Supplement Airplane Maintenance Manual
Cessna 172 with TAE 125-02-99 / -114
AMM-20-02
Rev. No:
Rev. Date:
Chapter:
Issue:
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20-AMM-61-02
3
06.11.2013
1
6
1
25.08.2014
61
PROPELLER
61.10
CONSTANT SPEED PROPELLER
The engine is equipped with propeller MTV-6-A/187-129.
For inspections and maintenance of the propeller refer to
Operation and Installation Manual of MT-Propeller E124 (ATA
61-01-24).
The propeller pitch limits differ for the TAE 125-02-99 and TAE
125-02-114. Refer to Chapter 06.3.
61.20
CONSTANT SPEED UNIT
The propeller control system uses gearbox oil to function. The oil
pump delivers oil to the constant speed unit. Inside the constant
speed unit the oil passes through a micro filter and a pressure
relief valve where the pressure is reduced to a constant 20 bar
(290 psi) before reaching the actual control valve. The propeller
control valve regulates the oil pressure to the propeller to
regulate pitch. Returned oil from the control valve is used to
lubricate the gearbox. The propeller control valve is regulated by
an electric signal from the FADEC while the pilot has no direct
input to the propeller. The propeller itself is a conventional
variable pitch propeller, pitch is increased by increasing oil
pressure and is decreased by the blade pitching moment and a
servo spring. The next Figure shows a schematic of the propeller
control system. See Figure 1.
Figure 1 Propeller Control System
Gearbox
Pump
Micro
Filter
Relief
Valve
FADEC
Propeller
Control
Valve
Propeller
Constant Speed Unit
Summary of Contents for Cessna 172
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