{"id":"F2006L02500","name":"AD/F100/81 - Autopilot Disconnect Unit","slug":"ad-f100-81-autopilot-disconnect-unit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":59705,"registerId":"commonwealth-F2006L02500-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Fokker F100 (F28 Mk 100) Series Aeroplan","sectionType":"division","heading":"Fokker F100 (F28 Mk 100) Series Aeroplanes","content":"### Fokker F100 (F28 Mk 100) Series Aeroplanes\n\n| AD/F100/81 | Autopilot Disconnect Unit | 9/2006 |\n| ---------- | ------------------------- | ------ |\n\n| Applicability: | F28 Mark 0070 and 0100 aeroplanes.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Modify the aeroplane in accordance with Section 3 - Accomplishment Instructions of Fokker Service Bulletin SBF100-22-050 dated 25 April 2006 or later EASA approved revision.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n|                | Note: CAA-NL AD NL-2006-010 (EASA Approval 2006-0195) refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n| Compliance:    | Within 36 months after the effective date of this Directive.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n|                | This Airworthiness Directive becomes effective on 31 August 2006.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n| Background:    | The Netherlands Civil Aviation Authority (CAA-NL) has advised that to date, there have been at least 10 reported events on Fokker 70 (F28 Mark 0070) and Fokker 100 (F28 Mark 0100) aircraft where the flight crew manually overpowered the autopilot, inadvertently neglecting to disengage the autopilot.                                                                                                                                                                                                                                                                                                                                                                                                                       |\n|                | Detailed investigation of these incidents has shown that this usually occurs in a high workload environment that demands immediate manual control of the aircraft by the pilot flying, eg terrain warning. When the autopilot is not disengaged, the elevator servomotor is overpowered and the horizontal stabilizer is moved by the Automatic Flight Control & Augmentation System (AFCAS) auto-trim in a direction opposite to the (manual) deflection of the elevator, causing high elevator control forces. This condition, if not corrected, could cause the stabilizer to move to an extreme out-of-trim position, creating the (remote) possibility of loss of control of the aircraft, due to the extreme control loads. |\n\n|     | In the original design of AFCAS, operation of the control wheel-mounted stabilizer trim switches has no effect when the autopilot is engaged. Based on the assumption that stabilizer trim switches will be operated by the pilot flying when encountering high control forces, an Autopilot Disconnect Unit (ADU) has been developed that disconnects the autopilot when the stabilizer trim switches are operated. Since a potentially unsafe condition has been identified that may exist or develop on aircraft of this type design, this Directive requires the installation of ADUs and associated wiring changes. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n21 July 2006","sortOrder":0},{"sectionNumber":"AD/F100/81","sectionType":"part","heading":"AD/F100/81","content":"## AD/F100/81","sortOrder":1},{"sectionNumber":"Autopilot Disconnect Unit","sectionType":"part","heading":"Autopilot Disconnect Unit","content":"## Autopilot Disconnect Unit","sortOrder":2},{"sectionNumber":"9/2006","sectionType":"part","heading":"9/2006","content":"## 9/2006","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope remains aligned with the original intent: to address an identified unsafe condition by requiring ADU installation on the specified Fokker models per the service bulletin and EASA approval. The directive limits application to those models and sets a fixed compliance period."},"complexity_factors":["Narrow applicability: only F28 Mark 0070 and 0100 models","Technical modification: installation of ADU and associated wiring per manufacturer service bulletin","Dependency on external approval: requires EASA‑approved revision of the service bulletin","Safety‑critical interface with flight controls (autopilot and trim systems)","Compliance timeline: 36‑month mandatory window affects maintenance scheduling","Operational cost and downtime for aircraft operators (parts, labour, docking)","Regulatory cross‑reference to CAA‑NL AD NL‑2006‑010 and EASA approval","Limited discretion for operators: prescriptive installation instructions reduce alternative compliance options"],"plain_english_summary":"This Airworthiness Directive requires operators of Fokker F70 (F28 Mark 0070) and Fokker 100 (F28 Mark 0100) aeroplanes to install an Autopilot Disconnect Unit (ADU) and associated wiring per Fokker Service Bulletin SBF100‑22‑050 (or a later EASA‑approved revision). The ADU causes the autopilot to disconnect when the stabilizer trim switches are used, preventing opposing autopilot auto‑trim that can produce very high control forces. Compliance is mandatory within 36 months of the effective date, so aircraft operators pay for and schedule the modification."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope: mandating a specific safety modification for a particular aircraft type based on identified operational incidents. There is no evidence of scope creep; the directive addresses exactly the safety issue described in the background."},"complexity_factors":["Single, specific technical requirement with clear reference to manufacturer service bulletin","Only one defined applicability criterion (two specific aircraft models)","Simple compliance timeline (36 months from effective date)","No nested exceptions, conditional logic, or alternative compliance methods","Background explanation is narrative but not legally operative","Total length is approximately one page","Cross-references limited to one foreign aviation authority directive (CAA-NL AD NL-2006-010) and one manufacturer document"],"plain_english_summary":"This AD mandates installation of an Autopilot Disconnect Unit (ADU) on Fokker 70 and Fokker 100 aircraft in Australia so the autopilot automatically disengages when pilots use the manual trim switches. It addresses at least 10 incidents where pilots took manual control but left autopilot engaged, causing conflicting inputs, heavy control forces, and risk of loss of control.\n\nAffected operators must install the ADU and wiring per Fokker Service Bulletin SBF100-22-050 (or later approved) within 36 months of 31 August 2006."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f100-81-autopilot-disconnect-unit","history":"/api/acts/ad-f100-81-autopilot-disconnect-unit/history","analysis":"/api/acts/ad-f100-81-autopilot-disconnect-unit/analysis","conflicts":"/api/acts/ad-f100-81-autopilot-disconnect-unit/conflicts","importantCases":"/api/acts/ad-f100-81-autopilot-disconnect-unit/important-cases","documents":"/api/acts/ad-f100-81-autopilot-disconnect-unit/documents"}}