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Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

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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:

Final rule; request for comments.

SUMMARY:

We are adopting a new airworthiness directive (AD) for all Boeing Model 737-300, -400, and -500 series airplanes. This AD requires repetitive inspections of the downstop assemblies on the main tracks of the No. 2, 3, 4, and 5 slats and the inboard track of the No. 1 and 6 slats to verify if any parts are missing, damaged, or in the wrong order. This AD also requires other specified actions, and related investigative and corrective actions if necessary. This AD results from reports of fuel leaking from a puncture in the slat track housing (referred to as the “slat can”). We are issuing this AD to detect and correct loose or missing parts from the main slat track downstop assemblies, which could puncture the slat can and result in a fuel leak and consequent fire.

DATES:

This AD is effective April 8, 2008.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of April 8, 2008.

We must receive comments on this AD by May 23, 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.

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 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.

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FOR FURTHER INFORMATION CONTACT:

Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6440; fax (425) 917-6590.

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SUPPLEMENTARY INFORMATION;

Discussion

Boeing has notified us that it has received numerous reports of fuel leaking from the slat track housing (referred to as the “slat can”) on Boeing Model 737-300, -400, and -500 series airplanes. In all cases, there were no reports of a fire as a result of the fuel leaks on these airplane models. In some of the reports, the fuel leak was caused by loose or broken parts falling off the downstop assembly into the slat can, which were then subsequently driven into the slat can by the retracting slat track. This condition, if not corrected, could puncture the slat can and result in a fuel leak and consequent fire.

Other Related Rulemaking

On August 28, 2007, we issued emergency AD 2007-18-52, amendment 39-15197, to address the same unsafe condition on all Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. That AD was published in the Federal Register on September 21, 2007 (72 FR 53928). That AD requires repetitive detailed inspections of the slat track downstop assemblies to verify that proper hardware is installed, one-time torquing of the nut and bolt, and corrective actions if necessary. That AD resulted from reports of parts coming off the main slat track downstop assemblies and a resultant fire. That AD was issued to detect and correct loose or missing parts from the main slat track downstop assemblies, which could result in a fuel leak and consequent fire.

Because the main slat track downstop assemblies of Model 737 airplanes are similar in design to those of other Boeing airplane models, we have been working with the manufacturer to evaluate its remaining airplane models to determine if a similar unsafe condition exists on them. As a result, we may consider additional rulemaking as those evaluations are completed.

Relevant Service Information

We reviewed Boeing Alert Service Bulletin 737-57A1301, dated February 5, 2008. The service bulletin describes procedures for doing repetitive detailed inspections of the downstop assemblies on the main tracks of the No. 2, 3, 4, and 5 slats and the inboard track of the No. 1 and 6 slats to verify if any parts are missing, damaged, or in the wrong order. The service bulletin specifies that the downstop assembly may be inspected using a borescope. The service bulletin also describes procedures for doing other specified actions, and doing related investigative and corrective actions if necessary. The other specified actions include a one-time torquing of the nut of the downstop assembly and a detailed inspection of the bolt to verify that the entire chamfered portion of the bolt protrudes beyond the outer surface of the nut. The related investigative action is a detailed inspection of the inside of the slat can for loose parts and damage to the wall of the slat can, which is done if any downstop assembly part is missing or damaged. The corrective actions include the following:

  • Removing any loose downstop assembly part found in the slat can.
  • Replacing any damaged slat can, or contacting Boeing for repair information.
  • Replacing any missing or damaged downstop assembly part with a new or serviceable part.
  • Removing and reinstalling the downstop assembly if any downstop assembly parts are in the wrong order, or if the entire chamfered portion of the bolt does not protrude beyond the outer surface of the nut after it is torqued.

The service bulletin specifies doing the initial inspection within 90 days and repeating the inspection thereafter at intervals not to exceed 4,500 flight Start Printed Page 15398cycles. The service bulletin specifies doing the other specified actions within 90 days. The service bulletin specifies doing the related investigative and corrective actions before further flight after certain findings.

FAA's Determination and Requirements of This AD

We are issuing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the(se) same type design(s). This AD requires accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the AD and Service Bulletin.”

Differences Between the AD and Service Bulletin

For airplanes on which any downstop assembly part is missing or damaged, the service bulletin specifies doing a related investigative action—i.e., a detailed inspection of the inside of the slat can for loose parts and damage to the wall of the slat can. However, this AD allows operators to accomplish a borescope inspection of the inside of the slat can instead of a detailed inspection. We have coordinated this difference with Boeing.

