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Federal Register / Vol. 86, No. 56 / Thursday, March 25, 2021 / Rules and Regulations
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 g1 of this AD. If the CSLFPI is unknown, use the CSN of the diffuser case M-flange.
ii For engines with a diffuser case Mflange 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 Mflange 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 g1 of this AD
using one of the following options:

A If the cycles of the diffuser case Mflange 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 g1iiiA 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 NonModification Alert Service Bulletin NMASB
V2500ENG72A0706, Revision 2, dated November 7, 2019 the NMASB, to perform the initial BSI.
Note 1 to paragraph g1iv: 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 g1i 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 g1i 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.

Table 1 to paragraph gl -M-flange cycle inspection limits
30,000 and greater
250

20,000 to 29,999

500

15,000 to 19,999

1,000

1 to 14,999

1,300

0

2,100

2 Replacement of the Diffuser Case MFlange 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 Mflange 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 Mflange 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 Mflange.
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 Mflange are unknown or cannot be determined based on the criteria identified in paragraphs g2iiA 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.

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Note 2 to paragraph g2ii: Guidance on performing the replacement of the diffuser case M-flange described in paragraphs g2i and ii can be found in the Accomplishment Instructions, paragraphs 1.A. and B., of IAE SB V2500ENG720709, 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 Mflange is the terminating action for the repetitive BSIs required by paragraph g1 of this AD.
h Installation Prohibition 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.
i Credit for Previous Actions You may take credit for the initial BSIs that are required by paragraphs g1i through iii of this AD, if you performed those actions before the effective date of this AD
using IAE NMASB V2500ENG72A0706, Revision 1, dated June 28, 2019, or Original Issue, dated February 14, 2019; IAE V2500
Special Instruction SI No. 341F18, dated November 19, 2018; IAE V2500 SI No. 350F
18, Rev. 1, dated December 17, 2018; IAE
V2500 SI No. 356F18, Rev. 1, dated January 9, 2019; IAE V2500 SI No. 372F18, dated
PO 00000

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January 8, 2019; or IAE V2500 Special SI No.
04F19, dated January 14, 2019.
j Definition For the purpose of this AD, an engine shop visit is the induction of the engine into the shop for maintenance involving the separation of pairs of major mating engine flanges, KN, except that the separation of engine flanges solely for the purposes of transportation without subsequent engine maintenance does not constitute an engine shop visit.
k Alternative Methods of Compliance AMOCs 1 The Manager, ECO Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14
CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the certification office, send it to the attention of the person identified in Related Information. You may email your request to: ANE-AD-AMOC@
faa.gov.
2 Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/
certificate holding district office.

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Cycles Since Last Fluorescent Penetrant Inspection CSLFPI