E7-22000. Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 and -900 Series Airplanes

AGENCY:

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

ACTION:

Final rule.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. This AD requires 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 AD results from reports of in-production airplanes with missing or insufficient fillet sealant around the receptacles at the disconnect bracket. 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.

DATES:

This AD becomes effective December 20, 2007.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of December 20, 2007.

ADDRESSES:

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 AD, the regulatory evaluation, any comments received, and other information. The address for the Docket Office (telephone [phone]) is the Document Management Facility, U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.

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:

Examining the Docket

You may examine the AD docket on the Internet at http://dms.dot.gov or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone [phone]) is located on the ground floor of the West Building at the DOT street address stated in the ADDRESSES section.

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. That NPRM was published in the Federal Register on March 30, 2007 (72 FR 15073). That NPRM proposed to 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.

Comments

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

Support for NPRM

Boeing and AirTran Airways support the NPRM's proposed actions.

Request for Parts Availability Accounting

AirTran Airways requests that the expected parts usage and parts availability be reviewed and addressed for feasibility prior to the release of the final rule to ensure that parts shortages will not necessitate requests for unnecessary alternative means of compliance or adjustments of the compliance time. The commenter adds that there are 36 part numbers that could possibly need replacement if there is corrosion beyond the acceptable limits in the service bulletin. Of these 36 connectors, 9 part numbers are not available; of those, 5 do not appear to be in the production pipeline. Quite a few part numbers show less than a dozen available.

We agree with the request and have coordinated with Boeing regarding AirTran's concern. The NPRM cited Boeing Special Attention Service Bulletin 737-24-1169, dated December 15, 2006. Since we issued the NPRM, Boeing has revised the service bulletin. Revision 1, dated August 6, 2007, provides optional connector part numbers, which will ensure adequate replacement parts for the specified corrective actions. The remaining information in Revision 1 is essentially unchanged. We have revised paragraphs (c) and (f) of this final rule to refer to Revision 1 of the service bulletin as the appropriate source of service information for the applicability and the required actions. We have included credit for actions previously performed in accordance with the original service bulletin.

Conclusion

We have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

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 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 AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866;

(2) Is not a “significant rule” under 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 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
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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):

2007-23-10 Boeing: Amendment 39-15256. Docket No. FAA-2007-27740; Directorate Identifier 2006-NM-290-AD.

Effective Date

(a) This AD becomes effective December 20, 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, Revision 1, dated August 6, 2007.

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, Revision 1, dated August 6, 2007. Do all applicable related investigative and corrective actions before further flight in accordance with the service bulletin.

(g) Accomplishment of an inspection and applicable related investigative and corrective actions done before the effective date of this AD in accordance with Boeing Special Attention Service Bulletin 737-24-1169, dated December 15, 2006, is considered acceptable for compliance with the corresponding requirements of paragraph (f) of this AD.

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.

Material Incorporated by Reference

(i) You must use Boeing Special Attention Service Bulletin 737-24-1169, Revision 1, dated August 6, 2007, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to http://www.archives.gov/​federal-register/​cfr/​ibr-locations.html.

Issued in Renton, Washington, on November 2, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.