{"id":"F2006B02290","name":"AD/AL 250/80 Amdt 1 - Gearbox - Torquemeter Gearshaft Assembly","slug":"ad-al-250-80-amdt-1-gearbox-torquemeter-gearshaft-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41520,"registerId":"commonwealth-F2006B02290-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/80 Amdt 1 - Gearbox - Torquemeter Gearshaft Assembly","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/AL250/80 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)\n\nAllison Turbine Engines \\- 250 Series\n\nAD/AL 250/80\n\nAmdt 1\n\n  \nGearbox \\- Torquemeter Gearshaft Assembly 8/2002\n\nApplicability: All 250-C20, \\-C20R, \\- B17 and B17F Series II engines with less than 100 hours’ time in service since the installation of one of the following part number (P/N) helical torquemeter gearshaft assemblies.\n\n23035299, 23038191, 6889701, 6871218, 6870941, 23030857, 23004504, 23037441.\n\nNote 1: This Directive is only applicable to engines which have had maintenance carried out on the gearbox in the last 100 hours engine time in service and had one of the above part number gearshafts installed with less than 100 hours’ time since new during that maintenance.\n\nRequirement: Remove applicable helical torquemeter gearshaft assemblies from service in accordance with one of the following Rolls Royce Alert Commercial Engine Bulletins as applicable by engine model; CEB A-1386R1, CEB A-72-4087R1, TP CEB A- 1331R1, TP CEB A-72-2083R1.\n\nCompliance with the previous issue of these Bulletins satisfies the requirements of this Directive.\n\nNote 2: FAA AD 2001-24-12 refers.\n\nCompliance: Unless previously accomplished, effective 8 August 2002; before further flight.\n\nThis amendment becomes effective on 8 August 2002.\n\nBackground: This Directive has been amended to reflect FAA AD 2001-24-12. Rolls Royce Alert Commercial Engine Bulletins CEB A-1386R1, CEB A-72-4087R1, TP CEB A- 1331R1, TP CEB A-72-2083R1 have been revised to reflect additional data. The original Directive was issued to address a reported power turbine overspeed that resulted in an uncontained release of turbine blades and turbine disc fragments. The overspeed release resulted in an engine fire and damage to the aircraft. The overspeed resulted from a high cycle fatigue initiated failure of the helical Torquemeter gearshaft. The examination of the failed gearshaft revealed evidence of a pre-existing crack.\n\nAllison Turbine Engines \\- 250 Series\n\nAD/AL250/80 Amdt 1 (continued)\n\nThe original issue of this Airworthiness Directive became effective on 17 October 2001.\n\n![](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 28 June 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 17 July 2002.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment remains tightly focused on its original safety purpose — addressing the specific high cycle fatigue failure mode in torquemeter gearshafts. The amendment merely updates the technical references to reflect revised Rolls Royce bulletins and aligns with the corresponding FAA directive. It does not expand beyond the original unsafe condition or apply to additional engine models."},"complexity_factors":["Multiple specific part numbers to identify (8 different P/Ns)","Nested applicability conditions: engine model + maintenance history + time-in-service thresholds (100 hours since installation, 100 hours since new, 100 hours since gearbox maintenance)","Cross-reference to four different external technical documents (Rolls Royce Bulletins) that contain the actual procedural instructions","Reference to corresponding FAA AD 2001-24-12 for additional context","Amendment structure requires understanding relationship between original AD (October 2001) and this revised version (August 2002)"],"plain_english_summary":"This AD orders immediate removal from service of certain helical torquemeter gearshaft assemblies installed in Allison 250-C20/C20R/B17/B17F Series II engines because pre-existing cracks can cause high-cycle-fatigue failure, turbine overspeed, uncontained blade/disc release, fire, aircraft damage, and loss of life.\n\nIt affects owners/operators of helicopters with those engines—especially if gearbox work in the last 100 flight hours installed one of the listed gearshafts—and requires removal before next flight (from 8 Aug 2002). Previous compliant actions remain valid."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment updates and reissues the earlier directive to align with FAA AD 2001-24-12 and revised Rolls Royce Alert Commercial Engine Bulletins; it retains the original safety focus (removal of specific helical torquemeter gearshafts due to fatigue crack risk) and does not materially expand the set of affected engine types or introduce new regulatory powers. The principal change is to the referenced service instructions (CEBs) and to reflect additional data, not a substantive broadening of scope."},"complexity_factors":["Short, single-issue directive focused on removal of specific parts","7 distinct part numbers listed in Applicability","Conditional applicability: only engines with gearbox maintenance in last 100 engine-hours and with installed gearshafts that have <100 hours since new (Note 1)","Cross-reference to four Rolls Royce Alert Commercial Engine Bulletins (CEBs) for procedural detail","Reference to an external FAA AD (2001-24-12) and revised manufacturer bulletins","Straightforward compliance timing (before further flight; effective date specified)"],"plain_english_summary":"**What this instrument does (mechanically)\n\n- This is an Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA). It cancels a previous AD and requires that certain helical torquemeter gearshaft assemblies be removed from service on specified Allison 250 turbine engines.\n- The AD applies to certain 250-series engines (250-C20, -C20R, -B17 and -B17F Series II) that have had gearbox maintenance within the last 100 hours of engine time and where one of the listed part numbers (P/Ns) of gearshafts was installed and that gearshaft has less than 100 hours since new. (See \"Applicability\".)