EN-1320
OPERATION AND INSTALLATION MANUAL
12.0. PROPELLER CONTROL SYSTEM
12.1 INTRODUCTION
A. General
The informations on function, installation, adjustment and testing of Jihostroj governors LUN7815
and/or LUN7816 are only included in this chapter. For information on other propeller governors refer to
governor manufacturer’s manual.
CAUTION:
KEEP IN MIND THAT WHEN THE RPM ARE MENTIONED ANYWHERE IN THIS CHAPTER, THIS
INFORMATION RELATES (AND IS APPLICABLE) ONLY TO 2080 RPM ENGINE.
12.2 AIRWORTHINESS LIMITATION
See the certificate delivered with governor for information on airworthiness limitations.
Contact manufacturer for additional information.
12.3 PROPELLER CONTROL
A. Oil supply
The propeller governor consists of a oil pump and control subassemblies. The oil pump supplies
pressurized oil to the propeller. It consists of a geared type pump and a relief valve that keeps the
pump outlet pressure at the required level.
B. RPM control
RPM control is keeping the propeller at a constant speed. The governor compares actual RPM with
requested RPM then varies the amount of oil pressure sent to the propeller. This pressure is used to
vary the pitch of the propeller blades to maintain the requested RPM.
Speed adjusting lever on the governor is connected through linkage with propeller condition lever in the
aircraft cockpit. Position of the adjusting lever determines loading of the speeder spring. This loading
represents RPM requested.
The governor shaft, which is driven from engine gear box and which RPM are proportional to propeller
RPM, is connected with flyweight head and both are rotating together. Centrifugal force of flyweights acts
against speeder spring. This force represents real propeller RPM.
The flyweight centrifugal force acts on pilot valve support. The force from speeder spring acts on the
second side of the support. The pilot valve support is connected with pilot valve, which controls oil flow to or
from the propeller.
There are three basic conditions for propeller governing: onspeed, overspeed and underspeed.
a) Onspeed
Refer to figure 12-1A. The centrifugal force acting on the flyweights is balanced by the speeder spring, and
the pilot valve is neither directing oil to or from the propeller servomechanism. Real propeller RPM
corresponds with setting.
b)
Overspeed
Refer to figure 12-1B. The centrifugal force acting on the flyweights is greater than the speeder spring
force. The flyweights tilt outward and raise the pilot valve. The pilot valve opens low pitch channel to
drain, blades moves to higher pitch and RPM goes down up to onspeed condition.
With governor LUN7816, high pitch side of the servomechanism is also pressurized at all the time by
0,6 MPa (87 psi) to help in pitch increasing.
61-10-20
PROPELLER CONTROL SYSTEM
(Installation With Jihostroj LUN-Series Governor)
Page 12-1
2017-10-06
