{"id":"F2006B02287","name":"AD/AL 250/78 - Superior Turbine Bearings","slug":"ad-al-250-78-superior-turbine-bearings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41517,"registerId":"commonwealth-F2006B02287-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/78 - Superior Turbine Bearings","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)  \nAllison Turbine Engines \\- 250 Series\n\nAD/AL 250/78 Superior Turbine Bearings 13/96\n\nApplicability: All Allison Model 250-B15G, \\-B17F, \\-B17F/1, \\- B17F/2, \\-C18, \\-C18A, \\-C18B, \\- C18C, -C20, -C20B, -C20F, -C20J, -C20S, -C20W, -C20R, -C20R/1, -C20R/2, -\n\nC20R/4, \\-C28B, \\-C28C, \\-C30, \\-C30P, \\-C30M, \\-C30S and C30G turbine engines fitted with Superior Air Parts Inc. Parts Manufacturing Approval (PMA) bearings part number (P/N) A6871505 and/or P/N A23007152.\n\nNote 1: This directive is only applicable to Allison 250 turboprop and turboshaft engines fitted with bearings manufactured by Superior Air Parts Inc.\n\nRequirement: 1: Engines fitted with a Superior Air Parts Inc. No. 5 bearing P/N A6871505:\n\n    Perform a visual inspection of the engine oil filters in accordance with (IAW) Superior Turbine Service Bulletin No. T95-SB001 Revision A.\n\n    b. Replace Superior Air Parts Inc. bearing P/N A6871505 with an Allison Engine Company bearing P/N 6871505.\n\n2: Engines fitted with a Superior Air Parts Inc. No. 8 bearing P/N A23007152:\n\na. Perform a visual inspection of the engine oil filters IAW Superior Turbine Service Bulletin No. T95-SB002 Revision A.\n\nReplace Superior Air Parts Inc. No. 8 bearing P/N A23007152 with an Allison Engine Company bearing P/N 23031478.\n\nNote 2: FAA Airworthiness Directive 96-19-01 refers.\n\nNote 3: Replacement of the Superior Air Parts Inc. bearings with Allison Engine Company bearings constitutes a terminating action for this directive.\n\nCompliance: 1. a. Prior to 31 December 1996 and thereafter at intervals not to exceed 25 hours’ time in service for engines with less than 300 hours’ time in service since installation of the subject bearing and thereafter at intervals not to exceed 100 hours’ time in service.\n\n    b. At next access to the affected bearing.\n\n    2. a. Prior to 31 December 1996 and thereafter at intervals not to exceed 25 hours’ time in service for engines with less than 300 hours’ time in service since installation of the subject bearing and thereafter at intervals not to exceed 100 hours’ time in service.\n\n2. b. At next access to the affected bearing.\n\nThis Airworthiness Directive becomes effective on 5 December 1996.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nBackground: This directive has been issued to require the inspection and replacement of certain turbine bearings. The requirement follows reports of premature wear and failures of the applicable bearings. Bearing failure could result in turbine and subsequently, engine failure.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive sticks to its original safety‑focused purpose: require inspection and replacement of specific aftermarket bearings that were reported to wear prematurely. It does not broaden regulatory scope beyond that technical remedy: it prescribes inspections, specifies OEM replacement parts as the terminating action, and sets compliance intervals. It therefore does not appear to have grown beyond its original intent; the replacement provision actually narrows ongoing burden by providing a terminating action."},"complexity_factors":["Narrow applicability: specific list of Allison Model 250 sub‑models and two discrete PMA part numbers (limited universe)","Two parallel requirement streams (No. 5 bearing and No. 8 bearing) with identical structure (inspect then replace)","Conditional inspection intervals tied to hours‑since‑installation (<300 hours → 25‑hour checks; otherwise 100‑hour checks)","‘At next access’ replacement timing creates operational variability","External cross‑references: two Superior Turbine Service Bulletins (T95‑SB001 Rev A and T95‑SB002 Rev A) and an FAA AD (96‑19‑01)","Terminates on replacement (explicit terminating action reduces ongoing requirements once replacement done)","Simple number of defined part numbers and plain actions (visual inspection and specific OEM replacement)","Fixed effective date and historic compliance timeline (adds legacy timing element but no ongoing regulatory branching)"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- It requires inspections and, in many cases, replacement of specific aftermarket (PMA) turbine bearings made by Superior Air Parts Inc. that are fitted to certain Allison Model 250 turboshaft/turboprop engines.\n- Two particular bearing part numbers are targeted: Superior P/N A6871505 (No. 5 bearing) and Superior P/N A23007152 (No. 8 bearing).\n- For each affected bearing the directive requires:\n  - A visual inspection of the engine oil filters in accordance with the referenced Superior Turbine Service Bulletins (T95-SB001 Rev A for the No. 5 bearing; T95-SB002 Rev A for the No. 8 bearing). (Requirement 1.a and 2.a)\n  - Replacement of the Superior bearing with a specific Allison Engine Company bearing (P/N 6871505 for the No. 5 position; P/N 23031478 for the No. 8 position). (Requirement 1.b and 2.b)\n- Replacing the Superior bearings with the Allison-engineered parts is stated to be a terminating action — once replaced, the ongoing inspection requirement for that bearing no longer applies. (Note 3)\n- The AD sets compliance timing: initial inspections were required prior to 31 December 1996, then at 25‑hour intervals while the bearing has less than 300 hours since installation and thereafter at 100‑hour intervals; replacement must occur at the next access to the affected bearing. (Compliance)\n- The directive became effective on 5 December 1996. The issuing authority cites reports of premature wear and failures of the Superior bearings and states bearing failure could lead to turbine and engine failure (Background).