Incident Overview
A Certified Flight Instructor (CFI) was demonstrating a power-off stall to a student. During the recovery, when full power was applied, the throttle became stuck between 1800 and 1900 rpm. The CFI confirmed that the friction lock was unlocked and attempted to push the throttle forward with both hands, but it would not advance. The pilot chose not to move the throttle back toward idle. The airplane could not maintain altitude, and a forced landing was initiated to a golf course.
Landing and Ground Contact
The CFI stated that he moved the throttle to idle on short final, and the throttle moved aft smoothly. The airplane touched down and, during the landing roll, the left landing gear contacted a sand trap. The airplane pivoted 90 degrees and came to rest upright.
Post-Accident Examination
Post-accident examination of the airplane revealed that the throttle cable's retaining bolt, nut, washer, and cotter pin were in place on the throttle lever arm of the carburetor, and the cable was secure in the mounting brace attached to the engine. The throttle cable was bent approximately 75 degrees into the engine truss as a result of the impact. At the accident site, the throttle cable was moved from the full forward position (the position it was in when personnel arrived) to the idle position; however, it was not possible to move the throttle cable.
The airplane was moved from the accident site, and a second examination took place. During this examination, the cable installation at the throttle quadrant and carburetor was found to be proper. The throttle control was moved, and the cable was observed to move up to the point of the 75-degree bend. After the cable was straightened, normal travel was attained, although some binding was noted near the idle position.
The throttle cable was then disassembled at the throttle control attach point, and the cable was removed. The inner cable was removed from its outer sheathing. The inner cable winding was "somewhat bulged or unwound" at the upper end just forward of the throttle lever attach point. The cable sheath displayed a "shined spot" at a location corresponding to the unwound area. No other anomalies were noted. The reason for the binding was not determined.