Shaw, MS, USA
N247LA
AIR TRACTOR INC AT 402A
The pilot was departing on an agricultural application flight from a 2,300-ft-long runway. When the airplane reached the end of the runway, the pilot could "feel that the airplane did not want to fly." The pilot extended the flaps, then dumped the spray load that was in the airplane’s hopper tank in an attempt to become airborne; however, the airplane continued off the end of the runway, crossed a drainage ditch, and came to rest in a bean field, resulting in substantial damage. The airplane’s hopper was loaded with about 3,400 lbs of a mixture of herbicide and other chemicals, which exceeded the hopper’s placarded limitation of 3,250 lbs. The airplane’s estimated weight at the time of the accident was 1,864 lbs higher than the manufacturer’s published gross weight and about 264 lbs more than field experience showed could be carried safely with adequate margins of performance and structural strength. Calculations by the airplane manufacturer using takeoff data of a similar airplane from a previous company test program indicated a takeoff ground roll distance of about 2,322 ft. Given the density altitude about the time of the accident, the airplane’s takeoff distance would have been increased by 24%, and there would have been an 18% decrease in its rate of climb. No preimpact failures or malfunctions were discovered that would have precluded normal operation. Despite the numerous indicators that the takeoff conditions were marginal, such as the high air temperature, high gross weight, and a short runway, the pilot failed to evaluate the conditions that existed in relation to the performance capability of the airplane.
On August 21, 2017, about 1830 central daylight time, an Air Tractor AT-402A airplane, N247LA, was substantially damaged when it was involved in an accident in Shaw, Mississippi. The pilot received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The airplane impacted terrain during takeoff from Tapley Airport (1MS0), Shaw, Mississippi. The pilot reported that he had a full load of herbicide onboard in the hopper tank. After applying engine power for takeoff, he noticed that the instruments were indicating maximum engine torque and maximum engine rpm. When the airplane reached the end of the paved portion of the runway, he could "feel that the airplane did not want to fly." He then lowered the wing flaps and "pushed the throttle to the stop," but the airplane was still not flying. As he approached the end of the runway, he dumped the load of herbicide. As the airplane continued off the end of the runway, the left wing "went down," and the right wing "went up" as the airplane crossed a drainage ditch. The airplane then slid, spun around, and came to rest in a bean field. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the airplane was substantially damaged. All four propeller blades were bent about mid-span, the aft fuselage was bent and torn almost in half, the right main landing gear wheel had separated from its mounting position and the gear leg was bent inward, the tail wheel landing gear assembly had separated from its mounting position, and the right and left wings were bent, twisted, and displayed visible wrinkling of the upper surfaces. No preimpact failures or malfunctions were discovered with the airplane or engine. The pilot advised that, before the accident flight, he had been flying all day and had previously taken two loads of the same mixture and quantity in the hopper tank with no indication of any problems. Review of weight and balance information submitted by the pilot indicated that he had calculated the weight of the load in the hopper (which he listed as consisting of Gramoxone, sodium chlorate, and water) at 3,350.70 lbs, 100.7 lbs higher than Air Tractor’s placarded hopper limit of 3,250 lbs. He had also calculated the takeoff weight to be 8,543.20 lbs, which was 1,543.20 lbs more than Air Tractor’s published maximum gross weight of 7,000 lbs. Review of photographs taken by the FAA revealed that the hopper contained 4 gallons of Gramoxone, 48 gallons of sodium chlorate, 4 gallons of fungicide, and 1 gallon of surfactant. Calculations by Air Tractor indicated that the load in the hopper at the time of the accident weighed about 3,400 lbs, which was about 150 lbs higher than the placarded limit of 3,250 lbs. Calculations also revealed that the airplane’s total takeoff weight was about 8,863.5 lbs, which was about 1,863.5 lbs more than the manufacturer’s published gross weight. At the time of certification of the airplane design, the Civil Air Regulations (CARs) and Civil Aeronautics Manual (CAM) were in effect. Chapter 8 (CAR 8/CAM 8), provided for the type and airworthiness certification of aircraft built or modified for special purposes (for example, crop dusting, seeding, and spraying) and eliminated the “equivalent level of safety” provision for restricted category aircraft. CAM 8 also set forth acceptable procedures and practices for guidance for those airplanes that were certificated under CAR 8 and allowed the use of CAM 8 in approving gross weight increases, if CAR 8 was used as part of the certification basis. Published guidance by Air Tractor advised that the AT-402A/402B was certificated by the manufacturer for a gross weight of 7,000 lbs starting with serial number 402A-1021; however, under the provisions of CAM 8, the operator could select its own maximum operating weight, and field experience showed that operating weights up to 8,600 pounds could be carried safely with adequate margins of performance and structural strength. Air Tractor did not publish weight and balance data above the certificated gross weight of 7,000 lbs. The closest weather reporting station was located at Cleveland Municipal Airport (RNV), Cleveland, Mississippi, 10 nautical miles north of the accident site. At 1835, the weather report included wind from 280° at 4 knots, 10 miles visibility, scattered clouds at 4,800 ft, temperature 33°C, dew point 24°C, and an altimeter setting of 30.04 inches of mercury. Density altitude was calculated as about 2,472.8 ft around the time of the accident. Calculations by Air Tractor using takeoff data of a similar airplane from a previous company test program indicated that the calculated ground roll distance on a paved surface at 35ºC at sea level was about 2,322 ft. Review of an FAA Koch Chart, which depicts the effects of density altitude on takeoff and climb performance, indicated that, given the atmospheric conditions present at the time of the accident, takeoff distance would have been increased by 24%, and there would have been an 18% decrease in rate of climb.
The pilot’s decision to attempt takeoff at high gross weight, in high density altitude conditions, and with insufficient runway length. Contributing to the accident was the pilot’s inadequate preflight planning.
Source: NTSB Aviation Accident Database
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