NTSB Factual Report

On June 10, 2014, about 2041 central daylight time, an Air Tractor AT-301 airplane, N8564S, was substantially damaged when it impacted terrain shortly after takeoff at Winner Regional Airport (ICR), Winner, South Dakota. The commercial pilot was not injured. The airplane was operated by Semper Fi Aviation, LLC, under the provisions of Title 14 Code of Federal Regulations Part 137 without a flight plan. Day visual meteorological conditions prevailed for the local agricultural application flight that was departing at the time of the accident.

The pilot stated the airplane weighed about 5,000 lbs after being loaded with 200 gallons of insecticide and 90 gallons of fuel. The pilot reported there were no anomalies with the engine or the wheel brakes during his taxi and before takeoff runup. The takeoff was made on runway 31 (4,500 ft by 75 ft, concrete) and liftoff was achieved with about ½ of the runway remaining. The pilot reported that shortly after liftoff, at an altitude of 3-5 ft above the runway, he heard a loud bang and the airplane began to yaw left. The airplane descended and bounced off the left side of the runway. The pilot stated that he increased aircraft pitch to gain altitude, but the airplane entered an aerodynamic stall and the left wing dropped. As he attempted to dump the load of insecticide, the airplane nosed over and impacted the ground alongside the runway. The airplane subsequently came to rest inverted. The pilot was able to exit the airplane uninjured through the left-side window.

A postaccident examination was completed by a Federal Aviation Administration (FAA) airworthiness inspector. Examination of the runway surface revealed a tire skid mark that began about 1,000 ft from the departure end of runway 31. The skid mark was consistent with the tread width of a main landing gear tire. The wavy tire marking continued about 30 ft until it departed the left runway edge. A second tire skid mark, about 10 ft right of the wavy tire marking, began about 10 ft from the left edge of the runway. The airplane exited the left runway edge about 970 ft from the end of the runway and entered a grass field. There were at least 12 propeller strike marks in the ground between where the airplane departed the left edge of the runway and main wreckage. The main wreckage was in a grass field about 100 ft left of the runway edge and about 750 ft from the end of runway 31. The airplane was inverted and was facing back toward the runway on a southeast heading. There were propeller strike marks and oil-covered grass immediately preceding the main wreckage. The airplane sustained substantial damage to the fuselage, both wings, and the empennage. The aft fuselage was crumpled immediately forward of the horizontal stabilizer. The empennage remained attached to the aft fuselage. The vertical stabilizer and rudder were crushed when the airplane nosed over. The elevator remained attached to the horizontal stabilizer. The flaps and ailerons remained attached to the wings. Flight control continuity was confirmed at the accident site. The right landing gear and tailwheel remained attached to the fuselage. The left landing gear leg had separated from the fuselage; however, visual examination of the attachment fittings revealed signatures consistent with overstress separation. The engine had separated from the airframe and was found adjacent to the fuselage under the left wing. The propeller remained attached to the engine. An examination of the engine revealed impact-related damage and no mechanical malfunctions. The No. 5 exhaust valve body was fractured, its exhaust valve cover was deformed and crushed inward, and the valve cover attachment studs were bent. The observed damage to the exhaust valve body was consistent with impact-related damage and not a mechanical malfunction. The postaccident examination revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation during the flight.

At 2053, about 12 minutes after the accident, the ICR weather observing system reported wind from 130° at 8 knots, 10 miles surface visibility, clear sky conditions, temperature 21°C, dew point 13°C, and an altimeter setting of 29.77 inches of mercury. Further review of recorded wind data revealed a southeasterly wind of 8-13 knots during the 3 hours before the accident and the hour following the accident. The surface wind at the time of the accident, from 130° at 8 knots, had resulted in a direct tailwind during takeoff. In his accident report, the pilot reported that the surface wind was 130° at 2 knots.

The FAA Pilot's Handbook of Aeronautical Knowledge, states that a normal takeoff is when an airplane is headed into the wind. The effect of a tailwind requires an airplane to achieve a greater groundspeed and to use additional runway length to attain the airplane's liftoff speed during takeoff. If a pilot attempts liftoff below the specified airspeed an airplane could be difficult to control, have a very low initial rate of climb, or enter an aerodynamic stall. Additionally, if an excessive angle of attack is used to achieve a premature liftoff, the airplane may not be able to climb out of ground effect.

NTSB Probable Cause

The pilot's improper decision to attempt a takeoff with a tailwind and his failure to achieve the proper airspeed for liftoff, which resulted in the airplane exceeding its critical angle of attack and entering an aerodynamic stall shortly after liftoff.