Papers by Author: Adam Bowler

Abstract: The AP-3C Orion aircraft is the oldest aircraft in the Royal Australian Air Force (RAAF) inventory. The planned fleet withdrawal has been extended far beyond the original design service objective. Continued safe and effective operation has required the development of a robust ageing aircraft management approach. A fundamental aspect was supplementing the structural certification basis with appropriate standards in the form of fatigue management requirements from Federal Aviation Regulations (FAR) 25.571 and Federal Aviation Administration Advisory Circular (FAA AC) 120-93. To develop and underpin the ageing aircraft management plan and transition to the supplementary fatigue management standards, the RAAF collaborated with the Original Equipment Manufacturer, Lockheed Martin Aeronautics Company, the United States Navy (USN) and other operators to form the P-3C Service Life Assessment Program (SLAP). This program provided Full Scale Fatigue Test (FSFT) data, associated analyses and analysis tools to support management in accordance with FAR 25.571. An important element of the ageing aircraft management plan included the introduction of a rigorous Safety By Inspection (SBI) maintenance regime to assure structural airworthiness. FAA AC 120-93 requires assessment of structural repairs to determine revised fatigue management and inspection requirements. Often, this information is derived using tailored analysis tools and detailed models on a case-by-case basis. This approach is specialized, expensive and usually occurs after the repair has been designed and installed. To avoid these limitations, the AP-3C Repair Assessment Manual (RAM) was developed to provide the repair designer with a design handbook approach to fatigue analysis. In conjunction with some simple Finite Element (FE) models, the RAM supports complete repair analysis prior to an aircraft leaving the maintenance venue. This paper will present the history of the SBI program, the genesis of the RAM and actual examples of assessing structural repairs on the P-3 platform using the RAM.

Abstract: The basic concept of an Aircraft Stuctural Integrity Program is to ensure that airframes are adequately managed to ensure safe operation without catastrophic failure, to maximise fleet availibilty and to minimise cost of ownership. In managing these three aspects, a number of conventional and advanced technologies are being adopted and applied within the RAAF. Composites and bonding technology has been developed and transitioned onto various RAAF aircraft over many years in the form of Bonded Patch Repairs to airframe structures (wing and fuselage). Based upon conventional heat treatment behaviour of aluminium alloys, Retrogressive Re-Ageing technology is being transitioned to minimise stress corrosion cracking. From structural mechanics and FEA technologies, Geometric Shape Optimisation methods have been applied to minimise peak stress thresholds within aged airframe structures. To manage structural degredation (fatigue and corrosion) a number sensor-based monitors are being developed and applied on RAAF aircraft. Finally, using the reliability methodology, a proactive management program to assess the extent of corrosion degradation within a whole aircraft is being instituted. This methodology is being articulated through a new paradigm known as “Environmental Degradation Management System – Tool Box” (EDMS-TB). Within RAAF it can be demonstrated that candidate technologies which are adopted have direct and in-direct positive influences within ASIPs to address the key structural integrity parameters of Safety, Availability and Cost of Ownership.