Aircraft Alternator Trouble

Alternator (p/n ASG120003RX) failed to charge during cross-country flight. Alternator cooling fan came apart in flight. Front engine charging system was intermittent, then constant alternator inoperative light was observed. The right engine locked up in flight, going into feather, and could not be restarted.

Editorial Staff

Thursday, February 18, 2016 at 12:00 AM ET

Verified

Key Takeaways:

Multiple aircraft experienced alternator failures stemming from a variety of mechanical and electrical issues.
Reported failure modes included separated case halves, cracked cooling fans, loose securing bolts, sheared drive shafts, high electrical resistance, and frozen units.
Consequences ranged from loss of charging and inoperative warnings to severe engine damage, leading to unscheduled landings.
These incidents occurred across different Cessna, Cirrus, and Piper models, often at relatively low part total times.

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Cessna 182T
Separated Case Halves

Alternator (p/n ASG120003RX) failed to charge during cross-country flight. Inspection revealed separation of alternator case halves. Through bolts held component intact but resulted in loose or sloppy tolerance on drive shaft main bearing and failure to produce current.

Part total time: 1373.0 hours

Cessna 210M
Cracked Cooling Fan

Alternator cooling fan came apart in flight. Portion of cooling fan punched a hole in induction air box downstream of air filter and the alternator belt came loose. Loss of power from engine damage resulted in an unscheduled landing. The cooling fan had cracked at a spot weld.

Part total time: 193.0 hours

Cessna 337G
Loose Bolts

Front engine charging system was intermittent, then constant alternator inoperative light was observed. Three bolts holding the alternator (p/n 633962) together were found loose despite factory safety wire being secure and untouched. Disassembly of unit showed frame had worked loose, allowing the stator to contact the rotor. The main wires had separated.

Part total time: 138.0 hours

Cessna 340A
Sheared Alternator Drive Shaft

The right engine locked up in flight, going into feather, and could not be restarted. The alternator (Prestolite p/n ALV9510) shaft had sheared off flush with the alternator inner bearing, causing the coupler and the input portion of the rotor shaft to drop into the engine, causing significant damage.

Part total time: Unknown

Cirrus SR20
High Resistance

Pilots reported the #2 alternator inoperative with associated warning message. Troubleshooting revealed high resistance of its field circuit when rotated; it seemed acceptable when static. Performed full field check of alternator and it was still inoperative. Alternator was replaced with serviceable unit.

Part total time: 263.0 hours

Piper PA-44-180
Frozen

Alternator inoperative annunciator illuminated in flight. Reset attempt failed and aircraft landed without incident. Right alternator (Kelly p/n ALX8521LS) was found frozen and its drive belt almost completely worn through.