AD/GAF-N22/28 Amdt 4 - Horizontal Stabiliser and Trim Tab System

Overview

The Civil Aviation Regulations 1998, specifically within Part 39 - 105, addresses the safety and airworthiness of aircraft through the issuance of Airworthiness Directives by the Civil Aviation Safety Authority (CASA). The purpose of these regulations is to ensure that all aircraft meet the necessary safety standards to protect the public and maintain the integrity of the aviation industry. One such Airworthiness Directive, AD/GAF-N22/28 Amendment 4, pertains to the GAF N22 and N24 series aeroplanes, focusing on the horizontal stabiliser and trim tab system. This amendment was introduced to address a problem identified through an inflight incident that involved extreme vibration and subsequent loss of part of the horizontal stabiliser trim tab. The policy objective is to prevent similar incidents by mandating specific modifications and inspections, ensuring that all applicable aircraft meet the required safety standards. The enactment of this directive by CASA aims to rectify the identified safety gap by requiring modifications and inspections in accordance with specified service bulletins and revisions. This legislative instrument was established to ensure compliance with safety protocols, thereby reducing the risk of similar incidents in the future. The directive reflects CASA’s commitment to maintaining high safety standards within the Australian civil aviation sector, providing clear guidance for aircraft operators to follow in order to maintain airworthiness.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, pertain to the maintenance and safety of aircraft within Australia and are enforced by the Civil Aviation Safety Authority (CASA). This legislative instrument, in the form of an Airworthiness Directive (AD), applies to all N22 and N24 Series aeroplanes and mandates modifications and inspections to address a specific safety concern regarding the horizontal stabiliser and trim tab system. The directive ensures that any modifications must align with GAF SB NMD-55-12 (Mod. N439) and inspections must follow GAF SB NMD-55-5 Revision 4. Compliance is required immediately and at specific intervals: prior to the next maintenance inspection following 30 November 1986, and then at intervals not exceeding 110 hours of time in service. The directive's applicability has been extended through this amendment to include all N22 and N24 Series aeroplanes, reflecting an update in response to an incident where there was significant structural damage due to extreme vibration in the empennage area. This amendment, effective from 24 June 1993, incorporates changes from previous directives and service bulletins to ensure comprehensive safety measures are in place.

Key Provisions

The Civil Aviation Regulations 1998, specifically in PART 39 - 105, detail the requirements for airworthiness directives concerning the GAF N22 and N24 Series aeroplanes. In this context, AD/GAF-N22/28 Amendment 4 pertains to modifications and inspections of the horizontal stabiliser and trim tab system (s. 1). The directive applies to all N22 and N24 Series aeroplanes and mandates modifications in accordance with GAF SB NMD-55-12 (Modification N439) unless these have already been carried out (s. 1). Additionally, inspections must be conducted in accordance with GAF SB NMD-55-5 Revision 4 (s. 2). Compliance with these requirements must be met immediately, and before the next scheduled inspection for maintenance release after 30 November 1986, and then at intervals not exceeding 110 hours of time in service (s. 2). The obligations under this airworthiness directive are clear and non-negotiable. Operators of N22 and N24 Series aeroplanes must ensure that the specified modifications are implemented as per the GAF SB NMD-55-12 (Mod. N439) and that the inspections are carried out following GAF SB NMD-55-5 Revision 4. Failure to adhere to these directives could potentially lead to significant safety risks, given the background of an inflight incident involving extreme vibration and structural damage to the horizontal stabiliser trim tab (s. 1, s. 2). The directive explicitly states that compliance must be achieved without delay and before the next scheduled inspection, with ongoing inspections to occur at intervals not exceeding 110 hours (s. 2). Failure to comply with the provisions of AD/GAF-N22/28 Amendment 4 can result in severe consequences. The Civil Aviation Regulations 1998 do not explicitly outline specific penalties or consequences for non-compliance within the text of the directive itself. However, the overarching regulations of the Civil Aviation Act 1988 and associated regulations typically impose stringent penalties for non-compliance with airworthiness directives. Such penalties can include substantial fines, potential grounding of the aircraft, and other enforcement actions by the Civil Aviation Safety Authority. The severity of these penalties underscores the importance of strict adherence to the outlined modifications and inspection intervals to ensure the continued airworthiness and safety of the N22 and N24 Series aeroplanes.