What happened
On 1 July 2018, a Rotorway Executive 90, registration G-BZES, was involved in an accident at Fenland Airfield, Lincolnshire. The pilot intended to refuel the aircraft, which was stored near a new hangar area that had been roped off due to unfinished surfacing. After coordinating with an airfield steward to manage bystanders, the pilot departed the hangar area and flew toward Holding Point ‘A’ to establish radio communications.
The flight path initially involved flying into the wind before turning crosswind and eventually proceeding in a downwind direction. During this final leg, the pilot inadvertently approached the landing point with a tailwind. As the aircraft descended toward the holding point, it experienced a sudden, unrecoverable increase in the rate of descent. The helicopter struck the ground heavily on the rear skid and pitched forward, causing the main rotor and skids to impact the surface and resulting in a rollover. The pilot, who was wearing a full harness, escaped the aircraft without injury.
The investigation
Investigators examined the flight dynamics and the environmental conditions at the time of the accident. The wind was recorded as an easterly 12 knots. The investigation focused on the aerodynamic consequences of the pilot's approach profile, specifically the transition from an into-wind to a downwind heading.
It was established that performing a descending approach into a tailwind using standard visual cues can lead to a reduction in airspeed to zero and then into negative values. This transition causes the aircraft to move forward while descending, leading to directional instability and increased pilot workload due to the need for frequent yaw pedal corrections. Furthermore, the loss of airspeed results in the loss of translational lift, and the aircraft requires significantly more power to decelerate and reach a hover when flying downwind compared to an into-wind approach.
Findings
- The pilot performed the approach in a downwind direction, which significantly increased the difficulty of the maneuver.
- The lack of airspeed led to a loss of translational lift and increased directional instability.
- The power required to arrest the increasing descent rate likely exceeded the available engine power.
- The pilot's limited flight experience and lack of recent flying contributed to the inability to manage the high workload created by the tailwind approach.