FLUVANNA, TX, USA
N73127
Air Tractor AT-400
The pilot was performing a swath run when he felt a vibration, and then the engine lost power. A forced landing was initiated to a plowed field. During the landing sequence, the left main landing gear separated from the fuselage, and the right wing spar was bent upward. A teardown inspection of the airplane's engine revealed that the reduction gear box failed and sheared the drive shaft. According to the FAA inspector, 'This failure allowed a turbine over speed to the point that the turbine blades separated from the wheel causing a contained catastrophic failure.'
On April 19, 1997, at 1400 central daylight time, an Air Tractor AT-400 agricultural airplane, N73127, registered to and operated by Benny White Flying Service, Inc., as a Title 14 CFR Part 137 aerial application flight, was substantially damaged during a forced landing following a loss of engine power near Fluvanna, Texas. The commercial pilot was not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the local flight that originated from a private airstrip near Lamesa, Texas. According to the pilot, he was performing a swath run when he felt a vibration, followed by a loss of engine power. A forced landing was initiated to a plowed field. During the landing sequence, the left main landing gear separated from the fuselage, and the right wing spar was bent upward. Examination of the PT6A-27 engine by a mechanic and the FAA inspector revealed that the turbine disc was missing approximately half of its blades. The engine was sent to Dallas Airmotive in Dallas, Texas, for further examination. On May 22, 1997, a teardown inspection revealed that the reduction gear box failed and sheared the drive shaft. According to the FAA inspector, "It was impossible to determine which part failed first. This failure allowed a turbine over speed to the point that the turbine blades separated from the wheel causing a contained catastrophic failure." According to the operator, the engine had accumulated a total of 2,430 hours since new, with approximately 1,300 hours since last overhaul.
The loss of engine power due to the failure of the reduction gear box. A factor was the lack of suitable terrain for the forced landing.
Source: NTSB Aviation Accident Database
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