What happened
On 11 December 2021, a Slick-360 aircraft, registration ZU-MDA, was participating in the Ace of Base 2021 aerobatic competition at Baragwanath Aerodrome (FASY) in Johannesburg. The flight, conducted under visual flight rules, was part of a scheduled display by the Sport Aerobatic Club.
During the final sequence of the display, the pilot attempted a complex maneuver consisting of a half Cuban-8 and a one-and-a-half snap roll. Eyewitnesses observed that the aircraft's left wing stalled during this high-speed sequence. While the pilot initially managed to recover from the first stall, a subsequent stall occurred at an altitude of less than 400 feet. The aircraft entered an uncontrolled descent and impacted the ground in an open area adjacent to a taxiway. The impact resulted in the destruction of the aircraft and the fatal injury of the pilot.
The investigation
An investigation by the SACAA AIID established that the aircraft was airworthy and maintained according to regulations prior to the accident. The investigation focused on the flight dynamics and the circumstances leading to the loss of control. Investigators noted that the high-density altitude at the time—approximately 7,590 feet—likely degraded the aircraft's performance.
Crucially, the investigation found that the pilot had designed and submitted his display sequence only the night before the event. Because the sequence was not practiced at the aerodrome prior to the competition, the pilot failed to realize that his planned maneuvers would lead to an insufficient altitude for recovery.
Findings
- The primary cause was the pilot's improper estimation of the starting altitude required to safely execute the descending Cuban-8 and snap roll maneuvers.
- The pilot initiated the final maneuver at approximately 700 feet, which left insufficient margin for error when the stall occurred.
- The pilot had not attended the official briefing or practiced the specific maneuvers at the event site prior to the competition.
- The organizers accepted the flight sequence despite it being submitted very late and without prior practice.
Safety action
Following the accident, the Sport Aerobatic Club (SAC) has moved to implement several safety enhancements, including:
- Implementing a "buddy system" to ensure pilots are fully prepared and have checked all flight parameters.
- Requiring competitors to indicate a specific "break point" in their sequences to account for altitude or weather changes.
- Enhancing sequence checking by senior judges to identify potential safety risks in submitted maneuvers.
The AIID has recommended that the competition committee implement a formal cut-off date for entries and establish a system to verify that all submitted sequences have been practiced and reviewed by a peer.