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 Department of Transportation Federal Aviation Administration 14 CFR Part 39
[Docket No. FAA-2007-28283; Directorate Identifier 2006-NM-254-AD]
RIN 2120-AA64
 AGENCY: Federal Aviation Administration (FAA), DOT.
 ACTION: Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.
 SUMMARY: We are revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. The original NPRM would have required a one-time general visual inspection of frames between body station (BS) 360 and BS 907 to determine if certain support brackets of the air conditioning (A/C) outlet extrusions are installed; medium- and high-frequency eddy current inspections for cracking of the frames around the attachment holes of the subject brackets; and repair if necessary. The original NPRM would also have required installing new, improved fittings for all support brackets of the A/C outlet extrusions between BS 360 and BS 907. The original NPRM resulted from numerous reports of multiple cracks in the frames around the attachment holes of certain support brackets of the A/C outlet extrusions. This action revises the original NPRM by adding an airplane to the applicability and reducing the compliance time for certain airplanes. We are proposing this supplemental NPRM to prevent frame cracking, which, if not corrected, could lead to a severed frame that, combined with cracking of the skin lap splice above stringer 10, could result in rapid decompression of the airplane.
 DATES: We must receive comments on this supplemental NPRM by September 15, 2008.
 ADDRESSES: You may send comments by any of the following methods: *Federal eRulemaking Portal:*
                         Go to 
                        *http://www.regulations.gov*. Follow the instructions for submitting comments.
                    *Fax:*
                         202-493-2251.
                    *Mail:*
                         U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
                    *Hand Delivery:*
                         U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for the service information identified in this proposed AD. Examining the AD Docket You may examine the AD docket on the Internet at 
                    *http://www.regulations.gov*; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone 800-647-5527) is in the 
                    **ADDRESSES**
                     section. Comments will be available in the AD docket shortly after receipt.
 FOR FURTHER INFORMATION CONTACT: Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6447; fax (425) 917-6590.


SUPPLEMENTARY INFORMATION: Comments Invited We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the 
                    **ADDRESSES**
                     section. Include “Docket No. FAA-2007-28283; Directorate Identifier 2006-NM-254-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments. We will post all comments we receive, without change, to 
                    *http://www.regulations.gov*, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD. Discussion We issued a notice of proposed rulemaking (NPRM) (the “original NPRM”) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. That original NPRM was published in the 
                    **Federal Register**
                     on May 25, 2007 (72 FR 29280). That original NPRM proposed to require a one-time general visual inspection of frames between body station (BS) 360 and BS 907 to determine if certain support brackets of the air conditioning (A/C) outlet extrusions are installed; medium- and high-frequency eddy current inspections for cracking of the frames around the attachment holes of the subject brackets; and repair if necessary. That original NPRM also proposed to require installing new, improved fittings for all support brackets of the A/C outlet extrusions between BS 360 and BS 907. Actions Since Original NPRM Was Issued Since we issued the original NPRM, Boeing has issued Special Attention Service Bulletin 737-25-1544, Revision 1, dated January 16, 2008. The revised service bulletin adds an airplane to the effectivity and deletes all references to an unreleased service bulletin. The service bulletin also reduces inspection thresholds for airplanes on which Boeing Business Jet (BBJ) lower cabin altitude modification has been incorporated in accordance with Supplemental Type Certificate (STC) ST01697SE. Comments We gave the public the opportunity to participate in developing this AD. We considered the comments received from the commenters. 
