The private pilot and a passenger planned to depart on a cross-country personal flight in the Piper PA32R from the airport in Falcon, Colorado, where density altitude was about 9,500 feet mean sea level.
During the pretakeoff engine run-up, the engine began running roughly. The pilot and a mechanic attempted to troubleshoot the engine issue by checking the dual magneto.
According to the mechanic, the left magneto was inoperative and the P-leads were wired incorrectly. He then disconnected both magnetos’ P-leads.
The pilot’s second and third engine run-ups appeared to produce full engine power when he adjusted the fuel mixture, however with an inoperative left magneto it is unlikely that full power was achieved.
The pilot departed and was unable to maintain altitude. He chose to land in a field adjacent to the airport. The airplane stalled just above the ground and then hit the ground.
During a post-accident examination of the airplane, the left magneto was removed and tested. It did not produce a spark at any terminal, and the contact points did not open.
Additionally, the spark plugs connected to the left magneto did not exhibit signs of recent operation, which was consistent with an inoperative magneto.
The disconnected P-leads would not have affected the right magneto’s ability to energize half of the spark plugs.
With an inoperative left magneto and a high density altitude, the available engine power would have been reduced, and the airplane’s climb performance would have been degraded.
The reduction in the available engine power, combined with the high-density altitude at the time of takeoff, resulted in the airplane’s inability to maintain a positive rate of climb after lifting off.
Probable cause: The pilot’s decision to depart with an inoperative left magneto, which resulted in degraded climb performance in high-density altitude conditions and a subsequent emergency landing.
This August 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.