{"id":"F2006B06324","name":"AD/PR/25 Amdt 9 - Hub Wall Cracking","slug":"ad-pr-25-amdt-9-hub-wall-cracking","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47476,"registerId":"commonwealth-F2006B06324-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PR/25 Amdt 9 - Hub Wall Cracking","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nPropellers \\- Variable Pitch \\- Dowty Rotol\n\nAD/PR/25\n\nAmdt 9\n\n  \nHub Wall Cracking 5/95\n\nApplicability: ALL R354/4-123-F/13, R354/4-123-F/20 and R375/4-123-F/21 propellers fitted to SAAB 340A or 340B aircraft.\n\nRequirement: 1. Action in accordance with Dowty Aerospace Propellers Mandatory Service Bulletin SF340-61-A42 Revision 6.\n\n2. Action in accordance with Dowty Aerospace Propellers SB SF340-61-61 Revision 4.\n\nCompliance: 1. As specified in the Requirement Document until Requirement 2 has been complied with.\n\n2. Unless previously carried out, at the next overhaul of the propeller. Incorporation of SB SF340-61-61 Rev 4 provides terminating action for this directive.\n\nBackground: Previous amendments have been raised to provide terminating action, to correct several P/N errors and to vary the repetitive inspection requirements.\n\nThis amendment mandates compliance with Revision 6, latest revision, to Dowty Mandatory SB SF340-61-A42.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment mandates compliance with Dowty Mandatory Service Bulletin SF340-61-A42 Revision 6 and requires incorporation of Dowty SB SF340-61-61 Revision 4 at the next propeller overhaul as terminating action. Compared with prior versions (which the Background says corrected part numbers and varied repetitive inspection requirements), the current text prescribes the latest SB revision (Rev 6) for immediate actions and ties termination of repetitive inspections to incorporation of SB SF340-61-61 Rev 4 at overhaul, thereby shifting the ongoing inspection regime to a defined terminating action."},"complexity_factors":["Multiple referenced documents (two Dowty service bulletins with specific revision numbers) requiring cross-referencing.","Conditional structure: one SB is mandatory until a second SB is incorporated, at which point the AD terminates.","Applicability limited to specific propeller P/Ns and aircraft types, requiring correct identification of equipment.","Amendments history (corrections to part numbers and inspection interval changes) increases the need to confirm the current mandated revision."],"plain_english_summary":"What this instrument does\n\n- This Airworthiness Directive (AD) applies to all Dowty Rotol propellers with part numbers R354/4-123-F/13, R354/4-123-F/20 and R375/4-123-F/21 when fitted to SAAB 340A or 340B aircraft. (Applicability)\n- It requires operators to carry out the work specified in two Dowty service bulletins: Mandatory Service Bulletin SF340-61-A42 Revision 6, and Service Bulletin SF340-61-61 Revision 4. (Requirement)\n- Until the second bulletin (SF340-61-61 Rev 4) has been incorporated, operators must follow the inspection and corrective actions in the Mandatory SB (SF340-61-A42 Rev 6) as set out in that document. Once SB SF340-61-61 Rev 4 has been incorporated at the next propeller overhaul, that incorporation terminates the AD. (Compliance)\n\nWho this affects and who decides\n\n- Who pays: aircraft operators and propeller owners pay for the inspections, any repairs, and for incorporating the service bulletins at overhaul (Requirement; Compliance). These are maintenance costs and potential downtime costs for the affected SAAB 340 aircraft.\n- Who decides: the Civil Aviation Safety Authority issued the AD and prescribes compliance with the specified Dowty Aerospace Propellers service bulletins. The detailed technical steps and intervals are set out in the Dowty SB documents the AD mandates. (Header; Requirement)\n\nWhy it matters (stated purpose and practical trade-offs)\n\n- Stated purpose: the AD addresses \"Hub Wall Cracking\" on the listed Dowty propellers (title and Background). The Background notes prior amendments corrected part-number errors and changed repetitive inspection requirements.