Plane & Pilot
Saturday, May 1, 2004

Known And Unknown Deficiencies

It’s both the pilot’s and mechanic’s responsibility to find faulty equipment

Witnesses at the airport observed the flight during the departure and reported that the airplane sounded normal, but it didn’t appear to climb normally, as if it was unable to gain altitude. One witness reported that as he watched the airplane pass, he could see the top of the wings because the nose was high. Another witness, a private pilot, stated that the airplane started to climb with the tail very low, and “it never climbed much.” Witnesses watched the airplane travel down the runway and fly low over the trees. They saw the right wing drop dramatically, and the airplane disappeared behind the trees.

The certified flight instructor held a commercial-pilot certificate with airplane single-engine and multi-engine land, and instrument ratings. His total flight time was approximately 1,675 hours. His approximate flight time in the Piper Arrow was not determined.

The private pilot was rated for airplane single-engine land and instruments. Total flight time was approximately 145 hours, with time in type not determined.

A review of the aircraft’s maintenance records did not disclose any previous work written up as having been performed on the magnetos or engine ignition system. The left and right magnetos were removed for further examination. The magnetos exhibited signs of previous maintenance and the tamper-proof torque seal had been disturbed on both. The left magneto was put on a test bench and run at 100-rpm increments from zero to 2,700 rpm. The magneto functioned normally throughout the operating range. The right magneto was put on a test bench and also run at 100-rpm increments from zero to 2,700 rpm. Erratic spark conditions were noted on the spark leads that are up to 1,500 rpm. From 1,600 to 2,600 rpm, the spark was consistent, and at 2,700 rpm, the magneto sparked normally. According to the passenger, he performed the first flight from Nashville to Lebanon, where he conducted two touch-and-go landings.

Investigators noted that an FAA Advisory Circular states that dual magneto systems are designed to provide redundancy so that, in case one magneto fails, the pilot will be able to proceed to the nearest suitable airport and land under power. It explains that, although an engine can run on only one magneto, only one set of spark plugs will be firing and the quality of combustion and power output will be affected. Investigators also noted that the operating handbook for the airplane called for running the engine with “both” magnetos selected.


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