Overview

The Civil Aviation Regulations 1998, amended by F2006B02152, introduced an Airworthiness Directive aimed at addressing safety issues specifically concerning the Twin Commander series aeroplanes, notably models 500, 600, and 700. This legislative instrument was enacted by the Civil Aviation Safety Authority (CASA) under the authority of the Commonwealth of Australia to enhance aviation safety standards. The problem it sought to resolve included instances where fatigue cracks, exacerbated by the interaction between the firewall and the main spar lower cap at wing station 96, led to catastrophic failures. The directive mandates thorough inspections and corrective actions to prevent similar incidents in the future. The overarching policy objective is to ensure the continued airworthiness of affected aircraft by identifying and mitigating potential structural failures.

Scope and Application

The Civil Aviation Safety Authority (CASA) has issued an Airworthiness Directive under the Civil Aviation Regulations 1998, specifically targeting Twin Commander (Gulfstream/Rockwell/Aerocommander 500, 600 and 700) series aeroplanes. The directive applies to aircraft with specified model serial numbers and mandates inspections to address the issue of fatigue cracks aggravated by fretting on the forward flange of the main spar lower cap. This directive applies to all aircraft within the specified serial numbers, irrespective of prior compliance with other service bulletins, aiming to ensure the airworthiness of these aircraft. The directive applies nationally within Australia, and compliance is mandatory for all operators of the affected aircraft. There are no stated exclusions or exemptions within the text provided; however, the directive allows for certain conditions under which aircraft that have previously complied with certain service bulletins may have adjusted compliance timelines. The directive is reinforced by the requirement for operators to visually inspect and repair as necessary, ensuring that all aircraft meet the specified safety standards.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, mandates the compliance with Airworthiness Directives (AD) to ensure the safety of aircraft. In this instance, AD/AC/91 pertains to the Twin Commander (Gulfstream/Rockwell/Aerocommander 500, 600, and 700) series aeroplanes, with a focus on the main spar lower cap at wing station 96. The directive is applicable to specific model serial numbers, requiring a series of inspections and maintenance actions (Reg 39.105(1)). Operators of the affected aircraft must conduct a thorough visual inspection for interference between the forward flange of the main spar lower cap and the outboard flange of the firewall assembly, as detailed in Twin Commander Service Bulletin 212. This inspection must be performed in accordance with the specified accomplishment instructions. Additionally, operators are required to remove a section of the wing to nacelle fairing at wing station 96, and inspect for corrosion or other surface damage in the radius area. If any damage is found, it must be blended and polished, and any bare areas must be repainted. The main spar lower cap must also be inspected for cracks using Fluorescent Dye Penetrant, and any necessary repairs must be made (Reg 39.105(2)-(3)). The directive stipulates that all inspections and maintenance actions must be completed within specific timeframes. For aircraft that have not previously complied with Part I of Twin Commander SB 212, the inspections must be conducted within 50 hours of time in service from 27 April 1995. For those that have complied with Part I before the directive was issued, the inspections must be conducted within 250 hours of time in service. If Parts I and II of Twin Commander SB 212 were complied with prior to the directive, operators must contact the Civil Aviation Safety Authority for further instructions (Reg 39.105(4)-(5)). Failure to comply with the AD/AC/91 requirements may result in significant civil and criminal penalties. The Civil Aviation Safety Authority has the authority to enforce compliance through legal action, which can include substantial fines and potential criminal charges for operators who neglect to adhere to the safety directives. The exact penalties are not specified in the legislative instrument but may vary based on the severity and frequency of non-compliance (Reg 39.105(6)).