What happened
On the afternoon of 14 December 2001, a Windlass Aquilla, registered ZU-BWB, departed from Microland in Bapsfontein for a local recreational flight. The aircraft was carrying a pilot and one passenger. Shortly after takeoff, the aircraft performed a series of steep turns and high-attitude climbs and dives. During this sequence of maneuvers, the aircraft crashed approximately 2km from the departure point. The impact resulted in two fatalities, as both occupants sustained fatal injuries. The aircraft was destroyed in the crash.
The investigation
Investigators examined the wreckage and the aircraft's maintenance history to determine the cause of the structural failure. The inquiry established that the pilot held a valid microlight license and medical certificate. However, the investigation revealed significant lapses in the aircraft's maintenance oversight. The annual inspection for 2001 had not been performed, and the previous annual inspection in 2000 had been completed six months late. Furthermore, the aircraft's "Special Flight Permit" had expired on 5 November 2001, meaning it lacked a valid "Authority to Fly" at the time of the accident. The aircraft's logbook had not been updated since October 2000.
Findings
- The aircraft entered a "Whip-Stall" maneuver, which subjected the wing to negative loads exceeding its design limits.
- This maneuver led to a catastrophic failure of the wing structure.
- Evidence of damage was found on the spreader bar cables, specifically suspect marks on the swage ferrules near the center lugs caused by being pinched by the swivel block.
- It is believed these cables failed due to pre-existing damage that was not identified.
- The absence of the 2001 annual inspection meant that the damage to the cables and ferrules likely went undetected.
- Witness accounts of the pilot performing aggressive maneuvers, such as steep turns and high-attitude climbs and dives, served as a major contributing factor to the structural failure.