E7-5907. Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 and -900 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. This proposed AD would require an inspection of the fillet sealant at the inboard and outboard sides of the receptacles in the wheel wells of the main landing gear, and related investigative/corrective actions if necessary. This proposed AD results from reports of in-production airplanes with missing or insufficient fillet sealant around the receptacles at the disconnect bracket. We are proposing this AD to prevent corrosion damage due to missing or insufficient fillet sealant. Such corrosion could result in insufficient electrical bonding between the connectors and the disconnect bracket, and consequent loss of the shielding that protects the wire bundles from lightning, electromagnetic interference (EMI), and high intensity radiated field (HIRF). Loss of lightning, EMI, and HIRF protection at those receptacles could cause failure of multiple electrical systems and subsequent loss of several critical control systems that are necessary for safe flight. In addition, a lightning strike could cause arcing in the fuel tank; this potential ignition source, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

DATES:

We must receive comments on this proposed AD by May 14, 2007.

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.
• Fax: [phone].
• 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.

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

FOR FURTHER INFORMATION CONTACT:

Binh Tran, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

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 in the ADDRESSES section. Include the docket number “FAA-2007-27740; Directorate Identifier 2006-NM-290-AD” at the beginning 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 received 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 may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Docket

You may 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 [phone]) 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 Docket Management System receives them.

Discussion

We have received a report indicating that 333 Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes in the production factory had missing or insufficient fillet sealant around the receptacles in the wheel wells of the main landing gear (MLG). Missing or insufficient fillet sealant could result in corrosion damage, and consequent insufficient electrical bonding between the connectors and the disconnect bracket. The loss of electrical bonding could result in loss of the shielding that protects the wire bundles from lightning, electromagnetic interference (EMI), and high intensity radiated field (HIRF). The loss of lightning, EMI, and HIRF protection at those receptacles could cause multiple electrical systems failures. Those failures could result in the loss of several critical control systems that are necessary for safe flight. In addition, a lightning strike could cause arcing in the fuel tank; this potential ignition source, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-24-1169, dated December 15, 2006. The service bulletin describes procedures for a detailed inspection of the fillet sealant at the inboard and outboard sides of the receptacles in the MLG wheel wells. For airplanes on which the sealant is missing or otherwise insufficient, the service bulletin describes the following related investigative and corrective actions:

• An additional detailed inspection to detect signs of corrosion damage of the connector and receptacle;
• Cleaning of any corrosion-free connector;
• Cleaning of any receptacle that has corrosion damage on less than 20 percent of the total surface area of the receptacle flange;
• Replacement (with a new part having the same part number) of any receptacle that has corrosion on more than 20 percent of the total surface area of the receptacle flange;
• Replacement of corroded connectors with connectors identified in the service bulletin; and
• Application of fillet sealant around the receptacles.

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. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously.

Costs of Compliance

There are about 333 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Estimated Costs

Work hours	Average labor rate per hour	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
1	$80	$80	118	$9,440

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, 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 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

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-27740; Directorate Identifier 2006-NM-290-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by May 14, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes; certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-24-1169, dated December 15, 2006.

Unsafe Condition

(d) This AD results from reports of in-production airplanes with missing or insufficient fillet sealant around the receptacles installed in the wheel wells of the main landing gear (MLG). We are issuing this AD to prevent corrosion damage due to missing or insufficient fillet sealant. Such corrosion could result in insufficient electrical bonding between the connectors and the disconnect bracket, and consequent loss of the shielding that protects the wire bundles from lightning, electromagnetic interference (EMI), and high intensity radiated field (HIRF). Loss of lightning, EMI, and HIRF protection at those receptacles could cause failure of multiple electrical systems and subsequent loss of several critical control systems that are necessary for safe flight. In addition, a lightning strike could cause arcing in the fuel tank; this potential ignition source, 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.

Inspection

(f) Within 24 months after the effective date of this AD, perform a detailed inspection to determine if there is sufficient fillet sealant at the inboard and outboard sides of the receptacles in the MLG wheel wells, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-24-1169, dated December 15, 2006. Do all applicable related investigative and corrective actions before further flight in accordance with the service bulletin.

Alternative Methods of Compliance (AMOCs)

(g)(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) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

Issued in Renton, Washington, on March 23, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.