{"id":"F2006B02963","name":"AD/B737/63 - Stabilizer Trim Jackscrew Actuator","slug":"ad-b737-63-stabilizer-trim-jackscrew-actuator","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42305,"registerId":"commonwealth-F2006B02963-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/63 - Stabilizer Trim Jackscrew Actuator","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Boeing 737 Series Aeroplanes\n\n \n\nAD/B737/63 Stabilizer Trim Jackscrew Actuator 12/91\n\nApplicability: Model 737-300, -400 and -500 series, as listed in Boeing SB 737-27-1161. Requirement:               Action in accordance with the Technical Requirements of FAA AD 91-20-04 Amdt\n\n39-8038.\n\n \n\nNote: Boeing SB 737-27-1161 refers.\n\n \n\nCompliance: As specified in the requirement document with a revised effective date of 12 December 1991 for Australian registered aircraft.\n\n \n\nBackground: Reports have been received of worn auxiliary trim brakes that may allow slippage and movement of the horizontal stabilizer under certain conditions. The effective date required by the FAA is extended by one month.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-limited safety directive focused on a specific mechanical defect in specific aircraft models. It has not expanded beyond its original purpose of mandating inspection/repair of stabilizer trim jackscrew actuators."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly referenced (Boeing SB 737-27-1161 — a service bulletin)","No nested conditional logic or exceptions","Single cross-reference to external FAA document (AD 91-20-04) which contains the actual technical requirements","No interpretation section or definitions clause","Straightforward applicability criteria (specific aircraft models by series number)","Compliance date is fixed and absolute (no tiered or conditional deadlines)"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on certain Boeing 737 aircraft.\n\n**Who it affects:** Owners and operators of **Boeing 737-300, -400, and -500 series aircraft** registered in Australia. These are specific older models of the popular 737 jet (often called the \"Classic\" series).\n\n**What it requires:** Operators must follow the technical instructions in an American safety order (FAA AD 91-20-04) to inspect and fix a problem with the **stabilizer trim jackscrew actuator** — a mechanical component that helps control the aircraft's pitch (whether the nose points up or down).\n\n**The safety problem:** The **auxiliary trim brakes** — backup braking parts within this system — can wear out and allow the horizontal stabilizer (the tail wing that controls pitch) to slip or move unexpectedly. This could affect the pilot's ability to control the aircraft's angle during flight.\n\n**When to comply:** Australian operators have until **12 December 1991** to complete the required actions — one month later than the original US deadline.\n\n**Why it matters:** This prevents potential loss of pitch control, which could lead to dangerous flight conditions or accidents. Airworthiness directives are legally binding — operators cannot fly these aircraft without completing the required work."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The instrument changes the timing of when the FAA-prescribed actions must be complied with for Australian-registered aircraft by extending the FAA’s effective date by one month and setting the Australian effective date to 12 December 1991. It otherwise adopts the FAA AD’s technical requirements and references Boeing SB 737-27-1161 for the list of affected models. (Requirement; Note; Compliance; Background)"},"complexity_factors":["External cross-references: the AD requires action “in accordance with” FAA AD 91-20-04 and refers to Boeing SB 737-27-1161 rather than reproducing technical steps (Requirement; Note).","Narrow applicability: applies only to specific Boeing 737-300/-400/-500 series aircraft as listed in the Boeing service bulletin, so implementers must confirm model/status against that list (Applicability; Note).","Timing adjustment: CASA revises the effective date for Australian-registered aircraft, creating a divergence in compliance timing from the FAA AD (Compliance; Background).","Limited textual detail: the AD text is short and delegates technical content to external documents, increasing the need to consult additional materials (Requirement; Note).","Regulatory layering: national adoption of an FAA AD introduces coordination tasks for operators and maintenance providers between international (FAA) and national (CASA) requirements (Requirement; Compliance)."],"plain_english_summary":"Mandates that Australian-registered Boeing 737‑300/‑400/‑500 aircraft referenced in Boeing SB 737‑27‑1161 comply with FAA Airworthiness Directive 91‑20‑04—i.e. required inspections/repairs to address worn auxiliary trim brakes that can allow stabilizer movement. CASA adopts the FAA technical requirements but sets the Australian effective date as 12 December 1991, a one‑month extension."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-63-stabilizer-trim-jackscrew-actuator","history":"/api/acts/ad-b737-63-stabilizer-trim-jackscrew-actuator/history","analysis":"/api/acts/ad-b737-63-stabilizer-trim-jackscrew-actuator/analysis","conflicts":"/api/acts/ad-b737-63-stabilizer-trim-jackscrew-actuator/conflicts","importantCases":"/api/acts/ad-b737-63-stabilizer-trim-jackscrew-actuator/important-cases","documents":"/api/acts/ad-b737-63-stabilizer-trim-jackscrew-actuator/documents"}}