N2065BWsk Pzl Mielec M-18A

On August 18, 2009, at 1830 central daylight time, a Wsk Pzl Mielec M-18A Dromader, N2065B, piloted by a commercial pilot, was substantially damaged during a forced landing immediately after takeoff from runway 32 (3,640 feet by 60 feet, concrete) at Audubon County Airport, Audubon, Iowa. The pilot reported a partial loss of engine power during the takeoff run. The aerial application flight was being conducted under 14 Code of Federal Regulations Part 137, without a flight plan. Visual meteorological conditions prevailed. The pilot was not injured. The local flight was originating at the time of the accident.

The pilot stated that he noticed the engine was “low on power” during the takeoff. However, there was not sufficient runway remaining to reject the takeoff. He noted that “at lift off, the engine lost more power” and he was unable to remain airborne. The pilot landed in a corn field about 500 feet from the end of the runway.

The airplane came to rest upright. The fuselage and empennage were substantially damaged during the impact sequence. The engine and propeller remained attached to the airframe. The propeller blades were bent and twisted, but remained secured to the propeller hub. The main landing gear collapsed. The exhaust duct was creased. The exhaust duct also exhibited outward dents consistent with internal impact from exiting debris.

A teardown examination of the Pratt & Whitney PT6A-45B engine revealed that portions of the compressor turbine blades were separated and fragmented. In general, the fragmented blade sections consisted of a triangular portion of the blade; approximately 0.5 inches from the root at the trailing edge to near the end of the blade at the leading edge. Metallic deposits (“metal splatter”) were observed on the compressor turbine blades, shroud, and guide vanes. Metallurgical examination of the compressor turbine blades did not reveal any material anomalies. In addition, no evidence of blade creep was observed.

The power turbine housing was separated from the exhaust duct and partially separated from the reduction gearbox rear housing. The first stage power turbine was dislocated and located in the gas generator case at the time of the examination. The blades were fractured at varying heights above the disc platform. The second stage power turbine remained installed in the power section. The blades were fractured near the disc platform.

The reduction gearbox exhibited a fracture of the rear housing and the second stage planet gear carrier. The remainder of the unit including all reduction gears appeared intact. The first stage sungear remained engaged to the power turbine and mating reduction gears. Continuity was confirmed between the front housing accessory gears and the propeller shaft. The reduction and accessory gearbox chip detectors, as well as the oil filter, contained metallic debris.

Engine accessories tested, including the fuel pump and fuel control unit, did not exhibit any anomalies consistent with a pre-impact failure or malfunction.

Airplane maintenance records indicated that an annual inspection was completed on June 15, 2009, at 3,809 hours total airframe time. The engine was overhauled in October 2007 and subsequently installed on the airframe in February 2008. The pilot reported the airplane had been operated approximately 300 hours since the overhaul.