AD/B737/16 Amdt 3 - Engine Flameouts - Revised Operating Technique and Modifications

Overview

The Civil Aviation Regulations 1998, as amended by the Civil Aviation Safety Authority in 1992, introduced Airworthiness Directives (AD) to address safety concerns associated with Boeing 737-300 and 400 aircraft equipped with CFM56-3 series engines. This legislation was enacted by the Commonwealth of Australia to ensure compliance with international safety standards, particularly focusing on engine performance and safety in adverse weather conditions. The AD requires airlines to update their operational procedures and aircraft systems to mitigate the risk of engine flameouts during flights in or near moderate to heavy rain, hail, or sleet, and thunderstorm activity. The policy objective is to enhance flight safety by reducing the likelihood of engine failures in challenging weather conditions through revised operational techniques and mandatory engine modifications.

Scope and Application

The Civil Aviation Safety Authority Schedule of Airworthiness Directives under the Civil Aviation Regulations 1998 pertains to all Boeing 737-300 and 400 aircraft equipped with CFM56-3 series engines, targeting the aviation industry and specifically operators of these aircraft models. The directive mandates several amendments to ensure safety when operating in adverse weather conditions such as moderate to heavy rain, hail, or sleet, and thunderstorms. This includes specific operational procedures, modifications to the aircraft's Flight Manual, and the installation of placards on the instrument panel. Compliance with these directives is necessary for continued airworthiness and must be achieved by certain deadlines. The scope of the regulation is national, given its enforcement under the Commonwealth of Australia, and it extends to all operators within Australia. The directive allows for compliance through subordinate instruments, such as the insertion of specific amendments into the Flight Manual or Minimum Equipment List, pending formal updates. Certain modifications and compliance actions are mandated by specific dates, ensuring a structured timeline for implementation.

Key Provisions

The Civil Aviation Regulations 1998, under Part 39 - 105, include specific Airworthiness Directives (AD) aimed at ensuring the safety of Boeing 737 Series aeroplanes, particularly the 737-300 and 737-400 models equipped with CFM56-3 series engines. Section 105 mandates the incorporation of certain operational and maintenance requirements to mitigate risks associated with engine flameouts, especially during adverse weather conditions such as moderate to heavy rain, hail, or sleet. The AD requires the amendment of the aircraft Flight Manual to include specific operational instructions for such weather conditions, ensuring that the engine start switches are set to "FLIGHT," the minimum engine N1 is maintained at 45 per cent, and the auto-throttle must be turned off. Additionally, the directive advises avoiding flight operations within five miles of thunderstorm activity. The AD also imposes obligations on the operators of Boeing 737-300 and 737-400 aircraft to ensure compliance with these operational guidelines. Operators must update their Minimum Equipment List to include weather radar and both engine ignitors for operations in known or forecast rain, hail, or sleet. Furthermore, a placard must be installed on the instrument panel, clearly visible to the flight crew, indicating the need to maintain at least 45 per cent N1 when operating in or near moderate to heavy rain, hail, or sleet. These updates to the Flight Manual and Minimum Equipment List must be completed before further flights are undertaken after specified dates, ensuring that the aircraft are compliant with the latest safety standards. In addition to the operational and equipment requirements, the AD includes modifications to the engines to enhance their resistance to flameouts. For Boeing 737-300 series aircraft, these modifications, as detailed in Boeing Service Bulletin 737-77-1031, Revision 1, must be completed by 1 August 1994. Once these modifications are accomplished, the requirements of Parts 1, 2, and 3 of this AD no longer apply. For Boeing 737-400 series aircraft, the same modifications must be made, and any related flight compartment instrument panel placard may be removed once the modifications are completed. Failure to comply with these ADs can result in significant safety risks, including engine flameouts, and thus, strict adherence is mandatory.