What happened
On 26 August 2022, a Pitts S-1S, registration G-BOXV, was performing aerobatic practice maneuvers over Shobron Airfield, Herefordshire. The pilot, an experienced instructor, initiated a vertical climbing roll from approximately 420 ft agl. As the aircraft reached the apex of the climb at roughly 1,100 ft agl, it experienced a right yaw. This caused the aircraft to enter an uncommanded, autorotative right roll, which transitioned into a steep, nose-down spiral dive.
As the aircraft accelerated during the descent, the pilot attempted to pull out of the dive. However, the increased g-loading triggered an accelerated stall and a further rolling departure to the right. Due to the low altitude and high rate of descent, there was insufficient height to recover before the aircraft struck a field near Runway 26. The impact resulted in a post-crash fire that destroyed the aircraft, and the pilot sustained fatal injuries.
The investigation
Investigators examined the wreckage and analyzed video footage from eyewitnesses and CCTV. The examination of the G-BOXV airframe and engine revealed no evidence of pre-existing technical failures or mechanical issues that could have caused the loss of control. While a left rudder cable was found fractured, this was determined to be a result of the impact and subsequent fire rather than a cause of the accident.
Analysis of the flight dynamics suggested that the aircraft was likely flying at a lower airspeed than intended during the transition from climb to descent. This reduction in speed likely diminished the aerodynamic effectiveness of the controls, making it difficult for the pilot to counteract the asymmetric lift that initiated the autorotative roll.
Findings
- The aircraft entered an autorotative right roll because the low airspeed at the apex of the manoeuvre reduced the pilot's ability to maintain control during the yaw.
- The pilot's attempt to recover from the spiral dive led to an accelerated stall due to high g-loading.
- The entry conditions for the vertical manoeuvre provided almost no safety margin for recovery once the aircraft began to deviate from the intended flight path.
- Entering the manoeuvre with greater speed or altitude would have significantly improved the chances of a successful recovery.