{"id":"F2006B04243","name":"AD/BEECH 90/55 - Oxygen System - Inspection","slug":"ad-beech-90-55-oxygen-system-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44022,"registerId":"commonwealth-F2006B04243-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BEECH 90/55 - Oxygen System - 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)  \nBeechcraft 90 and 65-90 (King Air) Series Aeroplanes\n\nAD/BEECH 90/55 Oxygen System \\- Inspection 8/80\n\nApplicability: All models with S/Nos. LJ-490 to LJ-667 and LW-1 to LW-326, not modified in accordance with Beechcraft SI No. 0867-341, Rev. 2.\n\nRequirement: 1. Fabricate a placard using letters at least 3 mm high to read as follows :\n\n“Flight above 25,000 feet prohibited unless oxygen system is ARMED (ON)”.\n\n2. Install this placard in clear view of the pilot and operate the aircraft in accordance with this limitation.\n\nCompliance: Within the next 50 hours’ time in service after 16 July 1980.\n\nBackground: Overseas experience has shown that this requirement is necessary to prevent seizure and binding of the oxygen control cable due to freezing of contaminating moisture which will interfere with activation of the oxygen system.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused on a specific safety modification for a defined aircraft population. It has not expanded beyond its original purpose of addressing the oxygen system freezing risk."},"complexity_factors":["Single, specific applicability criterion based on aircraft serial numbers","Two simple, sequential requirements (fabricate placard, install placard)","No defined terms section","No cross-references to other legislation or regulations beyond the enabling regulation (CAR 1998 Part 39)","Single compliance deadline with clear calculation method (50 hours time in service after fixed date)","Straightforward background explanation without technical sub-paragraphs"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for specific Beechcraft King Air aircraft.\n\n**What it does:**\n- Requires owners/operators of certain Beechcraft 90 and 65-90 series planes to **install a warning placard** in the cockpit\n- The placard must state: *\"Flight above 25,000 feet prohibited unless oxygen system is ARMED (ON)\"*\n- The text must be at least **3 mm high**\n- The placard must be placed where the pilot can clearly see it\n\n**Who it affects:**\n- Owners and operators of Beechcraft King Air aircraft with serial numbers LJ-490 to LJ-667 and LW-1 to LW-326\n- **Excludes** aircraft already modified according to Beechcraft Service Instruction No. 0867-341, Revision 2\n\n**Why it matters:**\n- Overseas incidents showed that moisture contamination in the oxygen control cable can freeze at high altitude, causing the cable to seize or bind\n- This prevents the oxygen system from activating when needed — a serious safety risk if cabin pressure is lost above 25,000 feet\n- The placard ensures pilots keep the oxygen system armed (turned on) before flying high, preventing the freezing issue\n\n**Deadline:** Must be completed within the next 50 hours of flight time after 16 July 1980."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive implements a targeted operational limitation and cockpit placard to address the risk described in the Background (freezing of contaminating moisture causing oxygen control cable seizure). It does not broaden the affected fleet beyond the serial numbers listed or impose additional unrelated obligations; instead it provides a specific, limited requirement and notes a modification exemption (Applicability; Requirement). Therefore the scope remains aligned with the stated safety concern and does not change beyond that original, stated intent."},"complexity_factors":["Narrow applicability limited to specific serial number ranges and an explicit modification exception (Applicability)","Single, simple corrective action (fabricate and install a placard) with a straightforward operational requirement (Requirement 1; Requirement 2)","Short, explicit compliance timeframe stated (Compliance)","Dependence on human compliance (pilots observing placard) rather than technical retrofit introduces monitoring/enforcement considerations (Requirement 2; Background)","Presence of an alternative path (airframes modified per Beechcraft SI No. 0867-341, Rev. 2 are excluded) adds a small decision point for owners (Applicability)"],"plain_english_summary":"This directive requires operators of specified Beechcraft 90 and 65‑90 serials to install a cockpit placard reading “Flight above 25,000 feet prohibited unless oxygen system is ARMED (ON)” and to comply with that limitation; aircraft modified per Beechcraft SI 0867‑341 Rev.2 are excluded. \n\nIt responds to overseas reports that moisture freezing can seize the oxygen control cable, so the placard forces a procedural mitigation rather than immediate hardware retrofit."}},"importantCases":[],"_links":{"self":"/api/acts/ad-beech-90-55-oxygen-system-inspection","history":"/api/acts/ad-beech-90-55-oxygen-system-inspection/history","analysis":"/api/acts/ad-beech-90-55-oxygen-system-inspection/analysis","conflicts":"/api/acts/ad-beech-90-55-oxygen-system-inspection/conflicts","importantCases":"/api/acts/ad-beech-90-55-oxygen-system-inspection/important-cases","documents":"/api/acts/ad-beech-90-55-oxygen-system-inspection/documents"}}