AD 2014-13-10

This AD is effective August 19, 2014.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of August 19, 2014.

For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544-5000, extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. You may view this referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the availability of this material at the FAA, call 425-227-1221.

Georgios Roussos, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6482; fax: 425-917-6590; email: georgios.roussos@faa.gov.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. The NPRM published in the Federal Register on December 12, 2013 (78 FR 75512). The NPRM was prompted by a report of installation of incorrect wire support clamps within the bay area of the left and right ECS during production; the ECS bay area is a flammable leakage zone. Use of incorrect wire support clamps that are not fully cushioned could allow electrical power wiring to come in contact with the exposed metal of the improper clamp, causing a short circuit and subsequent electrical arcing. The NPRM proposed to require inspecting to identify the part number of the wire support clamp, and related investigative and corrective actions if necessary. We are issuing this AD to prevent electrical arcing and a potential ignition source, which, in combination with flammable fuel vapors, could result in a fuel tank explosion, and consequent loss of the airplane.

We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the proposal (78 FR 75512, December 12, 2013) and the FAA's response to each comment.

Boeing, All Nippon Airways (ANA), and American Airlines (AA) asked that the third sentence in the “Relevant Service Information” section of the NPRM (78 FR 75512, December 12, 2013) be removed. That sentence specified “The related investigative actions include an eddy current inspection of the wing front spar for cracking and a detailed inspection of the bolt forward of the wing front spar upper chord for cracking or missing bolts.” Boeing stated that those actions seem unrelated to the intent of the AD. ANA stated that the eddy current inspection is not specified in Boeing Special Attention Service Bulletin 737-28-1312, dated April 19, 2013. AA stated that those actions are not included in the referenced service information, and asked that those actions be clarified or that the “Relevant Service Information” section be corrected by removing those actions.

We agree that the “Relevant Service Information” section in the NPRM (78 FR 75512, December 12, 2013) should not have stated that the related investigative actions include an eddy current inspection of the wing front spar for cracking; that inspection is not related to the unsafe condition addressed by this AD. However, the “Relevant Service Information” section of the NPRM is not carried over into this final rule; therefore, no change to this final rule is necessary in this regard.

AA asked that we add “equivalent fully cushioned wire clamps” to the approved part numbers (P/Ns) identified in paragraph (h) of the proposed AD (78 FR 75512, December 12, 2013) (redesignated as paragraph (i) of this AD). AA stated that paragraph (h) of the proposed AD prohibits the installation of a wire support clamp within the ECS bay area, unless the clamp has P/N TA0930034-10, TA0930034-10P, TA0930034-11, or TA0930034-12P. AA noted that adding “equivalent fully cushioned wire clamps” would account for future part number changes and future availability issues of the included part numbers. AA also asserted that including the equivalent clamps also would reduce the potential for airplanes becoming noncompliant during future maintenance.

We do not agree to add “equivalent fully cushioned wire clamps” to the approved part numbers identified in paragraph (i) of this AD (designated as paragraph (h) of the proposed AD). AA did not submit any data to show how equivalency of the wire support clamp is to be established, maintained, and controlled. However, under the provisions of paragraph (j) of this AD, we may consider requests to use alternate clamps if sufficient data are submitted to substantiate that these clamps meet the standards for the environmental (temperature, vibration, fluid resistance) and performance requirements necessary to provide an acceptable level of safety. We have not changed this final rule in this regard.

AA asked that we change the inspection estimate in the “Costs of Compliance” section in the NPRM (78 FR 75512, December 12, 2013) from 6 to 24 work-hours, as specified in Boeing Special Attention Service Bulletin 737-28-1312, dated April 19, 2013.

We agree to change the work-hour estimate for the inspection specified in the “Costs of Compliance” section. After further review of Boeing Special Attention Service Bulletin 737-28-1312, dated April 19, 2013, we have determined that the work-hour estimate of 24 hours is based on correct installation of the wire clamps and does not include repairs to the wiring. Therefore, we have increased the work hour estimate for the inspection specified in the “Costs of Compliance” section of this final rule.

Since we issued the NPRM (78 FR 75512, December 12, 2013), Boeing has issued Special Attention Service Bulletin 737-28-1312, Revision 1, dated April 21, 2014. No additional work is necessary on airplanes that were changed using Boeing Special Attention Service Bulletin 737-28-1312, dated April 19, 2013. We have added Boeing Special Attention Service Bulletin 737-28-1312, Revision 1, dated April 21, 2014, to paragraphs (c) and (g) of this AD, and added a new credit paragraph (h) to this AD giving credit for Boeing Special Attention Service Bulletin 737-28-1312, dated April 19, 2013.

Since we issued the NPRM (78 FR 75512, December 12, 2013), we have determined that the language used in the “Parts Installation Limitations” paragraph of the AD needs clarification. As written, the language could be interpreted as applying to “all” clamps located in the ECS bay area; however, the limitation only applies to certain clamps. We have changed paragraph (h) of the the proposed AD (redesignated as paragraph (i) of this AD) to provide that clarification.

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously. We also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.

We estimate that this AD affects 519 airplanes of U.S. registry.

We estimate the following costs to comply with this AD:

We estimate the following costs to do any necessary related investigative and corrective actions that would be required based on the results of the inspection. We have no way of determining the number of aircraft that might need these actions.

We have received no definitive data that would enable us to provide cost estimates for the on-condition repair of chafed or damaged wiring specified in this AD.

According to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all costs in our cost estimate.

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.

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 the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),

(3) Will not affect intrastate aviation in Alaska, and

(4) 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.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

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

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