What happened
On 23 April 2011, a Rotorsport UK MTOSport, registration G-CGEW, was involved in an accident during a training flight at Popham Airfield, Hampshire. The flight was being conducted for instructional purposes, specifically focusing on how to manage rotor speed increases without the use of a pre-rotator.
During the maneuver, the pilot was instructed to pull the control stick back gently while the rotor speed was at approximately 100 rpm. The goal was to allow the rotor speed to build up to roughly 200 rpm before applying full power for a standard takeoff. While following these instructions and moving the stick back, the rotor blades made contact with the aircraft's fin. The impact resulted in damage to the empennage, the propeller, and the rotor system. There were no injuries to the two crew members on board.
The investigation
The investigation examined the procedures being performed and the manufacturer's guidance regarding the aircraft's operation. The pilot was following a specific technique to increase rotor speed without the pre-rotator engaged.
Investigators reviewed the Pilots’ Operating Handbook for the Rotorsport UK MTOSport, which notes that operation without a pre-rotator is possible. The manual provides instructions to manually increase the blades to approximately 45 rpm before taxiing into the wind and applying power. However, the investigation also highlighted a critical warning within the handbook: holding the control stick fully back brings the blades into close proximity to the rudder. The manual warns that blade flap, system flexibility, or uneven ground surfaces could lead to contact between the blades and the tail unit.