EASA's most recent airworthiness directive warned Airbus A380 operators about possible cracks in the ribs of the fittings that attach the left (LH) and right (RH) main landing gear (MLG) to the wing. During the scheduled lubrication of the Airbus A330 MLGs, EASA detected an increasing number of corrosion or unexpected cracks in the protrusions of the landing gear attachment rib 6 on both sides of the wings.
“Analysis of the findings revealed that the root cause of these cracks is a complex combination of intergranular attack, corrosion and friction of the installed bushings.”
EASA warned that this condition could reduce the structural integrity of the aircraft's primary structure. However, maintenance checks of the A380s resulted in the discovery of cracked sealant in the bushings of the gear 9 rib fittings, used to attach the LH and RH MLG to the wing.
The European regulator highlighted that the bushings for the gear 9 rib fittings are similar to the fittings installed on the A330 and A340 aircraft. To resolve the issue on the latter aircraft, EASA issued an emergency AD (EAD) on 12 December 2006, which was superseded by several subsequent directives.
The most recent AD related to the A330 and A340 aircraft issue was issued on September 21, 2016, after Airbus developed a modification (mod 205205 and mod 205492) to address cracks in the rib terminals of production aircraft. Modifications 205491 and 205724 were applied to in-service A330/A340 aircraft, requiring rework of the LH and RH MLG 6 rib terminal assemblies.
It was also highlighted that whilst cracked sealant does not pose a direct risk to flight safety, it can increase the chance of moisture penetrating the terminal and bushings, which can potentially increase the risk of terminal bore corrosion over time. . If left untreated, this condition can result in cracked ribs, EASA warned.
“Airbus has determined that timely detection of cracks in the A9 landing gear rib 380 docking lugs is necessary and has issued SB (Service Bulletin) A380-57-8148 and SB A380-57-8269, to provide instructions for inspecting the landing gear accessory terminals of rib 9 (LH and RH) for cracks and the condition of the sealant of the bushings installed in these gear ribs, respectively.”
As a result, EASA mandated that operators conduct repetitive inspections of the LH and RH wing landing attachment (WLG) rib 9 fittings. Although the AD had an effective date of July 30, the European regulator warned that the directive was considered provisional and that further action could follow.
The guidance specified that operators inspect WLG LH and RH attachment fittings 9 within six months or before exceeding 500 flight cycles, whichever comes first, from the effective date of the AD. Alternatively, operators must perform the inspection within 18 months or before exceeding 800 FC, whichever occurs first, since entry into service (EIS) or since the last replacement of the affected gear 9 rib, whichever occurs last.
If deficiencies are found during inspections, operators must Airbus prior to the airframe's next flight to obtain manufacturer-approved repair instructions. However, carrying out repairs does not eliminate the need for repetitive inspections of the aircraft, unless the repair instructions indicate otherwise.
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