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This paper addresses the issues of data reduction, visualization, clustering and classification for fault diagnosis and prognosis of the Liquid Cooling System (LCS) in an aircraft. LCS is a cooling system that consists of a left and a right loop, where each loop is composed of a variety of components including a heat exchanger, source control units, a compressor, and a pump. The LCS data and the fault correlation analysis used in the paper are provided by Hamilton Sundstrand (HS) - A United Technologies Company (UTC). This data set includes a variety of sensor measurements for system parameters including temperatures and pressures of different components, along with liquid levels and valve positions of the pumps and controllers. A graphical user interface (GUI) is developed in Matlab that facilitates extensive plotting of the parameters versus each other, and/or time to observe the trends in the data.

During teleoperation in space, there are two major sources of performance degradation: (1) spatiotemporal displacements in visual feedback; confounded by (2) microgravity effects, attributable to kinetic and inertial properties of large masses maneuvered in low gravity. Both sources contributed to the Progress-Mir collision in 1997. This report describes findings from two sets of studies directed at modeling possible effects on teleoperation tracking performance of spatial, temporal, and microgravity perturbations in visual feedback presented to the teleoperator. In the first set of studies, effects of both temporal and angular displacements in visual feedback on control of tracking behavior by individual subjects were evaluated under conditions of both continuous pursuit and discrete movement tracking.

This paper describes how Fluorescent Penetrant Inspection (FPI) was used in the past, how it is used now and how it will be used in the future. The United States Air Force (USAF) and Pratt & Whitney (P&W) now use a fully-automated FPI process with manual visual inspection. With direction and funding provided by the USAF/Aeronautical System Center (ASC), these fully-automated FPI processors, located at Kelly Air Force Base in San Antonio, Texas were developed, manufactured, installed, qualified and put into operation by Pratt & Whitney. This paper will cover the following: the Qualification and Acceptance Tests which include test objectives, test articles, test facility, test equipment, test results, and training.

This paper describes Pratt &Whitney's pioneering work in “constrained dynamic inversion,” a control algorithm architecture for multivariable systems that must operate tight to limits. A hallmark of gas turbine control is the prevalence and fundamental importance of tightly holding limits. When constrained dynamic inversion is applied to gas turbine systems control, this algorithm enables operation closer to physical and operational limits, while also providing faster and more precise responses. In addition to more fully exploiting systems physical capabilities, this architecture provides for the independent and finely coordinated control of system variables-of-interest even when each effector affects all variables. A distinctive feature of this algorithm is that it can be implemented on state of the art controllers at update rates consistent with vehicle control.

Over the past few decades, advanced methods have been developed for the analysis of digital systems using mathematical reasoning, i.e., formal logic. These methods are supported by sophisticated software tools that can be used to perform analysis far beyond what is practically achievable using “paper and pencil” analysis. In December 2011, RTCA published RTCA DO-178C [1] along with a set of technical supplements including RTCA DO-333 [2] which provides guidance on the use of formal methods towards the certification of airborne software. Such methods have the potential to reduce the cost of verification by using formal analysis instead of conventional test-based methods to produce a portion of the verification evidence required for certification.

Modern aircraft systems employ numerous processors to achieve system functionality. In particular, engine controls and power distribution subsystems rely heavily on software to provide safety-critical functionality, and are expected to move toward multicore architectures. The computing hardware-layer of avionic systems must be able to execute many concurrent workloads under tight deterministic execution guarantees to meet the safety standards. Single-chip multicores are attractive for safety-critical embedded systems due to their lightweight form factor. However, multicores aggressively share hardware resources, leading to interference that in turn creates non-deterministic execution for multiple concurrent workloads. We propose an approach to remove on-chip interference via a set of methods to spatio-temporally partition shared multicore resources.

This paper addresses the issue of fault diagnosis in the heat exchanger of an aircraft Air Conditioning System (ACS). The heat exchanger cools the air by transferring the heat to the ram-air. Due to a variety of biological, mechanical and chemical reasons, the heat exchanger may experience fouling conditions that reduces the efficiency and could considerably affect the functionality of the ACS. Since, the access to the heat exchanger is limited and time consuming, it is preferable to implement an early fault diagnosis technique that would facilitate Condition Based Maintenance (CBM). The main contribution of the paper is pre-flight fault assessment of the heat exchanger using a combined model-based and data-driven approach of fault diagnosis. A Simulink model of the ACS, that has been designed and validated by an industry partner, has been used for generation of sensor data for various fouling conditions.

This paper provides an insight into how the introduction and implementation of the blending borescope used to perform on-wing blending of compressor blades on Pratt & Whitney (P&W) Engines has resulted in significant savings. It describes the following: Commercial statistics and savings; Military statistics and potential savings; P&W maintenance team; What is on-wing blending; The capabilities of on-wing blending; The contents of a typical blending borescope inspection kit; Test results; Measurement of Foreign Objects Damage (FOD); Installation of the equipment; How to blend FOD; How to measure the repair and observe how the equipment provides precise results; How to polish the repair. Typical commercial cost savings for blending assembled compressors are in the order of $360,000.00 per event, compared with engine teardown cost.

