AD/AL 250/55 Amdt 3 - Gas Producer Rotor Assembly - Tie Bolt P/N 6843388, 6876991 and 6889320

Overview

The Civil Aviation Regulations 1998, enacted by the Commonwealth of Australia, were established to regulate civil aviation safety and address any gaps in ensuring the safe operation of aircraft within Australian airspace. One of the legislative instruments under these regulations is the Civil Aviation Safety Authority Schedule of Airworthiness Directives, specifically AD/AL 250/55 Amendment 3, which pertains to Allison Turbine Engines of the 250 Series. This amendment was introduced to address a critical safety issue concerning the fatigue cracking of certain tie bolts in the gas producer rotor assembly of these engines. The policy objective is to ensure the safe operation of aircraft by mandating the removal and replacement of defective tie bolts with ones of improved strength, thereby mitigating the risk of turbine failure and subsequent damage to the aircraft. Compliance with this directive is required at the next turbine repair or overhaul, or by specified deadlines, to maintain airworthiness standards and protect public safety.

Scope and Application

The Civil Aviation Regulations 1998, as amended, specifically under Part 39 - 106, addresses the safety and operational standards for aviation activities within Australia, thereby applying to all entities and individuals engaged in civil aviation. The scope of this particular regulation, AD/AL 250/55 Amendment 3, focuses on the mandatory removal of specific tiebolts from Allison Turbine Engines - 250 Series, which includes various models such as the 250-C18, 250-C20, 250-B15G, 250-B17, 250-C28B, and 250-C30. This requirement applies to all engines with the specified turbine tie bolts (Part Numbers 6843388, 6876991, and 6889320) fitted, regardless of the manufacturer or operator. The directive mandates compliance with the outlined procedures for removing these tiebolts from service to prevent potential hazards, such as gas producer rotor failure, which could lead to severe damage to the aircraft. Compliance must be achieved either at the next turbine repair or overhaul, or by the specified dates of 28 February 1990 for certain bolts and 28 February 1992 for others, as detailed in the Allison 250 Revision 2 Requirement Documents.

Key Provisions

The key provisions of the Civil Aviation Regulations 1998, specifically Part 39 - 106, pertain to the Allison Turbine Engines - 250 Series. The legislative instrument, AD/AL 250/55 Amendment 3, targets the Gas Producer Rotor Assembly and mandates the removal of certain tie bolts from service. The applicable turbine models include the 250-C18, 250-C20, 250-B15G, 250-B17, 250-C28B, and 250-C30 series, specifically those with the serial numbers detailed in the Requirement Document or fitted with tie bolts bearing the part numbers 6843388, 6876991, or 6889320. The directive requires the removal of tie bolts P/N 6843388 and tie bolts P/N 6876991 and 6889320, with compliance to be achieved at the next turbine repair or overhaul, or by specified dates, 28 February 1990 and 28 February 1992 respectively. The obligations under this Act are clear: operators and maintainers of the specified turbine engines must ensure that the identified tie bolts are removed from service as per the directive. This involves either replacing the tie bolts during the next scheduled turbine repair or overhaul, or ensuring that the removal is completed by the deadlines provided. Failure to comply with these requirements could result in significant safety risks, as the directive is implemented to address fatigue cracking in the threaded area of the tie bolts, which could lead to the failure of the Gas Producer Rotor Assembly and potentially catastrophic damage to the aircraft. In terms of legal consequences, failure to comply with the provisions of this directive could result in severe penalties. Although the specific penalties are not detailed in the excerpt, non-compliance with aviation safety regulations generally carries significant civil or criminal penalties. These could include fines, suspension or revocation of operational licenses, and possible criminal charges for negligence. The seriousness of the potential consequences underscores the importance of adhering to the requirements outlined in the directive to ensure the safety of the aircraft and its occupants. Moreover, the directive notes that the compliance schedule has been updated to include the new P/N 6843388 tie bolt assembly and reflects the revised requirement documents. This amendment aims to mitigate the risk of tie bolt failure by introducing new, stronger bolts. The directive's background highlights the critical nature of the issue, as failure of the tie bolts could result in the Gas Producer Rotor Assembly failing, leading to turbine wheel fragments being ejected from the engine. Such an event could severely damage the aircraft, posing a significant risk to flight safety. Overall, the directive is a crucial safety measure designed to prevent potential catastrophic failures by ensuring that older, potentially compromised tie bolts are replaced with new, improved ones. Compliance with this directive is mandatory, and failure to adhere to the stipulated requirements could lead to severe civil or criminal repercussions, highlighting the importance of stringent adherence to aviation safety regulations.