What happened
On June 4, 2019, a Cessna 172 (registration EC-DCP) operated by Cinetic Plus departed from Madrid/Cuatro Vientos airport for a local visual flight training session. Shortly after takeoff, while climbing toward 3,000 feet, the flight instructor attempted to reduce engine power. However, the throttle lever failed to influence the engine's output, leaving the engine stuck at maximum power.
The instructor declared an emergency and coordinated with air traffic control to divert to the nearby Geta/Getafe Air Base. To manage the situation, the instructor eventually shut off the fuel supply to stop the engine while over the airfield. During the emergency landing on runway 23, the aircraft failed to maintain a stabilized approach. The aircraft touched down on a paved area to the right of the runway, crossed the runway at a 30-degree angle, and traveled 650 meters—much of which was off the paved surface—before coming to a stop. Both the instructor and the student remained uninjured, and the aircraft sustained only minor damage.
The investigation
The CIAIAC investigation focused on the mechanical failure of the throttle linkage and the circumstances of the landing. Investigators examined the engine compartment and discovered that the connection between the throttle lever and the engine injection control had become disconnected. Specifically, the pin and nut securing the throttle linkage to the injector cam were missing.
The investigation noted that recent maintenance performed by Sinma Aviación had involved replacing several engine components, including the fuel injection system. The findings suggested that while the securing nut was likely installed, it had not been properly safety-wired or secured with a locking device. Furthermore, the investigation highlighted that the pilot's inability to maintain the runway centerline was due to the high aerodynamic drag caused by the propeller being stopped in a fine pitch position, which significantly altered the aircraft's glide characteristics compared to standard engine-idle training.
Findings
- The primary cause of the engine malfunction was the disconnection of the throttle linkage from the engine injection control.
- The failure was likely due to a maintenance error where the securing nut was not properly safety-wired.
- The emergency landing was characterized by an unstabilized approach, as the pilot could not maintain the runway centerline due to the unexpected drag from the stopped propeller and an inability to accurately estimate the aircraft's energy during the glide.
Safety action
- REC 30/21: The maintenance organization, Sinma Aviación (ES.145.113), is recommended to implement and effectively perform independent second inspections or double-checks on all safety-critical or sensitive maintenance tasks, in accordance with EASA Part M or Part ML regulations.