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N1508X accident description

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Tail numberN1508X
Accident dateAugust 24, 1993
Aircraft typeAir Tractor AT-402
LocationLa Barre, LA
Additional details: None

NTSB description

HISTORY OF THE FLIGHT

On August 24, 1993, about 1920 central daylight time, an Air Tractor AT-402, N1508X, was destroyed when it impacted the ground while maneuvering near La Barre, Louisiana. The airplane, flown by a commercial pilot, was on a local aerial application flight. There was no flight plan filed and visual meteorological conditions prevailed throughout the area. The pilot received fatal injuries.

The airplane departed the operator's facility at the False River Airpark, at 1900, loaded with two hundred gallons of methyl parathion and permethrin. A search was initiated after the airplane failed to return and the wreckage was found in a sugar cane field at 2225. The accident site was located about three quarters of a mile east of the first field that the pilot was to have sprayed. Flags found at the spray field indicated that he had finished application on the field and that the field had been sprayed using east/west passes. The second field that was to have been sprayed was located about 3 miles north of the first.

There were no witnesses to the accident. One witness saw the airplane flying en route to the first field and another observed it from a distance performing an aerial application type turn in the vicinity of the first field. The accident time was estimated by the operator based on the flags found at the field, the size of the field, and work experience.

PERSONNEL INFORMATION

The pilot's personal logs were not located during the investigation; however, the operator provided estimates as to his flight time, which included 6,480 hours of aerial application experience. Federal Aviation Administration records revealed that the pilot had indicated a total time of 7,450 hours at the time of his last medical examination on April 29, 1993. It was determined the pilot also owned an aerobatic Pitts Special that he flew during his off duty time.

AIRCRAFT INFORMATION

The airplane was certificated in the restricted category and had last received an annual inspection on August 22, 1993, at an undetermined total airframe time. The maintenance records indicated that a 2,203 hour engine had been installed in the airframe at the time of manufacture, along with a new propeller. The airplane was within weight and center of gravity limits both at takeoff and at the time of the accident. The airplane had been refueled with 160 gallons of Jet-A earlier in the day and had flown three loads for about two hours after the refueling.

COMMUNICATIONS

The pilot had radio contact with the operator's base station; however, at no time did he indicate he was experiencing a problem. No distress calls were monitored on any of the FAA frequencies.

WRECKAGE AND IMPACT INFORMATION

The airplane impacted in a sugar cane field in which the cane was about 7 feet tall on a measured heading of 084 degrees. The airplane's attitude at impact was 35 degrees right bank and 20 degrees nose down as evidenced by the measured angles of the cut sugar cane at the impact crater. The right wing tip was found separated in the immediate vicinity of the initial impact area. The main wreckage came to rest about 100 feet from the point of initial impact on a southerly heading.

All of the flight control surfaces remained attached and control continuity was established. The flight control cables and rods were bound. The fuselage and wings were distorted and deformed. The right wing was bent rearward and the wing center section was found separated from the fuselage. The right side of the fuselage, from aft of the engine to aft of the cockpit exhibited crush. The left wing and the empennage remained in place.

The engine was displaced downward and to the right and all of the engine control cables between the engine and the cockpit were pulled as a result. Clear fuel was found in the fuel filter bowl. The propeller was found about mid-point between the initial impact point and the main wreckage. It had separated immediately aft of the drive shaft flange. All three blades were found loose in the hub. All exhibited evidence of twist, curl, and chordwise striations and had gouges in the leading edges. One blade was missing a 2.5 inch piece at the tip which was not found. Examination of the tip separation surfaces did not reveal any evidence of progressive type failure. In addition, one blade exhibited a 10 inch long serrated gouge that ran from the root outboard. The source of the gouge was not determined. It was noted that there were no foreign wires at the accident site, nor were any wires present between the accident site and the field that had been sprayed. In addition, one tree was identified about mid-way between the field and the accident site which had separated branches and the appearance of having been struck. The tree was felled and examined. No evidence of either airplane or propeller strikes was found.

The seat was equipped with a four point restraint system. The shoulder harnesses were found adjusted evenly. The metal structure surrounding the harness guides was torn downward. All of the restraints remained attached to their respective anchors and the pilot was strapped into the seat, with the shoulder harness attached, when the rescue personnel arrived. The left vertical support of the seat was found pulled forward away from its bulkhead attachment and the seat was displaced downward. The pilot was seen to be wearing a helmet on departure. However, it was found laying in his lap with the chin strap snap closed when the rescue personnel arrived. The helmet retention strap adjustments could not be determined.

MEDICAL AND PATHOLOGICAL INFORMATION

An autopsy and toxicology studies were ordered. The autopsy was performed by the State of Louisiana Medical Examiner's Office in Baton Rouge. The toxicology studies were performed by the FAA Civil Aeromedical Institute in Oklahoma City. On the autopsy, there were findings of "mild biventricular dilation, hepatomegaly (enlargement of the liver) with mild fatty changes and congestion, splenomegaly (enlargement of the spleen) with mild congestion, and mild atherosclerosis involving the aorta and coronary arteries." There were no significant findings in the toxicology reports to include no pesticides in the blood.

TESTS AND RESEARCH

Engine Disassembly and Examination: The engine was examined at the facilities of Ryder/Aviall on September 15, 1993. The aft gearbox was separated at the shaft in the area of the inlet. Forty five degree folds, opposite the direction of rotation, were noted in the hot section area and both exhaust stacks were distorted and bent. The propeller shaft was separated about 1.5 inches forward of the nose case and the break was consistent with torsion and bending. The shafting was intact on the fuel control and the fuel pump and the fuel control drive rotated freely. Rub was noted on the faces and tips of the turbine blades and the blades were displaced forward. The internal shafts were found sheared torsionally. The burner can was found distorted and bent. The first stage compressor exhibited foreign object damage. The gearbox rotated freely and the gear train was intact and the bearings showed no evidence of heat distress. No evidence of pre-impact failure or malfunction was found during the examination.

Propeller Examination: The propeller was examined at the Hartzell facilities on February 7, 1994, with the FAA in attendance. The examination did not reveal any evidence of pre- impact failure or malfunction. The tear down report stated that evidence in the form of internal contact damage found during the disassembly indicated that the propeller blades were at 20 degrees pitch at the time of impact. It was the manufacturer's opinion that the propeller was not feathered and that the blade damage signatures indicated more than windmilling power.

ADDITIONAL INFORMATION

Wreckage Release: The wreckage was released to the owner's representative on October 4, 1993. All of the retained components and records were returned prior to the completion of the investigation.

(c) 2009-2011 Lee C. Baker. For informational purposes only.