AD 2021-16-08

This AD is effective September 28, 2021.

For service information identified in this final rule, contact CFM International, S.A., Aviation Operations Center, 1 Neumann Way, M/D Room 285, Cincinnati, OH 45125; phone: (877) 432-3272; email: fleetsupport@ge.com. You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 1200 District Avenue, Burlington, MA 01803. For information on the availability of this material at the FAA, call (781) 238-7759. It is also available at https://www.regulations.gov by searching for and locating Docket No. FAA-2019-0597.

Christopher McGuire, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone: (781) 238-7120; fax: (781) 238-7199; email: Chris.McGuire@faa.gov.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2019-12-05, Amendment 39-19660 (84 FR 28717, June 20, 2019), (AD 2019-12-05). AD 2019-12-05 applied to all CFM CFM56-5B, CFM56-5C, and CFM56-7B model turbofan engines with a certain rotating air HPT front seal. AD 2019-12-05 required replacement of the affected rotating air HPT front seal with a part eligible for installation. The actions required by AD 2019-12-05 were interim and only addressed the highest risk engines with an affected rotating air HPT front seal that have a specified number of cycles since being reconfigured.

The NPRM published in the Federal Register on October 23, 2019 (84 FR 56709). AD 2019-12-05 was prompted by cracks found in the rotating air HPT front seal. In the NPRM, the FAA proposed to retain the requirements of AD 2019-12-05 and extend those requirements to engines that have fewer cycles since being reconfigured.

After the NPRM was issued, CFM revised its service information that provides instructions for replacing the affected rotating air HPT front seal. In addition, the revised service information addresses CFM56-5B or CFM56-7B model turbofan engines with a reconfigured rotating air HPT front seal that was previously operated in a CFM56-5C model turbofan engine, and specifies that those engines follow the removal limits established for CFM56-5C model turbofan engines. In addition, the FAA determined changes to the proposed AD were necessary based on comments received on the NPRM.

Accordingly, the FAA issued a supplemental notice of proposed rulemaking (SNPRM), which published in the Federal Register on March 23, 2021 (86 FR 15436). In the SNPRM, the FAA proposed to retain the requirements of AD 2019-12-05 and expand the applicability to require the replacement of affected rotating air HPT front seals installed on CFM CFM56-5B, CFM56-5C, and CFM56-7B model turbofan engines that have fewer cycles since being reconfigured than the engines affected by AD 2019-12-05. In the SNPRM, the FAA also proposed to require that CFM56-5B and CFM56-7B model turbofan engines with a reconfigured rotating air HPT front seal that was previously operated in a CFM56-5C model turbofan engine follow the removal requirements of the CFM56-5C model turbofan engine. The FAA is issuing this AD to address the unsafe condition on these products.

The FAA received comments from one commenter on the SNPRM. The commenter was The Boeing Company (Boeing). Boeing supported the proposed AD without change.

The FAA reviewed the relevant data, considered the comments received, and determined that air safety requires adopting the AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. This AD is adopted as proposed in the SNPRM.

The FAA reviewed CFM Service Bulletin (SB) CFM56-5B S/B 72-1074, Revision 02, dated November 6, 2019; CFM SB CFM56-5C S/B 72-0794, Revision 02, dated November 6, 2019; and CFM SB CFM56-7B S/B 72-1042, Revision 02, dated November 6, 2019. CFM SB CFM56-5B S/B 72-1074, Revision 02, contains procedures for replacing the affected rotating air HPT front seal on CFM CFM56-5B model turbofan engines. CFM SB CFM56-5C S/B 72-0794, Revision 02, contains procedures for replacing the affected rotating air HPT front seal on CFM CFM56-5C model turbofan engines. CFM SB CFM56-7B S/B 72-1042, Revision 02, contains procedures for replacing the affected rotating air HPT front seal on CFM CFM56-7B model turbofan engines.

The FAA estimates that this AD affects 4 engines installed on airplanes of U.S. registry.

The FAA estimates the following costs to comply with 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.

The FAA is 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.

The FAA has 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) Will not affect intrastate aviation in Alaska, 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.

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:

a. Removing Airworthiness Directive 2019-12-05, Amendment 39-19660 (84 FR 28717, June 20, 2019); and

b. Adding the following new airworthiness directive: