OPERATION AND INSTALLATION MANUAL
EN-1320
c) Underspeed
Refer to figure 12-1C. The centrifugal force acting on the flyweights is lower than the speeder spring force.
The flyweights tilt inward and lower the pilot valve. The pilot valve opens low pitch channel to high pressure
channel, blades moves to lower pitch and RPM goes up to onspeed condition.
With governor LUN7816, the pressure at low pressure side of servomechanism must be high enough to
exceed pressure of 0,6 MPa (87 psi) at high pitch side of the servomechanism and all other forces.
Figure 12-1 Propeller governor function
C. Beta mode of operation
Beta mode of operation is used to decrease propeller thrust at taxiing or to set negative thrust after landing.
It allows to set any position between minimum flight pitch and maximum reverse at control of engine power
simultaneously.
For the propeller governors LUN 7815.01 and .02, the engine power increases up to maximum reverse
power depending on the blade position and the propeller model.
For the propeller governor LUN 7815.03, the engine power remains engine power at idle up to maximum
reverse angle.
Beta control is realized by pilot using the engine condition lever. Pilot valve is out of operation at beta
control. Blade position is controlled by coaxial valve, which controls oil flow to the propeller. The outer
valve, which determines requested position, is controlled by engine condition lever behind idle stop. The
inner valve is turned from beta-ring feedback. The feedback also switches on the cockpit beta lamp.
When the blades are in required position, no oil flows through the coaxial valve (figure 12-2A).
LUN 7815
LUN 7816
A
B
C
61-10-20
PROPELLER CONTROL SYSTEM
(Installation With Jihostroj LUN-Series Governor)
Page 12-2
2017-10-06
