What happened
On May 23, 2014, at approximately 18:05 local time, a Klemm 107 (Kl 107B) crashed approximately 550 meters southeast of the Neuburg Egweil (EDNJ) airfield in Germany. The aircraft was conducting a private sightseeing flight with a pilot and two passengers, heading in an easterly direction.
Witnesses at the airfield reported hearing unusual engine noises and observing the aircraft at an altitude of approximately 10 meters. Observers noted that the aircraft initiated a right-hand turn. One witness observed that the aircraft's angle of attack appeared to increase as its airspeed decreased. The aircraft subsequently entered a nearly vertical descent, impacting a wheat field. All three persons on board were killed in the impact.
The investigation
The BFU investigation examined the aircraft's mechanical condition, the pilot's experience, and evidence recovered from the wreckage. Digital evidence played a crucial role; photos taken by a passenger in the front right seat just after takeoff showed the aircraft at 120 km/h, climbing at 1 m/s, with the engine at 2,480 RPM. These images also revealed the fuel selector was set to tank number one.
Engine analysis revealed a fouled spark plug in the third cylinder, which had developed a bridge between the electrodes. This condition, likely caused by prolonged idling or insufficient high-power running prior to takeoff, could lead to an uneven engine run or reduced power. However, investigators found no evidence of a total engine failure or mechanical defect that would have prevented a safe landing in the nearby fields.
Findings
- The aircraft was operating at the rear limit of its allowable center of gravity.
- The engine experienced a potential power reduction due to a fouled spark plug.
- The Klemm 107 lacked a stall warning system, which is common in older aircraft of this type; a stall is only preceded by a slight vibration in the tail.
- The aircraft entered a stall during a turn because the airspeed dropped below the minimum required for that flight state.