AD/CESSNA 550/21 - Thrust Reverser Throttle Load Limiter

Overview

The Civil Aviation Regulations 1998, as amended by the legislative instrument F2006B08427, introduces Airworthiness Directives to address specific safety concerns in civil aviation. This particular directive, AD/CESSNA 550/21, targets Cessna 550 (Citation II) Series Aeroplanes, aiming to mitigate the risk of reduced power control authority due to issues with the thrust reverser throttle load limiter. This problem was identified after an incident where the activation of the limiter during thrust reverser transition severely compromised the pilots' control over engine power. The directive was enacted by the Civil Aviation Safety Authority, ensuring compliance within 150 hours of the aircraft's time in service following 24 June 1993. The policy objective is to enhance flight safety by mandating modifications as per Cessna Service Bulletins 550-78-03 and S550-78-04, aligning with the Federal Aviation Administration’s AD 93-05-15. This legislative measure underscores the Commonwealth of Australia's commitment to stringent aviation safety standards, ensuring that aircraft operations remain within safe parameters by addressing specific mechanical vulnerabilities. The directive mandates modifications to the thrust reverser system to prevent incidents of severely reduced power control, thus safeguarding the integrity of flight operations and the safety of passengers and crew.

Scope and Application

The Civil Aviation Regulations 1998, as amended, under the authority of the Civil Aviation Safety Authority, apply to all operators of Cessna 550 (Citation II) Series Aeroplanes, specifically those with unit numbers ranging from -0002 to -0678 for the 550 model and from -0001 to -0160 for the 551 model, that are equipped with thrust reversers. This regulation is intended to ensure the airworthiness of these aircraft by mandating modifications to the thrust reverser throttle load limiter to prevent incidents where the load limiter device is inadvertently activated, leading to a significant reduction in power control authority. The modifications must be implemented in accordance with the relevant Cessna Service Bulletins (SBs 550-78-03 and S550-78-04) and should be completed within 150 hours of time in service following 24 June 1993, the date of the directive. The scope of this regulation is national, applying across all states and territories of Australia, and there are no stated exclusions or exemptions within the directive itself. However, the application and enforcement of these regulations may be subject to further clarification or adjustment through subordinate instruments issued by the Civil Aviation Safety Authority.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, includes a Schedule of Airworthiness Directives that governs the maintenance and operation of aircraft in Australia. One such directive, AD/CESSNA 550/21, pertains to the Cessna 550 (Citation II) Series Aeroplanes, focusing on the thrust reverser throttle load limiter (Section 1). This directive applies to models 550 and 551 with unit numbers ranging from -0002 to -0678 and S550 unit numbers from -0001 to -0160, all of which are equipped with thrust reversers (Section 2). The directive mandates that modifications be made to the aircraft in accordance with Cessna Service Bulletins 550-78-03 and S550-78-04, as applicable (Section 3). This modification requirement is consistent with FAA AD 93-05-15, indicating an international consensus on addressing this issue (Section 4). Operators and owners of the specified Cessna 550 and 551 aircraft must ensure compliance with the directive within 150 hours of time in service after 24 June 1993 (Section 5). This means that they need to implement the required modifications to the thrust reverser throttle load limiter within this timeframe to maintain the airworthiness of their aircraft. Failure to comply with the directive could result in the aircraft being deemed unairworthy, leading to potential grounding and operational disruptions (Section 6). Failure to adhere to the provisions of AD/CESSNA 550/21 could lead to serious consequences. The Civil Aviation Safety Authority (CASA) enforces these regulations rigorously, and non-compliance may result in enforcement actions. While specific penalties are not detailed in the directive, non-compliance with airworthiness directives generally can lead to significant penalties under the Civil Aviation Act 1988 and Civil Aviation Regulations 1988. These can include substantial fines and potential criminal charges for operators who knowingly allow an unairworthy aircraft to be used (Section 7). Additionally, pilots who operate an aircraft that does not comply with applicable airworthiness directives may face professional consequences, including the suspension or revocation of their pilot's licence (Section 8). In summary, AD/CESSNA 550/21 is a critical directive aimed at ensuring the safe operation of certain Cessna 550 and 551 aircraft by addressing a specific issue with the thrust reverser throttle load limiter. Operators must adhere to the directive's requirements, which include making necessary modifications within a specified timeframe. Non-compliance not only risks the airworthiness of the aircraft but can also result in severe regulatory and legal consequences, including fines and criminal charges for operators and potential disciplinary action for pilots.