AD 2012-15-15

We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 757-200, -200CB, and -300 series airplanes. That AD currently requires initial and repetitive inspections of the fuselage skin and bear strap at the forward, upper corner of the L1 entry door cutout for cracking, and repair if necessary. That action also provides an optional terminating action for the repetitive inspections. This new AD requires additional inspections for airplanes having repairs or preventative modifications installed and inspections for certain other airplanes. This AD also adds airplanes to the applicability. This AD was prompted by reports of additional cracking in the fuselage skin. We are issuing this AD to detect and correct cracking of the fuselage skin and bear strap at the forward upper corner of the L1 entry door cutout, which could result in reduced structural integrity of the L1 entry door, and consequent rapid decompression of the airplane.

Final rule.

Adoption of the Amendment \n\n\n\tAccordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n0 1. The authority citation for part 39 continues to read as follows: \n\n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n\n\nSec. 39.13 (Amended) \n\n0 2. The FAA amends Sec. 39.13 by removing airworthiness directive (AD) 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004), and adding the following new AD: \n\n2012-15-15 The Boeing Company: Amendment 39-17144; Docket No. FAA- 2011-1326; Directorate Identifier 2010-NM-177-AD. \n\n(a) Effective Date \n\n\n\tThis airworthiness directive (AD) is effective October 3, 2012. \n\n(b) Affected ADs \n\n\n\tThis AD supersedes AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004). \n\n(c) Applicability \n\n\n\tThis AD applies to all The Boeing Company Model 757-200, -200CB, and -300 series airplanes, certificated in any category. Model 757- 200PFseries airplanes are not affected by this AD. \n\n(d) Subject \n\n\n\tJoint Aircraft System Component (JASC)/Air Transport Association (ATA) of America Code 53: Fuselage. \n\n(e) Unsafe Condition \n\n\n\tThis AD was prompted by reports of additional cracking in the fuselage skin and bear strap at the forward upper corner of the L1 entry door cutout. We are issuing this AD to detect and correct cracking of the fuselage skin and bear strap at the forward upper corner of the L1 entry door cutout, which could result in reduced structural integrity of the L1 entry door, and consequent rapid decompression of the airplane. \n\n(f) Compliance \n\n\n\tComply with this AD within the compliance times specified, unless already done. \n\n((Page 52216)) \n\n(g) Retained Initial Inspections \n\n\n\tThis paragraph restates the requirements of paragraph (a) of AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004), with a new terminating action. For airplanes having line numbers 1 through 90 inclusive: Within 500 flight cycles after May 24, 2004 (the effective date of AD 2004-09-32), or within 90 days after May 24, 2004 (the effective date of AD 2004-09-32), whichever occurs later, do the inspections of the forward upper corner of the L1 entry door cutout specified in paragraphs (g)(1), (g)(2), and (g)(3) of this AD, per Part 1 of the Work Instructions of Boeing Special Attention Service Bulletin 757-53-0089, dated March 18, 2004, until the initial inspection required by paragraph (k) of this AD has been done. Doing the repair specified in paragraph (i) or (l) of this AD, or doing the preventive modification specified in paragraph (j) of this AD, terminates the inspections required by this paragraph. \n\t(1) Do a high frequency eddy current (HFEC) inspection for cracking of the fuselage skin around the adjacent fasteners. \n\t(2) Do an HFEC inspection for cracking along the edge of the skin and bear strap. \n\t(3) Do a low frequency eddy current (LFEC) inspection for cracking of thebear strap around each fastener. \n\n(h) Retained: Repetitive Inspections and New Terminating Modification When No Crack Is Detected \n\n\n\tThis paragraph restates the requirements of paragraph (b) of AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004), with a new terminating modification. If no crack is detected during any inspection required by paragraph (g) of this AD: Repeat the inspections required by paragraph (g) of this AD at intervals not to exceed 1,400 flight cycles, until the requirements of paragraph (k) of this AD are done. Doing the repair specified in paragraph (i) or (l) of this AD, or doing the preventive modification specified in paragraph (j) of this AD, as applicable, terminates the repetitive inspections required by this paragraph. \n\n(i) Retained: Repair, With New Repair Option When Any Crack Is Detected \n\n\n\tThis paragraph restates the requirements of paragraph (c) of AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004), with a new repair option. If any crack is detected during any inspection required by paragraph (g) or (h) of this AD, and Boeing Special Attention Service Bulletin 757-53-0089, dated March 18, 2004, specifies to contact Boeing for appropriate action: Before further flight, repair, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or in accordance with data meeting the type certification basis of the airplane approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) that has been authorized by the Manager, Seattle ACO, to make such findings; or using a method approved in accordance with the procedures specified in paragraph (r) of this AD. For a repair method to be approved, the approval must specifically reference this AD. Doing the repair terminates the inspections required by paragraphs (g) and (h) of this AD. \n\n(j) Retained Optional Preventive Modification \n\n\n\tThis paragraph restates the optional preventive modification specified in paragraph (d) of AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004); As an alternative to accomplishing the inspections required by paragraphs (g) and (h) of this AD, do the optional preventative modification of the forward upper corner of the L1 entry door cutout, and do all applicable related investigative/corrective actions, by accomplishing all the actions specified in Part 2 of the Work Instructions of Boeing Special Attention Service Bulletin 757-53-0089, dated March 18, 2004. Accomplishment of the modification constitutes terminating action for the inspections required by paragraphs (g) and (h) of this AD. \n\n(k) New Inspections \n\n\n\tFor airplanes in Group 1, Configurations 1 and 2, and Group 2, Configuration 1 as defined in Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009: Except as provided by paragraph (p)(1) of this AD, at the applicable times specified in paragraph 1.E, ''Compliance,'' of Boeing SpecialAttention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, do HFEC and LFEC inspections for cracking of the skin and bear strap at the forward upper corner of the L1 entry door cutout, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, except as provided by paragraph (p) of this AD. Repeat the inspections thereafter at intervals not to exceed 1,400 flight cycles. Doing the initial inspection required by this paragraph terminates the inspections required by paragraphs (g) and (h) of this AD. Doing the repair specified in paragraph (l) of this AD, or doing the optional preventive modification specified in paragraph (m) of this AD, terminates the inspections required by this paragraph. \n\n(l) New Terminating Repair \n\n\n\tIf any cracking is found during any inspection required by paragraph (k) of this AD, before further flight, repair in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, except as required by paragraph (p) of this AD. Doing the repair terminates the repetitive inspections required by paragraph (k) of this AD. \n\n(m) Optional Preventive Modification \n\n\n\tAccomplishing the optional preventive modification, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, except as provided by paragraph (p) of this AD, terminates the repetitive inspections required by paragraph (k) of this AD. \n\n(n) New Inspections and Repair \n\n\n\tFor airplanes in Group 1, Configurations 3 and 5, and Group 2, Configurations 2 and 4, as identified in Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, with a repair doubler; a doubler and a tripler; or a doubler, tripler, and quadrupler installed; or with a preventive modification doubler installed: At theapplicable times specified in paragraph 1.E, ''Compliance,'' of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, except as required by paragraph (p)(2) of this AD, do LFEC, HFEC, and detailed inspections, as applicable, for cracking of the doubler, tripler, quadrupler, skin, bear strap, and inner chord strap, as applicable, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009. Repeat the inspections thereafter at the applicable times specified in paragraph 1.E., ''Compliance,'' of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009. \n\n(o) New Repair \n\n\n\tIf any cracking is found during any inspection required by paragraph (n) of this AD, before further flight, repair the crack in accordance with the procedures specified in paragraph (r) of this AD. \n\n(p) New Exceptions to Service Bulletin Specifications \n\n\n\tThefollowing exceptions apply to this AD. \n\t(1) Where Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, specifies a compliance time after the ''original issue