{"id":"F2007L01339","name":"AD/CFM56/26 - Low Pressure Turbine Rear Frame Life","slug":"ad-cfm56-26-low-pressure-turbine-rear-frame-life","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":65568,"registerId":"commonwealth-F2007L01339-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"CFM International Turbine Engines - CFM5","sectionType":"division","heading":"CFM International Turbine Engines - CFM56 Series","content":"### CFM International Turbine Engines - CFM56 Series\n\n| AD/CFM56/26 | Low Pressure Turbine Rear Frame Life | 7/2007 TX |\n| ----------- | ------------------------------------ | --------- |\n\n| 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.                                                                                                                                                                                                                                                                                                        |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| 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/N340-166-205-0, 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/B72-0579 revision 1, or later NAA approved revision.Note 2: EASA AD 2007-0104 dated 17 April 2007 refers. |\n| Compliance:    | 1. Within 7 days from the effective date of this AD.2. Within 300 flight cycles from the effective date of this AD.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |\n|                | This Airworthiness Directive becomes effective on 11 May 2007.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |\n\n| 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. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nCharles Lenarcic  \nDelegate of the Civil Aviation Safety Authority\n\n8 May 2007","sortOrder":0},{"sectionNumber":"AD/CFM56/26","sectionType":"part","heading":"AD/CFM56/26","content":"## AD/CFM56/26","sortOrder":1},{"sectionNumber":"Low Pressure Turbine Rear Frame Life","sectionType":"part","heading":"Low Pressure Turbine Rear Frame Life","content":"## Low Pressure Turbine Rear Frame Life","sortOrder":2},{"sectionNumber":"7/2007 TX","sectionType":"part","heading":"7/2007 TX","content":"## 7/2007 TX","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. Before this AD the LPT rear frames were not subject to a mandatory life limit or mandatory inspection (Background). The AD introduces formal LCF life limits and requires either removal/replacement or inspections where cycle history is unknown (Requirement 1–2), thereby expanding mandatory maintenance scope and record‑keeping obligations for affected operators."},"complexity_factors":["Cross-references to external technical documents: CFM56-7B ESM revision 33 (Requirement 1) and CFM56-7B Service Bulletin S/B72-0579 revision 1 (Requirement 2).","Multiple specified part numbers and engine variants in Applicability increase tracking and applicability checks.","Record‑keeping verification burden when accumulated cycles cannot be established — triggers mandatory removal/replace or inspections (Requirement 2).","Short, dual compliance windows: immediate action within 7 days and corrective action within 300 flight cycles (Compliance).","Regulatory discretion over later revisions requires National Airworthiness Authority (NAA) approval for referenced document updates (Requirement 1).","Operational and cost impact from potential removals/replacements and additional inspections (Requirement 2; Background)."],"plain_english_summary":"This Airworthiness Directive requires operators of CFM56-7B engines fitted with the listed low-pressure turbine (LPT) rear frame part numbers to comply with newly established low-cycle fatigue (LCF) life limits in the CFM56-7B Engine Shop Manual (rev 33 or later). If the accumulated flight cycles for a rear frame cannot be verified, the part must be removed and replaced or inspected per the specified service bulletin.\n\nIt affects airlines and maintenance organisations using those engines, creating short compliance deadlines and imposing record‑keeping, inspection or replacement costs."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope. It addresses a specific safety-critical component (LPT rear frame) with targeted life limits, exactly as intended when the fatigue issue was identified. No scope creep is evident."},"complexity_factors":["Single, narrow technical scope focused on one engine component family","Only 6 specific part numbers affected, clearly listed","Two straightforward compliance pathways: life limit compliance OR inspection/replacement","Minimal cross-referencing (only to manufacturer manuals ESM revision 33 and Service Bulletin 72-0579)","Simple binary compliance timeline (7 days for paperwork, 300 cycles for physical action)","No nested exceptions or conditional logic — requirements apply uniformly to all affected parts","Background clearly explains technical rationale without legal obfuscation"],"plain_english_summary":"This AD imposes mandatory life limits on the Low Pressure Turbine (LPT) rear frame in certain CFM56-7B engines (Boeing 737), after discovery of low-cycle fatigue cracks that could cause engine failure. \n\nOperators must update maintenance records and, within 300 flight cycles, either remove unknown-history parts or inspect/retire frames per the manufacturer to prevent unsafe failures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cfm56-26-low-pressure-turbine-rear-frame-life","history":"/api/acts/ad-cfm56-26-low-pressure-turbine-rear-frame-life/history","analysis":"/api/acts/ad-cfm56-26-low-pressure-turbine-rear-frame-life/analysis","conflicts":"/api/acts/ad-cfm56-26-low-pressure-turbine-rear-frame-life/conflicts","importantCases":"/api/acts/ad-cfm56-26-low-pressure-turbine-rear-frame-life/important-cases","documents":"/api/acts/ad-cfm56-26-low-pressure-turbine-rear-frame-life/documents"}}