The following information is derived from the FAA's Service Difficulty Reports and Aviation Maintenance Alerts.


Beech H35 Bonanza

Improper Mounting

The alternator suffered a total mechanical failure after only 144.7 hours. The replacement unit failed after only 41.8 hours in service. Observation suggests the alternator case hardware was not properly torqued and/or was not assembled with locking fluid. Each failure found the aircraft in near-IMC conditions.

Part total time: 41.8 hours

Cessna 182T Skylane

Case Separation

Alternator failed to charge during cross-country flight. Inspection shows separation of alternator case halves, resulting in sloppy tolerance on drive shaft main bearing and failure to produce current.

Part total time: 1373.0 hours

Cirrus SR20

Unknown Failure

While airborne, the #2 alternator (p/n 653344) was inoperative. Investigation discovered the alternator’s field was open. During replacement, maintenance noted the cooling fan was covered with a dusting of copper-colored particles, which could be from the brush slip rings.

Part total time: 286.0 hours

Mooney M20J 201

Field Circuit

Alternator’s five-amp field circuit breaker popped. Investigation revealed the voltage regulator had shorted internally and the field circuit breaker was fried. Run-up seemed normal until applying a full complement of electrical loads, when the field circuit breaker tripped and fried another regulator. Discovered alternator had no output. It appears failure of the new alternator caused failure of voltage regulator. Voltage regulator does not seem to be protected by five-amp field circuit breaker.

Part total time: 31.0 hours

Piper PA-28-181 Archer II/III

Seized Alternator

The aircraft was in the traffic pattern when pilots noted the alternator was no longer charging, accompanied by a strong burning odor in the cabin. Inspection found the alternator had seized, causing the alternator belt to overheat and melt.

Part total time: Unknown

Piper PA-34-200 Seneca

Internal Short

Left alternator failed in flight, with smoke coming from the cowling. Inspection revealed the alternator would not rotate when turning the propeller. After removal, further inspection revealed that a fairly large piece (approximately one-inch square) of the rotating assembly had broken off and was still in the alternator, preventing rotation. Damage to the associated wiring was also noted.

Part total time: Unknown


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