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

Summary:

The FAA is revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. The original NPRM would have required sealing the fasteners on the front and rear spars inside the main fuel tank and on the lower panel of the center fuel tank, inspecting the wire bundle support installation in the equipment cooling system bays to identify the type of clamp installed and determine whether the Teflon sleeve is installed, and doing related corrective actions if necessary. The original NPRM resulted from a design review of the fuel tank systems. This action revises the compliance time for the corrective actions specified in the original NPRM. We are proposing this supplemental NPRM to prevent arcing at certain fuel tank fasteners in the event of a lightning strike or fault current event, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

Table of Contents

Table of Figures

Dates:

We must receive comments on this supplemental NPRM by January 28, 2008.

Addresses:

You may send comments by any of the following methods:

Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.

Fax:202-493-2251.

Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.

Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

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

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone 800-647-5527) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

For further information contact:

Kathrine Rask, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6505; fax (425) 917-6590.

Supplementary information:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2007-28348; Directorate Identifier 2007-NM-060-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

We proposed to amend 14 CFR part 39 with a notice of proposed rulemaking (NPRM) for an AD (the “original NPRM”) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. The original NPRM was published in the Federal Register on June 5, 2007 (72 FR 30996). The original NPRM proposed to require sealing the fasteners on the front and rear spars inside the main fuel tank and on the lower panel of the center fuel tank, inspecting the wire bundle support installation in the equipment cooling system bays to identify the type of clamp installed and determine whether the Teflon sleeve is installed, and doing related corrective actions if necessary.

Actions Since Original NPRM Was Issued

Since we issued the original NPRM, we have become aware that the compliance time for the corrective actions in the referenced service bulletin, Boeing Alert Service Bulletin 737-57A1279, dated January 24, 2007, is specified incorrectly. Paragraph 1.E. of the service bulletin specifies replacing incorrect clamps within 5 years of the release date on the service bulletin. Paragraph (g) of this supplemental NPRM would require this action before further flight after discovery of the incorrect clamps.

Comments

We provided the public the opportunity to participate in the development of this AD. We have considered the comments received.

Support for the NPRM

Boeing concurs with the contents of the NPRM.

Request To Revise Compliance Time

Air Transport Association (ATA), on behalf of its member American Airlines (AAL), requests that we revise the proposed compliance time for the sealant application and inspection from 60 months to 72 months. AAL states that its current maintenance schedule might not allow for accomplishment of the proposed actions on all of itsaffected airplanes within 60 months. AAL would therefore incur significant costs associated with special maintenance visits to meet the compliance time.

We disagree with the request. In developing an appropriate compliance time for this action, we considered the safety implications, the manufacturer's recommendations, and normal maintenance schedules for most affected operators for the timely accomplishment of the required actions. We have determined that the compliance time, as proposed, represents the maximum interval of time allowable for the affected airplanes to continue to safely operate before the required actions are done. We have not changed the original NPRM regarding this issue. However, according to the provisions of paragraph (h) of this supplemental NPRM, we may approve requests to adjust the compliance time if the request includes data that prove that a different compliance time would provide an acceptable level of safety.

Request To Approve Alternative Part Numbers and Other Specifications

ATA and AAL request that we revise the original NPRM to allow alternatives to parts and other specifications identified in Alert Service Bulletin 737-57A1279. AAL states that including an option to choose among multiple vendors or specifications should reduce any part availability issues for the operator.

We disagree with the request. We understand that, when developing service information, Boeing tries to identify alternative parts and other specifications to give operators as many options as possible. We review those options when we approve the service information. AAL did not make any specific proposals for alternative specifications. We need to approve the use of all such substitutions to ensure that the unsafe condition is adequately addressed. We have not changed this supplemental NPRM regarding this issue. However, paragraph (h) of this supplemental NPRM provides operators the opportunity to request alternative methods of compliance if data are presented that prove that the proposed options will provide an acceptable level of safety.

Request To Revise Cost Estimate

ATA and AAL request that we revise the proposed cost estimate to reflect additional work that might be necessary to comply with the proposed AD. First, AAL states that the original NPRM provides no costs for open/close actions, although the proposed actions might not always be accomplished at the same time as other maintenance work that involves similar open/close actions (removing A/C packs, opening wing fuel tanks, and deploying Krueger Flaps). To ensure timely compliance, AAL suggests that an additional 42.5 hours per airplane might be necessary for open/close actions. Second, AAL states that the NPRM provides no costs for clamp/sleeve replacement, although an additional 58 hours per airplane might be necessary for this action (depending on the inspection results).

We disagree with the request to revise the cost estimate. 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, or the costs of “on-condition” actions such as repairs (that is, actions needed to correct an unsafe condition). We have not changed the supplemental NPRM regarding this issue.

FAA's Determination and Proposed Requirements of the Supplemental NPRM

The compliance time for one of the corrective actions discussed above expands the scope of the original NPRM; therefore, we have determined that it is necessary to reopen the comment period to provide additional opportunity for public comment on this supplemental NPRM.

Differences Between the Supplemental NPRM and the Service Bulletin

As stated previously, where the service bulletin specifies a compliance time for replacing incorrect clamps within 5 years after the date on the service bulletin, this supplemental NPRM would require this action before further flight after discovery of the incorrect clamps.

Costs of Compliance

There are about 1,754 airplanes of the affected design in the worldwide fleet; of these, 645 airplanes are U.S. registered. The following table provides the estimated costs for U.S. operators to comply with this supplemental NPRM, at an average hourly labor rate of $80.

Estimated Costs
ActionGroupWork hoursAveragehourly labor rate Cost perairplane Number of U.S.-registered airplanesFleet cost
Sealant application 1 62 $80 $4,960 586 $2,906,560
2 28 80 2,240 44 98,560
3 28 80 2,240 15 33,600
Inspection 1 3 80 240 586 140,640
2 3 80 240 44 10,560
3 2 80 160 15 2,400

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

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, oron 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 supplemental NPRM and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of subjects in 14 cfr part 39

Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-28348; Directorate Identifier 2007-NM-060-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 28, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Model 737-600, -700, -700C, -800 and -900 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 737-57A1279, dated January 24, 2007.

Unsafe Condition

(d) This AD results from a design review of the fuel tank systems. We are issuing this AD to prevent arcing at certain fuel tank fasteners in the event of a lightning strike or fault current event, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

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.

Fastener Sealant

(f) Within 60 months after the effective date of this AD: Seal the fasteners on the front and rear spars inside the main fuel tank and on the lower panel of the center fuel tank, as applicable, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-57A1279, dated January 24, 2007.

Inspection

(g) Within 60 months after the effective date of this AD: Perform a general visual inspection of the wire bundle support installation in the equipment cooling system bays to identify the type of clamp installed, and determine whether the Teflon sleeve is installed. Do these actions in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-57A1279, dated January 24, 2007. Do all applicable corrective actions before further flight in accordance with the service bulletin.

Alternative Methods of Compliance (AMOCs)

(h)(1) The Manager, Seattle Aircraft Certification Office (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) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.

Issued in Renton, Washington, on December 20, 2007. Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

References

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