{"id":"F2006B09820","name":"AD/F28/85 - Liftdumper Microswitches","slug":"ad-f28-85-liftdumper-microswitches","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54762,"registerId":"commonwealth-F2006B09820-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.","sortOrder":0},{"sectionNumber":"AD/F28/85 Liftdumper Microswitches 9/200","sectionType":"part","heading":"AD/F28/85 Liftdumper Microswitches 9/2000 DM","content":"# AD/F28/85 Liftdumper Microswitches 9/2000 DM\n\nApplicability: All Model F.28 Mk 1000, 2000, 3000, 4000 series aeroplanes.\n\nRequirement: 1. If not previously accomplished, visually inspect and functionally check the liftdumper microswitches installed in the pedestal in accordance with Part 2 of the Accomplishment Instructions of Fokker Service Bulletin (SB) F28/27-186 dated 8 May 2000.\n\n2. If, as a result of the Requirement 1 inspection, the position of the centreline of the microswitch activating roller is found to be 2mm ±0.5mm before the end of the cam, the aircraft may be returned to service. However, if the position of the centreline of the microswitch activating roller is found to be less than 1.5mm before the end of the cam, re-rig the cam in accordance with Part 2.A(5) of the Accomplishment Instructions of Fokker SB F28/27-186.\n\nNote: RLD AD 2000-073 (A) refers.\n\nCompliance: For Requirement 1 \\- Before 19 September 2000.\n\nFor Requirement 2 \\- Before further flight.\n\nThis Airworthiness Directive becomes effective on 19 July 2000.\n\nBackground: The Netherlands Rijksluchtvaartdienst has received two reports of inadvertent liftdumper deployment in F28 series aeroplanes during the take-off roll. Investigation revealed that with the throttle leavers in full forward position and the liftdumper system armed, the rollers of both 75% liftdumper microswitches ran off the end of the cam.\n\nThis condition, if not corrected, could result in occurrences of inadvertent liftdumper deployment during take-off. This Directive requires a once only inspection of the liftdumper microswitches and, if necessary, re-rigging of the microswitches.\n\n![](image.003.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 13 July 2000\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 19 July 2000.","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope. It addresses a specific unsafe condition in a specific aircraft type with targeted inspection and remediation requirements. There is no evidence of scope creep or expansion beyond the original safety purpose."},"complexity_factors":["Single, specific aircraft type (Fokker F.28 series) with clear model numbers","Only two requirements: one inspection and one conditional re-rigging action","Simple conditional logic (if position < 1.5mm then re-rig; if 2mm ±0.5mm then OK)","Clear compliance dates (before 19 September 2000 for inspection; before further flight for any required re-rigging)","References only one external technical document (Fokker Service Bulletin F28/27-186)","No nested exceptions or complex cross-referencing to other legislation","Straightforward background explaining the safety risk in plain language"],"plain_english_summary":"This CASA Airworthiness Directive mandates a one‑time inspection and functional test of the liftdumper microswitches in Fokker F.28 cockpits after two incidents where they caused unintended lift‑dumper deployment during take‑off. It affects operators, airlines and maintenance organisations flying F.28 series aircraft in Australia and carries a hard compliance deadline (19 Sep 2000); aircraft with an out‑of‑tolerance switch must be grounded until corrected."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive implements a narrowly focused safety remedy for a specific mechanical condition (inadvertent liftdumper deployment) on particular Fokker F.28 models. It requires a one‑time inspection and corrective re‑rigging if measurements fall outside the stated tolerance. This remains within the original safety‑remediation purpose described in the Background and has not broadened the scope beyond that technical objective."},"complexity_factors":["Narrow scope: single aircraft family (F.28 Mk 1000–4000)","Two-step requirement structure (inspect; then possibly re-rig)","Dependence on external document: Fokker Service Bulletin F28/27-186 (Part 2 and Part 2.A(5))","Precise measurement tolerances (2 mm ±0.5 mm; action if < 1.5 mm)","Time-limited compliance windows (one before-set date and one 'before further flight')","Cross-reference to another authority’s AD (RLD AD 2000-073 (A))","Technical subject-matter requiring skilled maintenance personnel"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- **Applicability:** It applies to all Fokker F.28 Mk 1000, 2000, 3000 and 4000 series aeroplanes (the affected fleet). (See “Applicability”.)