{"id":"F2005L01741","name":"AD/AL 250/87 - Containment Ring","slug":"ad-al-250-87-containment-ring","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":35818,"registerId":"commonwealth-F2005L01741-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Allison Turbine Engines - 250 Series","sectionType":"division","heading":"Allison Turbine Engines - 250 Series","content":"### Allison Turbine Engines - 250 Series\n\n| AD/AL 250/87 | Containment Ring | 8/2005 |\n| ------------ | ---------------- | ------ |\n\n| Applicability: | Rolls-Royce Corporation (RRC) (formerly Allison Engine Company) 250-B17B,-B17C, -B17D, -B17E, -C20, -C20B, -C20F, -C20J, -C20S and -C20W turboprop and turboshaft engines that do not have turbine energy absorbing ring part number (P/N) 23035175, or an equivalent approved serviceable turbine energy absorbing ring installed.                                                                                      |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | Unless previously accomplished, install a turbine energy absorbing ring, RRC P/N 23035175, or an equivalent approved turbine energy absorbing ring, in the plane of the 1st stage turbine wheel, using paragraphs 1.M., 2.A. and 2.B. of Rolls-Royce Corporation Alert Commercial Engine Bulletin No. CEB-A-1255, Revision 4 dated 29 September 2004 to do the installation.Note: FAA AD 2005-10-13Amdt 39-14090 refers. |\n| Compliance:    | At the next time the gas producer turbine rotor is disassembled for any reason, or within 1,750 hours time-since-last overhaul, time since-new, time-since-last-heavy-maintenance, or time-since-last-hot section inspection after the effective date of this Directive, whichever occurs first, but no later than 31 October 2011.                                                                                      |\n|                | This Airworthiness Directive becomes effective on 4 August 2005.                                                                                                                                                                                                                                                                                                                                                         |\n| Background:    | This Directive is in response to an unacceptable rate of uncontained 1st stage turbine wheel failures. The fitment of the energy absorbing ring is designed to minimize the risk of uncontained 1st stage turbine wheel fragments from causing damage to the aircraft, which could lead to loss of control and loss of the aircraft.                                                                                     |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n24 June 2005","sortOrder":0},{"sectionNumber":"AD/AL 250/87","sectionType":"part","heading":"AD/AL 250/87","content":"## AD/AL 250/87","sortOrder":1},{"sectionNumber":"Containment Ring","sectionType":"part","heading":"Containment Ring","content":"## Containment Ring","sortOrder":2},{"sectionNumber":"8/2005","sectionType":"part","heading":"8/2005","content":"## 8/2005","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in specific engine models. The scope remains tightly focused on the original safety issue (uncontained turbine wheel failures) and the mandated remedy (energy absorbing ring installation). No evidence of scope creep or expansion beyond the original safety purpose."},"complexity_factors":["Single, specific mechanical requirement (install one part)","Clear applicability table listing exact engine models by part number","Straightforward compliance timeline with 'whichever occurs first' logic (three triggers plus absolute deadline)","Only one cross-reference (to FAA AD 2005-10-13 and Rolls-Royce service bulletin)","No defined terms section — technical terms (turboshaft, time-since-last-overhaul) are industry standard","Short document (approximately 250 words of substantive content)","Single background rationale with clear safety purpose"],"plain_english_summary":"This AD mandates installation of a turbine energy-absorbing ring (P/N 23035175 or approved equivalent) on specified Rolls‑Royce/Allison 250-series engines if not already fitted. It affects listed 250‑B17 and 250‑C20 variants and is legally required.\n\nOperators must fit the ring at the next gas‑producer turbine rotor disassembly or within 1,750 operating hours (from overhaul/new/hot‑section inspection), whichever is sooner, and no later than 31 Oct 2011, to contain turbine wheel fragments and prevent catastrophic damage."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive stays within the original technical corrective action: it mandates fitting an energy absorbing ring to mitigate uncontained 1st stage turbine wheel failures for the specified engine models. The instrument does not expand the affected fleet beyond the listed models, nor introduce unrelated regulatory obligations. Its mechanics — a specified part or equivalent, installation per manufacturer's bulletin, and time‑bound compliance — align with the stated safety objective and do not materially broaden scope beyond that corrective purpose."