Discussion \n\n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all The Boeing Company Model 757-200, -200PF, and -200CB series airplanes. The NPRM published in the Federal Register on October 4, 2016 (81 FR 68371) (''the NPRM''). The NPRM was prompted by an analysis of the cam support assemblies of the MCD that indicated that the existing maintenance program for the cam support assemblies is not adequate to reliably detect cracks before two adjacent cam support assemblies could fail. The NPRM proposed to require an inspection to determine part numbers, repetitive inspections to detect cracking of affected cam support assemblies of the MCD, and replacement if necessary. We are issuing this AD to detect and correct cracking of the cam support assemblies of the MCD, which could result in reduced structural integrity of the MCD and consequent rapid decompression of the airplane. \n\nCommentsWe gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nRequests To Revise Applicability \n\n\n\tBoeing, Delta Air Lines (DAL), European Air Transport Leipzig GmbH (EAT), DHL Express (DHL), FedEx Express (FedEx), and United Airlines (UAL) requested that we revise the proposed AD applicability. DAL and UAL requested that airplanes that do not have a MCD be excluded from the AD applicability. \n\tThree of these commenters requested that the actions of the service information be applicable only to \n\n((Page 44302)) \n\nairplanes in the service information effectivity. These commenters explained that the service information effectivity includes only airplanes that have a MCD installed by Boeing, either as a Boeing factory-delivered freighter or as a Boeing Supplemental Type Certificate (STC)-converted freighter, and not airplanes that have been converted to a freighter by a non-Boeing STC. \n\tEAT and DHL requested that we revise the applicability of the proposed AD to exclude Model 757 airplanes with passenger to freighter modification STC ST01529SE by Precision Conversions. \n\tFedEx requested that we either withdraw the NPRM and issue a new one, to include a separate section for airplanes modified under VT Mobile Aerospace Engineering STC ST03562AT, or exempt the airplanes modified by that STC from the NPRM and issue a new NPRM for airplanes modified by that STC. FedEx also requested that we revise the NPRM to mandate, for Model 757-200 airplanes modified in accordance with STC ST03562AT, VT Mobile Aerospace Engineering Service Bulletin MAE757SF- SB-52-l 601, Revision 0, dated April 15, 2016, or a subsequent revision, instead of Boeing Alert Service Bulletin 757-52A0094, dated December 23, 2015. FedEx explained that the MCD that is installed by the Precision Conversion STC is different than that installed by Boeing or VT Mobile Aerospace Engineering and does not have the affected cam support fittings installed. FedEx stated that it prefers the VT Mobile Aerospace Engineering service information for modifying airplanes instead of the Boeing service information, since Boeing does not provide support for the VT Mobile Aerospace STC, and any discrepancies or questions on the Boeing service information would be addressed by Boeing based on goodwill, rather than by contractual agreement. \n\tWe partially agree with the commenters' requests. We agree that the unsafe condition does not apply to Model 757-200 airplanes that do not have a MCD and to airplanes modified from passenger to freighter in accordance with Precision Conversions STC ST01529SE. The unsafe condition applies only to MCD cam support assemblies with the specified part numbers. \n\tWe disagree that the AD should apply only to Boeing converted freighters. We also disagree that a separate AD should be issued to address Model 757-200 freighters modified by STC ST03562ATor any of the other passenger-to-freighter modification STCs because these support assemblies having affected part numbers could be installed during original aircraft manufacture, or during passenger-to-freighter modification. The unsafe condition applies only to airplanes with certain part number cam support assemblies installed, and it does not apply to Model 757-200 airplanes that do not have a MCD. \n\tParagraphs (g) and (h) of this AD list the part numbers of the cam support assemblies that have the unsafe condition. We have confirmed that the cam support assemblies having affected part numbers are not installed on Model 757 airplanes as part of the Precision Conversions STC ST01529SE passenger-to-freighter conversion. We have revised the SUMMARY section, Discussion section, and paragraph (c) of this AD to state that the AD applies to all Model 757-200, -200PF, and -200CB series airplanes equipped with a MCD, except those airplanes that have been converted from a passenger to freighter configuration in accordance with STC ST01529SE. \n\tWe expect that the actions specified in Boeing Alert Service Bulletin 757-52A0094, Revision 2, dated May 2, 2017 (''ASB 757-52A0094, R2''), can be accomplished on airplanes that are not identified in that service information. In addition, we do not consider it appropriate to include various provisions in an AD applicable only to an operator's unique configuration of affected airplanes. However, if an operator with a Model 757-200 freighter cannot accomplish the required actions specified in the service information, or prefers to use different service information that is specific to their design (such as FedEx's request to use VT Mobile Aerospace Engineering Service Bulletin MAE757SF-SB-52-l 601, Revision 0, dated April 15, 2016), an alternative method of compliance (AMOC) can be requested in accordance