What happened
On April 18, 2006, a SCHEMPP-HIRT NIMBUS-4DM, registration OH-948, was performing a private local flight at the Beas de Segura aerodrome in Jaén, Spain. During the initial climb after takeoff, the pilot detected coolant temperature warnings. After two attempts to stabilize the temperature by reducing engine RPM, the temperature reached the 110 °C limit. The pilot subsequently shut down the engine and began the procedure to retract the propeller for a glider landing.
While performing the landing approach, the pilot initially intended to land on runway 34. However, upon noticing a vehicle near the runway threshold, the pilot attempted to redirect the aircraft to runway 27. Due to the low altitude and high descent rate, the aircraft was unable to complete the turn safely. The aircraft struck the runway at a heading of approximately 280/285°, bounced onto the grass, and veered into a fuel station facility located near the hangars. The impact caused significant damage to the left wing, the fuselage pylon, and various control surfaces. The two occupants escaped the aircraft without injuries.
The investigation
The investigation focused on the engine's failure and the sequence of the landing maneuver. Technical analysis of the engine by the manufacturer revealed that the engine had lost all its coolant due to a crack in the first cylinder. This crack was caused by vibrations from the carburetor and intake manifold assembly, which occurred because a mounting bolt had not been properly tightened or secured.
Flight data from the onboard logger confirmed the engine's temperature fluctuations and the pilot's maneuvers, including the steep turns and the descent rate. The investigation also examined the pilot's workload, noting that the simultaneous tasks of retracting the propeller and managing the engine failure at a low altitude contributed to the difficulty in identifying runway obstacles in time.