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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. 2003-NM-106-AD; Amendment 39-13855; AD 2004-22-27]
          - RIN 2120-AA64

# AGENCY:

Federal Aviation Administration, DOT.

# ACTION:

Final rule.

# SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes, that requires 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 also requires 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:

Effective December 14, 2004.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of December 14, 2004.

# ADDRESSES:

                        The service information referenced in this AD may be obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 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*.                    

# 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:

                    A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes was published in the                     **Federal Register**                     on May 3, 2004 (69 FR 24101). That action proposed to 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 also proposed to require applying sealant if none is present or if it is not continuous.                

## Comments

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

## Request To Extend Compliance Time

One commenter requests that the FAA extend the compliance time for the general visual inspection from 18 months or 3,500 flight cycles, whichever occurs first, to 24 months or 4,500 flight cycles, whichever occurs first. The commenter states that access is common for the proposed inspection and Boeing Maintenance Planning Document (MPD) tasks 54-040-1 through 54-050-02, dated February 10, 2004, and that it would be more cost efficient if the commenter could perform the inspection and MPD tasks during the same maintenance visit, every 24 months.

                    We do not agree with the request to extend the compliance time. The commenter provided no justification for the change other than for the convenience of its maintenance program. In developing an appropriate compliance time for this action, we considered the recommendation of the manufacturer, urgency associated with the subject unsafe condition, and the practical aspect of accomplishing the required inspection within a period of time that corresponds to the normal scheduled maintenance for most affected operators. However, under the provisions of paragraph (c) of the final                           ( print page 64853)                        rule, we may approve requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety.                

## Conclusion

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

## Clarification of Changes to the Final Rule

We have revised paragraph (a)(2) of the final rule and added new paragraph (a)(3) to eliminate any possible ambiguity created by use of the term “and/or” in the proposed AD.

## 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 will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required actions, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the 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 requirements of this AD action, and that no operator would accomplish those actions in the future if this 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 AD. As a result, the costs attributable to this AD may be less than stated above.

## Regulatory Impact

The regulations adopted herein 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.

                    For the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption                     **ADDRESSES**                    .                

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Incorporation by reference
      - Safety

## Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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.

§ 39.13 

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

**2004-22-27 Boeing:**                             Amendment 39-13855. 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

(2) The seal is not continuous and there is no evidence of fay seal squeeze out present, before further flight, fillet seal around the interface of the diagonal brace fitting and the aft bulkhead, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1039, Revision 1, dated October 10, 2002.

## Application of Cap Seal

(3) If the bolts do not have evidence of sealant squeeze out and no cap seal exists, before further flight, cap seal 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.

## 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 (AMOC)

(c) In accordance with 14 CFR 39.19, the Manager, Seattle Aircraft Certification Office, FAA, is authorized to approve AMOCs for this AD.

## Incorporation by Reference

                            (d) Unless otherwise specified in this AD, the actions shall be done in accordance with Boeing Special Attention Service Bulletin 737-54-1039, Revision 1, dated October 10, 2002. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected 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*.                        

## Effective Date

(e) This amendment becomes effective on December 14, 2004.

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

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 04-24626 Filed 11-8-04; 8:45 am]

BILLING CODE 4910-13-P