{"id":"F2006B02749","name":"AD/B727/48 - Stabilizer Trim System Brake Assembly - Modification","slug":"ad-b727-48-stabilizer-trim-system-brake-assembly-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42091,"registerId":"commonwealth-F2006B02749-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B727/48 - Stabilizer Trim System Brake Assembly - Modification","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 727 Series Aeroplanes\n\n \n\nAD/B727/48 Stabilizer Trim System Brake Assembly - Modification\n\n\n5/67\n\n \n\nApplicability: All models.\n\n \n\nRequirement: Install additional spacers under pawls in the stabilizer trim system brake, Boeing P/N 10-60822-1, Western Gear P/N 4472, R155, Western Gear S/Nos. 101 through 225, in accordance with para. 2 of Western Gear SB “Flight Controls - Stabilizer Brake Assembly, Western Gear P/No. 4472 R155 Install Additional Spacers Under Pawls”.\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\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"No change of scope is apparent within the text provided. The AD applies to all Boeing 727 models but confines the required modification to specific stabilizer trim brake assemblies identified by part and serial numbers, and it directs compliance with paragraph 2 of the referenced Western Gear service bulletin. The instrument itself does not indicate an amendment or expansion beyond that single modification."},"complexity_factors":["Narrow technical action: single, well-defined modification (install spacers under pawls). (Requirement)","Reference to external procedural document: compliance depends on paragraph 2 of a Western Gear service bulletin rather than full procedure being contained in the AD. (Requirement)","Part/serial-number specificity: only applies to brake assemblies with specified P/Ns and S/Ns, requiring record checks. (Requirement)","Regulatory formality: issued as an Airworthiness Directive under Part 39 (imposes a mandatory obligation), but the excerpt omits timing and alternative compliance details. (header; Requirement)","Operational impacts: requires parts, labour and aircraft downtime, which are practical but routine burdens for operators. (Requirement)"],"plain_english_summary":"This Airworthiness Directive mandates installing additional spacers under the pawls of specified stabilizer trim brake assemblies on Boeing 727 aeroplanes. It affects aircraft owners/operators and maintenance organisations, who must identify affected units by part/serial number and carry out the modification per paragraph 2 of the referenced Western Gear service bulletin; costs and downtime fall to operators and compliance is compulsory under the AD."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific mechanical component. It has not expanded beyond its original purpose of addressing a known safety issue with the stabilizer trim brake assembly on Boeing 727 aircraft."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 2 defined applicability criteria (aircraft model and specific part serial numbers)","Single, straightforward requirement with clear reference to external technical document (Western Gear Service Bulletin)","No nested exceptions, conditional logic, or cross-references to other legislation","Highly specific technical scope limited to one mechanical component on one aircraft type"],"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 **Boeing 727 series aircraft** to modify the stabilizer trim system brake assembly. Specifically, they must install additional spacers under the \"pawls\" (mechanical locking components) in a particular brake assembly made by Western Gear.\n\n**Who it affects:**\n- Anyone who owns or operates Boeing 727 aircraft (all models)\n- Specifically applies to aircraft with Western Gear brake assemblies with serial numbers 101 through 225\n\n**Why it matters:**\nThe stabilizer trim system controls the angle of the aircraft's horizontal tail surface, which is critical for maintaining stable flight. The brake assembly prevents unwanted movement of this system. This modification addresses a safety issue with the original design — without the additional spacers, the pawls might not function correctly, potentially leading to loss of control over the stabilizer trim.\n\n**What must be done:**\nOperators must follow the instructions in Western Gear Service Bulletin (SB) regarding \"Flight Controls - Stabilizer Brake Assembly\" to install the additional spacers under the pawls."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b727-48-stabilizer-trim-system-brake-assembly-modification","history":"/api/acts/ad-b727-48-stabilizer-trim-system-brake-assembly-modification/history","analysis":"/api/acts/ad-b727-48-stabilizer-trim-system-brake-assembly-modification/analysis","conflicts":"/api/acts/ad-b727-48-stabilizer-trim-system-brake-assembly-modification/conflicts","importantCases":"/api/acts/ad-b727-48-stabilizer-trim-system-brake-assembly-modification/important-cases","documents":"/api/acts/ad-b727-48-stabilizer-trim-system-brake-assembly-modification/documents"}}