Piper PA-34-200T Landing Gear Failure at Cuatro Vientos Airport (EC-EUN)

Incident Overview and Location On Wednesday, May 4, 2005, at 16:40 local time, a Piper PA-34-200T with registration EC-EUN, operated by Aeromadrid, experienced a mechanical failure during the takeoff roll at Cuatro Vientos Airport in Madrid. The aircraft was conducting a general aviation flight for dual-command instruction. ## Sequence of Events and Damage The aircraft had traveled only approximately 10 meters down the runway when the left main landing gear leg failed. The forward and left sections of the aircraft subsequently struck the ground. The pilot in command and the student pilot, the only occupants, were uninjured and disembarked under their own power. The incident resulted in minor damage to the aircraft, specifically the rupture of the piston within the left main landing gear cylinder at its connection to the wheel axle fork. Additional minor damage included the left wing flap and the left propeller, whose blades were bent forward. ## Crew and Aircraft Details The pilot in command was a 54-year-old Spanish national holding a commercial pilot license. He had a total of 9,700 flight hours, including 800 hours on the aircraft type. The student pilot had 155 total flight hours. The aircraft, a 1979 Piper PA-34-200T (Seneca II) with serial number 34-7970213, was powered by two Continental TSIO-360-EB1B engines and equipped with Hartzell propellers. The aircraft had a total of 6,638 flight hours and was up to date with its required maintenance inspections. ## Investigation and Probable Cause The investigation focused on the fracture of the left main landing gear piston. Analysis of the fracture zone indicated that the failure was due to material fatigue. Typical fatigue marks, known as 'beach marks,' were observed. The fracture occurred around the through-hole of the screw that secures the piston to the fork, a structurally weakened area with high stress concentration. The investigation noted that while a previous FAA Airworthiness Directive required the replacement of the main structural component (trunnion) after 2,000 hours, it did not mandate the replacement of the piston. The manufacturer reported that the piston had no established history of failures and considered this incident isolated.