AD/HS 125/138 - Wing Leading Edge Corrosion

Overview

The Civil Aviation Regulations 1998 (F2006B10418) were enacted by the Commonwealth of Australia to establish and maintain a comprehensive regulatory framework governing civil aviation safety. Within this extensive regulatory structure, Part 39 - 105 Civil Aviation Safety Authority Schedule of Airworthiness Directives includes specific directives aimed at ensuring the ongoing airworthiness of aircraft types, such as the British Aerospace BAe 125 Series Aeroplanes. One such directive, AD/HS 125/138, addresses the issue of wing leading edge corrosion on Model 125 Series 800 and 1000 aircraft. This directive mandates corrective actions in accordance with British Aerospace Mandatory Service Bulletin 57-77 to mitigate the risk of exfoliation corrosion at the wing leading edge section, particularly at the interface with the TKS panels, caused by moisture ingress through sealant gaps that develop during service. The directive ensures compliance within two years of the aircraft's manufacture or before 31 May 1994, whichever is later, aiming to enhance the safety and reliability of these aircraft in service.

Scope and Application

The Civil Aviation Regulations 1998, as amended, apply to all entities and persons involved in the operation of British Aerospace BAe 125 Series 800 and 1000 aircraft that have not yet undergone modification 253538A or B, which addresses improved corrosion protection. This regulation is part of the broader civil aviation safety directives under the oversight of the Civil Aviation Safety Authority and applies across the Commonwealth of Australia. The regulation mandates compliance with British Aerospace Mandatory Service Bulletin 57-77, which aligns with the UK Civil Aviation Authority's AD 016-05-93, to address the identified issue of exfoliation corrosion in the wing leading edge section at the interface with the TKS panels. This corrosion is attributed to moisture ingress through gaps in the sealant that develop during aircraft service. Compliance with this directive must be achieved within two years from the date of the aircraft's manufacture or before 31 May 1994, whichever is the later date. The scope of this regulation is specific to the mentioned aircraft models and does not extend to other aircraft types or modifications that have already incorporated the required corrosion protection improvements.

Key Provisions

The Civil Aviation Regulations 1998, specifically under Part 39 - 105, contain the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives. Of particular note is AD/HS 125/138 concerning the British Aerospace BAe 125 Series aeroplanes and addressing the issue of wing leading edge corrosion (Section 9/93). This directive applies to Model 125 Series 800 and 1000 aircraft that were manufactured before the modification numbers 253538A or B, which introduced improved corrosion protection (Section 9/93). These regulations mandate that actions be taken in accordance with British Aerospace Mandatory Service Bulletin 57-77. It is worth noting that this directive references the UK Civil Aviation Authority AD 016-05-93 for further guidance (Section 9/93). The directive requires compliance within two years of the aircraft's manufacture or by 31 May 1994, whichever is the later date. This timeline is intended to ensure that any identified issues are addressed before they can lead to further degradation of the aircraft’s structural integrity. The obligations imposed by this directive on the parties or entities it governs include the requirement to inspect and, if necessary, repair or replace the wing leading edge sections to prevent exfoliation corrosion. This involves identifying any gaps in the sealant that allow moisture ingress, which is a known cause of corrosion in this area. Operators of the BAe 125 Series 800 and 1000 aircraft must ensure that these inspections and any required repairs are carried out in a timely manner to maintain the airworthiness of the aircraft. Failure to comply with these airworthiness directives can lead to significant consequences. While the specific penalties are not detailed in the text provided, under the Civil Aviation Act 1988, breaches of airworthiness regulations can result in both civil and criminal penalties. Civil penalties can include fines, while criminal penalties can include imprisonment, reflecting the serious nature of ensuring the safety and airworthiness of aircraft. The specific maximum penalties would depend on the nature and severity of the breach, as outlined in the broader regulatory framework.