{"id":"F2006B09900","name":"AD/F50/70 - LH Elevator Drainage","slug":"ad-f50-70-lh-elevator-drainage","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55076,"registerId":"commonwealth-F2006B09900-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/70 - LH Elevator Drainage","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Fokker F50 (F27 Mk 50) Series Aeroplanes\n\n \n\nAD/F50/70 LH Elevator Drainage 7/96\n\nApplicability: F27 Mk 050 S/N 20103 to 20188.\n\n \n\nRequirement: Action in accordance with Fokker SB F50-55-006.\n\n \n\nNote: RLD AD 1996-033(A) refers.\n\n \n\nCompliance: Within 500 hours time in service after 20 June 1996, or prior to 31 December 1996 whichever occurs first.\n\n \n\nBackground:  When the aircraft is parked the elevator bungee unit causes the elevators to deflect to elevator nose up. This may lead to water being trapped aft of the LH elevator rear spar (up to two litres has been reported). Freezing of the trapped water may lead to elevator instability which may in turn result in elevator and/or aircraft damage.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","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 technical defect in a defined aircraft population. It has not expanded beyond its original purpose of mandating drainage modifications to prevent elevator damage."},"complexity_factors":["Single, specific applicability (one aircraft type, defined serial number range)","Single requirement referencing an external technical document (Fokker SB F50-55-006)","Simple compliance deadline (whichever-occurs-first logic with two fixed dates/hours)","No defined terms section","No cross-references to other legislation or regulations beyond a note about a related Dutch directive","Straightforward background explanation with clear causal chain (water trapping → freezing → instability → damage)"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for specific Fokker F50 aircraft.\n\n**What it does:**\nOrders owners/operators of certain Fokker F50 planes (serial numbers 20103 to 20188) to follow a specific maintenance procedure outlined in Fokker Service Bulletin F50-55-006. This procedure addresses a drainage problem with the left-hand (LH) elevator.\n\n**The safety problem:**\nWhen these aircraft are parked, a component called the \"elevator bungee unit\" causes the elevators (the movable parts on the tail that control up/down movement) to tilt upward. This creates a pocket where water can collect behind the left elevator's rear spar — up to 2 litres has been found. If this water freezes, it can cause the elevator to become unstable, potentially damaging the elevator or the aircraft itself.\n\n**Who must act:**\nOperators of Fokker F50 aircraft with serial numbers between 20103 and 20188.\n\n**When they must act:**\nWithin 500 flight hours after 20 June 1996, or before 31 December 1996 — whichever comes first.\n\n**Why it matters:**\nThis prevents ice formation that could compromise aircraft control surfaces, avoiding potential structural damage and ensuring flight safety."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text provides an initial airworthiness directive narrowly targeting left-hand elevator drainage on F27 Mk 050 aeroplanes serial numbers 20103–20188 and prescribes compliance with a specific Fokker service bulletin within a stated time window (Applicability; Requirement; Compliance). The document itself does not indicate any change to the scope from a prior instrument or an expansion beyond those specified serial numbers, so there is no evidence in this text that the scope has been changed."},"complexity_factors":["Narrow applicability to a defined serial-number range (Applicability).","Mandatory action is defined by reference to an external document (Fokker SB F50-55-006), requiring operators to obtain and follow that bulletin (Requirement).","Compliance deadline is conditional: whichever occurs first of a fixed hours-in-service window or a calendar date (Compliance).","Safety rationale ties a specific mechanical cause (bungee-induced nose-up posture and trapped water) to the hazard, requiring technical remediation (Background).","Cross-reference to another authority's AD (RLD AD 1996-033(A)) introduces an external coordination point (Note)."],"plain_english_summary":"Operators of Fokker F50 (F27 Mk 050) aeroplanes S/N 20103–20188 must carry out the work described in Fokker Service Bulletin F50-55-006 within 500 flight hours after 20 June 1996 or before 31 December 1996, whichever comes first.  \n\nThe action aims to prevent water trapping aft of the left elevator spar — which can freeze, destabilise the elevator and risk damage — and places compliance scheduling and costs on the aircraft operator."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-70-lh-elevator-drainage","history":"/api/acts/ad-f50-70-lh-elevator-drainage/history","analysis":"/api/acts/ad-f50-70-lh-elevator-drainage/analysis","conflicts":"/api/acts/ad-f50-70-lh-elevator-drainage/conflicts","importantCases":"/api/acts/ad-f50-70-lh-elevator-drainage/important-cases","documents":"/api/acts/ad-f50-70-lh-elevator-drainage/documents"}}