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 published in the Federal Register on November 18, 2011 (76 FR 71472). That NPRM proposed to require inspecting to detect damage to the upper fire seals on the forward edge of the thrust reverser, where the fire seal contacts the 12-o'clock engine strut, and for correct stiffness and vent holes, and doing corrective actions if necessary; and installing a bracket for the fire seal. \n\nRevised Service Information \n\n\n\tSince we published the NPRM (76 FR 71472, November 18, 2011), Boeing has issued Special Attention Service Bulletin 737-78-1086, Revision 1, dated May 15, 2012. That revision removes one airplane from the effectivity, updates and corrects certain illustrations and procedures, and states that no more work is necessary on airplanes changed in accordance with the original issue (BoeingSpecial Attention Service Bulletin 737-78-1086, dated October 6, 2010), which was specified as the appropriate source of service information in the NPRM. \n\tWe have accordingly changed paragraphs (g), (g)(1), and (g)(2) of this final rule to specify Boeing Special Attention Service Bulletin 737-78-1086, Revision 1, dated May 15, 2012; added paragraph (i) of this AD to give credit for actions done before the effective date of this AD using Boeing Special Attention Service Bulletin 737-78-1086, dated October 6, 2010; and reidentified subsequent paragraphs. \n\tHowever, the revised service bulletin, Boeing Special Attention Service Bulletin 737-78-1086, Revision 1, dated May 15, 2012, contains two errors, as follows: \n\tFigure 10, Sheet 3 of 3: Note row (a) of the table shown in Figure 10, incorrectly refers the reader to ''(a)'' instead of Note row (b). \n\tFigures 6, 7, 15, and 16, all Sheet 2 of 3, all View B: These illustrations show the top fastener to be removed in the center of threefasteners in order to remove the retainer. However, these three fasteners are adjustable sustained preload (ASP) fasteners that do not require removal for this action. View B also incorrectly shows the location of the top rivet hole, which is actually below the row of ASP fasteners. These errors in those figures affect the actions specified in paragraph (g)(2) of this AD. The other instructions in the figures are correct. \n\tTo clarify the correct actions for paragraph (g)(2) of this AD, we have added paragraph (h) to this AD to describe these differences, and Figures 1 through 4 of this AD to show the correct fastener and rivet hole information. \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 (76 FR 71472, November 18, 2011) and the FAA's response to each comment. \n\nRequest To Change the Unsafe Condition Statement \n\n\n\tBoeing requested that we rephrase the unsafe condition described in the Summary and paragraph (e) of the NPRM (76 FR 71472, November 18, 2011). The commenter stated that damage to the fire seals or low stiffness \n\n((Page 26234)) \n\nis the unsafe condition because either condition could allow increased airflow into the engine core compartment, which could reduce fire extinguishing concentrations. Boeing further stated that it has received no reports of damage to adjacent structure due to fire seal damage, but has received reports of damage to insulation blankets adjacent to the fire seal damage; it received no reports of damage with sealed blankets. \n\tWe agree to revise the unsafe condition statements for the reasons given, and have changed the Summary and paragraph (e) of this AD accordingly. \n\nRequest for Terminating Action Statement \n\n\n\tAmerican Airlines (AAL) requested that the NPRM (76 FR 71472, November 18, 2011) include a statement indicating that performing the required actions terminates the AD's requirements. AAL stated that fire seal inspections have regular maintenance requirements scheduled under Maintenance Review Board (MRB) items 78-090 and -100, which adequately monitor ongoing serviceability. \n\tWe agree with AAL's request for the reason given. We have added the words ''one-time,'' which accurately describes the general visual inspection required by paragraph (g) of this AD. Because paragraphs (g)(1) and (g)(2) refer to the paragraph (g) inspection, those paragraphs need no change. \n\nRequest To Extend the Compliance Time \n\n\n\tAAL requested that the compliance time in paragraph (g) of the NPRM (76 FR 71472, November 18, 2011) be extended to 72 months from the date of the NPRM (76 FR 71472, November 18, 2011), rather than 36 months. AAL stated that the longer compliance time would eliminate an undue burden on operators by better coinciding with their heavy checks, and that the added time needed to replace or reseal the upper support flange on-wing affects their tighter C-check schedules. Further, the MRB seal inspections maintain an acceptable safety level. \n\tWe do not agree to extend the compliance time. The proposed compliance time of 36 months after the AD effective date, will be well after the manufacturer's recommended action time of 36 months after the original issue date of Boeing Special Attention Service Bulletin 737- 78-1086, dated October 6, 2010. \n\tIn developing an appropriate compliance time for this action, we considered the urgency associated with the subject unsafe condition, the availability of required parts, and the practical aspect of accomplishing the required inspection within a period of time that corresponds to the normal scheduled maintenance for most affected operators. However, under the provisions of paragraph (j) of this final rule, we will consider requests for approval of an extension of the compliance time if sufficient data are submitted to substantiate that the new compliance time would provide an acceptable level of safety. We have not changed the AD in this regard. \n\nRequest To Change Cost Information \n\n\n\tAAL requested that we increase the labor time in the ''Costs of Compliance'' section of the NPRM (76 FR 71472, November 18, 2011) to reflect