AD 2017-10-08

We are superseding Airworthiness Directive (AD) 2009-21-01 for certain The Boeing Company Model 737-300 and 737-400 series airplanes. AD 2009-21-01 required repetitive inspections to detect cracking of the aft fuselage skin, and related investigative and corrective actions if necessary. This new AD adds certain inspections, repairs, replacement, related investigative and corrective actions if necessary; and removes certain airplanes from the applicability. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the aft fuselage skin is subject to widespread fatigue damage (WFD), and by reports of aft fuselage cracking. We are issuing this AD to address the unsafe condition on these products.

Final rule.

Adoption of the Amendment \n\n\n\tAccordingly, under the authority delegated to me by the Administrator, \n\n((Page 24471)) \n\nthe 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) 2009-21-01, Amendment 39-16038 (74 FR 52395, October 13, 2009), and adding the following new AD: \n\n2017-10-08 The Boeing Company: Amendment 39-18882; Docket No. FAA- 2016-6667; Directorate Identifier 2015-NM-125-AD. \n\n(a) Effective Date \n\n\n\tThis AD is effective July 5, 2017. \n\n(b) Affected ADs \n\n\n\tThis AD replaces AD 2009-21-01, Amendment 39-16038 (74 FR 52395, October 13, 2009) (''AD 2009-21-01''). \n\n(c) Applicability \n\n\n\t(1) This AD applies to The Boeing Company Model 737-300 series airplanes, certificated in any category, as identified in Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015 (''SASB 737-53-1168, Revision 4''). \n\t(2) Installation of Supplemental Type Certificate (STC) ST01219SE (http://rgl.faa.gov/Regulatory_and_Guidance_Library/ rgstc.nsf/0/ebd1cec7b301293e86257cb30045557a/$FILE/ST01219SE.pdf) does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST01219SE is installed, a ''change in product'' alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17. \n\n(d) Subject \n\n\n\tAir Transport Association (ATA) of America Code 53, Fuselage. \n\n(e) Unsafe Condition \n\n\n\tThis AD was prompted by an evaluation by the design approval holder (DAH) indicating that the aft fuselage skin is subject to widespread fatigue damage (WFD), and reports of aft fuselage cracking. We are issuing this AD to detect and correct cracking in the aft fuselage skin along the longitudinal edges of the chem- milled pockets in the bonded skin doubler, which could result in possible rapid decompression and reduced structural integrity of the airplane. \n\n(f) Compliance \n\n\n\tComply with this AD within the compliance times specified, unless already done. \n\n(g) Inspections, Related Investigative and Corrective Actions \n\n\n\tAt the applicable times specified in tables 1 and 2 of paragraph 1.E., ''Compliance,'' of SASB 737-53-1168, Revision 4, except as required by paragraphs (h)(1) and (h)(2) of this AD: Do the applicable inspections to detect cracks in the aft fuselage skin panels, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of SASB 737-53-1168, Revision 4, except as required by paragraphs (h)(3) and (h)(4) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections thereafter at the applicable intervals specified in tables 1 and 2 of paragraph 1.E., ''Compliance,'' of SASB 737-53- 1168, Revision 4. Accomplishment of a repair in accordance with ''Part 4: Repair'' of the Accomplishment Instructions of SASB 737- 53-1168, Revision 4, except as required by paragraph (h)(3) of this AD, is terminating action for the repetitive inspections required by this paragraph at the repaired locations only. \n\n(h) Exceptions to SASB 737-53-1168, Revision 4 \n\n\n\t(1) Where SASB 737-53-1168, Revision 4, specifies compliance times ''after the Revision 4 date of this service bulletin,'' this AD requires compliance within the specified compliance times after the effective date of this AD. \n\t(2) The Condition column of paragraph 1.E., ''Compliance,'' of SASB 737-53-1168, Revision 4, refers to airplanes in certain configurations as of the ''issue date of Revision 4 of this service bulletin.'' However, this AD applies to airplanes in the specified configurations ''as of the effective date of this AD.'' \n\t(3) Where SASB 737-53-1168, Revision 4, specifies contacting Boeing for repair instructions or work instructions, before further flight, repair or perform the work instructions using a method approved in accordance with the procedures specified in paragraph (n) of this AD, except as required by paragraph (h)(4) of this AD. \n\t(4) For airplanes on which an operator has a record that a skin panel was replaced with a production skin panel before 53,000 total flight cycles: At the applicable time for the next inspection as specified in tables 1 and 2 of paragraph 1.E., ''Compliance,'' of SASB 737-53-1168, Revision 4, except as provided by paragraph (h)(1) and (h)(2) of this AD, perform inspections and applicable