AD/PW4000/4 - Low Pressure Turbine Stage 4 Disk

Overview

The Civil Aviation Regulations 1998, specifically within Part 39, were enacted by the Commonwealth of Australia to ensure the safety and compliance of civil aviation activities. Among these regulations, the Airworthiness Directive (AD) for Pratt and Whitney Turbine Engines - PW4000 Series, known as AD/PW4000/4, was introduced to address a safety issue concerning the Low Pressure Turbine Stage 4 Disk. This directive was issued in response to concerns about a change in cooling hole geometry on these disks, which reduces cooling air flow and increases stress, potentially leading to uncontained disk failure. The policy objective is to mandate the replacement of affected LPT Stage 4 Disks in accordance with the technical requirements outlined in FAA AD 99-15-01, ensuring compliance with the specified timeframes to mitigate safety risks.

Scope and Application

The Civil Aviation Regulations 1998, specifically under Part 39, mandates airworthiness directives applicable to certain aircraft components, including the Pratt and Whitney Turbine Engines - PW4000 Series, particularly addressing the Low Pressure Turbine Stage 4 Disk as outlined in AD/PW4000/4. This directive applies to all PW4000 series engines equipped with the specified Low Pressure Turbine Stage 4 disk, as identified in FAA AD 99-15-01. The directive requires the replacement of these affected disks in accordance with the technical specifications provided in the aforementioned FAA airworthiness directive. Compliance with this directive is mandatory at the periods stipulated in the requirement document, ensuring that the specified modifications are implemented to mitigate the risk of uncontained disk failure due to reduced cooling air flow and higher stress levels. The directive came into effect on 7 October 1999 and applies across the Commonwealth of Australia, overseen by the Civil Aviation Safety Authority.

Key Provisions

The main operative sections of the Civil Aviation Regulations 1998 (Cth), specifically Part 39, involve the scheduling of Airworthiness Directives (ADs) related to the Pratt and Whitney Turbine Engines of the PW4000 series. Section 39-106 outlines the specific AD/PW4000/4 concerning the Low Pressure Turbine (LPT) Stage 4 Disk. The directive, issued on 7 October 1999, requires that affected LPT Stage 4 disks in PW4000 series engines must be replaced in accordance with the technical requirements stipulated in FAA AD 99-15-01. This directive also references Pratt and Whitney Service Bulletins PW4ENG 72-657 and PW4G 100-72-105, which provide further guidance and technical specifications for the replacement process. The obligations imposed by this Airworthiness Directive are clear and specific. Engine manufacturers and operators of aircraft equipped with the specified PW4000 series engines must ensure that any affected LPT Stage 4 disks are replaced at the intervals detailed in the requirement document, which adheres to FAA AD 99-15-01. Compliance with this directive is critical, as it addresses safety concerns related to a change in cooling hole geometry that results in reduced cooling air flow to the disk, leading to higher stresses. This heightened stress can potentially cause an uncontained disk failure, which poses significant safety risks to aviation operations. Failing to comply with the requirements of this Airworthiness Directive can result in serious consequences. The Civil Aviation Safety Authority (CASA) enforces the regulations and can impose penalties for non-compliance. While the specific penalties are not detailed in the directive, breaches of airworthiness directives can result in civil or criminal penalties, including fines and imprisonment, depending on the severity of the non-compliance. The potential for uncontained disk failure also highlights the critical importance of adhering to these safety directives to prevent accidents and ensure the safety of all personnel and passengers involved in aviation activities.