Incident Description
On Monday, 17 February 2003, at approximately 18:30 local time, a Piper PA-28R-180, registration EC-FHH, was involved in an incident at Valencia Airport. The aircraft, on a dual instruction flight, had departed Valencia around 16:00, proceeded to Castellón airfield for touch-and-go landings, and then returned to Valencia. During approach to runway 12, the landing gear was extended but the three green down-and-locked indicators did not illuminate initially. The crew retracted and re-extended the gear, after which the indicators showed all three green. The aircraft landed normally.
After reducing speed, the pilot turned left onto taxiway H-2. Shortly after entering the taxiway, the right landing gear unsafe warning light illuminated, and the aircraft began to sink on the right side. The pilot stopped the aircraft immediately, and both the instructor and student pilot evacuated. The airport fire service responded but no fire or fuel spill occurred. Maintenance personnel later inspected the right main landing gear leg and found broken components.
Aircraft and Crew Information
The aircraft was a Piper PA-28R-180 with a Lycoming O-360-B1E engine. The pilot in command, aged 28, held a commercial pilot license with single-engine, multi-engine, instrument, and instructor ratings. He had 1,400 total flight hours, including 500 hours on type. Both occupants were uninjured.
Damage and Investigation
The right main landing gear leg sustained damage: the forward pivot pin (tetón) was sheared, and the bolt connecting the pin to its housing was also broken. The rear pivot pin showed no significant marks. The damaged components were sent to the Instituto Nacional de Técnica Aerospacial (INTA) for analysis.
Macroscopic and microscopic examination confirmed that both the pivot pin and the bolt failed due to progressive fatigue fractures under purely mechanical action. No material anomalies were found. The analysis determined that the bolt had been subjected to inadequate torque during installation, which initiated fatigue cracks in both the bolt and the pin. The bolt's fracture occurred at the first thread root, where tensile stresses were highest.
Conclusions
The investigation concluded that the inadequate torque applied to the bolt caused fatigue phenomena affecting both the bolt and the pivot pin, ultimately leading to the fracture of both elements.