{"id":"F2005L00237","name":"AD/CF34/9 - High Pressure Compressor Forward Spool","slug":"ad-cf34-9-high-pressure-compressor-forward-spool","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":33804,"registerId":"commonwealth-F2005L00237-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"General Electric Turbine Engines - CF34 ","sectionType":"division","heading":"General Electric Turbine Engines - CF34 Series","content":"### General Electric Turbine Engines - CF34 Series\n\n| AD/CF34/9 | High Pressure Compressor Forward Spool | 3/2005 |\n| --------- | -------------------------------------- | ------ |\n\n| Applicability: | GE CF34-3A, CF34-3A2, CF34-1A, CF34-3A1, CF34-3B, and CF34-3B1 series turbofan engines with high pressure compressor (HPC) forward spool, part number (P/N) 6078T56P03 or 6078T56P04, installed.Note 1: These engines are installed on, but not limited to, Bombardier series Business Jet Model CL-600-2A12 (CL- 601), Bombardier series Business Jet Model CL-600-2B16 (CL-601-3A, CL-601-3R, and CL-604), and Bombardier series Regional Jet Model CL- 600-2B19 (Regional Jet Series 100 and 440) aeroplanes.  |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Remove from service HPC forward spools, P/Ns 6078T56P03 and 6078T56P04.2. Do not install any HPC forward spool, P/N 6078T56P03.Do not install any HPC forward spool, P/N 6078T56P04, with more than 0 CSN.Note 2: FAA AD 2004-26-02 Amdt 39-13914 refers.                                                                                                                                                                                                                                                      |\n| Compliance:    | For Requirement 1.For CF34-3B engines: At the first piece-part exposure after 6,000 cycles-since-new (CSN), but no later than 20,000 CSN.For CF34-3A, CF34-3A2, CF34-1A, CF34-3A1, and CF34-3B1 engines: At the first piece-part exposure after 6,000 CSN, but no later than 22,000 CSN.For Requirement 2.After the effective date of this Directive:Definition: For the purpose of this Directive, the definition of piece-part exposure for the HPC forward spool is when the spool is completely disassembled. |\n|                | This Airworthiness Directive becomes effective on 17 March 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                  |\n\n| Background: | This Directive results from an updated low-cycle fatigue (LCF) analysis performed on HPC forward spools, P/Ns 6078T56P03 and 6078T56P04, by GE. We are issuing this AD to prevent LCF cracks and failure of the HPC forward spool, which could result in an uncontained engine failure and damage to the aeroplane. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n4 February 2005","sortOrder":0},{"sectionNumber":"AD/CF34/9","sectionType":"part","heading":"AD/CF34/9","content":"## AD/CF34/9","sortOrder":1},{"sectionNumber":"High Pressure Compressor Forward Spool","sectionType":"part","heading":"High Pressure Compressor Forward Spool","content":"## High Pressure Compressor Forward Spool","sortOrder":2},{"sectionNumber":"3/2005","sectionType":"part","heading":"3/2005","content":"## 3/2005","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive remains narrowly focused on addressing low‑cycle fatigue risk in two specific HPC forward spool part numbers for specified CF34 engine variants. It does not expand beyond that technical purpose (no broader engine design changes, no additional components or unrelated operational restrictions). The measures (removal timing and installation prohibitions) align with the stated safety objective and do not materially broaden the scope beyond preventing spool LCF failure."},"complexity_factors":["Two specific part numbers subject to different installation rules (P/N 6078T56P03 prohibited entirely; P/N 6078T56P04 may only be installed new, CSN = 0).","Multiple engine model variants covered (CF34‑3A, ‑3A2, ‑1A, ‑3A1, ‑3B, ‑3B1) with variant‑specific compliance windows.","Piece‑part exposure concept as the trigger for action (requires operators to track complete disassembly events in addition to CSN).","Different upper CSN deadlines depending on engine model (20,000 CSN vs 22,000 CSN) and a common 6,000 CSN lower threshold tied to first exposure.","Cross‑reference to an FAA Airworthiness Directive (FAA AD 2004‑26‑02), which may require operators to reconcile overlapping requirements.","A single defined term provided (piece‑part exposure) but reliance on industry terms (CSN) that require accurate recordkeeping.","Practical implementation complexity (scheduling full disassembly, sourcing replacement spares) though the legal text itself is short and focused."],"plain_english_summary":"**What this directive does (mechanics)\n\n- Orders the removal from service of specific high pressure compressor (HPC) forward spools used in certain GE CF34 turbofan engines. The affected part numbers are P/N 6078T56P03 and P/N 6078T56P04.\n- Prohibits installing any spool with P/N 6078T56P03. It also prohibits installing any P/N 6078T56P04 spool that has more than 0 cycles‑since‑new (CSN) — in other words, used P/N 6078T56P04 spools may not be fitted.\n- Sets mandatory times for removal tied to a defined event called “piece‑part exposure” (which this directive defines as when the spool is completely disassembled). For all covered engines you must remove the spool at the first complete disassembly that occurs after 6,000 CSN. That removal must occur no later than:\n  - 20,000 CSN for CF34‑3B engines; or\n  - 22,000 CSN for CF34‑3A, CF34‑3A2, CF34‑1A, CF34‑3A1, and CF34‑3B1 engines.\n- The directive took effect on 17 March 2005 and cross‑refers to FAA AD 2004‑26‑02.\n\nWho is affected\n\n- Aircraft operators and maintenance organisations that operate aeroplanes fitted with GE CF34 series engines of the listed variants when those engines have the specified HPC forward spool part numbers installed. The AD notes common aircraft types (Bombardier CL‑600/CL‑601/CL‑604 family and Regional Jet Series 100/440) but applies to the engines wherever installed.