{"id":"F2006B08689","name":"AD/CT7/5 - Rotor Parts","slug":"ad-ct7-5-rotor-parts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51848,"registerId":"commonwealth-F2006B08689-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CT7/5 - Rotor Parts","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nGeneral Electric Turbine Engines \\- CT7 Series\n\nAD/CT7/5 Rotor Parts 5/94 Applicability: CT7-5A2,-7A and -9C turboprop engines; and CT7-2A and -6 turboshaft engines. Requirement: Action in accordance with GE Service bulletins:\n\nFor CT7-5A2, \\-7A and \\-9C: SB A72-252 of 31 Aug 1990\\. For CT7-2A: SB A72-18 of 10 Sep1990.\n\nFor CT7-6: SB A72-17 of 10 Sep 1990.\n\nNote: FAA AD 93-25-17 refers.\n\nCompliance: Before exceeding the \\`Max total allowable cycles' specified in the relevant Service Bulletins.\n\nBackground: This AD requires the removal from service of certain gas generator rotor assembly parts that were plasma sprayed during manufacture . The requirement arises from results obtained during material testing which indicated that the plasma-spray process reduces the low cycle fatigue capability of the material.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in specific engine models. It has not expanded beyond its original purpose of mandating removal of plasma-sprayed rotor parts."},"complexity_factors":["Short, single-purpose directive (approximately 150 words)","Only 5 specific engine models affected, clearly listed","Simple conditional structure: identify engine type → apply relevant Service Bulletin → comply before cycle limit","No defined terms section (relies on external Service Bulletins for technical specifications)","Single cross-reference to FAA AD 93-25-17 for additional context","No nested exceptions or complex procedural requirements"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific **General Electric CT7 aircraft engines** used in planes and helicopters.\n\n**What it does:**\n- Requires operators to remove certain **rotor parts** (spinning components inside the engine) from service before they reach a maximum number of flight cycles.\n- These parts were treated with a manufacturing process called **\"plasma spraying\"** (coating metal with a protective layer using superheated gas).\n- Testing revealed this process weakens the metal, making it more likely to crack under repeated stress (**low cycle fatigue** — damage from repeated heating/cooling and pressure changes during flights).\n\n**Who it affects:**\n- Owners and operators of aircraft with CT7-5A2, CT7-7A, CT7-9C (turboprop engines — used in propeller aircraft), or CT7-2A, CT7-6 (turboshaft engines — used in helicopters).\n- Maintenance organisations servicing these engines.\n\n**Why it matters:**\n- **Safety critical.** Fatigue failures in engine rotors can cause catastrophic engine failure, potentially leading to loss of aircraft and life.\n- The directive mandates compliance before a specific flight cycle limit, preventing parts from failing in service.\n\n**What operators must do:**\n- Follow specific General Electric Service Bulletins (technical instructions) for their engine model.\n- Track \"total allowable cycles\" (how many times the engine has started, run, and shut down) and remove parts before exceeding the limit."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's operative scope (remove specified plasma‑sprayed gas generator rotor parts from service on the listed CT7 engine models before they exceed the service‑bulletin \"Max total allowable cycles\") matches the stated technical reason in the Background (material testing showing reduced low cycle fatigue). The AD confines action to the listed engine models and delegates procedural detail and cycle thresholds to the referenced GE service bulletins (Requirement; Compliance; Background). No change of scope beyond that stated in the instrument is indicated by the text supplied."},"complexity_factors":["Specific and limited applicability to five CT7 engine variants reduces scope complexity (Applicability).","Mandates following multiple manufacturer service bulletins (different SB numbers/dates per model), requiring operators to consult external documents for procedural detail (Requirement).","Compliance timing tied to a measured parameter — the \"Max total allowable cycles\" in the service bulletins — requires accurate tracking of part cycles (Compliance).","Identification of affected parts depends on knowing whether parts were plasma‑sprayed during manufacture, which may require record checks or inspection (Background).","Cross‑reference to an FAA AD implies coordination with an external