What happened
On June 1, 2008, at approximately 16:10, a pilot and a passenger departed from the Sauldorf-Boll ultralight airfield for a recreational flight intended to visit Lake Constance. Around 16:30, witnesses observed the Comco Ikarus C 22B flying at a low altitude and slow speed, approaching from the south.
As the aircraft attempted to clear a line of trees adjacent to the B 14 highway near the "Oberer Wiedenholzerhof," the wingtip struck a tree branch. Following this impact, the aircraft began to roll around its longitudinal axis and plummeted into a nearby agricultural building. The cockpit of the aircraft breached the roof of the barn, and the impact resulted in two fatalities.
The investigation
The BFU examined the wreckage of the aircraft and the engine components to determine the cause of the loss of control. The investigation focused on the condition of the Jaribu-2200 engine, the fuel system, and the recent maintenance performed by the pilot. Investigators inspected the carburetor, fuel filter, and spark plugs, as well as the cylinder and piston assembly.
Findings
Technical analysis of the engine revealed significant internal issues. Scuffing and grinding marks were found on one of the cylinders and the piston, and the piston crown was encrusted with oil carbon. Additionally, oil was found leaking from a damaged exhaust valve into an exhaust pipe. The condition of the spark plugs and the engine components indicated a loss of power in the front left cylinder.
In the fuel system, the Bing carburetor showed signs of contamination; the float arms were bent, and impurities were present in both the fuel filter and the carburetor. Furthermore, the jet needle in the carburetor was coated with a black deposit, and similar deposits were found within the float chamber. Scuffing and abrasion marks were also noted on the inside of the carburetor housing and on a metal extension used for the throttle Bowden cable.