Overview

The Airworthiness Directive AD/AL 250/83 was enacted in 2004 by the Civil Aviation Safety Authority (CASA) to address a critical safety concern related to the third-stage turbine wheels of Allison Turbine Engines, specifically the 250 series models 250-C28, -C28B, and -C28C. This directive was issued in response to reports of failures in the turbine wheels, which could lead to significant safety hazards such as loss of engine power and uncommanded shutdowns. The objective of this directive is to ensure the continued airworthiness of affected aircraft by mandating specific actions to replace or prohibit the use of certain turbine wheels to mitigate the identified risk. This legislative instrument is a crucial step in ensuring the safety and reliability of aviation operations within Australia.

Scope and Application

The Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA) under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998 pertains specifically to Rolls-Royce Corporation's (formerly Allison Engine Company) models 250-C28, -C28B, and -C28C turboshaft engines equipped with third-stage turbine wheels, part number 6899383, that are listed by serial number in Table 1 of this directive. This AD mandates the replacement of specific third-stage turbine wheels to prevent potential blade and shroud failures, which could lead to loss of power and uncommanded engine shutdown. The directive applies to these specific engine models installed on various helicopters, such as the Bell Helicopter Textron 206L-1 and Eurocopter Deutschland BO 105 LS A-1, among others. The directive is effective from 30 September 2004, with compliance timelines varying based on the operating hours of the turbine wheels since they were new. This AD is part of the Commonwealth's legislative framework, as evidenced by its notification in the Commonwealth of Australia Gazette on 8 September 2004.

Key Provisions

The main operative sections of the Airworthiness Directive (AD) require the replacement or prohibition of certain third-stage turbine wheels in specific Rolls-Royce Corporation (formerly Allison Engine Company) turboshaft engines. Specifically, section 1 requires the replacement of existing third-stage turbine wheels listed in Table 1 of this Directive with a turbine wheel not listed in Table 1 (section 1(a)). Section 2 mandates that no third-stage turbine wheels listed in Table 1 should be installed into any engine (section 1(b)). The compliance timeline for these actions is specified in section 3, with different deadlines depending on the operating hours of the turbine wheels since new (TSN) on the effective date of this Directive. The obligations imposed by the AD on the parties or entities it governs include ensuring that only compliant turbine wheels are installed in the specified engines. For turbine wheels with less than 250 operating hours TSN on the effective date, the replacement must occur before accumulating 300 operating hours TSN (section 3(a)). For turbine wheels with 250 or more operating hours TSN on the effective date, the replacement must happen before accumulating an additional 50 operating hours (section 3(b)). Additionally, the prohibition on installing turbine wheels listed in Table 1 into any engine takes effect immediately from the effective date of the AD (section 3(c)). Failure to comply with the AD can result in serious consequences, including potential safety hazards such as loss of power and uncommanded engine shutdown. While the AD itself does not specify penalties, non-compliance with ADs can lead to enforcement actions by the Civil Aviation Safety Authority (CASA). These actions may include fines, orders for corrective action, and in severe cases, grounding of the aircraft until compliance is achieved. The exact penalties are determined by CASA in accordance with applicable aviation regulations and may vary depending on the severity and circumstances of the non-compliance.