regulator but does not add procedural detail within this AD (Note)."],"plain_english_summary":"What this instrument does (mechanics)\n\n- Requires removal from service certain gas generator rotor assembly parts that were plasma‑sprayed during manufacture. (Requirement; Background)\n- Applies to owners/operators of specific General Electric CT7 engine models: CT7-5A2, -7A, -9C (turboprop), and CT7-2A, -6 (turboshaft). (Applicability)\n- Directs operators to carry out the removals in accordance with the GE service bulletins listed for each engine model (specific bulletin numbers and dates are given). (Requirement)\n- Sets the timing: the parts must be removed before they exceed the “Max total allowable cycles” specified in the relevant GE service bulletins. (Compliance)\n- Notes a cross-reference to FAA Airworthiness Directive 93-25-17. (Note)\n\nWhy it matters (stated rationale and practical consequences)\n\n- The stated technical reason is that material testing indicated the plasma‑spray manufacturing process reduces the material’s low cycle fatigue capability for the affected parts. That is the safety concern the directive targets. (Background)\n\nWho is affected and who decides\n\n- Who must act: aircraft owners/operators that operate the listed CT7 engine models must remove the specified rotor parts in accordance with the listed GE service bulletins and before the parts exceed the cycle limits. (Applicability; Requirement; Compliance)\n- Who sets the action: the Civil Aviation Safety Authority issues the airworthiness directive and the detailed removal/inspection/replacement procedures are those set out in the GE service bulletins referenced by this AD. (Requirement)\n\nImmediate compliance and operational mechanics\n\n- The AD does not itself give detailed removal or replacement steps; it requires operators to follow the referenced GE service bulletins for the exact procedures and the “Max total allowable cycles” thresholds that trigger removal. (Requirement; Compliance)\n- Operators must therefore track part service cycles and identify which rotor assembly parts were plasma‑sprayed during manufacture in order to determine compliance timing. (Background; Compliance)\n\nCosts, incentives and implementation considerations (mechanical, source‑grounded)\n\n- Direct compliance cost and operational burden fall on owners/operators: they must identify affected parts, schedule removals before the specified cycle limits, and carry out whatever replacement or repair the service bulletins require. (Applicability; Requirement; Compliance)\n- The AD ties mandatory action to the manufacturer’s service bulletins, which concentrates procedural discretion over inspection/removal methods and cycle thresholds with the bulletin authors (GE), subject to the AD’s requirement to follow those bulletins. (Requirement)\n- Operators need accurate cycle tracking and parts‑identification (to know which parts were plasma sprayed). That creates administrative and inspection burdens not detailed in the AD itself but implied by the requirement to comply with the service bulletins and the cycle limits. (Background; Compliance)\n- The AD cross‑references an FAA AD, implying alignment with a related foreign regulator’s corrective action; the AD itself relies on service bulletins and cycle limits for precise implementation. (Note; Requirement)\n\nTrade‑offs and risks (implementation‑focused)\n\n- The AD addresses a materials performance risk identified by testing (reduced low cycle fatigue) by removing potentially affected parts before a cycle limit. (Background; Compliance)\n- The AD creates operational choices for operators: they must allocate maintenance windows and cost to remove/replace parts earlier than they otherwise might have, and they must rely on manufacturer guidance for technical steps. (Requirement; Compliance)\n- The AD does not specify replacement part availability, alternative repairs, or compensatory options; those practical details are left to the service bulletins and operator maintenance planning. (Requirement)\n\nSource citations: Applicability; Requirement (service bulletin numbers and dates); Compliance (timing tied to \"Max total allowable cycles\"); Background (plasma spray and test results); Note (FAA AD reference)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ct7-5-rotor-parts","history":"/api/acts/ad-ct7-5-rotor-parts/history","analysis":"/api/acts/ad-ct7-5-rotor-parts/analysis","conflicts":"/api/acts/ad-ct7-5-rotor-parts/conflicts","importantCases":"/api/acts/ad-ct7-5-rotor-parts/important-cases","documents":"/api/acts/ad-ct7-5-rotor-parts/documents"}}