corrective actions using a method approved in accordance with the procedures specified in paragraph (n) of this AD. \n\n(i) Actions for Airplanes With a Time-Limited Repair Installed \n\n\n\t(1) For airplanes with a time-limited repair installed, as specified in Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006: At the applicable times specified in table 3 of paragraph 1.E., ''Compliance,'' of SASB 737-53-1168, Revision 4, except as provided by paragraphs (h)(1) and (h)(2) of this AD, do the actions specified in paragraphs (i)(1)(i) and (i)(1)(ii) of this AD. \n\t(i) Do the applicable inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of SASB 737-53-1168, Revision 4, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections thereafter at the applicable intervals specified in SASB 737-53-1168, Revision 4. \n\t(ii) Make the time-limited repair permanent, and do all applicable related investigative and corrective actions, in accordance with Part 6 of the Accomplishment Instructions of SASB 737-53-1168, Revision 4, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Accomplishing the permanent repair required by this paragraph terminates the inspections required by paragraph (i)(1)(i) of this AD for the permanently repaired area only. \n\t(2) For airplanes with a time-limited repair installed, as specified in SASB 737-53-1168, Revision 4: At the applicable times specified in table 4 of paragraph 1.E., ''Compliance,'' of SASB 737- 53-1168, Revision 4, do the actions specified in paragraphs (i)(2)(i) and (i)(2)(ii) of this AD. \n\t(i) Do the applicable inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of SASB 737-53-1168, Revision 4, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections thereafter at the applicable intervals specified in table 4 of paragraph 1.E., ''Compliance,'' of SASB 737-53-1168, Revision 4. \n\t(ii) Make the time-limited repair permanent, and do all applicable related investigative and corrective actions, in accordance with Part 6 of the Accomplishment Instructions of SASB 737-53-1168, Revision 4, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Accomplishing the permanent repair required by this paragraph terminates the inspections required by paragraph (i)(2)(i) of this AD for the permanently repaired area only. \n\n(j) Modification of Certain Permanent Repairs \n\n\n\tFor airplanes with an existing time-limited repair that was made permanent, as specified in Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006: At the applicable times specified in table 5 of paragraph 1.E., ''Compliance,'' of SASB 737- 53-1168, Revision 4, except as provided by paragraphs (h)(1) of this AD, modify the existing permanent repair, and do all applicable related investigative and corrective actions, in accordance with Part 6 of the Accomplishment Instructions of SASB 737-53-1168, Revision 4, except as required \n\n((Page 24472)) \n\nby paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. \n\n(k) Post-Repair Inspections \n\n\n\tTable 6 of paragraph 1.E., ''Compliance,'' of SASB 737-53-1168, Revision 4, specifies post-repair airworthiness limitation inspections in compliance with 14 CFR 25.571(a)(3) at the repaired locations, which support compliance with 14 CFR 121.1109(c)(2) or 129.109(b)(2). As airworthiness limitations, these inspections are required by maintenance and operational rules. It is therefore unnecessary to mandate them in this AD. Deviations from these inspections require FAA approval, but do not require an AMOC. \n\n(l) Skin Panel Replacement \n\n\n\tAt the later of the times specified in paragraphs (l)(1), (1)(2), and (l)(3) of this AD: Replace the applicable skin panels, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of SASB 737-53- 1168, Revision 4. Do all applicable related investigative and corrective actions before further flight. Doing the skin panel replacement required by this paragraph terminates the inspection requirements of paragraphs (g), (i), and (j) of this AD for that skin panel only, provided the skin panel replacement was done with a production skin panel after 53,000 total flight cycles. \n\t(1) Before 60,000 total flight cycles, but not before 53,000 total flight cycles. \n\t(2) Within 6,000 flight cycles after the effective date of this AD, but not before 53,000 total flight cycles. \n\t(3) If the skin panel is replaced with a production skin panel, not before 53,000 total flight cycles. If the skin panel is replaced with a kit skin panel as specified in SASB 737-53-1168, Revision 4, the 53,000 total flight cycle limit does not apply. \n\n(m) Credit for Previous Actions \n\n\n\t(1) This paragraph provides credit for the actions required by paragraph (g) of this AD, if those actions were performed before the effective date of this AD using Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, except as required by paragraph (h)(4) of this AD. Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, was incorporated by reference in AD 2009- 21-01. \n\t(2) This paragraph provides credit for the actions required by paragraph (l) of this AD, if those actions were performed before the effective date of this AD using Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, except as required by paragraph (h)(4) of this AD. Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, was incorporated by reference in AD 2009- 21-01. \n\t(3) This paragraph provides credit for the actions required by paragraph (l) of this AD, if those actions were performed before November 17, 2009 (the effective date of AD 2009-21-01), using any service information specified in paragraphs (m)(3)(i), (m)(3)(ii), and (m)(3)(iii) of this AD, provided the replacement is made with a kit skin panel, except as required by paragraph (h)(4) of this AD. The service information specified in paragraphs (m)(3)(i), (m)(3)(ii), and (m)(3)(iii) of this AD was incorporated by reference in AD 2009-21-01. \n\t(i) Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1168, dated March 16, 1995. \n\t(ii) Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1168, Revision 1, dated August 17, 1995. \n\t(iii) Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1168, Revision 2, dated November 27, 1996. \n\n(n) Alternative Methods of Compliance (AMOCs)(1) The Manager, Los Angeles Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for 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 manager of the ACO, send it to the attention of the person identified in paragraph (o)(1) of this AD. Information may be emailed to: 9-ANM-LAACO-AMOC-Requests@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, modification, or alteration required by this AD if it is approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) that has been authorized by the Manager, Seattle ACO, to make those findings. To be approved, the repair method, modification deviation, or alteration deviation must meet the certification basis of the airplane and the approval must specifically refer to this AD. \n\t(4) AMOCs approved previously for repairs required by AD 2009- 21-01 are approved as AMOCs for the corresponding provisions of paragraph (g) of this AD. \n\t(5) AMOCs approved previously for modifications done as optional terminating action for AD 2009-21-01 are approved as AMOCs for the skin panel replacement required by paragraph (l) of this AD. \n\n(o) Related Information \n\n\n\t(1) For more information about this AD, contact Jennifer Tsakoumakis, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Los Angeles ACO, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5264; fax: 562-627-5210; email: jennifer.tsakoumakis@faa.gov. \n\t(2) Service information identified in this AD that is not incorporated by reference is available at the addresses specified in paragraphs (p)(3) and (p)(4) of this AD. \n\n(p) 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(i) Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015. \n\t(ii) Reserved. \n\t(3) For Boeing service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717; Internet https://www.myboeingfleet.com. \n\t(4) You may view this service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the availability of this material at the FAA, call 425-227-1221. \n\t(5) You may view this 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 2009-21-01, Amendment 39-16038 (74 FR 52395, October 13, 2009) (''AD 2009-21-01''). AD 2009-21-01 applied to certain the Boeing Company Model 737-300 and 737-400 series airplanes. The NPRM published in the Federal Register on May 13, 2016 (81 FR 29802). The NPRM was prompted by an evaluation by the DAH indicating that the aft fuselage skin is subject to WFD, and by reports of aft fuselage cracking. The NPRM proposed to continue to require repetitive inspections to detect cracking of the aft fuselage skin, and related investigative and corrective actions if necessary. The NPRM also proposed to add new aft fuselage skin inspections for cracking, inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers, permanent repairs of time-limited repairs, related investigative and corrective actions if necessary, and skinpanel replacement. The NPRM also proposed to remove Model 737-400 series airplanes from the applicability. We are issuing this AD to detect and correct cracking in the aft fuselage skin along the longitudinal edges of the chem-milled pockets in the bonded skin doubler, which could result in possible rapid decompression and reduced structural integrity of the airplane. \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\nRequest To Revise the Precipitating Event Statement \n\n\n\tBoeing requested that we revise the precipitating event statement by including that there have been reports of aft fuselage cracking. Boeing stated that this revision would be consistent