AD/CFM56/26 Low Pressure Turbine Rear Frame Life (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

CFM International Turbine Engines - CFM56 Series

AD/CFM56/26 Low Pressure Turbine Rear Frame Life 7/2007 TX

Applicability:

CFM International (CFM) CFM56-7B18, -7B20, -7B22, -7B22/B1, -7B22/B2, -7B24, -7B24/B1, -7B26, -7B26/B1, -7B26/B2, -7B27, -7B27/B1, -7B27/B3 turbofan engines equipped with a low pressure turbine (LPT) rear frame part number (P/N) 340-166-205-0, 340-166-206-0, 340-166-207-0, 340-166-208-0, 340-166-209-0 or 340-166-210-0.

Note 1:  These engines are installed on, but not limited to, Boeing 737series aeroplanes.

Requirement:

1.    For LPT rear frame P/N 340-166-205-0, 340-166-206-0, 340-166-207-0,
340-166-208-0, 340-166-209-0, 340-166-210-0, comply with the Low Cycle Fatigue (LCF) life limits in accordance with chapters 05-12-04 and 05-21-03 in CFM56-7B ESM, revision 33, dated 15 November 2006, or later NAA approved revision.

2.    If the number of cycles accumulated since new by a LPT rear frame P/N
340-166-205-0, 340-166-206-0, 340-166-207-0, 340-166-208-0, 340- 166-209-0, 340-166-210-0 cannot be established, then remove and replace the LPT rear frame, or perform the inspections detailed in CFM56-7B Service Bulletin S/B
72-0579 revision 1, or later NAA approved revision.

Note 2:  EASA AD 2007-0104 dated 17 April 2007 refers.

Compliance:

1.    Within 7 days from the effective date of this AD.

2.    Within 300 flight cycles from the effective date of this AD.

This Airworthiness Directive becomes effective on 11 May 2007.

Background: Before the issue of the CFM56-7B Engine Shop Manual (ESM) Temporary Revision (TR) 05-0071, the LPT rear frames were neither subject to a life limit nor a mandatory inspection.  Using a refined damage tolerant approach accounting for crack initiation and propagation to insure any cracking that is present will not grow to unsafe levels; CFM has now established a low cycle fatigue (LCF) life limit for the LPT rear frames.  This requirement was first introduced by revision TR 05-0071 of the CFM56-7B ESM.  This revision has been integrated into revision 33 of the CFM56-7B ESM.  This AD is issued to make sure that all operators are informed about these LCF life limits affecting new P/Ns and revise their aircraft maintenance programs accordingly.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

8 May 2007