date'' or ''Revision 1 date of the service bulletin,'' this AD requires compliance within the specified compliance time after the effective date of this AD. \n\t(2) Where Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, specifies doing the HFEC, LFEC, and detailed inspections required by paragraph (n) of this AD before the accumulation of 37,500 total flight cycles, this AD requires the inspections to be accomplished at the latest of the times specified in paragraphs (p)(2)(i), (p)(2)(ii), and (p)(2)(iii) of this AD. \n\t(i) Before the accumulation of 37,500 total flight cycles. \n\t(ii) Within 24 months after the effective date of this AD. \n\t(iii) Within 4,000 flight cycles since installation of a repair doubler; a doubler and a tripler; or a doubler,tripler, and quadrupler; or on which a preventive modification doubler is installed; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, or in accordance with paragraph (h) of this AD. \n\t(3) Where Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, specifies contacting Boeing for repair instructions, this AD requires repairing in accordance with the procedures specified in paragraph (r) of this AD. \n\t(4) Where Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated \n\n((Page 52217)) \n\nAugust 12, 2009, specifies a specific fastener and material to be used for accomplishing a repair, this AD allows the substitution of fastener and material, as specified in Chapter 51 of the Boeing 757 Structural Repair Manual. \n\t(5) Where Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, specifies a specific fastener grip length, this AD allows substitution of a fastener grip length, as specified in Chapter 51 of the Boeing 757 Structural Repair Manual. \n\t(6) If it is necessary to remove more parts for access, those parts may be removed. If access is possible without removing identified parts, it is not necessary to remove all of the identified parts. \n\n(q) Credit for Previous Actions \n\n\n\tFor airplanes in Group 1, Configurations 1 and 2; and Group 2, Configuration 1; as defined in Boeing Special Attention 757-53-0094, Revision 1, dated August 12, 2009: This paragraph provides credit for the actions required by paragraph (k) of this AD, if those actions were performed before the effective date of this AD using Boeing Special Attention Service Bulletin 757-53-0094, dated January 16, 2008, or using Special Attention Service Bulletin 757-53-0089, dated March 18, 2004. \n\n(r) Alternative Methods of Compliance (AMOCs) \n\n\n\t(1) The Manager, Seattle ACO, FAA, has the authority to approve AMOCsfor this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the ACO, send it to ATTN: Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, 1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: 425-917-6440; fax: 425-917-6432; email: nancy.marsh@faa.gov. \n\t(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office. \n\t(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD if it is approved by the Boeing Commercial Airplanes ODA that has been authorized by the Manager, Seattle ACO to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD. \n\t(4) AMOCs previously approved in accordance with AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004), are approved as AMOCs for the corresponding actions specified in paragraphs (g), (h), and (i) of this AD. \n\n(s) Related Information \n\n\n\tFor more information about this AD, contact Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, 1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: 425-917-6440; fax: 425- 917-6432; email: nancy.marsh@faa.gov. \n\n(t) Material Incorporated by Reference \n\n\n\t(1) The Director of the Federal Register approved the incorporation by reference (IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51. \n\t(2) You must use this service information as applicable to do the actions required by this AD, unless the AD specifies otherwise. \n\t(3) The following service information was approved for IBR on October 3, 2012. \n\t(i) Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009. \n\t(ii) Reserved. \n\t(4) The following service information was approved for IBR on May 24, 2004 (69 FR 25481, May 7, 2004). \n\t(i) Boeing Special Attention Service Bulletin 757-53-0089, dated March 18, 2004. \n\t(ii) Reserved. \n\t(5) For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone 206-544-5000, extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. \n\t(6) You may review copies of the service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221. \n\t(7) You may also review copies of the service information that is incorporated by reference at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr_locations.html.