with wording of other related rulemaking. \n\tWe agree with Boeing's request because it provides additional clarity to the precipitating event statement. We have revised the SUMMARY and Discussion sections, and paragraph (e) of this AD accordingly. \n\n((Page 24469)) \n\nRequest To Require Reinstalling Lap Joint Modification \n\n\n\tJet2.com Limited (Jet2) requested that we revise the NPRM to require reinstalling the lap joint modification previously installed in accordance with AD 2015-21-06, Amendment 39-18298 (80 FR 69839, November 12, 2015) (''AD 2015-21-06''), which requires the S-14 lap joint to be trimmed out prior to 50,000 total flight cycles. Jet2 stated that Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015 (''SASB 737-53-1168, Revision 4'') specifies reinstalling the lap joint modification. \n\tWe do not agree with the commenter's request. The modification required in AD 2015-21-06 consists of trimming out the lap splice, such that if this modification were installed, it would be impossible to install a new skin without reinstalling the lap modification. If the instructions in SASB 737-53-1168, Revision 4, to reinstall the lap splice modification were accidently overlooked, it would become clear to the installer that the reinstallation would be required. We have not changed this AD in this regard. \n\nRequest To Address Certain Repairs \n\n\n\tBoeing requested that we add a paragraph to the proposed AD to address repairs that are installed on the airplane for reasons other than chem-mill cracking. Boeing submitted suggested language and pointed out that the additional language is similar to that in other rulemaking. \n\tWe disagree with Boeing's request. Part 1 of the Accomplishment Instructions of SASB 737-53-1168, Revision 4, does not make a distinction regarding why an existing repair was installed. Therefore, repairs installed for damage other than a chem-mill crack are already addressed. We have not changed this AD in this regard. \n\nRequest To Revise Proposed Compliance Time \n\n\n\tBoeing requested that we revise paragraph (h)(4) of the proposed AD to do the actions at an initial compliance time obtained through the alternative method of compliance (AMOC) process specified in paragraph (n)(1) of the proposed AD. Boeing stated that the repetitive inspections would still be done at the times specified in the service information. Boeing also requested that we include in the paragraph revision the terminating action of skin panel replacement at the time approved through an AMOC. Boeing stated that its request would provide a reset on the compliance times if the skin panel was replaced prior to 53,000 total airplane cycles. Boeing explained that its authorized representative under the Boeing Commercial Airplanes Organization Designation Authorization (ODA) cannot approve extensions to the compliance times. \n\tWe partially agree with Boeing's request. We agree that, for airplanes with skin panels replaced prior to 53,000 total flight cycles, in order to reset the inspection threshold on the replaced skin panels, approval must come from the FAA. Under the provisions of paragraph (n) of this AD, we may consider requests for a reset of the compliance times if the skin panel was replaced prior to 53,000 total airplane cycles 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 Specify the Service Information Accomplishment Instructions Part Numbers \n\n\n\tBoeing requested that we add the specific part of the accomplishment instructions in paragraphs (i)(1)(ii), (i)(2)(ii), and (j) of the proposed AD. Boeing stated that paragraph (g) of the proposed AD specifies the specific part number, and that this change would make these paragraphs consistent with the wording in paragraph (g) of the proposed AD. \n\tWe agree with Boeing's request. We agree that specifying the specific part of the Accomplishment Instructions of SASB 737-53-1168, Revision 4, will add clarity to the AD. We have revised paragraphs (i)(1)(ii), (i)(2)(ii), and (j) of this AD accordingly. \n\nRequest To Revise Flight Cycle Limit for Replacement Kit Skin Panels \n\n\n\tBoeing requested that we revise paragraph (l) of the proposed AD to specify that skin panel replacements using the kit identified in SASB 737-53-1168, Revision 4, do not have the lower flight cycle limit restriction that the production skin panel replacements have. \n\tWe agree with Boeing's request because the skin panel replacements using the kit identified in SASB 737-53-1168, Revision 4, is an improved design compared to the production skin panels, and therefore, do not need the lower flight cycle limit restriction. We have added paragraph (l)(3) to this AD, which states, in part, that if the skin panel is replaced with a kit skin panel as specified in SASB 737-53- 1168, Revision 4, the 53,000 total flight cycle limit does not apply. \n\nRequest To Remove Flight-Cycle