Lamesa, TX, USA
N91905
Air Tractor AT-502
The 22,894-hour pilot reported that after a "normal" takeoff he reduced the throttle to cruise power and the "engine started losing power." During a forced landing, the aircraft nosed over and came to rest in an inverted position. Examination of the engine by a Pratt & Whitney representative revealed that the P3 air filter, low pressure fuel pump filter, and the fuel line between the fuel control unit (FCU) and the oil/fuel heat exchanger contained dirt and water contamination. The 14 fuel nozzles were removed and flow checked. One nozzle met the manufacturer's specifications, one nozzle was completely obstructed, and the remaining 12 nozzles displayed "varying degrees of streaking."
On April 15, 2002, at 1202 central daylight time, an Air Tractor AT-502 agricultural airplane, N91905, was substantially damaged during a forced landing following a loss of engine power near Lamesa, Texas. The airplane was registered to a private individual who was doing business as Hogg Flying Service of Lamesa, Texas. The commercial pilot, sole occupant of the airplane, sustained minor injuries. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 137 aerial application flight. The local flight originated from the Lamesa Municipal Airport, Lamesa, Texas, at 1155. According to the 22,894-hour pilot, the airplane departed from runway 16 with a load of granular fertilizer. The pilot reported that after a "normal" takeoff he reduced the throttle to cruise power and the "engine started losing power." A forced landing was executed to a soft field 1.5 miles from the departure runway, during which the airplane nosed over and came to rest inverted. The FAA inspector, who examined the airplane at the accident site, reported that both wings sustained structural damage and the engine was displaced from the engine firewall. According to a representative from Pratt & Whitney (P&W) who examined the airplane, two propeller blades were curled, one propeller blade was bent aft, and the propeller spinner remained attached. The high pressure fuel filter bowl was removed and "large amounts of very fine sand/dirt [were found] between the pleats" of the fuel filter. The engine was removed from the aircraft and transported to P&W in Addison, Texas, for examination. The engine was examined at P&W under supervision of the NTSB Investigator-In-Charge. The P3 air filter was removed and dirt contamination was present in the wire screen; however, there was no water present. The low pressure fuel pump was removed and its filter was contaminated with water and dirt. The fuel line between the fuel control unit (FCU) and the oil/fuel heat exchanger contained water contamination. The 14 fuel nozzles were removed and flow checked. One nozzle met the manufacturer's specifications, one nozzle was completely obstructed, and the remaining 12 nozzles displayed "varying degrees of streaking." The high pressure fuel pump and FCU were removed as one assembly and sent to the P&W facility in Canada for further examination. The low pressure fuel pump was removed and sent to S&T Accessories, Inc., in New Braunfels, Texas, for further testing. The turbine section was boroscoped and the blades for the second stage turbine were intact. Furthermore, the blade tips and their respective shrouds did not display rub marks or scoring.
The loss of engine power due to contamination of the fuel system. A contributing factor was the lack of suitable terrain for the forced landing.
Source: NTSB Aviation Accident Database
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