Summary
We are revising an earlier proposed airworthiness directive (AD) for all Airbus Model A318, A319, A320, and A321 series airplanes. The NPRM proposed to supersede Airworthiness Directives (AD) 2011-13-11 and AD 2013-16-09. AD 2011-13-11 currently requires an amendment of the airplane flight manual (AFM), repetitive checks of specific centralized fault display system (CFDS) messages, an inspection of the opening sequence of the main landing gear (MLG) door actuator for discrepancies if certain messages are found, and corrective actions if necessary. AD 2013-16-09 currently requires an inspection to determine airplane configuration and part numbers of the landing gear control interface unit and MLG door actuators; and, for affected airplanes, repetitive inspections of the opening sequence of the MLG door actuator, and replacement of the MLG door actuator if necessary; and provides optional terminating action for the repetitive inspections. The NPRM was prompted by a determinationthat the interval of the MLG door opening sequence inspection must be reduced. The NPRM proposed to reduce the interval of the MLG door opening sequence inspection, and also to replace or modify certain MLG door actuators. This action revises the NPRM by adding a flushing procedure to be performed when installing a new MLG door actuator. We are proposing this supplemental NPRM (SNPRM) to detect and correct deterioration of the damping ring and associated retaining ring of the MLG door actuator, which can sufficiently increase the friction inside the actuator to restrict opening of the MLG door by gravity, during operation of the landing gear alternate (free-fall) extension system. This condition could prevent the full extension and/or down-locking of the MLG, possibly resulting in MLG collapse during landing and consequent damage to the airplane and injury to occupants. Since these actions impose an additional burden over those proposed in the NPRM, we are reopening the comment periodto allow the public the chance to comment on these proposed changes.