Propeller Owner’s Manual
139
TESTING AND TROUBLESHOOTING
61-00-39
Page 4-5
Rev. 17 Apr/20
(b) Hunting and/or surging may also be caused by
friction or binding within the governor control, o
r
i
nternal 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 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.
(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 propeller.
(b) Friction in propeller.
