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 certain The Boeing Company Model 777-200 and -300 series airplanes equipped with Pratt and Whitney engines. The NPRM published in the Federal Register on August 7, 2014 (79 FR 46201). The NPRM was prompted by reports of blocked drain lines at the engine forward strut that caused flammable fluid to accumulate in a flammable leakage zone. The NPRM proposed to require repetitive functional checks for blockage of the forward strut drain line and doing corrective actions (including cleaning or replacing any blocked drain lines) if necessary, and a one-time cleaning of certain forward strut drain lines. We are issuing this AD to detect and correct blockage of forward strut drain lines, which could cause flammable fluids to collect in the forward strut area and potentially cause an uncontrolled fire or cause failure of engine attachmentstructure and consequent airplane loss. \n\tThis AD requires revisions to certain operator maintenance documents to include new actions (e.g., inspections). Compliance with these actions is required by 14 CFR 91.403(c). For airplanes that have been previously modified, altered, or repaired in the areas addressed by this AD, the operator may not be able to accomplish the actions described in the revisions. In this situation, to comply with 14 CFR 91.403(c), the operator must request approval for an alternative method of compliance according to paragraph (l) of this AD. The request should include a description of changes to the required inspections that will ensure the continued operational safety of the airplane. \n\nRelated Rulemaking \n\n\n\tOn September 23, 2014, we issued AD 2014-20-10, Amendment 39-17983 (79 FR 60331, October 7, 2014), for certain The Boeing Company Model 777-200 and -300 series airplanes. AD 2014-20-10 superseded AD 2013-11- 14, Amendment 39-17474 (78 FR 35749, June14, 2013). AD 2014-20-10 currently requires repetitive general visual inspections of the strut forward dry bay for the presence of hydraulic fluid, and related investigative and corrective actions (including checking drain lines for blockage due to hydraulic fluid coking; cleaning or replacing drain lines to allow drainage) if necessary; and adds airplanes to the applicability. AD 2014-20-10 was prompted by reports of hydraulic fluid contamination (including contamination caused by hydraulic fluid in its liquid, vapor, and/or solid (coked) form) found in the strut forward dry bay. The actions required by 2014-20-10 are intended to detect and correct hydraulic fluid contamination of the strut forward dry bay, which could result in hydrogen embrittlement of the titanium forward engine mount bulkhead fittings, and consequent inability of the fittings to carry engine loads and resulting in engine separation. Hydrogen embrittlement also could cause a through-crack formation across the fittings through which an engine fire could breach into the strut, resulting in an uncontained strut fire. \n\tOn December 22, 2014, we issued AD 2015-01-01, Amendment 39-18062 (80 FR 3158, January 22, 2015) for certain The Boeing Company Model 777-200 and -300 series airplanes. AD 2015-01-01 superseded AD 2011-09- 11, Amendment 39-16673 (76 FR 24354, May 2, 2011). AD 2015-01-01 currently requires repetitive inspections for hydraulic fluid contamination of the interior of the strut disconnect assembly; repetitive inspections for discrepancies of the interior of the strut disconnect assembly, if necessary; repetitive inspections of the exterior of the strut disconnect assembly for cracks, if necessary; and corrective action if necessary. AD 2015-01-01 also provides an optional terminating action for the inspections and adds, for certain airplanes, an inspection of the side and top cover plates to determine if all cover plate attach fasteners have been installed, installing any missing fasteners including doing an inspection for damage, and repair if necessary. \n\tAD 2015-01-01, Amendment 39-18062 (80 FR 3158, January 22, 2015) was prompted by reports of side and top cover plates installed with missing fastener bolts, which could result in an unsealed opening on the system disconnect assembly. The actions required by AD 2015-01-01 are intended to detect and correct hydraulic fluid contamination, which could cause cracking of titanium parts in the system disconnect assembly. The actions of 2015-01-01 are also intended to detect and correct missing fasteners, which could result in unsealed openings on the system disconnect assembly. Both unsafe conditions