{"id":"F2006B09969","name":"AD/FSM/22 - POSA Carburettor - Modification","slug":"ad-fsm-22-posa-carburettor-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55249,"registerId":"commonwealth-F2006B09969-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/FSM/22 - POSA Carburettor - Modification","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nFuel Supply and Metering Equipment\n\nAD/FSM/22 POSA Carburettor \\- Modification 5/83\n\nApplicability: All model Posa Carburettors as fitted to converted V.W. Engines. These carburettors may be fitted to, but not necessarily confined to the Revmaster and H.A.P.1 V.W. Conversion ranges of engines.\n\nRequirement: (i) Incorporate Revmaster Bulletin No. 001 \"Injector Rework\" dated 30 July 1973.\n\n    (ii) Lockwire choke idle screw.\n\n    (iii) Lock all body screws.\n\n    (iv) Provide overboard drain, well clear of exhaust, to drain throttle valve of excess fuel during start up.\n\nCompliance: Engines in Service: Within ten hours in service after 31 May 1983\\. New Engines: Before issue of Permit to Fly.\n\nBackground: This Directive was originally issued as part of AD/REV/4 pertaining to Revmaster engines. It is now issued under subject heading to cover all Posa Carburettors fitted to any converted V.W. engine. A Posa Carburettor Service Bulletin issued by the Hapi Engine Organisation and dated February 23, 1983 reports of two inflight fuel starvation incidents caused by the main metering needle turning in flight. While the Posa (Hapi) Bulletin proposes that certain inspection actions be taken to obviate further incidents of this nature it should be accepted that the modification action required by this Directive is a more positive and long term answer for overcoming this problem.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"Originally this directive only applied to Revmaster engines (AD/REV/4). It was reissued under a broader subject heading to cover ALL Posa Carburettors fitted to ANY converted Volkswagen engine, expanding from a single manufacturer to a category of equipment regardless of who manufactured or installed it."},"complexity_factors":["Single, discrete subject matter (one carburettor type on specific engines)","Only 4 specific technical requirements, clearly numbered","No defined terms section or interpretation provisions","No cross-references to other legislation (only references to manufacturer bulletins)","Simple binary applicability test (does the aircraft have this carburettor?)","Straightforward compliance deadlines with no conditional exceptions","Background section provides clear rationale without legal caveats","Total length is approximately 250 words"],"plain_english_summary":"This CASA Airworthiness Directive mandates modifications to Posa carburettors on converted Volkswagen aircraft engines (notably Revmaster and H.A.P.1 conversions) because the metering needle can rotate in flight and cause fuel starvation. \n\nOperators must install specific hardware changes and secure screws/drains within the stated deadlines (existing aircraft within 10 flight hours after 31 May 1983; new aircraft before first flight) to prevent in‑flight engine failure and possible crashes."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Scope was broadened. The Directive was originally part of AD/REV/4 for Revmaster engines but is reissued to cover all Posa carburettors fitted to any converted V.W. engine (Background)."},"complexity_factors":["Technical specificity: mandates defined mechanical actions (lockwiring, locking body screws, provide overboard drain) that require skilled maintenance (Requirement).","Cross-reference to external material: requires incorporation of Revmaster Bulletin No.001, creating dependency on a separate document for procedural details (Requirement).","Narrow, safety‑critical scope: affects a limited class of carburettors but involves in‑service safety risk and regulatory enforcement (Applicability; Background).","Short compliance window: ten hours in service for existing engines and before Permit to Fly for new engines increases scheduling and operational impact (Compliance).","Applicability wording: phrase 'may be fitted to, but not necessarily confined to' introduces some ambiguity about exact fleet coverage (Applicability).","Implementation cost and downtime: physical modifications and inspections impose direct costs on owners/operators and workload on maintenance providers (Requirement; Compliance)."],"plain_english_summary":"This directive requires modification of all Posa carburettors fitted to converted Volkswagen engines to reduce the risk of in‑flight fuel starvation. It compels incorporation of a Revmaster service rework and fixes to prevent parts loosening and fuel pooling.\n\nIt applies to aircraft owners/operators and maintenance organisations; compliance is required within ten hours for engines in service and before issue of a Permit to Fly for new engines. The stated purpose is to stop main metering needles turning in flight (Background)."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-fsm-22-posa-carburettor-modification","history":"/api/acts/ad-fsm-22-posa-carburettor-modification/history","analysis":"/api/acts/ad-fsm-22-posa-carburettor-modification/analysis","conflicts":"/api/acts/ad-fsm-22-posa-carburettor-modification/conflicts","importantCases":"/api/acts/ad-fsm-22-posa-carburettor-modification/important-cases","documents":"/api/acts/ad-fsm-22-posa-carburettor-modification/documents"}}