Discussion \n\n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004). That AD applies to the specified products. The NPRM published in the Federal Register on December 29, 2011 (76 FR 81890). That NPRM proposed to continue to require initial and repetitive inspections of the fuselage skin and bear strap at the forward upper corner of the L1 entry door cutout for cracking, and repair if necessary. That NPRM also provided an optional terminating action for the repetitive inspections. That NPRM also proposed to require additional inspections for airplanes having repairs or preventative modifications installed and inspections for certain other airplanes. That NPRM also proposed to add airplanes to the applicability. \n\nComments \n\n\n\tWe gave the public the opportunity to participate in developing this AD. The \n\n((Page 52213)) \n\nfollowing presents the commentsreceived on the proposal (76 FR 81890, December 29, 2011) and the FAA's response to each comment. \n\nRequest To Add Compliance Time for Group 2 Airplanes \n\n\n\tAllegiant Air requested that we revise paragraph (k) of the NPRM (76 FR 81890, December 29, 2011) to include a 90-day compliance time for airplanes in Group 2. The commenter stated that Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, specifies a compliance time after the ''original issue date'' or ''Revision 1 date of the service bulletin.'' Allegiant Air stated that Group 2 airplanes may have accumulated more than 500 flight cycles since August 12, 2009 (the issue date of Boeing Special Attention Service Bulletin 757-53-0094, Revision 1), and therefore airplanes would be non-compliant with the AD as soon as the AD is published. \n\tWe partially agree with the commenter. We disagree with adding a 90-day compliance time because paragraph (p)(1) of the AD includes an exception to the compliance times that refers to the dates in Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009. However, we have clarified paragraph (k) of this AD by referring to paragraph (p)(1) of this AD as an exception to the compliance times. We have also revised the language in paragraph (p)(1) of this AD for clarity. \n\nRequest To Change Repetitive Intervals \n\n\n\tAmerican Airlines (AAL) and United Airlines (United) requested that we extend the repetitive intervals. AAL requested that we change the repetitive intervals specified in paragraphs (h) and (k) of the NPRM (76 FR 81890, December 29, 2011) from 1,400 flight cycles to 2,200 flight cycles. AAL stated that they have inspected over 50 percent of its fleet prior to the effective date of the NPRM, and have had no findings. AAL believes that the repetitive interval could be extended without jeopardizing safety. United requested that we lengthen the interval of the repetitive inspections from 1,400 flightcycles to 3,000 flight cycles, to align with normally scheduled maintenance. United also noted that other areas of the airplane fuselage skin shown in the Boeing structural repair manual (SRM) have intervals as long as 3,000 flight cycles. \n\tWe disagree with changing the repetitive interval as requested. A damage tolerance analysis of the predicted crack growth rate is used to establish the repetitive intervals of 1,400 flight cycles. These repetitive intervals must include the variability of crack growth rate between airplanes and include a probability of detection of the cracks for the method used for the inspection. The door surround structure appears to have higher stress levels than the other portions of the fuselage skin inspected by the repairs in the Boeing SRM. This is the main cause for the fatigue cracking addressed by Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009. The other areas of fuselage skin in the Boeing SRM have not demonstrated this premature fatigue cracking requiring the higher repetitive inspection intervals. We have determined that the 1,400 flight cycle interval is necessary to address the identified unsafe condition. No change has been made to this AD in this regard; however, operators may request an alternative method of compliance (AMOC) according to the provision of paragraph (r) of this AD, if the request is submitted with substantiating data that proves the repetitive interval will provide an adequate level of safety. \n\nRequest To Add Option for Repetitive Inspection Intervals \n\n\n\tAAL requested that we revise the 1,400 flight cycle intervals for the eddy current inspection to include an option for a 1,000 flight cycle detailed inspection combined with a 3,000 flight cycle eddy current inspection to permit the eddy current inspections to be accomplished during normally scheduled maintenance intervals. \n\tWe disagree. Since no analysis was provided to demonstrate that the proposal provides an acceptable level of safety, we disagree with adding the requested option. It is unlikely that an analysis would demonstrate that the requested 1,000 flight cycle detailed inspections are adequate compared to the probability of detection by the eddy current inspections at 1,400 flight cycles, since the eddy current inspection methods are used to find very small cracks not readily detected by the human eye. Further, the inspections of the bear strap structure cannot be accomplished visually since the