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 787-8 airplanes. The NPRM published in the Federal Register on November 19, 2015 (80 FR 72393), (''the NPRM''). The NPRM was prompted by reports of water leakage from the potable water system due to improperly installed waterline couplings, and water leaking into the EE bays from above the floor in the main cabin, resulting in water on the equipment in the EE bays. The NPRM proposed to require replacing the potable waterline couplings above the forward and aft EE bays with new, improved couplings. The NPRM also proposed to require sealing the main cabin floor areas above the aft EE bay, installing drip shields and foam blocks, and rerouting the wire bundles near the drip shields above the equipment in the aft EE bay. We are issuing this AD to prevent a water leak from an improperly installed potable water system coupling, or main cabin water source, which could cause the equipment in the EE bays to become wet, resulting in an electrical short and potential loss of system functions essential for safe flight. \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 and the FAA's response to each comment. \n\nSupport for the NPRM \n\n\n\tThe Airline Pilots Association International stated that it concurs with the contents of the NPRM. \n\tUnited Airlines (UAL) stated that it supports the compliance time of 60 months to accomplish the actions proposed by the NPRM. \n\nRequests To Revise Compliance Times \n\n\n\tMr. Geoffrey Barrance requested that we revise the compliance times specified in the NPRM to before further flight. Mr. Barrance stated that, in view of the effect of common mode faults to nullify the safety design of critical avionic systems housed in the avionics bay, this matter needsto be treated with the greatest urgency and that the correction of the problem should be required with far greater urgency than the timescales proposed in the NPRM. Mr. Barrance stated an example of the automatic landing function of the automatic flight control system that does not and cannot take into account common mode faults such as water ingress into multiple line replaceable units (LRUs), which are present to provide functional redundancy and fault tolerance. Mr. Barrance stated that no probability can be assessed for unwanted behavior resulting from water ingress into multiple redundant LRUs. \n\tUAL requested that we extend the proposed compliance time from 24 months to 30 months for accomplishing the actions specified in Boeing Alert Service Bulletin B787-81205-SB380009-00, Issue 001, dated March 26, 2015. UAL stated that if maintenance requires an unforeseen disassembly of the airplane for access or to correct a test failure, a 30-month period is required to schedule the clamp inspection and replacement in a heavy check. \n\tWe do not agree to revise the compliance times required by this AD. In developing appropriate compliance times for this AD, we considered not only the safety implications, including evaluation of the hazards associated with water ingress into multiple redundant LRUs, but the manufacturer's recommendations, the availability of required parts, and the practical aspect of accomplishing the required actions within an interval of time that corresponds to typical scheduled maintenance for affected operators. After considering all the available information, we have determined that the compliance times, as proposed, represent appropriate intervals of time in which the required actions can be performed in a timely manner within the affected fleet, while still maintaining an adequate level of safety. Operators are always permitted to accomplish the requirements of an AD at a time earlier than the specified compliance time. Operators wanting additional time to comply with the requirements of an AD may request adjustments to the compliance time under the provisions of paragraph (k) of this AD. We will consider requests for an adjustment of the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety. We have not changed this AD in this regard. \n\nRequest To Use Alternative Moisture Barrier Tape \n\n\n\tUAL requested that we approve the use of flame retardant (FR) moisture barrier tapes Nitto 11611-MB polyurethane tape or BMS8-346 Type II, Class 4 tape (3M 8657) as alternates to the BMS8-346 Type 1, Class 1 moisture barrier tape (Patco D9100) specified in Boeing Alert Service Bulletin B787 81205 SB530029-00, Issue 001, dated March 26, 2015. UAL stated that during a supplemental type certificate test for a Model 737 airplane, burn testing was performed on the Patco D9100 tape by Zodiac Northwest Aerospace Technologies, and it failed the 12-second vertical test. UAL stated that, therefore, the Patco D9100 tape could not be certified to meet the 14 CFR 25.853 flammability requirements. \n\tWe do not agree with UAL's request. We have contacted Boeing who provided evidence that BMS8-346 Type 1, Class 1 moisture barrier tape (Patco D9100) material passed the 12-second vertical burn test. UAL did not submit specific evidence to substantiate that Nitto 11611-MB polyurethane tape or BMS8-346 Type II, Class 4 tape (3M 8657) is compliant and that BMS8-346 Type 1, Class 1 moisture barrier tape (Patco D9100) material is non-compliant. Under the provisions of paragraph (k) of this AD, we will consider requests for approval of an alternative method of compliance (AMOC) if sufficient data are submitted to substantiate that alternative tapes are compliant. We have not changed this AD in this regard. \n\nRequests To Use Revised Service Information \n\n\n\tBoeing and UAL requested that we revise the NPRM to refer to Boeing Alert Service Bulletin B787-81205-SB380009-00, Issue 002, dated December 9, 2015; Boeing Alert Service Bulletin B787-81205-SB530029-00, Issue 002, dated January 26, 2016; and \n\n((Page 44501)) \n\nBoeing Alert Service Bulletin B787-81205-SB530031-00, Issue 002, dated March 16, 2016. \n\tWe agree with the commenters' requests to use the most current service information. We have revised this AD as described below. \n\tBoeing Alert Service Bulletin B787-81205-SB380009-00, Issue 002, dated December 9, 2015, adds notes, revises the waiting time in the leak test, and corrects typographical errors. We have revised paragraphs (c) and (g) of this AD to reference this service information. \n\tBoeing Alert Service Bulletin B787-81205-SB530029-00, Issue 002, dated January 26, 2016, extends the 24-month compliance time for sealing floor panels and seat tracks to 60 months; clarifies installation of components, revises tape