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Proposed Rule

Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 and -900 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

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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.

Start Further Info

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.

End Further Info End Preamble Start Supplemental Information

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. Start Printed 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

ActionWork hoursPartsCost per airplaneFleet cost
General visual inspection1No parts required$80$50,080.
MFEC and HFEC inspectionsBetween 170 and 216No parts requiredBetween $13,600 and $17,280Up to $10,817,280.
Replace support fittingsBetween 258 and 346Between $56,095 and $81,339Between $76,735 and $109,019Up 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: Start Printed Page 48309General 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.

Start List of Subjects

List of Subjects in 14 CFR Part 39

End List of Subjects

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

Start Part

PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Start Authority

Authority: 49 U.S.C. 106(g), 40113, 44701.

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[Amended]

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.

Start Signature

Issued in Renton, Washington, on August 7, 2008.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. E8-19149 Filed 8-18-08; 8:45 am]

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