{"id":"F2006B09774","name":"AD/F28/36 - APU Enclosure Fuel Drain - Modification","slug":"ad-f28-36-apu-enclosure-fuel-drain-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54676,"registerId":"commonwealth-F2006B09774-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F28/36 - APU Enclosure Fuel Drain - Modification","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)  Fokker F28 Series Aeroplanes\n\n \n\nAD/F28/36 APU Enclosure Fuel Drain - Modification 11/77\n\nApplicability: All models with S/Nos. 11003 to 11131 and 11991 to 11993. Document:  1. Fokker SB F28/49-25; or\n\n2. RLD AD A102/77.\n\n \n\nCompliance: Before 30 April 1978.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive from 1977 with a single specific purpose. It has not expanded beyond its original scope of requiring a specific modification to address a fuel drainage issue in Fokker F28 aircraft."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined references (the Fokker Service Bulletin and RLD AD)","Simple applicability criteria (specific serial number ranges)","Single compliance deadline with no conditional extensions or exceptions","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1988","No nested conditions or 'unless' clauses"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by the Civil Aviation Safety Authority (CASA) requiring specific repairs or modifications to aircraft.\n\n**What it does:** It orders owners and operators of certain **Fokker F28 series aeroplanes** to modify the fuel drain system in the Auxiliary Power Unit (APU) enclosure. The APU is a small engine that provides power when the main engines are off. The modification prevents fuel from accumulating in the APU enclosure, which could create a fire or explosion risk.\n\n**Who it affects:** \n- **Aircraft models:** All Fokker F28 models with **serial numbers 11003 to 11131 and 11991 to 11993**\n- **People affected:** Airlines, aircraft owners, and maintenance organisations operating these specific aircraft\n\n**What must be done:**\n- Follow the instructions in **Fokker Service Bulletin F28/49-25** OR the **Dutch aviation authority's directive RLD AD A102/77**\n- Complete the modification **before 30 April 1978**\n\n**Why it matters:** Fuel leaks in enclosed spaces near heat sources are a serious safety hazard. This directive ensures a known design flaw is fixed before it can cause an accident."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied text contains a single, focused requirement: modify the APU enclosure fuel drain on specified Fokker F28 serial numbers by a fixed date using one of two referenced technical documents. The text does not indicate any amendment or expansion of scope from an earlier version within the supplied material, so there is no sign that the scope has changed from the directive as presented here."},"complexity_factors":["Narrow applicability limited to specific serial number ranges reduces legal and operational complexity.","Clear, single deadline (30 April 1978) simplifies timing requirements.","Directive does not include technical instructions and relies on two external documents (Fokker SB F28/49-25 or RLD AD A102/77), creating a dependency on those documents for implementation details.","No exemptions, alternative compliance routes, enforcement mechanisms, or cost allocation rules are stated in the supplied text, which simplifies the AD but leaves practical implementation questions to normal maintenance/authority processes.","The short text leaves ambiguity about administrative details (who pays, how compliance is recorded) which shifts complexity into operational/administrative practices rather than the directive’s substance."],"plain_english_summary":"What this directive requires\n\n- The Civil Aviation Safety Authority has issued an airworthiness directive titled \"AD/F28/36 APU Enclosure Fuel Drain - Modification\" (11/77). (Header)\n- It requires a physical modification to the APU (auxiliary power unit) enclosure fuel drain on certain Fokker F28 aeroplanes. The directive does not include the step‑by‑step modification instructions itself; it refers to external documents for the technical work: Fokker Service Bulletin F28/49‑25 or RLD AD A102/77. (Document)\n- The directive applies only to aeroplanes with serial numbers 11003 to 11131 and 11991 to 11993. (Applicability)\n- Operators of those aircraft must complete the modification before 30 April 1978. (Compliance)\n\nWho is affected and who decides\n\n- The named operators/owners of the specific Fokker F28 aircraft listed in the Applicability section are the parties required to act. The directive appears in the Civil Aviation Safety Authority schedule of airworthiness directives, indicating CASA issued the requirement. (Header; Applicability)\n\nHow it works mechanically\n\n- The directive makes compliance mandatory for the listed serial numbers by a fixed deadline. It does not itself contain detailed technical steps; instead it mandates following one of two external technical documents. (Document; Compliance)\n\nStated purpose and how that compares to practical effects\n\n- The directive’s title identifies the subject as the APU enclosure fuel drain modification. The directive does not set out an explicit rationale within the text supplied here. (Header)\n- Practically, the requirement forces owners/operators of the listed aircraft either to carry out the specified modification or to follow whatever maintenance/airworthiness process is needed to demonstrate compliance by the deadline. (Applicability; Document; Compliance)\n\nCosts, incentives and operational trade‑offs (source‑grounded)\n\n- Compliance imposes an action requirement on a narrowly defined group of aircraft (those serial numbers). The AD creates a time‑limited obligation that operators must satisfy before the stated date, which will require scheduling maintenance resources and using the referenced technical documents. (Applicability; Document; Compliance)\n- The directive itself does not specify who pays, how costs are to be recovered, or enforcement measures for non‑compliance. Those matters are not stated in the text supplied. (Entire text)\n- Because the AD relies on external service/repair documents, operators must obtain and follow those documents to complete the mandated work; the need to reference external material is a source of implementation dependency. (Document)\n\nCompliance burden and discretion\n\n- The burden is concentrated on operators of the specified serial‑numbered aircraft. The directive sets the mandatory requirement and deadline; it does not, in the supplied text, assign discretionary exemptions or alternative means of compliance. Any such discretion would need to be sought from the issuing authority or would be set out elsewhere. (Applicability; Compliance)\n\nNet operational effect (mechanical, not evaluative)\n\n- If complied with, the specified modification will have been carried out on the listed aircraft by the deadline using one of the two referenced documents. The directive changes the maintenance obligations for those serial numbers for the specific item named (APU enclosure fuel drain). (Header; Document; Applicability; Compliance)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f28-36-apu-enclosure-fuel-drain-modification","history":"/api/acts/ad-f28-36-apu-enclosure-fuel-drain-modification/history","analysis":"/api/acts/ad-f28-36-apu-enclosure-fuel-drain-modification/analysis","conflicts":"/api/acts/ad-f28-36-apu-enclosure-fuel-drain-modification/conflicts","importantCases":"/api/acts/ad-f28-36-apu-enclosure-fuel-drain-modification/important-cases","documents":"/api/acts/ad-f28-36-apu-enclosure-fuel-drain-modification/documents"}}