AD 2010-01-05 Airworthiness Directives; CFM International, S.A. CFM56-7B Series Turbofan Engines

This AD applies to: (1) CFM International, S.A. CFM56-7B20; -7B22; -7B24; -7B26; -7B27; -7B22/B1; -7B24/B1; -7B27/B1; -7B26/B1; -7B20/3; -7B22/3; -7B24/3; -7B26/3; -7B27/3; -7B22/3B1; -7B24/3B1; -7B27/3B1; -7B26/3B1; -7B26/3F; -7B27/B3; -7B27/3F; -7B27/3B1F; and -7B27/3B3 turbofan engines assembled with a low-pressure (LP) turbine rear frame, part number (P/N) 340-166-254-0; 340-166-255-0; 340-166-256-0; 340-166-257-0; 340-166-258-0; or 340-166-259-0; and (2) CFM International, S.A. CFM56-7B20/2; -7B22/2; -7B24/2; -7B26/2; and -7B27/2 turbofan engines assembled with a dual annular combustor and an LP turbine rear frame, P/N 340-177-551-0; 340-177-552-0; 340-177-553-0; 340-177-554-0; 340-177-555-0; or 340-177-556-0. (3) These engines are installed on, but not limited to, Boeing 737-600, 737-700, 737-800, and 737-900 series airplanes.

You are responsible for having the actions required by this AD performed within the compliance times specified unless the actions have already been done. Inspections of LP Turbine Rear Frames (f) For CFM International, S.A. CFM56-7B20; -7B22; -7B24; -7B26; -7B27; -7B22/B1; -7B24/B1; -7B27/B1; -7B20/3; -7B22/3; -7B24/3; -7B26/3; -7B27/3; -7B22/3B1; -7B24/3B1; -7B27/3B1; -7B26/3F; -7B27/3F; and -7B27/3B1F turbofan engines with an LP turbine rear frame, P/N 340-166-254-0; 340-166-255-0; 340-166-256-0; 340-166-257-0; 340-166-258-0; or 340-166-259-0, do the following: (1) Perform an initial eddy current inspection (ECI) of the LP turbine rear frame within 25,000 cycles-since-new (CSN) on the LP turbine rear frame. (2) For engines with unknown LP turbine rear frame CSN, perform an initial ECI within 300 cycles from the effective date of this AD. (3) Perform repetitive ECIs of the LP turbine rear frame, using the inspection intervals in paragraph 3.A. (8) of the Accomplishment Instructions of CFM International, S.A. SB No. CFM56-7B S/B 72-0579, Revision 5, dated March 30, 2009. (4) Use paragraphs 3.A. through 3.A. (7)(d) of the Accomplishment Instructions of CFM International, S.A. Service Bulletin (SB) No. CFM56-7B S/B 72-0579, Revision 5, dated March 30, 2009, to do the ECIs. (5) Remove LP turbine rear frames from service that have a total cumulated crack length at any location, of 0.79 inch (20 mm) or longer. (g) For CFM International, S.A. CFM56-7B26/B1; -7B27/B3; -7B26/3B1; and -7B27/3B3 turbofan engines with an LP turbine rear frame, P/N 340-166-254-0; 340-166-255-0; 340-166-256-0; 340-166-257-0; 340-166-258-0; or 340-166-259-0, do the following: (1) Perform an initial ECI of the LP turbine rear frame within 19,000 CSN on the LP turbine rear frame. (2) For engines with unknown LP turbine rear frame CSN, perform an initial ECI within 300 cycles from the effective date of this AD. (3) Perform repetitive ECIs of the LP turbine rear frame, using the inspection intervals in paragraph 3.A. (9) of the Accomplishment Instructions of CFM International, S.A. SB No. CFM56-7B S/B 72-0579, Revision 5, dated March 30, 2009. (4) Use paragraphs 3.A. through 3.A. (7)(d) of the Accomplishment Instructions of CFM International, S.A. Service Bulletin (SB) No. CFM56-7B S/B 72-0579, Revision 5, dated March 30, 2009, to do the ECIs. (5) Remove LP turbine rear frames from service that have a total cumulated crack length at any location, of 0.79 inch (20 mm) or longer. (h) For CFM International, S.A. CFM56-7B20/2; -7B22/2; -7B24/2; -7B26/2; and -7B27/2 turbofan engines assembled with a dual annular combustor and an LP turbine rear frame, P/N 340-177-551-0; 340-177-552-0; 340-177-553-0; 340-177-554-0; 340-177-555-0; or 340-177-556-0, do the following: (1) Perform an initial ECI of the LP turbine rear frame within 16,350 CSN on the LP turbine rear frame. (2) For engines with unknown LP turbine rear frame CSN, perform an initial ECI within 300 cycles from the effective date of this AD. (3) Perform repetitive ECIs of the LP turbine rear frame, using the inspection intervals in paragraph 3.A. (8) of the Accomplishment Instructions of CFM International, S.A. SB No. CFM56-7B S/B 72-0558, Revision 3, dated March 30, 2009. (4) Use paragraphs 3.A. through 3.A. (7)(d) of the Accomplishment Instructions of CFM International, S.A. SB No. CFM56-7B S/B 72-0558, Revision 3, dated March 30, 2009, to do the ECIs. (5) Remove LP turbine rear frames from service that have a total cumulated crack length at any location, of 0.43 inch (11 mm) or longer. Previous Credit (i) Initial inspection of LP turbine rear frames before the effective date of this AD performed using the Accomplishment Instructions of CFM International, S.A. SB No. CFM56-7B S/B 72-0579, original issue, Revision 1, Revision 2, Revision 3, or Revision 4, satisfy the requirements of paragraphs (f)(1), (f)(2), (g)(1), and (g)(2) of this AD. (j) Initial inspection of LP turbine rear frames before the effective date of this AD performed using the Accomplishment Instructions of CFM International, S.A. SB No. CFM56-7B S/B 72-0558, original issue, Revision 1, or Revision 2, satisfy the requirements of paragraphs (h)(1) and (h)(2) of this AD. Alternative Methods of

This AD results from a refined life analysis by the engine manufacturer that shows the need to identify an initial and repetitive inspection threshold for inspecting certain LP turbine rear frames. We are issuing this AD to prevent failure of the LP turbine rear frame from low-cycle-fatigue cracks. Failure of the LP turbine rear frame could result in engine separation from the airplane, possibly leading to loss of control of the airplane.