{"id":"F2006B09904","name":"AD/F50/74 - Ground Idle Stop Assembly","slug":"ad-f50-74-ground-idle-stop-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55088,"registerId":"commonwealth-F2006B09904-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/74 - Ground Idle Stop Assembly","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/F50/74 Ground Idle Stop Assembly 6/97\n\nApplicability: All Fokker F27 Mk 50 aircraft with serial numbers 20103 through 20317, 20321, 20324, 20327, 20329 and 20331.\n\nRequirement : Modify the engine controls by installing a new ground-idle stop assembly and two placards in accordance with the accomplishment instructions of Fokker F50 Service Bulletin F50-76-016 dated December 20, 1996.\n\nNote 1: RLD AD 1996-149(A) dated December 31, 1996, supersedes and cancels RLD AD 1996-128(A) dated October 31, 1996.\n\nNote 2: A flight manual amendment correcting the “available accelerate-stop distance” initially required by RLD AD 1996-128(A) has been retained by RLD AD 1996-148(A) and is available from CASA on request.\n\nCompliance: No later than 22 May 1998.\n\nThis Airworthiness Directive becomes effective on 22 May 1997.\n\nBackground: During flight tests of a Fokker F27 Mk 60 aircraft it was determined that the stop performance with rapid selection of reverse was less than expected. This condition also applies to the F27 Mk 50 aircraft.\n\nThe reduced performance is attributed to the slew-rate limiter that is a feature of the production propeller pitch control unit (PCU). The prototype PCU that was used during initial performance testing did not have the slew-rate limiter incorporated.\n\nThis directive provides a modification to the power levers and a revision to the flight manual to address this situation.","sortOrder":0}],"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":2,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive with a narrow, well-defined scope addressing a specific safety defect in a particular aircraft type. The scope has not expanded beyond its original purpose of correcting a stopping performance issue."},"complexity_factors":["Single, specific technical requirement (install one assembly and two placards)","Clear applicability clause limited to specific aircraft serial numbers","Single compliance date with no conditional exceptions","No defined terms section or complex cross-referencing","Background explanation provided in plain language","Document is essentially a one-page safety bulletin"],"plain_english_summary":"This CASA safety order required operators of specified Fokker F50 (F27 Mk 50) aircraft to fit a ground‑idle stop assembly and cockpit placards to the engine controls. It responds to tests showing a production slew‑rate limiter slowed reverse‑thrust response, making published landing‑stop distances unreliable. Affected aircraft are serials 20103–20317 and several specific later serials; work was due by 22 May 1998."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This AD replaces and cancels an earlier AD (RLD AD 1996‑128(A)) while retaining a previously required flight manual amendment (Notes 1–2). It therefore consolidates and clarifies corrective action (hardware installation plus placards per the service bulletin) for the listed serial numbers and sets a new compliance date, altering the regulatory packaging and status of prior requirements (Requirement; Note 1; Note 2; Compliance)."},"complexity_factors":["Technical modification to engine controls involving the propeller pitch control unit and its slew‑rate limiter (Background; Requirement)","Limited applicability by precise serial numbers requiring fleet checks to identify affected aircraft (Applicability)","Mandatory use of manufacturer Service Bulletin instructions, creating dependency on supplier documentation and possible shop capability differences (Requirement)","Regulatory cross‑references and replacement of earlier ADs, requiring operators to track superseded requirements and retained manual amendments (Note 1; Note 2)","Fixed compliance deadline imposing scheduling and potential operational disruption to affected operators (Compliance)"],"plain_english_summary":"This directive orders operators of specified Fokker F27 Mk 50 aeroplanes (listed serial numbers) to install a new ground‑idle stop assembly and two cockpit placards, following Fokker Service Bulletin F50‑76‑016, to address reduced reverse/stop performance caused by a propeller control unit slew‑rate limiter. (Applicability; Requirement; Background) Operators must comply by 22 May 1998, pay for the modification and placards, and keep a retained flight‑manual amendment available from CASA. (Compliance; Note 2)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-74-ground-idle-stop-assembly","history":"/api/acts/ad-f50-74-ground-idle-stop-assembly/history","analysis":"/api/acts/ad-f50-74-ground-idle-stop-assembly/analysis","conflicts":"/api/acts/ad-f50-74-ground-idle-stop-assembly/conflicts","importantCases":"/api/acts/ad-f50-74-ground-idle-stop-assembly/important-cases","documents":"/api/acts/ad-f50-74-ground-idle-stop-assembly/documents"}}