\n- The mandated action is removal of the listed gearshaft assemblies \"in accordance with\" the specified Rolls Royce Alert Commercial Engine Bulletins (CEBs): CEB A-1386R1, CEB A-72-4087R1, TP CEB A-1331R1, TP CEB A-72-2083R1. Compliance with earlier issues of those Bulletins also satisfies the AD. (See \"Requirement\" and \"Note 2\".)\n- The compliance deadline is immediate for affected engines: before further flight, effective 8 August 2002. (See \"Compliance\".)\n\n**Who is directly affected\n\n- Aircraft operators and owners who operate the listed Allison 250 engine models and who have had gearbox maintenance in which one of the listed gearshafts was fitted within the last 100 hours of engine time.\n- Maintenance, repair and overhaul (MRO) organisations that perform gearbox work and that installed those gearshafts in the specified window.\n- Parts suppliers and maintenance shops involved in replacing the removed gearshafts.\n\n**Why CASA issued the AD (stated purpose and technical reason)\n\n- The AD says it was issued because of an incident where a power turbine overspeed occurred, causing an uncontained release of turbine blades and disc fragments, a resulting engine fire, and damage to the aircraft. The overspeed was traced to a high-cycle-fatigue failure of a helical torquemeter gearshaft where a pre-existing crack was found. (See \"Background\".)\n- The AD has been amended to align with FAA AD 2001-24-12 and revised Rolls Royce CEBs which contain additional data relevant to the corrective action.\n\n**How the AD changes behaviour and who pays\n\n- Behaviour change required: operators/MROs must inspect maintenance records to identify affected engines, remove the specified gearshaft assemblies, and carry out the removal work according to the Rolls Royce Bulletins before the next flight.\n- Who pays: the immediate financial and operational costs fall on the aircraft owner/operator or their MRO provider. Costs include labour for inspection and removal, replacement parts if required, and aircraft downtime.\n\n**Implementation mechanics and compliance risk\n\n- The AD references specific service bulletins (the Rolls Royce CEBs) for the detailed removal and replacement procedure. This delegates technical method to those supplier documents (see \"Requirement\").\n- Compliance is time-critical (before further flight), so operators must quickly check records and ground affected aircraft until the action is done. If maintenance records are incomplete or parts tracking is poor, there is a risk of non‑compliance or operational disruption.\n\n**Costs, incentives, and trade-offs\n\n- Direct cost: operators incur inspection and removal/replacement costs and aircraft downtime. These are concentrated on operators of the affected engine types who fit the listed P/Ns.\n- Safety benefit: the stated benefit is reduced risk of turbine overspeed and uncontained engine failures. The benefit is concentrated (operators and passengers of affected aircraft) but also diffuse in reducing risk to third parties on the ground and to airworthiness oversight.\n- Market effects: demand for replacement gearshafts or approved alternatives will increase immediately, which may push supply and price effects on small numbers of operators and independent MROs that rely on stocking those components.\n- Incentives: operators are incentivised to improve parts traceability and maintenance record-keeping to avoid last-minute groundings. MROs bear incentives to ensure conformity to the Rolls Royce Bulletins to limit liability and avoid repeat removals.\n\n**Administrative discretion and referenced documents\n\n- CASA exercised delegated regulatory power under CAR 1998 subregulation 39.1(1) to revoke and reissue the AD; the technical content and method are tied to the Rolls Royce Bulletins referenced. The AD therefore relies on those manufacturer documents to specify the detailed steps and any technical judgement.\n\n**Possible unintended consequences or substitution effects (mechanisms, not value judgments)\n\n- Replacement needs could strain parts availability for these engine models in the short term, increasing lead times or costs for operators.\n- Operators with poor record-keeping may be forced to ground aircraft until conformity is proven, increasing operational disruption.\n\n\nSource citations (where each point is drawn from the text):\n- Applicability and Note 1: who/when engines are affected.\n- Requirement and Note 2: what must be done and which Bulletins to follow.\n- Compliance: timing requirement (before further flight; effective 8 August 2002).\n- Background: technical cause (high-cycle fatigue, pre-existing crack) and connection to FAA AD and revised CEBs.\n\nSummary statement: The AD mechanically orders removal of specific helical torquemeter gearshafts from certain Allison 250-series engines installed during recent gearbox maintenance, requires following Rolls Royce service Bulletins for the work, and sets immediate compliance (before further flight). The direct financial and operational burden falls on aircraft operators and MROs; the technical justification is to prevent a repeat of an engine overspeed and uncontained failure traced to fatigue-cracked gearshafts."},"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-250-80-amdt-1-gearbox-torquemeter-gearshaft-assembly","history":"/api/acts/ad-al-250-80-amdt-1-gearbox-torquemeter-gearshaft-assembly/history","analysis":"/api/acts/ad-al-250-80-amdt-1-gearbox-torquemeter-gearshaft-assembly/analysis","conflicts":"/api/acts/ad-al-250-80-amdt-1-gearbox-torquemeter-gearshaft-assembly/conflicts","importantCases":"/api/acts/ad-al-250-80-amdt-1-gearbox-torquemeter-gearshaft-assembly/important-cases","documents":"/api/acts/ad-al-250-80-amdt-1-gearbox-torquemeter-gearshaft-assembly/documents"}}