Incident Overview
The pilot reported that the airplane was not climbing as expected and showed decreased engine rpm. After checking the throttle and mixture controls, and with obstructions ahead, the pilot intentionally stalled the airplane, which resulted in a hard landing.
Post-Accident Examination
Examination of the mixture control system revealed that the mixture control arm was in the idle cutoff position. The mixture control cable was fractured aft of the mixture control arm. A bracket near the carburetor that secures the mixture cable was displaced to the left by 1.5 inches. Additionally, the swivel assembly in the mixture control arm was installed upside down.
Following the accident, the engine was operated and reached 2,300 rpm. After the engine run, both ends of the flame tube of the muffler were found separated. One of the flame tube ends had impact damage, and portions of the fracture surfaces on both ends had a relatively shiny appearance.
The mixture control cable exhibited wear and fatigue adjacent to the fracture area, with bending overstress to the right on the remaining fracture surface. The mixture control cable had not been replaced since the airplane was manufactured in 1974. The airplane had accumulated 2,246 total flight hours since manufacture, 44 hours since the last annual inspection 11 months earlier, and 408 hours since an overhauled muffler was installed.