{"id":"F2006B10418","name":"AD/HS 125/138 - Wing Leading Edge Corrosion","slug":"ad-hs-125-138-wing-leading-edge-corrosion","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116099,"registerId":"commonwealth-F2006B10418-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/138 - Wing Leading Edge Corrosion","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 125/138 Wing Leading Edge Corrosion 9/93\n\nApplicability: Model 125 Series 800 and 1000 aircraft pre-Mod. 253538A or B (Improved Corrosion Protection).\n\n \n\nRequirement: Action in accordance with British Aerospace Mandatory Service Bulletin 57-77.\n\n \n\nNote: UK CAA AD 016-05-93 refers.\n\n \n\nCompliance: Within 2 years of the date of aircraft manufacture or prior to 31 May 1994, whichever occurs later.\n\n \n\nBackground: Reports have been received of exfoliation corrosion of the wing leading edge section at the interface with the TKS panels. This is due to the ingress of moisture through gaps in the sealant that have developed during service.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific corrosion issue in a specific aircraft type. It has not expanded beyond its original purpose of mandating inspection and repair of wing leading edge corrosion."},"complexity_factors":["Single, specific aircraft type and model range (BAe 125 Series 800 and 1000)","Clear applicability criteria based on modification status","Single compliance action referencing an external technical document (Service Bulletin 57-77)","Simple time-based compliance deadline with clear 'whichever is later' logic","No defined terms section, no cross-references to other legislation, no conditional exceptions","Total length: approximately 150 words of substantive content"],"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 business jets (specifically the Series 800 and 1000 models) to inspect and fix a corrosion problem in the wing leading edge. The corrosion occurs where the wing meets the TKS panels (ice protection panels), caused by moisture getting through worn-out sealant.\n\n**Who must follow it:** Anyone operating a BAe 125 Series 800 or 1000 aircraft that hasn't been modified with improved corrosion protection (Mod. 253538A or B).\n\n**What they must do:** Follow the instructions in British Aerospace Mandatory Service Bulletin 57-77 — a technical document from the manufacturer detailing the inspection and repair procedures.\n\n**When it must be done:** Within 2 years of the aircraft's manufacture date, or before 31 May 1994 — whichever comes later.\n\n**Why it matters:** Exfoliation corrosion (a type of corrosion that spreads between metal layers) can weaken the wing structure. This directive prevents potential structural failure that could endanger passengers and crew."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument’s scope is narrowly targeted at BAe 125 Series 800 and 1000 aeroplanes that are built prior to incorporation of Mod 253538A or 253538B and prescribes following the manufacturer’s Service Bulletin to address a specific corrosion issue reported at the wing leading edge/TKS panel interface. The text provides no indication that the scope has been expanded or narrowed from an earlier stated intent; it remains focused on the identified affected aircraft and a single prescribed corrective action. (Applicability) (Requirement) (Background)"},"complexity_factors":["Narrow technical scope limited to BAe 125 Series 800 and 1000 aircraft pre-Mod 253538A/B (Applicability)","Mandates compliance with an external technical document (British Aerospace Mandatory Service Bulletin 57-77) rather than specifying repair steps in the instrument itself (Requirement)","Conditional compliance deadline tied to either aircraft manufacture date or a fixed calendar date, which requires per-aircraft calculation (Compliance)","Cross-reference to a foreign regulator’s AD (UK CAA AD) for related context but without inclusion of further requirements (Note)","Lack of cost, parts or time-off-wing data in the instrument, which leaves practical implementation details to operators and maintenance providers (Requirement) (Compliance)"],"plain_english_summary":"Owners/operators of BAe 125 Series 800 and 1000 aeroplanes built before incorporation of Mod 253538A/B must carry out the actions in British Aerospace Mandatory Service Bulletin 57-77 to inspect/repair reported exfoliation corrosion at the wing leading edge/TKS panel interface.  \n\nWork must be done by the Bulletin’s deadline (within two years of manufacture or by 31 May 1994, whichever is later); owners bear the costs and follow the manufacturer’s technical instructions."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-138-wing-leading-edge-corrosion","history":"/api/acts/ad-hs-125-138-wing-leading-edge-corrosion/history","analysis":"/api/acts/ad-hs-125-138-wing-leading-edge-corrosion/analysis","conflicts":"/api/acts/ad-hs-125-138-wing-leading-edge-corrosion/conflicts","importantCases":"/api/acts/ad-hs-125-138-wing-leading-edge-corrosion/important-cases","documents":"/api/acts/ad-hs-125-138-wing-leading-edge-corrosion/documents"}}