Piper PA32R N2880W accident near Falcon, Colorado

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.

NTSB analysis

The private pilot and the passenger planned to depart on a cross-country personal flight; the density altitude was about 9,500 ft 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 and chose to land in a field adjacent to the airport; the airplane stalled just above the ground and then impacted the ground.

During a postaccident examination of the airplane, the left magneto was removed and tested; the left magneto did not produce a spark at any terminal, and the contact points did not open. In addition, 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.

Text from the NTSB. Open the NTSB docket for CEN18LA348 for the full record.