RIN 2120-AA64
Key claim: The FAA wants operators of certain CFM56 jet engines to inspect and replace a turbine seal that can shed honeycomb material and crack nearby parts, to prevent engine failure.
Abstract
(Proposed Rule · Transportation Department, Federal Aviation Administration) The FAA proposes to adopt a new airworthiness directive (AD) for certain CFM International, S.A. (CFM) Model CFM56-5B, CFM56-5C, and CFM56-7B engines with a certain high-pressure turbine (HPT) inner stationary seal installed. This proposed AD was prompted by multiple reports of honeycomb separation from the surface of HPT inner stationary seals. This proposed AD would require initial and repetitive borescope inspections (BSIs) of the rotating air HPT front seal for cracks and, depending on the results, replacement with a part eligible for installation. This proposed AD would also require removal and replacement of the affected HPT inner stationary seal. This proposed AD would also require inspection of the affected HPT inner stationary seal for honeycomb separation and, depending on the results of the inspection, removal and replacement of the rotating air HPT front seal, HPT rotor blades, and No. 3 ball bearing. The FAA is proposing this AD to address the unsafe condition on these products.
Why this matters
CFM56 engines power a large share of the global narrowbody fleet (737 Classic/NG and A320ceo families), so an AD targeting a turbine seal failure mode reaches many operators and maintenance shops. The proposed inspection-and-replace approach follows the FAA’s standard pattern of catching a manufacturing/wear defect before it causes an uncontained failure or in-flight shutdown.