Primary finding
Probable cause
The failure of the left magneto, which resulted in a partial loss of engine power.
Investigator assessment
Analysis narrative
The pilot said that after descending from an altitude of 4500 ft msl to 2500 ft msl, a partial loss of engine power occurred. During a forced landing in a field, the airplane was damaged. A post-accident examination revealed the left magneto was inoperative.
Source record
Factual narrative
On September 12, 1993, about 1835 eastern standard time, a Cessna 172F airplane, N5678R, experienced partial loss of engine power during cruise and landed off-airport near Fishers, Indiana. The private pilot and two passengers reported no injury. The airplane was substantially damaged in the forced landing. The flight originated about 1630 EST in Galion, Ohio, without a flight plan and operated in visual meteorological conditions under 14 CFR 91. According to the pilot, after descending from an altitude of 4500 feet MSL to 2500 feet MSL, the airplane's right magneto failed. The pilot states the airplane then misfired on the left magneto. Not being able to maintain altitude due to low RPM, he performed emergency procedures and initiated a forced landing onto a field. Postaccident investigation revealed the left magneto was inoperative. -