{"id":"F2006B09804","name":"AD/F28/70 Amdt 1 - Horizontal Stabilizer Actuator Servo Valve Assembly","slug":"ad-f28-70-amdt-1-horizontal-stabilizer-actuator-servo-valve-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54726,"registerId":"commonwealth-F2006B09804-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F28/70 Amdt 1 - Horizontal Stabilizer Actuator Servo Valve 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 F28 Series Aeroplanes\n\nAD/F28/70\n\nAmdt 1\n\n  \nHorizontal Stabilizer Actuator Servo Valve Assembly 5/95\n\nApplicability: 1. All model F28 (except Mk 0100) S/N 11003 thru 11241, 11991 and 11992.\n\n2. All spare Menasco actuators P/No 11100.\n\nRequirement: Unless previously carried out, action in accordance with Fokker Service Bulletin SB F28/27-183.\n\nNote 1: RLD AD 1992-077/2 (A) refers.\n\nNote 2: Fokker SB F28/27-183 refers to Menasco SB 11100-27-105.\n\nCompliance: 1. a. By 01 August 1995 for Part 1 of the Requirement Document.\n\n    b. For Part 2 of the Requirement Document: At next removal of the stabilizer control unit or by 01 January 1998, whichever occurs first.\n\n    2. Prior to installation on an aircraft.\n\nBackground: A crew on an overseas F28 experienced a horizontal stabilizer malfunction where the stabilizer trim slowly ran away. The auto pilot disengaged and the aircraft started to pitch up and climb. Although both pilots held the control column fully forward, the aircraft continued to climb to 31,000 feet. The crew reduced engine power after which the climb stopped and the aircraft started to descend. At the same time the centre of gravity had been moved forward by reseating the passengers. The aircraft diverted and carried out an emergency landing at the nearest airport. This amendment is being raised to mandate actuator modification following advice that a F28 horizontal stabilizer moved to the full nose down position after engine shut-down.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is an amendment (Amdt 1) to an existing Airworthiness Directive, but it remains tightly focused on its original purpose: addressing a specific mechanical defect in the horizontal stabilizer actuator. The amendment adds a second incident to the background and adjusts compliance timing, but does not expand beyond the original safety issue."},"complexity_factors":["Short, single-purpose directive (approximately 250 words)","Only 2 defined applicability categories (aircraft serial numbers and spare parts)","Simple two-part compliance structure with clear deadlines","Minimal cross-referencing (only references to manufacturer service bulletins and one related airworthiness directive)","No nested exceptions or conditional logic beyond standard 'unless previously carried out' clause","Single requirement tied to external technical document (Fokker Service Bulletin)"],"plain_english_summary":"This AD requires inspection and modification of the horizontal stabilizer actuator servo valve assembly on specified Fokker F28 aircraft (certain serials) and on Menasco spare actuators before installation, per Fokker Service Bulletin F28/27-183. Compliance deadlines set short-term and by removal/maintenance actions.\n\nIssued after two incidents of uncommanded stabilizer movement that nearly caused loss of control, the directive addresses a defect that can lead to uncontrollable pitch and catastrophic outcomes."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This amendment expands the original directive by mandating actuator modification/inspection via the Fokker service bulletin and by explicitly including spare Menasco actuators P/No 11100 and an installation prohibition. It also sets staged compliance deadlines (Part 1 and Part 2) rather than only ad‑hoc inspections, thereby formalising required corrective work and parts control."},"complexity_factors":["Narrow, serial‑numbered applicability (Applicability: specified F28 S/N ranges and exclusions).","Mandated action relies on external documents (Requirement: compliance with Fokker SB F28/27‑183; Note 2: refers to Menasco SB 11100‑27‑105).","Phased compliance timing (Compliance: Part 1 by 01 Aug 1995; Part 2 at next removal or by 01 Jan 1998).","Spare parts treatment and installation restriction (Requirement/Compliance: spare Menasco actuators P/No 11100 must comply prior to installation).","Cross‑reference to prior ADs (Note 1: RLD AD 1992‑077/2 (A)), creating possible interaction with existing obligations.","Safety‑critical system implications increase operational and maintenance burden (Background: incident of stabilizer runaway gives rationale).","Potential administrative burden for tracking serial numbers and removals across operator fleets."],"plain_english_summary":"This airworthiness directive requires operators of specified Fokker F28 aeroplanes and spare Menasco actuators to modify or inspect the horizontal stabilizer actuator servo valve assembly in accordance with Fokker Service Bulletin SB F28/27‑183. It also prohibits installing unmodified spare actuators.\n\nIt affects aircraft owners, maintenance organisations and parts suppliers for the listed serial numbers, with staged compliance dates aimed at preventing stabilizer runaway after reported in‑flight incidents."},"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-f28-70-amdt-1-horizontal-stabilizer-actuator-servo-valve-assembly","history":"/api/acts/ad-f28-70-amdt-1-horizontal-stabilizer-actuator-servo-valve-assembly/history","analysis":"/api/acts/ad-f28-70-amdt-1-horizontal-stabilizer-actuator-servo-valve-assembly/analysis","conflicts":"/api/acts/ad-f28-70-amdt-1-horizontal-stabilizer-actuator-servo-valve-assembly/conflicts","importantCases":"/api/acts/ad-f28-70-amdt-1-horizontal-stabilizer-actuator-servo-valve-assembly/important-cases","documents":"/api/acts/ad-f28-70-amdt-1-horizontal-stabilizer-actuator-servo-valve-assembly/documents"}}