Propeller Owner's Manual
136
TESTING AND TROUBLESHOOTING
61-00-36
Page 4-8
Rev. 2 Feb/17
B. Engine/Propeller Speed Varies with Airspeed
(1) Small variances in engine speed are normal and are no
cause for concern.
(2) Decrease in engine speed while decreasing airspeed:
(a) Governor is not increasing oil volume in the propeller
to decrease blade pitch.
1 Internal oil leakage to opposite side of the
hydraulic piston and the propeller resists the
governor attempt to move the piston for pitch
change decrease.
2 Inadequate engine oil supply to the governor.
3 Governor oil pump pressure relief valve
not maintaining sufficient oil pressure
(275 psi minimum).
4 Blockage of oil line from the governor to the
propeller.
5 Governor pilot valve is sticking to retard
pumping of oil.
(b) Engine oil transfer system is leaking excessively.
1 Normal governor oil pumping capacity is unable
to overcome the excessive leakage to decrease
blade pitch.
(c) Excessive friction in propeller blade bearings or
pitch changing mechanism is not permitting a
decrease of blade pitch.
(3) Increase in engine speed while increasing airspeed:
(a) Governor is not decreasing oil volume in the
propeller to increase blade pitch.
1 Blockage of the oil line from the governor to the
propeller.
2 Governor pilot valve is sticking to retard oil drain
(b) Excessive friction in propeller blade bearings or pitch
changing mechanism is not permitting an increase
of blade pitch.