Discussion \n\n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to the specified products. That NPRM was published in the Federal Register on September 1, 2011 (76 FR 54405). That NPRM proposed to require repetitive general visual inspections for broken or missing latch pins of the lower sills of the forward and aft lower lobe cargo doors; repetitive detailed inspections for cracking of the latch pins; and corrective actions if necessary. \n\n((Page 21427)) \n\nComments \n\n\n\tWe gave the public the opportunity to participate in developing this AD. The following presents the comments received on the proposal and the FAA's response to each comment. \n\nRequest to Withdraw the NPRM (76 FR 54405, September 1, 2011) \n\n\n\tUnited Parcel Service (UPS) asked that we withdraw the NPRM (76 FR 54405, September 1, 2011). UPS stated that there is a lack of justification for issuing the NPRM and added thatit is being issued based on a report of a fatigue crack in the 17-4PH material latch pins of the lower cargo door, and the assumption that adjacent latch pins could also be affected. UPS noted that the latching structures of the lower forward and aft cargo door each include eight latch pins; those latch pins are part of a fail-safe design, which should preclude critical failure with the failure of one element. UPS added that the Model 747-400 maintenance planning document includes a detailed inspection of the latch mechanism of the lower cargo door, which includes the latch pins, at 2 year or 2,000 flight cycle intervals, whichever occurs first. UPS noted that the NPRM would require repetitive inspections at 1,600-flight-cycle intervals--a modest increase in frequency over the existing maintenance program--which has already been proven successful at detecting damage to adjacent latch pins. UPS concluded that, based on the extensive fleet history of the latch pins of these lower cargo doors, with no reports of adjacent pin failures, the existing maintenance program inspections of the latch pins are adequate. \n\tWe do not agree with the commenter's request to withdraw the NPRM (76 FR 54405, September 1, 2011). Although the commenter has not experienced pin failure in service, the manufacturer has found pin fatigue failure on another airplane of the same type design. Therefore, we find we must issue this AD to address the identified unsafe condition on the entire fleet. \n\tThe inspections identified in the maintenance planning document are general visual inspections of the entire door. The inspections required by this final rule include detailed inspections of the latch pins themselves. These detailed inspections are the result of the pin fracturing in service. The fractured pin was the number eight latch pin on the lower sill of the aft lower lobe cargo door; investigation by the manufacturer revealed that the crack initiated due to fatigue, and propagated by a combination of fatigue and stress corrosion. If the latch pins on the lower sill are not regularly inspected, and broken latch pins are not replaced, the forward and/or aft cargo door could open during service, resulting in loss of the cargo door, rapid decompression, and significant damage to the airplane. No change to the AD is necessary in this regard. \n\nRequest To Clarify Language in Relevant Service Information Section \n\n\n\tBoeing asked that the description specified in the ''Relevant Service Information'' section of the NPRM (76 FR 54405, September 1, 2011) be changed as follows: ''The service bulletin describes procedures for repetitive detail inspections of latch pins for broken or missing latch pins of the lower sills of the forward and aft lower lobe cargo doors; repetitive detailed inspections of the replaced latch pins for cracked, broken or missing latch pins; and corrective actions if necessary.'' Boeing stated that Boeing Alert Service Bulletin 747- 53A2835, dated October28, 2010, necessitates that a detailed inspection be done on all pins (including previously replaced pins). Boeing added that the detailed inspection is for cracks, and the general visual inspection is to look for the broken and missing pins. Boeing notes that paragraph (g) of the NPRM provides the correct description of the inspections specified in the service bulletin. \n\tWe acknowledge the commenter's concern and agree that the language could be clarified somewhat; however, since that section of the preamble does not reappear in the final rule, no change to this AD is necessary in this regard. \n\nRequest To Include Revision 1 of the Referenced Service Bulletin \n\n\n\tBoeing also asked that Boeing Alert Service Bulletin 747-53A2835, Revision 1, dated December 8, 2011, be included in the NPRM (76 FR 54405, September 1, 2011) for accomplishing certain actions. Boeing Alert Service Bulletin 747-53A2835, dated October 28, 2010, was referred to as the appropriate source of service information for accomplishing the actions specified in the NPRM. Boeing added that Boeing Alert Service Bulletin 747-53A2835, Revision 1, dated December 8, 2011, is scheduled for FAA-approval, and includes a latch pin modification and post-modification inspection to address the safety issue. \n\tWe have reviewed Boeing Alert Service Bulletin 747-53A2835, Revision 1, dated December 8, 2011, and agree to include it in this final rule as an additional source of service information. Boeing Alert Service Bulletin 747-53A2835, Revision 1, dated December 8, 2011, reduces an existing compliance time, adds a latch pin modification, and repetitive post-modification inspections. We are including the actions in Boeing Alert Service Bulletin 747-53A2835, Revision 1, dated December 8, 2011, as optional in order to avoid delaying issuance of the AD. We have revised paragraph (g) of this AD accordingly. We are currently considering additional rulemaking to require the modification and post-modification inspections. \n\nConclusion \n\n\n\tWe reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously--and minor editorial changes. We have determined that these minor changes: \n\tAre consistent with the intent that was proposed in the NPRM (76 FR 54405, September 1, 2011) for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM (76 FR 54405, September 1, 2011). \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of the AD. \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 228 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n\n\tEstimated Costs -------------------------------------------------------------------------------------------------------------------------------------------------------- \n\tAction Labor cost Parts cost Cost per product Cost on U.S. operators -------------------------------------------------------------------------------------------------------------------------------------------------------- Inspection........................... 3 work-hours x $85 per $0 $255 per inspection $58,140 per inspection cycle. \n\thour = $255 per cycle. \n\tinspection cycle. -------------------------------------------------------------------------------------------------------------------------------------------------------- \n\n\n\n((Page 21428)) \n\n\n\tWe estimate the following costs to do any necessary replacements/ modifications that would be required based on the results of the required inspection. We have no way of determining the number of aircraft that might need these actions: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replacement of latch pins..................... 8 work-hours x $85 per hour = $680.... $0 $680 Modification of latch fittings................ 36 hours x $85 per work-hours = $3,060 0 3,060 ---------------------------------------------------------------------------------------------------------------- \n\nAuthority for this Rulemaking \n\n\n\tTitle 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority. \n\tWe are issuing this rulemaking under the authority described in Subtitle VII,Part A, Subpart III, Section 44701: ''General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action. \n\nRegulatory Findings \n\n\n\tThis AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. \n\tFor the reasons discussed above, I certify that this AD: \n\t(1) Is not a ''significant regulatory action'' under Executive Order 12866, \n\t(2) Is not a ''significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), \n\t(3) Will not affect intrastate aviation in Alaska, and \n\t(4) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.