AD/HS 125/158 - APU Fuel Feed Hose Assemblies

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 105, contains a schedule of airworthiness directives intended to ensure the safety of aircraft operations in Australia. One such directive, AD/HS 125/158, pertains to British Aerospace BAe 125 Series Aeroplanes and specifically addresses issues with the Auxiliary Power Unit (APU) fuel feed hose assemblies. This directive was introduced to address the problem of heat damage to APU feed hoses due to impingement of hot bleed air, which could potentially result in an in-flight fire. The Civil Aviation Safety Authority (CASA), under the authority of the Australian Government, enacted this directive to mitigate safety risks associated with these aircraft models. The policy objective is to ensure that the specified maintenance actions are implemented to prevent potential hazards and maintain airworthiness standards. The directive requires inspections and replacements of the APU fuel feed hose assemblies on BAe 125-800A and Hawker 800 series aircraft incorporating Mod 259404B. Compliance must be achieved within specific timeframes: inspections must be completed within 75 days of the directive's effective date, and replacements must be carried out within 200 flight hours of the effective date. The directive became effective on 29 January 1998, emphasising the urgency and importance of these safety measures.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, governs the airworthiness of aircraft operating within Australian airspace, and this regulation applies directly to the BAe 125-800A and Hawker 800 series aircraft that have incorporated the Mod 259404B, which introduced the Turbomach Auxiliary Power Unit (APU). The regulation mandates a comprehensive inspection of the APU fuel feed hose assembly as per Hawker Raytheon Corporate Jets Mandatory Inspection Service Bulletin SB 49-45, referencing FAA AD 97 21-03. Furthermore, the vinyl conduit of the APU fuel feed hose assembly must be replaced with a convoluted PTFE tube according to Hawker Service Bulletin SB.49-47-25A825A (Modification No. 25A825A). The compliance requirements state that the inspection must be completed within 75 days from the effective date of the directive, 29 January 1998, while the replacement must occur within 200 flight hours from the same date. Compliance with the replacement requirement also terminates the necessity for the inspection. This directive is integral to ensuring the safety of the aircraft by preventing potential in-flight fires due to complete failure of the APU hoses, which could occur from heat damage caused by impingement of hot bleed air leaking from adjacent pneumatic components.

Key Provisions

The Civil Aviation Regulations 1998, Part 39 - 105, specifically within the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, contains the directive AD/HS 125/158, which pertains to British Aerospace BAe 125 Series Aeroplanes, focusing on APU fuel feed hose assemblies. This directive applies to all BAe 125-800A and Hawker 800 series aircraft that incorporate modification 259404B, which introduces the Turbomach APU. The directive mandates two primary requirements: the inspection of the APU fuel feed hose assembly in accordance with Hawker Raytheon Corporate Jets Mandatory Inspection Service Bulletin SB 49-45, and the replacement of the vinyl conduit on the APU fuel feed hose assembly with convoluted PTFE tube in accordance with Hawker Service Bulletin SB.49-47-25A825A (Modification No. 25A825A). These requirements are essential to address the risk of heat damage and potential complete failure of the APU hoses, which could lead to in-flight fires. The obligations imposed by this directive are quite clear and must be adhered to strictly. Operators of the affected aircraft are required to conduct the specified inspection within 75 days of the effective date of this directive, which is 29 January 1998. Additionally, the replacement of the vinyl conduit with convoluted PTFE tube must be completed within 200 flight hours of the effective date of the directive. It is worth noting that compliance with the second requirement serves as terminating action for the inspection stipulated in the first requirement. Failure to comply with these requirements could compromise the airworthiness and safety of the aircraft. Breaches of the provisions set forth in AD/HS 125/158 can result in serious consequences. The regulations do not explicitly outline the penalties for non-compliance in this particular directive; however, under the broader Civil Aviation Act 1988 and Civil Aviation Regulations 1998, failure to adhere to airworthiness directives can lead to substantial penalties. Civil penalties may include fines, and in severe cases, criminal charges can be pursued, which may result in imprisonment. Additionally, non-compliance could lead to the grounding of the affected aircraft until the necessary inspections and modifications are completed, potentially causing significant operational disruptions and financial losses. Therefore, it is imperative for operators to ensure strict adherence to these directives to maintain the safety and airworthiness of their aircraft.