AD/FU24/44 - Part 1. Wing Spar Modification, and Part 2. Wing Spar Inspection

Overview

The Civil Aviation Regulations 1998, amended by the Civil Aviation (Airworthiness Directives) Notice 2006, was enacted to address specific safety concerns associated with certain aircraft models, particularly those used in agricultural operations. The problem this legislation aimed to address was the identification and mitigation of structural integrity issues in the wing spars of agricultural aeroplanes, which posed significant safety risks if left unaddressed. The objective of this directive, as outlined in the legislation, is to ensure the continued airworthiness of these aircraft by mandating specific modifications and inspections to enhance safety. The authority responsible for enacting this legislation is the Commonwealth of Australia, through the Civil Aviation Safety Authority, which oversees the implementation and compliance of these airworthiness directives.

Scope and Application

The Civil Aviation Regulations 1998, under the jurisdiction of the Commonwealth of Australia, specifically address airworthiness directives through Part 39 - 105. These regulations apply to all models within the agricultural category and to those aircraft that were previously used in agricultural operations, excluding those that have incorporated spar steel doublers in accordance with Air Parts Service Bulletin No. AP.55 Part B. The scope of the legislation mandates two primary actions: the modification of the centre-wing main spar lower cap in accordance with Air Parts Service Bulletin No. AP.59 and the inspection of the centre-wing main spar lower cap for any signs of cracking. This inspection must be thorough, extending to areas accessible after removing components such as the main beam slot fairing, leading edge fuel tanks, and access panels. Furthermore, the regulations provide for alternative inspection methods such as radiographic techniques, contingent on their ability to detect complete failures of the spar cap members. Compliance with these directives is time-sensitive, with specific timelines and intervals prescribed for inspections and modifications based on the total time in service of the aircraft.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, establish Airworthiness Directives for the FU 24 Series Aeroplanes manufactured by Airparts (NZ) Ltd. Two main sections are pertinent here. Part 1 requires a modification to the centre-wing main spar lower cap as per Air Parts Service Bulletin No. AP.59 (Section 1). Part 2 mandates visual inspections for cracking of the centre-wing main spar lower cap, inspection of the spar cap members using a borescope, and a visual and dye penetrant inspection of the outer and centre-wing main spar lower attachment fittings (Section 2). These directives apply to all models in the agricultural category and those previously used in agricultural operations, except for aircraft with spar steel doublers as per Air Parts SB No. AP.55 Part B. The obligations under these provisions are stringent. For aircraft in the agricultural category, the centre-wing main spar lower cap must be modified according to the specifications in Air Parts Service Bulletin No. AP.59 within 1000 hours of service after 31 March 1972. For aircraft previously used in agricultural operations but no longer in that category, the Civil Aviation Safety Authority (CASA) must be consulted to establish the appropriate inspection and modification requirements. Visual inspections must be thorough, with special attention given to areas adjacent to fastener holes and changes in section. Additionally, inspections using a borescope or an alternative radiographic technique must be conducted to detect major cracks or failures in the spar cap members. The outer and centre-wing main spar lower attachment fittings must also be inspected visually and using dye penetrant techniques. Failure to comply with these directives can result in significant consequences. Although the Civil Aviation Regulations do not explicitly outline penalties, non-compliance with Airworthiness Directives can lead to enforcement actions by CASA. These actions can include grounding of the aircraft, fines, and other regulatory penalties. The exact penalties depend on the severity and frequency of the non-compliance, but they can be substantial, reflecting the critical nature of ensuring airworthiness in aviation safety.