Introduction
On August 1, 2012, at 1430 central daylight time, an Air Tractor AT-502B, registration N5128U, sustained substantial damage during an attempted takeoff from Kifer Airport (LS83) in Newellton, Louisiana. The pilot, who was the sole occupant, was not injured. The aircraft was registered to Precision Air of Franklin, LLC, and operated by Delta Dusters, LLC, under 14 Code of Federal Regulations Part 137 as an agricultural application flight. Visual meteorological conditions prevailed, and the flight was not operating on a flight plan. The accident occurred at the start of the intended flight.
Event Narrative
The pilot reported loading 400 gallons of water and chemical into the hopper. He lowered the flaps for takeoff. During the takeoff roll, he monitored the engine temperature, which remained within normal limits, but did not check the torque, though it had been normal on previous flights that morning. The aircraft's tail rose approximately halfway down the runway, but the airplane was unable to become airborne. It departed the end of runway 24, a 2,750-foot by 75-foot asphalt strip, struck a road embankment, and continued rolling about 600 feet into a cotton field. The impact resulted in substantial damage to the wings and empennage. The pilot reported no preaccident mechanical malfunctions or failures.
Examination
Federal Aviation Administration inspectors examined the aircraft's electric flap actuator jackscrew. It was run out approximately 2.5 inches, indicating the flaps were set at 20 degrees. The airplane flight manual stated that takeoffs with a full chemical hopper load from a short field should be made with a 10-degree flap deflection, and it did not authorize takeoffs with flaps extended beyond 10 degrees.
Weight and Performance
The pilot reported an operating weight of 10,283 lbs, with a maximum gross weight of 10,480 lbs. The aircraft manufacturer's documentation specified a maximum certificated takeoff weight of 8,000 lbs. However, regulations and FAA guidance allow agricultural operators of restricted-category airplanes to operate at weights exceeding the maximum certificated weights. In accordance with Civil Aeronautics Manual 8 and Advisory Circular 20-33B, the manufacturer demonstrated operations at 9,400 lbs. The guidance permitted operations of the AT-502B at weights up to 31 percent above the certificated takeoff weight (10,480 lbs), provided the operator performed a flight check confirming safe flight characteristics at that weight.
The flight manual noted a takeoff distance required to clear a 50-foot obstacle of about 2,800 feet. This distance was applicable to a departure from a hard surface runway at a gross weight of 8,000 lbs with 10 degrees of flaps, at sea level and an ambient temperature of 35 degrees Celsius. The manual did not contain takeoff data for weights or flap settings exceeding 8,000 lbs or 10 degrees, respectively. The manufacturer did not recommend attempting takeoffs with more than 10 degrees of flap.
Weather Conditions
At 1453, the surface weather observation at Vicksburg Tallulah Regional Airport, about 25 nautical miles northeast of the accident site, reported wind from 200 degrees at 6 knots, visibility 10 miles, few clouds at 4,700 feet, temperature 36 degrees Celsius, dew point 24 degrees Celsius, and altimeter 29.93 inches of mercury. Calculated density altitude was 2,765 feet.