{"id":"F2006B10329","name":"AD/GULL/2 - Rear Fuselage Drain Holes","slug":"ad-gull-2-rear-fuselage-drain-holes","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56085,"registerId":"commonwealth-F2006B10329-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/GULL/2 - Rear Fuselage Drain Holes","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)  Percival Vega Gull Series Aeroplanes\n\n \n\nAD/GULL/2 Rear Fuselage Drain Holes 9/71\n\nApplicability: All models.\n\n \n\nDocument: 1. Percival Mod. No. 210; or\n\n \n\n2. ANO 105.1.26.0.2.2.\n\n \n\nCompliance: Forthwith.\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\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD text, as provided, applies to \"All models\" of the Percival Vega Gull and mandates compliance with the two named documents \"Forthwith.\" There is no indication in the provided text that the AD's scope has been changed from an earlier stated intent or altered scope; the instrument narrowly prescribes compliance by reference and covers all models as set out in the \"Applicability\" line."},"complexity_factors":["Brevity of the AD text — the directive itself contains minimal technical detail, making the instruction simple in form but shifting complexity to external documents (see \"Document\").","Reference to external documents — required actions are defined only by Percival Mod. No. 210 or ANO 105.1.26.0.2.2, so compliance requires obtaining and interpreting those documents (see \"Document\").","Immediate compliance requirement — the term \"Forthwith\" compresses available time for planning and execution, increasing practical complexity in scheduling and logistics (see \"Compliance: Forthwith\").","Clear applicability — the AD applies to all models, which simplifies the coverage question but broadens the population of affected aircraft (see \"Applicability: All models.\")"],"plain_english_summary":"- What this instrument does mechanically\n  - This is an Airworthiness Directive (AD) titled \"AD/GULL/2 — Rear Fuselage Drain Holes\" that requires operators to follow the corrective or modification action described in one of two documents listed under \"Document\". The AD applies to all Percival Vega Gull series aeroplanes (\"Applicability: All models.\") and must be complied with immediately (\"Compliance: Forthwith.\").\n\n- Who it affects\n  - Owners and operators of Percival Vega Gull series aeroplanes (all models). Maintenance organisations and engineers who perform aircraft modifications or inspections will also be affected because they will need to carry out the work set out in the referenced documents (see \"Applicability\" and \"Document\").\n\n- What the AD requires and how it works\n  - The AD does not set out step‑by‑step instructions in the text of the instrument. Instead it directs compliance by reference to either: Percival Mod. No. 210; or ANO 105.1.26.0.2.2 (see \"Document\"). Those referenced documents are the operative instructions. The AD makes compliance mandatory and immediate (see \"Compliance: Forthwith\").\n\n- Official rationale in the source\n  - The AD text itself does not include an explicit statement of the safety problem or the regulator's reasons for issuing the directive. The title identifies the subject as \"Rear Fuselage Drain Holes,\" which indicates the location of the work, but the AD does not set out the hazard or risk assessment in this text.\n\n- Practical consequences, incentives and trade‑offs (source‑grounded)\n  - Who pays and who decides: Owners/operators must arrange and pay for whatever work is required by the referenced documents. The AD vests the decision to implement the specified corrective action in the persons who carry out maintenance and the operator, subject to the AD's mandatory requirement (see \"Document\" and \"Compliance\").\n  - Compliance burden: Because the AD does not include detailed instructions in its text, operators must obtain and follow one of the two referenced documents to know the exact tasks, parts and labour required. That creates additional administrative steps — acquiring the documents and scheduling the work — and likely direct costs for parts and labour (see \"Document\").\n  - Timing pressure and implementation risk: The directive requires action \"Forthwith,\" which reduces the time available to plan and execute the work and to source parts or specialised maintenance services. That timing requirement raises the risk of short‑term scheduling pressures for owners and maintenance providers (see \"Compliance: Forthwith\").