What happened
On 1 November 2014, a Rotorsport UK MT-03, registration G-JBRE, was positioned on Runway 20 at Shoreham Airport for departure. The pilot had pre-rotated the main rotors to 200 rpm to prepare for takeoff and avoid delaying other aircraft in the sequence. After a delay in receiving clearance, the pilot temporarily disengaged the pre-rotation to prevent wear on the drive mechanism.
Upon receiving takeoff clearance, the pilot re-engaged the pre-rotation. Believing the rotor speed had reached the target 200 rpm, the pilot advanced the throttle, applied aft stick input, and began adjusting the rotor trim. During this maneuver, the rotor blades made contact with the propeller. The pilot felt a lateral jolt and vibration, which he initially mistook for a landing gear issue. To prevent further damage to the runway, the pilot aborted the takeoff and steered the aircraft into the grass adjacent to the runway. There were no injuries to the pilot.
The investigation
The investigation examined the damage to the aircraft, which included the rotor blades, propeller blade tips, tailplane, and rudder cables and rods. Investigators analyzed the flight sequence and the pilot's control inputs relative to the rotor speed. The physical evidence, specifically the damage to the lower surfaces of the rotor and the propeller tips, confirmed that the rotor blades had struck the propeller.
Findings
- The interaction between the rotor blades and the propeller was caused by a combination of low rotor speed, increasing airspeed, and specific control inputs.
- The pilot's control inputs and forward speed were inappropriate for the actual rotor speed, leading to a retreating blade stall.
- The pilot's lack of experience operating at a busy airfield was considered a contributing factor to the sequence of events.