AD 2021-05-18

For engines with a diffuser case assembly, part number 2A0051, 2A2081-01, 2A2581-01, 2A2883-01, 2A2885-01, 2A2889-01, 2A2891-01, 2A2896-01, 2A2897-01, or 2A3132 installed, perform an initial borescope inspection (BSI) of zones 1, 2, and 3 of the M-flange as follows:

(i) For engines with a diffuser case M-flange that has 19,000 or more cycles since new (CSN) on the effective date of this AD, perform the initial BSI of the M-flange before accumulating the “Inspect within (Cycles)” in Table 1 to paragraph (g)(1) of this AD. If the CSLFPI is unknown, use the CSN of the diffuser case M-flange.

(ii) For engines with a diffuser case M-flange that has fewer than 19,000 CSN on the effective date of this AD, perform the initial BSI of the M-flange before accumulating 20,300 CSN.

(iii) For engines with a diffuser case M-flange or diffuser case in which the CSN is unknown or cannot be determined, perform the initial BSI of the M-flange before accumulating the “Inspect within (Cycles)” in Table 1 to paragraph (g)(1) of this AD using one of the following options:

(A) If the cycles of the diffuser case M-flange are unknown or cannot be determined, use the total cycles on the diffuser case.

(B) If the cycles on the diffuser case are unknown or cannot be determined and it can be documented that the diffuser case was always installed on the engine, use total engine cycles.

(C) If neither paragraph (g)(1)(iii)(A) or (B) applies, perform the BSI of the M-flange within 250 cycles after the effective date of this AD.

(iv) Use the Accomplishment Instructions, paragraphs 2.A. through 2.G. of IAE Non-Modification Alert Service Bulletin (NMASB) V2500-ENG-72-A0706, Revision 2, dated November 7, 2019 (the NMASB), to perform the initial BSI.

Note 1 to paragraph (g)(1)(iv): Paragraph 2.G. of the NMASB describes procedures for performing a local fluorescent penetrant inspection of the M-flange if you are unable to confirm if an indication is a crack.

(v) If no crack is found as a result of the inspections required by paragraphs (g)(1)(i) through (iv) of this AD, repeat the BSI of zones 1, 2, and 3 of the M-flange at intervals not to exceed 2,100 cycles since the previous BSI.

(vi) If a crack is found as a result of the inspections required by paragraphs (g)(1)(i) through (iv) of this AD, replace the diffuser case M-flange or repeat the BSI of zones 1, 2, and 3 of the M-flange as specified by either “Table 2: Fly on Limits” or “Table 4: Fly on Limits,” in paragraph 2.H., Accomplishment Instructions, of the NMASB as appropriate for the affected the engine model.

(i) At the next engine shop visit after the effective date of this AD or before the diffuser case M-flange accumulates 20,000 CSN, whichever occurs later, replace the diffuser case M-flange.

(ii) For engines with a diffuser case M-flange or diffuser case in which the CSN is unknown or cannot be determined, perform one of the following options:

(A) If the cycles of the diffuser case M-flange are unknown or cannot be determined, at the next engine shop visit after the effective date of this AD or before the diffuser case accumulates 20,000 CSN, whichever occurs later, replace the diffuser case M-flange.

(B) If the cycles of the diffuser case are unknown or cannot be determined, and if it can be documented that the diffuser case was always installed on the engine, at the next engine shop visit after the effective date of this AD or before the engine accumulates 20,000 CSN, whichever occurs later, replace the diffuser case M-flange.

(C) If the cycles on the diffuser case M-flange are unknown or cannot be determined based on the criteria identified in paragraphs (g)(2)(ii)(A) and (B), or it cannot be shown that the diffuser case was always installed on the engine, at the next engine shop visit after the effective date of this AD, replace the diffuser case M-flange.

Note 2 to paragraph (g)(2)(ii): Guidance on performing the replacement of the diffuser case M-flange described in paragraphs (g)(2)(i) and (ii) can be found in the Accomplishment Instructions, paragraphs 1.A. and B., of IAE SB V2500-ENG-72-0709, Revision 1, dated February 20, 2020.

(iii) Thereafter, repeat the replacement of the diffuser case M-flange before accumulating 20,000 cycles since the previous replacement.

(iv) Replacement of the diffuser case M-flange is the terminating action for the repetitive BSIs required by paragraph (g)(1) of this AD.

After the effective date of this AD, do not install a diffuser case onto any affected engine if the diffuser case M-flange has more than 20,000 CSN.