{"id":"F2006B08399","name":"AD/CESSNA 500/25 - Thrust Reverser Throttle Load Limiter","slug":"ad-cessna-500-25-thrust-reverser-throttle-load-limiter","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115846,"registerId":"commonwealth-F2006B08399-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 500/25 - Thrust Reverser Throttle Load Limiter","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)  Cessna 500 (Citation) Series Aeroplanes\n\n \n\nAD/CESSNA 500/25 Thrust Reverser Throttle Load Limiter 7/93\n\nApplicability: Models 500 and 501 unit numbers -0001 to 0689 equipped with thrust reversers. Requirement:              Modify in accordance with Cessna SB 500-78-11.\n\nNote: FAA AD 93-05-15 refers.\n\n \n\nCompliance: Within 150 hours time in service after 24 June 1993.\n\n \n\nBackground:  There has been an incident where an attempt to advance the throttle control levers during thrust reverser transition resulted in activation of the spring loaded limiter device. Subsequent displacement of the load limiter resulted in severely reduced power control authority.\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":3,"scope_assessment":{"changed":false,"description":"The directive’s scope is consistent with its stated purpose: it targets specific aircraft serial ranges equipped with thrust reversers and mandates a manufacturer-specified modification to address a defined failure mode. The instrument does not expand beyond those aircraft or require actions other than the specified modification. (Applicability; Requirement; Background)"},"complexity_factors":["Narrow applicability limited to specific models and serial-number range (Models 500 and 501, unit numbers -0001 to -0689). (Applicability)","Single prescriptive action: modify per a named manufacturer service bulletin rather than multiple optional remedies. (Requirement)","Clear, short compliance timeframe (150 hours time in service after 24 June 1993). (Compliance)","Safety-critical technical implementation depends on correct adherence to the service bulletin (potential variability in maintenance execution). (Requirement)","Regulatory dependence on external technical document (Cessna SB 500-78-11) rather than full technical detail within the AD itself. (Requirement)"],"plain_english_summary":"# What this directive does\n\nThis airworthiness directive requires owners/operators of certain Cessna 500 and 501 aeroplanes to modify the thrust reverser throttle load limiter system. The change must be carried out in accordance with Cessna Service Bulletin SB 500-78-11. (Requirement)\n\n# Who it affects\n\n- Applies to Cessna 500 and 501 aeroplanes with unit numbers -0001 to -0689 that are equipped with thrust reversers. (Applicability)\n- The legal responsibility to comply falls on the aircraft owner or operator because airworthiness directives are mandatory under the referenced Civil Aviation Regulations and CASA schedule. (COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 — Schedule of Airworthiness Directives)\n\n# When it must be done\n\nThe modification must be completed within 150 hours time in service after 24 June 1993. (Compliance)\n\n# Why the change is required (official explanation)\n\nThe background states there was an incident in which advancing the throttle during thrust reverser transition activated a spring-loaded limiter device; displacement of that device then produced severely reduced power control authority. The modification is intended to address that failure mode. (Background)\n\n# How it works mechanically\n\n- The directive mandates performing a specific modification described by the manufacturer’s service bulletin. (Requirement)\n- The service bulletin provides the technical steps; the regulator (CASA) requires those steps be followed for the affected serial-numbered aircraft. (Requirement; COMMONWEALTH OF AUSTRALIA ... PART 39)\n\n# Who pays, who decides, and what behaviour changes\n\n- Who pays: Aircraft owners/operators pay for parts, labour and any associated downtime required to perform the service-bulletin modification. (Requirement; Compliance)\n- Who decides: The Civil Aviation Safety Authority issues the directive and sets the compliance deadline; the aircraft owner/operator decides when and how (which approved maintenance organisation or technician) to have the modification performed, subject to the compliance timeframe. (COMMONWEALTH OF AUSTRALIA ... PART 39 — Schedule of Airworthiness Directives; Compliance)\n- Behaviour changes: Operators must schedule the modification into maintenance planning and ensure aircraft are not flown beyond the compliance limit without the modification; maintenance providers must follow the manufacturer’s service bulletin procedures. (Requirement; Compliance)\n\n# Trade-offs, implementation risks and compliance burden\n\n- Direct cost and downtime: The directive creates a one-time cost for each affected aircraft (parts and labour) and requires taking aircraft out of service for the work; these are borne by the owner/operator. (Requirement; Compliance)\n- Implementation risk: Safety outcomes depend on correct execution of the service bulletin; variability in workmanship or incomplete compliance could leave the original risk unmitigated. (Requirement)\n- Dependence on manufacturer documentation: The modification is specified by the manufacturer’s service bulletin, so the regulator relies on that technical standard rather than prescribing alternative technical solutions. (Requirement)\n- Enforcement and operational effect: Because the AD sets a firm compliance window (150 hours TIS after 24 June 1993), operators must integrate the work into short-term maintenance planning or face regulatory non-compliance. (Compliance)\n\n# Cross-reference\n\nThe directive notes a related FAA airworthiness directive (FAA AD 93-05-15), which indicates a corresponding regulatory action by another authority. (Note)\n\n"},"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 single modification to prevent throttle control failures."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 2 defined applicability criteria (model numbers and serial number range)","Single, unambiguous compliance requirement referencing an external technical standard","No nested exceptions, conditional logic, or cross-references to other legislation","Straightforward deadline calculation (150 hours after fixed date)","Minimal regulatory machinery — essentially a direct instruction with background context"],"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). Think of it as a \"recall notice\" for aircraft, but legally binding.\n\n**What it does:** It requires owners and operators of specific Cessna 500 and 501 business jets (serial numbers 0001 to 0689 that have thrust reversers installed) to carry out a specific mechanical modification.\n\n**The problem being fixed:** There was a dangerous incident where a pilot tried to move the throttle levers while the thrust reversers were deploying. This accidentally triggered a safety device (the \"load limiter\"), which then broke or moved out of place. When that happened, the pilots lost most of their ability to control engine power — a serious safety risk during landing or aborted takeoff.\n\n**What must be done:** Aircraft must be modified following Cessna Service Bulletin 500-78-11 (a technical instruction manual from the manufacturer).\n\n**Who it affects:** Operators of early-model Cessna Citation 500/501 jets in Australia with thrust reversers fitted.\n\n**Deadline:** The modification had to be completed within 150 flight hours after 24 June 1993.\n\n**Why it matters:** This prevents a scenario where pilots could lose engine power control during critical phases of flight, potentially leading to loss of aircraft control or runway excursions."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-500-25-thrust-reverser-throttle-load-limiter","history":"/api/acts/ad-cessna-500-25-thrust-reverser-throttle-load-limiter/history","analysis":"/api/acts/ad-cessna-500-25-thrust-reverser-throttle-load-limiter/analysis","conflicts":"/api/acts/ad-cessna-500-25-thrust-reverser-throttle-load-limiter/conflicts","importantCases":"/api/acts/ad-cessna-500-25-thrust-reverser-throttle-load-limiter/important-cases","documents":"/api/acts/ad-cessna-500-25-thrust-reverser-throttle-load-limiter/documents"}}