AD 2017-06-14

This AD is effective May 2, 2017.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of May 2, 2017.

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 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. It is also available on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2016-9068.

George Garrido, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification Office (ACO), 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5232; fax: 562-627-5210; email: george.garrido@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 737-300, -400, and -500 series airplanes. The NPRM published in the Federal Register on September 8, 2016 (81 FR 62022) (“the NPRM”). The NPRM was prompted by reports of cracks in the horizontal stabilizer lower skins. The NPRM proposed to require inspections for cracking of the horizontal stabilizer lower skin, including repetitive inspections, as applicable, and corrective actions if necessary; and also proposed actions that would terminate certain repetitive inspections. We are issuing this AD to detect and correct cracks in horizontal stabilizer lower skins resulting in reduced local stiffness of the horizontal stabilizer, which can cause heavy vibration leading to loss of structural integrity of the horizontal stabilizer.

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

Boeing expressed support for the NPRM.

All Nippon Airways (ANA) requested that we revise paragraphs (h)(1) and (h)(3) of the proposed AD to state “repair common to the rear spar lower chord between station (STA) 83.50 and STA 249.10,” instead of “repair.” ANA stated that there might be a repair installed on the lower skin of the horizontal stabilizer that is not addressed in Boeing Special Attention Service Bulletin 737-55-1059, Revision 1, dated April 6, 2016 (“SASB 737-55-1059 R1”). ANA explained that some structural repair manual repairs and external doublers are not applicable to the inspection area specified in SASB 737-55-1059 R1.

We agree with ANA's request. Specifying the location of the applicable repairs may reduce potential confusion. Therefore, we have revised paragraphs (h)(1), (h)(2), and (h)(3) of this AD to specify the location of the applicable repairs.

ANA requested that we clarify the fastener requirements. ANA stated that figure 3 in Boeing Special Attention Service Bulletin 737-55-1059, dated September 10, 1998, specifies to use blind rivets and Hi-lok fasteners; however, compliance table 2, note (b), in SASB 737-55-1059 R1, states that doublers installed with solid rivets do not need to be inspected for any loose or missing fasteners. ANA explained that Boeing told ANA that Hi-lok fasteners do not require inspection for any loose or missing fasteners.

We agree to clarify the fastener requirements. We infer that ANA is requesting that we update paragraph (h) of this AD to specify that Hi-lok fasteners do not require inspection. We have determined that Hi-lok fasteners do not require inspection. Therefore, we have added paragraph (i)(3) to this AD to specify that where SASB 737-55-1059 R1 specifies that doublers installed with solid rivets do not need to be inspected for loose or missing fasteners, this AD does not require doublers installed with solid rivets or Hi-lok fasteners to be inspected for loose or missing fasteners. We have also revised paragraph (h)(1) of this AD to reference this exception.

ANA requested that we revise paragraph (h) of the proposed AD to refer to the horizontal stabilizer configuration with the applicable repair installed side only. ANA asserted that the wording of paragraph (h) of the proposed AD could be interpreted to require inspection of both the repaired and unrepaired sides of the horizontal stabilizer.

We agree with ANA's request. The wording in the proposed AD is not clear regarding what is required if an airplane has left and right stabilizers that are different configurations. For example, the left-side stabilizer may have a repair installed common to the rear spar lower chord (configuration 2), whereas the right side may not have a repair (configuration 1). We have revised the affected airplanes in paragraph (g) of this AD from “Group 1, Configuration 1, airplanes” to “any Configuration 1 horizontal stabilizer on Group 1 airplanes”. We have revised the affected products in paragraph (h) of this AD from “Group 1, Configuration 2, airplanes” to “any Configuration 2 horizontal stabilizer on Group 1 airplanes.”

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

We concur 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 final rule. Therefore, for airplanes on which STC ST01219SE is installed, a “change in product” 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 AD 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 correcting 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 AD.

We reviewed SASB 737-55-1059 R1. The service information describes procedures for doing inspections of the horizontal stabilizer lower skin, and repairs. The service information also describes procedures for doing actions that would terminate certain repetitive inspections. 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 270 airplanes of U.S. registry.

We estimate the following costs to comply with this AD:

We estimate the following costs to do any necessary repairs that will be required based on the results of the inspection. We have no way of determining the number of aircraft that might need these repairs:

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 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):