Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Airbus Model A330 airplanes and A340-200 and -300 series airplanes. For certain airplanes, this proposed AD would require inspecting to determine the part number of certain S4- and MZ-type spoiler servo-controls (SSCs). For certain other airplanes, this proposed AD would require inspecting to determine the part number of all SSCs. This proposed AD would also require replacing any affected SSC with a new SSC. This proposed AD results from a new load duty cycle defined by the manufacturer. Additional fatigue tests and calculations done on this basis indicated that the spoiler valve manifold of the S4- type SSCs, and, on certain airplanes, the maintenance cover of the MZ- type SSCs, may crack during its service life due to pressure impulse fatigue. We are proposing this AD to prevent fatigue cracking of certain SSCs, which could result in hydraulic leakage and consequent loss of SSC function and loss of theassociated hydraulic system. These conditions could affect all three hydraulic systems, which could result in reduced controllability of the airplane.