EN-1320
OPERATION AND INSTALLATION MANUAL
8.4. Rpm variations between ascend, cruise and descent although having identical propeller
setting
Up to
±
50 rpm normal condition. If more :
Cause:
1. Excessive friction in the propeller
2. Excessive friction in the governor
3. Defect tachometer
Remedy: 1. Contact manufacturer.
2. Contact manufacturer.
3. Replace/repair instrument.
8.5. Rpm decrease during normal operation without change of propeller lever position
Cause:
1. Oil leakage or hot oil
2. Worn oil transfer system causes a increase in blade angle of attack
3. Failure of governor speeder spring
4. Governor drive failure
Remedy:
1. Check for oil leaks, replace gaskets, decrease oil temperature with higher
aispeeds.
2. If the system works with cold oil and fails at high oil temperature, this will indicate
high leakage in the oil transfer system on the propeller shaft. Repair turbine.
3. Contact manufacturer.
4. Check governor drive and governor on the test bench.
8.6. Rpm increase during normal operation without change of propeller lever position
Cause:
1. Sticking pilot valve in governor
2. Control inoperative or broken
Remedy: 1. Check governor on the test bench
2. Check free movement, connection and positive stop contact.
8.7. Extremely slow pitch change or no pitch change on ground
(rpm changes with airspeed like a fixed pitch propeller)
Cause:
1. Blocked oil line
2. Sludge deposit in propeller piston
3. Damaged pitch change mechanism
4. Corrosion in the blade bearings
Remedy: 1. Check turbine
2. Clean propeller and crankshaft
Concerning 1 and 2 :
This behavior does not appear at once and gets worse after some time. It should be
observed at the preflight check.
3. Contact manufacturer.
This error may appear suddenly.
4. Repair propeller.
61-10-20
TROUBLESHOOTING
Page 8-2
2017-10-06