                    ( print page 48308) Support for the Original NPRM Boeing concurs with the content of the original NPRM. Request To Clarify Inspection Requirements AirTran Airways requests that we clarify the inspection requirements of the NPRM. AirTran suggests that we revise paragraphs (g) and (h) of the NPRM to specify that, in accordance with Boeing Special Attention Service Bulletin 737-25-1544, dated October 4, 2006, some frames between body station (BS) 360 and BS 907 are excluded from the inspection requirements of the service bulletin. AirTran asserts that this will help to ensure that the inspection requirements of the original NPRM do not deviate from the procedures described in the service bulletin. We partially agree with this request. Some frames are machined or fabricated from a thicker material or have a three-rivet attachment fitting, rather than the two-rivet attachment fitting. Further, the notes of Step 3.B.1 of “Part 1—Access” of the Accomplishment Instructions of the service bulletin specify that these frames are not subject to the inspections. Therefore, we have revised paragraph (g) of the supplemental NPRM to clarify that certain frames are not subject to the inspection requirements of the proposed AD. However, paragraph (h) of the supplemental NPRM refers to the modification, which affects all frames between BS 360 and BS 907; therefore, it is not appropriate to exempt the frames specified by the commenter from the requirements of paragraph (h) of the supplemental NPRM. As specified in paragraph (h) of the supplemental NPRM all frames are affected. We have not changed the supplemental NPRM in this regard. Compliance Time for Certain Airplanes We have determined from Boeing Special Attention Service Bulletin 737-25-1544, Revision 1, dated January 16, 2008, that the compliance time for airplanes on which BBJ lower cabin altitude modification has been incorporated in accordance with STC ST01697SE must be reduced by one-half for the flight cycle compliance time. Therefore, we have added new paragraph (i) to the supplemental NPRM to define the compliance time for these airplanes as: Before the accumulation of 18,000 total flight cycles, or within 72 months after the effective date of this AD, whichever occurs later. Credit for Use of Original Issue of Service Bulletin We have revised this supplemental NPRM to refer to Boeing Special Attention Service Bulletin 737-25-1544, Revision 1, dated January 16, 2008, as the appropriate source of service information for doing the requirements of the proposed AD. Therefore, we have added new paragraph (j) to the supplemental NPRM to give credit for actions done prior to the effective date of the AD according to Boeing Special Attention Service Bulletin 737-25-1544, dated October 4, 2006. We have also re-identified paragraph (i) of the original NPRM as paragraph (k) of the supplemental NPRM. Clarification of Paragraph (g)(1) of the NPRM Paragraph (g)(1) of the NPRM specifies that for any support bracket not attached with a two-rivet attachment fitting, no further action is required by paragraph (g) of the NPRM. We have revised paragraph (g)(1) of the supplemental NPRM to specify that for any support bracket attached with three or more rivets, no further action is required by paragraph (g) of the supplemental NPRM. Clarification of Compliance Time in Paragraph (g)(2) of the NPRM Paragraph (g)(2) of the NPRM does not specify a compliance time for doing the inspections specified in that paragraph. We intended that the inspections be done within the same compliance time specified in paragraph (g) of the NPRM. We have added the compliance time specified in paragraph (g) of the supplemental NPRM to paragraph (g)(2) of the supplemental NPRM. Clarification of Unsafe Condition Statement We have replaced the phrase “to detect and correct” in the unsafe condition statement in the Summary and in paragraph (d) of the supplemental NPRM with the phrase “to prevent” to clarify that the actions in this supplemental NPRM are intended to prevent the identified unsafe condition. FAA's Determination and Proposed Requirements of the Supplemental NPRM We are proposing this supplemental NPRM because we evaluated all pertinent information and determined an unsafe condition exists and is likely to exist or develop on other products of the same type design. Certain changes described above expand the scope of the original NPRM. As a result, we have determined that it is necessary to reopen the comment period to provide additional opportunity for the public to comment on this supplemental NPRM. Costs of Compliance There are about 1,679 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 626 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD, at an average labor rate of $80 per work hour. Operators should note that special cold working tools and sleeves will be needed if any repair is required, which may increase costs. Estimated Costs
Action
Work hours
Parts
Cost per airplane
Fleet costGeneral visual inspection
1
No parts required
$80
$50,080.MFEC and HFEC inspections
Between 170 and 216
No parts required
Between $13,600 and $17,280
Up to $10,817,280.Replace support fittings
Between 258 and 346
Between $56,095 and $81,339
Between $76,735 and $109,019
Up to $68,245,894.
