AD/B737/39 - APU Fire Detector Element

Overview

The Civil Aviation Regulations 1998, under the authority of the Civil Aviation Act 1988, introduced a comprehensive framework to regulate and ensure the safety of civil aviation within Australia. One such regulatory measure is the Airworthiness Directive AD/B737/39, specifically addressing the installation and inspection of fire detection systems in Boeing 737 series aeroplanes. This directive was enacted to address a critical safety issue identified with the Auxiliary Power Unit (APU) fire detection systems on certain Boeing 737 models, ensuring that the appropriate Walter Kidde fire detector elements are correctly installed and functioning as intended. The objective of this legislation is to mitigate the risk of fire in the APU compartment by ensuring the correct fire detection system components are in place, thereby enhancing the overall safety and reliability of air travel. The Civil Aviation Safety Authority, as part of the Australian Government's Department of Infrastructure and Transport, issued this directive to comply with international safety standards and to respond to specific incidents where incorrect fire detection elements were installed, potentially compromising the safety of the aircraft. The policy objective is to maintain and improve the safety of civil aviation by ensuring that all applicable aircraft meet stringent airworthiness standards, thereby protecting passengers, crew, and the general public.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105 under the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, pertains to the Boeing 737 series aeroplanes and mandates a particular safety directive concerning the Auxiliary Power Unit (APU) fire detector element. This regulation applies to all Boeing 737 series aircraft that are equipped with Walter Kidde APU fire detection systems. The directive requires an inspection to confirm that the correct Walter Kidde fire detector element is installed within the APU compartment, with the inspection potentially being conducted by visual confirmation through the APU cooling air exhaust outlet. The specific fire detector element must be identified by its perforated shield, and if the shield is not visible, the lower APU shroud must be opened to verify the installation of the correct part numbers for different 737 series models. This regulation is applicable regardless of the location where the aircraft are registered or operated within Australia, as it is a Commonwealth regulation enforced by CASA. There are no exclusions or exemptions specified within the directive itself, though the application may be extended or restricted through subordinate instruments as determined by CASA.

Key Provisions

The Civil Aviation Regulations 1998, specifically in Part 39 under Subpart 105, contain the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, which include AD/B737/39 concerning Boeing 737 series aeroplanes and their APU fire detection systems. This directive applies to all model 737 series aircraft equipped with Walter Kidde auxiliary power unit (APU) fire detection systems (s 39.105). The main requirement outlined in this directive is to inspect the APU compartment to ensure a Walter Kidde fire detector element is installed. This inspection can be performed by viewing through the APU cooling air exhaust outlet. For 737-300 and 737-400 series aircraft, the specific fire detector element must be Boeing P/N 10-61096-316 / Walter Kidde P/N 894481, while for 737-100 and 737-200 series aircraft, it must be Boeing P/N 10-62061-6 or P/N 10-61096-116 (s 39.105(1)). If the perforated shield protecting the Walter Kidde element is not visible, the lower APU shroud must be opened to verify the correct installation. Compliance with this directive is mandatory for aircraft prior to 19 July 1990. It is essential that airlines and operators of these aircraft ensure that the specified fire detector elements are correctly installed and visible as required. This involves conducting thorough inspections and verifying the presence and correct type of fire detector element in the APU compartment. Failure to comply with these requirements could result in significant safety risks, as highlighted by Boeing's advisory that several aircraft had incorrect Systron-Donner fire detector elements installed instead of the correct Walter Kidde elements. Such non-compliance could lead to a false positive flight deck fire detector test, while the actual fire detection system remains ineffective. The Civil Aviation Regulations impose clear obligations on the operators of Boeing 737 series aircraft to adhere to the specified airworthiness directives. These obligations include conducting the required inspections and verifying the correct installation of the Walter Kidde fire detector element in the APU compartment. Operators must ensure that the correct part numbers are installed and visible as per the directive. Non-compliance with these directives can result in serious safety implications and potential regulatory action. It is imperative that operators maintain accurate records of all inspections and any corrective actions taken to ensure ongoing compliance. Any breach of the provisions under AD/B737/39 can lead to civil and criminal consequences. Failure to comply with the airworthiness directives can result in penalties imposed by CASA. The specific penalties are not detailed in the provided text, but they typically include fines and potential grounding of the non-compliant aircraft until corrective actions are taken. In severe cases, persistent non-compliance could lead to more stringent penalties, including revocation of the aircraft's airworthiness certificate. Ensuring adherence to these directives is crucial for maintaining the safety and airworthiness of the aircraft in operation.