{"id":"F2006B09860","name":"AD/F50/33 Amdt 1 - Landing Gear - Extension/Retraction Control","slug":"ad-f50-33-amdt-1-landing-gear-extension-retraction-control","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54947,"registerId":"commonwealth-F2006B09860-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/33 Amdt 1 - Landing Gear - Extension/Retraction Control","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/F50/33\n\nAmdt 1\n\n  \nLanding Gear \\- Extension/Retraction Control 7/92\n\nApplicability: F27 Mk 050 aircraft Serial Numbers 20103 to 20197 inclusive.\n\nRequirement: 1. Connect the DOWN solenoid of the landing gear selector valve to the EMERGENCY DC bus No 2 instead of DC bus No 2 as outlined in Fokker Service Bulletin F50-32-013 dated 16 October 1989, or\n\nNote: AD/F50/33 covers Requirement 2 of the RLD Airworthiness Directive, Flight Manual amendment A/ANF 2750/10 has been issued to cover Requirement 1 of the RLD Airworthiness Directive.\n\n2. Replace the Landing Gear Selector Valve P/N 114044002 with a modified Valve P/N 114044003 as outlined in Fokker Service Bulletin F50-32-016 dated 23 December 1991. Compliance with SB F50-32-016 and removal of the Flight Manual amendment A/ANF 2750/10 is an alternative means of compliance with this AD.\n\nNote: RLD Airworthiness Directive BLA 89-138 Issue 3 refers.\n\nCompliance: The Compliance of the original issue of this Directive was prior to 15 March 1990.\n\nThis amendment is effective from 25 June 1992.\n\nBackground: Fokker have found that an inadvertent UP selection of the landing gear selector valve is possible as a result of a leaking pilot valve at the moment the DOWN solenoid is de-energised. The original issue of this Directive required modification to the system wiring to prevent such an occurrence.\n\nAmendment 1 is issued to advise of an alternative method of compliance and increases the serial number range of aircraft affected.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original directive (issued prior to March 1990) required only the electrical rewiring modification. Amendment 1 (June 1992) expanded the scope in two ways: (1) it increased the serial number range of affected aircraft (originally narrower, now 20103-20197), and (2) it added an entirely alternative compliance method (valve replacement) rather than mandating only the wiring change. This transformed the directive from a single-mandate to a flexible compliance framework."},"complexity_factors":["Single technical subject matter (landing gear wiring/valve only)","Only 2 defined compliance paths with clear alternatives","Minimal cross-referencing (only to specific Fokker Service Bulletins and one Dutch RLD directive)","No nested conditional logic or exceptions to exceptions","Short document (approximately 200 words)","Specific, unambiguous applicability (serial number range clearly stated)","Technical terminology is aircraft-specific but used precisely without requiring extensive legal interpretation"],"plain_english_summary":"This CASA safety directive requires owners/operators of Fokker F50 serials 20103–20197 to correct a landing‑gear defect that can allow the gear to retract when the \"DOWN\" solenoid loses power (due to a leaking pilot valve).  \n\nCompliance may be achieved by rewiring the DOWN solenoid to the emergency DC bus or by fitting a modified selector valve per Fokker service bulletins. The measure prevents accidental gear retraction and associated runway or control accidents."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 1 expands the directive's scope by increasing the affected serial-number range to S/N 20103–20197 and by adding an alternative method of compliance: replacing selector valve P/N 114044002 with modified P/N 114044003 per Fokker SB F50-32-016 (which can substitute for the earlier wiring change and allow removal of Flight Manual amendment A/ANF 2750/10). The amendment is effective 25 June 1992; the original directive required compliance prior to 15 March 1990."},"complexity_factors":["Technical nature: involves aircraft electrical wiring (DC bus refeed) and hydraulic/control valve replacement, requiring qualified maintenance personnel and access to parts.","Alternative compliance routes: operators may choose either a wiring change (SB F50-32-013) or a valve P/N replacement (SB F50-32-016), increasing decision and verification complexity.","Cross-references: relies on multiple external documents (two Fokker Service Bulletins, RLD Airworthiness Directive BLA 89-138 Issue 3, and a Flight Manual amendment A/ANF 2750/10) which creates coordination and document-control burden.","Serial-number scope: amendment expands the affected SN range (now 20103–20197), requiring operators to review fleet applicability.","Compliance history/dates: original compliance was required prior to 15 March 1990, while the amendment is effective 25 June 1992, creating potential record-keeping/retrospective compliance issues.","Operational verification: one compliance route involves removal of a Flight Manual amendment as evidence, which requires procedural as well as physical changes.","Supply/parts risk: valve replacement depends on availability of modified P/N 114044003, creating potential procurement or downtime costs for operators."],"plain_english_summary":"This Airworthiness Directive requires Fokker F27 Mk 50 (F50) operators to either rewire the landing‑gear DOWN solenoid to the emergency DC bus or replace the landing‑gear selector valve with a modified part. It applies to aircraft serial numbers 20103–20197 and is effective 25 June 1992.\n\nThe stated purpose is to prevent an inadvertent UP selection caused by a leaking pilot valve when the DOWN solenoid is de‑energised. Operators pay for and implement the corrective wiring or part change by following the cited Fokker Service Bulletins."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-33-amdt-1-landing-gear-extension-retraction-control","history":"/api/acts/ad-f50-33-amdt-1-landing-gear-extension-retraction-control/history","analysis":"/api/acts/ad-f50-33-amdt-1-landing-gear-extension-retraction-control/analysis","conflicts":"/api/acts/ad-f50-33-amdt-1-landing-gear-extension-retraction-control/conflicts","importantCases":"/api/acts/ad-f50-33-amdt-1-landing-gear-extension-retraction-control/important-cases","documents":"/api/acts/ad-f50-33-amdt-1-landing-gear-extension-retraction-control/documents"}}