NTSB Identification: LAX98LA308.
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Accident occurred Saturday, September 26, 1998 in ATWATER, CA
Probable Cause Approval Date: 04/20/2000
Aircraft: Rockwell COMMANDER 114, registration: N114AL
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The engine sputtered then quit as the pilot was initiating a turn to base. He landed hard on the runway and severed the right main landing gear. The aircraft continued forward on the runway, then impacted a runway light and veered off into a grassy area. An FAA inspector examined the engine and noted no external damage. The aircraft was equipped with a dual cased single-drive magneto and the maintenance records indicated that a 500-hour inspection had been performed on the magneto on June 13, 1998. The mechanic reported that he checked all the points for evidence of arcing and found none. He stated that he ran the magneto on a test bench and it ran normally. Postaccident examination of the magneto revealed that the right points did not open and the left points would close intermittently. It was further noted that the cam followers for both sides of the magneto were melted. Neither capacitor passed the insulation resistance test at 400 VDC. The magneto was test run with the original harness and capacitors attached. Both sides of the magneto generated sparks at 500 and 1,000 rpm. A 150-watt lamp was set up next to the magneto to simulate engine heat. The magneto was then run at a speed approximating cruise speed. After 5 minutes, the right magneto ceased to generate sparks. The left magneto generated sparks for the duration of the test. The pilot reported that he performed two magneto checks prior to takeoff, with no noted discrepancies.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

An internal capacitor failure and melting of the point cam followers, which resulted in failure of both magnetos, and subsequent total loss of engine power.

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