# SDR 2026FA0000472

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: May 28, 2026
- Submitted: June 2, 2026
- Operation: General aviation
- Aircraft: [N774CB](https://openairdocs.org/aircraft/N774CB), registered now
- Make and model: Hughes 369E
- Registry model: [Hughes 369E](https://openairdocs.org/model/hughes-helicopters-369e) (OpenAirDocs)
- Aircraft serial: 0016E
- Engine: Allsn 250C20
- System (JASC): [7200 · Engine (Turbine/Turboprop)](https://openairdocs.org/jasc/7200)
- Part: Lock Nut
- Part number: MS21043
- Condition: Failed
- Location: Zone 100
- Stage of operation: IN
- How discovered: V
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/2026FA0000472

## Discrepancy

MS20143 NUTS ARE UTILIZED TO SECURE WITHIN THE ENGINE ASSEMBLY THE FOLLOWING ARTICLES COMPRESSOR, TURBINE, FUEL CONTROL, GOVERNOR, FUEL PUMP, TACH GENERATORS, GEARBOX SPLIT LINE, AND HAVE BEEN FOUND NUMEROUS OCCASIONS BACKING OFF.  THE MS21043 NUTS HAVE BEEN RECEIVED NEW FROM MANUFACTURER WITH NO DRAG TORQUE. THE LOCKING FEATURE IS FAILING. LOT NUMBERS ARE NOT SIMILAR. LOT NUMBERS, A FEW ARE 54539-000, 206242-1, 101638, 7365911005, M001463-001. MANUFACTURERS ARE VARIOUS FROM ONE MONROE AEROSPACE, AVAIL (BOEING), TO ESNA. 3 SEPARATE TURBINE INSTALLATIONS WHERE NEW NUTS WERE INSTALLED FAILED. NUTS WERE TORQUED PER M250C20-OMM 10W2 72-50-00. THE LAST 3 COMPRESSOR INSTALLATION WHERE THE NUTS WERE REPLACED HAD THE SAME ISSUE WHERE THE BUTS WERE BACKING OFF.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.