{"id":"F2006B10570","name":"AD/HS 748/4 - Door Sill and Secondary Lock Mechanism Micro Switches","slug":"ad-hs-748-4-door-sill-and-secondary-lock-mechanism-micro-switches","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116403,"registerId":"commonwealth-F2006B10570-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 748/4 - Door Sill and Secondary Lock Mechanism Micro Switches","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 748/4 Door Sill and Secondary Lock Mechanism Micro Switches\n\n  \n13/94\n\nApplicability: All HS 748 aircraft.\n\nRequirement: Inspect all door sill and secondary lock mechanism micro switches in accordance with the Accomplishment Instructions of British Aerospace Aircraft Group, Manchester Division HS 748 Service Bulletin 52/106 dated November 1982.\n\nNote: CAA(UK) AD 001-01-83 refers.\n\nCompliance: At intervals not to exceed 1000 hours time in service, effective 8 December 1994.\n\nBackground: This Directive introduces a periodic inspection to confirm the integrity of the door sill and secondary lock mechanism micro switches of the crew/freight, passenger and baggage doors, including large freight doors where applicable.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope aligns with its stated purpose in the Background: to introduce a periodic inspection confirming the integrity of the specified micro switches. The AD prescribes the inspection subject, the controlling Service Bulletin, and the recurring interval; it does not expand beyond that original inspection objective. (Background; Requirement; Compliance)"},"complexity_factors":["Narrow technical scope limited to door sill and secondary lock mechanism micro switches on a specific aircraft type (Applicability; Background)","Mandatory reference to an external Service Bulletin for procedural detail (Requirement) — requires users to obtain and follow that document","Recurring compliance scheduling (intervals not to exceed 1,000 hours TIS) creates operational planning requirements (Compliance)","No alternative compliance paths or exemptions stated in the AD text (Requirement; Compliance)","Multiple door types covered (crew/freight, passenger, baggage, and large freight doors) requiring comprehensive inspection coverage (Background)"],"plain_english_summary":"This directive requires operators of all British Aerospace (Hawker Siddeley) HS 748 aircraft to perform recurring inspections of door sill and secondary lock mechanism micro switches per British Aerospace Service Bulletin 52/106.  \n\nInspections must follow the manufacturer’s Accomplishment Instructions and be repeated at intervals not exceeding 1,000 hours TIS, imposing recurring maintenance costs and scheduling impacts on owners/operators while confirming switch integrity for continued airworthiness."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on door micro switch inspections for one aircraft type. It has not expanded beyond its original technical safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly understood ('time in service')","No cross-references to other legislation or regulations beyond a single reference to a UK authority document","Single, unambiguous requirement with clear compliance deadline and interval","No conditional logic, exceptions, or nested provisions","Straightforward applicability statement ('All HS 748 aircraft')"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\n- Requires owners and operators of **British Aerospace HS 748 series aircraft** to regularly inspect small electrical switches (called \"micro switches\") that are part of the door locking systems.\n- These switches are located in two places: the door sill (the bottom frame of the door) and the secondary lock mechanism (a backup locking system).\n\n**Who it affects:**\n- Anyone who owns or operates an HS 748 aircraft in Australia.\n\n**Why it matters:**\n- Door micro switches are critical safety components. They typically send signals to warn pilots if doors are not properly closed and locked. If these switches fail, the crew might not receive warnings about improperly secured doors — which could lead to dangerous situations like doors opening during flight or incorrect pressurisation.\n- The directive mandates inspections every **1,000 hours of flight time** to catch wear, damage, or failure before they become dangerous.\n\n**Key details:**\n- The inspections must follow specific instructions from the manufacturer (British Aerospace Service Bulletin 52/106 from November 1982).\n- This became mandatory from **8 December 1994**.\n- The UK aviation authority issued a similar directive (CAA(UK) AD 001-01-83), which CASA references for additional context."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-748-4-door-sill-and-secondary-lock-mechanism-micro-switches","history":"/api/acts/ad-hs-748-4-door-sill-and-secondary-lock-mechanism-micro-switches/history","analysis":"/api/acts/ad-hs-748-4-door-sill-and-secondary-lock-mechanism-micro-switches/analysis","conflicts":"/api/acts/ad-hs-748-4-door-sill-and-secondary-lock-mechanism-micro-switches/conflicts","importantCases":"/api/acts/ad-hs-748-4-door-sill-and-secondary-lock-mechanism-micro-switches/important-cases","documents":"/api/acts/ad-hs-748-4-door-sill-and-secondary-lock-mechanism-micro-switches/documents"}}