Incident Overview
On June 5, 2010, an ultralight aircraft operated by Flight Design GmbH, model CTSW (serial number 07-10-23), was involved in an accident near Drensteinfurt, Germany. The incident resulted in no injuries to the pilot or passenger but caused severe damage to the aircraft. The investigation was conducted by the German Federal Aviation Accident Investigation Agency (BFU) under case number BFU 3X072-10.
Flight Details and Sequence of Events
The 46-year-old pilot, holding a valid license for passenger flights, departed from Kamen-Heeren airfield with one passenger. While flying north at approximately 170 km/h near Drensteinfurt, the pilot initiated a 180-degree turn in a descent around 12:30 local time. During this maneuver, the aircraft exceeded its never-exceed speed (VNE), reaching 313 km/h. This overspeed condition induced flutter in the elevator control surface and caused the elevator to break off approximately 30 cm from the vertical stabilizer.
Despite the structural failure, the pilot maintained control of the aircraft and returned to the departure airfield. The landing was executed at a higher-than-normal speed due to the damaged configuration. Post-landing inspections revealed pre-existing damage, including a repair on the left elevator leading edge and a 25 cm paint crack on the upper surface.
Investigation Findings and Safety Actions
The BFU determined that the accident was caused by exceeding the VNE during a turn in descent, leading to aerodynamic flutter and structural failure. Following the incident, the manufacturer conducted ground vibration tests and issued service instructions regarding trim tab modifications. In August 2010, the German Aero Club (DAeC) issued an airworthiness directive limiting the VNE of this model to 225 km/h and requiring warning placards. Further directives in 2012 mandated specific trim tab modifications and weight checks to ensure structural integrity.