{"id":"F2006B04931","name":"AD/CESSNA 150/33 Amdt 1 - Vented Fuel Caps","slug":"ad-cessna-150-33-amdt-1-vented-fuel-caps","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44776,"registerId":"commonwealth-F2006B04931-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 150/33 Amdt 1 - Vented Fuel Caps","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)  \nCessna 150, F150, 152 & F152 Series Aeroplanes\n\nAD/CESSNA 150/33\n\nAmdt 1\n\n  \nVented Fuel Caps 8/80\n\nApplicability: Model 150 with S/Nos. 617, 628, 649, 17001 to 17999, 59001 to 59018 and 15059019 to 15077005. Model A150 with S/Nos. 15064970 and A1500001 to A1500609.\n\nRequirement: Install vented fuel cap(s) in accordance with:\n\n1. Cessna SL No. SE 77-6; or\n\n2. FAA AD 79-10-14, Amendment 39-3475; or\n\n3. Bureau Veritas AD 79-155-IMP(A).\n\nNote: Installation of a placard is not an acceptable alternative to installation of vented fuel caps.\n\nCompliance: Within 100 hours time in service after 31 August 1979, or before 1 January 1980, whichever is later.\n\nBackground: To guard against the possibility of either an obstructed primary vent or sticking of the fuel tank vent valve it has been found necessary to provide secondary venting in the form of vented fuel caps. Due to some misinterpretation of this Directive a NOTE has now been added to disallow the fitting of a placard.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing Airworthiness Directive. The amendment is narrow and surgical — it adds a single Note clarifying that placards are not an acceptable alternative to vented caps. This addresses 'misinterpretation' of the original directive but does not expand the scope beyond the original safety purpose (ensuring proper fuel tank venting)."},"complexity_factors":["Single, specific mechanical requirement (install vented caps)","Limited applicability — only specific serial numbers of one aircraft family","Three alternative compliance methods provided (Cessna SL, FAA AD, or Bureau Veritas AD)","One explicit prohibition (placards not acceptable)","Simple compliance deadline structure (hours OR date)","No nested definitions, cross-references to other legislation, or conditional exceptions","Total length: approximately 200 words"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for specific **Cessna 150 series aircraft**.\n\n**What it does:**\n- Requires owners/operators of certain Cessna 150, F150, 152 and F152 aeroplanes to **install vented fuel caps** on their fuel tanks.\n\n**Why it matters:**\n- The original fuel system design had a flaw: the primary fuel tank vent could become blocked, or the vent valve could stick shut. This could create a vacuum in the fuel tank, starving the engine of fuel and potentially causing engine failure in flight.\n- The vented fuel caps provide a **backup (secondary) venting system** to prevent this dangerous situation.\n\n**Who must comply:**\n- Owners of specific Cessna models with particular serial numbers listed in the \"Applicability\" section (covering various production batches from the 1950s through 1970s).\n\n**What you must do:**\n- Replace the standard fuel caps with vented ones following one of three approved technical documents (Cessna Service Letter, FAA Airworthiness Directive, or Bureau Veritas directive).\n- **Important:** Simply putting a warning label (placard) on the aircraft is **not acceptable** — you must actually install the vented caps.\n\n**When:**\n- The work had to be completed by a specific deadline based on flight hours or calendar date (whichever came later)."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"Amendment clarifies and narrows acceptable compliance methods by adding a NOTE that disallows fitting a placard as an alternative. The original directive required secondary venting; this amendment removes a previously misinterpreted substitute (placard), leaving only physical installation per the listed documents."},"complexity_factors":["Narrow, specific applicability limited to particular Cessna 150/A150 serial numbers (low breadth).","Single, prescriptive technical remedy (install vented fuel caps) with three equivalent referenced documents to follow.","Short, firm compliance deadline (100 hours after 31 Aug 1979 or before 1 Jan 1980) — minimal scheduling complexity.","Explicit prohibition of an alternative measure (placard), reducing interpretive ambiguity.","No multi-step approvals, exemptions, or ongoing reporting requirements specified."],"plain_english_summary":"Requires owners/operators of specified Cessna 150 and A150 serial-numbered aeroplanes to install vented fuel caps by following one of three listed Cessna/FAA/Bureau Veritas documents. Compliance is due within 100 hours’ time-in-service after 31 August 1979 or before 1 January 1980, whichever is later.\n\nA placard is explicitly not an acceptable alternative. The cost and compliance burden fall to aircraft owners to add secondary venting to protect against obstructed vents or a sticking tank vent valve."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-150-33-amdt-1-vented-fuel-caps","history":"/api/acts/ad-cessna-150-33-amdt-1-vented-fuel-caps/history","analysis":"/api/acts/ad-cessna-150-33-amdt-1-vented-fuel-caps/analysis","conflicts":"/api/acts/ad-cessna-150-33-amdt-1-vented-fuel-caps/conflicts","importantCases":"/api/acts/ad-cessna-150-33-amdt-1-vented-fuel-caps/important-cases","documents":"/api/acts/ad-cessna-150-33-amdt-1-vented-fuel-caps/documents"}}