Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Airbus Model A300 B2 and B4 series airplanes; Model A300 B4-600, A300 B4-600R, C4-605R Variant F, and A300 F4-600R (collectively called A300-600) series airplanes; and Model A310 series airplanes. The existing AD currently requires replacement of the transformer rectifier units (TRUs) in the avionics compartment with new, improved TRUs. This proposed AD would require replacement of the TRUs installed according to the existing AD with different TRUs that are improved. This proposed AD is prompted by analysis that has revealed that certain diodes installed in the TRUs are the main factor contributing to the continuing TRU failures. We are proposing this AD to prevent failure of the TRUs. Failure of multiple TRUs could result in loss of the thrust reversers, autothrottle, flaps, and various systems (wing/cockpit window anti-ice, trim tank pumps, and windshield wipers) on the airplane; or display of incorrect information to the flightcrew.