{"id":"F2005L03542","name":"AD/AL 250/88 - Third-stage Turbine Wheel Seal Joint","slug":"ad-al-250-88-third-stage-turbine-wheel-seal-joint","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":39044,"registerId":"commonwealth-F2005L03542-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 250/88 | Third-stage Turbine Wheel Seal Joint | 13/2005 |\n| ------------ | ------------------------------------ | ------- |\n\n| Applicability: | Rolls-Royce Corporation (RRC) (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) models 250-C28, -C28B, and -C28C turboshaft engines fitted with third stage turbine wheel part number (P/N) 6899383.Note 1: These engines are installed on, but not limited to, Bell Helicopter Textron 206L-1; Eurocopter Deutschland BO 105 LS A-1; and Eurocopter CanadaBO 105 LS A-3 helicopters.                                                                                                                                 |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Unless previously accomplished in accordance with Rolls Royce RRC Alert Service Bulletin No. CEB-A-72-2205 dated 26 April 2005, remove the third-stage turbine wheel and perform a one-time visual inspection of the seal joint in each passage between airfoils at the hub and shroud. Seal joint evidence must not be present within blade fillet radii. See Figure 1 of this AD for reference.2. Remove from service any turbine wheel that has seal joint evidence present within the blade fillet radii.Note 2: FAA AD 2005-20-11 Amdt 39-14305 refers. |\n| Compliance:    | 1. For third-stage turbine wheels, with fewer than 3,000 hours time-since-new (TSN), inspect the next time the third-stage turbine wheel is directly available for removal, at the next turbine overhaul, or by 30 April 2007, whichever occurs sooner.For third-stage turbine wheels, with 3,000 hours or more TSN, inspect within 300 hours or by 30 April 2007, whichever occurs sooner.2. Before further flight after the effective date of this AD.                                                                                                        |\n\n|             | This Airworthiness Directive becomes effective on 22 December 2005.                                                                                                                                                                                               |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Background: | This AD results from FAA reports of three failed third-stage turbine wheels and from the manufacturer's analysis of those failures. This AD is intended to prevent loss of power and uncommanded engine shutdown due to failure of the third-stage turbine wheel. |\n\n![](image.002.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n10 November 2005","sortOrder":0},{"sectionNumber":"AD/AL 250/88","sectionType":"part","heading":"AD/AL 250/88","content":"## AD/AL 250/88","sortOrder":1},{"sectionNumber":"Third-stage Turbine Wheel Seal Joint","sectionType":"part","heading":"Third-stage Turbine Wheel Seal Joint","content":"## Third-stage Turbine Wheel Seal Joint","sortOrder":2},{"sectionNumber":"13/2005","sectionType":"part","heading":"13/2005","content":"## 13/2005","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":false,"description":"Based solely on the text provided, the directive sets specific inspection and removal requirements for the identified wheels and engines. The document does not indicate a broadened or narrowed scope from any earlier instrument; it appears to clarify and mandate inspection/removal for the specified part and models."},"complexity_factors":["Narrow technical scope: targets a single part (third‑stage turbine wheel P/N 6899383) on specified 250‑C28 engine models.","Inspection detail: requires visual inspection for ‘seal joint evidence within blade fillet radii’, which is a technically specific inspection criterion.","Tiered compliance timing: different deadlines based on time‑since‑new (TSN) thresholds (<3,000 hours vs ≥3,000 hours) and event triggers (next removal, overhaul, or fixed date).","Operational impact: may force unscheduled removals, engine downtime and replacement of wheels found non‑compliant.","Reference dependencies: compliance may be satisfied by following a named Rolls‑Royce Alert Service Bulletin and references an FAA AD, adding cross‑document obligations.","Clear remedial action: removal from service is mandatory for any wheel with the defect, creating immediate asset disposal/replacement costs."],"plain_english_summary":"This Airworthiness Directive requires operators to remove the third-stage turbine wheel and carry out a one‑time visual check of the seal joint between the blade airfoils at the hub and shroud, and to withdraw from service any wheel that shows seal joint evidence within the blade fillet radii. It applies to Rolls‑Royce (Allison) 250‑C28 series turboshaft engines fitted with turbine wheel P/N 6899383 used on certain helicopters. The action is intended to prevent loss of power and uncommanded engine shutdown following reported wheel failures."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains focused scope on its original safety purpose. It addresses a specific manufacturing defect in a single turbine wheel part number, triggered by three reported failures. The requirements remain tightly bounded to visual inspection and replacement of the defective component, without expanding into broader operational restrictions or additional engine systems."},"complexity_factors":["Single, specific mechanical defect addressed (seal joint in one turbine wheel part number)","Straightforward two-part requirement: inspect, then remove if defective","Clear applicability criteria (three specific engine models, one part number)","Simple conditional compliance structure based only on flight hours (TSN threshold of 3,000 hours)","Minimal cross-referencing (only one FAA AD and one manufacturer service bulletin mentioned)","No nested exceptions or complex definitional sections","Visual reference to single figure (Figure 1) for inspection guidance"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspection and, if necessary, removal and replacement of Rolls‑Royce (Allison) 3rd‑stage turbine wheels (P/N 6899383) because a manufacturing defect in the seal joint can crack where blade meets wheel. Owners/operators of affected 250‑C28/C28B/C28C engines (used on certain Bell and Eurocopter helicopters) must inspect on the stated hour limits and ground any wheel with defects before next flight. It responds to multiple in‑service failures that risk sudden engine loss."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-88-third-stage-turbine-wheel-seal-joint","history":"/api/acts/ad-al-250-88-third-stage-turbine-wheel-seal-joint/history","analysis":"/api/acts/ad-al-250-88-third-stage-turbine-wheel-seal-joint/analysis","conflicts":"/api/acts/ad-al-250-88-third-stage-turbine-wheel-seal-joint/conflicts","importantCases":"/api/acts/ad-al-250-88-third-stage-turbine-wheel-seal-joint/important-cases","documents":"/api/acts/ad-al-250-88-third-stage-turbine-wheel-seal-joint/documents"}}