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Proposed Rule

Airworthiness Directives; Boeing Model 737-300 and -400 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.

Start Preamble

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-300 and -400 series airplanes. This proposed AD would require testing and inspecting a certain web panel of the main wheel well pressure deck to determine the material type and thickness; and related investigative and corrective actions if necessary. This proposed AD results from several reports indicating that cracks ranging from 0.8 to 8.0 inches long were found on a certain web panel of the main wheel well pressure deck. We are proposing this AD to prevent fatigue cracking in the web panel of the main wheel well pressure deck, which could result in venting and consequent rapid decompression of the airplane.

DATES:

We must receive comments on this proposed AD by February 25, 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 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.

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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-2007-0395; Directorate Identifier 2007-NM-157-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 have received several reports indicating that cracks ranging from 0.8 to 8.0 inches long were found on a certain web panel of the main wheel well pressure deck. These cracks were found on certain Boeing Model 737-300 and -400 series airplanes. Boeing analyzed pieces of the cracked web sections on three airplanes and found that in each case, the webs were made of the wrong material type and thickness. According to design, the web should be 0.050 inch thick 2024-T42 bare sheet. The webs were found to be 7075 Clad material, with thicknesses of 0.040 inches nominal. (Webs made from this material and thickness are more likely to crack.) The flight cycles on the airplanes when the cracking was found ranged from 13,332 to 22,849 total flight cycles. Cracking in the web panel, if not corrected, could result in venting and consequent rapid decompression of the airplane. Start Printed Page 1847

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-57-1289, dated June 13, 2007. The service bulletin describes procedures for testing and inspecting a certain web panel of the main wheel well pressure deck to determine if the material type and thickness are discrepant, and performing related investigative and corrective actions if necessary.

The testing and inspection procedures include performing either a one-time chemical spot test or a one-time evaluation with a Scanning Electron Microscope (SEM) of the web material of the main wheel well pressure deck to determine the type of web material, and performing a one-time ultrasonic inspection to determine the material thickness. For airplanes on which the web thickness is discrepant (the thickness is less than 0.047 inches, or if the web material is 7000 series aluminum), the procedures for the related investigative and corrective actions include the following:

  • For airplanes on which the web thickness is less than 0.037 inches, replace the web panel before further flight.
  • For airplanes on which the web thickness is greater than or equal to 0.037 inches and less than 0.047 inches, or the web material is 7000 series aluminum: Perform a detailed inspection for any crack and a general visual inspection for any corrosion before further flight. If no crack or corrosion is found, repeat the inspections until the web panel is replaced. Accomplishing the replacement eliminates the need for the repetitive inspections.

If any crack or corrosion is found during any inspection, replace the web panel or contact Boeing for repair instructions and repair before further flight.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Difference Between the Proposed AD and Service Information.”

Difference Between the Proposed AD and Service Information

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed 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.

Costs of Compliance

There are about 31 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 1 airplane of U.S. registry. The proposed tests and inspections would take about 3 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the proposed AD for this U.S. operator is $240.

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

We have 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 that the 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

Start List of Subjects

List of Subjects in 14 CFR Part 39

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The Proposed Amendment

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

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PART 39—AIRWORTHINESS DIRECTIVES

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]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-0395; Directorate Identifier 2007-NM-157-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by February 25, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-300 and -400 series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-57-1289, dated June 13, 2007.

Unsafe Condition

(d) This AD results from several reports indicating that cracks ranging from 0.8 to 8.0 inches long were found on a certain web panel of the main wheel well pressure deck. We are issuing this AD to prevent fatigue cracking in the web panel of the main wheel well pressure deck, which could result in venting and consequent 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. Start Printed Page 1848

Testing/Inspecting/Investigative and Corrective Actions

(f) Within 6 months after the effective date of this AD: Do a test of the web panel of the main wheel well pressure deck to determine the material type, and do an ultrasonic inspection to determine material thickness, by doing all the applicable actions specified in the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-57-1289, dated June 13, 2007.

(g) For airplanes on which the web thickness or material is found to be discrepant during the test and inspection required by paragraph (f) of this AD, accomplish the applicable actions specified in paragraphs (g)(1) and (g)(2) of this AD at the time specified, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-57-1289, dated June 13, 2007.

(1) Do all applicable related investigative and corrective actions (including detailed and general visual inspections) before further flight, by doing all the actions specified in the Accomplishment Instructions of the service bulletin; except as provided by paragraph (h) of this AD. Repeat the inspections thereafter at intervals not to exceed 1,000 flight cycles until paragraph (g)(2) of this AD has been done.

(2) Within 30 months or 6,000 flight cycles after accomplishing the actions required by paragraph (g)(1) of this AD, whichever is later, replace the web panel in accordance with the Accomplishment Instructions of the service bulletin. Doing this replacement ends the repetitive inspections required by paragraph (g)(1) of this AD.

Corrective Actions

(h) If any crack or corrosion is found during any inspection required by paragraph (g)(1) of this AD, and Boeing Special Attention Service Bulletin 737-57-1289, dated June 13, 2007, specifies to contact Boeing for repair instructions: Before further flight, repair according to a method approved in accordance with the procedures specified in paragraph (i) of this AD.

Alternative Methods of Compliance (AMOCs)

(i)(1) The Manager, Seattle ACO, 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 December 21, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. E8-251 Filed 1-9-08; 8:45 am]

BILLING CODE 4910-13-P