AD/DHC-6/24 Amdt 3 - Elevator and Tailplane

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 105, were enacted to ensure the safety and airworthiness of aircraft operating within Australia. This legislative instrument addresses issues pertaining to the maintenance and modifications of specific aircraft models, particularly the DHC-6 (Twin Otter) Series Aeroplanes. The regulations aim to mitigate risks associated with structural integrity and operational safety by issuing Airworthiness Directives (ADs). These ADs are designed to enforce compliance with necessary modifications and inspections to prevent incidents related to known structural failures. The regulations were enacted by the Australian Government and are administered by the Civil Aviation Safety Authority (CASA), ensuring that all aircraft meet stringent safety standards. The overarching policy objective of these regulations is to enhance the safety and reliability of civil aviation through proactive and prescriptive maintenance and modification directives. This particular amendment to the Airworthiness Directive AD/DHC-6/24 focuses on addressing the specific issues of cracking, galling, and enlargement of bolt holes in the elevator outboard hinge assemblies, as well as lug failure on the tailplane fitting and elongated holes in the elevator attachment fitting. The amendment aims to ensure that these critical components are inspected and modified as required to prevent potential failures. Compliance with this directive is mandatory, with specific timelines provided for inspections and modifications, ensuring that all DHC-6 aircraft meet the necessary safety standards. This legislative instrument is effective from 18 August 1994, aligning with international safety standards and ensuring consistent regulatory practices across jurisdictions.

Scope and Application

The Civil Aviation Regulations 1998, specifically PART 39 - 105, mandates safety directives for aircraft such as the DHC-6 (Twin Otter) series aeroplanes through the Civil Aviation Safety Authority. This particular legislation applies to all model DHC-6 aircraft, ensuring compliance with safety directives to maintain airworthiness. The geographic reach of this regulation is national, as it pertains to all operations within the Commonwealth of Australia. It mandates specific actions including inspections and modifications to the elevator and tailplane as per the de Havilland Service Bulletin 6/421 Revision B. Compliance must be achieved within 50 hours of time in service after 31 August 1983, and subsequently at intervals not exceeding 1200 hours of time in service, or by 31 March 1995 if not already accomplished. This Act is supported by subordinate instruments that ensure its effective implementation, while also aligning with the Transport Canada AD CF-83-11R1.

Key Provisions

The Civil Aviation Regulations 1998, particularly Part 39, Section 105, which pertains to the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives for DHC-6 (Twin Otter) Series Aeroplanes, outlines specific requirements for maintaining the airworthiness of these aircraft. Section 105 AD/DHC-6/24 Amendment 3 details the necessity for operators to conduct inspections and modifications to the elevator and tailplane components of all model DHC-6 aircraft (Section 105 AD/DHC-6/24). The primary requirement is to perform inspections as outlined in de Havilland Service Bulletin 6/421 Revision B and to install Modification 6/1799, also detailed in the same service bulletin. It is noted that the incorporation of this modification provides a terminating action for the ongoing inspection requirements specified by this directive. Operators of DHC-6 aircraft must adhere to stringent compliance schedules. Specifically, the inspections and modifications must be completed within 50 hours of time in service after 31 August 1983, and then at intervals not exceeding 1200 hours of time in service (Section 105 AD/DHC-6/24). Furthermore, if the modifications have not been completed, they must be carried out before 31 March 1995. This directive also recognises that compliance with the previous version of the directive remains valid as Requirement 1, while Requirement 2 introduces new modifications. The amendment is effective from 18 August 1994, and it aims to address reported issues such as cracking, galling, and enlargement of bolt holes in the elevator outboard hinge assemblies, as well as lug failures and elongated holes in the elevator attachment fitting. Failing to comply with the provisions set out in the Civil Aviation Regulations 1998 can lead to serious consequences. Although the specific penalties for non-compliance are not detailed within the text of this particular directive, general provisions within the Civil Aviation Act 1988 outline that non-compliance with airworthiness directives can result in both civil and criminal penalties. Civil penalties may include fines, while criminal penalties can extend to imprisonment, reflecting the importance of adhering to these safety measures to ensure the continued safe operation of DHC-6 aircraft. Operators must therefore ensure that all inspections and modifications are carried out in a timely and compliant manner to avoid any legal repercussions.