Airworthiness Directive · Amendment 39-18952 · Turbine engine compressor section
CFM International S.A. Turbofan Engines
This AD applies to CFM International S.A. (CFM) CFM56-3, -3B, and -3C turbofan engines with steel high-pressure compressor (HPC) stator case, part numbers (P/Ns)1499M30G01, 1499M30G02, 1499M30G03, or 1676M88G01, installed.
We are adopting a new airworthiness directive (AD) for certain CFM International S.A. (CFM) CFM56-3, -3B, and -3C turbofan engines. This AD was prompted by a report of dual-engine loss of thrust control (LOTC) that resulted in an air turn back. This AD requires initial and repetitive checks of the variable stator vane (VSV) actuation system in the high-pressure compressor (HPC). We are issuing this AD to address the unsafe condition on these products.
(1) Inspect the affected engines to determine if the compressor front stator case is marked with “RP031” adjacent to the part number. If the case is marked with “RP031,” no further action is required. If the case is not marked with “RP031,” follow the remaining steps in paragraph (f) of this AD.
(2) Perform an initial pull force check of stage 1, stage 2, and stage 3 of the compressor variable stator vane (VSV) actuation system.
(i) If any stage requires more than 100 lb force to move the actuation ring, ream the VSV bores and apply anti-corrosion coating to stages 1, 2, and 3, prior to further flight, or replace with an HPC stator case that is eligible for installation and passes the VSV pull force check with measurements of 75 lb or less.
(ii) If any stage requires more than 75 lb, but less than or equal to 100 lb force to move the actuation ring, repeat the inspection within 3 months since last inspection.
(iii) If all stages require 75 lb force or less to move the actuation rings, repeat the inspection within 12 months since last inspection.
(3) Thereafter, continue to perform repetitive pull force checks of stages 1, 2, and 3 of the compressor VSV actuation system and disposition as specified in paragraphs (2)(i) through (iii) of this AD.
Reaming the VSV bores and applying anti-corrosion coating, as specified in paragraph (f)(2)(i) of this AD, is terminating action to the repetitive inspections required by paragraph (f)(3) of this AD.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
