Cessna T210N Landing Incident at Alicante Airport (EC-FSU)

Incident Overview and Flight Details On May 25, 2004, at 19:30 UTC, a privately operated Cessna T210N, registration EC-FSU, departed Alicante Airport for a local training flight. The aircraft was equipped with a single Teledyne Continental TSIO-520-R9B engine. The pilot in command, a 35-year-old commercial pilot with 4,288 total flight hours, was accompanied by an instructor in the right seat. The flight was intended to prepare for the pilot's single-engine piston (SEP) license renewal under JAR-FCL regulations. During the flight, the crew performed all required maneuvers for the renewal. Upon returning to Alicante, the aircraft joined the downwind leg for runway 10 and was configured for landing with the landing gear extended. The pilot executed a long landing to avoid turbulence from preceding heavy traffic. The landing was described as somewhat abrupt, and the instructor assessed that the aircraft touched down on the main landing gear. Subsequently, the main gear retracted, while the nose gear remained down and locked. The aircraft then rested on its tail and dragged for several meters before exiting the right side of runway 10. Once stopped, the crew secured the aircraft by cutting the fuel and electrical systems and then evacuated. No injuries were reported, and the aircraft sustained minor damage. The right horizontal stabilizer was damaged by friction and deformation, and the rear lower fuselage was damaged where it rested after the gear retracted. The tires showed superficial marks on their tread, perpendicular to their plane of rotation, from sliding on the runway with the gear almost fully retracted. No other damage occurred. The aircraft was later flown to its workshop after the damaged horizontal stabilizer was replaced. In the workshop, the aircraft was placed on jacks and fifteen complete landing gear cycles were performed. The electro-hydraulic system, which includes a single electric pump and a manual emergency pump, was tested using an external battery group. The control lever was operated normally six times, with correct function and warning lights indicating the gear position as per the flight manual. The time for the gear to lower was seven seconds in all cases. Nine interrupted cycles were then performed by placing the lever in intermediate positions and connecting/disconnecting the pump breaker. Cycles were only completed when the lever was in the correct position. The lights functioned correctly in all cases, indicating the actual gear position. The mechanical system was inspected, and no failures or deformations were found that could indicate a failure due to a hard landing. The locking pins functioned in the correct sequence and, once locked, prevented the gear from unlocking even after the hydraulic pressure was voluntarily released. No hydraulic leaks were observed. The gear warning light circuit remained active even after the hydraulic pump power was removed, as per the maintenance manual. The lights only indicated gear up or down when the gear had reached the corresponding position. When the system pressure was removed with the gear up, the nose gear lowered by gravity and locked, despite not having the aid of airflow received in flight. This did not happen with the main gear. When the normal gear lowering procedure was initiated, the nose gear descended immediately and locked in three seconds. Photographs were taken, and it was confirmed that the marks on the fuselage and wheels were compatible with the sequence of the incident described by the crew. The landing gear has a simple actuation mechanism. An electrically driven hydraulic pump provides the pressure needed to activate three independent actuators: one for the nose gear and one for each main gear leg. When the gear is up, it is held in that position by the hydraulic pressure of the circuit, with no pressure accumulator. Therefore, when the pressure falls below a threshold due to small leaks (normally in the actuators), the pump automatically connects to restore it. When the gear is down, pins ensure the gear is in the correct position (overcenter). Positive hydraulic pressure is required to lift them from their position, so the gear does not release unless the mechanisms and/or their supports are broken, none of which was observed on this aircraft after the incident. The green 'gear down' light is actuated by a set of three limit switches connected in series, so the failure of one to actuate prevents the light from turning on. The same applies to the yellow light indicating 'gear up'. No light is on during transit. As indicated above, the function of these circuits was correct, as was the calibration of the limit switches. It is noteworthy that the instructor did not state in his declaration that he personally saw the green gear light on, but that the student at the controls 'called gear down'. The investigation considered and discussed five hypotheses about the circumstances of the incident. The first hypothesis, that the crew did not extend the landing gear, was not viable because the aircraft touched down with the nose gear down and locked, and the main gear wheels showed signs of having dragged perpendicular to their tread. Additionally, the pilot in command remembered that the impact on the runway was 'on the main gear'. The second hypothesis, that the crew extended the landing gear, which remained down and correctly locked at the time of landing, was also not acceptable, as no part of the gear mechanism was broken or deformed. Furthermore, for the main gear to fold into its well, once the pins were broken, the aircraft would have had to jump appreciably to allow the legs to lower enough to start moving backward. The third hypothesis, that the crew extended the landing gear, but the pump failed (the circuit breaker tripped) or the battery was low and did not provide enough power, leaving the nose gear locked by gravity and relative wind, was considered. The source text is cut off here, but the analysis continues to discuss the remaining hypotheses.