What happened
On 7 September 2022, a CZECH AIRCRAFT WORKS Sport Cruiser, registration EC-ZXG, was conducting a private flight from Córdoba Airport to Mutxamel Aerodrome as part of the Vuelta Aérea España 2022 competition. The aircraft was carrying a pilot and one passenger.
While cruising at approximately 5,500 feet near the 'S' waypoint, the occupants experienced violent engine vibrations and a noticeable reduction in propeller traction. The pilot attempted several procedures to restore engine performance, including activating the fuel pump and carburetor heat, and switching fuel tanks, but these actions were unsuccessful.
In an attempt to land on runway 12 at Mutxamel, the pilot performed descending spirals and a slip maneuver to lose altitude. However, the aircraft approached the runway at a speed of 73 knots, which was significantly above the recommended 54 knots for a full-flap approach. Due to the high speed and altitude, the pilot overflew the runway and attempted a go-around. During this attempt, the engine failed to provide sufficient power for a climb, leaving the aircraft unable to return to the circuit or execute a 180-degree turn. The pilot subsequently declared a MAYDAY and attempted to reach an empty parking lot, but ultimately performed an emergency landing in a concrete drainage channel between several roads. The pilot sustained serious injuries, while the passenger suffered minor injuries.
The investigation
The CIAIAC examined the engine, propeller, and control systems. While the propeller and gearbox were found to be in good working order, the investigation revealed several maintenance deficiencies. The inspection of the engine showed that the fuel pump, lubrication, and cooling system hoses were out of date. Additionally, the spark plugs in cylinders No. 1 and No. 3 showed signs of poor carburation, with a defective electrode found in the No. 1 plug.
Crucially, investigators found that the carburetor throttle spring on the 1/3 side was loose due to material wear on the throttle lever and the plastic guard. This caused a desynchronization between the carburetors, preventing the engine from accelerating correctly and causing the observed vibrations.
Findings
- The primary cause of the accident was an emergency off-airfield landing necessitated by a loss of engine power, likely resulting from poor maintenance.
- The loose throttle spring caused the engine to fail to accelerate properly, leading to engine desynchronization and vibrations.
- The aircraft was poorly maintained, as evidenced by the worn throttle lever, out-of-date hoses, and improper carburetor condition.
- The pilot's approach to the runway was characterized by excessive speed and altitude, which led to the failed landing attempt and subsequent go-around.
- The selection of the emergency landing site was inappropriate, as the pilot was unable to reach the intended parking area.