# SDR 2026FA0000198

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: January 23, 2026
- Submitted: March 19, 2026
- Operation: General aviation
- Aircraft: [N126AV](https://openairdocs.org/aircraft/N126AV), registered now
- Make and model: Cessna 172S
- Registry model: [Cessna 172S](https://openairdocs.org/model/cessna-172s) (OpenAirDocs)
- Aircraft serial: 172S10621
- Aircraft time: 2,660 hours
- Engine: Lyc IO360L2A
- System (JASC): [7414 · Magneto/Distributor](https://openairdocs.org/jasc/7414)
- Part: Impulse Coupling
- Part number: 3163
- Part serial: NA
- Condition: Destroyed
- Location: Magneto
- Part time: 1,061 hours
- Component: Magneto, Champion
- Component part number: 4371
- Stage of operation: CR
- How discovered: V
- Nature of condition: R
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/2026FA0000198

## Discrepancy

PILOT REPORT OF FLUCTUATING RPM'S WHILE IN CRUISE FLIGHT, PLUS OR MINUS 400RPM. DURING GROUND RUN FOR TROUBLESHOOTING, RH MAGNETO MAG DROP WAS EXCESSIVE. FURTHER ATTEMPTS AT CLEARING PLUGS, ETC, TO THEN RECHECK RH MAGNETO DROP RESULTED IN COMPLETE ENGINE SHUT DOWN WHEN RH MAGNETO SELECTED ON IGNITION SWITCH.  MAGNETO REMOVED AND SENT TO REPAIR FACILITY WHERE IT WAS DISCOVERED THAT THE RIVETS HOLDING THE PAWLS IN PLACE HAD LOOSENED, ALLOWING THE PAWLS MOVE IN AN OBLONG PATTERN, CONTACTING AND DAMAGING THE OIL SEAL, INTRODUCING OIL INTO THE MAGNETO HOUSING WHICH CAUSED A LACK OF SPARK.

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