\n\n- **Required actions:**\n  - **Requirement 1:** If it has not already been done, operators must visually inspect and functionally check the liftdumper microswitches in the pedestal according to Part 2 of the Accomplishment Instructions in Fokker Service Bulletin F28/27-186 dated 8 May 2000.\n  - **Requirement 2:** If the inspection shows the centreline of the microswitch activating roller is 2 mm ± 0.5 mm before the end of the cam, no further action is required and the aircraft may return to service. If the centreline is less than 1.5 mm before the end of the cam, the cam must be re‑rigged following Part 2.A(5) of the same Service Bulletin.\n\n- **Timing (Compliance):**\n  - The inspection in Requirement 1 had to be completed before 19 September 2000. \n  - Any corrective re‑rigging required by Requirement 2 must be done before the aircraft’s next flight (i.e. before further flight).\n\n- **Effective date:** The Directive became effective on 19 July 2000.\n\n**Why it was issued (official rationale)**\n\n- The Netherlands civil aviation authority reported two incidents in which the liftdumper deployed unintentionally during the take‑off roll. Investigation found that, with throttles fully forward and the liftdumper armed, the rollers of the 75% liftdumper microswitches could run off the end of the cam. The Directive’s stated purpose is to correct that unsafe condition by requiring a one‑time inspection and re‑rigging if needed.\n\n**Who is affected and who pays**\n\n- **Affected parties:** Aircraft operators/owners of the listed F28 models, and maintenance organisations that service them.\n- **Who pays:** The operator pays for the inspection and any re‑rigging (labour, any minor parts if required), and for aircraft downtime while maintenance is performed.\n\n**How this changes behaviour and decision rights**\n\n- Operators must prioritise and schedule a one‑time technical inspection for each affected aircraft and perform corrective rigging where the measurement threshold is breached. Maintenance technicians must make an accurate measurement of the microswitch roller position against the cam and follow the manufacturer's Service Bulletin if adjustment is needed.\n\n**Implementation, compliance burden and risks**\n\n- **Implementation relies on an external document:** The AD mandates following specific parts of Fokker Service Bulletin F28/27‑186 (an external, manufacturer document). \n- **Technical precision required:** Compliance depends on a narrow measurement tolerance (2 mm ± 0.5 mm; corrective action if < 1.5 mm). That requires competent maintenance personnel and suitable access/fixturing to measure and re‑rig the mechanism.\n- **Operational impact:** Where re‑rigging is needed, the aircraft is grounded until the corrective action is completed (requirement: before further flight). Even where only inspection is needed, scheduling and labour impose modest downtime and cost.\n- **Authority and enforceability:** The CASA delegate issued the AD under the cited regulation; operators are legally required to comply within the stated timeframes.\n\n**Trade‑offs, incentives and economic effects**\n\n- **Concentrated benefits, diffuse costs:** The safety benefit (reduced risk of inadvertent liftdumper deployment) is concentrated on the operator and passengers/crew of each affected aircraft; the cost (inspection and potential re‑rigging, downtime) is borne by operators. \n- **Incentives for prompt action:** The “before further flight” requirement for corrective rigging creates a strong incentive to fix any aircraft found outside tolerance immediately. \n- **Potential for substitution or measurement error:** If measurement techniques vary between maintenance providers, some aircraft might be re‑rigged unnecessarily or some non‑conforming aircraft might be missed. The AD’s reliance on the Service Bulletin centralises the technical procedure but also requires operators to possess or obtain that document and to interpret it correctly.\n\n**Concrete mechanisms, not judgment**\n\n- The Directive legally requires an inspection against defined dimensional criteria and requires re‑rigging where the dimension is less than a specified limit, using the manufacturer’s prescribed method. It creates a binding, time‑limited obligation on aircraft operators for the affected models and references specific steps within a manufacturer service document for implementation (Requirements 1 and 2; Compliance)."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f28-85-liftdumper-microswitches","history":"/api/acts/ad-f28-85-liftdumper-microswitches/history","analysis":"/api/acts/ad-f28-85-liftdumper-microswitches/analysis","conflicts":"/api/acts/ad-f28-85-liftdumper-microswitches/conflicts","importantCases":"/api/acts/ad-f28-85-liftdumper-microswitches/important-cases","documents":"/api/acts/ad-f28-85-liftdumper-microswitches/documents"}}