Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Airbus Model A330 and A340 series airplanes. This proposed AD would require repetitive borescope inspections of the left and right fuel tanks of the trimmable horizontal stabilizers (trim tanks) for detached or damaged float valves; related investigative/corrective actions if necessary; and the eventual replacement of all float valves in the left and right trim tanks with new, improved float valves, which terminates the need for the repetitive inspections. This proposed AD would also require repetitive replacement of certain new, improved float valves. This proposed AD is prompted by reports of detached and damaged float valves in the trim tanks. We are proposing this AD to prevent, in the event of a lightning strike to the horizontal stabilizer, sparking of metal parts and debris from detached and damaged float valves, or a buildup of static electricity, which could result in ignition of fuel vapors andconsequent fire or explosion.