Alternators

Editorial Staff

Thursday, March 23, 2023 at 01:34 PM ET

Verified

Key Takeaways:

Aircraft alternators fail due to a variety of issues, including internal component breakdowns (e.g., stator, rectifier, rotating assembly), mechanical problems (e.g., loose bolts, seizing), and electrical connection faults (e.g., cracked solder joints, broken terminals).
These failures manifest as intermittent charging, low voltage output, or complete loss of electrical power, often leading to system malfunctions, manual operations (e.g., gear extension), and hazards such as arcing, smoke, or burning odors.
Several reported incidents indicate premature alternator failures occurring at relatively low operating hours, suggesting potential for manufacturing defects or early wear in critical components.

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Beechcraft A36 Bonanza

Stator And Rectifier Failure

During descent, electric power was lost. Selected standby alternator. Unable to extend gear electrically; manually extended gear and landed uneventfully. Removed alternator (p/n 649304). Repair station replaced the stator and rectifier.

Part total time: Unknown

Beechcraft 58 Baron

Cracked Solder Joint

Pilot reported left alternator was intermittent (indicator light was flashing). Inspection revealed a cracked solder joint on the alternator at the base of the A+ output terminal.

Part total time: 41.0 hours

Cessna 172N Skyhawk

Broken Power Terminal

In cruise, the alternator dropped off line. Switch and circuit breaker checked okay. Crew experienced intermittent flap, radio and light failures. Investigation revealed the power terminal had snapped off and was arcing to the alternator. The battery was drained beyond recovery and was replaced with new. The alternator was replaced and alternator wiring repaired as required.

Part total time: Unknown

Cessna T210L Turbo Centurion

Low Voltage Output

Voltmeter indicated a discharge at 1000 rpm. Normal voltage should be 28.5+-0.5. Voltmeter indicated 25.0 @ 1000 rpm, with 37 amps. At 1700 rpm, 27.8v, 42 amps; at 2000 rpm, 27.8v, 39 amps.

Part total time: 84.0 hours

Cessna 337G Skymaster

Loose Frame Bolts

Front engine charging system went intermittent, then inoperative. Examination found three bolts holding together the alternator frame were loose despite secure and untouched factory safety wiring. Disassembly revealed the loose frame allowed the stator to contact the rotor.

Part total time: 138.0 hours

Piper PA-28-181 Archer II/II

Seized Alternator

The aircraft was in the pattern when its pilots noted the alternator was no longer charging. A strong burning odor entered the cabin. On-ground inspection found the alternator had seized, causing the alternator belt to overheat and melt.

Part total time: Unknown

Piper PA-34-200 Seneca

Broken Rotating Assembly

In-flight failure of the left alternator resulted in smoke coming from the cowl. Aircraft landed safely. Alternator would not turn when turning the propeller. Inspection revealed a diode was missing. Further inspection revealed approximately 1”x1” piece of the rotating assembly had broken off and was lodged in the alternator. Damage to the wiring was also noted.

Part total time: Unknown