 Authority for This Rulemaking Title 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. We are issuing this rulemaking under the authority described in “Subtitle VII, Part A, Subpart III, Section 44701: 
                    ( print page 48309)
                    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. Regulatory Findings We determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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. For the reasons discussed above, I certify this proposed regulation: 1. Is not a “significant regulatory action” under Executive Order 12866, 2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), and 3. 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. You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket. List of Subjects in 14 CFR Part 39 Air transportation
Aircraft
Aviation safety
Safety
 The Proposed Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows: PART 39—AIRWORTHINESS DIRECTIVES 1. The authority citation for part 39 continues to read as follows: Authority:
                        49 U.S.C. 106(g), 40113, 44701. § 39.13
  2. The FAA amends § 39.13 by adding the following new AD: **Boeing:**
                                 Docket No. FAA-2007-28283; Directorate Identifier 2006-NM-254-AD. Comments Due Date (a) We must receive comments by September 15, 2008. Affected ADs (b) None. Applicability (c) This AD applies to Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes; certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-25-1544, Revision 1, dated January 16, 2008. Unsafe Condition (d) This AD results from numerous reports of multiple cracks in the frame around the attachment holes of the support bracket of the air conditioning (A/C) outlet extrusion. We are issuing this AD to prevent frame cracking, which, if not corrected, could lead to a severed frame that, combined with cracking of the skin lap splice above stringer 10, could result in rapid decompression of the airplane. Compliance (e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. Service Bulletin Reference (f) The term “service bulletin,” as used in this AD, means the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-25-1544, Revision 1, dated January 16, 2008. Inspections (g) Before the accumulation of 36,000 total flight cycles, or within 72 months after the effective date of this AD, whichever occurs later, except as required by paragraph (i) of this AD: Do a general visual inspection to determine if the support brackets of the A/C outlet extrusions between body station (BS) 360 and BS 907 have two-rivet attachment fittings in accordance with Part 2 of the service bulletin, except at the locations identified in the notes of Step 3.B.1 of Part 1 of the service bulletin. (1) For any support bracket attached with three or more rivets: No further action is required by paragraph (g) of this AD. (2) For any subject support bracket having a two-rivet attachment fitting: Before the accumulation of 36,000 total flight cycles, or within 72 months after the effective date of this AD, whichever occurs later, except as required by paragraph (i) of this AD, do medium- and high-frequency eddy current inspections for cracking of the frame around the attachment holes of the support bracket, in accordance with Part 2 of the service bulletin. If any cracking is discovered, before further flight, repair the cracking in accordance with Part 3 of the service bulletin. Modification (h) Except as required by paragraph (i) of this AD: Before the accumulation of 36,000 total flight cycles, or within 72 months after the effective date of this AD, whichever occurs later, replace the support fittings of all A/C outlet extrusions between BS 360 and BS 907 with new, improved support fittings, in accordance with Part 4 of the service bulletin. Compliance Time for Certain Airplanes (i) For airplanes on which Boeing Business Jet (BBJ) lower cabin altitude modification is incorporated in accordance with Supplemental Type Certificate ST01697SE: Before the accumulation of 18,000 total flight cycles, or within 72 months after the effective date of this AD, whichever occurs later, do the actions specified in paragraphs (g) and (h) of this AD. Actions Accomplished According to Previous Issue of Service Bulletin (j) Actions accomplished before the effective date of this AD according to Boeing Special Attention Service Bulletin 737-25-1544, dated October 4, 2006, are considered acceptable for compliance with the corresponding actions specified in this AD. Alternative Methods of Compliance (AMOCs) (k)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, ATTN: Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-3356, telephone (425) 917-6447, fax (425) 917-6590, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19. (2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO. (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 an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who 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.
 Issued in Renton, Washington, on August 7, 2008. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service.


[FR Doc. E8-19149 Filed 8-18-08; 8:45 am] BILLING CODE 4910-13-P