AD/PMC/21 - Three Blade Propeller Hub - Modification or Replacement

Overview

The Civil Aviation Regulations 1998, under Part 39, specifically within the Schedule of Airworthiness Directives, addresses the safety of propellers on certain aircraft models. The regulation in focus here is AD/PMC/21, which pertains to the modification or replacement of three-blade propeller hubs on McCauley propellers for specific Cessna 206 series aircraft. This directive was enacted to address safety concerns associated with propeller hub integrity on these models, particularly those equipped with normally aspirated Continental IO-520 engines that have not been modified in accordance with a previous McCauley Service Bulletin (SB No. 88). The regulation was issued by the Civil Aviation Safety Authority to ensure the continued airworthiness of these aircraft and to mitigate potential risks associated with propeller failure. The policy objective of AD/PMC/21 is to mandate timely modifications or replacements of the affected propeller hubs to enhance the safety and reliability of the aircraft in question. This is achieved by setting specific compliance timelines based on the total time in service of the propellers, ensuring that these critical components are inspected and, if necessary, repaired or replaced within defined periods. The directive is enforceable under the Civil Aviation Regulations, and compliance is to be verified against the documentation specified in Cessna Service Letter SL SE71-15 or McCauley Service Bulletin No. 89.

Scope and Application

The Civil Aviation Regulations 1998, specifically within Part 39 and the Airworthiness Directives Schedule for propellers, addresses safety concerns for certain Cessna 206 series aircraft equipped with variable pitch McCauley propellers. This regulation applies to specific models, namely D3A32C77, C79, C88, and C90, and mandates modifications or replacements to the propeller hub for those aircraft with a normally aspirated Continental IO-520 engine that have not been altered in line with McCauley Service Bulletin No. 88. The directive is geographically applicable across the Commonwealth of Australia, thereby extending its reach throughout the nation, ensuring that all relevant aircraft within Australian jurisdiction are compliant. Compliance with this directive is time-sensitive, requiring modifications within specific time frames contingent on the propeller’s accumulated service hours. Propellers that have completed 600 hours or more must be addressed within 25 hours of service after 30 July 1971, while those with 500 hours must be modified before reaching 600 hours. The regulation is enforced through the Civil Aviation Safety Authority and can be extended or further specified by subordinate instruments as necessary to maintain the highest safety standards.

Key Provisions

The Civil Aviation Regulations 1998, particularly Part 39, contain several Airworthiness Directives (AD) which mandate modifications and inspections for specific aircraft components to ensure continued safety and airworthiness. Section 107 of these regulations, under the Authority’s schedule, specifically addresses the modification or replacement of three-blade propeller hubs for certain Cessna 206 series aircraft (section 107.7). The directive AD/PMC/21 applies to models D3A32C77, C79, C88, and C90 of the Cessna 206 series equipped with a normally aspirated Continental IO-520 engine that has not been modified according to McCauley Service Bulletin No. 88, as referenced in AD/PMC/20. The operative sections of AD/PMC/21 require modifications or replacements of the propeller hub for specified Cessna 206 models. Specifically, section 107.7 mandates that these propeller hubs must be modified or replaced if the propellers have completed 600 hours of total time in service, and this must occur within 25 hours of time in service following 30 July 1971. For propellers that have accumulated 500 hours of total time in service but have not yet reached 600 hours, the modification or replacement must be completed before the propellers reach the 600-hour mark. Compliance is to be evidenced by referencing either the Cessna Service Letter SE71-15 or McCauley Service Bulletin No. 89. The obligations imposed by these regulations on the operators and owners of the affected aircraft are clear and specific. They must ensure that the propeller hubs are either modified or replaced according to the stipulated timeframes and conditions. Failure to comply with these requirements can lead to serious safety implications, as the directive is designed to mitigate potential risks associated with the specified propeller hubs. The documentation must be kept updated and available for inspection by the Civil Aviation Safety Authority (CASA), demonstrating that the compliance measures have been implemented correctly. The consequences for non-compliance with these provisions are significant. While the regulations do not explicitly detail specific offences, penalties, or maximum fines, non-compliance can result in the aircraft being deemed unairworthy. This can lead to enforcement actions by CASA, which may include grounding the aircraft until the required modifications are completed. Additionally, operators and owners could face civil penalties or criminal charges if their non-compliance results in safety incidents or violations that endanger public safety. It is essential for all parties involved to adhere strictly to the regulations to avoid these potential repercussions.