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Proposed Rule

Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 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), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD would require repetitive inspections for cracks in the fuselage skin, doubler, bearstrap, and frames surrounding the main, forward, and aft cargo doors; and repair of any cracking. This proposed AD also would require inspections of certain existing repairs for cracking, and related corrective action if cracking is found. This proposed AD is prompted by reports of multiple fatigue cracks in the fuselage skin and bonded skin doubler, bearstrap, and doorway frames surrounding the forward and aft cargo doors. We are proposing this AD to find and fix fatigue cracking in the fuselage skin, doubler, bearstrap, and frames, which could result in reduced structural integrity of the frames, possible loss of a cargo door, and consequent rapid decompression of the fuselage.

DATES:

We must receive comments on this proposed AD by October 22, 2004.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

  • DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
  • Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
  • Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, Washington, DC 20590.
  • By fax: (202) 493-2251.
  • Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

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

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., room PL-401, on the plaza level of the Nassif Building, Washington, DC.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Technical information: Howard Hall, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6430; fax (425) 917-6590.

Plain language information: Marcia Walters, marcia.walters@faa.gov.

End Further Info End Preamble Start Supplemental Information

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

The FAA has implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, new AD actions are posted on DMS and assigned a docket number. We track each action and assign a corresponding directorate identifier. The DMS AD docket number is in the form “Docket No. FAA-2004-99999.” The Transport Airplane Directorate identifier is in the form “Directorate Identifier 2004-NM-999-AD.” Each DMS AD docket also lists the directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes.

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2004-19003; Directorate Identifier 2003-NM-245-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments submitted by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that website, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov.

We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at http://www.faa.gov/​language and http://www.plainlanguage.gov.

Examining the Docket

You can examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the DMS receives them.

Background

The FAA previously issued related rulemaking applicable to certain Boeing Model 737 series airplanes, as follows:

AD 88-11-12, amendment 39-5890 (53 FR 18077, May 20, 1988). That AD requires structural inspection of the forward lower cargo doorway frames, and repair if necessary. That AD also requires replacement of certain repaired parts previously installed.

AD 93-14-10, amendment 39-8634 (58 FR 43547, August 17, 1993). That AD requires structural inspections to detect cracks of the forward and aft body frames adjacent to the aft lower cargo door and repair of cracked parts, and provides an optional modification. That AD also requires certain repetitive inspections to continue after installation of the optional modification.

FAA's Determination Since Issuance of AD 88-11-12 and AD 93-14-10

Since we issued those ADs, we have received reports of multiple fatigue cracks in the fuselage skin and bonded skin doubler, bearstrap, and doorway frames surrounding the forward and aft cargo doors on certain Boeing Model Start Printed Page 54059737 series airplanes. Several cracks have also been found in the fuselage skin/doubler and bearstrap of the upper corners of the main cargo door. Additionally, during structural inspections, cracks were found in the bearstrap under the fuselage frame flanges at the edges of the forward cargo door. In two cases, cracks were found in the fuselage frames of the aft cargo door where steel repair doublers had been installed using the requirements of AD 93-14-10. In another case, cracks were found in the unreinforced area above the aluminum repair doubler, which had also been installed using the requirements of AD 93-14-10. A recent inspection done on an airplane having 73,080 total flight cycles revealed cracks in the forward fuselage frame and adjacent skin/doubler and bearstrap of the forward cargo door. Such fatigue cracking, if not found and fixed, could result in reduced structural integrity of the frames, possible loss of a cargo door, and consequent rapid decompression of the fuselage.

Explanation of Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-53A1228, dated July 10, 2003, which describes procedures for repetitive detailed, general visual, and high and low frequency eddy current inspections for cracks in the fuselage skin, doubler, bearstrap, and frames surrounding the main, forward, and aft cargo doors, and repair of any crack found. The service bulletin also describes procedures for repetitive inspections for cracks in certain existing repairs in the subject areas, and related corrective action.

The corrective action includes alternative inspections or replacement of the repaired component, depending on the cracking damage found. The service bulletin recommends that operators contact Boeing for certain repair instructions. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

This service bulletin recommends compliance times at the following approximate intervals:

1. For the detailed and general inspections of the forward and aft cargo door cutouts, the inspection threshold is before the accumulation of 50,000 total flight cycles or within 4,000 flight cycles after release of the service bulletin, whichever is later. The inspections are repeated at intervals ranging from 4,000 flight cycles to 12,000 flight cycles.