\n\nWhy the regulator issued it (official rationale)\n\n- GE performed an updated low‑cycle fatigue (LCF) analysis on these forward spools and identified a risk of LCF cracking. The regulator’s stated purpose is to prevent LCF cracks and consequent spool failure, which could lead to an uncontained engine failure and damage to the aeroplane.\n\nAnalyst’s practical read on incentives, costs, and trade‑offs\n\n- Who pays: aircraft operators and their maintenance providers bear the direct costs — removing and replacing spools, possible purchasing of new spares, maintenance downtime, and recordkeeping. If replacement new spools are in short supply, operators may face increased spare prices or longer aircraft out‑of‑service time.\n- Who decides: the regulator sets the mandatory removal and installation rules; operators decide how and when to schedule disassembly/maintenance within the mandated windows and where to source replacement parts.\n- Behavioural effect on operators: operators must track CSN and piece‑part exposure events closely, plan maintenance to meet the first disassembly after 6,000 CSN, and avoid installing prohibited or used parts. Some operators may increase inspection/disassembly frequency to comply or to rotate spares.\n- Market and competition effects: demand shifts toward new spare spools (P/N 6078T56P04 with 0 CSN) or alternate compliant parts/engines. Independent maintenance organisations and spare suppliers will see demand for compliant new parts and for replacement of scrap/withdrawn spools; supply shortages could raise prices. Contractual relationships with OEMs or parts suppliers may be triggered (warranty, parts availability, exchange programs).\n- Compliance burden and implementation risk: the rule introduces administrative burden (CSN tracking, logging piece‑part exposure), potential scheduling disruption (downtime for complete disassembly), and scrap of removed spools. There is some operational risk if operators misread the “first piece‑part exposure after 6,000 CSN” requirement or miscount CSN. The cross‑reference to the FAA AD means operators who comply with FAA guidance may already meet parts of the requirement, but they must confirm alignment.\n- Trade‑offs: the directive reduces the risk of catastrophic spool failure (safety benefit) at the cost of earlier removal/replacement of spools, spare parts expenditure, and maintenance downtime. The directive is narrowly targeted to particular part numbers and specific engine models; it does not mandate inspections or changes on other engine components.\n\nKey reference points in the directive\n\n- Affected parts: P/N 6078T56P03 and 6078T56P04 (Requirement 1).\n- Installation prohibitions: do not install any P/N 6078T56P03; do not install any P/N 6078T56P04 with CSN > 0 (Requirement 2).\n- Timing for removal: first piece‑part exposure after 6,000 CSN, but no later than 20,000 or 22,000 CSN depending on engine model (Compliance section).\n- Definition: piece‑part exposure = spool completely disassembled (Compliance section).\n\nBottom line: This Airworthiness Directive mandates removal and disposal/replacement controls for two specific HPC forward spool part numbers on particular CF34 engine models, on the basis of updated low‑cycle fatigue analysis. The safety benefit (reducing risk of LCF cracks and uncontained failure) must be implemented by operators through scheduled disassembly, parts replacement, recordkeeping and likely spare‑parts procurement."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, targeted Airworthiness Directive addressing a specific safety defect identified in particular engine components. The scope remains precisely limited to the identified part numbers and engine models, consistent with the original purpose of preventing catastrophic engine failure."},"complexity_factors":["Technical aviation terminology throughout (turbofan, high-pressure compressor, cycles-since-new, piece-part exposure)","Multiple specific part numbers (P/N 6078T56P03, 6078T56P04) and engine model variants requiring careful cross-referencing","Tiered compliance deadlines based on engine sub-model (20,000 CSN vs 22,000 CSN)","Conditional installation prohibition with usage threshold (0 CSN for P/N 6078T56P04)","Requires understanding of maintenance concepts like 'piece-part exposure' (defined in the document as complete disassembly)","Reference to foreign regulation (FAA AD 2004-26-02) for additional context"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's aviation regulator (CASA) that requires specific maintenance actions on certain aircraft engines.\n\n**What it does:**\n- **Orders the removal** of specific high-pressure compressor forward spools (critical engine parts) from General Electric CF34 turbofan engines\n- **Bans installation** of these parts once they've been used beyond certain limits\n\n**Who it affects:**\n- Owners and operators of aircraft with GE CF34-3A, CF34-3A2, CF34-1A, CF34-3A1, CF34-3B, and CF34-3B1 series engines\n- Specifically affects Bombardier business jets (CL-601, CL-604) and regional jets (Series 100 and 440)\n\n**Why it matters:**\n- GE discovered through updated fatigue analysis that these parts can develop cracks due to repeated stress cycles (called \"low-cycle fatigue\")\n- If the spool fails, it could cause an \"uncontained engine failure\" — where engine parts break apart and potentially damage the aircraft or injure passengers\n- This is a **safety-critical mandate** — compliance is legally required, not optional\n\n**Key deadlines:**\n- Parts must be removed when the engine is next disassembled for maintenance after 6,000 flight cycles, but absolutely no later than 20,000–22,000 cycles depending on engine model\n- No new installations of the banned part numbers allowed after March 17, 2005"}},"importantCases":[],"_links":{"self":"/api/acts/ad-cf34-9-high-pressure-compressor-forward-spool","history":"/api/acts/ad-cf34-9-high-pressure-compressor-forward-spool/history","analysis":"/api/acts/ad-cf34-9-high-pressure-compressor-forward-spool/analysis","conflicts":"/api/acts/ad-cf34-9-high-pressure-compressor-forward-spool/conflicts","importantCases":"/api/acts/ad-cf34-9-high-pressure-compressor-forward-spool/important-cases","documents":"/api/acts/ad-cf34-9-high-pressure-compressor-forward-spool/documents"}}