What happened
On 26 May 2002, a Piper PA32-300, registration ZS-JGH, was conducting a private flight from Bloemfontein Aerodrome toward Lanseria Aerodrome. The aircraft was carrying a pilot and two passengers. While descending to 7500 feet Above Mean Sea Level (AMSL) to navigate below the Johannesburg Terminal Control Area (TMA), the engine failed to respond to the pilot's throttle inputs. The engine remained stuck at a manifold pressure of 13 inches of mercury, a setting insufficient to sustain level flight. Consequently, the pilot was forced to perform an emergency landing in an open field near Shaft 4 of the Westdene Mine. While there were 0 fatalities and 0 injuries, the aircraft's undercarriage sustained damage during the touchdown.
The investigation
Investigators examined the mechanical state of the throttle assembly following the incident. The inquiry established that the throttle cable rod end fitting had separated from the throttle arm. Specifically, the rod end bearing had seized onto the ball end, and the bearing subsequently came loose from the rod end fitting. The investigation also revealed that a larger washer had been omitted from the assembly, which allowed the rod end to slip over the bolt head. Records indicated that the aircraft's last Mandatory Periodic Inspection (MPI) occurred on 27 July 2001, with the aircraft having flown an additional 48 hours since that inspection. All Airworthiness Directives and Service Bulletins appeared to be up to date.
Findings
- The primary cause of the power loss was the separation of the throttle cable rod end fitting from the throttle arm.
- The position of the throttle arm following the failure restricted the engine to a reduced power output, making level flight impossible.
- A contributing factor was the presence of a seized or worn throttle cable rod end fitting that had gone undetected or unrected during the previous MPI.