What happened
On October 26, 1998, a Hughes 269 C helicopter was performing a transfer flight from Oedheim to Dattenberg. Approximately 30 minutes after departure, the pilot heard a loud bang, followed by smoke in the cockpit and a noticeable yaw to the right. The pilot immediately initiated an autorotation and shut down the electrical system.
As the smoke cleared, the pilot realized the aircraft was on a steep descent toward a cemetery. The engine had ceased functioning, rotor RPM was critically low, and the aircraft's controllability was severely limited. The pilot attempted an emergency landing within the cemetery grounds, but the helicopter struck several gravestones while maintaining forward speed and a high rate of descent. The impact caused the aircraft to capsize. The accident resulted in one person seriously injured and caused damage to the aircraft and cemetery monuments.
The investigation
An investigation by the BFU focused on the mechanical state of the engine and the flight controls. Initial on-site findings suggested mechanical damage to the engine. Subsequent technical analysis revealed that a piston pin in the second cylinder had failed. Metallurgical examination of the fracture surfaces identified a fatigue failure, though the specific origin and cause of this fatigue could not be determined. Investigators also examined the cyclic and periodic main rotor controls; however, due to extensive damage in this area, they could not determine if a technical malfunction in the controls contributed to the low rotor RPM.