What happened
On January 29, 2024, a Hughes Helicopters HU 369D helicopter departed from the Mühldorf special landing field for a flight to Kirchdorf am Inn. The flight was being conducted as a proficiency check to maintain the pilot's type rating. Shortly after takeoff, while climbing at approximately 700 ft AGL and a ground speed of 75 kt, the aircraft suffered an unexpected engine failure.
The pilot initiated an autorotative maneuver, performing an executing an autorotation with a reverse turn toward a field located below the aircraft. During the landing on the soft ground, the helicopter tipped over, coming to rest on its right side. The aircraft sustained heavy damage, including a broken tail boom and a detached right skid, while also causing minor damage to the surrounding field. The pilot, who was the owner and operator of the aircraft, was able to exit the wreckage independently and sustained no injuries.
The investigation
The BFU examined the wreckage and the Allison 2-shaft turboshaft engine. The investigation included a physical inspection of the engine components, such as the fuel filters, chip detectors, and the fuel spray nozzle. No evidence of oil or fuel leaks was found, and the fuel filters showed no contamination. The engine could be rotated by hand without any unusual resistance or noise.
To further the investigation, several critical components—including the Fuel Control Unit, the Power Turbine Governor, the Engine Fuel Pump, the Engine Bleed Valve, and the Engine Fuel Spray Nozzle—were disassembled and sent to a specialized facility in the United Kingdom. These components were inspected under the supervision of the UK Air Accidents Investigation Branch (AAIB).