\n  - Effects on private providers and markets: Because the AD mandates specified maintenance/modification actions, maintenance organisations that service these aeroplanes are the parties that will perform the work. The AD therefore creates immediate demand for whatever skills, parts or materials the referenced documents require. The AD text itself does not specify parts or suppliers (see \"Document\").\n  - Bureaucratic discretion: The AD is prescriptive in mandating compliance by reference to named documents; it does not, in its published text, leave discretionary options to the operator about whether to comply. Any discretionary assessment (for example, assessing whether a particular aircraft already complies) will depend on interpreting the referenced documents (see \"Document\").\n\n- Costs, trade‑offs and opportunity costs (source‑grounded)\n  - Direct costs will fall on owners/operators because the AD makes compliance mandatory and requires following the documents named. Those costs could include parts, labour and aircraft downtime. The AD itself does not state an indemnity, funding arrangement or fee exemption (no such provision appears in the text provided). The AD does not state alternative measures or exemptions; the only compliance route set out is by following one of the two referenced documents (see \"Document\" and \"Compliance\").\n\n- Uncertainties and implementation notes\n  - The AD text is brief and relies entirely on external documents for the technical content. That reliance means that to determine the precise scope of work, costs and parts required, an operator must obtain and review Percival Mod. No. 210 or ANO 105.1.26.0.2.2. The AD provides no timeframe beyond \"Forthwith,\" and no procedural detail for demonstrating compliance in the published text (see \"Document\" and \"Compliance\").\n\n- Bottom line (mechanical description)\n  - The AD immediately obliges all Percival Vega Gull operators to carry out whatever corrective/modification work is set out in Percival Mod. No. 210 or ANO 105.1.26.0.2.2, with administrative and cost consequences falling to the operators and the maintenance providers who perform the work (see \"Applicability,\" \"Document,\" and \"Compliance\")."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1971 addressing a specific structural modification. It has not expanded beyond its original purpose of ensuring proper drainage in the rear fuselage of Percival Vega Gull aircraft."},"complexity_factors":["Extremely short document — approximately 100 words of substantive content","Only 2 defined compliance paths (Percival Mod. No. 210 or ANO reference)","No conditional logic, exceptions, or nested provisions","Single, unambiguous applicability clause (\"All models\")","No cross-references to other legislation beyond the two cited documents","Uses archaic regulatory language (\"Forthwith\", \"ANO\") but meaning is clear in context"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order — issued by Australia's Civil Aviation Safety Authority (CASA) for **Percival Vega Gull series aeroplanes**.\n\n**What it does:**\n- Requires owners/operators of these vintage aircraft to modify the rear fuselage by adding or ensuring proper drain holes.\n- The modification must follow either **Percival Modification No. 210** (the manufacturer's official fix) or **ANO 105.1.26.0.2.2** (an older British Airworthiness Notice).\n\n**Who it affects:**\n- Anyone who owns, operates, or maintains a Percival Vega Gull aircraft in Australia.\n\n**Why it matters:**\n- Drain holes prevent water accumulation in the rear fuselage, which can cause corrosion, structural weakness, or control system failures. This is a **safety-critical** issue — water trapped in airframes has caused accidents.\n- The directive uses the word **\"Forthwith\"** — meaning compliance is **immediate**, with no grace period.\n\n**Key point:** This AD dates from **September 1971** (the \"9/71\" in the reference), showing how long-standing safety requirements remain binding on the Australian aircraft register indefinitely unless explicitly cancelled."}},"importantCases":[],"_links":{"self":"/api/acts/ad-gull-2-rear-fuselage-drain-holes","history":"/api/acts/ad-gull-2-rear-fuselage-drain-holes/history","analysis":"/api/acts/ad-gull-2-rear-fuselage-drain-holes/analysis","conflicts":"/api/acts/ad-gull-2-rear-fuselage-drain-holes/conflicts","importantCases":"/api/acts/ad-gull-2-rear-fuselage-drain-holes/important-cases","documents":"/api/acts/ad-gull-2-rear-fuselage-drain-holes/documents"}}