What happened
On 7 October 2009, a Robinson R44 Raven, registration G-CDXB, was undergoing engine warm-up at Culter Helipad in Aberdeenshire. The pilot was participating in a refresher course to renew a type rating and had been instructed to perform the initial engine start independently before the instructor joined the aircraft.
During the post-start procedures, the helicopter unexpectedly lifted off the ground. As the aircraft became airborne, the right skid struck the ground, causing the helicopter to roll onto its right side. The pilot managed to shut off the fuel supply and egress the aircraft with minor injuries. While components of the main rotor were scattered up to 90 metres from the wreckage, no persons on the ground were harmed.
The investigation
The investigation examined the aircraft's configuration and the pilot's actions during the low rotor RPM check. Post-accident inspections of the Robinson R44 Raven suggested that the after-start checklist had not been fully completed. Specifically, the investigation looked into whether the collective lever had been raised too high or if the throttle setting was excessive during the check.
Investigators also assessed the cockpit settings, noting that the governor appeared to be off, while the hydraulic switch was on. The investigation also considered the state of the flight controls, noting that the cyclic friction remained applied, which would have hindered the pilot's ability to react to the sudden lift-off.
Findings
- The unexpected takeoff was likely caused by the excessive raising of the collective lever or an inappropriately high throttle setting during the rotor RPM check.
- The pilot's ability to regain control was likely compromised by the element of surprise and the fact that the cyclic friction was still engaged.
- The after-start checklist was not fully executed prior to the occurrence.