What happened
On 9 November 2018, a Partenavia P68C-TC, registration ZS-PBR, departed Lanseria International Airport for a maintenance check flight. The flight was being conducted following a mandatory periodic inspection to test a newly installed onboard camera system. The aircraft was carrying a full fuel load of 520 litres.
During the flight, the pilot observed a significant fuel imbalance, noting that the right-hand fuel gauge was dropping while the left remained full. In an attempt to rectify this, the pilot utilized the cross-feed system. However, when the imbalance persisted, the pilot reverted to selecting fuel from the respective tanks for each engine. While traversing the Magaliesberg mountain range, the right engine surged and failed, followed shortly by the failure of the left engine. The pilot attempted an emergency landing on a road near Hartebeesfontein Road, where the aircraft struck small trees and a brick wall, resulting in substantial damage to the airframe. The pilot escaped without injury.
The investigation
SACAA AIID investigators examined the fuel system architecture and the pilot's actions during the emergency. The investigation focused on the sequence of fuel selector movements and the activation of fuel pumps. Investigators also reviewed the aircraft's maintenance history, noting that the aircraft had recently undergone a 100-hour inspection and was being used for a post-maintenance test flight.
Findings
- The aircraft was operated with the cross-feed selector configured to supply fuel from the right tank to both engines, which caused the right tank to deplete rapidly.
- The pilot failed to activate the left auxiliary fuel pump after switching the fuel selectors to the left tank.
- This omission created a vacuum in the left engine's fuel supply line, restricting fuel flow to the engine while it was at cruise power.
- The loss of fuel pressure led to the sequential failure of both engines, making sustained flight impossible.