HISTORY OF FLIGHT: On August 5, 1994, at 1528 central daylight time, a Grumman G-164B, N6804Q, was destroyed while maneuvering near Henderson, Louisiana. The commercial pilot received fatal injuries. Visual meteorological conditions prevailed for the local aerial application flight. During personal interviews, witnesses reported the pilot had started the work day at 0700. He departed with the first load at 0745 and completed two loads prior to lunch. No discrepancies with the airplane were reported and two additional flights were planned for the afternoon. Witnesses further stated that the pilot was going to spray several 20 acre sugarcane plots located to the north and south of a 480 foot communications tower, with antennas 494 feet above the ground. The airplane hopper was loaded with 300 gallons of chemical and the fuel tanks with 80 gallons of aviation fuel. The airplane departed the private grass airstrip at approximately 1445 for the spray run. Witnesses from vehicles on nearby Interstate Highway 10 (I-10) reported to local authorities that the airplane was tumbling end-over-end as it fell from the sky, hit the ground, and started to burn. The main fuselage came to rest in an inverted position in the center median of I-10. Witnesses assisted in the removal of the pilot, prior to the airplane being engulfed in flames. PERSONNEL INFORMATION: Witnesses reported that 1994 was the pilot's first spraying season with the conversion installation of the turbine engine. AIRCRAFT INFORMATION: Turbines, Inc. of Terre Haute, Indiana, records showed the PT6A-20 engine, S/N PCE21562, was overhauled with a hot section on September 13, 1991, and installed on N6804Q, on September 19, 1991. Complete operator maintenance records were not made available to the Safety Board. WRECKAGE AND IMPACT INFORMATION: Physical evidence of cable damage and yellow paint transfer was found on the tower guide cables. The airplane was painted yellow. Portions of the right wing and tail sections were found near the damaged cables. Numerous parts of the airplane were distributed in the sugarcane field. The fuselage and engine came to rest in an inverted position on a measured magnetic heading of 280 degrees 600 feet from the southeast corner of the tower. See the enclosed wreckage diagram for additional details. A post crash fire destroyed the cockpit and portions of the engine and accessories. The engine gear box was intact and showed lubrication. Compressor blades were seized and showed extensive fire damage. Fuel control lines and connections were intact and fuel was found inside the unit. Flight control continuity was established by the control cables to the cockpit. The rudder cable was separated aft of the cockpit and showed physical evidence of fire distortion. The propeller blades exhibited torsional twisting. Both propeller blades showed leading edge scouring, striations and gouges. MEDICAL AND PATHOLOGICAL INFORMATION: Emil M. Laga, M. D. of New Iberia, Louisiana, performed the autopsy. Toxicology was requested by the NTSB and the FAA; however, Dr. Laga refused to provide toxicological specimens to the FAA Civil Aeromedical Institute of Oklahoma City, Oklahoma. TEST AND RESEARCH: The communications tower operated by Cellular One of Austin, Texas, was inspected on June 3, 1994, with no reported discrepancies. All tower lights were reported operational on August 4, 1994. The tower outage was clocked at 1528:20 on August 5, 1994. Post accident evaluation by the operator (enclosed report) and the FAA was conducted on August 7, 1994. Three guide cables on the northeast corner outer anchor point contained yellow paint and aluminum fragments. Damaged cable footage ranged from 101 feet to 131 feet above the ground. Stress coiling was evident in all three cables. Additional information: The airplane was released to the owner's representative following the investigation.