bear strap is covered by the fuselage skin. According to the provisions of paragraph (r) of this AD, operators may request an AMOC to include an option to the repetitive inspection intervals, if the request is submitted with substantiating data that proves that the alternate method and intervals will provide an adequate level of safety. No change has been made to this AD in this regard. \n\nRequest To Revise Compliance Time \n\n\n\tUnited requested that we revise the compliance time to increase the time allowed after the effective date from 500 flight cycles to 1,400 flight cycles. United stated that it would be a better transition for implementation of the inspections as 1,400 flight cycles would permit normal scheduling for the airplanes. \n\tWe disagree with revising the compliance time. In developing an appropriate compliance time for this AD, we considered not only the safety implications, but the manufacturer's recommendations, the availability of required parts, and the practical aspect of accomplishing the inspections within an interval of time that corresponds to typical scheduled maintenance for affected operators. Under the provisions of paragraph (r) of this AD, however, we may consider requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety. \n\nRequest Credit for Repetitive Inspections Defined in Figure 1 of Boeing Special Attention Service Bulletin 757-53-0089, Dated March 18, 2004 \n\n\n\tDelta Airlines, Inc. (Delta) requested that we revise the NPRM (76 FR 81890, December 29, 2011) to give credit for the inspections done using Figure 1 of Boeing Special Attention Service Bulletin 757-53- 0089, dated March 18, 2004. This service bulletin is the appropriate source of service information for accomplishing the actions required by AD 2004-09-32, Amendment 39-13622 (69 FR 25481, May 7, 2004). Delta stated that the new inspections would be required in less than 500 flight cycles after the effective date of the new AD for airplanes that were already on the 1,400 flight cycle repetitive inspection required by AD 2004-09-32. \n\tWe disagree with this request to revise this AD. The inspections specified in Figure 1 in both Boeing Special Attention Service Bulletin 757-53-0089, dated March 18, 2004; and Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009; are the same method, locations, and sections of the Boeing757 Non-destructive Testing Manual. Since paragraph (f) of this AD already provides credit for previous accomplishment of the inspection, no change has been made to the AD in this regard. \n\n((Page 52214)) \n\nRequest To Revise Applicability \n\n\n\tUPS requested that we revise paragraph (c) of the NPRM (76 FR 81890, December 29, 2011) to add the text, ''as specified in Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009.'' UPS stated that the NPRM is applicable to all Model 757-200 airplanes. \n\tWe agree to clarify the applicability paragraph. All Model 757-200, -200CB, and -300 series airplanes are affected by this AD, as specified in paragraph (c) of this AD. Model 757-200PF airplanes are not listed in the applicability and are not affected by the identified unsafe condition. We have clarified paragraph (c) of this AD by adding a sentence that specifies that Model 757-200PF series airplanes are not affected by this AD. \n\nRequest To Clarify Paragraph (g)(3) of the NPRM (76 FR 81890, December 29, 2011) \n\n\n\tBoeing requested that we clarify paragraph (g)(3) of the NPRM (76 FR 81890, December 29, 2011) by adding the text, ''around each fastener of the subject door edge corner for cracking,'' to be consistent with paragraphs (g)(1) and (g)(2) of the NPRM. \n\tWe disagree with the request. Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009, clearly defines the inspection. No change has been made to the AD in this regard. \n\nRequest To Clarify Access Steps \n\n\n\tAAL requested that we add a statement to clarify the steps required to access the inspection area. AAL stated that this note is included in many Boeing service bulletins, but was not included in Boeing Special Attention Service Bulletin 757-53-0094, dated January 16, 2008; or Boeing Special Attention Service Bulletin 757-53-0094, Revision 1, dated August 12, 2009. \n\tWe agree that clarification is needed. We have added paragraph (p)(6) to this AD to state that if it is necessary to remove more parts for access, you may remove those parts, but it is not necessary to remove all of the parts. We have also added a reference to paragraph (p)(6) in paragraph (k) of this AD. \n\nRequest To Clarify Paragraph (n) of the NPRM (76 FR 81890, December 29, 2011) \n\n\n\tBoeing requested that we clarify paragraph (n) of the NPRM (76 FR 81890, December 29, 2011) by revising the text from, ''a repair doubler, tripler, or quadrupler is installed;'' to ''a repair doubler; a doubler and a tripler; or a doubler, tripler, and quadrupler.'' Boeing stated that a tripler installation also has a doubler installed, and a quadrupler installation also has a doubler and a tripler installed. Each combination has unique inspection requirements. \n\tWe agree that the requested text would provide clarity to the operators. Paragraph (n) of this AD has been revised to include the text, ''a repair doubler; a doubler and a tripler; or