NTSB Identification: DFW07LA165.
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Accident occurred Friday, July 20, 2007 in Slaton, TX
Probable Cause Approval Date: 01/31/2008
Aircraft: Air Tractor AT-502, registration: N15400
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot/owner of the single-engine agricultural airplane stated that the gas turbine rotation speed (Ng) was adjusted "one click" prior to departure to increase the engine power from 96 percent to 100 percent (normal range is between 50 and 102 percent). Shortly after takeoff, at an altitude of approximately 150-feet above ground level (agl), the pilot noted that the Ng speed was still at 96 percent, so he turned back toward the airport. As the pilot was turning back to the airport, the engine lost power, and he was unable to maintain altitude. The pilot made a forced landing to a dirt road, impacted a stop sign, and continued over a highway and into an open field. The pilot added that the engine was still producing enough power for him to taxi the airplane out of the field and back onto the highway. External examination of the engine revealed there was a 5-inch-wide hole in the engine's compressor housing. The engine was then disassembled into two sections; the power section module and the gas generator module. Damage of the power section included torn and nicked compressor turbine blades (leading edge), excessive FOD damage to the hot section stator vanes, the power turbine shroud was bent, buckled, and torn with several bolts sheared out of their holes. The containment ring was split in half. The power turbine stator vanes were torn and deformed. The power turbine wheel had 10 sheared blades at or near the blade root, and several other blades were broken in half. The chip detector was removed and was filled with large metal chips. The oil filter was filled with a small amount of fine metallic particles. Examination of the gas generator revealed that the compressor bleed valve, fuel manifolds, compressor turbine stator assembly, accessory gear box assembly, impeller, compressor inlet case and compressor rotor in the gas generator case, and the compressor turbine blades exhibited no anomalies. A review of maintenance records revealed that the last 100-hour inspection performed on the engine was on April 27, 2007, at a Hobbs time of 5,892.9 hours. However, there was no record of the engine's last overhaul, no record of present engine total time/time since overhaul, and no record of engine removal from the aircraft. The reason for the loss of engine power could not be determined.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: An uncontained failure of the turbine engine's power section for undetermined reasons. Full narrative available
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