{"id":"F2006B09908","name":"AD/F50/78 Amdt 1 - Outer Wing Stringer-to-Rib Connections","slug":"ad-f50-78-amdt-1-outer-wing-stringer-to-rib-connections","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55100,"registerId":"commonwealth-F2006B09908-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/78 Amdt 1 - Outer Wing Stringer-to-Rib Connections","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 F50 (F27 Mk 50) Series Aeroplanes\n\nAD/F50/78\n\nAmdt 1\n\n  \nOuter Wing Stringer-to-Rib Connections 3/99\n\nApplicability: Model F.27 Mk.050 and 0502 aircraft with serial numbers 20103 through 20298\\. Requirement: Inspect and modify in accordance with RLD AD 1998-023/2.\n\nNote: Fokker Service Bulletin F50-57-019 refers.\n\nCompliance: At the inspection threshold and modification times specified in the Requirement Document.\n\nThis Amendment becomes effective on 25 March 1999.\n\nBackground: On early Model F.27 Mk.050 series aircraft, loose connections between ribs and stringers may still occur as in the case of the Model F.27 series aircraft, which was addressed by AD/F27/139. Such deficient connections reduce the static buckling strength of the wing skin, and may cause fretting of the stringer. This condition, if not corrected, could result in fatigue cracking of the stringer and skin. This Directive requires inspection and modification of the connections between stringers and ribs outboard of Wing STA.10760.\n\nAmendment 1 is issued in response to a revision of the RLD AD which introduces a repeat inspection requirement until the required modification is accomplished.\n\nThe original issue of this Airworthiness Directive became effective on 21 May 1998.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 1 increases the ongoing inspection obligation by introducing repeat inspections until the mandated modification is completed. The original AD required inspection and modification; the amendment adds a continuing inspection cycle (per the revised RLD AD) that expands the duration and frequency of compliance duties for affected operators."},"complexity_factors":["Cross-reference to an external Requirement Document (RLD AD 1998-023/2) and Fokker Service Bulletin F50-57-019 — requires users to consult outside material to determine action and timing.","Introduction of repeat inspection obligation until modification is accomplished — creates ongoing compliance tracking and potential for repeated maintenance events.","Serial-number-limited applicability (20103–20298) — requires fleet-level record checks to determine affected aircraft.","Technical nature of inspections and modifications (structural stringer-to-rib connections) — demands certified maintenance personnel, specialised skills and possible parts or modification works.","Compliance timing specified only by the referenced Requirement Document — affords limited immediate detail in the AD itself, shifting interpretive burden to the Requirement Document.","Operational impact: inspections/modification may cause aircraft downtime and direct costs to operators; scheduling and logistical coordination are required."],"plain_english_summary":"Requires operators of Fokker F.27 Mk.050 and 0502 aircraft (serial numbers 20103–20298) to inspect and modify outer wing stringer-to-rib connections in accordance with RLD AD 1998-023/2; this amendment adds repeat inspections until the required modification is completed. It applies to aircraft operators and maintenance organisations, who bear inspection, repair and scheduling costs. The measure is directed at preventing fretting and fatigue cracking of stringers and wing skin; exact timing and thresholds are set in the referenced Requirement Document."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment stays within the original scope of addressing wing structural integrity. It adds a repeat inspection requirement but does not expand to new aircraft types, new structural areas, or new safety issues. The change is procedural (how often to inspect) rather than a scope expansion."},"complexity_factors":["Single, specific technical requirement (inspect and modify per external document)","Only 2 defined applicability criteria (model numbers and serial number range)","Minimal conditional logic (compliance timing references external document)","No internal cross-references to other sections of legislation","Short length (under 300 words)","Single amendment purpose clearly stated in plain language"],"plain_english_summary":"This safety order requires owners/operators of certain Fokker F.27 Mk.050 and 0502 aeroplanes (serials 20103–20298, ~196 aircraft) to inspect and repair loose stringer-to-rib connections in the outer wings to prevent metal fatigue and potential structural failure. Maintenance engineers must carry out the work.\n\nUnlike the 1998 rule, this 1999 amendment mandates repeated inspections at intervals until the required modification is completed."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-78-amdt-1-outer-wing-stringer-to-rib-connections","history":"/api/acts/ad-f50-78-amdt-1-outer-wing-stringer-to-rib-connections/history","analysis":"/api/acts/ad-f50-78-amdt-1-outer-wing-stringer-to-rib-connections/analysis","conflicts":"/api/acts/ad-f50-78-amdt-1-outer-wing-stringer-to-rib-connections/conflicts","importantCases":"/api/acts/ad-f50-78-amdt-1-outer-wing-stringer-to-rib-connections/important-cases","documents":"/api/acts/ad-f50-78-amdt-1-outer-wing-stringer-to-rib-connections/documents"}}