What happened
On 20 June 2017, a Kolb FireFly, registration G-CEPN, departed from Cottered Airfield for a private flight. Shortly after takeoff, approximately one mile from the runway, the aircraft entered a sharp, descending left turn. CCTV footage captured the aircraft flying in a stable, level manner for a brief period before it rolled abruptly to the left and entered a steep dive. The aircraft struck the ground vertically near Newell Lane, L amongst the trees. The pilot, who had extensive flying experience but had not flown for several months, sustained fatal injuries.
The investigation
Investigators examined the wreckage and reviewed CCTV footage from a nearby residence. The footage allowed for a calculation of the aircraft's performance immediately prior to the maneuver, showing a groundspeed between 38 and 46 mph at an altitude of roughly 120 ft agl.
Technical inspections of the Kolb FireFly focused on the engine, controls, and structural integrity. The engine, a Fuji Robin 330, was found to be in working order, and the carburetors contained fuel with no signs of malfunction. While the aileron control circuit's universal joint was found broken, evidence indicated the joint was intact and correctly rigged at the time of impact. All wing attachment pins and bolts were secure. The damage to the propeller blades and the wing spars was determined to be the result of structural overload caused by the impact with the ground rather than a pre-existing failure.
Findings
- The aircraft was flying at a speed above its predicted stall speed immediately before the sudden roll.
- There was no evidence of mechanical failure or engine defect that would have prevented the aircraft from responding to control inputs.
- The pilot showed no signs of medical incapacitation, and toxicology reports were negative.
- It remains undetermined why the aircraft departed from controlled flight, as no in-flight structural failure or stall was identified.