{"id":"F2006B04245","name":"AD/BEECH 90/57 Amdt 4 - Fuselage Fatigue Life Limitations","slug":"ad-beech-90-57-amdt-4-fuselage-fatigue-life-limitations","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44026,"registerId":"commonwealth-F2006B04245-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BEECH 90/57 Amdt 4 - Fuselage Fatigue Life Limitations","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 90/57\n\nAmdt 4\n\n  \nFuselage Fatigue Life Limitations 4/85\n\nApplicability: All model F90 series.\n\nRequirement: 1. Retire the cabin door upper locking pins P/N 50-430177-3 and lower locking pins P/N 50-430018-9 from service.\n\n2. Retire the pressure cabin from service.\n\nCompliance: 1. For Para. 1 \\- Upon or prior to the locking pins achieving 4500 pressurised flight cycles.\n\n2. For Para. 2 \\- Before exceeding 8200 pressurised flights.\n\nNote: These lives may be revised following the completion of further tests and analysis currently being carried out by the manufacturer.\n\nBackground: This amendment deletes the retirement life requirements for cabin and cockpit side windows. All model F90 aircraft now have the stretched acrylic failsafe windows installed, AD/Beech 90/70 refers.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"The legislation maintains its original narrow scope — regulating fatigue life limits for specific components on a single aircraft model. The amendment actually narrows the scope slightly by removing window retirement requirements, but this reflects updated technical knowledge rather than scope creep."},"complexity_factors":["Very short document (under 200 words)","Only 2 defined part numbers (P/N 50-430177-3 and P/N 50-430018-9)","Simple conditional structure: two compliance deadlines tied to flight cycle counts","No cross-references to other legislation (only a note about a related directive)","Single amendment note explaining what was deleted from previous version","Clear applicability statement limiting scope to one aircraft model series"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific repairs, inspections, or modifications to aircraft.\n\n**What it does:**\nThis directive sets strict \"retirement\" deadlines (permanent removal from use) for two critical components on Beechcraft King Air F90 series aircraft:\n\n- **Cabin door locking pins** (upper and lower) — must be retired after **4,500 pressurised flights**\n- **The entire pressure cabin** — must be retired after **8,200 pressurised flights**\n\n**Who it affects:**\nOwners and operators of all **Beechcraft F90 series** aircraft (a twin-turboprop business aircraft commonly used for corporate transport, medical evacuation, and regional airline services).\n\n**Why it matters:**\nThese limits exist because pressurised cabins experience repeated stress cycles that eventually cause metal fatigue — microscopic cracks that can lead to catastrophic structural failure. The directive prevents potential decompression accidents by forcing retirement of these components before they reach dangerous fatigue levels.\n\n**Key change in this version:**\nThis amendment (version 4) **removes** previous retirement requirements for cabin and cockpit side windows, because newer \"stretched acrylic failsafe\" windows are now standard on all F90 aircraft (covered by a separate directive, AD/Beech 90/70)."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"This amendment removed the retirement life requirements for the cabin and cockpit side windows that had been in earlier versions and notes those windows are now fitted with stretched acrylic failsafe windows; those window items are handled under AD/Beech 90/70 (Background). The amendment retains and sets explicit retirement lives for the cabin door locking pins and the pressure cabin (Requirement; Compliance)."},"complexity_factors":["Straightforward numerical retirement limits (4,500 cycles for pins; 8,200 pressurised flights for pressure cabin) reduce legal ambiguity.","Technical requirement depends on accurately tracking 'pressurised flight cycles', an operational metric that requires reliable recordkeeping.","Specificity to component part numbers increases enforceability but requires operators to identify affected parts precisely (P/N 50-430177-3 and P/N 50-430018-9).","Possibility of life-limit revision based on manufacturer testing introduces regulatory uncertainty and administrative follow-up (Note).","Cross-reference to another AD (AD/Beech 90/70) shifts certain items out of scope of this amendment and requires operators to consult multiple directives (Background)."],"plain_english_summary":"This directive requires Beechcraft F90 operators and maintenance organisations to retire certain cabin pressurisation-related components and the pressurised cabin after fixed numbers of pressurised flight cycles, imposing mandatory life limits to manage fatigue risk. Owners/operators bear replacement and repair costs and must track pressurised cycles precisely to remain compliant.\n\nThe numerical lives may be revised after further manufacturer testing, and prior retirement rules for cabin/cockpit side windows have been removed and are covered by a separate AD."}},"importantCases":[],"_links":{"self":"/api/acts/ad-beech-90-57-amdt-4-fuselage-fatigue-life-limitations","history":"/api/acts/ad-beech-90-57-amdt-4-fuselage-fatigue-life-limitations/history","analysis":"/api/acts/ad-beech-90-57-amdt-4-fuselage-fatigue-life-limitations/analysis","conflicts":"/api/acts/ad-beech-90-57-amdt-4-fuselage-fatigue-life-limitations/conflicts","importantCases":"/api/acts/ad-beech-90-57-amdt-4-fuselage-fatigue-life-limitations/important-cases","documents":"/api/acts/ad-beech-90-57-amdt-4-fuselage-fatigue-life-limitations/documents"}}