History of Flight
On February 26, 2018, about 1718 central standard time, an Air Tractor Inc. AT-802A, registration N581LA, was substantially damaged when it impacted trees and terrain near Greenwood, Mississippi. The commercial pilot was fatally injured. The airplane, owned by Ag Concepts Inc., was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. Visual meteorological conditions prevailed, and no flight plan was filed. The accident flight originated sometime after 1706 from the operator's airstrip in Morgan City, Mississippi.
According to the mixer/loader, the pilot was scheduled to conduct applications to two fields, each requiring three loads of chemicals. Data from the onboard GPS receiver showed three flights and multiple spray passes to the first spray field, located about 3 nautical miles east-northeast of the operator's airstrip. These flights occurred between 1548 and 1701, when the pilot returned to the airstrip. The accident flight was not recorded. The loader indicated that, before departing on the accident flight, both fuel quantity gauges showed half capacity. He stated that the pilot had not surveyed the application field before this flight but had sprayed it "hundreds of times" previously.
A witness about 1 nautical mile east-southeast of the accident site, while looking west through a gap in trees, noticed an airplane making passes from east to west. He then heard two nearly simultaneous "loud/hard" sounds, similar to dynamite, with the second louder than the first. Another pilot-rated witness, located about 1.7 nautical miles west-southwest of the accident site, heard an airplane flying from the Morgan City area. He reported that the airplane flew near him and then eastward, consistent with a spray pass, before he heard the impact sound. He estimated the airplane's altitude between 200 and 300 ft and heard no unusual sounds from it. There were no known eyewitnesses to the impact sequence.
Personnel Information
The 36-year-old pilot held an airline transport pilot certificate with airplane single- and multi-engine land ratings and commercial privileges for airplane single-engine sea. He also held a flight instructor certificate with airplane single- and multi-engine and instrument airplane ratings. He held a first class FAA medical certificate with no limitations, issued August 21, 2017, and reported 12,500 total flight hours, with 500 hours in the previous 6 months. Hired as a contract pilot by the operator in February 2013, he became the company's chief pilot in early 2015. According to company records dated January 22, 2016, he indicated 500 hours in the Air Tractor AT-802A, all in the previous 12 months. The manager and loader reported no health issues and noted the pilot was wearing his helmet and shoulder harness before departure.
Aircraft Information
The single-seat, low-wing airplane, serial number 802A-0581, was manufactured in 2015. It was powered by a Pratt & Whitney Canada PT6A-65AG engine, rated at 1,220 shaft horsepower, and equipped with a 5-blade, reversing, feathering Hartzell HC-B5MP-3F/M11276NS propeller. The last inspection was an annual inspection on January 26, 2018.
Meteorological Information
At 1653, a surface observation at Greenwood-Leflore Airport, about 9 nm east-southeast of the accident site, reported wind from 020° at 5 knots, 10 miles visibility, temperature 19°C, dew point 6°C, and altimeter setting 30.24 inches of mercury. A witness near the accident site reported wind from the northwest at 6 mph. Sunset occurred at 1755, and at the accident time, the sun's azimuth was about 246° true north with an elevation of about 19°.
Wreckage and Impact Information
Examination of the accident site revealed damage to a tree east of the site, about 40 ft above ground level, consistent with the airplane in a left bank of less than 30° at impact. A 17-ft-long tree limb with 2-inch diameter branches was found in a ditch beneath the tree. Debris including an LED strobe light portion, damaged tree limbs, navigation light lens, and housing of an LED navigation light were found east of the tree, while sections of the right spray boom, right wingtip, sheared rivets, wingtip fiberglass with blue primer, cut and broken tree limbs, and a brake line strap were found west of the tree. An impact crater with sections of overhead turn windows, light bar, hopper lid, windshield frame, two propeller blades, and hopper auger was about 515 ft west of the tree. A continuous ground scar about 176 ft long on a magnetic heading of 290° was noted between the crater and the inverted airplane, which came to rest on a magnetic heading of 332°. The left wingtip was found on the right side of the debris path.
Flight controls (ailerons, elevators, rudder) remained attached or were found nearby, with no evidence of preimpact failure or malfunction. Both wing flaps were symmetrically retracted. The right horizontal aft spar attachment was fractured in tension overload. The vertical stabilizer and upper rudder were displaced aft, with the vertical stabilizer crushed aft and the rudder compressed vertically. Both wings remained attached, exhibiting impact damage; the right wing had a semicircular depression from tree contact. All boom hangers were present. There was no evidence of aileron jamming despite denting on the right aileron leading edge.
The cockpit was fragmented; the dump handle was in the aft and locked position. The control stick was damaged but not fractured. All five restraint straps and airbag hoses were cut. The instrument panel separated from the airplane, and several instruments detached. The engine power lever was near idle, propeller lever in feather, fuel condition lever in RUN, rudder trim at full-nose-right, and elevator trim neutral (takeoff). Both spray booms were fragmented; one right boom section had a 2-inch contact mark from tree contact. The hopper door was closed and locked.
The engine separated from the airframe and rested near the main wreckage. The propeller and reduction gearbox separated, with only one blade secured to the hub; all blades were accounted for. The reduction gearbox had fractured second stage carrier webs consistent with high torsion overstress, with no preexisting cracks. Four propeller blades had aft bending, one slight forward bend. No preimpact failure or malfunction was found in the engine or propeller.
Medical and Pathological Information
A postmortem examination by the Office of the State Medical Examiner, Pearl, Mississippi, attributed death to multiple blunt trauma. Toxicology testing at the FAA Forensic Sciences Laboratory detected no carbon monoxide, volatiles, or tested-for drugs; cyanide testing was not performed.
Tests and Research
Previous roll rate testing by Air Tractor on an AT-802 (same wings and ailerons as AT-802A) at 9,300 pounds, engine torque 2,300 ft-lbs, propeller 1,650 rpm, and 90 mph showed a roll rate of 29° per second. Calculations for speeds of 170, 180, and 190 mph gave roll rates of 103°, 116°, and 129° per second, respectively, assuming steady-state maneuvers and not aggressive maneuvers like snap rolls.
Correlation of impact creases on ailerons to an exemplar AT-802A indicated the right aileron had deflections of 14.8° up (inboard) and 11.4° up (outboard); the left aileron had 3.7° up (inboard) and 11.3° down (outboard). Simultaneous up and down deflection of the left aileron is not possible, and an 11.3° down deflection of the left aileron corresponds to 12.5° up deflection of the right aileron. Total design travel for each aileron is 17° up and 13° down.