What happened
On the afternoon of 1 December 2024, a Cubby aircraft, registration ZU-DWY, departed Highway Airfield in Knysna, Western Cape, for a local scenic flight. The flight began with a passenger on board, but the pilot returned to the airfield after approximately ten minutes because the passenger had become airsick. After the passenger disembarked, the pilot taxied back to the start of Runway 13 and took off again.
During the second climb, the aircraft entered a teardrop turn to position itself for landing on the reciprocal Runway 31. During this maneuver, the engine ceased operation, causing the aircraft to stall. Due to the low altitude, the pilot was unable to recover from the stall, and the aircraft impacted the ground at Forest View Farm in a nose-down attitude. The pilot sustained serious injuries, and the aircraft suffered substantial damage.
The investigation
An investigation by the SACAA AIID established that the aircraft had been stationary for approximately three months prior to the accident. During this period, the aircraft was subject to high summer temperatures, which likely caused fuel condensation and the formation of water droplets within the fuel tank.
While the initial flight segment was successful because the water and fuel were temporarily mixed, the investigators determined that during the period between the first landing and the second takeoff, the water likely settled at the bottom of the tank. The investigation found that the pilot did not perform adequate pre-flight checks, such as draining the fuel to check for contamination. Consequently, the engine ingested water during the second climb, leading to the engine failure.
Findings
- The engine stopped during the climb phase of the flight.
- The pilot attempted a teardrop turn to land on the opposite runway rather than following the recommended procedure of landing straight ahead following an engine failure.
- The aircraft stalled due to the loss of power and reduced airspeed during the turn.
- Water contamination in the fuel was a primary factor, as the aircraft had been unoperated for three months.
- The pilot failed to conduct sufficient pre-flight inspections to identify fuel contamination.