locks disengage from the piston by centrifugal force
acting on the latch pins to compress the spring (within
the units). When RPM drops below 800 RPM, the springs
overcome the centrifugal force and move the latch pins to
engage the piston, preventing blade angle movement to
feather.
Shortly after start up with the propeller RPM above 800, the
latch pins in the start locks will still retain the blade angle.
To release the latch pins, it is necessary to manually actuate
the propeller slightly toward reverse. This will move the
piston, allowing the latch pins to slide freely. Centrifugal force
will compress the springs and disengage the pins from the
piston.
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DESCRIPTION AND OPERATION
Rev. 16 May/20