2020 Robinson R44 Accident at Herne Bay (G-WTWT)

Accident Overview and Aircraft Details On 26 July 2020 at 0904 UTC, a Robinson R44 Raven II helicopter, registration G-WTWT, crashed near Herne Bay, Canterbury, Kent. The aircraft, manufactured in 2019 with serial number 14294, was powered by a single Lycoming IO-540-AE1A5 piston engine. The private flight was operated by a 53-year-old pilot holding a Private Pilot’s Licence, with 400 total hours of experience, including 268 hours on type. The helicopter was carrying one crew member and three passengers. ## Flight History and Initial Incident The pilot departed from Orsett near Thurrock, where the helicopter was based, to fly to a friend’s house near Herne Bay. The initial flight was uneventful, and the helicopter landed near Maypole airfield. After the first landing, the pilot kept the rotors running while passengers changed. During the subsequent takeoff to the west, the pilot noticed that the left front door was not fully closed, with a gap of approximately half an inch. Attempts to close the door in flight were unsuccessful, prompting the pilot to decide on a precautionary landing in a nearby field. ## Approach and Crash Sequence While preparing for the precautionary landing, the pilot believed he was heading north and planned a crosswind approach. However, he inadvertently turned right and was actually tracking northeast, making a downwind approach. As the helicopter descended below 100 feet, the rate of descent exceeded 1,000 feet per minute, and the airspeed dropped below 15 knots. The helicopter did not respond to collective or cyclic inputs, and the pilot was unable to arrest the descent. The aircraft struck the ground with the right skid first, dug into the soil, and rolled onto its right side. ## Injuries and Damage The crash resulted in substantial damage to the helicopter. The pilot and two of the three passengers sustained minor injuries. All occupants were able to exit the aircraft, with the pilot and front-seat passenger assisting the rear-seat passengers. Emergency services arrived shortly after the impact. ## Investigation Findings and Probable Cause The UK Air Accidents Investigation Branch (AAIB) determined that the helicopter likely entered a vortex ring state during the downwind approach. Vortex ring state is an aerodynamic condition characterized by a sudden loss of rotor thrust and rapid loss of height, typically occurring when power is applied, the rate of descent is high, and indicated airspeed is low. The pilot was unaware of the downwind approach and did not recognize the onset of vortex ring state, preventing corrective action. The investigation also noted the hazard of passengers boarding with rotors running, which can make it difficult for pilots to confirm doors are properly closed, and the risk of pilot distraction from minor in-flight issues.