{"id":"F2006B09743","name":"AD/F27/90 Amdt 1 - Pneumatic Isolating Valves - Inspection","slug":"ad-f27-90-amdt-1-pneumatic-isolating-valves-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115945,"registerId":"commonwealth-F2006B09743-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F27/90 Amdt 1 - Pneumatic Isolating Valves - Inspection","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)  \nFokker F27 Series Aeroplanes\n\nAD/F27/90\n\nAmdt 1\n\n  \nPneumatic Isolating Valves \\- Inspection 7/77\n\nApplicability: All models fitted with pneumatic isolating valves, Dunlop Aviation Division P/N ACM 17892 or ACM 26214.\n\nRequirement: Inspect using a method approved by the Secretary, pneumatic isolating valves, Dunlops Aviation Division P/N ACM 17892 or ACM 26214, for presence of cracks around internal circumference of body, P/N ACM 16724, ACO 22631 or ACM 26573 in area of undercut in main body chamber. Valve bodies showing crack indications extending through more than one third of the wall thickness must be replaced before further flight.\n\nCompliance: Within 250 hours time in service after 31 March 1977 and thereafter at intervals not exceeding 2400 hours time in service.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"This amendment (Amdt 1 to AD/F27/90) imposes mandatory inspection and replacement requirements for specific pneumatic isolating valves and valve bodies fitted to Fokker F27 aeroplanes (Applicability; Requirement; Compliance). Mechanically, it defines who is covered (specified P/Ns), what must be done (inspect by a method approved by the Secretary; replace bodies with cracks exceeding one third wall thickness), and when inspections must occur (initially within 250 hours after 31 March 1977 and thereafter at intervals not exceeding 2400 hours TIS). The amendment therefore changes the operational scope for owners/operators of affected aircraft by adding these specified inspection and replacement obligations."},"complexity_factors":["Narrow technical scope: applies only to specific Dunlop valve P/Ns on Fokker F27 aircraft (Applicability).","Clear, single mechanical requirement: inspect for cracks and replace at a quantified threshold (>1/3 wall thickness) (Requirement).","Regulatory discretion point: Secretary must approve the inspection method, introducing administrative choice (Requirement).","Timing rule uses time-in-service hours with a historical reference date, which requires operators to map calendar dates to flight hours (Compliance).","Implementation depends on reliably measuring crack depth, which can introduce technical inspection complexity despite simple textual requirements (Requirement)."],"plain_english_summary":"This AD requires owners/operators of Fokker F27s fitted with specified Dunlop pneumatic isolating valves to inspect valve bodies (using an inspection method approved by the Secretary) for internal cracks and to replace any valve body with a crack through more than one‑third of wall thickness before further flight. First inspection within 250 flight hours after 31 Mar 1977, then every 2400 hours. Operators bear inspection, replacement and downtime costs."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, targeted safety directive addressing a specific mechanical defect in specific aircraft. It has not expanded beyond its original purpose of ensuring pneumatic valve integrity in Fokker F27 operations."},"complexity_factors":["Single, specific technical requirement with clear pass/fail criteria (crack depth > 1/3 wall thickness)","Only 2 part numbers affected, with 3 specific body part numbers referenced","Simple compliance timeline: one initial deadline plus recurring interval","No nested exceptions, conditional logic, or cross-references to other legislation","Total length: approximately 150 words","Single applicability criterion (aircraft model + specific part installation)"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety order issued by Australia's aviation safety regulator (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners and operators of **Fokker F27 aircraft** to inspect certain **pneumatic isolating valves** (parts that control air pressure in the plane's systems) for dangerous cracks.\n\n**Who it affects:**\nAnyone operating Fokker F27 planes fitted with specific Dunlop valve parts (part numbers ACM 17892 or ACM 26214).\n\n**The specific safety risk:**\nThe valve bodies can develop cracks around their internal circumference. If a crack extends through more than one-third of the wall thickness, the valve must be replaced before the aircraft flies again.\n\n**When to comply:**\n- First inspection: within 250 flight hours after 31 March 1977\n- Repeat inspections: every 2,400 flight hours thereafter\n\n**Why it matters:**\nCracked pneumatic valves could fail in flight, potentially causing loss of critical air pressure systems. This directive prevents catastrophic failure by catching cracks early."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f27-90-amdt-1-pneumatic-isolating-valves-inspection","history":"/api/acts/ad-f27-90-amdt-1-pneumatic-isolating-valves-inspection/history","analysis":"/api/acts/ad-f27-90-amdt-1-pneumatic-isolating-valves-inspection/analysis","conflicts":"/api/acts/ad-f27-90-amdt-1-pneumatic-isolating-valves-inspection/conflicts","importantCases":"/api/acts/ad-f27-90-amdt-1-pneumatic-isolating-valves-inspection/important-cases","documents":"/api/acts/ad-f27-90-amdt-1-pneumatic-isolating-valves-inspection/documents"}}