Airworthiness Directives; Airbus SAS Airplanes

The FAA is adopting a new airworthiness directive (AD) for all Airbus SAS Model A320-251N and -271N airplanes, and Model A321-251N, - 253N, -271N, and -272N airplanes. This AD was prompted by reports that the regulated bleed temperature was measured above the design target with a temperature regulation shift phenomenon, and investigation results show that incorrect temperature regulation can degrade pneumatic system components located downstream of the pre-cooler. This AD requires uploading improved bleed monitoring computer (BMC) software (SW), as specified in a European Union Aviation Safety Agency (EASA) AD, which is incorporated by reference. The FAA is issuing this AD to address the unsafe condition on these products.