FAA: Check Those Turbine Cracks or Ground the Planes
Published Date: 9/14/2026
Proposed Rule
Summary
The FAA wants to keep certain CFM56-5B, 5C, and 7B engines safe by checking for cracks and honeycomb damage in key turbine parts. If problems show up, parts must be replaced to avoid engine trouble. Operators need to act quickly, with inspections and fixes happening regularly, helping prevent costly failures and keep flights smooth.
Analyzed Economic Effects
3 provisions identified: 0 benefits, 3 costs, 0 mixed.
Mandatory seal replacement at shop visit
At the next engine shop visit after the AD becomes effective, you must remove and replace the affected HPT inner stationary seal (P/N 1808M56G01). The FAA estimates replacement per engine costs at $680 labor plus $173,700 parts = $174,380, and estimates 39 U.S.-registered engines would total $6,800,820.
Large on-condition replacement costs if damage found
If cracks or honeycomb separation are found, you must replace components before further flight. The NPRM lists on-condition estimated costs per engine: rotating air HPT front seal about $602,080 total, HPT rotor blades (set) about $2,020,000 total, and No. 3 ball bearing about $71,140 total.
Mandatory repetitive borescope inspections
If you operate airplanes with the listed CFM56-5B/5C/7B engines, you must perform initial and repeating borescope inspections (BSIs) of the rotating air HPT front seal. The NPRM sets specific intervals by group: Group 1 — within 400 flight cycles (FCs) then every 800 FCs; Group 2 — within 300 FCs then every 800 FCs; Group 3 — within 125 FCs then every 250 FCs; Group 4 — within 400 FCs then every 800 FCs; Group 5 — within 300 FCs then every 800 FCs.
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Key Dates
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