What happened
On July 5, 1997, a Socata TB 10 was conducting a training flight at Schönhagen Airfield, Germany. The flight was intended to provide type transition training for a pilot with approximately 60 hours of total experience. On board were the flight instructor, the trainee pilot, and her husband.
During the third circuit, the aircraft performed a touchdown and go-around maneuver. The aircraft touched down late, at the halfway runway marker, and did not lift off again until it reached the very end of the runway. Following the takeoff, the aircraft exhibited a very shallow climb gradient. As it approached the treeline adjacent to the runway, the stall warning activated, indicating a critical flight condition due to low airspeed. The aircraft struck the trees approximately 1.5 km from the airfield, causing the airframe to break apart. The impact ruptured the wing fuel tanks, leading to an immediate post-crash fire.
Tragically, the trainee pilot died at the scene. The flight instructor and the passenger sustained severe burns; the instructor later succumbed to his injuries in the hospital. The third occupant survived.
The investigation
The BFU investigation focused on the aircraft's climb performance and the engine's operational state. Investigators examined the engine, a Lycoming O-360-A1AD, which had only 95 hours of time since its last overhaul. Analysis of the cylinders revealed unusually heavy carbon deposits and significant oil fouling on the spark plugs in cylinders 1 and 3, which was inconsistent with the low engine hours.
Investigators also reviewed the aircraft's maintenance history, noting that the owner was aware of previous engine power loss issues characterized by intermittent ignitions. While the aircraft was legally airworthy, the investigation looked into whether configuration errors—such as the position of the flaps, propeller pitch, or carburetor heat—contributed to the insufficient climb rate.
Findings
- The primary contributing factors were the late touchdown at the halfway marker and the subsequent insufficient climb performance.
- The engine's power output was likely reduced due to spark plug fouling, potentially caused by an excessively steep approach and prolonged idling, which prevented the plugs from self-cleaning.
- Evidence of heavy oil deposits suggested an unnaturally high oil consumption, likely stemming from inadequate honing during the engine's previous overhaul.
- The aircraft was operated despite known engine irregularities, as the owner had previously experienced power loss during ground tests.
- The investigation could not definitively confirm the exact configuration of the flaps or propeller pitch at the moment of takeoff, though the flaps were found in the retracted position after the crash.