Airworthiness Directives; Airbus Model A300 B2 and B4 Series Airplanes; and Model A300 B4-600, B4-600R, and F4-600R Series Airplanes, and Model C4-605R Variant F Airplanes (Collectively Called A300-600 Series Airplanes)

The FAA is superseding two existing airworthiness directives (AD) that apply to certain Airbus Model A300 B2, A300 B4, and A300-600 series airplanes. One AD currently requires an inspection for cracks of the lower outboard flange of gantry No. 4 in the main landing gear (MLG) bay area, and repair if necessary. The other AD currently requires, among other actions, repetitive inspections of the gantry lower flanges, and repair if necessary. This new AD requires new repetitive inspections for cracks in the lower flange of certain gantries, and repair if necessary, which ends the existing inspection requirements. This new AD also provides for optional terminating actions for the new repetitive inspections. This AD results from a report of a large fatigue crack along the outboard flange of beam No. 4 and a subsequent determination that existing inspections are inadequate. We are issuing this AD to detect and correct fatigue cracks in the lower flanges of gantries 1 through 5 inclusive in the MLG bay area, which could result in reduced structural integrity of the fuselage, and consequent rapid decompression of the airplane.