What happened
On 3 February 2019, a Luton LA4A Minor, registration G-AWMN, was performing a test flight at Waits Farm, near Belchamp Walter, Essex, to renew its Permit to Fly. The pilot was conducting the flight alone. Witnesses observed the aircraft climbing away from the airfield, heading north-east, at which point it appeared to be traveling slowly. Shortly after, the aircraft was seen banking sharply to the right and descending at a steep, nose-down angle toward the ground. Witnesses reported hearing the engine noise cease before the impact. The aircraft struck a harvested field and was subsequently destroyed by an intense post-impact fire. The pilot sustained fatal injuries.
The investigation
The AAIB investigation focused on the engine performance and the integrity of the flight controls. Examination of the Volkswagen-derived engine revealed that the combustion chambers and piston crowns lacked the typical brown coloring of a normally functioning engine, instead displaying a black finish indicative of an over-red mixture. This condition is often associated with significant carburettor ice formation.
Regarding the flight controls, investigators discovered that a turnbuckle barrel from the aileron balance cable was missing. While the wire locking was still present, the absence of the barrel could not be definitively linked to a pre-flight condition or a failure during flight. The investigation also noted that the aircraft's engine was capable of producing power, but the propeller damage was consistent with an absence of power at the moment of impact.
Findings
- The engine may have ceased producing power due to carburettor icing, a risk heightened by the cold temperatures and high humidity present at the time.
- It is possible that the pilot, unable to maintain sufficient airspeed following a loss of power, entered a stall from which recovery was impossible at such a low altitude.
- A turnbuckle barrel was missing from the aileron balance cable, though the cause of its absence remains undetermined.
- The aircraft's impact and subsequent fire resulted in a non-survivable event.