AD/CESSNA 500/25 - Thrust Reverser Throttle Load Limiter

Overview

The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority, were enacted to ensure the safety and efficiency of civil aviation in Australia. Within this extensive regulatory framework, Part 39 specifically addresses the airworthiness of aircraft, including issuing directives to address specific safety concerns. One such directive, AD/CESSNA 500/25, was introduced to mitigate risks associated with the thrust reverser mechanism in Cessna 500 (Citation) Series aeroplanes. This directive was necessitated by an incident where the throttle control levers were advanced during thrust reverser transition, activating a spring-loaded limiter device and leading to significantly diminished power control authority. The directive mandates compliance within 150 hours of time in service after its issuance on 24 June 1993, aiming to prevent similar incidents and enhance flight safety. The directive requires affected models, specifically units numbered from -0001 to 0689 equipped with thrust reversers, to undergo modifications as detailed in Cessna Service Bulletin 500-78-11. This action aligns with the overarching policy objective of the Civil Aviation Regulations 1998 to maintain the highest standards of airworthiness and protect the public from aviation-related hazards. By implementing this specific directive, the Civil Aviation Safety Authority seeks to ensure the reliability and safety of the affected aircraft, thus reinforcing the safety culture within Australia's aviation industry.

Scope and Application

The Civil Aviation Regulations 1998, as amended under the Civil Aviation Act 1988, specifically address the safety of aircraft operations within Australia, and Part 39 - 105, concerning the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, applies to all aircraft registered in Australia and operated by Australian entities. The regulation in question pertains to the Cessna 500 (Citation) Series Aeroplanes, specifically targeting models 500 and 501 with unit numbers from -0001 to 0689, that are equipped with thrust reversers. The directive requires modifications to be made in accordance with Cessna Service Bulletin 500-78-11 to address an identified issue where an attempt to advance the throttle control levers during thrust reverser transition led to the activation of a spring-loaded limiter device. This activation subsequently resulted in severely reduced power control authority, highlighting a critical safety concern. Compliance with this directive must be achieved within 150 hours of time in service after 24 June 1993. This regulation underscores the importance of maintaining airworthiness standards and ensuring the safety of aircraft operations by mandating specific modifications to prevent operational hazards.

Key Provisions

The key operative sections of the AD/CESSNA 500/25 regulation, as outlined in Part 39 of the Civil Aviation Regulations 1998, require modifications to the thrust reverser throttle load limiter for specific models of Cessna 500 and 501 series aeroplanes. Specifically, Section 39-105 mandates that models 500 and 501 with unit numbers from -0001 to -0689, which are equipped with thrust reversers, must be modified in accordance with Cessna Service Bulletin (SB) 500-78-11. This directive is applicable to ensure safety and compliance with the Federal Aviation Administration (FAA) AD 93-05-15. The compliance timeline for this modification is set at 150 hours of time in service after the effective date of 24 June 1993. The Act imposes specific obligations on the owners and operators of the affected aircraft. They are required to ensure that the necessary modifications are performed by qualified personnel in line with the instructions provided in the Cessna Service Bulletin. These modifications are crucial to prevent incidents where the spring-loaded limiter device is inadvertently activated during thrust reverser transition, which could lead to a loss of power control authority. The onus is on the operators to ensure that these modifications are carried out within the stipulated timeframe to maintain airworthiness. Failure to comply with the AD/CESSNA 500/25 directive can lead to serious safety implications. The Civil Aviation Safety Authority (CASA) may take enforcement action against operators who do not adhere to the requirements. Non-compliance could result in the grounding of the aircraft, which would prevent it from being used for commercial or private flights until the necessary modifications are completed. Additionally, operators may face significant penalties, including fines and potential criminal charges, if the non-compliance leads to an aviation incident or poses a significant risk to flight safety. The specific penalties are outlined in the Civil Aviation Regulations and can vary based on the severity and circumstances of the breach.