Papers by Keyword: Widespread Fatigue Damage

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 overview of the fatigue and damage tolerance substantiation approach for a 70-90 seat class regional aircraft named Mitsubishi Regional Jet, which is now under development by Mitsubishi Aircraft Corporation, is presented. To comply with the new regulatory requirement for prevention from widespread fatigue damage, full-scale airplane fatigue test will be performed with simulating actual airplane structural configuration and typical loading spectra expected in service. In addition to widespread fatigue damage, damage tolerance evaluations assuming manufacturing defect or in-service damage are being performed. Hundreds of structural tests from coupon level to sub-component level are to be used to verify the material properties and analysis methodology.

Abstract: The paper highlights key questions in ensuring safe operation of aging civil\transport aircraft in Russia. Presented is the analysis of current requirements to fatigue, fail-safe and damage tolerance for transport aircraft structures stated in FARs, Advisory Circulars (UAS) and Russian Airworthiness Regulations\ AR IAC Aviation Regulations. The paper gives the design goals and actual service life values\ service years of aging aircraft fleet and data on full-scaled fatigue tests, together with methods and approaches to ensure safe operation of aircraft structures in case of multiple site damages, corrosion and materials degradation for Russian aging fleet.

Abstract: Widespread Fatigue Damage (WFD) issue is a major threat to the structural integrity of the aging aircrafts, So WFD assessment is a key measurement and necessary task to ensure the continuing airworthiness. A methodology using probabilistic framework to assess WFD was developed. The major feature of this method is that a stochastic process which is introduced to crack initiation and crack growth as well as yield stress and fracture toughness. Stress Intensity Factor (SIF) was incrementally calculated using Finite Element Method (FEM). Numerical studies were performed for panels with five holes using Monte Carlo Simulation (MCS). The WFD Average Behavior, include inspection, monitoring and repair period, was presented, and the convergence of the MCS was also discussed. The effectiveness of this methodology was verified by comparing the experimental data. This approach simulated and evaluated the WFD behavior and got the relative statistic data, which provided a practical engineering method for WFD evaluation.

Abstract: Widespread fatigue damage (WFD) is an important concern of aging aircrafts. Residual strength of stiffened panels with widespread fatigue damage was evaluated by an engineering approach and a finite element method respectively. Nine stiffened panels with three types of damage were tested for their residual strength. The predictions are in good agreement with the experiment results and it is shown the methods could be used in an engineering practice for the residual strength evaluation with the acceptable accuracy. It can be seen from this research that WFD could result in significantly reduction in the residual strength of stiffened panels.

Abstract: Widespread Fatigue Damage (WFD) is a technical expression used in the certification of aircraft. The paper presents a set of issues which may influence the probability that a structural item exhibits WFD. The paper mainly follows the line of a stochastic approach to these subjects, and includes the influence of realistic parameters - like manufacturing - and tries to assess what may be the impact of new technologies.