Airworthiness Directives; Boeing Model 737-200, -200C, -300, -400, -500, -600, -700, -700C, -800, and -900 Series 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 737-200, -200C, -300, -400, -500, -600, -700, -700C, -800, and -900 series airplanes. This proposed AD would require a one-time detailed inspection for discrepancies of the secondary fuel vapor barrier of the wing center section, and related investigative/corrective actions if necessary. This proposed AD is prompted by reports that the secondary fuel vapor barrier was not applied correctly to, or was missing from, certain areas of the wing center section. We are proposing this AD to prevent fuel or fuel vapors from leaking into the cargo or passenger compartments and coming into contact with a possible ignition source, which could result in fire or explosion.

DATES:

We must receive comments on this proposed AD by December 27, 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.

You can get the service information identified in this proposed AD from Boeing Commercial Airplanes, PO 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: 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.

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-2004-19567; Directorate Identifier 2004-NM-118-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 website, 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 in person at the Docket Management Facility office between 9:00 a.m. and 5:00 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located 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, during manufacture, the secondary fuel vapor barrier was not applied correctly to the wing center section front spar and upper panel of certain Boeing Model 737-300 series airplanes. The vapor barrier was also not applied continuously along the front spar vertical stiffeners and the top panel floor beams. In addition, inspections of Boeing Model 737-600, -700, and -800 series airplanes revealed these same conditions. The secondary fuel vapor barrier was also missing from the side body corner of the spar upper panel of the wing center section and the lower row of fasteners on the front spar. The vapor barrier on these airplanes also was too thin in some areas and too thick in other areas of the top panel and front spar. This condition, if not corrected, could result in fuel or fuel vapors leaking through fasteners or cracks in the wing center section into the cargo or passenger compartments and coming into contact with a possible ignition source, which could result in fire or explosion.

The vapor barrier installations on Boeing Model 737-300 series airplanes are identical to those on Model 737-200, -200C, -400, and -500 series airplanes, and the vapor barrier installations on Model 737-600, -700, and -800 series airplanes are identical to those on Model 737-700C, and -900 series airplanes. Therefore, all of these models may be subject to the identified unsafe condition.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-57-1261, dated February 27, 2003; and Boeing Special Attention Service Bulletin 737-57-1250, Revision 1, dated September 4, 2003. The service bulletins describe procedures for a one-time detailed visual inspection for discrepancies of the secondary fuel vapor barrier of the front spar and top panel of the wing center section; and related investigative/corrective actions, if necessary. Discrepancies include areas of the secondary fuel vapor barrier that are missing, peeling, non-transparent, non-continuous, too thin, or too thick. Investigative action includes measuring the thickness of the secondary fuel vapor barrier with a non-conductive coating thickness gauge. Corrective actions include removing incorrectly applied secondary fuel vapor barrier, primers, sealants, corrosion inhibitors, and embedded metallic particles; and applying new primers, sealants, corrosion inhibitors, filleting seals, and secondary fuel vapor barrier; as necessary.

Accomplishing the actions specified in the service bulletins 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 to require a one-time detailed inspection for discrepancies of the secondary fuel vapor barrier of the wing center section, and related investigative/corrective actions if necessary. The proposed AD would require you to use the service information described previously to perform these actions except as specified under “Clarification of Inspection Terminology.”

Clarification of Inspection Terminology

In this proposed AD, the “detailed visual inspection” specified in the service bulletins is referred to as a “detailed inspection.” We have included the definition for a detailed inspection in a note in the proposed AD.

The service bulletins refer to a “special detailed inspection'; however, this action is actually a measurement of the thickness of the secondary fuel vapor barrier using a non-conductive coating thickness gauge. The proposed AD would refer to this measurement of the secondary fuel vapor barrier as “related investigative action” rather than a special detailed inspection.

Costs of Compliance

This proposed AD would affect about 1,521 airplanes of U.S. registry and 3,861 airplanes worldwide. We estimate the average labor rate to be $65 per work hour. We estimate that it would take the number of work hours shown in the following table to accomplish the proposed actions for each airplane. Parts and materials are standard and are to be supplied by the operator. Based on these figures, the cost impact of the proposed AD is estimated to range between $325 and $910 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.