Incident
While returning to a private airstrip, the pilot heard a loud explosion from the engine. The engine subsequently lost all power, and the pilot executed a forced landing to a soybean field. During the landing, the right wing contacted the ground, causing the airplane to come to rest inverted.
Engine Examination
The airplane was equipped with a Honeywell (Garrett) TPE331-43A turboprop engine. Examination of the engine revealed that the second stage turbine rotor was fractured, separated, and lodged in the back of the engine. The second stage turbine stator seal plate assembly exhibited warpage. The evidence was consistent with the warped second stage turbine stator seal plate contacting the second stage turbine rotor, causing the rotor to separate.
Maintenance History
Airworthiness directive (AD) 86-08-06 R1 pertained to the accident engine and required an x-ray inspection of the second stage turbine stator seal plate assembly to detect and repair warpage. The last annual inspection of the airplane was performed approximately four months prior to the accident. According to the aircraft logbooks, the airframe and powerplant mechanic with an inspection authorization (IA) noted the AD as not applicable due to the engine model number. However, the subject engine model number did require completion of the AD.