can compromise the engine firewall and result in fire hazards for both the engine compartment and the strut. \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 NPRM (79 FR 46201, August 7, 2014) and the FAA's response to each comment. \n\nRequest To Add Service Information as Optional Terminating Action \n\n\n\tBoeing and Japan Airlines (JAL) requested that we add Boeing Special Attention Service Bulletin 777-71-0055, dated June 12, 2014, as a terminating action to the NPRM (79 FR \n\n((Page 52950)) \n\n46201, August 7, 2014). Boeing specifically requested that this service information be added in the Supplementary Information--Interim Action section and as a second paragraph to paragraph (i) of the NPRM. Boeing requested that paragraph (i) of the NPRM state that accomplishment of Boeing Special Attention Service Bulletin 777-71-0055, dated June 12, 2014, terminates the requirements of Boeing Special Attention Service Bulletin 777-54-0027, Revision 1, dated September 12, 2013, and is an alternative means of compliance with this AD. \n\tWe agree. Boeing Special Attention Service Bulletin 777-71-0055, dated June 12, 2014, which has since been revised as Revision 1, dated April 15, 2015, describes procedures that address the identified unsafe condition. These procedures include removing the forward strut drain lines; cleaning the left systems disconnect, strut forward lower spar, and forward fireseal pan drain lines; installing new forward strut drain lines and insulation blankets; and doing a functional leak check of the forward strut drain lines, and repair if any leaking is found. \n\tWe have added new paragraph (i) to this AD to provide optional terminating action and redesignated subsequent paragraphs accordingly. Paragraph (i) of this AD states that accomplishment of Boeing Special Attention Service Bulletin 777-71-0055, Revision 1, dated April 15, 2015, along with a revision of the maintenance or inspection program, as applicable, to incorporate a certain airworthiness limitation, terminates the requirements of paragraph (g)(1) of this AD at the modified area only. \n\tWe have also added new paragraph (j) of this AD to specify that no alternative actions or intervals may be used after incorporating the airworthiness limitation unless the actions or intervals are approved as an alternative method of compliance (AMOC) in accordance with the procedures specified in paragraph (l) of this AD. We redesignated subsequent paragraphs accordingly. \n\tWe have also added new paragraph (k) to this AD to give credit for actions required by paragraph (i) of this AD, if those actions were performed before the effective date of this AD using Boeing Special Attention Service Bulletin 777-71-0055, dated June 12, 2014. We redesignated subsequent paragraphs accordingly. \n\tIn addition, we updated the ''Interim Action'' paragraph in the SUPPLEMENTARY INFORMATION section of the preamble of this final rule accordingly. \n\nRequest To Remove Requirement To Clean Forward Strut Drain Line \n\n\n\tAll Nippon Airways (ANA) requested that we revise the NPRM (79 FR 46201, August 7, 2014) to remove the phrase ''clean the forward strut drain line'' from paragraph (g)(1) of the NPRM. ANA stated that cleaning the forward strut drain line is not required if part 1, condition 1, in paragraph 3.B ''Work Instructions,'' of Boeing Special Attention Service Bulletin 777-54-0027, Revision 1, dated September 12, 2013, is met. \n\tWe agree because condition 1 is met when 354 or more ounces of water are collected within 2 minutes after the start of pouring water for the functional check of the forward strut drain line. Cleaning the blocked drain line is part of the corrective actions in condition 2 as specified in Boeing Special Attention Service Bulletin 777-54-0027, Revision 1, dated September 12, 2013. This change does not compromise safety or the intent of the AD, therefore, we have removed the phrase ''clean the forward strut drain line,'' from paragraph (g)(1) of this final rule. \n\nRequest To Allow Alternate Tee Fitting Part Numbers \n\n\n\tANA requested the NPRM (79 FR 46201, August 7, 2014) include three part numbers of the tee fitting. ANA indicated that paragraph 2.C., of Boeing Special Attention Service Bulletin 777-54-0027, Revision 1, dated September 12, 2013, states BACT16BR120612J tee fitting is required if replacement is necessary. ANA stated tee fittings having part numbers BACT16BR120612J, BACT16BR120612JN, and AS4139J120612 may be used according to a Boeing product standard parts list. \n\tWe agree