What happened
On 11 June 2025, a Robinson R66, registration G-WBRN, departed Denham Airfield for a private flight to Warwickshire. Although the pilot noted marginal weather conditions upon arrival, ground observations suggested the cloud base was higher than forecast, prompting a decision to proceed. Shortly after takeoff, the aircraft encountered low cloud at approximately 500 ft agl, transitioning from visual to instrument meteorological conditions.
To manage the flight while obscured, the pilot engaged the autopilot's stability augmentation system. During a climbing turn, the aircraft's speed dropped below 44 kt, causing the heading and altitude hold modes to disengage automatically. The pilot, frequently checking a navigation tablet, attempted to adjust the heading bug but was unaware the specific heading mode was no longer active. This led to significant spatial disorientation.
In an attempt to rectify the situation, the pilot disengaged the autopilot system entirely. Without the stability of the autopilot and lacking instrument flight training, the pilot lost control of the aircraft. The helicopter emerged from the cloud in an extreme attitude, eventually entering a rapid left yaw. The aircraft struck the ground in a field near Chalfont St Peter, resulting in significant damage to the rotor blade and empennette, though the pilot escaped without injury.
The investigation
The AAIB examined cockpit audio and video recordings, which provided a detailed timeline of the flight. The investigation focused on the transition from visual to instrument conditions and the subsequent pilot actions. Investigators analyzed the functionality of the Genesys Aerosystems HeliSAS autopilot and the impact of the pilot's use of a handheld tablet on situational awareness. The investigation also reviewed local meteorological reports from nearby airfields, which confirmed that the cloud base was lower than the pilot had anticipated.
Findings
- The decision to depart when weather conditions were marginal for VFR flight.
- A failure to turn back to the airfield when visual references began to deteriorate immediately after takeoff.
- The pilot's lack of instrument flight training, which prevented effective control of the aircraft in IMC.
- Confusion regarding the active modes of the autopilot system.
- Distraction caused by frequent glances at a navigation tablet, which interrupted the necessary scan of flight instruments.