{"id":"F2006L03618","name":"AD/F50/96 Amdt 1 - Bottom Skin Chine Line","slug":"ad-f50-96-amdt-1-bottom-skin-chine-line","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":137308,"registerId":"commonwealth-F2006L03618-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Fokker F50 (F27 Mk 50) Series Aeroplanes","sectionType":"division","heading":"Fokker F50 (F27 Mk 50) Series Aeroplanes","content":"### Fokker F50 (F27 Mk 50) Series Aeroplanes\n\n| AD/F50/96 Amdt 1 | Bottom Skin Chine Line | 12/2006 |\n| ---------------- | ---------------------- | ------- |\n\n| Applicability: | Model F27 Mark 050 aircraft, serial numbers 20103 through 20172. |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement: | 1. Visually inspect the Fuselage Bottom Skin Chine Line between Fuselage Station (STA) 6675 and STA 15375 in accordance with Part 3, Steps A and B of the Accomplishment Instructions of Fokker Services Service BulletinSBF50-53-058, dated 30 June 2006, or later EASA approved revision.a. When cracks are found appearing through the paint layer, proceed in accordance with the instructions in SBF50-53-058 and within the following time limits:If the crack length is more than 50 mm, before further flight, remove the paint in accordance with AMM Chapter 51-24-00 and reinspect.If the crack length is between 10 and 50 mm, within 50 flight cycles, remove the paint in accordance with AMM Chapter 51-24-00, and reinspect.If the crack length is less than 10 mm, within 1,000 flight cycles, eddy-current inspect in accordance with Fokker SBF50-53-059. dated24 August 2006, or later EASA approved revision.b. When cracks are found after the removal of paint as instructed by Requirement 1.a., proceed in accordance with the instructions inSBF50-53-058, and within the following time limits:If the crack length is more than 100 mm, before further flight, repair in accordance with SRM Chapter 53-00-02 Repair No. 10.If the crack length is between 50 mm and 100 mm, within 50 flight cycles, repair in accordance with SRM Chapter 53-00-02 Repair No. 10.If the crack length is between 10 mm and 50 mm, repeat the visual inspection in accordance with SBF50-53-058 within 100 flight cycles after the initial inspection, and thereafter at intervals not to exceed 100 flight cycles; until accomplishment of SBF50-53-059.If the crack length is less than 10 mm, within 1,000 flight cycles, eddy-current inspect in accordance with Fokker SBF50-53-059. |\n| | 2. Visually inspect the Fuselage Bottom Skin Chine Line between STA 1320 and STA 3100, in accordance with Part 3, Steps C and D of the Accomplishment Instructions of SBF50-53-058, dated 30 June 2006, or later EASA approved revision.When cracks are found appearing through the paint layer, proceed in accordance with the instructions in SBF50-53-058 and within the time limits provided in Requirement 1.a.When cracks are found after the removal of paint, proceed in accordance with the instructions in SBF50-53-058 and within the time limits provided in Requirement 1.b.3. In all cases, whether or not cracks were found and repaired in accordance with Requirements 1 and 2 of this Directive, eddy-current inspect the Fuselage Bottom Skin Chine Line (between the same fuselage stations as covered by the visual inspection) in accordance with Part 3, Accomplishment Instructions ofSBF50-53-059 dated 24 August 2006, or later EASA approved revision.When cracks are found during the eddy-current inspection, proceed in accordance with the instructions in SBF50-53-059 and the following time limits:If the crack length is more than 100 mm, before further flight, repair in accordance with SRM Chapter 53-00-02 Repair No. 10.If the crack length is between 50 mm and 100 mm, within 50 flight cycles, repair in accordance with SRM Chapter 53-00-02 Repair No. 10.If the crack length is less than 50 mm, within 100 flight cycles after the initial inspection, accomplish the eddy-current inspection in accordance with SBF50-53-059, and repeat thereafter at intervals not to exceed 100 flight cycles; until the repair is accomplished.When cracks are found as a result of the inspection requirements of this Directive, within 7 days after the inspection, report all findings to Fokker Services B.V.Note: CAA-NL AD NL-2006-009 R1 refers. |\n| Compliance: | 1. Upon accumulating 20,000 total flight cycles or within 3 weeks after31 August 2006, whichever occurs later.2. Upon accumulating 45,000 total flight cycles or with 3 weeks after31 August 2006, whichever occurs later.3. Within 1,000 flight cycles after the visual inspection in accordance withSBF50-53-058. |\n\n| | The compliance times for Requirements 1 and 2 remain unchanged by this issue of this Directive. |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| | This Amendment becomes effective on 23 November 2006. |\n| Background: | The inspection procedure as described by Fokker 50 Non-Destructive Testing Manual (NDTM), Part 6, Chapter 53-30-02, which is referenced by Fokker 50 Maintenance Review Board (MRB) Tasks 530000-00-04 and 530000-00-08 does not show the correct inspection areas. In addition to the existing procedure, the area at the kink in the bottom fuselage skin, the actual chine line, must be inspected. Investigation revealed