United Airlines

Subject: NPRM Docket# FAA-2013-0088, Directorate# 2011-NM-233-AD Sir or Madam, The above referenced NPRM mandates replacement of the A319/A320 Brake System Control Unit BSCU with the upgraded enhanced manufacturing and maintainability (EMM) BSCU. United Airlines is currently in the process of upgrading our BSCU to the enhanced EMM version (compliant with the NPRM) and is 81% complete. UAL does concur with the FAA assertion that termination action should consist of BSCU standard L4.9B, std. 10 or std. 10.1, rather than standard L4.1, or L4.5. The proposed rule mandates accomplishment of the BSCU replacement within 6 months of the effective date. UAL is concerned that the vendor may not be able to support this relatively short deadline with sufficient numbers of enhanced BSCU’s. A more feasible solution with an acceptable level of safety would be: 1. Continue repetitive inspections of the upper support of the Nose Landing Gear (NLG) until replacement with the EMM BSCU. 2. Aircraft previously accomplished with termination action per AD 2007-18-09 (standard L4.1, L4.5, or L5-2) would also require continued inspections of the NLG. 3. Upgrade to the standard L4.9B, std. 10 or std. 10.1 could then be accomplished on attrition, as units are available from the BSCU manufacturer. Sincerely, Steve Lydon Senior Project Engineer Aircraft Systems United Airlines 872-825-9307