Airworthiness Directives; Boeing Model 757 Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 757 airplanes. This proposed AD would require inspections of certain wire bundles in the left and right engine-to-wing aft fairings for discrepancies, and other specified and corrective actions. This proposed AD is prompted by a report indicating that a circuit breaker for the fuel shutoff valve tripped due to a wire that chafed against the structure in the flammable leakage zone of the aft fairing, causing a short circuit. We are proposing this AD to prevent chafing between the wire bundle and the structure of the aft fairing, which could result in electrical arcing and subsequent ignition of flammable vapors and possible uncontrollable fire.

DATES:

We must receive comments on this proposed AD by December 20, 2004.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, Washington, DC 20590.
• By fax: (202) 493-2251.
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

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

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov , or at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., room PL-401, on the plaza level of the Nassif Building, Washington, DC.

FOR FURTHER INFORMATION CONTACT:

Technical information: Thomas Thorson, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6508; fax (425) 917-6590.

Plain language information: Marcia Walters, marcia.walters@faa.gov.

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

The FAA has implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, new AD actions are posted on DMS and assigned a docket number. We track each action and assign a corresponding directorate identifier. The DMS AD docket number is in the form “Docket No. FAA-2004-99999.” The Transport Airplane Directorate identifier is in the form “Directorate Identifier 2004-NM-999-AD.” Each DMS AD docket also lists the directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes.

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2004-19540; Directorate Identifier 2004-NM-110-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments submitted by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov,, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov.

We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at http://www.faa.gov/language and http://www.plainlanguage.gov.

Examining the Docket

You can examine the AD docket on the Internet at http://dms.dot.gov,, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

We have received a report indicating that a circuit breaker of the fuel shutoff valve tripped due to a wire that chafed against the structure in the flammable leakage zone of the aft fairing, causing a short circuit. This occurred on a Boeing Model 757-200 series airplane that had accumulated approximately 10,900 total flight hours and 6,225 total flight cycles. Subsequent maintenance inspections of the remainder of the operator's fleet revealed 9 out of 13 airplanes had the same type of wire chafing. The causes of that chafing were missing or incorrectly installed wire sleeving, incorrect grommet installation, and incorrect wire clamp installation. The existing design allows contact between the wire bundle and the engine strut webs. Chafing between the wire bundle and the structure of the aft fairing could result in electrical arcing and subsequent ignition of flammable vapors and possible uncontrollable fire.

The wire bundles of the fuel shutoff valves on Model 757-200PF, -200CB, and -300 series airplanes are identical to those on the affected Model 757-200 series airplanes. Therefore, all of these models may be subject to the same unsafe condition.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletins 757-28A0073 (for Model 757-200, -200CB, and -200PF series airplanes) and 757-28A0074 (For Model 757-300 series airplanes), both dated November 20, 2003. The service bulletins describe procedures for inspecting for discrepancies of the wire bundles (W5100 for the left engine strut; W5200 for the right engine strut) from power plant station (PP STA) 278 aft, to the rear spar of the wing in the left and right engine-to-wing aft fairings, and other specified and corrective actions. The discrepancies include chafing of the wire bundles, missing or chafed sleeves, and incorrect installation of the caterpillar grommet. The procedures for the other specified and corrective actions include:

• Repairing any damage found, in addition to installing a new support bracket.
• Inspecting for chafed or missing sleeves at PP STA 278, 290, and 301, and adding a new wrap-on sleeve if the sleeve is chafed or missing.
• Inspecting the PP STA 278 and 301 bulkheads to ensure correct installation of the caterpillar grommet, and cleaning the area and installing a new grommet if the grommet is missing or incorrectly installed; and
• Re-routing the wire bundles.

The service bulletins also describe procedures for a functional test of the engine fuel shutoff valves. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. Therefore, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously.

Clarification of Inspection Terminology

In this proposed AD, the “inspections” of the wire bundles, as specified in the Boeing service bulletins are referred to as “detailed inspections.” We have included the definition for a detailed inspection in a note in the proposed AD.

Costs of Compliance

This proposed AD would affect about 613 airplanes worldwide and 335 airplanes of U.S. registry. The proposed actions would take about 16 work hours per airplane, at an average labor rate of $65 per work hour. Required parts would cost about $560 per airplane. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $536,000, or $1,600 per airplane.

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, or on 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 proposed AD. 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.