Page 2-21
Dec/05
DESCRIPTION AND OPERATION
61-00-75
Propeller Owner's Manual
175
D. Constant Speed, Feathering and Reversing Propellers
(Internal Beta System)
Propeller models HC-83(X,V)F-3( )( ) Refer to Figure 2-9.
A constant speed, feathering and reversing propeller is
typically used on a twin engine aircraft. It is counterweighted
and uses internal and external reversing control hardware.
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 a link arm 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 forces of the installed spring and counterweight attempt
to rotate the blades to a higher blade angle.
The counterweight is a weight that is attached to each blade
clamp to cause the blade to rotate to a higher blade angle.
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.
Oil is metered by the governor to oppose these constant
forces and maintain a constant engine RPM.
OBSOLETE PROPELLER MODELS. SEE COVER PAGE
WARNINGS AND SERVICE BULLETIN HC-SB-61-331
