{"id":"F2006B10436","name":"AD/HS 125/155 - Fuselage Fluid Drainage","slug":"ad-hs-125-155-fuselage-fluid-drainage","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116135,"registerId":"commonwealth-F2006B10436-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/155 - Fuselage Fluid Drainage","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 125/155 Fuselage Fluid Drainage 10/96\n\nApplicability: BAe 125 series 800A, series 800B, and Hawker 800 aircraft.\n\nRequirement: Action in accordance with Hawker Mandatory Service Bulletin 53-82-3566G Revision 3.\n\nNote: FAA AD 96-12-16 Amdt 39-9659 refers.\n\nCompliance: Unless Modification 253566G is already installed in accordance with a previous issue of the Requirement document, including a functional test to determine if a bolt fouls the flap control system (in accordance with para. 2.A.(18) of the SB Accomplishment Instructions); before 31 December 1996.\n\nBackground: Reports were received of restricted control of the ailerons due to water accumulation that froze at an aileron pulley in the lower area of the fuselage, aft of the wing rear spar.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope aligns with its stated purpose: it applies to BAe 125 series 800A, series 800B and Hawker 800 aircraft and requires the installation (or verification of prior installation) of Modification 253566G per Hawker Mandatory Service Bulletin 53-82-3566G Revision 3 to prevent water accumulation freezing at an aileron pulley. The text does not indicate any expansion or narrowing of scope beyond that original intent (Applicability, Requirement, Background, Compliance)."},"complexity_factors":["Narrow applicability to specific aircraft models (BAe 125 series 800A, 800B and Hawker 800) reduces breadth but concentrates impact (Applicability).","Compliance is tied to a specific manufacturer service bulletin and a particular revision (Hawker Mandatory Service Bulletin 53-82-3566G Revision 3), so conformity requires following detailed technical steps in that external document (Requirement).","The directive includes a conditional exemption where the named modification plus functional test has already been installed under a prior service bulletin issue, introducing a verification step for prior work (Compliance).","A functional test to detect whether a bolt fouls the flap control system is required, which raises technical/diagnostic complexity beyond a simple parts replacement (Requirement).","A fixed compliance deadline (before 31 December 1996) creates schedule pressure and potential operational disruption for affected operators (Compliance).","Cross-reference to an FAA AD adds a layer of inter-jurisdictional alignment to consider for operators subject to multiple regulators (Note)."],"plain_english_summary":"What the directive requires (mechanical change)\n\n- The directive requires operators of certain BAe 125 / Hawker 800 aeroplanes to install a specified fuselage fluid drainage modification (Modification 253566G) and to carry out the associated functional test described in Hawker Mandatory Service Bulletin 53-82-3566G Revision 3. (Requirement)\n- If Modification 253566G has already been installed in accordance with a previous issue of the same Service Bulletin and that earlier installation included the functional test to determine whether a bolt fouls the flap control system, no further action is required. (Compliance)\n- The work must be completed before 31 December 1996 unless the exemption above applies. (Compliance)\n\nWhy the directive was issued (official rationale)\n\n- The directive was issued after reports that water had accumulated and then frozen at an aileron pulley located in the lower fuselage aft of the wing rear spar. The ice could restrict aileron control. The requirement implements the service bulletin intended to prevent that condition. (Background)\n\nWho this affects and who pays\n\n- Affected parties: owners/operators of BAe 125 series 800A, series 800B and Hawker 800 aircraft. (Applicability)\n- Who pays: the directive creates an obligation on those operators to have the modification and functional test performed in accordance with the service bulletin. The directive itself does not allocate funding; the cost of compliance therefore falls to the operator unless another arrangement exists. (Requirement, Compliance)\n\nHow it works in practice (incentives, compliance burden, discretion, and risks)\n\n- Incentives and behaviour: Operators must either (a) confirm a qualifying earlier installation including the required functional test, or (b) install the modification and perform the test before the specified deadline. That creates an immediate operational incentive to schedule the work. (Requirement, Compliance)\n- Compliance burden: The directive ties compliance to a specific manufacturer service bulletin (Hawker Mandatory Service Bulletin 53-82-3566G Revision 3), so operators must follow that document’s procedures, including a functional test for bolt interference with the flap control system. The bulletin’s technical steps determine the labour, parts and downtime required. (Requirement)\n- Discretion and exemptions: The only explicit exemption in the text is where the exact modification (253566G) and the functional test were already completed under a previous issue of the same service bulletin. No other discretionary exemptions are stated. (Compliance)\n- Implementation risk and trade-offs: The stated safety risk — frozen water restricting aileron control — is the condition the modification is intended to address. Implementing the required modification and test eliminates or reduces that particular mechanical risk but requires operators to allocate maintenance resources and aircraft downtime. (Background, Requirement)\n- Inter-regulatory note: The directive references a related FAA airworthiness directive (FAA AD 96-12-16 Amdt 39-9659), indicating parallel regulatory activity by another aviation authority. That may affect operators who also must meet foreign regulator requirements. (Note)\n\nNet practical effect\n\n- Mechanically, the instrument imposes a mandatory maintenance/modification task (and a specific functional test) on a narrow set of aircraft models to mitigate a defined freezing-related control risk. The immediate costs (parts, labour, downtime) are borne by the operators; the immediate benefit is reduction of the identified mechanical hazard. (Applicability, Requirement, Background, Compliance)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific aircraft models. It has not expanded beyond its original purpose of mandating a fuselage drainage modification."},"complexity_factors":["Single, specific aircraft type applicability (3 variants only)","References external technical document (Hawker Mandatory Service Bulletin 53-82-3566G Revision 3) without reproducing its contents","Single compliance condition with one exception (already installed modification)","One cross-reference to FAA AD 96-12-16 Amdt 39-9659","No defined terms section — uses standard aviation terminology","Clear, single deadline (31 December 1996)"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety order for aircraft owners and operators.\n\n**What it does:**\nOrders specific modifications to British Aerospace BAe 125 series aircraft (including Hawker 800 models) to fix a dangerous fluid drainage problem in the fuselage.\n\n**The safety problem:**\nWater was accumulating in the lower fuselage and freezing around aileron pulleys (small wheels that guide control cables). This restricted aileron movement — meaning pilots couldn't properly control the aircraft's roll. That's a serious flight safety risk.\n\n**Who must act:**\nOwners and operators of:\n- BAe 125 series 800A\n- BAe 125 series 800B  \n- Hawker 800 aircraft\n\n**What they must do:**\nFollow Hawker Mandatory Service Bulletin 53-82-3566G Revision 3. This involves installing a specific modification (Modification 253566G) and conducting a functional test to check that a bolt doesn't interfere with the flap control system.\n\n**Deadline:**\nBefore 31 December 1996 (unless the modification was already done under an earlier version of the service bulletin).\n\n**Why it matters:**\nFrozen water in flight controls can cause partial or complete loss of roll control. This directive prevents accidents by ensuring proper drainage and eliminating interference risks in the control system."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-155-fuselage-fluid-drainage","history":"/api/acts/ad-hs-125-155-fuselage-fluid-drainage/history","analysis":"/api/acts/ad-hs-125-155-fuselage-fluid-drainage/analysis","conflicts":"/api/acts/ad-hs-125-155-fuselage-fluid-drainage/conflicts","importantCases":"/api/acts/ad-hs-125-155-fuselage-fluid-drainage/important-cases","documents":"/api/acts/ad-hs-125-155-fuselage-fluid-drainage/documents"}}