{"id":"F2006B10517","name":"AD/HS 125/76 - APU Bonding","slug":"ad-hs-125-76-apu-bonding","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116297,"registerId":"commonwealth-F2006B10517-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/76 - APU Bonding","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  British Aerospace BAe 125 Series Aeroplanes\n\n \n\nAD/HS 125/76 APU Bonding 4/86\n\nApplicability: All DH/HS/BH/B.Ae.125 series aircraft up to and including aircraft 258034 fitted with an Auxiliary Power Unit to Mod. 251605 or 258748.\n\n \n\nRequirement: Action in accordance with British Aerospace SB 49-32-(9210A).\n\n \n\nNote: The British CAA have classified this Service Bulletin as mandatory.\n\n \n\nCompliance: Before 31 December 1986.\n\n \n\nBackground:  To protect the A.P.U. system against a possible starter/generator live casing condition, and potential fire hazard.\n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD's stated scope is limited to BAe 125 series aircraft up to and including serial 258034 fitted with APUs to Mod. 251605 or 258748, and requires action per British Aerospace SB 49-32-(9210A) to address a specified APU hazard. The document itself sets the applicability, the technical compliance method, the deadline and the stated safety purpose; there is no text in the instrument indicating a change in scope from that stated intent. (Applicability; Requirement; Compliance; Background)"},"complexity_factors":["Narrow technical applicability (specific aircraft series and serial-number cutoff; specific APU modification numbers) (Applicability)","Mandates compliance by reference to an external technical document (British Aerospace SB 49-32-(9210A)) rather than reproducing technical instructions (Requirement)","Fixed calendar compliance deadline that compresses scheduling choices for operators (Compliance)","Cross-reference to foreign regulator's classification (British CAA) introducing an external regulatory signal (Note)"],"plain_english_summary":"Owners and operators of specified British Aerospace BAe 125 series aeroplanes fitted with APU Mod. 251605 or 258748 must modify APU bonding in accordance with British Aerospace Service Bulletin 49‑32‑(9210A). Compliance is mandatory by 31 December 1986. The measure—at operator expense—aims to protect the APU against a possible live‑casing starter/generator condition and reduce fire risk."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive with a narrow, well-defined scope. It addresses a specific technical fault in a specific aircraft type and does not represent scope creep from any broader legislative scheme."},"complexity_factors":["Very short document (approximately 150 words)","Only 4 operative provisions: applicability, requirement, note, and compliance","Single cross-reference to external technical document (British Aerospace SB 49-32-(9210A))","No defined terms section — terms like 'Mod. 251605' rely on industry knowledge","No nested conditions or exceptions","Simple temporal trigger for compliance (fixed date deadline)"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:** It requires owners and operators of certain British Aerospace BAe 125 series business jets to carry out a specific safety modification to the **Auxiliary Power Unit (APU)** — a small engine at the back of the plane that provides power when the main engines are off.\n\n**The problem:** The APU's starter/generator (the device that starts the APU and generates electricity) could develop a \"live casing\" fault. This means the outer metal housing could become electrically charged, creating a **fire risk**.\n\n**Who must comply:** Anyone operating BAe 125 series aircraft (including models designated DH/HS/BH/B.Ae.125) with serial numbers up to 258034, provided they have an APU fitted with specific modification standards (Mod. 251605 or 258748).\n\n**What they must do:** Follow the instructions in **British Aerospace Service Bulletin 49-32-(9210A)** — a technical document from the manufacturer detailing the required inspection or modification. The British aviation regulator (CAA) has already classified this bulletin as mandatory, and Australia is adopting that requirement.\n\n**Deadline:** The work had to be completed before **31 December 1986**.\n\n**Why it matters:** Electrical faults in APUs can cause fires — a serious hazard on any aircraft, especially during ground operations when the APU is typically running. This directive closes a known safety gap identified by the manufacturer and UK regulators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-76-apu-bonding","history":"/api/acts/ad-hs-125-76-apu-bonding/history","analysis":"/api/acts/ad-hs-125-76-apu-bonding/analysis","conflicts":"/api/acts/ad-hs-125-76-apu-bonding/conflicts","importantCases":"/api/acts/ad-hs-125-76-apu-bonding/important-cases","documents":"/api/acts/ad-hs-125-76-apu-bonding/documents"}}