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this AD would require repairing those conditions in one of the following ways:

  • Using a method that we approve; or
  • Using data that meet the certification basis of the airplane, and that have been approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

Clarification of Slat Can Replacement

Paragraph 3.B.5.a.(2) of the Accomplishment Instructions of the service bulletin specifies to either replace any damaged slat can or contact Boeing for repair information if any damaged slat can is found. Paragraph (f)(3) of this AD specifies, in part, that if an operator chooses to replace the damaged slat can instead of contacting Boeing for repair information, the damaged slat can must be replaced with a new slat can having the same part number.

Interim Action

We consider this AD interim action. The manufacturer is currently developing a modification that will address the unsafe condition identified in this AD. Once this modification is developed, approved, and available, we might consider additional rulemaking.

FAA's Justification and Determination of the Effective Date

Loose or missing parts from the main slat track downstop assemblies could puncture the slat can and result in a fuel leak and consequent fire. Because of our requirement to promote safe flight of civil aircraft and thus, the critical need to assure the structural integrity of the main slat track downstop assemblies and the short compliance time involved with this action, this AD must be issued immediately.

Because an unsafe condition exists that requires the immediate adoption of this AD, we find that notice and opportunity for prior public comment hereon are impracticable and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited

This AD is a final rule that involves requirements affecting flight safety, and we did not provide you with notice and an opportunity to provide your comments before it becomes effective. However, we invite you to send any written data, views, or arguments about this AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2008-0303; Directorate Identifier 2008-NM-047-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this AD. We will consider all comments received by the closing date and may amend this 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 AD.

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: 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

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.

For the reasons discussed above, I certify that this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under 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.

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List of Subjects in 14 CFR Part 39

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Adoption of the Amendment

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Accordingly, under the authority delegated to me by the Administrator, the FAA amends

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PART 39—AIRWORTHINESS DIRECTIVES

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

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

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[Amended]
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2. The FAA amends § 39.13 by adding the following new AD:

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2008-06-29 Boeing: Amendment 39-15441. Docket No. FAA-2008-0303; Directorate Identifier 2008-NM-047-AD.

Effective Date

(a) This airworthiness directive (AD) is effective April 8, 2008.

Affected ADs

(b) None. Start Printed Page 15399

Applicability

(c) This AD applies to all Boeing Model 737-300, -400, and -500 series airplanes, certificated in any category.

Unsafe Condition

(d) This AD results from reports of fuel leaking from a puncture in the slat track housing (referred to as “slat can”). We are issuing this AD to detect and correct loose or missing parts from the main slat track downstop assemblies, which could puncture the slat can and result in a fuel leak and consequent fire.

Compliance

(e) Comply with this AD within the compliance times specified, unless already done.

Repetitive Inspections and Corrective Actions

(f) At the applicable time specified in Table 1 of paragraph 1.E. of Boeing Alert Service Bulletin 737-57A1301, dated February 5, 2008, except as provided by paragraph (f)(1) of this AD: Do a detailed inspection or borescope inspection of the downstop assemblies on the main tracks of the No. 2, 3, 4, and 5 slats and the inboard track of the No. 1 and 6 slats to verify if any parts are missing, damaged, or in the wrong order; and do all the other specified, related investigative, and corrective actions as applicable; by accomplishing all of the applicable actions specified in the Accomplishment Instructions of the service bulletin, except as provided by paragraphs (f)(2) and (f)(3) of this AD. Repeat the inspection thereafter at the applicable interval specified in Table 1 of paragraph 1.E. of the service bulletin. Do all applicable related investigative and corrective actions before further flight.

(1) Where the service bulletin specifies counting the compliance time from “* * * the date on the service bulletin,” this AD requires counting the compliance time from the effective date of this AD.

(2) For airplanes on which any downstop assembly part is missing or damaged, a borescope inspection of the inside of the slat can for loose parts and damage to the wall of the slat can may be accomplished in lieu of the detailed inspection of the inside of the slat can that is specified in the service bulletin.

(3) If any damaged slat can is found during any inspection required by this AD: Before further flight, either replace the slat can with a new slat can having the same part number or repair the slat can using a method approved in accordance with the procedures specified in paragraph (g) of this AD.

Alternative Methods of Compliance (AMOCs)

(g)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, Attn: Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6440; fax (425) 917-6590; has the authority to approve AMOCs for this AD, if requested using 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.

Material Incorporated by Reference

(h) You must use Boeing Alert Service Bulletin 737-57A1301, dated February 5, 2008, to do the actions required by this AD, unless the AD specifies otherwise.

(1) The Director of the Federal Register approved the incorporation by reference of this service information under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

(3) You may review copies of the service information incorporated by reference at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington; or 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/​code_​of_​federal_​regulations/​ibr_​locations.html.

Start Signature

Issued in Renton, Washington, on March 11, 2008.

Stephen P. Boyd,

Assistant Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. E8-5702 Filed 3-21-08; 8:45 am]

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