Accident Overview
On May 31, 2015, at approximately 0815 central daylight time, an Air Tractor 502B airplane, registration N120TF, struck power transmission line wires while maneuvering about five nautical miles southwest of Archer City, Texas. The aircraft was operated under 14 Code of Federal Regulations Part 137 as an agricultural aerial application flight. Visual meteorological conditions prevailed, and the flight was not conducted under a visual flight rules flight plan. The flight had originated from Wichita Valley Airport (F14) at 0645.
The commercial pilot, who was the sole occupant, sustained serious injuries. The airplane was substantially damaged, including the fuselage, both wings, and the empennage.
Aircraft and Operator Information
The single-seat, low-wing, fixed-gear airplane was manufactured in 2007 and powered by a Pratt and Whitney PT6A-34AG turbine engine rated at 750 horsepower, equipped with a Hartzell three-bladed adjustable-pitch propeller. The aircraft was registered to the Bank of Utah Trustee and operated by Chanay Aircraft Service Inc., based in Wichita Falls, Texas. According to the operator, the most recent annual inspection was completed in December 2014. At the time of the accident, the airframe and engine had accumulated 4,100 hours.
Meteorological Conditions
A review of recorded data from a nearby automated weather observation station (elevation 998 feet) indicated that at 1315 conditions were wind from 360 degrees at 4 knots, visibility of 10 statute miles, and clear skies.
Wreckage and Impact Details
The accident site was approximately 75 feet east of Texas State Highway 79, on flat grass pasture with short mesquite shrubs and cactus. A set of east-west oriented cross-country transmission lines were located about 500 feet north of the site. The top two wires were broken and lying on the roadway; the lower three wires were intact but hanging low enough to pose a hazard to highway traffic at about 6 feet above the road.
The aircraft wreckage was east of the highway in the pasture, about 500 feet southwest of the damaged transmission lines. The airplane came to rest upright with the nose pointing south-southwest, parallel to the highway. Substantial damage was noted to the fuselage forward of the cockpit. The wing leading edges exhibited crush damage, and wing skin panels were buckled with popped rivet lines. The tailwheel was suspended above the ground.
All flight control surfaces and major components were located near the main wreckage. Both main landing gear legs, the propeller and engine reduction gearbox, and other miscellaneous parts were found between initial impact marks and the main wreckage. Continuity of all flight controls was established during examination. The engine was damaged in the impact; the propeller and reduction gearbox separated from the engine at the engine "A" flange. Two of the three propeller blades had broken tips near the debris path start. Blade A displayed torsional twisting and a 90-degree bend about 12 inches from the hub; blades B and C showed torsional twisting and bending, respectively.
Pilot Statement
During a telephone conversation with the National Transportation Safety Board investigator-in-charge on June 29, 2015, the pilot stated that he did not remember much from the day of the accident. He also reported no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.
Operational Context
Representatives from Chanay Aircraft Services reported that the pasture was being treated with herbicide. The pilot had already made applications on other area pastures before moving to the accident pasture.