What happened
On October 13, 2004, a Piper PA-34-200T, registration EC-FMX, was performing a positioning flight from the Casarrubios del Monte Aerodrome to Madrid/Cuatro Vientos. Prior to departure, the pilot had conducted ground checks of the braking system following a recent maintenance inspection of the brakes.
During the takeoff roll on runway 26, approximately 80 meters from the start of the runway, the nose gear collapsed. This caused the forward section of the fuselage and both propellers to impact the runway pavement. The aircraft continued to slide on its forward fuselage for an additional 8 and 80 meters before coming to a halt. The two occupants of the aircraft were uninjured and able to egress the aircraft on their own.
The investigation
The investigation focused on the mechanical state of the nose gear and the condition of the runway surface. Examination of the nose gear assembly revealed that the downlock link assembly was not properly secured. Specifically, the length of the tensioner element was insufficient to allow the drag link to reach its correct position, meaning the gear was held in place only by hydraulic pressure.
Upon inspection of the link assembly, investigators found that the screw stud connecting the assembly to the drag link was bent near the head. This damage likely occurred during the gear collapse. Furthermore, the investigation noted that the aircraft had recently undergone significant maintenance involving the installation of a new nose gear strut, during which the improper adjustment of the tensioner likely occurred.
Additionally, the runway surface at Casarrubios del Monte was found to be in poor condition, characterized by deep cracks and significant irregularities, including asphalt ridges and potholes. The investigation determined that these surface defects subjected the landing gear to extreme loads during the takeoff roll.
Findings
- The primary cause of the nose gear failure was the incorrect adjustment of the length of the downlock link assembly tensioner.
- The deteriorated condition of the runway pavement, including significant cracks and uneven surfaces, acted as a contributing factor by increasing the mechanical loads on the nose gear.
- The improper adjustment of the tensioner likely occurred during recent maintenance work involving the installation of the nose gear strut.
- The hydraulic system's pressure relief valves likely opened due to the high-pressure spikes caused by the aircraft traversing the uneven pavement.