2014 Hélicoptères Guimbal Cabri G2 accident near Egelsbach

Incident Overview and Flight Details On 18 October 2014, a Hélicoptères Guimbal Cabri G2 helicopter was involved in an accident near Egelsbach, Germany. The aircraft, a two-seat helicopter equipped with a Lycoming O-360-J2A piston engine and a Fenestron tail rotor, was operating a night flight from Frankfurt-Egelsbach (EDFE) to Augsburg (EDMA). The pilot, a 43-year-old commercial helicopter pilot, was accompanied by a 26-year-old passenger holding a private helicopter pilot license. Shortly after takeoff and overflying a local industrial area at approximately 18:55 local time, the occupants reported hearing sudden, sharp noises. The pilot, unable to explain the sounds, decided to return to the airfield. During the turn, the pilot experienced a sudden loss of engine RPM, initiated an autorotation, and steered the helicopter toward an open field that had just been overflown. ## Accident Sequence and Damage During the autorotation landing, the helicopter skidded across the field. As it came to rest, the main rotor struck the tail boom, causing severe damage to the aircraft. The tail boom was sheared off just before the vertical fin, the Fenestron shroud sustained circumferential scratches and partial breaks, and two of its seven blades were destroyed. The horizontal stabilizer was broken into several pieces, and one of the three main rotor blades showed severe damage with a split trailing edge. The helicopter came to rest upright on its skids, which had sunk into the soft ground at the end of a several-meter skid mark. Both occupants were able to leave the aircraft uninjured. No fire occurred, and there was no third-party damage. ## Aircraft Maintenance and Technical Findings The affected helicopter, built in 2012 with serial number 1041, had approximately 420 total flight hours. Maintenance records showed that on 21 March 2014 and 25 March 2014, unscheduled maintenance was performed due to a slipping drive belt. On both occasions, the drive belt was found to be contaminated with oil and grease. On 17 April 2014, the main gearbox was resealed due to leaks. The last release to service was issued on 27 August 2014 after scheduled maintenance. Following the accident, further investigation in the presence of the manufacturer, an insurance representative, and the owner revealed that the entire area between the fire wall, engine, and main gearbox—specifically the area around the drive belt—was contaminated with oil and grease. Parts of the drive belt were also contaminated, and the rubber ribs of the belt felt soft and greasy. After disassembly at the manufacturer's facility, it was additionally found that the left drive belt guide was bent and likely had insufficient clearance from the drive belt. The destroyed drive belt, torn into many strips and pieces, was found in the power transmission area between the engine and main gearbox, with some strips wrapped around the tail rotor shaft. ## Meteorological and Operational Context According to the German Weather Service, Germany was situated between a low-pressure system northwest of Ireland and a high-pressure zone extending from the Alps to Eastern Europe, with very mild air flowing in from a southwesterly direction. The stabilizing effect of the high-pressure system remained dominant during the day and into the following night. Routine weather reports (METAR) from the nearby Frankfurt-Main Airport (EDDF) at 18:50 local time indicated wind from 060° at 5 knots, visibility greater than 10 km, no cloud below 5,000 ft (CAVOK), a temperature of 15 °C, a dew point of 14 °C, and a QNH of 1,021 hPa. Sunset occurred at approximately 18:29 local time. The helicopter was not equipped with a flight data recorder (FDR) or cockpit voice recorder (CVR), as these devices were not required by the applicable aviation regulations at the time. ## Investigation and Manufacturer Response The investigation was conducted by the German Federal Bureau of Aircraft Accident Investigation (BFU) in accordance with EU Regulation No. 996/2010 and the German Aircraft Accident Investigation Act (FlUUG). The sole purpose of the investigation was the prevention of future accidents and incidents, not the determination of fault, liability, or claims. According to the manufacturer, no drive belt failure had previously occurred in the affected model prior to this accident. Following the accident, the manufacturer issued Service Bulletin (SB) 14-026A, titled “Transmission Belt Check,” on 27 October 2014.