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Proposed Rule

Airworthiness Directives; Boeing Model 777 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

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Start Preamble

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 777 series airplanes. This proposal would require modification of the supports for the fuel quantity indicator system (FQIS) wire bundles. This action is necessary to prevent chafing of the FQIS wiring on surrounding structures and systems, which could result in exposure of the bare conductor in close proximity to structures or other electrically conductive return paths and a consequent possibility of electrical arcing and explosion in the fuel tank in the event of an additional wiring failure outside the fuel tank. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by September 10, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-387-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. 2000-NM-387-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 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, 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.

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FOR FURTHER INFORMATION CONTACT:

Ed Hormel, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2681; fax (425) 227-1181.

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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 2000-NM-387-AD.” The postcard will be date stamped and returned to the commenter.

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. 2000-NM-387-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

As a result of a 747-100 accident investigation, the FAA conducted an inspection of the fuel quantity indicator system (FQIS) wiring in a 777-300 center fuel tank (CFT). This inspection identified several potential FQIS wire chafing concerns. Boeing 777-200 airplanes with increased capacity CFTs share the same CFT design and potential wire chafing concerns as the 777-300 airplanes. FQIS wiring on 777-200 and -300 airplanes, which is routed through penetrations in the CFT spanwise beams and side body ribs, has inadequate clearance, excessive slack, and is unprotected from chafing and damage. Also, FQIS wiring secured by P-clamps mounted on flat bracket plates is exposed to chafing on the bracket plate edges and airplane structure. Fuel sloshing, vibration, and normal maintenance activity within the fuel tanks over the lifetime of the airplane increases the risk of chafing and damage to wire that is inadequately secured and protected. Chafed FQIS wiring, with bare conductor exposed, and in close proximity to structures or other electrically conductive return paths, is a potential ignition source when combined with certain FQIS wiring or component failures. This condition, if not corrected, could result in electrical arcing and explosion in the fuel tank.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Special Attention Service Bulletin 777-28-0012, dated September 2, 1999 (for Model 777-200 series airplanes), which describes procedures for replacement, with new brackets and seals, of the wiring support brackets for the FQIS wire bundles at the structural penetration points where the wire bundles enter the CFT.

The FAA has reviewed and approved Boeing Special Attention Service Bulletin 777-28-0016, dated April 27, 2000 (for Model 777-200 and -300 series airplanes), which describes procedures for modification of the FQIS wiring in the CFT by increasing the separation between wire and surrounding structures and systems, and by controlling the wire slack at clamping locations. The modification involves installing spacers on the FQIS wiring support brackets and standoffs, installing a clamp next to the grommet at each tank unit, and replacing the clamp filler O-rings.

The FAA has also reviewed and approved Boeing Special Attention Service Bulletin 777-28-0021, dated April 27, 2000 (also for Model 777-200 and -300 series airplanes), which describes procedures for modification of the FQIS wiring in the main fuel tanks, also by increasing the separation between wire and surrounding structures and systems and by controlling the wire slack at clamping locations. The modification involves installing spacers on the FQIS wiring support brackets and standoffs, installing a clamp next to the grommet at each tank unit, and replacing the clamp filler O-rings.

Accomplishment of the actions specified in each of the above-referenced service bulletins 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 bulletins described previously, except as discussed below. The proposed AD also would require that operators report results of inspection findings to the manufacturer.

Differences Between Proposed Rule and Service Bulletins

Operators should note that, although the service bulletins recommend accomplishing the modifications “at a convenient maintenance opportunity when manpower and facilities are available,” the FAA has determined that such an imprecise compliance time would not address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the modifications. In light of all of these factors, the FAA finds a compliance time of 24 months for completing the required actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Operators should also note that, although the service bulletins do not give specific instructions for the disposition of any damaged wire encountered during the modifications, this AD would require that any damaged wire (i.e., chafed wire, or wire with exposed conductor, broken insulation, conductor, or shielding) must be replaced per the Boeing Standard Wiring Practices Manual D6-54446, Chapter 20, Section 10, Subject 11 (20-10-11), dated August 1, 1996, and any Start Printed Page 38590damage reported to the Boeing Company.

