N8810Z

On September 7, 1994, at 0600 eastern daylight time, an Eagle DW-1 (crop duster), N8810Z, registered to and piloted by Duane E. Mahue, sustained substantial damage during a forced landing near, Houlton, Maine . The pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The departure point was Houlton. The local flight was operated under 14 CFR Part 133.

The pilot had started the initial pass over a field, and was about to start aerial application, when the engine lost power. According to the pilot's statement, the "plane started to shake, sputter and backfire." The pilot tried to land at the airport, but was unable to reach the runway. The pilot elected to land on Interstate Highway 95, the right wing struck a tree, the airplane hit a guard rail, and flipped over.

The engine was removed from the airframe, and shipped to Williamsport, Pennsylvania, at the request of the NTSB. An engine test run was conducted under the supervision of the FAA, at Lycoming's facilities, Williamsport, Pennsylvania, on November 15, 1994.

The engine was mounted on a test stand and a start was attempted. According to the test run report submitted by Lycoming, the engine tried to start, but "would not continue to run." Black smoke was observed coming from the exhaust pipes and the engine was "kicking backwards." Magneto timing was checked, and found to be "approximately 27 degrees before top dead center." The magneto timing was adjusted, and again the engine could not sustain a run. The magneto was replaced, and the engine ran successfully.

Disassemble of the Bendix (dual) magneto, Model D6LN-3000, P/N 10-682560-13, S/N-6197, revealed that a piece of metal was found logged under the impulse spring cover. The piece of metal was removed, the impulse coupling was reassembled. After reassembly the investigation revealed that the, "impulse was still very hard to turn."

Detailed examination of the magneto revealed that corrosion was present in the magneto housing, and on the rotating magnet (right side). The points were arcing, and the arcing was sufficient enough to cause a partial power loss.