Accident Ayres S-2R-T41 Turbo Thrush N30902,
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ASN Wikibase Occurrence # 289227
 
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Date:Thursday 16 June 2011
Time:12:30 LT
Type:Silhouette image of generic SS2T model; specific model in this crash may look slightly different    
Ayres S-2R-T41 Turbo Thrush
Owner/operator:Swan Lake Flying Services Inc
Registration: N30902
MSN: T41-179
Year of manufacture:1992
Total airframe hrs:5328 hours
Engine model:P&W PT6A SER
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Athleimer, Arkansas -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Agricultural
Departure airport:Athleimer, AR (None)
Destination airport:Athleimer, AR
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot had just started his first pass spraying fertilizer when the turboprop engine 'exploded” and the propeller suddenly stopped. He saw flames around the cowling and soot and pieces of metal were exiting the exhaust stack. The pilot made a forced landing to a field, which resulted in the landing gear being torn from the airplane. The pilot was able to exit before the airplane was completely consumed by fire. A teardown examination of the engine revealed a failure in the first stage planetary gearset of the propeller reduction gearbox. All the gear teeth of the sun gear were ground down as far as the gear tooth roots, and the three meshing planetary gear teeth were battered and mutilated with only about 2/3 of the gear teeth height remaining. Review of the documentation of the last repair revealed that the gearset was a used replacement from another engine, contrary to manufacturer guidance, which states that first stage planetary gears should be replaced with a new gearset. The shop that sold the used gearset had misrepresented it as being zero-timed. The hours accumulated on the used gearset were beyond the manufacturer's recommended time between overhaul.

Probable Cause: Failure of the first stage planetary gearset in the propeller reduction gearbox, which resulted in catastrophic engine failure. Contributing to the failure was the misrepresentation of the gearset being zero-timed by the company that sold the gearset to the operator. Also contributing was the total accumulated hours on the used gearset, which were beyond the manufacturer's recommended time between overhaul.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CEN11LA404
Status: Investigation completed
Duration: 2 years and 2 months
Download report: Final report

Sources:

NTSB CEN11LA404

Location

Revision history:

Date/timeContributorUpdates
05-Oct-2022 11:21 ASN Update Bot Added

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