Summary
We propose to adopt a new airworthiness directive (AD) for certain Airbus Model A330-200 and -300 series airplanes; Model A340-200 and -300 series airplanes; and Model A340-541 and -642 airplanes. This proposed AD was prompted by reports of wing tip brakes (WTBs) losing their braking function in service due to heavy wear on the brake discs. WTBs are designed to stop and hold the mechanical transmission of slats and flaps in certain failure cases. This proposed AD would require repetitive operational tests of certain WTB pressure-off-brakes (POBs) for performance on the flap and slat systems, and replacement of any affected WTB with a new or serviceable part if the test fails. This proposed AD would also require eventual replacement of all affected WTBs with a new part, which would terminate the repetitive tests. We are proposing this AD to prevent loss of the WTB braking function, and consequent inability of the flap or slat system to be stopped and held in position during operation, which could result in loss of control of the airplane.