the additional two work shifts needed for installation and cure time, plus the material cost of the new flange insulation. AAL stated that it prototyped the actions specified in Boeing Special Attention Service Bulletin 737-78-1086, dated October 6, 2010, and found that it added significant time to the light C-check, mostly due to a minimum of five work shifts to install and cure the flange insulation, during which time no rigging or operating of flight controls could be done. \n\tWe agree to revise the cost information as follows, based on the new service information discussed in the ''New Service Information'' section above: ''Labor cost'' increased to 28 work-hours (14 hours per engine), and ''Parts cost'' to $2,494 ($1,247 per engine). The ''on- condition costs'' remainunchanged. \n\nRequest To Include Later FAA-Approved Service Bulletin Revisions \n\n\n\tAAL requested that we allow compliance by any later FAA-approved revisions to Boeing Special Attention Service Bulletin 737-78-1086, Revision 1, dated May 15, 2012. \n\tWe disagree to refer to later revisions to service information, because when referring to a specific service bulletin in an AD, we cannot use the phrase, ''or later FAA-approved revisions,'' due to Office of the Federal Register regulations for approving materials that are incorporated by reference. However, operators may request approval to use a later revision of the referenced service bulletin as an alternative method of compliance, under the provisions of paragraph (j) of the final rule. We have not changed the AD in this regard. \n\nRequest To Exclude Certain Parts of the Service Information \n\n\n\tAAL stated that Boeing Special Attention Service Bulletin 737-78- 1086, dated October 6, 2010, specifies actions that duplicate procedures given in the aircraft maintenance manual (AMM), or apply only to on-wing methods or not removing the thrust reverser, and requested that the NPRM (76 FR 71472, November 18, 2011) not mandate these actions for all airplanes and methods when they do not apply, or do not address the unsafe condition for that airplane. In one example, AAL described that if the thrust reverser is not removed, only the fire-seal compression check of AMM 78-31-12-4 or 87-31-01-5 (fire seal removal/installation, and thrust reverser adjustment/test, respectively) needs to be done, because the vee-blade depth and deflection limiter geometry do not change. \n\tWe do not agree to exclude certain actions specified in the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-78-1086, Revision 1, dated May 15, 2012, from the requirements of this AD. Those instructions do not address accomplishing the work off-wing, other than stating that it can be done. The thrust reverser adjustment is included in the steps regardless of how the seal flange is installed, because adding the additional material in the stack-up might affect part fit-up and ultimately require re-rigging prior to releasing the airplane into service. Further, the service bulletin only refers to the AMM procedures, which gives operators flexibility in doing the work due to particular maintenance procedures not being mandated. We have not changed the AD in this regard. \n\nRequest To Correct Errors in, or Refer to, Revised Service Information \n\n\n\tAAL and Boeing submitted examples of errors in and corrections needed to Boeing Special Attention Service Bulletin 737-78-1086, dated October 6, 2010. AAL requested that the service information be corrected or revised, and Boeing requested that we incorporate Boeing Special Attention Service Bulletin 737-78-1086, Revision 1, dated May 15, 2012, which Boeing stated corrects the items it identified. \n\tAs discussed in the Revised Service Information section above, weagree to refer to the revised service information, including the two differences noted in that section. \n\nConcern for Parts Availability \n\n\n\tAAL stated that there needs to be sufficient stock of seals available to \n\n((Page 26235)) \n\nsupport replacements resulting from inspections done within the proposed compliance time. AAL found that in December 2011, the Boeing parts page on the Internet showed no available stock of the required seals and did not show a standard lead time for them, but projected dates in February and March of 2012. \n\tWe infer that AAL requested that we delay issuing the AD until parts are available. We received information from Boeing that ample parts kits are now available to supply the fleet. We have not changed the AD in this regard. \n\nAdded Paragraph for Certain Alternative Methods of Compliance (AMOCs) \n\n\n\tWe added new paragraph (j)(3) to this AD to allow AMOC requests approved by Boeing's Organization Designation Authorization (ODA). \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\t(Agr)re consistent with the intent that was proposed in the NPRM/(76 FR 71472, November 18, 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 71472, November 18, 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 968 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n\n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tActionLabor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- General visual inspection and 28 work-hours x $85 per $2,494 $4,874 $4,718,032 \n\tbracket installation. hour = $2,380. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tWe estimate the following costs to do necessary repairs and 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 repairs. \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Drill vent holes (up to 8).................... 1 work-hour x $85 per hour = $85 $0 $85 Replace fire seal (up to 4)................... 8 work-hours x $85 per hour = 8,010 8,690 \n\t$680. ---------------------------------------------------------------------------------------------------------------- \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 regulationsfor 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.