Avionics are fundamental to the flight management and engine control of today's airplanes. With increasing functional complexity of onboard autonomous avionic systems, there is an increasing demand for system-level health assessment, fault diagnostics, and prognostics, especially to meet critical safety and mission requirements. This article presents the motivation for increased health management, diagnostics, and prognostics for avionics, and then provides a diagnostics and prognostics approach to assess avionics. Keywords: prognostics; diagnostics; health management; avionics; aerospace; electronics; reliability

Abstract Current aircraft life prediction methodologies do not take into account the effect that environmental degradation has on the structural integrity of a component. This has led to the setting of limits on the amount of damage, usually based on maintaining residual strength that can be present on a component. These arbitrary limits have caused a significant increase in the maintenance cost of aircraft, since components must undergo a repair procedure when the detected damage is above the preset limits. To better assess the state of an aircraft, sensors can be placed in areas known to be susceptible to environmental degradation, such as corrosion. These sensors can monitor the environment in the area of concern to determine if conditions are present to cause corrosion. Sensors can also be used to directly determine if corrosion damage is present on a particular component and to what level. However, procedures need to be developed to relate the parameters that are monitored by a particular sensor type to the life of the component. This may include the development of algorithms to relate the environmental parameters that favor the growth of corrosion to the corrosion damage present on the particular component.

Architectural heritage is a resource and a fundamental part of the cultural European background; it also causes concern due to the huge investment needed to maintain it, or even to repair it, after environmental injuries. Dynamic testing is a fundamental tool to perform a general, low-cost, recurring or continuous on-line survey on the structural whole body. A study on the Holy Shroud Chapel in Torino (Italy) is reported as a validation of the monitoring techniques adopted at present on ancient buildings, although the refinement of the model updating procedure is not yet concluded.

The reason for a certain amount of damage at the well-known national monument “Brandenburg gate” should be investigated and clarified. In order to get sufficient information of the current static and dynamic structural behavior, a modal analysis of the gate has been carried out. The impacts on the gate because of railroad and road traffic, construction work, and special events like the “love parade” have been measured and investigated by using a permanently operating monitoring system. With the help of modal analysis and results from the condition monitoring system, the reason for the damage could be identified and threshold values for further impact to the structure could be defined. The results of the investigation serve also as a basis for the development of the best technical and economical rehabilitation measures. Keywords: Brandenburg gate; vibration monitoring; modal analysis

Abstract A flight demonstration of a structural health monitoring (SHM) system for a bonded structural repair is described. Motivations for health monitoring of bonded repairs are presented, and the flight test of a health monitoring system for a bonded repair on a fighter airplane is described. Experience gained by fielding a laboratory‐level system is discussed.

Sensor systems should be designed and engineered according to generally binding standards and guidelines. The use of the new fiber-optic sensor (FOS) technology requires recommendations on how to design and apply a sensor system to solve a specific measurement task. At present, corresponding national or international standards and guidelines are being developed. When customers are interested in the use of FOS technology, a multitude of reliability-related aspects have to be considered. Guidelines help give the users confidence in this new technology if they are strictly observed during manufacturing of sensor system components, when the measurement systems are designed and sensor components are selected to solve a specific measurement task, during application and later on during operation of the sensor system. The article provides a survey on important aspects that have to be considered for the use of reliable and long-term stable SHM systems, reflects upon state of the art of standards and guidelines activities, besides summarizing validation aspects that have to be described in FOS guidelines. Important technical aspects that influence sensor characteristics and the accuracy, efficiency, and long-term integrity of a sensor system are exemplified for fiber-optic strain sensors. One test method to characterize strain transfer for applied sensor fibers is discussed. Keywords: standards; guidelines; fiber-optic sensor; reliability; measurement uncertainty

Abstract The concept of wireless sensor nodes and sensor networks has been widely investigated within the field of structural health monitoring (SHM). However, the ability to power sensors, onboard processing, and telemetry components is a significant challenge in many SHM applications. Several energy harvesting techniques, based on piezoelectric and thermoelectric materials, have been proposed and studied to solve such problems. This article summarizes recent advances and research issues in energy harvesting relevant to SHM applications. We also present a feasibility study for using radio frequency (RF) signals to wirelessly deliver energy to power sensing systems. The goal of this study is to provide a method for supplying power to a sensor node periodically so that the SHM system does not rely on an onboard power source.

Abstract The Vasco da Gama Bridge is a 17‐km crossing over the river Tagus in Lisbon that was constructed and opened to traffic on the occasion of the World Exhibition Expo'98. As part of the dynamic tests required at the commissioning stage, ambient and free vibration tests were developed on the five viaducts and on the main cable‐stayed part that form the bridge, with the purpose of assessing the most relevant dynamic parameters in order to validate design studies and verify the safety condition of the structure. Focusing on the main cable‐stayed bridge, the efficient strategy followed in order to form an extensive and high‐quality database and the different techniques successively employed to identify modal properties are described, showing the potential of operational modal analysis in the assessment of the dynamic behavior of a complex structure and the usefulness of free vibration tests in the accurate identification of modal damping ratios. The full characterization of the dynamic behavior of the bridge provides the definition of the so‐called zero‐state condition of the bridge and has been used as reference in the subsequent surveillance and monitoring of the bridge that has been implemented by Lusoponte, the consortium that owns the concession of the bridge.

Abstract Buildings and civil engineering structures are subjected to natural hazards such as severe earthquakes, tsunamis, floods, and hurricanes, as well as man‐made hazards such as fires, crime, and terrorist attacks, during their long‐term use. To mitigate these hazards, monitoring various risks in a building employing structural health monitoring (SHM) technologies is necessary. In this article, a concept of risk monitoring of buildings for disaster mitigation is presented and related sensing technologies are reviewed. As advanced examples of risk monitoring of buildings, a ubiquitous structural monitoring (USM) system and a risk information delivery (RID) system using wireless sensor networks are introduced.

Advisory Circular 29-2 C, Section MG-15, Airworthiness Approval of Rotorcraft Health and Usage Monitoring System (HUMS), provides guidance for achieving airworthiness approval for installation, credit validation, and instructions for continued airworthiness for a full range of HUMS applications. The state-of-the-art HUMS and recent advancements including usage monitoring, flight regime recognition, fault, and crack detection technologies have begun to allow the use of HUMS for the condition-based maintenance or maintenance credits. “Maintenance credit” means to give approval to a HUMS application that adds to, replaces, or intervenes in industry-accepted maintenance practices or flight operations. Additionally, the future use of HUMS can eventually allow the fatigue life of rotorcraft components to be extended or the life-limited components to be removed before its fatigue life is fully consumed. Therefore, HUMS technologies and their applications can be used to achieve the safety goal, maintain continued airworthiness, and improve operating costs of rotorcraft. This article provides the Federal Aviation Administration (FAA) perspective of how HUMS are being used or may be used in rotorcraft to address safety and continued airworthiness issues. This article also describes a few FAA-critical research efforts to achieve the full implementation of HUMS for usage credits.