What happened
On the morning of 15 July 2024, a Sling 4 TSI aircraft, registration ZU-PBL, departed Tedderfield Aerodrome (FATA) for Rand Aerodrome (FAGM) in Gauteng Province. The flight was being conducted under private operations in clear visual meteorological conditions. During the climb phase, at an altitude of approximately 500 feet above ground level, the right-side gullwing door opened unexpectedly.
In an attempt to secure the door, the pilot inadvertently moved the control stick to the right. This maneuver caused the aircraft to bank more than 60 degrees to the right, entering a state of sideslip. This sudden movement caused the fuel in the selected right tank to migrate away from the pickup point toward the wingtip. Consequently, the engine experienced a surge and subsequently stopped due to fuel starvation. The pilot performed a forced landing in an open area near an informal settlement. While the aircraft sustained substantial damage, the pilot and passenger escaped without injury.
The investigation
SACAA AIID investigators examined the aircraft's engine, a Rotax 915, and found no mechanical defects; the engine was capable of operating within all specified parameters. Data retrieved from the Engine Control Unit (ECU) confirmed that the fuel flow fluctuated and cut off approximately two minutes after takeoff, while the power lever was set to 99% power.
Investigators also reviewed the aircraft's fuel system and the Pilot’s Operating Handbook (POH). The investigation focused on the interaction between the aircraft's flight attitude and the fuel delivery mechanism. The inspection of the door latching mechanism suggested that the door had not been fully secured prior to departure.
Findings
- The primary cause of the engine failure was fuel starvation resulting from an excessive roll angle.
- The pilot's attempt to close the open door led to a right-hand bank exceeding the 60-degree limit specified in the POH.
- This extreme bank caused fuel to move away from the intake pipe in the right wing tank.
- The right-side door was likely not properly latched during the takeoff roll, allowing airflow to push the handle and open the door in flight.
- The aircraft was airworthy and the pilot was qualified and medically fit for the flight.