Synopsis
During after-start checks, the Robinson R44 Raven, registration G-CDXB, became unexpectedly airborne. The right skid contacted the ground and the aircraft rolled onto its right side. The pilot isolated the fuel and was assisted out of the aircraft with minor injuries. Parts of the main rotor were found up to 90 metres from the aircraft, but there were no injuries to anyone on the ground.
History of the Flight
The pilot was undertaking a refresher course to renew his type rating on the R44. He was due to undertake a training flight and had been briefed by his instructor to start the aircraft on his own, after which the instructor would join him. The aircraft was started and after allowing some time for the engine to warm up, the instructor was approaching the aircraft when it suddenly became airborne. This was probably a result of the collective lever being raised excessively, or the throttle being set too high, as part of completing the low rotor RPM check. The aircraft landed again on its right skid before rolling on its side.
Post-Accident Inspection
The training organisation carried out a post-accident inspection of the aircraft and reported that the governor was off, collective friction was off but cyclic friction on, and the hydraulic switch was on. If the switches were undisturbed as a result of the accident, it would appear that the after-start checklist had not been completed.
Analysis
For the aircraft to have become airborne, it is most likely that the collective had been raised. If this was a deliberate action, the check which calls for this to be done only requires a small movement of the lever, sufficient to check the low rotor RPM warning horn and light. It is possible that either the lever was inadvertently raised excessively or that, with the governor switched off, the rotor RPM had been set excessively high at the point the lever was raised. Once the aircraft became airborne, the pilot would have had additional difficulty in trying to control it, both as a result of surprise and the fact that the cyclic friction was still applied. This is likely to have contributed to the subsequent loss of control leading to the aircraft rolling over.