Propeller Owner's Manual
115N
DESCRIPTION AND OPERATION
61-00-15
Page 2-3
Rev. 24 Dec/20
1. Description of Propeller and Systems
A. System Overview
(1) The propellers covered in this manual are constant speed,
single-acting, hydraulically actuated propellers. Some of
the propellers have feathering capability. These propellers
are designed primarily for use with reciprocating engines,
but there are some turbine applications.
(2) A constant speed propeller system is controlled by an
engine speed sensing device (governor) to maintain a
constant engine/propeller RPM by changing blade angle.
(3) The governor uses an internal pump that is driven by
the engine. This pump increases engine oil pressure for
supply to the propeller. Engine speed sensing hardware
within the governor controls the supply of oil to the
propeller, supplying or draining oil as appropriate to
maintain constant engine speed.
(4) Propeller blade angle change is accomplished via 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
pitch change rod and a fork. A pitch change knob, located
at the base of each blade, is in contact with the fork. Each
blade root is supported in the hub by a retention bearing.
The retention bearing holds the blade firmly in the hub, but
also allows the blade angle to change.
(5) Propeller forces, consisting of: 1) mechanical spring
action, 2) cylinder air charge, 3) counterweights, 4) and
centrifugal twisting moment on the blades, in a variety of
combinations, are constantly present while the propeller
is operating. The summation of these forces is opposed
by a variable hydraulic force (oil pressure from the
engine driven governor). Oil pressure is metered by the
governor to oppose this constant force. The propeller
forces, opposed by the variable hydraulic force cause the
propeller blade angle to increase, decrease, or maintain
current setting.