2. For the detailed and high frequency eddy current (HFEC) inspections of the main cargo door cutout, the inspection threshold is before the accumulation of 20,000 total flight cycles or within 4,000 flight cycles after release of the service bulletin, whichever is later. The inspections are repeated at intervals not to exceed 12,000 flight cycles.

3. For the detailed and HFEC inspections of the forward cargo doorway frame, the inspection threshold is before the accumulation of 20,000 total flight cycles or within 4,000 flight cycles after release of the service bulletin, whichever is later. The inspections are repeated at intervals not to exceed 4,000 flight cycles.

4. For the general visual, HFEC and low frequency eddy current inspections of the aft cargo doorway frame, the inspection threshold ranges between 20,000 and 40,000 total flight cycles or within 4,000 flight cycles after release of the service bulletin, whichever is later. The inspections are repeated at intervals not to exceed 4,000 flight cycles.

5. If the frame is replaced, the inspection threshold starts from the time the frame was replaced. If the frame is repaired, the inspection threshold starts from the time the repair was installed, or the total airplane cycles if it is unknown when the repair was installed.

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. The proposed AD would require you to use the service information described previously to perform the actions, except as discussed under “Differences Between the Proposed AD and Service Bulletin.''

Differences Between Proposed AD and Service Bulletin

The service bulletin specifies compliance times relative to the date of the service bulletin; however, this proposed AD would require compliance within the thresholds specified in paragraph 1.E., “Compliance” of the service bulletin, after the effective date of the AD.

The service bulletin recommends reporting any discrepancies to the manufacturer; however, this proposed AD does not include that requirement.

Although the service bulletin specifies that operators may contact the manufacturer for disposition of certain repair conditions, this proposed AD would require operators to repair those conditions using a method approved by the Manager of the Seattle Aircraft Certification Office of the FAA, or using data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Costs of Compliance

There are about 3,132 airplanes of the affected design in the worldwide fleet. We estimate that 870 airplanes of U.S. registry would be affected by this proposed AD. We provide the following cost estimates to comply with this proposed AD, per inspection cycle:

GroupWork hoursHourly labor ratePartsCost per airplane
124$65$0$1,560
2 and 4286501,820
3 and 5306501,950
6 and 7286501,820

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. Start Printed Page 54060

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD. 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:

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.

End Authority
[Amended]

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

Boeing: Docket No. FAA-2004-19003; Directorate Identifier 2003-NM-245-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by October 22, 2004.

Affected ADs

(b) None.

Applicability

(c) This AD applies to all Model 737-100, -200, -200C, -300, -400, and -500 series airplanes; certificated in any category.

Unsafe Condition

(d) This AD was prompted by reports of multiple fatigue cracks in the fuselage skin and bonded skin doubler, bearstrap, and doorway frames surrounding the forward and aft cargo doors. We are issuing this AD to find and fix fatigue cracking in the fuselage skin, doubler, bearstrap, and frames, which could result in reduced structural integrity of the frames, possible loss of a cargo door, and consequent rapid decompression of the fuselage.

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.

Initial and Repetitive Inspections/Corrective Action

(f) Do the applicable detailed, general visual, and low and high frequency eddy current inspections for cracks in the fuselage skin, doubler, bearstrap, and frames surrounding the main, forward, and aft cargo doors, and for cracks in existing repairs, as specified in Tables 1, 2, and 3, as applicable, of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1228, dated July 10, 2003. Do the inspections at the initial compliance times listed in Tables 1, 2, and 3, as applicable, of paragraph 1.E., “Compliance,” of the service bulletin; except, where the service bulletin specifies a compliance time after the service bulletin date, this AD requires compliance within the specified compliance time after the effective date of this AD. Do the inspections in accordance with the Accomplishment Instructions of the service bulletin. Repeat the inspections within the repetitive inspection intervals listed in Tables 1, 2, and 3 of paragraph 1.E., “Compliance,” of the service bulletin.

(g) If any crack is found during any inspection: Repair before further flight in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1228, dated July 10, 2003. Where the service bulletin specifies contacting the manufacturer for disposition of certain repair conditions, repair before further flight in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved, the approval must specifically refer to this AD.

No Reporting Required

(h) Although the service bulletin referenced in this AD recommends reporting any discrepancies to the manufacturer, this AD does not include that requirement.

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) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the approval must specifically refer to this AD.

Start Signature

Issued in Renton, Washington, on August 26, 2004.

Kevin M. Mullin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 04-20209 Filed 9-3-04; 8:45 am]

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