requirements; revises sealant callouts; and corrects kit contents. We have revised paragraphs (c) and (h)(1) of this AD toreference this service information. \n\tBoeing Alert Service Bulletin B787-81205-SB530031-00, Issue 002, dated March 16, 2016, extends the 24-month compliance time for installing drip shields and foam blocks to 60 months. This service information also revises the airplane groups into configurations to account for airplanes on which the drip shield between the floor beams at station (STA) 1233 and STA 1257 was not installed due to interference with wire bundles over the P100 panel. This service information also clarifies certain instructions, revises certain task hour estimates, and removes one airplane from the effectivity. This service information erroneously specifies ''Group 6, Configuration 1'' airplanes where it should specify ''Group 7, Configuration 1'' airplanes for Task 29 in multiple places. We have revised paragraphs (c) and (h)(2) of this AD to reference Boeing Alert Service Bulletin B787-81205-SB530031-00, Issue 002, dated March 16, 2016. We have added new paragraph (i) tospecify an exception for Boeing Alert Service Bulletin B787-81205-SB530031-00, Issue 002, dated March 16, 2016. \n\tWe have also added new paragraph (j) of this AD to provide credit for actions done prior to the effective date of this AD using Boeing Alert Service Bulletin B787-81205-SB380009-00, Issue 001, dated March 26, 2015; Boeing Alert Service Bulletin B787-81205-SB530029-00, Issue 001, dated March 26, 2015; and Boeing Alert Service Bulletin B787- 81205-SB530031-00, Issue 001, dated March 26, 2015; as applicable. We have redesignated subsequent paragraphs accordingly. \n\nRequest To Review Airplane Certification Procedures \n\n\n\tMr. Geoffrey Barrance requested that we conduct an internal review and a review with the manufacturer as to why the airplane equipment bay design was not reviewed and required to protect the avionics LRUs from water ingress at the time of certification. Mr. Barrance stated that this is not a new issue and must be a standard check item on design reviews and certification signoff. Mr. Barrance stated that this is a design and certification omission, not primarily a problem with the quality of work by the people doing the installation of the potable waterlines. \n\tWe partially agree with Mr. Barrance's request. We agree that this is a design issue that increased the likelihood of mis-installation, and not primarily a problem with the quality of work by personnel installing the potable waterlines. We asked the manufacturer to conduct a root-cause analysis to determine how it permitted design issues that created the unsafe condition. We are working with the manufacturer to determine if their company processes must be updated to better identify these hazards. The actions required by this AD address only the results of that analysis that directly relate to the identified design issues, and mandate changes to correct those issues. \n\tWe disagree that the EE bay design was not reviewed and required to protect the avionics LRUs from water ingress at the time of certification. A hazard analysis was completed for these systems, as part of the certification process, which required known hazards to be addressed. This event shows that despite the hazard analysis during the design and certification phase, further improvement is needed to remove the unsafe condition. Airplane manufacturers are responsible for the safety of their products and services, and must be in compliance with applicable safety requirements. As a component of our safety management system, we verify that the safety systems of the design approval holder meet applicable requirements. Working with approval holders during the design development process, we strive to avoid unsafe conditions in the first place. The design for this system was evaluated during the certification process and found at the time to be compliant. We also verify that the approval holders' processes, products, and services continue to maintain safety of their product during the operational phases of their service life. In this regard, we have evaluated the issues related to this system and acted on them. \n\tWe are continuously evaluating our certification system and procedures and improving them when problems are found. In addition, if the FAA is made aware of issues occurring on a certificated product, we conduct an investigation, evaluate the manufacturer's root-cause analysis, and make a determination whether or not an unsafe condition exists. We then take appropriate action to mitigate the unsafe condition. We have not changed this AD 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 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 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 AD. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tWe reviewed the following service information. \n\tBoeing Alert Service Bulletin B787-81205-SB380009-00, Issue 002, dated December 9, 2015. \n\tBoeing Alert Service Bulletin B787-81205-SB530029-00, Issue 002, dated January 26, 2016. \n\tBoeing Alert Service Bulletin B787-81205-SB530031-00, Issue 002, dated March 16, 2016. \n\tThis service information describes procedures for replacing the potable waterline couplings above the forward and aft EE bays with new, improved couplings; sealing the floors, seat tracks, and lavatories above the aft EE bay; installing drip shields and foam blocks; and rerouting the wire bundles adjacent to the drip shields above the aft EE bay. This service information is reasonably available because the interested parties have accessto 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 affects 17 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n((Page 44502)) \n\n\n\n\n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tAction Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Replace waterline couplings....... Up to 24 work-hours x $3,195 Up to $5,235 Up to $88,995 \n\t$85 per hour = up to \n\t$2,040 Seal floors and seat tracks....... Up to 108 work-hours x 137 Up to $9,317 Up to $158,389 \n\t$85 per hour = up to \n\t$9,180 Install drip shields and reroute Up to 42 work-hours x34,594 Up to $38,164 Up to $648,788 \n\twiring. $85 per hour = up to \n\t$3,570 ---------------------------------------------------------------------------------------------------------------- \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\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 intrastateaviation 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.