\n\n**Who this affects**\n\n- Aircraft operators and owners who have Allison 250 series engines fitted with the specified Superior Air Parts bearings.\n- Approved maintenance organisations (MROs) and mechanics who must perform the inspections and replacements.\n- Parts suppliers and distributors: Superior Air Parts (the PMA supplier) and Allison Engine Company (the OEM whose replacement bearings are mandated).\n- Regulators and continued airworthiness approval bodies who monitor compliance.\n\n**Why it matters (risks, incentives, costs and trade-offs)**\n\n- Safety goal stated: the AD addresses reports of premature bearing wear/failure that can lead to turbine and engine failure (Background). Mechanically, the AD reduces the probability of in‑flight engine failure by mandating inspection and replacement of suspect bearings.\n\n- Who pays: direct costs fall on operators — labour for inspections, potential unscheduled maintenance access, and the cost of replacement parts (Allison bearings) and fitment. Downline costs include aircraft downtime and any recordkeeping required by the operator/MRO.\n\n- Behavioural incentives created:\n  - Operators have an incentive to replace the Superior bearings with the Allison parts because replacement is a stated terminating action and ends the frequent inspection burden (Note 3; Requirement 1.b and 2.b). That creates a trade-off between paying replacement cost now versus continuing to incur repeated inspection cost and increased operational risk.\n  - If Allison bearings are scarce or costly, some operators may defer replacement and accept the higher inspection frequency (25 hours while <300 hours since installation) to keep flying, which increases maintenance activity and administrative overhead.\n\n- Effects on competition and supply:\n  - The AD effectively requires use of OEM Allison bearings as the compliance remedy. That reduces the practical interchangeability of the aftermarket (PMA) bearing in affected installations and concentrates replacement demand on the OEM part numbers specified (Requirement 1.b and 2.b; Note 3). This shifts spend from the PMA supplier to the OEM in the short term.\n  - If Allison parts are limited in supply, that creates implementation risk (delays, increased prices) and may increase operators’ costs or aircraft downtime.\n\n- Compliance burden and operational impact:\n  - Short inspection intervals for relatively new installations (every 25 hours while the bearing has <300 hours) impose frequent access/inspection activity, recordkeeping and possible increased removal for maintenance. After 300 hours the inspection interval relaxes to 100 hours (Compliance).\n  - “At next access” replacement means the timing of replacement can depend on when the engine is next opened for maintenance, creating variability in operators’ scheduling and potential for prolonged exposure to the defective part if access is deferred.\n\n- Implementation and enforcement mechanics:\n  - The AD cross‑references manufacturer service bulletins for the inspection procedures, and references the FAA AD for related context (Note 2). That means compliance depends on following external documents and on MROs interpreting those bulletins correctly.\n  - The regulator (Civil Aviation Safety Authority) mandates compliance; MROs perform inspections/replacements and maintain records.\n\n**Concrete citation to the instrument**\n- Requirements and actions: Requirement 1.a/1.b (No. 5 bearing) and 2.a/2.b (No. 8 bearing).\n- Terminating action: Note 3.\n- Timing and frequency: Compliance section (initial by 31/12/1996, 25‑hour intervals while <300 hours, then 100‑hour intervals; replacement at next access).\n- Safety rationale: Background (reports of premature wear and possible turbine/engine failure)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific manufacturing defect in aftermarket parts. The scope remains precisely limited to the identified bearing failures and does not extend beyond the original safety purpose."},"complexity_factors":["Multiple applicability categories requiring cross-referencing against specific engine model numbers (24 variants listed)","Two distinct bearing part numbers with parallel but separate compliance requirements","Tiered compliance schedule based on accumulated flight hours (25-hour vs 100-hour intervals depending on whether bearing has <300 hours time-in-service)","Reference to external technical documents (Superior Turbine Service Bulletins T95-SB001 Rev A and T95-SB002 Rev A) without reproducing their content","Conditional logic: 'at next access to the affected bearing' creates operational discretion that requires maintenance judgment","Cross-reference to FAA Airworthiness Directive 96-19-01 for additional context"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspection and replacement of certain Superior Air Parts bearings (installed in Allison 250-series turbine engines) because they’ve been failing prematurely and can cause catastrophic in‑flight engine failure. It affects operators of helicopters and small turboprops with these engines.\n\nOperators must inspect oil filters for metal debris and replace the suspect bearings with Allison-made parts by the specified deadline (initial check before 31 Dec 1996) and follow recurring inspection intervals until replacement."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-78-superior-turbine-bearings","history":"/api/acts/ad-al-250-78-superior-turbine-bearings/history","analysis":"/api/acts/ad-al-250-78-superior-turbine-bearings/analysis","conflicts":"/api/acts/ad-al-250-78-superior-turbine-bearings/conflicts","importantCases":"/api/acts/ad-al-250-78-superior-turbine-bearings/important-cases","documents":"/api/acts/ad-al-250-78-superior-turbine-bearings/documents"}}