{"id":"F2006B10415","name":"AD/HS 125/135 - Fire Protection Circuitry - Inspection of Blocking Diodes","slug":"ad-hs-125-135-fire-protection-circuitry-inspection-of-blocking-diodes","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116093,"registerId":"commonwealth-F2006B10415-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/135 - Fire Protection Circuitry - Inspection of Blocking Diodes","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 BAe 125 Series Aeroplanes\n\nAD/HS 125/135 Fire Protection Circuitry \\- Inspection\n\nof Blocking Diodes\n\n  \n4/93\n\nApplicability: All series 125 aircraft identified in Corporate Jets Limited Service Bulletin S.B. 26-33 dated 8 December 1992.\n\nRequirement: Action in accordance with the Accomplishment Instructions of Corporate Jets Limited Service Bulletin S.B. 26-33 dated 8 December 1992.\n\nNote: This Service Bulletin has been classified as Mandatory by the CAA(UK), AD 012-12-92 refers.\n\nCompliance: Prior to 1 May 1993.\n\nBackground: This Directive has been issued following reports of isolated cases of dormant failure of the blocking diodes associated with the ‘EXT FIRED’ (bottle gone) indicators.\n\nCompliance with this Directive will provide improved system integrity.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-limited airworthiness directive addressing a specific technical fault in a specific aircraft type. It has not expanded beyond its original scope; it was issued to fix a known safety issue with blocking diodes and serves exactly that purpose."},"complexity_factors":["Single, specific aircraft type (British Aerospace BAe 125 series)","Single technical requirement referencing an external service bulletin","No defined terms section","No nested exceptions or conditional logic","Clear, fixed compliance deadline","Short document (approximately 150 words)","Straightforward cause-and-effect: identified fault → mandatory inspection → deadline"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety order for aircraft owners and operators.\n\n**What it does:**\nIt requires owners of specific British Aerospace BAe 125 series business jets to inspect (and fix if needed) certain electrical components called **blocking diodes** in the fire protection system.\n\n**Why it matters:**\nThese diodes are part of the circuitry that tells pilots when a fire extinguisher bottle has been discharged (the \"EXT FIRED\" indicator). There had been reports of these diodes failing silently — meaning the indicator might not work when needed, and pilots wouldn't know if the fire suppression system had actually activated.\n\n**Who must comply:**\nAnyone operating a BAe 125 series aircraft covered by a specific service bulletin from Corporate Jets Limited (dated 8 December 1992).\n\n**What they must do:**\nFollow the instructions in that service bulletin to inspect the blocking diodes.\n\n**Deadline:**\nBefore 1 May 1993.\n\n**The bottom line:**\nThis is a targeted safety fix to prevent a hidden failure that could leave pilots unaware of whether their fire suppression system had actually worked during an emergency."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument confines action to aircraft specifically identified in Corporate Jets Limited Service Bulletin S.B. 26-33 and requires those aircraft to be inspected per the bulletin before the stated deadline. The directive’s stated purpose (to address reports of dormant diode failure and improve system integrity) aligns with the mechanical change required (inspection of blocking diodes). There is no indication in the text that the scope was expanded or narrowed beyond that original operational objective (Applicability; Requirement; Background; Compliance)."},"complexity_factors":["Reference to an external technical document (Corporate Jets Limited Service Bulletin S.B. 26-33) for the detailed procedure rather than containing detailed steps in the directive itself (Requirement).","Technical subject matter (electrical blocking diodes and aircraft fire-protection indicators) requires specialist maintenance expertise to assess and remediate (Background; Requirement).","A fixed compliance deadline (prior to 1 May 1993) creates a scheduling and operational constraint for affected operators (Compliance).","Limited applicability scope (only BAe 125 series aircraft identified in the service bulletin) reduces breadth but requires cross-checking of fleet records to determine affected units (Applicability).","Cross-jurisdictional note that the UK CAA classified the bulletin as mandatory introduces an external regulatory reference that may affect interpretation or enforcement expectations (Note)."],"plain_english_summary":"This airworthiness directive requires owners/operators and maintenance organisations of specified BAe 125 series aeroplanes to inspect the blocking diodes for the “EXT FIRED” bottle‑gone indicators per Corporate Jets Ltd Service Bulletin S.B. 26‑33 (Accomplishment Instructions) by the stated deadline. Issued after reports of isolated diode failures, it aims to improve system integrity; inspection costs and any corrective work are borne by operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-135-fire-protection-circuitry-inspection-of-blocking-diodes","history":"/api/acts/ad-hs-125-135-fire-protection-circuitry-inspection-of-blocking-diodes/history","analysis":"/api/acts/ad-hs-125-135-fire-protection-circuitry-inspection-of-blocking-diodes/analysis","conflicts":"/api/acts/ad-hs-125-135-fire-protection-circuitry-inspection-of-blocking-diodes/conflicts","importantCases":"/api/acts/ad-hs-125-135-fire-protection-circuitry-inspection-of-blocking-diodes/important-cases","documents":"/api/acts/ad-hs-125-135-fire-protection-circuitry-inspection-of-blocking-diodes/documents"}}