# SDR 2020FA0000319

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: June 22, 2020
- Submitted: June 30, 2020
- Operation: General aviation
- Aircraft: [N441CD](https://openairdocs.org/aircraft/N441CD), registered now
- Make and model: Robsin R44RAVENII
- Aircraft serial: 12878
- Aircraft time: 1,146 hours
- System (JASC): [6310 · Engine/Transmission Coupling](https://openairdocs.org/jasc/6310)
- Part: Sprag Clutch
- Part number: C1883
- Part serial: 7129
- Condition: Abnormal
- Location: Drive Train
- Part time: 1,146 hours
- Stage of operation: DE
- How discovered: O
- Nature of condition: R
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/2020FA0000319

## Discrepancy

OWNER COMPLAINED OF POWER LOSS DURING LEVEL OFF AND FLARE AFTER DESCENT. HE INSISTED THERE WAS NO "NEEDLE SPLIT". IN SPITE OF THAT, I SUSPECTED AN ISSUE WITH THE OVERRUNNING (SPRAG) CLUTCH. I FLIGHT TESTED AND ALL APPEARED NORMAL. AFTER CHECKING EVERYTHING THAT COULD CAUSE AN INTERMITTENT, TEMPORARY POWER LOSS INCLUDING ENGINE AND GOVERNOR SYSTEMS AND ELIMINATING ENGINE AND ASSOCIATED SYSTEMS AS A POSSIBLE CAUSE, I FLIGHT TESTED THE AIRCRAFT AGAIN CONCENTRATING ON POWER RECOVERY FROM AUTOROTATIVE DESCENT. ON THE THIRD AUTOROTATION DESCENT WITH NEEDLES WELL SPLIT I INITIATED A GENTLE POWER RECOVERY. THE OVERRUNNING CLUTCH FAILED TO LOCK BACK UP WHEN NEEDLES WERE JOINED. I ROLLED THROTTLE BACK OFF AND REJOINED THE NEEDLES VERY CAREFULLY, ROCKING THE THROTTLE AS THE NEEDLES REJOINED. THE CLUTCH LOCKED BACK UP AND I WAS ABLE TO COMPLETE A NORMAL LANDING BEING EXTREMELY CAREFUL NOT TO ALLOW ANOTHER NEEDLE SPLIT. I HAD PREVIOUSLY (DURING INITIAL TROUBLESHOOTING) DRAINED AND INSPECTED THE SPRAG CLUTCH FLUID. IT SHOWED NO EVIDENCE OF METAL PARTICLES.  WE THEN INSTALLED A OVERHAULED CLUTCH ASSEMBLY INCLUDING A NEW SPRAG CLUTCH. PROBLEM SOLVED. ROBINSON HELICOPTERS IS INVESTIGATING THE CAUSE OF THE FAILURE.

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