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ASN Wikibase Occurrence # 176268
Last updated: 30 November 2021
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Date:20-MAY-2015
Time:14:40
Type:Silhouette image of generic SS2T model; specific model in this crash may look slightly different
Ayres S-2R-G6 Turbo Thrush
Owner/operator:A T Ag Services, LLC
Registration: N3300U
MSN: G6-139
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: Substantial
Category:Accident
Location:Refugio County south of Tivoli, TX -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Agricultural
Departure airport:Tivoli, TX
Destination airport:Tivoli, TX
Investigating agency: NTSB
Narrative:
The pilot reported that, during the accident flight, which was the twelfth aerial application flight of the day, the engine made an uncommanded power acceleration. The pilot retarded the throttle lever, but the engine did not respond. The pilot subsequently made a forced landing into a field, and the airplane nosed over and then came to rest inverted.

A postaccident examination of the airplane revealed no anomalies with the engine rigging. Examination of the fuel control unit revealed that the stub shaft spline was worn beyond the allowable limits. Such wear can allow the fuel control underspeed governor to be driven at a lower speed than the engine speed, which can increase fuel flow and engine speed and is consistent with the uncommanded power acceleration that occurred during the accident flight. A review of the airplane's maintenance records revealed that, 2 months before the accident flight, the fuel control unit was inspected for wear and damage in accordance with an airworthiness directive (AD). It is unlikely that the wear observed during the postaccident examination could have occurred between the time of the AD inspection and the accident. It is likely that the AD was either not accomplished as noted in the maintenance records or that maintenance personnel inadequately conducted the inspection.


Probable Cause: The failure of the fuel control unit due to the worn stub shaft spline, which resulted in an engine overspeed. Contributing to the accident was maintenance personnel's inadequate inspection of the fuel control unit.

Sources:

NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N3300U

Accident investigation:
cover
  
Investigating agency: NTSB
Status: Investigation completed
Duration:
Download report: Final report
Location


Revision history:

Date/timeContributorUpdates
21-May-2015 16:20 Geno Added
21-Dec-2016 19:30 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
01-Dec-2017 13:06 ASN Update Bot Updated [Operator, Departure airport, Destination airport, Source, Narrative]

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