Accident Air Tractor AT-502 N4531K,
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ASN Wikibase Occurrence # 240051
 
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Date:Friday 15 September 2017
Time:09:15
Type:Silhouette image of generic AT5T model; specific model in this crash may look slightly different    
Air Tractor AT-502
Owner/operator:Londe Air Llc
Registration: N4531K
MSN: 502-0102
Year of manufacture:1990
Total airframe hrs:5490 hours
Engine model:Pratt & Whitney PWC PT6A-15AG
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Union City, TN -   United States of America
Phase: En route
Nature:Agricultural
Departure airport:Hickman, KY (1M7)
Destination airport:Hickman, KY (1M7)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot of the aerial application flight indicated that the airplane was in cruise flight on its way to an application site when he heard a “pop,” and the engine lost total power. The pilot maneuvered the airplane for a forced landing on a roadway but changed his forced landing site to a corn field due to vehicle traffic. After touchdown, the main landing gear separated, which resulted in substantial damage to the fuselage.
Examination of the engine revealed catastrophic internal damage; all compressor turbine blades were fractured. Metallurgical examination revealed fracture features consistent with high-velocity impact and high-temperature deformation such as "creep." The primary fracture could not be identified; therefore, the sequence in which the fractures occurred could not be determined.
The engine was an assembled compilation of manufacturer and aftermarket parts manufacturer approval (PMA) parts. Some PMA parts installed were not authorized for the application, and the serial numbers reflected in the maintenance records did not match the components installed. For example, the factory original compressor turbine disk was installed, but the logbook indicated another disk was installed. The compressor turbine disk was a time-limited item, and the total hours on the installed disk could not be verified.


Probable Cause: The catastrophic failure of the compressor turbine blades, which resulted in a total loss of engine power. Contributing to the accident was the installation of undocumented, time-limited engine components of indeterminate age.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: ERA17LA326
Status: Investigation completed
Duration: 2 years and 11 months
Download report: Final report

Sources:

NTSB

Location

Revision history:

Date/timeContributorUpdates
15-Aug-2020 16:01 ASN Update Bot Added

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