Restriction for Certain Actions \n\n\n\tBoeing requested that we revise paragraphs (m)(2), (m)(3), and (n)(5) of the proposed AD to remove the flightcycle restriction for certain previously accomplished actions using certain service information. Boeing stated that the only skin panel replacements specified in previous revisions of SASB 737-53-1168 are those using the kit panels, and that those panels do not have the flight-cycle limit specified in paragraphs (m)(2), (m)(3), and (n)(5) of the proposed AD. \n\tWe agree with the commenter's request because the skin panel replacements using the kit identified in SASB 737-53-1168, Revision 4, are an improved design compared to the production skin panels, and therefore, do not need the lower flight cycle limit restriction. We have revised paragraphs (m)(2), (m)(3), and (n)(5) of this AD accordingly. \n\nRequest To Specify Terminating Action \n\n\n\tQantas Airways Limited (Qantas) requested that we revise paragraphs (g) and (l) of the proposed AD to specify terminating action. Qantas pointed out that replacing the skin panels with kit panels instead of production panels, as specified in SASB 737-53-1168, terminates the repetitive inspections identified in paragraphs (g), (i), and (j) of the proposed AD. Additionally, Qantas pointed out that replacement with kit skin panels using any revision of SASB 737-53-1168 before the effective date of the AD should also terminate the repetitive inspections identified in paragraphs (g), (i), and (j) of the proposed AD. \n\tWe agree with the commenter's request because the skin panel replacements using the kit identified in SASB 737-53-1168, Revision 4, are an improved design compared to the production skin panels and therefore, should terminate the repetitive inspections. We have revised paragraphs (m)(2), (m)(3), and (n)(5) of this AD accordingly. \n\nEffect of Winglets on Accomplishment of the Proposed Actions \n\n\n\tAviation Partners Boeing stated that accomplishing Supplemental Type Certificate (STC) ST01219SE does not affect the actions specified in the NPRM. \n\tWe concur with the commenter. We have redesignated paragraph (c) ofthe proposed AD as paragraph (c)(1) of this AD and added paragraph (c)(2) to this AD to state that installation of STC ST01219SE does not affect the ability to \n\n((Page 24470)) \n\naccomplish the actions required by this final rule. Therefore, for airplanes on which STC ST01219SE is installed, a ''change in product'' AMOC approval request is not necessary to comply with the requirements of 14 CFR 39.17. \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 SASB 737-53-1168, Revision 4. The service information describes procedures for doing inspections of the fuselage skin, repairs, and skin panel replacement. 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 affects 168 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product Cost on U.S. operators ---------------------------------------------------------------------------------------------------------------- Inspections.................. Up to 1,791 work-$0 Up to $152,235. Up to $25,575,480. \n\thours x $85 per \n\thour = $152,235. Skin replacement............. 624 work-hours x $85 98,275 $151,315....... $25,420,920. \n\tper hour = $53,040. ---------------------------------------------------------------------------------------------------------------- \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 ---------------------------------------------------------------------------------------------------------------- Time-limited repair............. 24 work-hours x $85 per (\1\) $2,040 per repair. \n\thour = $2,040 per \n\trepair. Permanent repair................ Up to 43 work(dash)hours (\1\) Up to $3,655 per repair. \n\tx $85 per hour = $3,655 \n\tper repair. ---------------------------------------------------------------------------------------------------------------- \1\ We have received no definitive data that would enable us to provide the part cost estimates for the on- \n\tcondition actions specified in this AD. \n\n\n\tWe estimate the following costs to do any necessary post-repair inspections that would be required. We have no way of determining the number of aircraft that might need these inspections: \n\n\n\tPost-Repair Inspection Costs ---------------------------------------------------------------------------------------------------------------- \n\tAction Labor cost Parts cost Cost per product ---------------------------------------------------------------------------------------------------------------- Post-repair inspection.......... Up to 7 work(dash)hours $0 Up to $595. \n\tx $85 per hour = $595. ---------------------------------------------------------------------------------------------------------------- \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 likelyto 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.