Incident Overview
On September 22, 2006, a single-engine experimental aircraft, identified as a BX-2 Cherry with registration PH-OOY, experienced an in-flight emergency during an overland flight from Teuge to Stadlohn (EDLS) in Germany. The aircraft was piloted by its owner, who had approximately 2,000 total flight hours and about 1,200 hours on type, accompanied by one passenger holding a pilot license. Both individuals remained unharmed following the incident.
Sequence of Events
The take-off from Teuge proceeded normally. Approximately four minutes into the flight, at an altitude of roughly 1,600 feet, the pilot reduced engine power and observed that the RPM dropped more than expected. Upon selecting more power, the engine threatened to stall. The pilot subsequently reduced power again, leaving the engine running at idle. Due to extensive radio communications with the airfield, the pilot lost track of altitude loss. At 700 feet, realizing the runway could not be reached, the pilot initiated an emergency landing in a beet field near Wilp.
During the approach, the pilot attempted a belly landing by retracting the landing gear at approximately 50 feet. Upon touchdown, the right wingtip struck the ground, causing the aircraft to rotate 90 degrees to the right and slide for about 50 meters until it came to rest. The exhaust system detached, and the propeller sustained irreparable damage.
Investigation Findings
Investigators from the Dutch Safety Board (Onderzoeksraad voor Veiligheid) found an oil trail on the engine cowling and the right side of the fuselage. The oil sight glass, used to monitor the oil level in the BMW R1100S boxer engine, was missing. Evidence indicated that the glass had been forced out of the engine block by increased crankcase pressure.
The aircraft utilized a non-standard crankcase breather system developed by amateur builders. Tests with identical engines showed that while normal crankcase pressure is around 0.5 bar, a blocked breather can cause pressure to rise to approximately 4 bar, exceeding the strength of the sight glass fitting. The investigation concluded that the loss of oil led to engine failure, necessitating the emergency landing.