Pilot Debrief

AYRES CORPORATION S2R-T34 near Athleimer, AR — 2011-06-16

Final reportCEN11LA404
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Date
2011-06-16
Location
Athleimer, AR, USA
Aircraft
AYRES CORPORATION S2R-T34
Registration
N30902
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Initial climb

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.

NTSB 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.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Using a new gearset instead of a used one during the engine repair.

NTSB coding

Evidence available

  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

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