AD 2021-10-09 Requires Removal, Inspection, And Replacement Of The Affected HPT Inner Stationary Seal

The FAA is adopting a new airworthiness directive (AD) for all CFM International, S.A. (CFM) CFM56-5B and CFM56-7B model turbofan engines with a certain high-pressure turbine (HPT) inner stationary seal installed.

This AD was prompted by cracks found in the rotating air HPT front seal. This AD requires removal, inspection, and replacement of the affected HPT inner stationary seal and, depending on the findings, replacement of the rotating air HPT front seal, HPT rotor blades, and No. 3 ball bearing. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective June 24, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all CFM CFM56-5B and CFM56-7B model turbofan engines with a certain HPT inner stationary seal installed. The NPRM published in the Federal Register on September 20, 2019 (84 FR 49487). The NPRM was prompted by a report that two cracks were discovered on a CFM CFM56-5B model turbofan engine rotating air HPT front seal during a routine engine shop visit. After investigation, CFM determined that the HPT inner stationary seal, part number 1808M56G01, may not have received the correct braze heat treat cycle at the time of the honeycomb replacement. As a result, the affected HPT inner stationary seal could lead to a localized separation of the replaced honeycomb, which may reduce the life of the rotating air HPT front seal. In the NPRM, the FAA proposed to require removal, inspection, and replacement of the affected HPT inner stationary seal and, depending on the findings, replacement of the rotating air HPT front seal, HPT rotor blades, and No. 3 ball bearing. The FAA is issuing this AD to address the unsafe condition on these products.

FMI: www.regulations.gov