because the tee fitting part number BACT16BR120612J listed in Boeing Special Attention Service Bulletin 777-54-0027, Revision 1, dated September 12, 2013, is obsolete. We have added text to paragraph (g)(1) of this AD to allow alternate tee fitting part numbers BACT16BR120612JN and AS4139J120612, as long as the installation of the forward strut drain lines is accomplished in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 777-54-0027, Revision 1, dated September 12, 2013. \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 AD with the changes described previously and minor editorial changes. We have determined that these minor changes: \n\t(Agr)re consistent with the intent that was proposed in the NPRM (79 FR 46201, August 7, 2014) for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM (79 FR 46201, August 7, 2014). \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD. \n\nInterim Action \n\n\n\tWe consider this AD interim action. The manufacturer has issued Boeing Special Attention Service Bulletin 777-71-0055, Revision 1, dated April 15, 2015, which describes a modification that addresses the unsafe condition identified in this AD. This service information is an optional action in this AD. If final action is later identified, we might consider further rulemaking. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tWe reviewed the following Boeing service information. \n\tBoeing Special Attention Service Bulletin 777-54-0027, Revision 1, dated September 12, 2013. The service information describes procedures for doing a functional check for blockage of the forward strut drain lines and corrective actions. \n\tBoeing Special Attention Service Bulletin 777-71-0055, Revision 1, dated April 15, 2015. This service information describes procedures for replacing the forward strut drain lines and adding insulation blankets. \n\tAirworthiness Limitation 54-AWL-01, ''Forward Strut Drain Line,'' Section D.4, Pratt and Whitney Forward Strut Drain Line, of the Boeing 777 Maintenance Planning Data (MPD) Document Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision October 2014. This service information describes an airworthiness limitation task for the functional check of the forward strut drain line. \n\tThis service information is reasonably available because the interestedparties have access to it through their normal course of business or by the means identified in the ADDRESSES section of this AD. \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 54 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n((Page 52951)) \n\n\n\n\n\n\n\tEstimated Costs: Required Actions ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Repetitive functional checks of 2 9 work-hours x $85 $0 $765 per inspection $41,310 per \n\tstruts per inspection cycle. per hour = $765 cycle. inspection cycle. \n\tper inspection \n\tcycle. One-time cleaning................ 13 work-hours x $850 1,105.............. 59,670. \n\tper hour = $1,105. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tWe estimate the following costs to do any necessary repairs or 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\tAction Labor cost Parts cost Cost per product ---------------------------------------------------------------------------------------------------------------- Repair drain tube assemblies in up to Up to 5 work-hours x $85 per $0 Up to $425. \n\t2 struts. hour = $425. Replace drain tube assemblies in up to Up to 5 work-hours x $85 per Up to $4,484Up to $4,909. \n\t2 struts. hour = $425. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tAccording to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all costs in our cost estimate. \n\n\n\tEstimated Costs: Optional Actions ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor Cost Parts Cost product ---------------------------------------------------------------------------------------------------------------- Removal of drain tube assemblies........... 1 work(dash)hour x $85 per hour = $0 $85 \n\t$85. Cleaning of drain lines.................... 6 work-hours x $85 per hour = $510. $0 $510 Installation of new drain lines and 2 work-hours x $85 per hour = $170. $17,250 $17,420 \n\tinsulation blankets. Leak check of drain lines.................. 1 work-hour x $85 per hour = $85... $0 $85 Revision of maintenance or inspection 1 work-hour x $85 per hour = $85... $0 $85 \n\tprogram. ---------------------------------------------------------------------------------------------------------------- \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.