Aeronca 11AC N9500E accident near Napa, California

Probable cause

The loss of engine power for undetermined reasons, which resulted in an off-airport landing on unimproved terrain.

NTSB analysis

The pilot was flying the airplane to an airport about 48 miles from the departure airport when, 30 minutes after departure while in cruise flight, the engine lost all power. The pilot then verified engine controls were at their correct positions and adjusted the carburetor heat setting. There was no change in engine power, so he made a mayday call and landed the airplane in an open field, during which the airplane sustained substantial damage to the lower fuselage.

A postaccident examination of the engine revealed that both magnetos produced a weak spark on all ignition leads when the propeller was rotated by hand. The left magneto was found to be in poor condition and did not function within the manufacturer’s specifications. Internal examination of the left magneto revealed that the distributor axle bearing had failed, and the distributor gear was missing about half of its gear teeth. The right magneto was found in poor overall condition and was missing about 6 distributor gear teeth; however, it did function within the manufacturer’s specifications. A review of maintenance records revealed no indication that the left and right magnetos were serviced, to include inspections or overhauls, since the engine’s last overhaul 15 years (or about 400 hours) before the accident.

While the left magneto was not functioning within the manufacturers specifications, and the right magneto functioned within the manufacturers specifications, it would not result a total loss of engine power. The reason for the total loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for WPR22LA099 for the full record.