Airworthiness Directives; Airbus Airplanes

We propose to supersede Airworthiness Directive (AD) 2013-13- 04, for certain Airbus Model A318, A319, A320, and A321 series airplanes. AD 2013-13-04 currently requires installing a power interruption protection circuit for the landing gear control interface unit (LGCIU). Since we issued AD 2013-13-04, we have determined that additional work is necessary to adequately address the identified unsafe condition. This proposed AD would require a new modification of any previously modified LGCIU. This proposed AD would also require revising the maintenance or inspection program to reduce a certain functional check interval. This proposed AD also adds airplanes to the applicability. We are proposing this AD to prevent untimely unlocking and/or retraction of the nose landing gear (NLG), which, while on the ground, could result in injury to ground personnel and damage to the airplane.