{"id":"F2006B02809","name":"AD/B737/105 - Rudder Trim Switch","slug":"ad-b737-105-rudder-trim-switch","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42151,"registerId":"commonwealth-F2006B02809-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/105 - Rudder Trim Switch","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)  \nBoeing 737 Series Aeroplanes\n\nAD/B737/105 Rudder Trim Switch 6/97\n\nApplicability: All Boeing Model 737 \\-300, \\-400, \\-500 aeroplanes identified in Boeing Service\n\nBulletin 737-27A1198 dated 6 June 1996.\n\nRequirement: Unless previously incorporated, replace the Aileron/Rudder trim control module in accordance with Service Bulletin 737-27A1198.\n\nNote: FAA AD 97-06-09 Amdt 39-9966 refers.\n\nCompliance: Prior to 22 May 1999.\n\nThis Airworthiness Directive becomes effective on the 22 May 1997.\n\nBackground: Operators have reported unwanted rudder trim motion occurring with the rudder trim actuator after the pilot had adjusted the trim and released the trim switch. This AD mandates the replacement of the module to provide a more reliable module and switch to help prevent the identified condition.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's scope remains the same as stated: it applies to Boeing Model 737-300, -400 and -500 aeroplanes identified in Boeing Service Bulletin 737-27A1198 and requires replacement of the Aileron/Rudder trim control module. The AD prescribes a single remedial action and a fixed compliance date; there is no indication within the text that the scope was broadened or narrowed from that stated purpose (Requirement; Applicability; Compliance; Background)."},"complexity_factors":["Single clear technical action required: replacement of a specific module (Requirement).","Limited applicability: only Boeing 737-300/-400/-500 aeroplanes identified in a specific Boeing Service Bulletin (Applicability).","Fixed compliance window with a single deadline (Compliance; Effective date).","Dependence on an external technical document (Boeing Service Bulletin 737-27A1198) for the detailed steps (Requirement).","No multiple options, conditional pathways or reporting/record-keeping regimes specified in the AD (simplicity reduces complexity)."],"plain_english_summary":"What this directive changes (mechanically):\n\n- The directive requires the physical replacement of the Aileron/Rudder trim control module on certain Boeing 737 aeroplanes. The replacement must be carried out in accordance with Boeing Service Bulletin 737-27A1198 dated 6 June 1996. (Requirement; Applicability)\n\nWho it affects:\n\n- Aircraft operators (owners, lessees or their maintenance organisations) of Boeing Model 737-300, -400 and -500 aeroplanes that are identified in Boeing Service Bulletin 737-27A1198. (Applicability)\n\nWhy it matters (stated purpose and mechanical effect):\n\n- The Background to the directive reports that operators observed unwanted rudder trim motion after the pilot adjusted the trim and released the trim switch. The stated purpose of the mandatory replacement is to provide a more reliable module and switch to help prevent that unwanted rudder trim motion. (Background)\n\nKey compliance mechanics and timing:\n\n- The replacement is mandatory unless it has already been done. (Requirement)\n- The compliance deadline is \"prior to 22 May 1999.\" The directive became effective on 22 May 1997. (Compliance; Effective date)\n- The directive refers to FAA AD 97-06-09 (Note). Operators must follow the Boeing Service Bulletin for the technical method of replacement. (Requirement; Note)\n\nWho pays, who decides, and what changes in behaviour:\n\n- Who pays: The operators of the applicable aeroplanes bear the direct cost of acquiring the replacement module and arranging the maintenance to install it, because the AD requires the operator to replace the module unless it has already been incorporated. (Requirement; Applicability)\n- Who decides / enforces: The Civil Aviation Safety Authority issued the Airworthiness Directive and set the compliance date; the technical execution must follow Boeing Service Bulletin 737-27A1198. (Header; Requirement)\n- Behavioural change required: Affected operators must schedule and complete the replacement before the compliance date; maintenance organisations will follow the Boeing service bulletin procedure when performing the work. The AD does not describe alternative mitigations or a phased approach. (Requirement; Compliance)\n\nOperational, cost and implementation trade-offs (mechanical, not normative):\n\n- Direct costs and downtime: Operators will incur the cost of the replacement unit and labour/time to install it, and must schedule aircraft out of service long enough to carry out the replacement per the Service Bulletin. (Requirement; Compliance)\n- Technical dependence: The AD instructs operators to use a specific Boeing Service Bulletin for the replacement, so the technical content and work scope come from Boeing's document. The AD does not specify other technical alternatives. (Requirement)\n- Identification and verification: Operators must check whether their aeroplanes are listed in the named Boeing Service Bulletin; the AD applies only to aeroplanes identified in that Service Bulletin. (Applicability)\n\nRisks, incentives and likely market effects (mechanical description):\n\n- Safety incentive: The AD creates a regulatory obligation to eliminate a specific reported unsafe condition (unwanted rudder trim motion) by replacing the control module. (Background; Requirement)\n- Demand for parts and maintenance: Requiring replacement for identified aeroplanes will create demand for the replacement modules and for maintenance labour to install them; the AD does not allocate who supplies parts or who performs the work beyond referring to the Service Bulletin. (Requirement)\n- Compliance burden and enforcement risk: Operators who do not incorporate the replacement by the compliance date will be out of compliance with the AD; the directive itself sets the deadline but does not describe enforcement mechanisms. (Compliance)\n\nSource citations: Applicability; Requirement; Compliance; Background; Note (FAA AD reference)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific aircraft. It has not expanded beyond its original purpose of mandating a hardware replacement to prevent uncommanded rudder trim movement."},"complexity_factors":["Very short document (under 200 words)","Only 1 defined term implicitly referenced (Service Bulletin)","Single, unambiguous compliance requirement with clear deadline","No nested conditions, exceptions, or cross-references to other legislation beyond a single note about the corresponding FAA directive","Straightforward applicability test (specific aircraft models identified by reference to manufacturer document)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nIt requires owners and operators of specific Boeing 737 aircraft (the -300, -400, and -500 series) to replace a faulty part — the **Aileron/Rudder trim control module** — with an improved version.\n\n**Why it matters:**\nPilots had reported a dangerous problem: after adjusting the rudder trim and releasing the switch, the trim would keep moving on its own. Unwanted rudder movement can make an aircraft difficult or dangerous to fly. This directive forces the fix to prevent potential accidents.\n\n**Who must comply:**\nAnyone operating the affected Boeing 737 models listed in Boeing's Service Bulletin 737-27A1198 (dated 6 June 1996).\n\n**Deadline:**\nThe replacement had to be done before 22 May 1999. The directive itself took effect on 22 May 1997.\n\n**Key point:**\nThis isn't optional — it's a legal requirement. If you don't comply, you can't legally fly the aircraft in Australian airspace."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-105-rudder-trim-switch","history":"/api/acts/ad-b737-105-rudder-trim-switch/history","analysis":"/api/acts/ad-b737-105-rudder-trim-switch/analysis","conflicts":"/api/acts/ad-b737-105-rudder-trim-switch/conflicts","importantCases":"/api/acts/ad-b737-105-rudder-trim-switch/important-cases","documents":"/api/acts/ad-b737-105-rudder-trim-switch/documents"}}