\n- Practical trade-offs and incentives:\n  - Immediate compliance cost: operators must perform inspections and any corrective work specified in SF340-61-A42 Rev 6 until they incorporate SF340-61-61 Rev 4. This creates ongoing inspection burden until the terminating action is taken. (Requirement; Compliance)\n  - Terminating action: incorporation of SB SF340-61-61 Rev 4 at the next propeller overhaul removes the need for the repetitive action mandated by the AD, so doing that work at overhaul reduces future compliance burden. (Compliance)\n  - Timing flexibility: the AD prescribes that SB SF340-61-61 Rev 4 be incorporated \"at the next overhaul\" unless already done; otherwise the mandatory SB actions continue. That creates a predictable point (overhaul) for operators to incur the termination cost. (Compliance)\n\nImplementation and compliance notes\n\n- The AD is prescriptive: it names specific Dowty SBs and exact revisions that must be followed, so technical compliance depends on following those documents precisely. (Requirement)\n- The Background records that earlier amendments corrected part-number errors and varied inspection intervals, so operators must ensure they refer to the correct part numbers and the latest mandated SB revision. (Background)\n- The AD ties the removal of the repetitive requirement to incorporation of a specific SB at overhaul, which concentrates the larger one-time cost at the next overhaul date and leaves smaller, repeated inspection costs in the interim. (Compliance)\n\nConcrete effects on behaviour\n\n- Operators will perform the Dowty-mandated inspections and corrective actions as specified in SF340-61-A42 Rev 6 immediately and repeatedly as required by that document until they carry out SB SF340-61-61 Rev 4 at overhaul. (Requirement; Compliance)\n- Maintenance organisations will need to follow the Dowty SB procedures and revisions specified by the AD. (Requirement)\n\nSource citations: Applicability; Requirement; Compliance; Background."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment remains tightly focused on its original purpose: addressing hub wall cracking in specific Dowty Rotol propellers fitted to SAAB 340 aircraft. The amendment history notes it has been updated to correct part number errors and adjust inspection intervals, but these are refinements within the original scope rather than expansion into new areas."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 3 defined propeller part numbers in the applicability section","Two cross-referenced external documents (manufacturer service bulletins) that contain the actual technical requirements","Simple conditional logic: 'do X until Y is done, then stop'","No nested definitions or interpretive provisions","Clear terminating condition (overhaul or previous compliance)"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on certain aircraft propellers.\n\n**What it does:**\n- Orders owners and operators of SAAB 340A and 340B aircraft to inspect and repair specific Dowty Rotol propeller models (R354/4-123-F/13, R354/4-123-F/20, and R375/4-123-F/21) due to a known defect: **cracking in the propeller hub walls**.\n\n**Who must act:**\n- Anyone operating SAAB 340 aircraft with the affected propeller models.\n\n**What must be done:**\n- **First:** Follow the instructions in Dowty Aerospace Propellers Mandatory Service Bulletin SF340-61-A42 (Revision 6) — this sets out the inspection and repair requirements.\n- **Second:** Eventually comply with Service Bulletin SF340-61-61 (Revision 4), which provides **terminating action** (meaning once this is done, the ongoing inspections can stop).\n\n**When to comply:**\n- Keep doing the inspections from the first bulletin until you've completed the second bulletin.\n- The second bulletin must be done at the next propeller overhaul, unless already completed.\n\n**Why it matters:**\nHub wall cracking in a propeller is a serious safety risk — it could lead to propeller failure in flight. This directive ensures the defect is found and fixed before it causes an accident. The amendment updates the requirements to the latest manufacturer guidance (Revision 6) and clarifies how operators can eventually stop the repetitive inspections."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pr-25-amdt-9-hub-wall-cracking","history":"/api/acts/ad-pr-25-amdt-9-hub-wall-cracking/history","analysis":"/api/acts/ad-pr-25-amdt-9-hub-wall-cracking/analysis","conflicts":"/api/acts/ad-pr-25-amdt-9-hub-wall-cracking/conflicts","importantCases":"/api/acts/ad-pr-25-amdt-9-hub-wall-cracking/important-cases","documents":"/api/acts/ad-pr-25-amdt-9-hub-wall-cracking/documents"}}