N1016GAir Tractor AT-402 · 1989

On July 29, 2016, at 0914 central daylight time, an Air Tractor AT-402 airplane, N1016G, collided with power lines and impacted terrain near Sac City, Iowa. The commercial rated pilot was fatally injured and the airplane was destroyed. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident and no flight plan had been filed. The airplane departed Arthur N Neu Airport (CIN), Carroll, Iowa, at 0902 and was spraying in the area of Sac City Municipal Airport, (SKI), Sac City, Iowa.

The pilot's ground crewman stated that he met the pilot at CIN about 0830 and loaded the airplane with 375 gallons of liquid applicant and 130 gallons of fuel and noted that the airplane was almost fully loaded and was within the specified limitations. He added that the pilot did not seem concerned about him running late that morning. The pilot did not seem rushed or nervous, which was unusual for him, and he also seemed complacent about the flight. He has always known the pilot to circle above a field and scan for hazards before starting an aerial application flight. He described the area near the accident site as a "wire farm" because of the amount of power lines present.

The responding Federal Aviation Administration (FAA) inspector reported that the airplane impacted a corn field one-mile south of SKI. Power lines were found downed near the accident site.

A review of the pilot's logbooks and flight data revealed that he had accumulated 1,746.2 total flight hours and 414.1 hours the Air Tractor AT-402. The pilot had flown 114.5 hours in the preceding 30 days, all of which were in the accident airplane.

The main wreckage was located in a corn field about one mile south of SKI. The field being treated was north of the accident site. A large set of power transmission lines ran east to west along the southern border of the target field (figure 1). The power lines and supporting tower structures were 80 to 90 ft tall and the power lines sagged in between each tower. A farm house and several farm buildings were located south of the power lines.

Figure 1 – Google Earth overview of the accident location and flight path

The wreckage debris path was oriented north to south and featured a swath cut through the mature corn, which continued to the main wreckage. The main wreckage was about 900 ft south of the power lines and 75 ft south of the initial impact area. There was a smell consistent with jet fuel and agricultural chemical around the site and the ground was damp. There was no evidence of fire. The debris path was relatively straight and began with the entire rudder on a gravel road underneath the power lines. A portion of the vertical stabilizer was found next in the debris path on the north side of the farm house. Next was the swath of cut corn and the initial ground impact point, which included debris from the bottom of the airplane (figure 2).

Figure 2 – Main wreckage and debris path

The forward wall of the cockpit was part of the hopper structure and was laying adjacent to the fuselage. The instrument panel remained mostly intact and undamaged. The Hobbs meter mounted in the instrument panel showed 7,008.3 hours. The center fuselage between the firewall and the cockpit was crushed. The fuselage was bent, twisted left, and came to rest next to the left wing. The horizontal stabilizers and elevators exhibited minimal damage and remained attached to the aft fuselage. The lower portion of the vertical stabilizer remained attached to the empennage and exhibited a jagged horizontal cut at the top (figure 3).

Figure 3 – Left rear view of the main wreckage

The right and left wings remained connected at the center splice joint. There were no prominent impact marks on the leading edge or upper surface of the wings. The bottom of the wings exhibited impact damage. The outboard section of the right flap was bent under the inboard half of the flap. The left and right ailerons and flaps remained installed in their respective positions. Both wing fuel tanks were breached at the inboard ends. The fuel caps were in place and secure.

The elevator controls were impact damaged, but continuous from the control stick to the elevators. The elevators were attached to the horizontal stabilizers at the hinge points. The rudder pedals remained attached to their pivot points with the rudder cables and adjustment brackets in place. The rudder cables were continuous to the aft fuselage where they were found separated and exhibited signs of tension overload. About 15 inches of the aft end of the rudder cables remained attached to the rudder and exhibited signs of tension overload. The horn plate remained installed on the bottom of the rudder, but was bent into a "U" shape.