that a number of aircraft have already passed the relevant inspection thresholds by a considerable margin. As a result, it may be possible that cracks have developed and remained undetected. This condition, if not corrected, could result in failure of the fuselage bottom skin.Amendment 1 is issued in response a revision of the related CAA-NL AD, which introduces additional eddy-current inspections. |\n\n![](image.001.png) \nDavid Villiers \nDelegate of the Civil Aviation Safety Authority\n\n12 October 2006","sortOrder":0},{"sectionNumber":"AD/F50/96 Amdt 1","sectionType":"part","heading":"AD/F50/96 Amdt 1","content":"## AD/F50/96 Amdt 1","sortOrder":1},{"sectionNumber":"Bottom Skin Chine Line","sectionType":"part","heading":"Bottom Skin Chine Line","content":"## Bottom Skin Chine Line","sortOrder":2},{"sectionNumber":"12/2006","sectionType":"part","heading":"12/2006","content":"## 12/2006","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":false,"description":"This is an amendment to an existing Airworthiness Directive (AD/F50/96). While it introduces additional eddy-current inspection requirements compared to the original directive, this expansion is consistent with the original purpose of ensuring structural integrity of the fuselage bottom skin. The amendment responds to updated information from the Dutch aviation authority (CAA-NL) and does not represent scope creep beyond the aircraft safety mandate."},"complexity_factors":["Multiple nested conditional requirements based on crack length (four distinct thresholds: <10mm, 10-50mm, 50-100mm, >100mm)","Cross-references to four external technical documents (SBF50-53-058, SBF50-53-059, AMM Chapter 51-24-00, SRM Chapter 53-00-02 Repair No. 10)","Dual inspection methodologies required (visual inspection plus eddy-current inspection)","Multiple compliance deadlines tied to different flight cycle accumulations (20,000 vs 45,000 total cycles) and calendar dates","Geographic specificity requiring inspection between defined Fuselage Stations (STA 6675-15375 and STA 1320-3100)","Amendment structure requiring readers to understand what changed from previous version versus what remained unchanged","Reporting requirement to external entity (Fokker Services B.V.) within 7 days of findings"],"plain_english_summary":"This AD requires operators of Fokker F50 aircraft (S/N 20103–20172, about 70 machines) to inspect the fuselage bottom skin chine line—using visual and eddy‑current methods—and to repair any cracks. Repairs or monitoring must follow deadlines tied to crack size to prevent further flight with significant damage.\n\nIt closes a gap missed in maintenance instructions after aircraft flew past inspection windows; undetected cracks in this area could lead to fuselage failure, so immediate checks are mandated."},"flash_summary":{"complexity_score":7,"scope_assessment":{"changed":true,"description":"Amendment 1 expands the inspection scope by explicitly adding the chine line area and introducing additional eddy‑current inspections (per Background and Requirement 3). It preserves the original compliance times for Requirements 1 and 2 but imposes new inspection methods, reporting obligations and size‑based repair deadlines, thereby broadening the practical burden on affected operators compared with the prior NDT/MRB procedures."},"complexity_factors":["Multiple inspection methods required: visual inspection, paint removal, and eddy‑current testing (Requirements 1–3).","Tiered, size-based compliance actions with different deadlines (crack length bands: <10 mm, 10–50 mm, 50–100 mm, >100 mm).","Distinct fuselage station ranges with separate procedures (STA 6675–15375 and STA 1320–3100).","Mixed timing metrics: flight cycles, fixed calendar dates, and short-term windows (e.g. within 7 days for reporting).","Cross-references to external documents and manuals (Fokker SBF50-53-058, SBF50-53-059, AMM Chapter 51-24-00, SRM Chapter 53-00-02) creating dependency on later EASA-approved revisions.","Applicability confined to a serial-number subset (20103–20172), requiring operator-level fleet tracking.","Interaction with prior AD and CAA‑NL requirements; Amendment 1 adds inspections while preserving some original compliance times."],"plain_english_summary":"This amendment requires operators of Fokker F50 aircraft (serials 20103–20172) to carry out targeted visual and eddy‑current inspections of the fuselage bottom skin chine line, remove paint where indicated, repair cracks according to size-based deadlines, and report findings to the manufacturer. It updates inspection areas missed by prior guidance. Operators pay for inspections, paint removal and any repairs, must schedule work by specified flight‑cycle or calendar deadlines, and may be grounded until repairs are completed."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-96-amdt-1-bottom-skin-chine-line","history":"/api/acts/ad-f50-96-amdt-1-bottom-skin-chine-line/history","analysis":"/api/acts/ad-f50-96-amdt-1-bottom-skin-chine-line/analysis","conflicts":"/api/acts/ad-f50-96-amdt-1-bottom-skin-chine-line/conflicts","importantCases":"/api/acts/ad-f50-96-amdt-1-bottom-skin-chine-line/important-cases","documents":"/api/acts/ad-f50-96-amdt-1-bottom-skin-chine-line/documents"}}