What happened
On September 28, 2011, a Robinson R44 Raven I helicopter was preparing for a flight from the Waren–Vielist special landing field to Rechlin–Lärz for refueling. The pilot was operating the aircraft alone. During the takeoff sequence, after the engine had warmed up and the pilot had increased the collective to 17 inches to lift the aircraft off the skids, the helicopter experienced a sudden jolt. The aircraft began to tilt toward the right, causing the rotating main rotor blades to strike the ground. The helicopter came to rest on its right side, sustaining heavy damage. The pilot sustained minor injuries and was able to exit the aircraft.
The investigation
The BFU investigation examined the aircraft, the site, and the pilot's actions. Physical inspection of the wreckage revealed that the tail boom had been torn from the fuselage and broken, the tail rotor drive shaft was fractured, and both main rotor blades were destroyed. The investigation also noted that the control rods to the rotor head had broken at the swashplate area. At the accident site, investigators found evidence of the rotor blades striking the ground and noted that the grass had been torn up along the path of the sliding right skid. The investigation also reviewed manufacturer safety notices regarding the risks of dynamic rollover.
Findings
- The primary cause of the accident was a dynamic rollover.
- The aircraft's right skid acted as a pivot point while a rolling moment was applied around the longitudinal axis.
- The pilot's memory of the event was interrupted immediately after the aircraft became light on the skids.
- The grass at the parking area was approximately 20–35 cm in length.