DEPARTMENT OF TRANSPORTATION Federal Aviation Administration

14 CFR Part 39
[Docket No. FAA-2022-0160; Project Identifier AD-2022-00009-E] RIN 2120-AA64
Airworthiness Directives; CFM International, S.A. Turbofan Engines (summary)
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) for certain CFM International, S.A. (CFM) LEAP-1A model turbofan engines. This proposed AD was prompted by reports of two in-flight shutdowns (IFSDs) and subsequent investigation by the manufacturer that revealed cracks in the high-pressure turbine (HPT) rotor stage 1 blades (rotor stage 1 blade deterioration and airfoil distress due to the build-up of dust.). The FAA is proposing this AD to address the unsafe condition on these products.
Background
The FAA received reports of two single-engine IFSDs on airplanes powered by LEAP-1A model turbofan engines, operating extensively in the Middle East and North Africa (MENA) region. A post-flight BSI of the HPT module revealed that the engine failures were due to cracks in the HPT rotor stage 1 blades. After investigation, the manufacturer determined that engines operating in the MENA region are susceptible to accelerated HPT rotor stage 1 blade deterioration and airfoil distress due to the build-up of dust. This unsafe condition, if not addressed, could result in failure of the engine, in- flight shutdown, loss of thrust control, and loss of the airplane.
(g) Required Actions
(1) Group 1 Engines: Borescope Inspection (BSI) of HPT Rotor Stage 1 Blades and HPT Stator Stage 1 Nozzle Set
For Group 1 engines with an affected HPT rotor stage 1 blade installed:
(i) Within 100 flight cycles (FCs) after accumulating 800 Middle East and North Africa (MENA) region takeoffs on the HPT rotor stage 1 blade, before the HPT rotor stage 1 blade accumulates 1,750 cycles since new (CSN), or within 100 FCs after the effective date of this AD, whichever occurs later…
(ii) Thereafter, at intervals not to exceed 150 FCs since the last BSI, perform a repetitive BSI of the HPT rotor stage 1 blades and HPT stator stage 1 nozzle set in accordance with the Accomplishment Instructions, paragraphs 5.E.(1)(c) and 5.E.(1)(d), of the SB.
For Group 2 engines with an affected HPT rotor stage 1 blade installed:
(i) Within 100 FCs after accumulating 800 MENA takeoffs on the HPT rotor stage 1 blade, before the HPT rotor stage 1 blade accumulates 2,600 CSN, or within 100 FCs after the effective date of this AD, whichever occurs later, perform an initial BSI ofthe HPT rotor stage 1 blades and HPT stator stage 1 nozzle set in accordance with the Accomplishment Instructions, paragraphs 5.E.(1)(c) and 5.E.(1)(d), of the SB.
(ii) Thereafter, at intervals not to exceed 300 FCs since the last BSI, perform a repetitive BSI of the HPT rotor stage 1 blades and HPT stator stage 1 nozzle set in accordance with the Accomplishment Instructions, paragraphs 5.E.(1)(c) and 5.E.(1)(d), of the SB.
Issued on March 10, 2022.
Lance T. Gant, Director,
Compliance & Airworthiness Division,
Aircraft Certification Service.
[FR Doc. 2022-05524 Filed: 3/18/2022 8:45 am; Publication Date: 3/21/2022]