Propeller Owner’s Manual
147
TESTING AND TROUBLESHOOTING
61-00-47
Page 4-5
Rev. 6 May/20
(b) Hunting and/or surging may also be caused by
friction or binding within the governor control, or
internal propeller corrosion, which causes the
propeller to react slower to governor commands.
1
To isolate these faults, the propeller must be
tested on a test bench at a certified propeller
repair station with the appropriate rating.
B. Engine Speed Varies with Airspeed
(1) Constant speed propeller models will experience some
small variances in engine speed that are normal and are
no cause for concern.
(2) Increase in engine speed while descending or increasing
airspeed:
(a) Governor is not reducing oil volume in the propeller.
(b) Friction in propeller.
(3) Decrease in engine speed while increasing airspeed:
(a) Governor pilot valve is stuck and is excessively
decreasing oil volume.
(b) Feathering command engaged on propeller pitch
control.
(4) Increase in engine speed while decreasing airspeed:
(a) Governor pilot valve is stuck and is excessively
increasing oil volume.
(5) Decrease in engine speed while decreasing airspeed:
(a) Governor is not increasing oil volume in the propeller.
(b) Engine oil transfer system leaking excessively.
(c) Friction in propeller.
