Incident Overview
On September 28, 2011, a single-engine Robinson Helicopter Company R44 Raven I experienced an accident while attempting to take off from Sonderlandeplatz Waren–Vielist (EDOW) in Germany. The investigation was conducted by the Bundesstelle für Flugunfalluntersuchung (BFU) under case number BFU 3X161-11.
Flight Details and Sequence of Events
The 68-year-old pilot, holding a Private Pilot License for helicopters, intended to fly to Verkehrslandeplatz Rechlin–Lärz for refueling. He was seated alone in the right front seat. During the engine warm-up and pre-flight checks, no abnormalities were reported. As the pilot slowly raised the collective pitch lever to 17 inches, the helicopter became "soft" on its skids. At this point, the pilot lost consciousness or memory of subsequent events.
Witnesses observed a sudden jerk through the airframe as it lifted off. The helicopter began to roll to the right, and the rotating main rotor struck the ground. The aircraft came to rest heavily damaged on its right fuselage side. The pilot exited the wreckage with minor injuries. An Emergency Locator Transmitter (ELT) was activated, with the first signal recorded at 11:31 local time.
Aircraft Condition and Findings
The helicopter, manufactured in 2008 with serial number 1926, had approximately 1,585 total flight hours. Post-accident inspections revealed that the tail boom was torn from the fuselage and bent, while the tail rotor drive shaft was broken. Both main rotor blades were destroyed, with fragments found around the wreckage. The cockpit glazing was damaged, and the fuselage exhibited multiple deformations.
The pitch lever was found in a pulled position. Control linkages to the rotor head near the swashplate were broken. The engine mount was deformed, and all spark plugs showed significant wear or had reached their service limits. Fuel leaked from the wreckage, with approximately 25 liters drained. No fire occurred.
Environmental and Operational Context
Weather conditions at the time were favorable, with visibility exceeding 10 km, light winds from 230 degrees at 4 knots, and clear skies. The accident site was located in the northeastern area of the aircraft parking apron near a windsock. Ground marks indicated that the helicopter had rolled over its right skid, tearing out a strip of grass from the parking spot to the final resting position.
Probable Cause Analysis
The investigation highlighted the phenomenon of "Dynamic Rollover." This occurs when one skid acts as a pivot point and a rolling moment around the longitudinal axis exceeds a critical angle. Once this threshold is crossed, it is typically impossible for the pilot to stop the rollover. The manufacturer's Safety Notice SN-9 advises pilots to maintain balance between left and right skids and lift off slowly and controlledly to avoid this hazard.