COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Pratt and Whitney Canada Turbine Engines - PT6A Series
AD/PT6A/28 Water Washing 2/99 DM
Applicability: All PT6A series engines installed in single engine aircraft:
- Carrying passengers for hire or reward in Civil Aviation Regulation (CAR) 206 commercial operations, and
2. Conducted in a salt laden environment.
Note 1: For the purpose of this directive, operating in a salt laden environment is defined as a take-off and landing within 10 nautical miles of the sea or, the flight route is within 10 nautical miles or over the sea and at an altitude of less than 10,000 feet .
Requirement: 1. In accordance with an inspection procedure and the criteria for acceptable damage detailed in the applicable Pratt and Whitney Canada maintenance manual, carry out a visual inspection of the compressor turbine blades for evidence of sulphidation, and
2. Carry out engine compressor and compressor turbine water washing in accordance with the procedure detailed in the applicable Pratt and Whitney Canada maintenance manual.
Note 2: The visual inspection may be carried out by either a boroscope inspection or a hot section inspection.
Compliance: 1. Unless the compressor turbine has been inspected within 200 hours time in service prior to the effective date of this directive, carry out the inspection within 10 hours time in service from the effective date of this directive.
2. In accordance with the “Wash Schedule Recommendations” table detailed in the applicable Pratt and Whitney Canada maintenance manual.
This Airworthiness Directive becomes effective on 30 December 1998.
Background: This Directive has been issued to require an inspection of the compressor turbine blades for evidence of sulphidation and, water washing of the compressor and compressor turbine. The requirement reflects concern for the airworthiness of single PT6A engine aircraft operated in a salt laden environment when water washing is not carried out at a frequency recommended by the manufacturer.
The concern results from the investigation of a recent PT6A in flight shut down event which has been attributed to compressor turbine blade fracture resulting from sulphidation. The level of sulphidation was consistent with inadequate water washing.
Overview
The Civil Aviation Regulations 1998, as amended by the Pratt and Whitney Canada Turbine Engines - PT6A Series AD/PT6A/28, was enacted to address the problem of compressor turbine blade sulphidation in PT6A series engines used in single engine aircraft operating in salt-laden environments. The regulation was introduced following an investigation into an in-flight engine shutdown event attributed to blade fracture due to sulphidation, which was consistent with inadequate water washing. This Airworthiness Directive, effective from 30 December 1998, requires visual inspections of the compressor turbine blades for sulphidation and the implementation of engine water washing procedures to ensure the airworthiness of aircraft operating under the specified conditions. The objective of this directive is to mitigate the risks associated with inadequate water washing by mandating inspections and water washing to prevent compressor turbine blade damage and subsequent engine failures.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 106, mandates the applicability of Airworthiness Directive AD/PT6A/28 concerning Pratt and Whitney Canada PT6A series turbine engines. This directive applies to all PT6A series engines installed in single-engine aircraft that are involved in commercial operations as outlined in Civil Aviation Regulation (CAR) 206, specifically those carrying passengers for hire or reward. Furthermore, it is pertinent to aircraft operating in salt-laden environments, defined as those taking off or landing within 10 nautical miles of the sea, or those flying within 10 nautical miles of or over the sea at altitudes below 10,000 feet. This directive does not extend to any other types of engines or aircraft outside the specified parameters. The requirement for compliance involves conducting a visual inspection of the compressor turbine blades for sulphidation and performing engine compressor and compressor turbine water washing as per the procedure detailed in the Pratt and Whitney Canada maintenance manual. The directive becomes effective on 30 December 1998, with specific timelines for inspections and washing schedules outlined in the applicable maintenance manual.
Key Provisions
The Civil Aviation Regulations 1998, specifically Part 39 - 106 under the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, includes a directive concerning Pratt and Whitney Canada Turbine Engines of the PT6A series (AD/PT6A/28). This directive mandates certain maintenance procedures for these engines when installed in single-engine aircraft that carry passengers for hire or reward in commercial operations, particularly in salt-laden environments (section 1). A salt-laden environment, for the purposes of this directive, is defined as operating within 10 nautical miles of the sea or flying over the sea at altitudes less than 10,000 feet (section 2).
The directive requires two key actions: Firstly, a visual inspection of the compressor turbine blades for sulphidation must be conducted in accordance with the inspection procedure and criteria for acceptable damage as detailed in the Pratt and Whitney Canada maintenance manual (section 1). Secondly, the engine's compressor and compressor turbine must be water-washed following the procedure outlined in the applicable Pratt and Whitney Canada maintenance manual (section 2). The visual inspection can be performed using either a boroscope inspection or a hot section inspection (Note 2). Compliance with this directive requires that if the compressor turbine has not been inspected within 200 hours of time in service prior to the directive's effective date, the inspection must be carried out within 10 hours of time in service from the effective date (section 1.1). Additionally, the water washing must be conducted in line with the "Wash Schedule Recommendations" table in the Pratt and Whitney Canada maintenance manual (section 1.2).
Breach of this Airworthiness Directive could lead to serious consequences, as it becomes effective on 30 December 1998. Non-compliance with these maintenance requirements may result in compromised airworthiness, potentially leading to in-flight engine shut-down events. This is particularly significant given the investigation into a recent in-flight PT6A engine shut-down, which was attributed to compressor turbine blade fracture due to sulphidation. The sulphidation level observed was consistent with inadequate water washing, underscoring the importance of adhering to these maintenance directives to ensure the safety of air operations in salt-laden environments. Failure to comply with these requirements could result in regulatory action, including fines or other penalties as stipulated by the Civil Aviation Regulations.