{"id":"F2006B09172","name":"AD/DHC-8/17 - Flap Ballscrews","slug":"ad-dhc-8-17-flap-ballscrews","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52919,"registerId":"commonwealth-F2006B09172-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-8/17 - Flap Ballscrews","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)  Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes\n\n \n\nAD/DHC-8/17 Flap Ballscrews  12/91 DM\n\n \n\nApplicability: All model DHC-8 aircraft with serial numbers 3 through 216.\n\n \n\nRequirement: Action in accordance with the technical requirements of Transport Canada AD CF- 91-34.\n\n \n\nCompliance: Within 50 hours time in service after 4 November 1991.\n\n \n\nBackground: It has been found from recent test programs carried out on DHC-8 aircraft at de Havilland that the flap loads may not be evenly distributed into the flap ballscrews. This condition, if not corrected could lead to accelerated wear, reduced fatigue life and possible overloading of the flap structure which could ultimately result in an asymetric flap condition.\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, time-bound safety directive addressing a specific mechanical defect in specific aircraft. It has not expanded beyond its original purpose of mandating flap ballscrew inspections and repairs."},"complexity_factors":["Single, specific mechanical issue addressed","No defined terms section — uses plain technical language","No nested exceptions or conditional logic","Single cross-reference to external Canadian directive (CF-91-34)","Clear, fixed compliance deadline (50 hours after specific date)","Narrow applicability (specific aircraft serial numbers only)","Total length: approximately 200 words"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners and operators of certain Bombardier DHC-8 aircraft (also known as Dash 8s) to inspect and fix a problem with the **flap ballscrews** — mechanical components that help extend and retract the wing flaps during takeoff and landing.\n\n**The problem:**\nTesting found that the flaps' load wasn't being distributed evenly across these ballscrews. If left unfixed, this could cause:\n- Faster wear and tear\n- Reduced lifespan of parts\n- Possible structural overload\n- **Worst case:** Asymmetric flaps (one wing's flaps extending differently from the other), which could make the plane hard or impossible to control\n\n**Who must act:**\nAnyone operating DHC-8 aircraft with serial numbers 3 through 216 — that's most early-model Dash 8s.\n\n**What they must do:**\nFollow the technical instructions in a Canadian safety directive (Transport Canada AD CF-91-34) within 50 flight hours after 4 November 1991.\n\n**Why it matters:**\nThis prevents potential catastrophic loss of control during critical flight phases (takeoff and landing). Airworthiness directives are legally binding — ignoring them grounds the aircraft."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"No change of scope indicated. The directive applies to all DHC‑8 aircraft with serial numbers 3–216 and requires action per Transport Canada AD CF‑91‑34 within 50 hours TIS after 4 Nov 1991 to address uneven flap ballscrew loads and associated structural fatigue risks (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Narrow, concrete applicability: limited to DHC‑8 serial numbers 3–216 (Applicability).","External normative reference: mandates compliance with Transport Canada AD CF‑91‑34 rather than reproducing technical steps (Requirement).","Short mandatory compliance window: corrective action due within 50 hours TIS after 4 Nov 1991, creating scheduling pressure for operators (Compliance).","Safety risk link: requirement founded on test findings of uneven flap load distribution leading to wear, reduced fatigue life and possible asymmetric flaps (Background).","Operational burden on operators: obligation to perform specified maintenance/inspection work within a tight timeframe—costs, downtime borne by operators (Requirement, Compliance).","Limited administrative discretion: directive states mandatory action and a fixed compliance period, leaving little room for alternative measures (Requirement, Compliance).","Dependency risk: enforcement and technical detail rely on the referenced Transport Canada AD; absence of reproduced procedures in this instrument increases reliance on the external document (Requirement)."],"plain_english_summary":"This airworthiness directive requires operators of Bombardier (de Havilland) DHC‑8 aircraft serial numbers 3–216 to carry out the corrective work set out in Transport Canada AD CF‑91‑34 so flap ballscrews share loads correctly. The work must be completed within 50 hours time‑in‑service after 4 November 1991 because tests found uneven load distribution can accelerate wear, reduce fatigue life and may lead to asymmetric flaps."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-17-flap-ballscrews","history":"/api/acts/ad-dhc-8-17-flap-ballscrews/history","analysis":"/api/acts/ad-dhc-8-17-flap-ballscrews/analysis","conflicts":"/api/acts/ad-dhc-8-17-flap-ballscrews/conflicts","importantCases":"/api/acts/ad-dhc-8-17-flap-ballscrews/important-cases","documents":"/api/acts/ad-dhc-8-17-flap-ballscrews/documents"}}