Accident Details
On July 28, 2016, at approximately 1530 central daylight time, an Air Tractor AT-602, registration N2033N, impacted a corn field about 3 miles northeast of David City, Nebraska. The pilot, the sole occupant, sustained fatal injuries. The airplane was destroyed. The flight operated under 14 CFR Part 137 as an aerial application flight, registered to Rayne Aviation, LLC, and operated by Emrich Aerial Spraying, LLC, both of Dorchester, Nebraska. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from Columbus Municipal Airport (OLU), Columbus, Nebraska, about 1430.
The airplane had been spraying Headline Fungicide on a corn field. The accident site was located 200 feet north of County Road 38 and west of County Road O. There was no fire and no witnesses.
Impact and Wreckage
On-scene evidence indicated the airplane struck the ground in a right wing slightly low, 60° nose-down attitude. It rebounded about 20 feet from the initial impact point and came to rest upright facing south. Witness marks in the field were consistent with a large sweep of the right wing through the corn crop, indicating right wing-down rolling motion at impact. All impact signatures and crop damage were in a northerly direction, and the debris field was small.
The aft cockpit wall behind the pilot's seat was deformed. Elevator and rudder control continuity was confirmed. Aileron controls were continuous except for fractures at both wing roots. All hardware was properly installed. The Hobbs meter was destroyed. The airplane was equipped with an inflatable restraint system, which had deployed. The flap actuator was extended 3-7/8 inches, correlating to a flap deflection of 28° to 30° according to Air Tractor.
Engine and Propeller Examination
Examination of the engine revealed dark colored debris on the fuel control unit low pressure fuel filter and in the filter bowl, and chalky gray sediment in the high pressure fuel filter housing. The propeller assembly fractured off the engine propeller shaft on impact. Two blades remained attached; three blades broke off. One blade was found near the propeller assembly, a second in front of the fuselage, and a third was recovered several weeks later some distance from the main wreckage.
On August 18, 2016, FAA and Pratt & Whitney examined the airplane, engine, propeller, and fuel system. Pratt & Whitney noted the engine displayed contact signatures characteristic of making significant power at impact, with no indications of malfunction or pre-impact failure. The propeller blades and hub bore no indications of Beta mode or reverse pitch.
Further examination on December 1, 2016, at Stallings Aircraft Propeller in Wynne, Arkansas, with representatives from Hartzell Propellers and Air Tractor, determined the blade butt, piston, cylinder, and rod impact marks indicated the propeller was operating at a blade angle range of approximately 16° to 19° at impact. The beta ring low pitch for this propeller is 13.9° and the hydraulic low pitch is approximately 7.9°. The estimated blade angle at impact was above the low pitch stop and in the normal operating range. Hartzell's report concluded no discrepancies were noted that would prevent or degrade normal propeller operation prior to impact; all damage was consistent with high impact forces.
Flight Data Recorder Analysis
A SATLOC aerial guidance system was recovered and sent to the NTSB Vehicle Recorder Division. According to the GPS Specialist's factual report, the airplane had completed six previous aerial applications that morning and was engaged in a seventh. During the last application, the airplane made four passes followed by shallow turns in the opposite direction. Altitude increased until the airplane reached 90° abeam the direction of application and then descended as it completed the turn on the opposite heading. The last data point was recorded at 15:03:57, indicating an altitude of 1,841 feet msl and groundspeed of 96 miles per hour, with the spray condition off. The measured diameter of the last turn from the impact point to a point abeam the impact point was approximately 750 feet; previous turns during the accident flight ranged from 600 to over 1,000 feet in diameter. The characteristics of the final turn did not greatly vary from earlier turns. The SATLOC manufacturer indicated that up to six seconds of data may be lost in volatile memory during a high impact.
Pilot Information
The pilot's autopsy attributed death to massive blunt trauma secondary to the crash. Toxicology testing revealed no evidence of carbon monoxide, ethanol, or drugs. Cyanide testing was not performed.
Additional Remarks
According to an Arkansas Air Tractor pilot familiar with this accident, agricultural pilots often make turns with flaps extended for greater stability. He noted that most Air Tractor pilots use 30° of flaps and keep speed above 100 knots, but some use 45° flaps with speeds as low as 80 to 90 knots during turns. The pilot also mentioned that some pilots disable the stall warning circuit breaker to prevent annunciation during turns, which he described as a bad combination that worsens with higher density altitude.