Introduction
On 11 June 2025, a Robinson R66 helicopter, registration G-WBRN, was involved in an accident near Chalfont St Peter, Buckinghamshire. The helicopter was manufactured in 2023 and powered by a single Rolls-Royce 250-C300/A1 turboshaft engine. The flight was a private operation with one pilot on board and no passengers. The pilot held a Private Pilot’s Licence, was 64 years old, and had accumulated 1,020 flight hours, including 380 hours on type. The helicopter sustained significant damage to its empennage and rotor blade; the pilot reported no injuries.
History of the Flight
The pilot planned a flight from Denham Airfield, Buckinghamshire, to a private airstrip near Wellesbourne, Warwickshire. After checking the weather forecast and noting marginal conditions, the pilot conducted a ground observation and decided to depart as scheduled at 0700 UTC. The helicopter departed from Runway 06. At approximately 400 ft above ground level (agl), visual references deteriorated, and the helicopter entered instrument meteorological conditions (IMC) at around 500 ft agl while climbing in a left turn. The pilot engaged the autopilot, selecting stability augmentation system (SAS), heading hold (HDG), and altitude hold (ALT) modes. The helicopter stabilized at 600 ft agl and 85 kt.
During the flight, the pilot attempted to climb to find visual flight rules (VFR) conditions above the cloud, using the autopilot trim function. The climb resulted in a reduction in airspeed to 34 kt, causing the HDG and ALT modes to disengage. The autopilot re-trimmed in SAS mode. The pilot reported becoming disoriented and was surprised to find the helicopter on a westerly heading. He pressed the SAS button, which disengaged the autopilot system. The helicopter pitched nose-up to 15°, climbed 250 ft, and banked left to 35° angle of bank. The nose dropped, and the helicopter entered a descending left turn. The pilot attempted to re-engage the autopilot but the helicopter emerged from cloud at approximately 600 ft agl with a 2,000 ft/min rate of descent and a terrain warning. The pilot rolled level and pulled up, but the helicopter re-entered cloud, pitching to 60° nose-up. The pilot disengaged the autopilot again. The helicopter rolled right to approximately 170° angle of bank, emerged from the cloud nearly inverted at 450 ft agl with a 3,000 ft/min rate of descent. The pilot applied full power, but main rotor RPM fell below 80%, likely due to overpitching. The helicopter yawed rapidly left and struck the ground in a field next to a paddock with outbuildings. The total flight time was under five minutes, with 58 seconds from autopilot disengagement to ground impact.
Meteorological Conditions
The UK was under a high pressure system with good visibility and light south-easterly winds, giving rise to extensive low cloud in the south. The cloud was forecast to lift and break by midday. At the time of departure, London Heathrow Airport reported overcast cloud between 400 and 500 ft agl, and RAF Northolt reported broken cloud between 500 and 800 ft agl. The flight route included terrain elevations up to 350 ft between Denham and the Maple Cross visual reference point.
Aircraft Information
The Robinson R66 is approved for VFR day and night operations only. G-WBRN was equipped with a factory-fitted cockpit camera system and an optional Genesys Aerosystems HeliSAS autopilot. The cockpit camera recorded 4K video, intercom audio, radio communication, and GPS position.
Autopilot and Control System
The HeliSAS autopilot includes SAS, HDG, and ALT modes. The trim button temporarily suspends SAS operation and removes cyclic forces. During the flight, the pilot expressed confusion about autopilot modes. The autopilot was disengaged, leading to loss of control.
Post-Impact
The helicopter struck the ground heavily. The skids were splayed and flattened, the cross tubes fractured, and the left skid collapsed, causing the helicopter to roll over. The main rotor blade struck the ground, severing the tail rotor and propelling a 70 cm section of blade tip, weighing 4.5 kg, nearly 180 m over a road and a petrol station canopy into a wisteria on a house wall. No damage to the house was reported.
Probable Cause
The pilot was not qualified to fly on instruments alone, and an opportunity to turn around was missed when the weather encountered after takeoff proved to be as forecast. There appeared to be confusion about autopilot modes and the autopilot was disengaged, leading to the loss of control.