{"id":"F2006B10574","name":"AD/HS 748/9 - Auto Feather Micro Switch Operating Levers","slug":"ad-hs-748-9-auto-feather-micro-switch-operating-levers","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116411,"registerId":"commonwealth-F2006B10574-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 748/9 - Auto Feather Micro Switch Operating Levers","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBritish Aerospace (Hawker Siddeley) HS 748 Series Aeroplanes\n\nAD/HS 748/9 Auto Feather Micro Switch Operating Levers 1/95\n\nApplicability: All HS 748 series aircraft not incorporating modification 6909.\n\nRequirement: Action in accordance with Revision 4 of Jetstream Aircraft Ltd Mandatory SB HS748-76-15.\n\nNote: UK CAA AD 0132 refers.\n\nCompliance: Within 1000 hours time in service from 5 January 1995. Thereafter, reinspect at intervals not exceeding 1000 hours time in service until modification 6909 has been incorporated.\n\nBackground: Cracks in the fork end of the levers which actuate the auto feather inhibiting micro switches, located on the engine sub frame, have been reported. In the event of a failed micro switch being followed by an engine failure, propeller auto feathering will not take place.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD targets a specific, identified failure mode (cracking of the fork end of the auto-feather micro switch operating levers) and prescribes inspections at fixed intervals until modification 6909 is incorporated. The directive therefore retains the original corrective scope — detect and address cracking of those levers to preserve auto-feather function — and does not broaden or narrow the population of affected aircraft beyond HS 748 aeroplanes lacking modification 6909. (Applicability; Background; Compliance)"},"complexity_factors":["Applicability is narrowly defined (only HS 748 series aircraft without modification 6909).","Compliance references an external technical document (Jetstream Mandatory SB HS748-76-15 Revision 4) for procedural detail.","Fixed inspection interval (1000 hours) and a clear end condition (incorporation of modification 6909) reduce interpretive complexity.","Technical work concerns small, specific components (fork end of operating levers) rather than system-wide changes.","Administrative requirements (scheduling, recordkeeping) are routine but must be maintained until modification 6909 is installed."],"plain_english_summary":"### What this document does\nThis Airworthiness Directive (AD) requires operators of certain British Aerospace (Hawker Siddeley) HS 748 series aeroplanes to inspect and, where necessary, act on the auto-feather micro switch operating levers that are mounted on the engine subframe. The directive applies only to HS 748 aeroplanes that have not had modification 6909 installed. (Applicability; Requirement)\n\n### Who this affects\nOwners and operators of HS 748 series aircraft that do not incorporate modification 6909 must comply. The Civil Aviation Safety Authority (CASA) issues the directive and directs compliance by reference to Jetstream Aircraft Ltd Mandatory Service Bulletin HS748-76-15 Revision 4. (Applicability; Requirement)\n\n### What you must do and when\n- Inspect the fork end of the levers that actuate the auto-feather inhibiting micro switches in accordance with Revision 4 of Jetstream Aircraft Ltd Mandatory SB HS748-76-15. (Requirement)\n- Do the first inspection within 1000 hours time in service counted from 5 January 1995. After that, repeat the inspection at intervals not exceeding 1000 hours time in service until modification 6909 has been installed on the aircraft. (Compliance)\n\n### Why this is required (claimed safety concern)\nThe directive explains that cracks have been reported in the fork end of these levers. If a micro switch fails and is then followed by an engine failure, the propeller may not auto-feather. The inspections (and eventual modification 6909) are directed to detect or eliminate the cracking risk so that auto-feathering will function when needed. (Background)\n\n### Who pays and what it costs (mechanics, not numbers)\n- Aircraft owners/operators pay for the inspections and any remedial work required by the service bulletin. (Requirement; Compliance)\n- Operators face an ongoing compliance cost in the form of repeat inspections every 1000 hours until they install modification 6909. Installing modification 6909 is presented as an alternative end-state after which the recurring inspections required by this AD no longer apply; that creates a trade-off between ongoing inspection costs and the one‑off time, parts and labour cost to incorporate the modification. (Compliance)\n\n### Who decides how to comply\nCASA prescribes the mandated action and the compliance timing. The detailed technical steps and any necessary repairs are required to be done \"in accordance with\" the specified Jetstream Mandatory Service Bulletin Revision 4, which defines the technical procedure. (Requirement)\n\n### Implementation and compliance risks\n- The AD ties compliance to an external technical document (the service bulletin). Following that bulletin precisely is required to meet the AD. (Requirement)\n- Recordkeeping and scheduling are needed to ensure inspections occur within the 1000-hour interval until modification 6909 is fitted. If inspections or the modification are not carried out, the stated safety failure mode (loss of auto-feather on engine failure) remains a risk. (Compliance; Background)\n\n### Net effect on operations\nOperators must introduce a maintenance task into their scheduled maintenance regime (inspection every 1000 hours until modification 6909 is installed) or perform the modification to remove the recurring inspection requirement. The AD therefore shifts maintenance effort and cost onto operators of affected aircraft until they incorporate the specified modification. (Applicability; Requirement; Compliance)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete airworthiness directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Single, specific technical requirement with clear compliance deadline","Only one defined term of note ('time in service' implied as flight hours)","No nested exceptions or conditional logic—straightforward inspection mandate","Cross-reference to only one external document (UK CAA AD 0132) and one service bulletin","Extremely short document (approximately 150 words)","Single applicability criterion (all HS 748 series without modification 6909)"],"plain_english_summary":"This is a **safety order for specific aircraft**. It requires owners and operators of British Aerospace HS 748 series planes to inspect a particular mechanical part—the tiny lever that controls the 'auto feather' safety system on the engines.\n\n**What is auto feather?** It's an automatic safety feature. If an engine fails during flight, the system automatically adjusts the propeller blades to reduce drag and help the pilot maintain control. If this system fails because a tiny switch is broken, the plane becomes harder to control during an engine failure.\n\n**What must be done:**\n- **Inspect** the small levers (called \"micro switch operating levers\") that activate the auto feather system\n- **When:** Within 1,000 flight hours starting from 5 January 1995, then re-check every 1,000 flight hours after that\n- **Keep doing this** until the aircraft is modified with a permanent fix (modification 6909)\n\n**Why it matters:** Cracks have been found in these levers. If a lever breaks and then an engine fails, the auto feather system won't work—creating a dangerous situation where the pilot has less control. This directive prevents accidents by catching cracks before they cause failures.\n\n**Who issued this:** The Civil Aviation Safety Authority (CASA), using powers under the Civil Aviation Regulations 1998."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-748-9-auto-feather-micro-switch-operating-levers","history":"/api/acts/ad-hs-748-9-auto-feather-micro-switch-operating-levers/history","analysis":"/api/acts/ad-hs-748-9-auto-feather-micro-switch-operating-levers/analysis","conflicts":"/api/acts/ad-hs-748-9-auto-feather-micro-switch-operating-levers/conflicts","importantCases":"/api/acts/ad-hs-748-9-auto-feather-micro-switch-operating-levers/important-cases","documents":"/api/acts/ad-hs-748-9-auto-feather-micro-switch-operating-levers/documents"}}