{"id":"F2006B02151","name":"AD/AC/90 - Wing Station 39 Wing Ribs","slug":"ad-ac-90-wing-station-39-wing-ribs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41381,"registerId":"commonwealth-F2006B02151-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC/90 - Wing Station 39 Wing Ribs","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)  \nTwin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes\n\nAD/AC/90 Wing Station 39 Wing Ribs 5/95\n\nApplicability: Models 690, 690A, and 690B S/n 11001 to 11566 and Model 685 S/n 12001 to\n\n12066.\n\nRequirement: Modify the wing ribs at WS 39 in accordance with Twin Commander Service Bulletin 211 Rev 1 Part II.\n\nCompliance: Within 50 hours’ time in service after 25 May 1995, or at the next inspection for Maintenance Release issue after 25 May 1995, whichever occurs first.\n\nBackground: This Directive is issued to prevent an under-strength condition developing in the wing ribs at WS 39, and is part of the requirements of FAA AD 94-04-12.\n\nThis Directive will be amended to include the spar cap and stringer inspections of FAA AD 94-04-12, if subsequent information is received indicating that this is necessary.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific structural defect in specific aircraft. It has not expanded beyond its original purpose; in fact, it explicitly notes it may be expanded in future to match the full US FAA directive, indicating it is currently narrower than the original US safety action."},"complexity_factors":["Single, specific technical requirement (one modification to one structural component)","Limited applicability (only 4 specific aircraft models with defined serial number ranges)","Simple compliance deadline (whichever comes first of two clear triggers)","No defined terms section or complex interpretive provisions","No cross-references to other legislation beyond a single FAA AD reference for background","Short document (approximately 150 words of substantive content)"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it as a \"recall notice\" for aircraft, but legally binding.\n\n**What it does:** It requires owners and operators of specific Twin Commander aircraft models to modify the wing ribs at \"Wing Station 39\" (a specific structural location on the wing). The modification must follow the manufacturer's Service Bulletin 211, Revision 1, Part II.\n\n**Who it affects:** \n- **Aircraft models:** Twin Commander 690, 690A, 690B (serial numbers 11001–11566) and Model 685 (serial numbers 12001–12066)\n- **People affected:** Aircraft owners, operators, and maintenance engineers responsible for these planes\n\n**Why it matters:** The wing ribs at this location could develop an \"under-strength condition\" — meaning they might not be strong enough to handle flight stresses, potentially leading to structural failure. This directive prevents that safety risk.\n\n**When it must be done:** Within 50 flight hours after 25 May 1995, or at the next scheduled inspection for issuing a Maintenance Release (a certificate showing the aircraft is safe to fly) — whichever comes first.\n\n**Background note:** This aligns with a US Federal Aviation Administration (FAA) safety order (AD 94-04-12). CASA notes they may expand this directive later to include additional inspections of spar caps and stringers (other wing structural parts) if needed."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive, as written, requires modification of wing ribs at WS 39 for the listed aircraft (Requirement; Applicability) and does not yet include the spar cap and stringer inspections from FAA AD 94-04-12. The text explicitly states it may be amended to add those inspections if subsequent information indicates it is necessary (Background). As of the text provided, the scope has not been expanded beyond the WS 39 rib modification."},"complexity_factors":["Narrow applicability limited to specific models and serial-number ranges (Applicability)","Single, well-specified technical action tied to a manufacturer service bulletin (Requirement)","Short, explicit compliance window with an alternative timing trigger (50 hours or next Maintenance Release) (Compliance)","Dependency on an external document (Twin Commander Service Bulletin 211 Rev 1 Part II) for technical detail (Requirement)","Potential future amendment to add further inspections (spar cap and stringer) based on new information (Background)"],"plain_english_summary":"This directive requires owners/operators of certain Twin Commander 690/690A/690B (s/n 11001–11566) and 685 (s/n 12001–12066) to modify the wing ribs at Wing Station 39 per Twin Commander Service Bulletin 211 Rev 1 Part II, within 50 flight hours after 25 May 1995 or at the next Maintenance Release, whichever comes first.\n\nIt’s intended to prevent an under‑strength rib condition; costs, downtime and technical execution fall to operators and their maintenance providers, and the authority may amend the directive later (possible additional inspections)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-90-wing-station-39-wing-ribs","history":"/api/acts/ad-ac-90-wing-station-39-wing-ribs/history","analysis":"/api/acts/ad-ac-90-wing-station-39-wing-ribs/analysis","conflicts":"/api/acts/ad-ac-90-wing-station-39-wing-ribs/conflicts","importantCases":"/api/acts/ad-ac-90-wing-station-39-wing-ribs/important-cases","documents":"/api/acts/ad-ac-90-wing-station-39-wing-ribs/documents"}}