Cost Impact

There are approximately 266 airplanes of the affected design in the worldwide fleet. The FAA estimates that 75 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately the number of work hours per airplane displayed in the table below to accomplish the proposed modifications, and that the average labor rate is $60 per work hour. Required parts costs are also listed in the table below:

Estimated Cost Impact

Boeing service bulletinNumber of work hours per airplaneParts cost per airplaneEstimated cost per airplaneNumber of U.S. airplanes affected
777-28-001238$628$2,90823
777-28-0016 (Group 1)434903,07018
777-28-0016 (Group 2)488393,71957
777-28-0021 (Work Package 1)301,0582,85875
777-28-0021 (Work Package 2)321,0582,97875

Service Bulletins 777-28-0012 and 777-28-0016 both address CFT wiring improvements and require CFT entry. Operators should note that concurrent incorporation of these two service bulletins would minimize tank entries and would be a cost saving (33 work hours per airplane) to the operators because they would need to de-fuel, access, and close access to the CFT only once.

The cost impact figures discussed in the above table are 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. The figures in the table above do not include incidental costs, such as planning time, or time necessitated by other administrative actions.

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.

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List of Subjects in 14 CFR Part 39

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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:

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PART 39—AIRWORTHINESS DIRECTIVES

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

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

End Authority
[Amended]

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

Boeing: Docket 2000-NM-387-AD.

Applicability: Model 777 series airplanes, certificated in any category, line numbers 1 through 266, inclusive.

Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent chafing of the fuel quantity indicator system (FQIS) wiring on surrounding structures and systems, which could result in exposure of the bare conductor in close proximity to structures or other electrically conductive return paths and a consequent possibility of electrical arcing and explosion in the fuel tank in the event of an additional wiring failure outside the fuel tank, accomplish the following:

(a) Within 24 months after the effective date of this AD, complete the actions required by paragraphs (a)(1), (a)(2), and (a)(3) of this AD, as applicable.

Modification of Model 777-200 Center Fuel Tank Wiring

(1) For Model 777-200 series airplanes identified in Boeing Special Attention Service Bulletin 777-28-0012, dated September 2, 1999, modify the FQIS wire bundles (including removing the FQIS wire bundle support brackets at each spanwise beam penetration and replacing them with seals; removing the FQIS wire bundle support brackets from the side of the body rib; installing a grommet in the penetration hole; and replacing the bracket with two new brackets) in accordance with the Accomplishment Instructions of the service bulletin.

Modification of Model 777-200 and -300 Center Fuel Tank Wiring

(2) For Model 777-200 and -300 series airplanes identified in Boeing Special Attention Service Bulletin 777-28-0016, dated April 27, 2000, modify the supports for the FQIS wire bundles in the center fuel tank (including installing spacers on the FQIS wiring support brackets and standoffs; installing a clamp next to the grommet at each tank unit; and replacing the clamp filler O-rings), in accordance with the Accomplishment Instructions of that service bulletin.

Modification of Model 777-200 and -300 Main Fuel Tank Wiring

(3) For Model 777-200 and -300 series airplanes identified in Boeing Special Attention Service Bulletin 777-28-0021, dated April 27, 2000, modify the FQIS wire bundles in the main fuel tanks (including Start Printed Page 38591installing spacers on the wiring support brackets and standoffs; installing a clamp next to the grommet at each tank unit; and replacing the clamp O-rings), in accordance with the Accomplishment Instructions of that service bulletin.

Replacement and Reporting of Damaged Wiring

(b) If any damaged wiring is found during the performance of the modifications required by paragraph (a)(1), (a)(2), or (a)(3) of this AD, before further flight, replace the damaged wiring with new wiring in accordance with Boeing Standard Wiring Practices Manual D6-54446, Chapter 20, Section 10, Subject 11 (20-10-11), dated August 1, 1996. Submit a report of damaged wire findings to the Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207, at the applicable time specified in paragraph (b)(1) or (b)(2) of this AD. The report must include a description of any discrepancies found, the airplane serial number, and the number of landings and flight hours on the airplane. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.

(1) For airplanes on which the modifications are accomplished after the effective date of this AD: Submit the report within 14 days after performing the applicable modification required by paragraph (a)(1), (a)(2), or (a)(3) of this AD.

(2) For airplanes on which the modifications have been accomplished prior to the effective date of this AD: Submit the report within 14 days after the effective date of this AD.

Alternative Methods of Compliance

(c) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permits

(d) Special flight permits may be issued in accordance with §§ 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Start Signature

Issued in Renton, Washington, on July 19, 2001.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 01-18473 Filed 7-24-01; 8:45 am]

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