What happened
On June 12, 2006, an experimental ultralight aircraft, a D4/EK "Fascination", departed from the Hüttenbusch airfield for a VFR flight toward Oldenburg. Shortly after takeoff, the aircraft entered a northbound circuit and returned for a low-level pass of runway 2-7. Witnesses observed the aircraft accelerating at an altitude of approximately 30 meters, traveling at an estimated speed of 250 km/h.
As the aircraft passed the control tower, the left wing separated from the fuselage. The aircraft rolled onto its left side and struck a field approximately 150 meters left of the runway threshold. The impact and subsequent post-crash fire resulted in two fatalities.
The investigation
The BFU examined the wreckage and the aircraft's maintenance records. Investigators recovered fragments of the left wing and analyzed the structural integrity of the wing components. The investigation also reviewed the aircraft's certification status, noting that the airworthiness documentation was incomplete at the time of the accident, as the final certification process had not yet been concluded.
Findings
Analysis of the left wing fragments revealed that the underside of the torsion nose had been opened between ribs 5, 6, and 7. These areas had been repaired using adhesive, but these repairs were not documented in the aircraft's logs. The investigation determined that the structural failure of the wing was caused by insufficient strength in the wing structure, specifically due to improper gluing of the composite wing skins to the ribs and the main spar.
Safety action
Following the accident, the German Federal Aviation Office (LBA) issued airworthiness directive LTA-Nr.: D-2007-358. This directive targeted similar D4/E-BK aircraft, requiring inspections of the wing structures for faulty adhesive bonds and mandating repairs where necessary.