PHM Sensor Implementation in the Real World - a Status Report

A growing field such as diagnostics involves moving technology from cutting-edge to commonplace. In an aircraft environment, the issues of cost, weight, and safety put severe constraints on implementation while demanding increased value. Prognostics and health management (PHM) sensors that monitor systemic rather than localized conditions often show the most value by covering a greater number of components for a given weight. By the same token, such sensors often cross physical, organizational, and in some cases, corporate boundaries, which complicates the already thorny integration issues presented by aircraft packaging. Today the model for aircraft PHM is the Joint Strike Fighter (JSF) program, which offers operational cost and safety benefits well beyond currently employed strategies. This is achieved in part by fielding technologies that have not been in a production flight environment before. By examining the challenges to real-world implementation, it is possible to better understand the problems that inevitably crop up. This can lead to the anticipation and mitigation of risks, which controls cost and increases the probability of the PHM system's success. For JSF PHM, a suite of engine sub-system sensors has been identified, which includes gas path debris monitoring. Gas path debris monitoring is indeed a holistic system; a turbine engine is foremost a way to move air, and monitoring the in- and outflows of the working fluid tells a lot about the inner workings of the engine. Gas path debris monitoring for JSF comprises the ingested debris monitoring system (IDMS), which monitors debris ingested into the engine intake and the exhaust debris monitoring system (EDMS), which monitors debris produced by gas path component faults and also the effects of ingested debris (if present). Both sensors present significant integration challenges. The IDMS is an engine sensor mounted in the inlet duct of the airframe, and the inlet duct is an integral part of the sensor. The EDMS is mounted in the tail section with significant thermal and durability concerns. This paper examines some of the considerations with implementing a PHM sensor system in the real-world environment of an aircraft program just short of first flight. The I/EDMS serve as a case study to highlight these issues