What happened
On 12 June 2009, a BE36 TC Bonanza, registration ZS-MGV, was conducting a training flight from Mookets and private aerodrome in Limpopo province toward Wonderboom aerodrome in Gauteng. The flight, operated under visual flight rules, proceeded without issue following a thorough pre-flight inspection. However, approximately one hour into the flight, while cruising at an altitude of roughly 6,500 feet AGL, the pilot observed a sudden drop in oil pressure, which was immediately followed by total engine failure.
Recognizing the emergency, the pilot identified a gravel road on a nearby private farm and initiated a forced landing. The pilot followed the emergency procedures outlined in the Pilot's Operating Handbook (POH). The aircraft touched down on the farm without causing any damage to property or the aircraft structure, though the engine was rendered inoperable due to seizure. Both the pilot and the passenger escaped the aircraft without any injuries.
The investigation
An investigation by the SACAA AIID examined the aircraft and the circumstances surrounding the engine failure. Investigators inspected the engine and noted significant oil leakage beneath the aircraft belly. A metallurgical examination was performed on the engine components to identify the source of the failure.
Findings
Technical analysis revealed that the engine oil scavenge line pipe failed due to metal fatigue. The fatigue originated at the toe of a fillet weld that secured the pipe to the engine mounting flange. The investigation determined that the failure was attributed to an inadequate weld size. The investigation also confirmed that the aircraft had been properly maintained, with the last annual inspection completed only 20.8 hours prior to the incident, and that weather conditions were favorable at the time of the event.