Incident Overview
During a traffic pattern, an airplane's engine backfired several times. The pilot landed and noted during taxi that the right ignition source was functioning intermittently. Unable to replace the component at that time, the pilot departed the following day. On a normal descent to the final destination, the right ignition source became completely inoperative.
Post-Flight Inspection
After landing at the final destination, the pilot removed the back plate of the right Hall Effect sensor module. Inside, the timing rotor was found fractured, and the internal face of the back plate showed rotational scoring marks.
Examination Findings
The Safety Board examined the failed timing rotor and determined the fracture was due to low-stress, high-cycle fatigue. The pilot had previously replaced both original magnetos with a Dual Lightspeed Plasma II ignition system equipped with Hall Effect Sensor Modules.
Manufacturer Input
According to the ignition system manufacturer, approximately 400 timing rotors were in service at the time of the incident, and no other failures had been reported.