with paragraph (j) of this AD. \n\nRequests To Revise the Compliance Time \n\n\n\tBoeing and FedEx requested that we revise the compliance time in paragraph (g)(l) of the proposed AD from ''18,000 total flight cycles'' to ''18,000 door flight cycles.'' The commenters explained that some of the affected airplanes have been converted from passenger to freighter airplanes, and for these converted airplanes, the cam support assemblies were installed at the time of the aircraft conversion, not when the airplanes were produced. The commenters stated that, for these converted airplanes, the initial compliance time for inspection should be based on the number of flight cycles since the part has been installed. In addition, Boeing stated that ASB 757-52A0094, R2, was revised to change the inspection threshold for Boeing converted freighter airplanes to total flight cycles after freighter conversion redelivery. \n\tWe agree with the commenters' request. For airplanes that have been converted to freighters, the compliance time for the initial inspection should be based on the number of cycles the cam support assembly has beenin service. We have revised paragraph (g)(1) of this AD accordingly. \n\nRequest To Withdraw the NPRM and Reference Revised Service Information \n\n\n\tFedEx requested that we withdraw the NPRM and issue a new NPRM to require compliance with ASB 757-52A0094, R2, instead of Boeing Alert Service Bulletin 757-52A0094, dated December 23, 2015. \n\tWe partially agree with the commenter's request. We agree with the commenter's request to reference ASB 757-52A0094, R2, as the appropriate source of service information. Revision 1 of Boeing Alert Service Bulletin 757-52A0094, dated April 21, 2016 (''ASB 757-52A0094, R1''), removed one airplane from the effectivity and updated some references and publications affected. ASB 757-52A0094, R2, removed non- Boeing-STC-converted freighter airplanes from the effectivity and changed the initial compliance time for the converted freighter airplanes to flight cycles after freighter conversion redelivery. \n\tWe disagree with withdrawing the NPRM and reissuing a new NPRM requiring compliance with ASB 757-52A0094, R2, because doing so would unnecessarily delay issuance of the final rule. Additionally, the compliance time can be corrected in the final rule without the need for a supplemental NPRM since the corrected compliance time will provide additional time for the converted freighter airplanes and will not reduce the initial compliance time for any airplane. We have revised this AD to refer to ASB 757-52A0094, R2, as the appropriate source of service information. We have also added paragraph (i) to this AD to provide credit for actions required by paragraph (h) of this AD, if those actions were performed before the effective date of this AD using Boeing Alert Service Bulletin 757-52A0094, dated December 23, 2015; or ASB 757-52A0094, R1. We have redesignated subsequent paragraphs accordingly. \n\nRequest To Correct Manual Reference in the Service Information \n\n\n\tUnited Parcel Service (UPS) requested that we revise paragraph (h) of the((Page 44303)) \n\nproposed AD to specify use of Airplane Maintenance Manual (AMM) 52-32- 11 in lieu of Component Maintenance Manual (CMM) 52-32-03 for the cam and bell-crank assembly installation. UPS explained that Boeing Alert Service Bulletin 757-52A0094, dated December 23, 2015, included an incorrect manual reference. \n\tWe partially agree with the commenter's request. We agree that the manual reference is incorrect in Boeing Alert Service Bulletin 757- 52A0094, dated December 23, 2015. The incorrect reference was changed in ASB 757-52A0094, R2, and, as explained previously, ASB 757-52A0094, R2, is referenced as the appropriate source of service information in this AD. No further change is necessary in this regard. \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 this final rule with the changes described previously and minor editorial changes. We have determined thatthese minor changes: \n\tAre consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM. \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tWe reviewed Boeing Alert Service Bulletin 757-52A0094, Revision 2, dated May 2, 2017. This service information describes procedures for an ultrasonic inspection of the cam support assemblies of the main cargo door, and replacement of the cam support assemblies. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section. \n\nCosts of Compliance \n\n\n\tWe estimate that this AD will affect 212 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.............. 6 work-hours x $85 $0 $510 per inspection cycle.................. $108,120 per inspection cycle. \n\tper hour = $510 per \n\tinspection cycle. -------------------------------------------------------------------------------------------------------------------------------------------------------- \n\n\n\tWe estimate the following costs to do any necessary replacements that would be required based on the results of the inspection. We have no way of determining the number of aircraft that might need these replacements: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replacement (per pair of cam support 60 work-hours x $85 per hour = $15,298 $20,398 \n\tassemblies). $5,100. ---------------------------------------------------------------------------------------------------------------- \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\tThis AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes to the Director of theSystem Oversight Division. \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.