AD/BN-2/45 Amdt 1 - Main Undercarriage Leg

Overview

The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority (CASA), provide a comprehensive framework for ensuring the safety of civil aviation within Australia. Among these regulations, Part 39 – 105, specifically addressing airworthiness directives, is essential in maintaining the structural integrity and operational safety of aircraft. One such directive, AD/BN-2/45 Amendment 1, pertains to the Pilatus Britten-Norman BN-2 Series Aeroplanes, focusing on the main undercarriage leg to address specific safety concerns identified by the manufacturer. This directive was enacted to mitigate the risk of centre torque link pin fractures caused by bending due to excessive accumulated wear clearances between the axle bracket, plunger tube, and gland bearing. The policy objective is to ensure that all model BN-2 aeroplanes undergo mandatory inspections and, if necessary, modifications to prevent potential failures, thereby safeguarding the safety of both crew and passengers. The directive requires compliance with specific inspection and maintenance protocols outlined in the manufacturer’s service bulletins, which are classified as mandatory by CASA. The inspections must be conducted within 100 hours after 31 August 1985 or at the next scheduled maintenance release, whichever is later. Subsequent inspections are mandated every 100 hours or 150 landings, whichever occurs first. Additionally, after implementing modifications, inspections for wear must occur every 500 hours of service. This proactive approach aims to identify and rectify potential issues before they compromise the aircraft's safety, thereby maintaining the high standards of safety and reliability expected in civil aviation.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, apply to all Pilatus Britten-Norman BN-2 series aeroplanes as outlined in the Schedule of Airworthiness Directives. This legislation is enforced by the Civil Aviation Safety Authority (CASA) and has a national reach across Australia, ensuring compliance with safety standards within the Commonwealth. The directive applies to all BN-2 aircraft models referenced in the requirement documents and mandates specific actions concerning the main undercarriage leg, including inspections and modifications to prevent fractures of the centre torque link pin due to wear. The requirement documents, including Britten Norman SB No. BN-2/SB.135, AP Precision Hydraulics S.B. No. 32-278, and AP Precision Hydraulics S.B. 32-307, detail the necessary actions and compliance schedules. Inspections must be carried out within 100 hours of service after 31 August 1985 or at the next scheduled maintenance release, with subsequent inspections every 100 hours or every 150 landings, whichever occurs first. Post-modification inspections must be conducted every 500 hours of service. The directive does not explicitly mention any exclusions, exemptions, or thresholds, but the mandatory classification of certain requirement documents underscores the critical nature of compliance for maintaining airworthiness.

Key Provisions

The Civil Aviation Regulations 1998, specifically under PART 39 - 105, detail a series of airworthiness directives aimed at ensuring the safety and compliance of aircraft within Australian airspace. One such directive, AD/BN-2/45, pertains to the Pilatus Britten-Norman BN-2 series aeroplanes, focusing on the main undercarriage leg. This directive was amended on 8 August 1985, as referenced in the legislative instrument F2006B04756. The directive mandates actions to address the issue of fractures in the centre torque link pin, which can occur due to bending caused by excessive accumulated wear clearances between the axle bracket, plunger tube, and gland bearing. This issue has been reported in two local operators who have experienced recent torque link pin failures. The main operative sections of this directive (AD/BN-2/45) require all BN-2 model aeroplanes, as specified in the Requirement Documents, to undergo specific inspections and modifications. The first requirement (section 1) necessitates an inspection according to the specifications in Britten Norman SB No. BN-2/SB.135 issue 2 and AP Precision Hydraulics S.B. No. 32-278 Rev. 1. This inspection must occur within 100 hours of time in service after 31 August 1985, or at the next scheduled inspection for maintenance release, whichever is later. The second requirement (section 2) mandates repeat inspections every 100 hours of time in service or every 150 landings, whichever comes first, following the initial inspection. The third requirement (section 3) involves inspecting for wear every 500 hours of time in service after the incorporation of the modification detailed in AP Precision Hydraulics S.B. 32-307. The obligations imposed by the Civil Aviation Regulations on the parties governed by AD/BN-2/45 are clear and stringent. Operators of BN-2 series aeroplanes must ensure that the specified inspections and modifications are conducted in accordance with the detailed requirements. Failure to comply with these directives can result in significant safety risks, as the directive is classified as "MANDATORY" by the Civil Aviation Authority (CAA). Operators must document and record all inspections and modifications as per the specified requirements to demonstrate compliance. Additionally, any modifications must be carried out by authorised personnel to ensure they meet the necessary standards. Non-compliance with the provisions of AD/BN-2/45 can lead to severe consequences. The CAA considers breaches of mandatory directives to be serious violations, potentially resulting in the suspension or revocation of the aircraft's certificate of airworthiness. This, in turn, can prevent the aircraft from being operated legally within Australian airspace. Furthermore, operators found in breach of these regulations may face penalties, including fines and legal action. While the specific maximum penalties are not detailed in the directive, they can be significant, reflecting the importance of adhering to airworthiness standards to ensure public safety.