What happened
On October 22, 2011, a chartered Wild Thing WT01 ultralight aircraft departed from Waldeck for a flight to Korbach airfield. The flight was intended for aerial photography, a task the pilot and passenger had performed together previously. After landing at Korbach at 16:29, the pilot performed maintenance on his own aircraft before departing Korbach for the return leg to Waldeck at 16:57.
During the departure from Korbach, witnesses observed the aircraft flying at low altitude, changing its direction and altitude several times. At approximately 17:04, the aircraft entered a steep climb while initiating a left-hand turn. During this maneuver, the aircraft stalled over a wing and impacted the ground approximately 160 meters from the northeast end of runway 21. The impact resulted in two fatalities and the total destruction of the aircraft.
The investigation
The BFU investigation examined the aircraft's configuration, weight, and center of gravity. Investigators found that the aircraft's trim was set to a nose-heavy position, and the flaps were extended to the first notch, likely to facilitate low-speed photography.
Discrepancies were noted regarding the aircraft's empty weight. While the pilot's records suggested an empty weight of 311 kg, the BFU's physical weighing of the wreckage determined the actual empty weight was 335 kg. The investigation also found that unsecured cargo in the rear of the cabin was not properly restrained.
Findings
- The aircraft was operating above its maximum takeoff mass. Based on the actual empty weight of 335 kg and a combined occupant weight of 215 kg, the takeoff weight exceeded the permitted 472.5 kg limit.
- An aft center of gravity contributed to the instability, likely caused by the combination of the aircraft's weight, the configuration of the flaps, and the presence of unsecured items in the rear compartment.
- The primary cause of the accident was the aircraft's speed dropping below the minimum flight speed during a climbing left-hand turn, which led to an uncontrolled flight state.