Federal Aviation Administration (FAA), DOT.
Notice of proposed rulemaking (NPRM).
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This proposed AD would require repetitive detailed, low frequency eddy current, and high frequency eddy current inspections of the webs of the aft pressure bulkhead at body station 1016 for cracks, and corrective action if necessary. This proposed AD is prompted by a report of cracks found, during fatigue testing, at several of the fastener rows in the web lap splices at the dome apex of the aft pressure bulkhead. We are proposing this AD to detect and correct fatigue cracks in the webs of the aft pressure bulkhead, which could result in rapid decompression of the airplane.
We must receive comments on this proposed AD by October 22, 2004.
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 Start Printed Page 54054and 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 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, firstname.lastname@example.org.End Further Info End Preamble Start Supplemental 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.
We invite you to submit any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2004-19022; Directorate Identifier 2004-NM-122-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.
We have received a report that, during fatigue testing, the manufacturer found cracks at several of the fastener rows in the web lap splices at the dome apex of the aft pressure bulkhead on a Boeing 737-800 series airplane. Cracks were found in three of the seven webs. The single rivet located where each of the webs transition up 0.032 inches over the adjacent web causes pull down loading, which leads to cracks at the rivet holes of the web lap splices. This condition, if not detected and corrected, could result in rapid decompression of the airplane.
The web lap splices on certain Model 737-600, -700, -700C, and -900 series airplanes are identical to those on the affected Model 737-800 series airplanes. Therefore, all of these models may be subject to the same unsafe condition.
Relevant Service Information
We have reviewed Boeing Service Bulletin 737-53-1251, dated June 3, 2004. The service bulletin describes procedures for doing repetitive detailed inspections, low frequency eddy current (LFEC) inspections, and high frequency eddy current (HFEC) inspections of the webs of the aft pressure bulkhead at body station 1016 from the aft side at the dome apex for cracks; and contacting the manufacturer for repair instructions if cracks are found. We have determined that accomplishing the actions specified in the service bulletin will 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. Therefore, we are proposing this AD, which would require doing repetitive detailed inspections, LFEC inspections, and HFEC inspections of the webs of the aft pressure bulkhead at body station 1016 from the aft side at the dome apex for cracks, and corrective action if necessary. The corrective action includes repairing any crack found during any inspection in accordance with a method approved by the FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the FAA to make those findings. The proposed AD would require you to use the service information described previously to perform these actions, except as discussed under “Differences Between the Proposed AD and the Service Bulletin.”
Differences Between the Proposed AD and the Service Bulletin
Operators should note that, although the service bulletin does not list a grace period in the compliance times, this proposal adds a grace period to the compliance times. The FAA finds that such a grace period will keep airplanes from being grounded unnecessarily.
Operators should also note that 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 per a method approved by the FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company DER Start Printed Page 54055who has been authorized by the FAA to make those findings.
Costs of Compliance
This proposed AD would affect about 457 airplanes of U.S. registry and 1,166 airplanes worldwide. The proposed actions would take about 8 work hours per airplane, at an average labor rate of $65 per work hour. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $237,640, or $520 per airplane, per inspection cycle.
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. See the ADDRESSES section for a location to examine the regulatory evaluation.Start List of Subjects
List of Subjects in 14 CFR Part 39End 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:
2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):
Boeing: Docket No. FAA-2004-19022; Directorate Identifier 2004-NM-122-AD.
Comments Due Date
(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by October 22, 2004.
(c) This AD applies to Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes, certificated in any category; as listed in Boeing Service Bulletin 737-53-1251, dated June 3, 2004.
(d) This AD was prompted by a report of cracks found, during fatigue testing, at several of the fastener rows in the web lap splices at the dome apex of the aft pressure bulkhead. We are issuing this AD to detect and correct fatigue cracks in the webs of the aft pressure bulkhead, which could result in rapid decompression of the airplane.
(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
(f) Prior to accumulating 26,000 total flight cycles or within 4,000 flight cycles after the effective date of this AD, whichever occurs later: Do a detailed inspection, low frequency eddy current inspection, and high frequency eddy current inspection of the webs of the aft pressure bulkhead at body station 1016 for cracks, in accordance with Boeing Service Bulletin 737-53-1251, dated June 3, 2004. Repeat the inspections thereafter at intervals not to exceed 4,000 flight cycles.
For the purposes of this AD, a detailed inspection is: “An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirror, magnifying lenses, etc., may be necessary. Surface cleaning and elaborate procedures may be required.”
(g) If any crack is found during any inspection required by paragraph (f) of this AD: Before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved, the approval must specifically reference this AD.
Alternative Methods of Compliance (AMOCs)
(h)(1) The Manager, Seattle ACO, FAA, 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 DER 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.
Issued in Renton, Washington, on August 27, 2004.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 04-20212 Filed 9-3-04; 8:45 am]
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