Pilot Debrief

AIR TRACTOR INC AT-502B near Decatur, IL — 2022-07-11

Final reportCEN22LA312
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Date
2022-07-11
Location
Decatur, IL, USA
Airport
DEC
Aircraft
AIR TRACTOR INC AT-502B
Registration
N5850R
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Initial climb

Probable cause

Fracture of the compressor turbine (CT) blades due to creep.

NTSB narrative

During departure climbout for spray operations, the pilot heard a “pop” and observed white smoke trailing the airplane. The pilot made a forced landing, during which the airplane struck an airport perimeter fence that resulted in substantial damaged to both wings. Examination revealed that all compressor turbine (CT) rotor blades were fractured at varying spanwise locations. The power turbine (PT) rotor blades downstream of the CT blades exhibited impact damage and were fractured at varying spanwise locations. Metallurgical analysis of the CT blades revealed micro-voids were present along the material grain boundaries and rafting of the gamma prime which were indicative of creep. Metallurgical analysis of the CT blades revealed solutioning of the gamma prime which is consistent with exposure to temperature in excess of the engine operating limits. It was not determined if the exposure to elevated temperatures occurred before or during the event.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have adhered to POH recommended power settings to prevent engine failure.

NTSB coding

Evidence available

  • Photos
  • 6 docket documents
View NTSB final reportView NTSB docket

Docket documents6

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