{"id":"F2006B10390","name":"AD/HS 125/112 - Water System","slug":"ad-hs-125-112-water-system","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116045,"registerId":"commonwealth-F2006B10390-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/112 - Water System","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 125/112 Water System 11/90\n\nApplicability: Model 125-600A, 125-700A, and 125-800A series equipped with a cabin interior and aft lavatory water system installed in accordance with STC SA 2271 SW.\n\nRequirement: Drain all water from the aft lavatory water system reservoir, deactivate the water system pressure pump by pulling the circuit breaker located beneath the vanity in the aft lavatory, and install a tie wrap on the circuit beaker to prevent it from being reset.\n\nNote 1: FAA AD 90-08-07 Amdt 39-6600 refers.\n\nNote 2: Reactivation will be dependent upon the design of a modification that is acceptable to the Authority.\n\nCompliance: Prior to the issue of a Certificate of Airworthiness.\n\nBackground: This Airworthiness Directive is raised in response to a FAA report of an aft lavatory water system leak, which caused the aileron control system to jam due to the resulting ice formation on the aileron control cables and fairleads.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive addressing a specific safety hazard. It has not expanded beyond its original purpose of mitigating the ice formation risk on control cables."},"complexity_factors":["Single, discrete safety directive with only one applicable aircraft type and modification","Clear, sequential compliance steps (3 specific actions)","No defined terms section or complex interpretive provisions","Minimal cross-referencing (only one FAA AD reference and one STC reference)","No conditional logic, exceptions, or nested provisions","Short document (approximately 150 words of substantive content)"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nIt requires owners and operators of certain British Aerospace BAe 125 series business jets (specifically the 600A, 700A, and 800A models with a particular cabin and lavatory setup) to **permanently disable the aft lavatory water system** before the aircraft can be certified as airworthy.\n\n**The specific steps required are:**\n- **Drain** all water from the lavatory water tank\n- **Pull the circuit breaker** for the water pressure pump (located under the vanity)\n- **Secure the circuit breaker** with a tie wrap so it can't accidentally be turned back on\n\n**Why it matters:**\nThis directive was issued after the US Federal Aviation Administration (FAA) reported a dangerous incident where a leak from this water system caused **ice to form on the aileron control cables** — the cables that move the wing flaps that steer the aircraft. The ice jammed the controls, creating a serious flight safety risk. Until a proper fix is designed and approved, the safest solution is to simply disable the system entirely.\n\n**Who it affects:**\nOwners and operators of the specific BAe 125 aircraft models mentioned, particularly those with the STC SA 2271 SW modification (a \"Supplemental Type Certificate\" — official approval for a specific alteration to the aircraft design).\n\n**Key limitation:**\nThe water system can only be reactivated once someone designs a modification that CASA approves as safe."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"Scope remains narrowly targeted to the specified BAe 125 variants with the aft lavatory water system installed under STC SA 2271 SW. The instrument imposes an immediate operational restriction (disable system and secure breaker) until an Authority‑approved modification is available, but does not broaden applicability beyond that stated fleet (Applicability; Requirement; Note 2)."},"complexity_factors":["Narrow applicability: applies only to Model 125-600A/700A/800A with aft lavatory water system installed under STC SA 2271 SW (Applicability).","Simple physical fixes required: draining the reservoir, pulling a circuit breaker and installing a tie-wrap are low-technical tasks (Requirement).","Timing constraint: must be completed before issuance of a Certificate of Airworthiness, creating an operational gate for affected aircraft (Compliance).","Operational consequence: deactivation removes a passenger service, imposing small recurring convenience costs on operators (Requirement).","Reactivation subject to regulatory approval: any reactivation depends on a modification acceptable to the Authority, creating approval/discretion and potential design-costs for owners (Note 2).","Safety-critical origin: directive stems from an incident where water leak → ice → aileron jam, giving the measure a direct and narrowly defined risk trigger (Background).","External reference: cross-references FAA AD 90-08-07, which may influence technical expectations or future compliance actions (Note 1)."],"plain_english_summary":"This directive requires operators of certain British Aerospace BAe 125-600A/700A/800A aircraft fitted with an aft lavatory water system (installed under STC SA 2271 SW) to drain the aft water reservoir, pull the pressure-pump circuit breaker beneath the aft vanity, and secure it with a tie-wrap until an Authority‑approved modification allows reactivation. Compliance must occur before a Certificate of Airworthiness is issued. The measure responds to a reported leak that led to ice formation and aileron control jamming."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-112-water-system","history":"/api/acts/ad-hs-125-112-water-system/history","analysis":"/api/acts/ad-hs-125-112-water-system/analysis","conflicts":"/api/acts/ad-hs-125-112-water-system/conflicts","importantCases":"/api/acts/ad-hs-125-112-water-system/important-cases","documents":"/api/acts/ad-hs-125-112-water-system/documents"}}