# SDR 2026F00041

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: July 23, 2025
- Submitted: March 19, 2026
- Operation: General aviation
- Aircraft: [N777ZA](https://openairdocs.org/aircraft/N777ZA), registered now
- Make and model: Bell 407
- Registry model: [Bell 407](https://openairdocs.org/model/bell-helicopter-textron-canada-407) (OpenAirDocs)
- Aircraft serial: 54626
- Aircraft time: 5,442 hours, 5,070 cycles
- Engine: Allsn 250C47B
- Engine time: 4,275 hours, 3,991 cycles
- System (JASC): [7200 · Engine (Turbine/Turboprop)](https://openairdocs.org/jasc/7200)
- Part: Engine
- Condition: Damaged
- Location: Zone 200
- 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/2026F00041

## Discrepancy

UNKNOWN INTERNAL ENGINE COMPONENT CAUSING BURNING OF OIL AFTER ENGINE OVERHAUL AND REPLACEMENT OF ALL 4 TURBINE WHEELS.  FIRST OCCURRENCE RECORDED AFTER SMOKE WAS OBSERVED COMING FROM THE EXHAUST WHEN THE AIRCRAFT WAS AT IDLE AND DURING SHUTDOWN AFTER A FLIGHT ON 7/23/2025, ENGINE TSO: 13.9 HRS. TROUBLESHOOTING OF ENGINE AND AIRFRAME SYSTEMS COORDINATED WITH PHI (WHO PERFORMED THE PRIOR MAINTENANCE) AND ASSIGNED ROLLS ROYCE TECH REP.  OIL APPEARED AND SMELLED BURNED.  NO CONCLUSIVE CAUSE FOUND.  ENGINE WAS REMOVED FROM SERVICE AND RETURNED TO PHI FOR A TEAR DOWN INSPECTION.  DURING THE INSPECTION TIME, A RENTAL ENGINE ACCUMULATED 170.5 HOURS ON THE SAME AIRFRAME WITH NO DISCREPANCIES.  NO CONCLUSIVE CAUSE WAS FOUND DURING PHI'S TEAR DOWN INSPECTION.  ENGINE RETURNED TO ZIP AVIATION AND REINSTALLED ON THE SAME AIRFRAME ON 10/11/2025.  ON 1/8/2026, TSO: 272.2 HRS, SMOKE WAS AGAIN OBSERVED COMING FROM THE EXHAUST AT IDLE AND SHUTDOWN AFTER A FLIGHT.  TROUBLESHOOTING FOUND NO CONCLUSIVE CAUSE.  OIL APPEARED AND SMELLED BURNED.  ENGINE WAS REMOVED FROM SERVICE AND SENT BACK TO PHI FOR ADDITIONAL INSPECTION/TROUBLESHOOTING.  NUMEROUS PARTS OF THE ENGINE HAVE BEEN REPLACED DURING THIS TIME.  AFTER APPROXIMATELY 4 HOURS OF RUNNING ON THEIR TEST CELL, OIL IS STILL BEING FOUND TO BE BURNED.  TROUBLESHOOTING IS STILL IN PROGRESS.  PHI'S THEORY IS THE DISCREPANCY IS INTERNAL OF THE TURBINE MODULE.  OPEN

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