N502KJAir Tractor AT-502B · 2012

On July 25, 2020, about 1136 mountain daylight time, an Air Tractor AT-502B airplane, N502KJ, was substantially damaged when it was involved in an accident near Grant, Nebraska. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 agricultural flight.

According to data downloaded from the airplane’s Satloc GPS guidance system, at 1108, the flight departed Grant Municipal Airport (GGF), Grant, Nebraska, and proceeded south toward the field to be sprayed. After arriving over the field, the pilot completed several orbits of the field before he began spraying using a series of east/west flightpaths, as shown in figure 1.

As the flight progressed, the airplane made a climbing left turn after each spray pass, the frequency of spray passes increased, the elapsed time between spray passes decreased, and the maximum altitude achieved between spray passes increased, as shown in figure 2. During the final 5 minutes of the flight, the airplane's groundspeed was 160-165 mph during each spray pass and 104-120 mph while in the turn between spray passes; the airplane routinely climbed 450-520 ft after each spray pass.

At 1136:48, the final track point recorded the airplane in a climb on a west heading near the end of a spray pass at the northern edge of the field being sprayed. The final track point was about 1/4 mile northeast of the accident site. The airplane's final recorded groundspeed and estimated altitude above ground level were 152 mph and 136 ft, respectively. The Satloc GPS guidance system has a 6-second delay between data acquisition and when data are saved to non-volatile memory and, as such, the final moments of the flight were not recorded.

Another agricultural pilot, who was spraying a nearby field at the time of the accident, reported that he maintained radio contact with the accident pilot throughout most of his flight and that he saw the accident airplane consistently climb 450-500 ft after each spray pass. He stated that the climbs between spray passes were higher than required for an aerial-application flight. The last time he saw the accident airplane, it was flying to the west in a climb before it rolled right-wing-down into a 90°-100° bank with a 10°-12° nose-up pitch attitude. The accident airplane was turning toward north when it pitched down through the horizon, consistent with a lazy eight flight maneuver. The pilot lost sight of the accident airplane when he turned his airplane after a spray pass. The pilot was unable to reestablish radio contact with the accident pilot and continued to spray his assigned field. The pilot subsequently saw the airplane wreckage in the cornfield directly west of the field that the accident pilot had sprayed, as shown in figure 3.

Figure 1. GPS Ground Track Data

Figure 2. Altitude, Groundspeed, and Ground Track Angle Data

Figure 3. Aerial Photo Taken of Accident Site (Source: Aurora Cooperative Elevator Company)

The operator’s chief pilot reported that he previously observed the pilot use “aggressive” flying techniques during an evaluation flight and told the pilot that a hammerhead maneuver between spray passes was not acceptable during agricultural flights. The chief pilot told the pilot that turns between spray passes should consist of three separate phases (field departure, procedure turn, and field reentry) and should not be combined into a single maneuver. At the recommendation of the chief pilot, the pilot agreed to review a National Agricultural Aviation Association endorsed training video, Turn Smart, that discussed and demonstrated the proper turning techniques to be used during agricultural flights.

The Air Tractor AT-502B airplane flight manual (AFM) states that spray passes should be flown at 130-140 mph to ensure proper spray penetration into the crop, and an abrupt pull-up at the end of a spray pass should be avoided to maintain adequate airspeed during the turn between spray passes. The AFM states that a maximum altitude loss of 220 ft is expected during a recovery from a wings-level aerodynamic stall at a gross weight of 8,000 lbs; however, an aerodynamic stall during an uncoordinated turn will result in a sharp decrease in airplane pitch and a significant loss of altitude. The AFM prohibits all aerobatic maneuvers, including spins.

The Air Tractor AT-502B airplane flight manual (AFM) states that spray passes should be flown at 130-140 mph to ensure proper spray penetration into the crop, and an abrupt pull-up at the end of a spray pass should be avoided to maintain adequate airspeed during the turn between spray passes. The AFM states that a maximum altitude loss of 220 ft is expected during a recovery from a wings-level aerodynamic stall at a gross weight of 8,000 lbs; however, an aerodynamic stall during an uncoordinated turn will result in a sharp decrease in airplane pitch and a significant loss of altitude. The AFM prohibits all aerobatic maneuvers, including spins.

The accident site was in a cornfield about 8.7 miles south-southeast of GGF. An onsite examination was conducted by a Federal Aviation Administration (FAA) inspector and an Air Tractor accident investigator. Based on the damage to the cornstalks immediately surrounding the wreckage, the airplane impacted terrain in an estimated 45° nose-down flightpath angle. There were no discernable ground impacts or debris path preceding the wreckage. The airplane wreckage was found upright with significant impact damage to the forward fuselage and the leading edge of both wings. The fuselage was oriented on an east-northeast heading.

Flight control continuity could not be established due to damage; however, all observed separations were consistent with impact-related damage. The rudder control cables were continuous from the rudder pedals to the rudder control horns. The aileron drooping system was continuous from the flap torque tube to the aileron bellcrank support assembly. The flap actuator measured 2.875 inches and was consistent with the flaps extended about 20° at impact. The aft fuselage and empennage exhibited minor impact-related damage. Both landing gear legs separated from the fuselage during impact. Both wing fuel tanks ruptured during impact and the odor of Jet-A fuel was present at the accident site. The engine and the propeller were found buried about 3 ft below ground level. The propeller exhibited various impact-related blade damage including a separated blade, blade twist, and tip curl that was consistent with engine operation at impact.

An autopsy of the pilot was performed by Western Pathology Consultants, Scottsbluff, Nebraska, which identified the cause of death as blunt force trauma with the manner of death an accident. No significant natural disease was identified during the autopsy. Toxicological testing, completed by the FAA Forensic Sciences Laboratory, detected ethanol at 0.058 g/dL in cavity blood, 0.128 g/dL in muscle tissue, and 0.036 g/dL in brain tissue. N-propanol and methanol were detected at low levels in cavity blood. N-butanol was detected at low levels in cavity blood and muscle tissue.

Ethanol is a type of alcohol that is the intoxicating substance of beer, wine, and liquor, and, if consumed, can impair judgment, psychomotor performance, cognition, and vigilance. FAA regulation imposes strict limits on flying after consuming ethanol, including prohibiting pilots from flying with a blood ethanol level of 0.04 g/dL or greater. However, consumption is not the only possible source of ethanol in postmortem specimens. Ethanol can also be produced by microbes in a person’s body after death. Postmortem ethanol production can affect multiple specimens from the same individual to different degrees, which can result in the specimens having significantly different ethanol levels from one another.

N-propanol and n-butanol are alcohols that can be produced by microbes in a person’s body after death. Methanol is wood alcohol; it occurs naturally in the body at very low levels, is present in some foods and drinks, and is a solvent in a variety of industrial products. At low levels, n-propanol, n-butanol, and methanol are not impairing.