Airworthiness directives: Boeing,

[Federal Register: May 3, 2004 (Volume 69, Number 85)]

[Proposed Rules]

[Page 24101-24103]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr03my04-23]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2003-NM-106-AD]

RIN 2120-AA64

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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-600, - 700, -700C, -800, and -900 series airplanes. This proposal would require a general visual inspection for sealant at the interface between the diagonal brace fitting and the aft bulkhead and at the four bolts common to the interface. It would also require applying sealant if none is present or if it is not continuous. This action is necessary to prevent flammable fluid in the upper or rear pylon areas from leaking past unsealed areas and onto a hot engine nozzle, which could result in ignition of the fluid, causing an undetected and uncontrollable fire to spread into the engine struts. This action is intended to address the identified unsafe condition.

DATES: Comments must be received by June 17, 2004.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-106-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must

contain ``Docket No. 2003-NM-106-AD,'' in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Doug Pegors, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6504; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments, as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.

For each issue, state what specific change to the proposed AD is being requested.

Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 2003-NM-106-AD.'' The postcard will be date stamped and returned to the commenter.

[[Page 24102]]

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-106-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports indicating that the fay sealing at the interface between the diagonal brace fitting and aft bulkhead in both engine struts and the wet installation of four bolts common to the interface may not have been completed during production of certain Boeing Model 737-600, -700, -00C, -800, and -900 series airplanes. This area is a flammable leakage zone and requires sealing of all openings that could provide a path to an ignition source. Incomplete sealing, if not corrected, could allow flammable fluid in the upper or rear pylon areas to leak past unsealed areas and onto a hot engine nozzle, which could result in ignition of the fluid, causing an undetected and uncontrollable fire to spread into the engine struts.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Special Attention Service Bulletin 737-54-1039, Revision 1, dated October 10, 2002, which describes procedures for the following actions:

1. A general visual inspection to determine whether the diagonal brace fitting and aft bulkhead has been fay sealed or fillet sealed to the aft bulkhead and to determine whether the four bolts have been wet installed or cap sealed.

2. Application of fillet seal, if the seal is not present or not continuous. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

   Explanation of Requirements of Proposed Rule

   Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously.

   Cost Impact

   There are approximately 946 airplanes of the affected design in the worldwide fleet. The FAA estimates that 436 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 2 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $56,680, or $130 per airplane.

   The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. Manufacturer warranty remedies may be available for labor costs associated with this proposed AD. As a result, the costs attributable to the proposed AD may be less than stated above.

   Regulatory Impact

   The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

   For the reasons discussed above, I certify that 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

   List of Subjects in 14 CFR Part 39

   Air transportation, Aircraft, Aviation safety, Safety.

   The Proposed Amendment

   Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

   PART 39--AIRWORTHINESS DIRECTIVES

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

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

   Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

   Boeing: Docket 2003-NM-106-AD.

   Applicability: Model 737-600, -700, -700C, -800, and -900 series airplanes, line numbers 1 through 946 inclusive; certificated in any category.

   Compliance: Required as indicated, unless accomplished previously.

   To prevent flammable fluid in the upper or rear pylon areas from leaking past unsealed areas and onto a hot engine nozzle, which could result in ignition of the fluid, causing an undetected and uncontrollable fire to spread into the engine struts; accomplish the following:

   Inspection of Sealant

   (a) Within 18 months or 3,500 flight cycles after the effective date of this AD, whichever occurs first: Perform a general visual inspection for sealant at the interface of the diagonal brace fitting and the aft bulkhead and at the four bolts common to the interface, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1039, Revision 1, dated October 10, 2002.

   (1) If the findings of the general visual inspection are as described in paragraphs (a)(1)(i) and (a)(1)(ii) of this AD, then no further action is required by this AD.

   (i) The seal is continuous or there is evidence of fay seal sqeeze out present.

   (ii) The bolts have evidence of sealant squeeze out or a cap seal exists.

   Application of Fillet Seal and Cap Seal

   (2) If the findings of the general visual inspection are as described in paragraphs (a)(2)(i) and/or (a)(2)(ii) of this AD, before further flight: Fillet seal around the interface of the diagonal brace fitting and the aft bulkhead; and/or cap seal the four bolts common to the interface; as applicable; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1039, Revision 1, dated October 10, 2002.

   (i) The seal is not continuous and there is no evidence of fay seal squeeze out present.

   (ii) The bolts do not have evidence of sealant squeeze out and no cap seal exists.

   Credit for Actions Accomplished per Previous Service Bulletin

   (b) Actions accomplished before the effective date of this AD per Boeing Special Attention Service Bulletin 737-54-1039, dated June 13, 2002, are acceptable for compliance with the corresponding actions of paragraph (a) of this AD.

   Alternative Methods of Compliance

   (c) In accordance with 14 CFR 39.19, the Manager, Seattle Aircraft Certification Office

   [[Page 24103]]

   (ACO), FAA, is authorized to approve alternative methods of compliance for this AD.

   Issued in Renton, Washington, on April 21, 2004. Kalene C. Yanamura, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

   [FR Doc. 04-9902 Filed 4-30-04; 8:45 am]

   BILLING CODE 4910-13-P