# SDR 2026FA0000327

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: May 7, 2026
- Submitted: May 7, 2026
- Operation: General aviation
- Aircraft: [N6823D](https://openairdocs.org/aircraft/N6823D), registered now
- Make and model: Cessna 340A
- Registry model: [Cessna 340A](https://openairdocs.org/model/cessna-340a) (OpenAirDocs)
- Aircraft serial: 340A1042
- Aircraft time: 5,769 hours
- Engine: Cont TSIO520*
- Engine time: 6,428 hours
- System (JASC): [2434 · DC Generator-Alternator](https://openairdocs.org/jasc/2434)
- Part: Alternator
- Part number: C28150S
- Part serial: HX013179
- Condition: Destroyed
- Location: Engine
- Part time: 482 hours
- Stage of operation: NR
- How discovered: V
- Nature of condition: H
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/2026FA0000327

## Discrepancy

ALTERNATOR INPUT SHAFT HAS BEEN DAMAGED DUE TO DETROYED DRIVE COUPLING.  DRIVE COUPLING HUB NO LONGER ROUND AND WOODRUFF KEY SLOT NO LONGER VISIBLE AS THE HOLE IS NOW EGG-SHAPED.  DRIVE COUPLING HUB & GEAR COMPLETELY SEPARATED WITH NEARLY ALL RUBBER BUSHING MISSING.  WOODRUFF KEY PIECES FUSED TO INPUT SHAFT OF ALTERNATOR. ENG'S CRANKSHAFT ALTERNATOR DRIVE GEAR FACE SEPARATED FROM CRANKSHAFT.  ALL 4 BOLTS SHEARED OFF WITH ENDS STILL INSIDE GEAR, REMAINDER OF BOLTS IN OIL SUMP.  BOLT LOCK PLATES  FOUND IN SUMP, SEVERLY DAMAGED,  SHOW SIGNS OF PROPER INSTALLATION & LOCKING CONDITION AS REQUIRED.  GEAR IS COMPLETELY CRACKED THRU IN 1 PLACE BUT STILL ROUND AND IN PLACE AROUND CRANKSHAFT FLANGE. ENG IS COMPLETELY DESTROYED AS GEAR FACE WAS PUSHED AGAINST THE CRANKCASE, WEARING A LARGE GROOVE IN CASE.  CRANKSHAFT DAMAGED.  ALL GEARS IN SAME LOCATION SHOW SIGNS OF METAL CONTAMINATION.   UNABLE TO DETERMINE WHERE FAILURE BEGAN, IT ALWAYS INVOLVES AN ASSEMBLY INVOLVING DRIVE COUPLINGS INSTALLED ON PLANE POWER ALTERNATORS.  THERE'S BEEN A SUBSEQUENT FAILURE OF THE CRANKSHAFT GEAR RETAINING BOLTS.   HAVE NOT SEEN THIS TYPE OF FAILURE WITH ANOTHER ALTERNATOR MANUFACTURER OR MODEL.  IT SEEMS TO BE A COMMON OCCURRENCE WITH CRANKSHAFT DRIVEN HARTZELL PLANE POWER ALTERNATORS.  THIS IS ONE OF THREE INSTANCES OF CATASTOPHIC ENGINE FAILURES WITH A PLANE POWER ALTERNATOR INSTALLATION THIS ENTITY HAS SEEN.  CONVERSATIONS WITH OTHER ENTITIES INCLUDE CATASTROPHIC ENGINE FAILURES WITH PLANE POWER ENGINE DRIVEN ALTERNATORS INSTALLED.  THE DRIVE COUPLING WAS PROPERLY INSTALLED AND THE CRANKSHAFT GEAR FACES AND TEETH WERE INSPECTED IN ACCORDANCE WITH CMI MANUAL M-0.

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