What happened
On October 2, 2007, a Kaman K-1200 K-MAX helicopter, registration HB-ZEH, was engaged in logging operations near Ibergeregg, Switzerland. The aircraft was transporting logs from a collection point to a central unloading site. During the approach to the unloading area, the pilot noticed a significant drop in engine RPM. To facilitate an emergency landing, the pilot activated the emergency load release to jettison the logs. The helicopter subsequently struck sloping terrain approximately 100 meters west of the landing site, resulting in the destruction of the aircraft. The pilot, who was wearing a helmet, sustained one injury but was able to exit the wreckage without assistance.
The investigation
Investigators from the Swiss Transportation Safety Investigation Board (SUST) examined the wreckage and the engine components. The investigation focused on the T5317A-1 engine and its N1 accessory drive gearbox. Technical analysis revealed that the engine had shut down during flight. Examination of the gearbox showed significant damage to the bearing, specifically fatigue and pitting in the ball bearing, as well as damage to the bevel gear teeth and the spline of the shaft connecting to the starter/generator.
Furthermore, the investigation looked into the maintenance history and the pilot's actions leading up to the crash. It was noted that the engine had been experiencing intermittent issues, including the activation of the 'ENG CHIP' warning light, for several months prior to the accident.