AD 2018-12-05

This AD is effective July 13, 2018.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of July 13, 2018.

For service information identified in this final rule, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717; internet https://www.myboeingfleet.com. You may view this service information at the FAA, Transport Standards Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195. It is also available on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2018-0074.

Payman Soltani, Aerospace Engineer, Airframe Section, FAA, Los Angeles ACO Branch, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5313; fax: 562-627-5210; email: payman.soltani@faa.gov.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. The NPRM published in the Federal Register on February 9, 2018 (83 FR 5743). The NPRM was prompted by reports of cracks found in the rear spar web and lower chord on the left and right wings. The NPRM proposed to require repetitive detailed inspections for cracking of the rear spar web and lower chord, and applicable on-condition actions.

We are issuing this AD to address cracks in the rear spar of the left and right wing between wing buttock line (WBL) 91 and WBL 155, which could lead to the inability of a principal structural element to sustain required flight loads and adversely affect the structural integrity of the airplane.

We gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM and the FAA's response to each comment.

The Boeing Company stated its support for the NPRM.

Southwest Airlines (Southwest), requested that we revise paragraph (h) of the proposed AD, which refers to the “Compliance” section of Boeing Alert Requirements Bulletin 737-57A1337 RB, dated September 14, 2017, regarding the different compliance times for the two inspection methods given in Table 1 of the “Compliance” section for Group 2 airplanes. Southwest stated that the planned inspection method should have no bearing on the timing of the inspection, and therefore the compliance times should be the same for both options. They did not specify which of the two compliance times they would favor.

We acknowledge the commenter's request. While the compliance times for inspections are not normally dependent on the planned inspection method, in this case, the initial compliance times were adjusted to account for differences in the probability of detection using a visual inspection versus an eddy current inspection. Because an eddy current inspection is more capable of detecting smaller cracks than a visual inspection, the initial compliance time was shortened for those airplanes that are inspected using the visual inspection option. We have not changed this AD in this regard.

Aviation Partners Boeing stated that the installation of winglets using Supplemental Type Certificate (STC) ST01219SE does not affect the actions specified in the NPRM.

We agree with the commenter. We have redesignated paragraph (c) of the proposed AD as paragraph (c)(1) of this AD and added paragraph (c)(2) to this AD to state that installation of STC ST01219SE does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST01219SE is installed, a “change in product” alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17.

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule with the changes described previously and minor editorial changes. We have determined that these minor changes:

• Are consistent with the intent that was proposed in the NPRM for addressing the unsafe condition; and

• Do not add any additional burden upon the public than was already proposed in the NPRM.

We also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule.

We reviewed Boeing Alert Requirements Bulletin 737-57A1337 RB, dated September 14, 2017. This service information describes procedures for repetitive detailed or surface High Frequency Eddy Current (HFEC) inspections for cracking of the rear spar web and lower chord, and applicable on-condition actions. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

We estimate that this AD affects 160 airplanes of U.S. registry. We estimate the following costs to comply with this AD:

We have received no definitive data that would enable us to provide cost estimates for the on-condition actions specified in this AD.

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 is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes and associated appliances to the Director of the System Oversight Division.

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),

(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):