04-19855. Airworthiness Directives; Boeing Model 737-600, 737-700, 737-700C, 737-800, and 737-900 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-600, 737-700, 737-700C, 737-800, and 737-900 series airplanes, that requires measuring the electrical resistance of the support bracket for the fire extinguisher bottle located in the left main landing gear wheel well to ensure that it does not exceed the maximum allowed resistance; and corrective actions, if necessary. This action is necessary to prevent high electrical resistance in the squib firing circuit, which could result in insufficient electrical current to fire the fire extinguisher bottle squib and discharge the fire extinguishing agent, which could lead to an uncontrolled engine fire. This action is intended to address the identified unsafe condition.

DATES:

Effective October 7, 2004.

The incorporation by reference of a certain publication listed in the regulations is approved by the Director of the Federal Register as of October 7, 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 [phone], 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; telephone [phone]; fax [phone].

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, 737-700, 737-700C, 737-800, and 737-900 series airplanes was published in the Federal Register on December 4, 2003 (68 FR 67812). That action proposed to require measuring the electrical resistance of the support bracket for the fire extinguisher bottle located in the left main landing gear wheel well to ensure that it does not exceed the maximum allowed resistance; and corrective actions, if necessary.

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.

Support for the Proposal

Two commenters, who do not have airplanes affected by the proposed AD, either do not object to or agree with the proposed AD.

Request To Give Credit for Boeing Telex

One commenter, an airplane operator, noted that the actions proposed in the notice of proposed rulemaking (NPRM) are based on Boeing Telex M-7200-02-01401, dated September 9, 2002. The operator states that immediate action based on the telex was necessary due to safety concerns, and it did not wait for Boeing to issue the related service bulletin before taking the necessary actions. The commenter proposes that the telex should be included in the final rule as an acceptable means for compliance with the proposed actions.

We agree with the commenter. We have included Boeing Telex M-7200-02-01401, dated September 9, 2002, in a new paragraph (c) of the final rule to allow credit for accomplishment of the required actions per that telex.

Request To Include New Revision of Service Bulletin

Another commenter, the airplane manufacturer, requests that Boeing Alert Service Bulletin 737-26A1118, Revision 1, dated April 8, 2004, be included as the appropriate source of service information for the final rule. The commenter states that a typographical error in the original release of the service bulletin (dated October 17, 2002) makes it impossible for any correctly configured airplane to pass the continuity test in the work instructions. In addition, as noted in the NPRM, the original release of the service bulletin did not have explicit instructions for reworking the terminal installation if the resistance requirement is not met. The commenter states that, if Revision 1 of the service bulletin is included in the final rule, paragraph (b) (“Additional Rework”) should be deleted, and paragraph (a) should be revised to exclude a reference to paragraph (b).

We partially agree with the commenter's request. In a further engineering review, we determined that there is no typographical error in the original release of the service bulletin that makes it impossible for airplanes to pass the continuity test. However, we have revised the applicability section and paragraphs (a) and (b) of the final rule to include Revision 1 of the service bulletin, which is the most current source of service information for the actions in this AD. We have not deleted paragraph (b), but instead have revised it to allow operators to rework the terminal installation in accordance with either Revision 1 of the service bulletin, or in accordance with a method approved by the FAA, as proposed in the NPRM. The new paragraph (c) of this final rule also allows credit for actions done in accordance with the original issue of the service bulletin.

Request To Revise Wording Regarding Anodize Coating

The same commenter requests that the following sentence in the “Discussion” section of the NPRM be revised: “During manufacture, the anodize coating was not removed properly from the holes in the support bracket into which the ground studs are inserted, thereby increasing the electrical resistance between the studs and the bracket.” The commenter notes that the anodize coating surrounding the hole was also improperly prepared for an electrical bond.

We partially agree with the commenter's request, which provides a more accurate description of the unsafe condition. However, the “Discussion” paragraph is included in an NPRM as a description of the unsafe condition to provide adequate information to the public during the comment period. The “Discussion” paragraph is not included in the final rule. Therefore, we have not changed the information in the final rule, but have provided the commenter's information above for the sake of accuracy.

Conclusion

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact

There are approximately 133 airplanes of the affected design in the worldwide fleet. The FAA estimates that 28 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 $3,640, 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.

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

[Amended]

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

2004-18-02 Boeing: Amendment 39-13779. Docket 2002-NM-327-AD.

Applicability: Model 737-600, 737-700, 737-700C, 737-800, and 737-900 series airplanes, as listed in Boeing Alert Service Bulletin 737-26A1118, Revision 1, dated April 8, 2004; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent high electrical resistance in the squib firing circuit, which could result in insufficient electrical current to fire the fire extinguisher bottle squib and discharge the fire extinguishing agent, which could lead to an uncontrolled engine fire, accomplish the following:

Inspection, Rework, Replacement, Relocation, and Installation

(a) Except as provided by paragraph (b) of this AD: Within 90 days after the effective date of this AD, measure the electrical resistance of the dual ground studs of the support brackets for the fire extinguisher bottle located in the left main landing gear wheel well (including the applicable corrective actions) by accomplishing all actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 737-26A1118, Revision 1, dated April 8, 2004. Do the actions per the service bulletin. Any applicable corrective action must be accomplished prior to further flight.

Additional Rework

(b) If, when accomplishing the bond resistance measurement described in Figure 4 of Boeing Alert Service Bulletin 737-26A1118, Revision 1, dated April 8, 2004, the resistance is found to be greater than 1.0 milliohms (0.001 ohms): Before further flight, do the actions in paragraph (b)(1) or (b)(2) of this AD.

(1) Rework the terminal installation per Figure 4 of the service bulletin.

(2) Rework the terminal installation per a method approved by the Manager, Seattle Aircraft Certification Office, FAA.

Actions Accomplished per Boeing Telex and Previous Issue of Service Bulletin

(c) Actions accomplished before the effective date of this AD per Boeing Telex M-7200-02-01401, dated September 9, 2002; or Boeing Alert Service Bulletin 737-26A1118, dated October 17, 2002; are considered acceptable for compliance with the corresponding action specified in this AD.

Alternative Methods of Compliance

(d) In accordance with 14 CFR 39.19, the Manager, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056, is authorized to approve alternative methods of compliance (AMOCs) for this AD.

Incorporation by Reference

(e) Unless otherwise specified in this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 737-26A1118, Revision 1, dated April 8, 2004. 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 [phone], or go to: http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html.

Effective Date

(f) This amendment becomes effective on October 7, 2004.

Issued in Renton, Washington, on August 20, 2004.

Kevin M. Mullin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.