ASN Wikibase Occurrence # 225613
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| Date: | Saturday 25 May 2019 |
| Time: | 13:30 LT |
| Type: |  Rockwell S-2R-T331 Turbo Thrush |
| Owner/operator: | Bearcreek Flying Service LLC |
| Registration: | N4907X |
| MSN: | 2099R |
| Year of manufacture: | 1974 |
| Total airframe hrs: | 12813 hours |
| Engine model: | Honeywell TPE-331-10 |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Oakes, Dickey County, ND -
 United States of America
|
| Phase: | Landing |
| Nature: | Agricultural |
| Departure airport: | Oakes, ND (2D5) |
| Oakes, ND (2D5) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot was conducting an agricultural application flight in the turbopropeller-equipped airplane when the engine lost total power. The pilot maneuvered the airplane for a forced landing to an uneven field, resulting in substantial damage to the fuselage and wings.
Teardown examination of the engine revealed that the teeth of the engine's helical cam gear were fractured. Several of the gear teeth cracks showed signatures consistent with fatigue failure. The engine assembly had a relatively low time in service (485 hours) since its most recent overhaul. The helical cam gear assembly did not show pre-existing installation anomalies.
The type and degree of damage to the helical cam gear was indicative of an uncoupling of the high-speed pinion from the helical cam gear of the engine torque sensor. The uncoupling event resulted in the continuous activation of the negative torque system, which likely drained the oil in the propeller and increased the propeller blade angle. This action would have resulted in an increase in engine operating temperature and subsequent loss of engine power.
Probable Cause: The failure of the helical cam gear of the engine assembly due to fatigue cracks in the gear teeth, which resulted in a total loss of engine power.
Accident investigation:
 |
|
Sources:
NTSB CEN19LA156
FAA register: https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N4907X
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 30-May-2019 09:26 | Captain Adam | Added |
| 30-May-2019 14:28 | Geno | Updated [Source] |
| 30-May-2019 19:56 | RobertMB | Updated [Aircraft type, Source, Narrative] |
| 30-May-2019 19:56 | RobertMB | Updated [Time] |
| 02-Jul-2022 09:02 | ASN Update Bot | Updated [Time, Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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