What happened
On July 18, 2013, a pilot was conducting maintenance on his amateur-built Murphy Renegable Spirit at the Trier-Föhren airfield. Following modifications to the airfoils, the pilot intended to perform a test flight. The aircraft departed from runway 05 at 12:20 local time.
During the initial climb, at an altitude of approximately 80 to 100 meters, the engine experienced a significant power loss, with RPM dropping from 6,100 to 3,800. In response to this failure, the pilot attempted a shortened and tight pattern to return to the airfield. While executing a right-hand turn, the pilot observed a construction crane and attempted to fly over its boom. This maneuver resulted in an excessive flight attitude. The aircraft subsequently entered a nose-down pitch that could not be recovered before impacting a wheat field approximately 240 meters northeast of the threshold of runway 22.
The airfield controller reported that the pilot had communicated via radio regarding engine problems and an intention to return to the field. The controller witnessed the aircraft pitching forward during the right turn and striking the ground.
The investigation
The BFU examined the wreckage and the engine components. The investigation noted that the aircraft sustained heavy damage, including a broken right lower wing, a deformed fuselage up to the rear seat, and a detached landing gear. The propeller blades were separated from the hub.
Upon inspection of the engine, investigators found that the spark plug of the front cylinder was hanging from the ignition cable. The first two threads of the spark plug thread showed aluminum erosion, and the gap electrode had been pressed against the center electrode. The spark plug thread in the front cylinder was damaged, and soot deposits were present around the spark plug opening. The remaining spark plugs showed healthy, light-brown combustion patterns.