History of Flight
On July 11, 2018, about 0630 central daylight time, an Air Tractor AT-602 airplane, registration N8508P, was destroyed when it impacted a wooded area about 1.5 miles north of Wheatley, Arkansas, and was consumed by a postcrash fire. The commercial pilot received fatal injuries. The airplane was owned by D-GER LLC and operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which departed about 0600 from Frank Federer Memorial Airport (M36), Brinkley, Arkansas.
A witness reported that the pilot loaded the airplane with 400 gallons of chemical and that the airplane's fuel tanks were full before departure. The witness stated that the pilot planned to spray his own 40-acre field about 5 nautical miles from M36. No witnesses to the accident were identified. Another witness reported seeing fire and smoke about 0630, and the wreckage was subsequently located by first responders.
Personnel Information
The 41-year-old pilot held a commercial pilot certificate with ratings for airplane single- and multi-engine land. He held a second-class Federal Aviation Administration airman medical certificate issued on January 22, 2018, with no limitations. On the application for that certificate, the pilot reported 4,023 total hours of flight experience, with 200 hours in the previous 6 months. The pilot's logbook indicated that he obtained his agricultural aircraft pilot endorsement on May 1, 2007.
Aircraft Information
The low-wing, single-engine airplane was manufactured in 2003 and powered by a 1,050-horsepower Pratt & Whitney PT6A-60AG engine equipped with a 5-blade Hartzell propeller. The airplane had a maximum takeoff weight of 12,500 lbs. The most recent annual inspection was conducted on February 12, 2018, at a total airframe time of 6,965.4 hours.
Meteorological Information
At 0553, the recorded surface weather observation at Bill and Hillary Clinton National Airport (LIT), Little Rock, Arkansas, located 56 nm from the accident site, included wind from 240° at 3 knots; 10 miles visibility; few clouds at 200 ft above ground level; temperature 24°C; dew point 23°C; and altimeter 30.03 inches of mercury.
Wreckage and Impact Information
The wreckage was found in a wooded area between two open fields about 1/3 mile west of the application field. A 6-ft-deep gully ran northeast-to-southwest through the wooded area. The debris path was over 200 ft long and oriented on a magnetic heading of 280°. The initial impact point was a shallow ground scar containing components from the underside of the fuselage. The debris path extended into the wooded area and comprised wing and empennage components. The fuselage was found on the north side of the gully about 120 ft from the initial impact point. The engine was separated from the fuselage and found in the gully below the fuselage. Most separated fuselage components were found in the gully to the southwest.
A postcrash fire consumed most of the fuselage's aluminum skin and components, limited to the area near the main wreckage. The central portion of the fuselage, including the hopper and cockpit, suffered the most fire damage. All cockpit instruments, circuit breakers, and controls were destroyed. The agricultural GPS system was destroyed, and none of the non-volatile memory components were recovered.
Both wings were destroyed by impact forces. The main wing spar was found bent around a tree. All wing ribs and skins were separated from the spar. The rear spar of both wings was fractured in numerous places and found throughout the wreckage.
The rudder, vertical stabilizer, right elevator, and right horizontal stabilizer were found damaged but remained partially connected to the fuselage. The outboard section of the left horizontal stabilizer and left elevator were found in a tree along the debris path.
All flight control surfaces were located with the main wreckage. The control stick was intact in the cockpit, and elevator controls were continuous to the control horns, except for fire damage to the aluminum pushrod and control stick pivot. The left stainless steel rudder cable showed continuity from the rudder control horn to the rudder pedal attachment fitting. The right stainless steel rudder cable remained attached to the rudder control horn, but had a "horsetail" separation at about mid-length, consistent with tensile overload. From this separation, the cable was traced to its forward end, embedded in melted aluminum and debris. The right rudder pedal was destroyed by fire.
The aileron controls consisted of steel pushrods connecting the control stick to aileron control horns through a torque tube and multiple bellcranks and idlers. Primary aileron controls were heavily damaged due to impact but were continuous except for separations from tree and ground impact.
The engine was separated from the mount ring at the "A" and "F" flanges. The exhaust case exhibited significant fore-aft crush damage. First stage compressor blades showed counter-rotational curling of blade tips and damage to leading edges.
The 5-bladed propeller remained connected to the engine propeller shaft. The propeller dome was fractured, and the internal spring had been liberated. Dome components and spring were found near the main wreckage.
The area surrounding the application field displayed no evidence of tree or wire strikes.
The engine and propeller were recovered and sent to the Pratt & Whitney Service Center in Bridgeport, West Virginia, for examination under NTSB oversight. First stage compressor blades exhibited impact damage, and several blades were bent opposite the direction of rotation. All blades showed rubbing from contact with the shroud. The third stage compressor stator was rubbed from contact with the spacer. The impeller exhibited rubbing on all airfoils from contact with the shroud, and its front face had rubbed the gas generator case.
The downstream side of the compressor turbine disc and blades exhibited rotational scoring from rubbing against the upstream side of the first stage power turbine vane. The compressor turbine shroud exhibited re-hardened melted material from blade rubbing.
Rotational scoring was evident on the downstream side of the second stage disc and blades from contact with the exhaust duct and No. 3 bearing/power turbine shaft housing. The power turbine shaft was fractured, with features consistent with torsional overload.
The first stage power turbine vane, baffle, and baffle retention rivets exhibited rotational scoring on the upstream side from contact with the compressor turbine.
Examination of the propeller revealed that the piston was fractured and fragmented. One piston fragment displayed an impact mark from the cylinder top corner about 2.37 inches from the bottom edge, roughly equivalent to a blade angle range of 13.7° to 16.7°. The cylinder was bent and buckled with marks from the piston bottom edge. Two crease marks were about 2.13 inches and 1.6 inches from the top of the cylinder, equivalent to blade angles of about -12° to 9.3°. One circumferential mark was about 2.49 inches from the top corner, equivalent to a blade angle range of about 17.3° to 20.3°. Longitudinal scoring marks started from about 3.125 inches below the top corner, equivalent to about 36° to 39°.
Damage to the 5 propeller blades included face-side chordwise/rotational abrasion, leading edge gouging, tip and mid-blade fractures, bending in the thrust/forward direction, S-bends, and twisting toward high pitch.
Medical and Pathological Information
The Travis County Office of the Medical Examiner, Austin, Texas, performed an autopsy of the pilot. The cause of death was multiple blunt force injuries. Toxicology testing at the FAA's Forensic Sciences Laboratory was negative for carbon monoxide and ethanol in the blood. No tested-for drugs were found in the blood.