{"id":"F2006B10407","name":"AD/HS 125/128 Amdt 1 - Rear Equipment Bay Drain Masts","slug":"ad-hs-125-128-amdt-1-rear-equipment-bay-drain-masts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116077,"registerId":"commonwealth-F2006B10407-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/128 Amdt 1 - Rear Equipment Bay Drain Masts","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 125/128\n\nAmdt 1\n\n  \nRear Equipment Bay Drain Masts 9/92\n\nApplicability: Model 125 Series as listed in BAe 125 SB 53-74-3193 C&D Revision 1. Requirement: Action in accordance with BAe 125 Mandatory SB 53-74-3193 C&D Revision 1.\n\nCompliance: Unless already accomplished in accordance with the initial issue of this Directive; prior to 31 October 1992. The compliance of the previous issue of this Directive is as stated. This Amendment is effective from 20 August 1992.\n\nBackground: Modification action is required in order to provide fluid venting clear of the rear fuselage structure, thereby avoiding the possibility of reingestion. Amendment 1 is issued in response to a revision of the Requirement Document which expands applicability and includes the removal of additional access panels in the accomplishment instructions.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original directive (initial issue) was narrower in scope. Amendment 1 expanded applicability to cover more aircraft models and added extra work (removal of additional access panels) to the accomplishment instructions. This represents modest scope creep typical of safety directive amendments — broadening both who must comply and what they must do."},"complexity_factors":["Very short document (under 200 words)","Only 1 defined term implicitly referenced (the service bulletin)","Single compliance pathway with one deadline","No nested exceptions or conditional logic — straightforward applicability and requirement","Cross-references only to manufacturer service bulletin, not to other legislation"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific repairs or modifications to aircraft.\n\n**What it does:** It orders owners and operators of British Aerospace BAe 125 series business jets to modify the drain masts (pipes that vent fluids) in the rear equipment bay. The modification ensures fluids drain away from the fuselage instead of being sucked back into the aircraft structure (\"reingestion\"), which could cause corrosion or other safety problems.\n\n**Who must comply:** Anyone operating the specific BAe 125 models listed in British Aerospace Service Bulletin 53-74-3193 C&D Revision 1.\n\n**What action is required:** Follow the instructions in the referenced service bulletin exactly — this includes removing extra access panels (a change from the original directive) to complete the work.\n\n**When it had to be done:** Before 31 October 1992 (unless already done under the earlier version of this directive).\n\n**Why it matters:** Fluid reingestion into aircraft structures can cause hidden corrosion, potentially compromising structural integrity. This AD prevents that safety risk by mandating a design fix from the manufacturer."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 1 expands the applicability to include additional BAe 125 Series models (see \"Background\") and revises the accomplishment instructions to include the removal of additional access panels during the modification (see \"Background\"). These changes increase the set of affected aircraft and add steps to the required work, which broadens the Directive’s practical scope relative to the initial issue."},"complexity_factors":["Limited technical scope: applies only to specific BAe 125 Series models listed in the referenced service bulletin (\"Applicability\").","Dependency on an external document: compliance requires following BAe Mandatory SB 53-74-3193 C&D Revision 1, so understanding and executing the SB is necessary (\"Requirement\").","Clear timeline: single compliance deadline (prior to 31 October 1992) and effective date reduce procedural complexity (\"Compliance\").","Amendment increases task steps: removal of additional access panels added in the revised accomplishment instructions increases labour/complexity relative to the original Directive (\"Background\").","No alternative compliance paths or exemptions presented in the text, so operators must follow the SB procedure as written (\"Requirement\")."],"plain_english_summary":"This AD mandates a specific modification to rear equipment-bay drain masts on certain British Aerospace BAe 125 Series aeroplanes, to be carried out exactly per BAe Mandatory SB 53-74-3193 C&D Revision 1. Affected owners/operators must comply (deadline: prior to 31 October 1992; amendment effective 20 Aug 1992). The change—which expands applicability and adds removal of extra access panels—routes fluid venting clear of the rear fuselage to prevent fluid reingestion; costs and downtime are borne by operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-128-amdt-1-rear-equipment-bay-drain-masts","history":"/api/acts/ad-hs-125-128-amdt-1-rear-equipment-bay-drain-masts/history","analysis":"/api/acts/ad-hs-125-128-amdt-1-rear-equipment-bay-drain-masts/analysis","conflicts":"/api/acts/ad-hs-125-128-amdt-1-rear-equipment-bay-drain-masts/conflicts","importantCases":"/api/acts/ad-hs-125-128-amdt-1-rear-equipment-bay-drain-masts/important-cases","documents":"/api/acts/ad-hs-125-128-amdt-1-rear-equipment-bay-drain-masts/documents"}}