Event Description
On 27 July 2006, at 13:45 local time, a Piper PA-34-200T aircraft, registration EC-FDE, operated by Aeromadrid, was conducting an instruction flight from Cuatro Vientos Airport (Madrid) to Valladolid Airport. The aircraft carried an instructor and a student pilot. After approximately one hour and ten minutes of flight, the crew initiated a landing on runway 23. During the landing roll, as the main gear touched down, the aircraft began veering slightly to the right. The crew observed that the nose gear position indicator displayed an intermittent signal. They executed a go-around before the nose gear contacted the ground to investigate the issue. During the subsequent left-hand visual pattern, the landing gear was cycled and all three green lights indicated gear down and locked. After receiving clearance, the crew performed a second landing. About 300 meters down the runway, at low speed, the aircraft began tilting to the right. As it slowed, the right propeller and right wing contacted the ground. The aircraft came to a stop on the right side of the runway, resting on its right wing. There was no fire, and both occupants were uninjured. Emergency personnel responded promptly. Post-incident inspection revealed the right main landing gear had collapsed, with the wheel, wheel fork, and axle separated from the aircraft. Additional damage included the brake assembly, propeller blade tips, flaps, and main landing gear door on the right side, as well as the entry step.
Aircraft and Crew Information
The Piper PA-34-200T is a twin-engine aircraft equipped with two Continental TSIO-360-EB engines. At the time of the incident, the aircraft held a normal airworthiness certificate valid until 9 May 2006, with an extension to 9 August 2006. Total airframe time was 10,528 flight hours. The instructor, aged 29, held a Commercial Airplane Pilot License and a valid competency certificate. He had accumulated 3,200 total flight hours, with about 100 hours on the type. The student pilot was enrolled in an Airline Transport Pilot License course and held a valid student pilot license.
Investigation Findings
The post-accident inspection determined that the shock absorber piston in the right main landing gear leg had completely fractured. Laboratory analysis identified signs of progressive fatigue crack growth on the fractured area, with an area of brittle failure that occurred as the wheel separated during the landing. The crack originated on the surface of the lock screw for the plug at the lower end of the piston. The screws had a rough surface finish, which can initiate fatigue cracks. The fractured section of the piston is located in a region where stress concentrates under normal landing loads. The operator had added an inspection item to the 500-hour maintenance check, using a camera to inspect the interior of the piston. The most recent 500-hour inspection, conducted on 21 May 2006 at 10,480 flight hours, did not detect any defects in the piston. The aircraft failed 48 flight hours later, suggesting the crack may have progressed rapidly or the inspection method was ineffective. The maintenance manual did not require any specific crack detection or non-destructive testing for the piston. The piston was not a component with a limited service life. The investigation noted three previous cases of trunnion fracture in service across the fleet. The manufacturer conducted a safety risk assessment and concluded that no design or maintenance changes were necessary.
Conclusions
The incident resulted from the fracture of the shock absorber piston on the right main landing gear leg, which had been weakened by a fatigue crack. The crack was not detected during the operator's maintenance inspection. The piston is not a limited-life component, and no special inspection techniques were mandated. The risk assessments did not indicate a need for design or maintenance amendments.