The control stick remained attached to the floor-mounted torque tube which remained attached to the left aileron control tube through the upper pushrod and fuselage bellcrank. The trailing edge push rod was bent and separated near the inboard end and the rod end bearing remained attached to the bellcrank. From the push rod separation, the controls were continuous to the left aileron control horn. From the cockpit torque tube, the right aileron controls were continuous through the upper pushrod and fuselage bellcrank. From the fuselage bellcrank, the controls were continuous to the right aileron, except the inboard end of the pushrod that was separated where the wing was pulled away from the fuselage. The flap actuator was found in the retracted position. The trim system sustained impact damage but remained continuous and attached at all connections.

The main landing gear separated from the fuselage. The left wheel and gear spring were found near the initial impact point in the debris path. The right gear spring was found near the left wingtip of and the right wheel on the right side of the fuselage. The tailwheel assembly separated from the tail spring.

The four-point pilot restraint system remained fastened and the lap belt had been cut by first responders on the left side of the buckle. The shoulder harness straps had separated from the attachment points at the lap belt. Slight fraying of the shoulder harnesses was noted near the top of the seatback with no evidence of overstress failure.

The engine sustained impact damage and remained attached to the respective engine mounts. The engine exhaust housing was impact damaged. The engine had separated at the "C" flange, revealing the interstage baffle and the power turbine wheel. The power turbine had damage to all blades and the interior of the engine showed significant rotational scoring signatures. The propeller hub and spinner remained attached to the engine flange. Only one propeller blade remained attached to the propeller hub. The two other blades were not found at the scene. The FAA Inspector stated that the two missing blades had been present in the debris field on his previous visit to the scene on the day of the accident.

The airplane was equipped with a single curved acrylic wind screen. There was an aluminum bar in front of the wind screen and a deflector cable connected the top of the canopy to the top of the vertical stabilizer, which were installed to add protection against wire strikes.

The aluminum bar was found separated from its lower base in the debris field and was bent to the left into a rough V-shape with an inside angle about 45°. At the upper end, the tubular support structure had separated from the cockpit structure and remained attached to the bar. A 6 ft piece of the deflector cable remained attached to the top of the bar. The bar had a chamfered edge on the right side that ran the entire length of the bar. The cable that was attached to the bar exhibited abrasion and damage (figure 4).

Figure 4 – Damaged wire strike protection bar

The upper right corner of the cockpit structure exhibited cylindrical abrasions and damage. Scratches and front to back damage was noted on the top of the canopy where the aftermarket GPS antenna had separated. The top 15 inches of the vertical stabilizer was separated and exhibited a jagged horizontal cut from front to back with impact damage on the leading edge near the cut; a portion of the deflector cable remained attached to the top. The rudder exhibited a 4-inch gouge into the vertical hinge line, which lined up with the cut of the horizontal stabilizer. The rudder horn remained attached to the rudder and was distorted about 90° down, and the aft ends of the rudder control cables remained attached.

GPS Device Downloads

A Satloc M3 Bantam GPS and a Garmin aera 510 GPS were found in the wreckage and were sent to the NTSB Recorders Laboratory for download. The combined data from the two devices was plotted on Google Earth (figure 1 and 5). The red flight path originates from the southeast and continues directly to the target field without any evidence of an initial circling pass. The areas of green represent the flight path when the airplanes spray function was on. The white lines represent the power lines that cross the flight path west to east.

Figure 5 – Google Earth overlay of accident flight path

Power Line Markers

A few round, orange objects, similar to high visibility power line markers, were observed on the road near the accident site by a nearby landowner. The power company reported that no markers were installed on the power lines. The power company could not find any documentation to prove there were high visibility power line markers installed prior to the accident. As a result of the accident, the power company installed several high visibility power line markers on the new power lines.

The Iowa Office of the State Medical Examiner, Ankeny, Iowa, completed an autopsy on the pilot and the cause of death was multiple blunt force injuries. The FAA's Bioaeronautical Sciences Research Laboratory conducted toxicology testing, which was negative for ethanol and drugs.