Pilot error is the primary cause of over 70 percent of all fatal general aviation accidents - a statistic that doesn't change much from year to year. Although it is difficult to determine the percentage that result because of poor decision-making, most accidents can be prevented if better decisions are made by the pilot-in-command.
On July 2, 2002, a Piper Turbo Arrow crashed shortly after takeoff from Lebanon, Tennessee. The training flight consisted of a private pilot and a flight instructor in the front seats, and a commercial-rated pilot in the backseat. The private pilot and CFI were killed, while the pilot in the back received minor injuries.
While conducting the run-up before takeoff, the left magneto operated normally, but when the right magneto was checked, the engine quit. A discussion ensued between the three pilots and the decision was made to continue the flight, on one magneto. The rational behind this decision was that the airplane had been flown in the same condition the previous week.
The Arrow proceeded to take off, and at about 200 feet agl, it began to sink. Ground witnesses noted that the airplane sounded normal, but did not climb normally. The CFI took control of the Arrow, banked to the right, and impacted a power line. At the time of the accident the CFI had almost 1,700 hours of experience, and the private pilot had accumulated 145.
The right magneto was inspected after the accident, and erratic spark conditions were noted on the spark plug leads up to 1500 rpm. From 1600-2600 rpm, the spark was consistent, and at 2700 rpm, the magneto sparked normally.
The NTSB determined the cause of this accident to be the CFI's attempted flight with known deficiencies, the inoperative magneto, and the subsequent loss of engine power, which resulted in a collision with power lines.
According to the POH for the Piper Turbo Arrow, during the ground check of the magnetos, "Drop off on either magneto should not exceed 175 rpm and the difference between the magnetos should not exceed 50 rpm." Logic would dictate if either of these conditions is met, the engine should be inspected before flight. The POH also goes on to say, "operation on one magneto should not exceed ten seconds."
Clearly, this accident would have been prevented if only the pilots had followed the guidelines outlined in the POH and stayed on the ground once the problem was discovered. The decisions made by these pilots highlight how blatant disregard of aircraft limitations can be deadly. Test pilots and engineers set these limitations for a reason - they must be followed.
For more information about aeronautical decision-making, see Robert N. Rossier's "Troubled Thoughts," from the April 1996 issue of AOPA Pilot magazine.
This accident report as well as others can be found in ASF's Online Database.
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