What happened
On 16 December 2003, a Piper PA-17 (registration ZS-VLN) departed from Pietermaritzburg (FAPM) for a private flight destined for Cato Ridge. Shortly after the aircraft left the runway, the engine began to lose power before failing completely. The pilot attempted an emergency landing in an open field located just outside the airport perimeter. The aircraft eventually came to a halt on Murray Road, a public thoroughfare. While the pilot escaped the wreckage without injury, the passenger sustained a broken arm. The aircraft sustained substantial damage during the sequence of events.
The investigation
Investigators examined the aircraft's airframe and engine in a workshop setting. The inspection revealed no mechanical defects or pre-existing issues other than the damage sustained during the crash. The aircraft had been maintained by an approved person, and its annual inspection was current, having been completed in April 2003. Furthermore, the fuel tanks contained sufficient fuel for the intended flight, and the engine had not been subjected to any inhibition processes that might have affected performance.
Findings
Technical analysis established that the engine failure was linked to specific operational settings. It was determined that applying carburetor heat caused a loss of power, and crucially, the engine failed when a full rich mixture setting was applied once the engine had reached its normal operating temperature.