What happened
On 5 July 2015, a Rans S6-ES, registration G-CDVF, was engaged in a private flight from Shifnal Airfield in Shropshire. The flight involved the pilot and one passenger. Prior to the accident, the aircraft had completed four successful circuits and landings, although the pilot noted that the engine performance felt sluggish during these maneuvers.
While preparing for a fifth takeoff, the engine began running roughly and experienced a drop in RPM, though it subsequently recovered. After performing a magneto drop check and two high-power engine runs, the pilot determined the engine appeared to be operating normally and proceeded with the takeoff. However, once the aircraft reached an altitude between 100 ft and 20 and 200 ft AGL, the engine RPM decreased without command. This loss of power caused the aircraft to lose altitude and strike the ground in a steep, nose-down attitude. A small fire broke out following the impact, which was extinguished by a bystander. Both the pilot and the passenger sustained serious injuries.
The investigation
The AAIB examined the wreckage, which had been moved from the site by members of the flying club. Due to the disassembly of the aircraft at the accident site, all fuel was lost, making it impossible to test for contamination. The damage to the aircraft was substantial enough to prevent operational testing of the engine, ignition system, or carburettors.
An inspection of the engine revealed no evidence of major mechanical failure. The mechanical fuel pump was found to be functioning correctly, the fuel filter was clean, and the spark plugs showed no signs of abnormal use. Additionally, the carburettors, which were equipped with heaters to prevent icing, showed no pre-impact defects.
Findings
- The engine, fuel supply, and control systems showed no evidence of pre-existing defects that would have prevented normal operation.
- Because the aircraft had completed several successful flights immediately prior to the accident, widespread fuel contamination was considered unlikely.
- An intermittent defect within the ignition system could not be ruled out as the cause of the uncommanded RPM reduction, as the damage prevented a full test of the system.