AD/HS 748/9 - Auto Feather Micro Switch Operating Levers

Overview

The Civil Aviation Regulations 1998, under Part 39 – 105, includes the Civil Aviation Safety Authority Schedule of Airworthiness Directives, specifically pertaining to the British Aerospace (Hawker Siddeley) HS 748 Series Aeroplanes. This legislative instrument, F2006B10574, was enacted to address the problem of cracks in the fork end of the levers which actuate the auto feather inhibiting micro switches in HS 748 series aircraft. These cracks, if left unaddressed, could lead to a failure in the propeller auto feathering mechanism in the event of an engine failure, thereby posing a significant safety risk. The policy objective is to ensure the continued airworthiness and safety of the HS 748 series aircraft by mandating specific actions as outlined in the legislation, including compliance with the requirements set out in Revision 4 of Jetstream Aircraft Ltd Mandatory SB HS748-76-15, and referencing UK CAA AD 0132. The Civil Aviation Regulations 1998 were enacted by the Australian Parliament to regulate civil aviation safety and to establish standards and requirements for aircraft and aviation operations within Australia. The legislative instrument in question, F2006B10574, was introduced by the Civil Aviation Safety Authority as part of its ongoing efforts to maintain and enhance aviation safety standards. The requirement to act in accordance with the specified mandatory service bulletin and to comply with the inspection intervals ensures that identified safety issues are systematically addressed, thereby mitigating potential hazards to flight safety.

Scope and Application

The Civil Aviation Safety Authority Schedule of Airworthiness Directives, specifically AD/HS 748/9 concerning British Aerospace (Hawker Siddeley) HS 748 Series Aeroplanes, applies to all HS 748 series aircraft that do not yet incorporate modification 6909. This legislation mandates compliance with Revision 4 of Jetstream Aircraft Ltd Mandatory Service Bulletin HS748-76-15 and references UK CAA AD 0132. The requirement is that the action specified in the service bulletin must be taken within 1000 hours of time in service from 5 January 1995, and subsequent reinspections must occur at intervals not exceeding 1000 hours until modification 6909 is incorporated. The directive addresses the issue of cracks found in the fork end of the levers that actuate the auto feather inhibiting micro switches on the engine sub frame. If such a crack leads to a failed micro switch followed by an engine failure, the propeller may not auto feather, hence the necessity for these specific safety measures. The regulation is enforced under the Commonwealth of Australia and extends nationally, applying to all relevant aircraft within Australia’s jurisdiction.

Key Provisions

The Civil Aviation Regulations 1998 (CAR) Part 39 - 105 contains the Schedule of Airworthiness Directives (ADs), which includes AD/HS 748/9 pertaining to British Aerospace (Hawker Siddeley) HS 748 series aeroplanes. Specifically, this directive addresses the auto feather micro switch operating levers, as outlined in Revision 4 of Jetstream Aircraft Ltd Mandatory Service Bulletin HS748-76-15. This directive applies to all HS 748 series aircraft that do not yet have modification 6909 incorporated. The requirement is that action must be taken in accordance with the specified revision of the service bulletin. It is noted that this directive aligns with UK CAA AD 0132. The directive mandates that compliance must be achieved within 1000 hours of time in service from 5 January 1995. Following this initial compliance, a reinspection must be conducted at intervals not exceeding 1000 hours of time in service until modification 6909 is incorporated. The obligations imposed by AD/HS 748/9 require the operators of the affected HS 748 series aircraft to address the reported issue of cracks in the fork end of the auto feather micro switch operating levers. These levers are critical as they are responsible for activating the micro switches that inhibit auto feathering in the event of an engine failure. The operator must ensure that the action required by Revision 4 of the service bulletin is completed and that the aircraft is brought into compliance. This involves inspecting the levers for any cracks, and if necessary, repairing or replacing them to prevent failure of the micro switches. Additionally, operators must schedule regular reinspections to ensure ongoing airworthiness and safety of the aircraft. Failure to comply with AD/HS 748/9 may result in serious safety implications, as a malfunction in the auto feather system can lead to a critical engine failure scenario. The Civil Aviation Safety Authority (CASA) enforces strict compliance with ADs, and any breach of this directive can lead to enforcement actions. Penalties for non-compliance can include fines and other sanctions as stipulated in the Civil Aviation Act 1988. The maximum penalties can be significant, reflecting the importance of adhering to airworthiness directives to ensure the safety of flight operations. It is crucial for operators to maintain strict adherence to these regulations to avoid any legal or safety repercussions.