An overview of the aircraft design and maintenance process is given with specific emphasis on the fatigue design as well as the phenomenon of the ageing aircraft observed over the life cycle. The different measures taken to guarantee structural integrity along the maintenance process are addressed. The impact of structural health monitoring as a means of possibly revolutionizing the current aircraft structural monitoring and design process is emphasized and comparison is made to jet engines and helicopters, where health monitoring has already found the respective breakthrough.
This paper details a new decision support that adds a proactive function to the actual line aircraft maintenance turn-around-time (TAT) process, where next-flight decisions are assisted by the health assessment function of the integrated vehicle health management (IVHM) of an aircraft. The 'operational risk assessment' concept appears an extended function supported on the IVHM information for calculating and evaluating the operational risk for aircraft and fleet operations. It creates or reshapes maintenance plans based on predictions of the future maintenance relevant events (e.g. component-degradation-driven repair or replacement events) and its impact on the operational planning of the aircraft/fleet. 'Operational risk assessment' makes it possible to turn the scheduled line maintenance into a proactively defined maintenance. The paper also illustrates the first step involved in this approach: 'condition view' function, which is responsible for the provision of the remaining useful life (RUL) prediction of a health managed component. This function provides the basis for the operational risk estimation on the aircraft in order to identify maintenance actions that can be deferred.
Since September 2006, an international Aerospace Industry Steering Committee was assembled at Stanford University. Since February 2009, the committee has been formally working on developing guidelines for validating, qualifying and certifying structural health monitoring systems. Working within the G-11 division of SAE International, the committee has compiled guidelines for civil transport aircraft. Some of these guidelines can be used for military applications. However, military guidelines are needed to address specific military considerations including concept of operations. The military guidelines should also cover the wider spectrum of military aircraft types and should focus on the key elements required for integrating structural health monitoring within military systems. Therefore, a G-11 Aerospace Industry Steering Committee Military Aircraft Working Group was formed to develop such guidelines. This article describes the motivation, rationale, scope, milestones and initial work of the Military Aircraft Working Group. The results of the guidelines will form the future framework for the military community.
Many service systems such as transportation and logistics systems provide multimodal services with various resources, where how a service is provided to customers including the resources assigned to the service is often designed in advance of the service operations. However, due to increasing dynamics and uncertainty in certain situations, the needs for quickly designing and deploying ad hoc service systems in response to urgent and unexpected events occurred during the service provision have become significant. Motivated by this, we present a structural and functional design that supports Ad Hoc Multimodal Service System (AHMSS) deployment with a focus on a structure of the system, constraints governing the decisions involved in the system, and functions required for the system operation. The proposed design solution provides the basis for developing a decision support system for AHMSS deployment.
Future health monitoring concepts in different fields of engineering require reliable fault detection to avoid unscheduled machine downtime. Diagnosis of electrical induction machines for industrial applications is widely discussed in literature. In aviation industry, this topic is still only rarely discussed. A common approach to health monitoring for electrical induction machines is to use Motor Current Signature Analysis (MCSA) based on a Fast Fourier Transform (FFT). Research results on this topic are available for comparatively large motors, where the power supply is typically based on 50Hz alternating current, which is the general power supply frequency for industrial applications. In this paper, transferability to airborne applications, where the power supply is 400Hz, is assessed. Three phase asynchronous motors are used to analyse detectability of different motor faults. The possibility to transfer fault detection results from 50Hz to 400Hz induction machines is the main question answered in this research work. 400Hz power supply frequency requires adjusted motor design, causing increased motor speed compared to 50Hz supply frequency. The motor used for experiments in this work is a 800W motor with 200V phase to phase power supply, powering an avionic fan. The fault cases to be examined are a bearing fault, a rotor unbalance, a stator winding fault, a broken rotor bar and a static air gap eccentricity. These are the most common faults in electrical induction machines which can cause machine downtime. The focus of the research work is the feasibility of the application of MCSA for small scale, high speed motor design, using the Fourier spectra of the current signal. Detectability is given for all but the bearing fault, although rotor unbalance can only be detected in case of severe damage level. Results obtained in the experiments are interpreted withrespect to the motor design. Physical interpretation are given in case the results differ from those found in literature for 50Hz electrical machines.
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