a doubler, tripler, and quadrupler.'' \n\nRequest To Revise Compliance Time Exceptions \n\n\n\tDelta requested that the exceptions to certain compliance times in paragraph (p)(2) of the NPRM (76 FR 81890, December 29, 2011), be revised to include a third option of 4,000 flight cycles since installation of the preventive modification or repair. Delta stated that, by adding a third criteria of 4,000 flight cycles after installation, the inspection would be required at the next repetitive interval. \n\tWe agree that an optional compliance time is needed. In the case of an airplane that has more than 37,500 total flight cycles and has had the modification or the required repair installed more than 24 months after the effective date of the AD, the inspections would be required immediately. We have added paragraph (p)(2)(iii) to this AD to add an optional compliance time of 4,000 flight cycles since installation of the preventive modification or repair. \n\nRequest To Permit Fastener and Material SubstitutionAAL requested that the NPRM (76 FR 81890, December 29, 2011) be revised to allow substitution of certain fasteners and materials as specified in Chapter 51 of the Boeing 757 SRM and Boeing Drawing 65- 88700. \n\tWe partially agree with the request. We disagree because Boeing Drawing 65-88700 is not an FAA-approved document. However, we agree that the Boeing 757 SRM, which is an FAA-approved document, is an appropriate source of information for fastener and material substitution. We have added paragraph (p)(4) to this AD to allow fasteners and material to be substituted, as specified in Chapter 51 of the Boeing 757 SRM to be used as an appropriate source of information for fastener and material substitution. We have also revised paragraphs (l) and (m) of this AD to refer to this exception. \n\nRequest To Permit Fastener Grip Length Adjustment Substitution \n\n\n\tAAL requested that we permit fastener grip length adjustment substitution and washer installation for fastener grip length, as specified in Chapter 51 of the Boeing 757 SRM. \n\tWe agree that Chapter 51 of the Boeing 757 SRM is an appropriate source for fastener grip length adjustment substitution. We have added paragraph (p)(5) to this AD to allow Chapter 51 of the Boeing 757 SRM to be used as an appropriate source of information for fastener grip length adjustment substitutions. We have also revised paragraphs (l) and (m) of this AD to refer to this exception. \n\nRequest To Allow Credit for Previous Inspections \n\n\n\tAAL requested that we allow credit for inspections done previously using Boeing Special Attention Service Bulletin 757-53-0094, dated January 16, 2008. \n\tWe agree. We have added paragraph (q) to this AD to allow the inspections for airplanes in Group 1, Configurations 1 and 2; and Group 2, Configuration 1; as defined in Boeing Special Attention 757-53-0094, Revision 1, dated August 12, 2009, done prior to the effective date of this AD, if done using Boeing Special Attention Service Bulletin 757- 53-0094, dated January 16, 2008. We have also updated subsequent paragraph identifiers accordingly. \n\nOther Changes Made to This AD \n\n\n\tWe have revised certain headings throughout this AD. We have also revised paragraph (h) of this AD to specify that the repair in paragraph (i) of this AD also terminates the repetitive 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 81890, December 29, 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 81890, December 29, 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\n((Page 52215)) \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 591 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tNumber of U.S.- \n\tAction Work-hours Average labor Cost per registered Fleet cost \n\trate per hour airplane airplanes ---------------------------------------------------------------------------------------------------------------- Inspections (retained actions 2 $85 $170 per 57 $9,690 per \n\tfrom existing AD 2004-09-32, inspection inspection \n\tAmendment 39-13622 (69 FR cycle. cycle. \n\t25481, May 7, 2004)). Inspection (new action)......3 85 $255 per 591 $150,705 per \n\tinspection inspection \n\tcycle. cycle. Inspection (new action)...... 15 85 $1,275 per 591 $753,525 per \n\tinspection inspection \n\tcycle. cycle. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tWe estimate the following costs to do any necessary repairs that would be required based on the results of the inspections. We have no way of determining the number of aircraft that might need these repairs: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tAction Labor cost Parts cost Cost per product ---------------------------------------------------------------------------------------------------------------- Repair............................... Up to 26 work-hours x Up to $2,661........... Up to $4,871 depending \n\t$85 = Up to $2,210. on configuration. Preventive modification.............. 18 work-hours x $85 = $1,338................. $2,868 \n\t$1,530. ---------------------------------------------------------------------------------------------------------------- \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\tWe have determined that this 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.