NTSB Factual Report

HISTORY OF FLIGHT:

On June 26, 1993, at 1420 central daylight time, an Air Tractor AT-502, N1504Q, maneuvering near Petronila, Texas, was destroyed when it impacted the terrain. The commercial pilot sustained fatal injuries. Visual meteorological conditions prevailed throughout the area for the local aerial application flight.

During interviews, conducted by the investigator in charge with witnesses and the operator, it was revealed that the pilot started working at 0730 and had flown five to six hours by 1400. For this run, the airplane was serviced with 125 gallons of fuel and the hopper carried 130 gallons of liquid composed of cottonseed oil mixed with Guthion in a 3:1 ratio. The airplane had departed the private airstrip at 1400 to spray 261.9 acres of cotton. The airplane was observed during several swath runs and turn around maneuvers as it was making steeper turns and climbing higher with each turn around. At 300 feet above the ground, the airplane was observed rolling to an inverted position. The witness stated that the pilot started to pull the airplane out of the maneuver but did not have enough altitude and the airplane impacted in wooded terrain on the edge of a lake.

WRECKAGE AND IMPACT INFORMATION:

The airplane came to rest on a measured magnetic heading of 045 degrees and was intact except for several pieces of the windshield, engine cowling, and hopper cowling, which were 35 feet forward of the main wreckage. One propeller blade, dug from the mud, was separated from the propeller shaft. Blades attached to the hub were bent and twisted with the tip of one blade separated. The landing gear was imbedded level with the fuselage in the muddy terrain with no physical evidence of forward motion. The engine and airframe exhibited vertical crushing with the structural frames bent, broken, and buckled downward and forward. The empennage and wings were buckled downward with the structural tubings of the stabilizers buckled in a vertical plane. Wing spars were buckled and twisted. Engine mounts were bent, twisted, and buckled downward. Several turbine blades were located in the engine exhaust. One tree five feet from the trailing edge of the left wing had several broken branches, and broken tree branches were located on the upper surface of the left wing. The flap actuator was extended 2.25 inches and the flap motor had separated.

Deformation downward and to the right was noted in the pilot's seat and the right sidebrace was broken. The left seat support was pulled forward from the bulkhead about 1.5 inches. The shoulder harness, with the stitching pulled in tension at the buckles, remained anchored to its structural attachment; however, it pulled through the guide in the aft bulkhead.

Power quadrant control had continuity. Flight control continuity was established to the rudder and the elevators. On the rudder/aileron interconnect, the cable on the left side separated at the wing root. The cable on the right side had continuity to the point where the turnbuckle had separated. Right aileron continuity was present thru where the control torque tube separated at the wing root. The left aileron control tube was intact from the wing root to the bellcrank; however, the tube extending to the aileron was separated.

Physical evidence of fuel was present at the site with the fuel lines ruptured at the tanks.

MEDICAL AND PATHOLOGICAL INFORMATION.

The autopsy was performed by the Nueces County Medical Examiner Office in Corpus Christi, Texas. Toxicological findings were negative.

ADDITIONAL INFORMATION:

Examination of the engine on August 11, 1993, revealed that rotational damage was noted on the first stage of the compressor wheel and the compressor shaft was separated. There were 45 degree bending folds on the outer shroud of the hot section which showed heat deformation. There was a shear brake inside the plenum and forward of the last stage wheel.

The airplane was released to the owner following the investigation.

NTSB Probable Cause

FAILURE OF THE PILOT TO MAINTAIN SUFFICIENT AIRSPEED, WHILE MANEUVERING, WHICH RESULTED IN AN INADVERTENT STALL. A FACTOR RELATED TO THE ACCIDENT WAS: HIS LACK OF ALTITUDE FOR RECOVERY FROM THE STALL.