Ryanair Boeing 737-800 Front Landing Gear Axle Failure at Treviso (EI-CSN)

Event Overview and Aircraft Details On 25 June 2007, a Boeing 737-800 with registration EI-CSN, operated by Ryanair as flight FR9513, departed Girona (LEGE) at 16:38 UTC for Treviso S. Angelo (LIPH). The aircraft carried 174 passengers and 6 crew members. The flight proceeded normally, and the aircraft was cleared for an ILS approach to runway 07. ## Landing and Immediate Aftermath The aircraft landed at 15:46 UTC (17:46 local time) with a mass of 63,400 kg and a speed of 138 knots. Weather conditions were favorable, with visibility over 10 km and light winds. Shortly after the nose gear touched down at a speed just over 100 knots, the crew reported a loud noise and a slight left roll, which was quickly corrected. ## Damage and Investigation During taxiing, the crew discovered a broken axle on the front landing gear, resulting in the loss of the left front wheel. The wheel was found two days later on the airport grounds. The aircraft sustained damage to the front landing gear axle and the left front gear door, with no injuries to passengers or crew. ## Technical Analysis Fractographic and metallurgical analyses confirmed that the axle failure was caused by stress corrosion cracking (SCC). The mechanism was initiated by general corrosion and pitting on the component's external surface. The failure occurred at a cycle count of 15,309, well below the design life of 75,000 cycles. The affected area was not covered by the C1 inspection corrosion checks because it was located under a spacer that was not removed during that maintenance task. ## Safety Recommendations Following the incident, a safety recommendation (ANSV-8/4197/1/A/07) was issued on 26 July 2007, suggesting a one-time visual corrosion inspection for all B737 models equipped with the same component. No further safety recommendations were deemed necessary after this action and previous recommendations related to a similar event involving another B737 (EI-COI) in 2006.