What happened
On December 13, 2003, at approximately 17:30, a Casa 1131-E Bucker, registration EC-GRB, was performing a local pleasure flight from the Casarrubios del Monte Aerodrome in Toledo, Spain. The aircraft was operated for agricultural work purposes, though this specific flight was for leisure. The pilot was accompanied by one passenger.
Following a normal takeoff from runway 08, the aircraft entered a left turn during the initial climb. During this maneuver, the engine suffered a sudden and complete loss of power. The pilot attempted to switch the fuel selector to the secondary position and activated the electric auxiliary fuel pump, but the engine failed to restart.
As the aircraft descended, the pilot identified a small depression to the left of the runway axis and decided to perform an emergency landing to avoid a rising mound of terrain. The aircraft struck the ground at approximately 50 knots, causing significant damage to the propeller, engine, left semi-wing, landing gear, and fuselage. The aircraft came to rest in a shallow, dry stream bed. The pilot sustained facial injuries, while the passenger remained uninjured. Both occupants escaped the aircraft using their five-point safety harnesses.
The investigation
The CIAIAC investigation focused on the engine's failure and the subsequent impact. Examination of the engine compartment revealed that the air filter, a sponge type impregnated with oil, was not in its proper housing. Instead, the filter had been sucked into the induction tube, obstructing the airflow to the fuel injector.
Investigators analyzed the air intake design, noting that the fiberglass housing lacked a support lip to secure the filter and safety mesh on the side leading to the induction tube. The investigation considered two possibilities for the filter'1s displacement: an incorrect installation during a recent 100-hour inspection, or a design flaw where engine suction could deform the mesh and allow the filter to pass through. While the inspection had involved cleaning and re-oiling the filter rather than replacing it, the investigation noted that the filter showed signs of being correctly installed previously, but the recent maintenance might have weakened its seating.
Findings
- The engine failure was caused by the suction of the air filter into the engine, which obstructed the airflow and led to a total loss of power.
- The air intake design lacked a physical stop or lip to prevent the filter from being pulled into the induction tube if the safety mesh deformed.
- The air filter had been cleaned and re-oiled during a recent 100-hour inspection rather than being replaced, which may have contributed to its displacement.
- The impact with the ground caused extensive damage to the landing gear, propeller, and left wing structure.