What happened
On November 3, 2010, a PIPER PA-31-200 Seneca III, registration EC-KTT, was performing a takeoff roll from runway 28 at Madrid-Cuatro Vientos Airport. The flight was a training/verification flight intended to renew multi-engine and instrument ratings, with an authorized examiner and two pilots on board.
During the takeoff roll, after covering approximately one-third of the runway length, the nose landing gear collapsed. The pilot in command, who was undergoing verification, was at the controls when the incident occurred, at which point the examiner took control. The aircraft veered from the runway centerline toward the left edge of the runway, traveling approximately 180 meters. During this excursion, the nose gear bay doors dragged along the asphalt. The aircraft eventually came to a stop near the intersection of the runway and taxiway E2. The aircraft rested on its main landing gear before the left main gear also collapsed, leaving the left wing on the ground. The propeller blades sustained damage from striking the ground. All three occupants were uninjured and evacuated the aircraft safely.
The investigation
The investigation focused on the mechanical state of the landing gear and the actions of the crew. Post-incident inspections revealed that the fuel mixture, propeller pitch, and throttle were all in the appropriate positions for the phase of flight, and the landing gear lever was in the down position.
Technical examinations of the nose gear assembly, including the down lock link and overcenter mechanism, showed no defects, improper adjustments, or structural deformities. The down lock link complied with all manufacturer service bulletins and airworthiness directives. Functional tests performed on the aircraft following the repair of a damaged hydraulic line demonstrated that the landing gear could extend and retract normally, with the gear locking securely in the down position and cockpit indicators functioning correctly.
Findings
- The investigation could not definitively confirm the exact trigger for the gear collapse, as the hydraulic system lost fluid during the inspection process.
- The nose gear mechanism and the down lock link were found to be in proper working order and properly adjusted according to maintenance manuals.
- The most probable cause was the inadvertent movement of the landing gear lever while the aircraft was on the ground with the electrical system energized.
- It is believed that as the aircraft gained speed and the struts began to extend, the squat switch activated the hydraulic pump, initiating the retraction cycle because the overcenter mechanism was no longer held in the locked position.