AD/PT6A/16 - Improved Strength P.T. Shaft Housing and Reduction Gearbox Condition Monitoring

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 106, addresses the critical issue of ensuring the airworthiness of aircraft engines, particularly those of the Pratt and Whitney Canada PT6A Series. This legislative instrument, enacted by the Commonwealth of Australia, is designed to maintain stringent safety standards in civil aviation, focusing on the modification and monitoring of turbine engines to prevent mechanical failure and ensure safe operation. The enactment by the Parliament of Australia underscores the importance of these safety measures, with the policy objective being to mitigate risks associated with engine failure, thereby enhancing overall aviation safety. The Civil Aviation Safety Authority (CASA) is the enforcing body responsible for overseeing compliance with these regulations, which mandate specific modifications and inspections to ensure the longevity and reliability of the engine components in question.

Scope and Application

The Civil Aviation Safety Authority's (CASA) AD/PT6A/16, found within the Civil Aviation Regulations 1998, applies specifically to certain Pratt & Whitney Canada PT6A series turbine engines, including models PT6A-6, -6A, -6B, -6/C20, -20, -20A, 20B, -21, PT6B-9, PT6A-27, -28, and -34. This legislative instrument is designed to ensure the airworthiness of these engines by mandating modifications and inspections that address issues related to the strength of the P.T. shaft housing and the condition monitoring of the reduction gearbox. The directive applies across the Commonwealth of Australia, affecting aircraft operators, maintenance providers, and any other entities involved in the maintenance and operation of these engines. The requirements include modifying affected engines with specific power turbine shaft housings, installing magnetic chip detectors, and conducting regular checks and inspections of the magnetic chip detectors and oil filters. Compliance with these directives is mandatory, with specific timelines for when modifications and inspections must be completed. The regulations also allow for adjustments to inspection intervals under certain conditions, such as when specific modifications have been incorporated into the engine build status, as referenced in AD/UAC-T/26.

Key Provisions

The Civil Aviation Regulations 1998, specifically under PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES, mandates modifications to Pratt and Whitney Canada Turbine Engines - PT6A Series, as outlined in AD/PT6A/16. The directive applies to a range of PT6A engine models, including -6, -6A, -6B, -6/C20, -20, -20A, 20B, -21, PT6B-9, PT6A-27, -28, and -34. The directive outlines several key requirements. Firstly, engines fitted with a P.N 3010548 welded power turbine shaft housing must be modified according to UACL SB No. 1138, Rev. 3 (Section 1). Secondly, all affected engines must have a magnetic chip detector installed in accordance with UACL SB No. 1217, Rev. 4 (Section 2). Thirdly, for engines modified under Section 2, the magnetic chip detector pins must be checked for electrical continuity, and if any contaminants are found, they must be removed and inspected in line with the guidance provided in the applicable engine Maintenance Manual (Section 3). Finally, all engines must undergo a visual inspection of the main engine oil filter element for signs of metallic contamination (Section 4). The obligations imposed by this directive require that modifications to the engine be completed within specific timeframes. For the modification of the welded power turbine shaft housing, this must occur during the next overhaul shop visit but no later than the next engine reconditioning after 30 April 1975 (Section 1). Installation of the magnetic chip detector must occur as soon as the necessary parts are available but no later than 30 October 1975 for engines requiring modification in accordance with Section 1, and no later than 31 January 1976 for all other affected engines (Section 2). The checks and inspections of the magnetic chip detector and the oil filter element must be conducted at intervals not exceeding 25 hours and 50 hours of time in service after 30 April 1975, respectively (Sections 3 and 4). These inspections and checks may revert to the normal aircraft maintenance inspection periods if the engines comply with the requirements of Australian AD/UAC-T/26 (Note 1). Failure to comply with the requirements of this directive can lead to civil and criminal consequences. Specifically, the regulations require that certifications include reference to the parts of this Directive that have been complied with. Failure to adhere to the mandated inspection and modification timelines may result in penalties, although the exact penalties are not specified in the directive. It is implied that non-compliance could affect the airworthiness certification of the aircraft, potentially leading to grounding and other enforcement actions by the Civil Aviation Safety Authority.