Mixture Control Cable Separation Leads to Forced Landing and Nose-Over (N1763U)

Accident Details

A pilot was in cruise flight after leveling off and began leaning the fuel mixture when the mixture control ceased to have any effect. The engine subsequently lost power and stopped running. The pilot executed a forced landing on tundra terrain, during which the airplane nosed over.

Postaccident Inspection

Examination after the accident revealed that the mixture control cable had unscrewed from the mixture control arm. The cable had been replaced 238 flight hours before the accident and had been inspected at 142 hours and again at 44 hours prior to the event.

Maintenance Specifications

The aircraft's service manual specified that the jam nut securing the cable to the mixture control arm should be torqued to 15 ± 2 inch-pounds. No safety wire was required for this linkage at the time of the accident. According to the investigation, if the linkage becomes disconnected, gravity would allow the mixture control arm to move to the idle-cutoff position.