On August 4, 1990, an Air Tractor AT-401 (registration N45116) operated by Macys Flying Service Inc. was involved in an aviation accident near Tule Lake, CA. Investigators recorded the probable cause as: The loss of engine power due to the right magneto distributor gear having approximately 50 percent of its teeth missing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
The pilot landed in a field after the engine quit during a spray run, colliding with a water line and causing the gear to collapse.
What happened
The aircraft was engaged in an agricultural operation when the engine stopped operating. The pilot initiated a pull-up maneuver to begin another spray pass, but power was lost. Unable to maintain altitude, the pilot executed an emergency landing in an adjacent field. During the touchdown, the aircraft struck a 12-inch water line buried in the ground. The impact caused the landing gear to collapse, and the nose of the aircraft pitched forward over.
The investigation
Following the accident, investigators examined the engine components to determine the cause of the power loss. The inspection revealed significant damage to the ignition system. Specifically, the right magneto was found to be missing approximately 50 percent of the teeth from its distributor gear. This mechanical failure prevented the ignition system from functioning correctly, leading to the sudden stoppage of the engine.
Probable cause
The loss of engine power due to the right magneto distributor gear having approximately 50 percent of its teeth missing.