{"id":"F2006B08427","name":"AD/CESSNA 550/21 - Thrust Reverser Throttle Load Limiter","slug":"ad-cessna-550-21-thrust-reverser-throttle-load-limiter","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115904,"registerId":"commonwealth-F2006B08427-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 550/21 - 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 550 (Citation II) Series Aeroplanes\n\n \n\nAD/CESSNA 550/21 Thrust Reverser Throttle Load Limiter 7/93\n\nApplicability: Models 550 and 551 unit numbers -0002 to 0678, equipped with thrust reversers and S550 unit numbers -0001 to -0160.\n\n \n\nRequirement: Modify in accordance with Cessna SBs 550-78-03 and S550-78-04 as applicable.\n\n \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","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 2 defined applicability criteria (model/serial number ranges)","Single, unambiguous compliance requirement (modify per specified service bulletins)","Simple deadline structure (150 hours time in service after fixed date)","No nested exceptions, conditional logic, or cross-references to other legislation","Only one external reference (FAA AD 93-05-15) provided as contextual note, not binding condition"],"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 550 Citation II business jets** to install a modification to the **thrust reverser throttle load limiter**. This is a safety device that prevents pilots from accidentally applying too much throttle when the thrust reversers (which help slow the plane down after landing) are deploying or stowing.\n\n**Why it matters:** There was a serious incident where a pilot tried to advance the throttle while the thrust reversers were moving. This triggered the spring-loaded safety limiter, which then moved out of position. The result? The pilots suddenly had very little control over engine power — a dangerous situation during a critical phase of flight (landing or takeoff). This AD fixes that design flaw before it causes an accident.\n\n**Who must comply:**\n- **Cessna 550 and 551 models** with serial numbers from -0002 to -0678 (if they have thrust reversers installed)\n- **Cessna S550 models** with serial numbers from -0001 to -0160\n\n**What must be done:** Aircraft must be modified following specific Cessna Service Bulletins (SB 550-78-03 or S550-78-04, depending on the model). This work must be completed **within 150 flight hours after 24 June 1993**.\n\n**The bottom line:** If you own or operate one of these specific Cessna jets in Australia, you legally cannot fly it beyond the compliance deadline without getting this safety modification done. It's about preventing a potentially catastrophic loss of engine control."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument prescribes a corrective modification for a defined set of aircraft; the text does not indicate any expansion or narrowing of subject matter beyond that corrective action."},"complexity_factors":["Narrow applicability by model and serial-number ranges (Applicability: Models 550 and 551 unit numbers -0002 to 0678; S550 -0001 to -0160).","Single mandated hardware modification following manufacturer service bulletins (Requirement: modify per Cessna SBs 550-78-03 and S550-78-04).","Short compliance window tied to flight hours and a fixed effective date (Compliance: within 150 hours after 24 June 1993).","Technical/maintenance execution risk and potential parts or labour costs for operators (implied by Requirement and Background).","Cross-reference to FAA directive (Note: FAA AD 93-05-15), which may affect import of engineering data or accepted methods."],"plain_english_summary":"This airworthiness directive orders operators of specified Cessna 550 and 551 aeroplanes equipped with thrust reversers to modify the throttle load limiter per Cessna Service Bulletins. The change must be carried out within 150 flight hours of 24 June 1993. It is aimed at preventing loss of engine power control that occurred when the spring‑loaded limiter displaced during thrust‑reverser transition."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-550-21-thrust-reverser-throttle-load-limiter","history":"/api/acts/ad-cessna-550-21-thrust-reverser-throttle-load-limiter/history","analysis":"/api/acts/ad-cessna-550-21-thrust-reverser-throttle-load-limiter/analysis","conflicts":"/api/acts/ad-cessna-550-21-thrust-reverser-throttle-load-limiter/conflicts","importantCases":"/api/acts/ad-cessna-550-21-thrust-reverser-throttle-load-limiter/important-cases","documents":"/api/acts/ad-cessna-550-21-thrust-reverser-throttle-load-limiter/documents"}}