},"complexity_factors":["Single clear technical requirement (install P/N 23035175 or approved equivalent) reduces legal complexity","Applicability lists 10 specific engine model variants (requires correct identification of engine model)","Compliance timing uses multiple conditional triggers: next rotor disassembly OR within 1,750 hours measured by several time metrics OR whichever occurs first, but no later than a calendar date","References external technical material for installation procedure (Rolls‑Royce CEB‑A‑1255 Rev 4, paragraphs 1.M., 2.A., 2.B.)","Allows 'equivalent approved' parts, which introduces a regulatory approval step and potential administrative complexity","Cross‑references an FAA AD (FAA AD 2005‑10‑13Amdt 39‑14090), increasing cross‑jurisdictional sourcing of compliance guidance"],"plain_english_summary":"**What this instrument does (in simple terms)**\n\n- **Requires** that a particular safety part — a turbine energy absorbing ring (Rolls‑Royce Corporation part number 23035175, or an equivalent approved ring) — be fitted in the plane of the 1st stage turbine wheel on specified Allison (now Rolls‑Royce Corporation) 250 series engines. (A turbine energy absorbing ring is designed to catch or slow fragments if the 1st stage turbine wheel fails.)\n\n**Who this affects**\n\n- Owners, operators and maintenance organisations that operate or service the listed Allison/ RRC 250‑series turboprop and turboshaft engines: 250‑B17B, ‑B17C, ‑B17D, ‑B17E, ‑C20, ‑C20B, ‑C20F, ‑C20J, ‑C20S and ‑C20W (see \"Applicability\").\n\n**What must be done and when**\n\n- If not already fitted, install RRC P/N 23035175 (or an equivalent approved turbine energy absorbing ring) in the plane of the 1st stage turbine wheel, following the specified paragraphs (1.M., 2.A. and 2.B.) of Rolls‑Royce Corporation Alert Commercial Engine Bulletin No. CEB‑A‑1255 Revision 4 (29 September 2004). (The AD cross‑references that manufacturer bulletin for the installation procedure.)\n- Timing: fit the ring at the next time the gas‑producer turbine rotor is disassembled for any reason, or within 1,750 flight hours (counting several relevant time metrics such as time‑since‑new, time‑since‑last‑overhaul, time‑since‑last‑heavy‑maintenance, or time‑since‑last‑hot‑section inspection) after the directive’s effective date — whichever occurs first — but in any event no later than the specified calendar date. (The AD gives specific calendar and hour limits in its Compliance paragraph.)\n\n**Why the rule exists (stated reason)**\n\n- The directive responds to an unacceptable rate of uncontained failures of the 1st stage turbine wheel. The energy absorbing ring is intended to reduce the risk that turbine wheel fragments escape the engine casing and damage the aircraft.\n\n**Practical mechanics and compliance effects (testing the stated purpose)**\n\n- Who pays: operators or their contracted maintenance providers must buy the ring (unless already fitted) and perform the installation. The AD names a specific OEM part number (RRC P/N 23035175), but allows \"equivalent approved\" rings — which requires an approval process (normally by the regulator or a certificated design/alteration approval). This creates direct parts and labour costs and a small administrative approval cost where an alternative part is proposed.\n\n- When it happens: the rule ties the modification to a natural maintenance milestone (next rotor disassembly) or a defined hours limit. That lowers immediate downtime cost compared with forcing an out‑of‑cycle shop visit, but still imposes an upper bound on when the retrofit must occur.\n\n- Implementation risk and compliance burden: compliance requires following the manufacturer’s bulletin paragraphs for installation. Incorrect installation or incomplete paperwork could negate the safety benefit and expose the operator to enforcement. Maintenance organisations must retain records showing the P/N fitted or the approval for an equivalent.\n\n- Market and competition effects: specifying an OEM part number concentrates initial demand on the OEM (RRC) for that ring. Allowing \"equivalent approved\" parts reduces that concentration in principle, but only to the extent equivalents are approved and available. This may advantage maintenance providers who already source parts from RRC and may raise aftermarket demand for the approved ring.\n\n- Who decides: approval of alternative parts or equivalency normally sits with the regulator (or their delegated approvals) under the AD and civil aviation rules; maintenance organisations decide when to schedule the work within the AD’s timing constraints.\n\n- Substitution effects and unintended consequences: operators may defer the work until a scheduled major maintenance to save cost (consistent with the AD’s timing). If parts supply is limited, some operators could face maintenance schedule disruption. The AD itself does not require a single supplier but the P/N reference tends to channel initial demand.\n\n**Summary of trade‑offs and opportunity costs**\n\n- The AD trades immediate parts and labour expense and potential scheduling inconvenience for reduced risk of uncontained turbine wheel fragments. The main opportunity cost is workshop capacity and maintenance budget that will be used for this retrofit instead of other work during a maintenance cycle.\n\n(References in the text: \"Applicability\", \"Requirement\", \"Compliance\" and \"Background\" paragraphs of the Directive.)"},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-87-containment-ring","history":"/api/acts/ad-al-250-87-containment-ring/history","analysis":"/api/acts/ad-al-250-87-containment-ring/analysis","conflicts":"/api/acts/ad-al-250-87-containment-ring/conflicts","importantCases":"/api/acts/ad-al-250-87-containment-ring/important-cases","documents":"/api/acts/ad-al-250-87-containment-ring/documents"}}