Page 2-17
Dec/05
DESCRIPTION AND OPERATION
61-00-75
Propeller Owner's Manual
175
C. Constant Speed and Feathering Propellers
Propeller models HC-82(X,V)(F,K,L)-2( )( ),
HC-83(X,V)F-2( )( ) and HC-83(X,V)20-2( )( ).
Refer to Figures 2-7 and 2-8.
A constant speed and feathering propeller is typically used
on a twin engine aircraft. It is counterweighted, and is
controlled by an engine speed-sensing device (governor) to
maintain a constant engine/propeller RPM by changing blade
angle and varying load on the engine.
Propeller blade angle change is actuated by a hydraulic
piston/cylinder combination mounted on the forward end
of the propeller hub. The linear motion of the hydraulic
piston is transmitted to each blade through either a link arm
system, or through a sliding rod and fork system, connected
to a blade clamp that rotates with the blade. Each blade is
retained on the propeller hub by a blade clamp and thrust
bearing. The thrust bearing permits the blade to change
angle under centrifugal load.
The counterweight is a weight that is attached to each
blade clamp to cause the blade to rotate to a higher blade
pitch. Counterweighted propellers require governor supplied
oil to decrease blade pitch. If the oil supply is lost, the
counterweighted propeller will go to feather.
The weight of each propeller blade when spinning, generates
centrifugal force and a twisting force that attempts to rotate
each blade to a lower blade angle.
Air flow around the blade generates lift and an aerodynamic
twisting moment that attempts to increase or decrease blade
angle, depending on flight condition and blade design. This
force is generally very small in relation to the other forces.
Propeller forces consisting of mechanical spring action,
counterweight twisting moment, and centrifugal and
aerodynamic twisting moment of the blades in various
combinations are constantly present while the propeller
is operating. The summation of these forces causes the
propeller to rotate to a higher pitch. A variable hydraulic force
(oil under pressure from the engine driven governor) toward
a lower blade pitch opposes the summation of these forces.
OBSOLETE PROPELLER MODELS. SEE COVER PAGE
WARNINGS AND SERVICE BULLETIN HC-SB-61-331