The intent of a balanced engine design process is to satisfy all systems requirements including operability, performance and durability. Due to the complexity of the trade-off process of the various metrics it is possible that system improvements may be required after a turbofan engine enters production. Also, in the case of derivative engines, configured for increased performance, the flowpath aerodynamics may be challenged and may have to be examined to ensure there is no flow field anomaly. By incorporating special diagnostic aero instrumentation at the earliest opportunity any required operability improvement can be identified and corrective action taken. The paper first delineates the component matching challenges of twin spool mixed flow turbofan engines. Then it discusses investigation of various potential destabilizing influences.

A number of amine-based carbon dioxide (CO2) removal systems have been developed for atmosphere revitalization in closed loop life support systems. Most recently, Hamilton Sundstrand has developed an amine-based sorbent, designated SA9T, possessing approximately 2-fold greater capacity compared to previous formulations. This new formulation has demonstrated applicability for controlling CO2 levels within vehicles and habitats as well as during extravehicular activity (EVA). Our current data demonstrates an amine-based system volume which is competitive with existing technologies which use metal oxides (Metox) and lithium hydroxide sorbents. Further enhancements in system performance can be realized by incorporating humidity and trace contaminant control functions within an amine-based atmosphere revitalization system. A 3-year effort to develop prototype hardware capable of removing CO2, H2O, and trace contaminants from a cabin atmosphere has been initiated.

Supported amines have been shown to absorb CO2 cyclically under temperature swing absorption (TSA) conditions, and show a substantial decrease in desorption energy compared to zeolite materials. Supported amines may therefore be a viable alternative for cyclic capture of CO2 on long-term space missions where minimal energy expenditure is a critical consideration. The research described in this paper presents efforts to improve the TSA-supported amine system with a focus on relationships between important parameters affecting cyclic CO2 capacities, as well as reaction effects of CO2 with the modified amine tetraethylenepentamine.

In this study, a parametric examination of the main factors affecting cyclic CO2 absorption into supported amine sorbents has been conducted. A bench-scale test apparatus and Taguchi statistical design of experiments were used to assess the importance of cycle time, inlet CO2 concentration, residence time, humidity, absorption temperature, desorption temperature and desorption pressure on cyclic CO2 capacity. Two amine sorbents were considered: TEPAN and modified E-100. Amine decomposition, amine oxidation, and the effects of amine chemical composition were also examined. For typical ranges of system variables found on-board the space shuttle orbiter, results indicated that desorption pressure over the range of 25–85 torr, desorption temperature over the range of 50–60°C, absorption temperature over the range of 20–30°C, and CO2 concentration over the range of 6–9 mmHg were the most important variables affecting cyclic CO2 removal capacity.

This technical paper presents the author's recommended approach to one aspect of managing flight safety - conducting Safety Risk Analyses (SRA) on in-service problems that may threaten flight safety. The author did not develop this statistically based approach for assessing the risk of future events, but has helped to improve it and highly endorses it. In conducting a safety risk analysis, the analyst might decide to perform a “quick” SRA and will need a minimal amount of information that will show the relative level of flight safety risk. When the analyst decides a complete safety risk analysis is needed, the possible approaches and level of details included in the SRA can vary greatly from company to company.

A Distributed Engine Control Working Group (DECWG) consisting of the Department of Defense (DoD), the National Aeronautics and Space Administration (NASA)- Glenn Research Center (GRC) and industry has been formed to examine the current and future requirements of propulsion engine systems. The scope of this study will include an assessment of the paradigm shift from centralized engine control architecture to an architecture based on distributed control utilizing open system standards. Included will be a description of the work begun in the 1990's, which continues today, followed by the identification of the remaining technical challenges which present barriers to on-engine distributed control.

The Environmental Control System (ECS) of an aircraft provides thermal and pressure control of the engine bleed air for comfort of the crew members and passengers onboard. For safe and reliable operation of the ECS under complex operating environments, it is critical to detect and diagnose performance degradations in the system during early phases of fault evolution. One of the critical components of the ECS is the heat exchanger, which ensures proper cooling of the engine bleed air. This paper presents a wavelet-based fouling diagnosis approach for the heat exchanger.

This paper addresses the issues of Fault Detection and Isolation (FDI) in complex networked systems such as the Environmental Control System (ECS) of an aircraft. The ECS controls and supplies pressurized air to the aircraft and consists of multiple subsystems that in turn consist of interconnected components, heterogeneous sensing devices, and feedback controllers. These complex interconnections and feedback control loops make fault detection and isolation a very challenging task in the ECS. For example, a faulty component yields off-nominal outputs which are inputs to the other coupled components. This coupling leads to off-nominal outputs from otherwise healthy components, thus causing unwanted false-alarms. Secondly, due to off-nominal inputs, the healthy components are driven beyond their normal operating conditions, leading to cascading failures.

In the present study, an experimental investigation was conducted to characterize a hot-air-based anti-/de-icing system for the icing protection of aero-engine inlet guide vanes(IGVs). The experimental study was conducted in a unique icing research tunnel available at Iowa State University (i.e., ISU-IRT). A hollowed IGV model embedded with U-shaped hot-air flowing conduit was designed and manufactured for the experimental investigations. During the experiments, while a high-speed imaging system was used to record the dynamic ice accretion or anti-/de-icing process over the surface of the IGV model for the test cases without and with the hot-air supply system being turned on, the corresponding surface temperature distributions on the IGV model were measured quantitatively by using a row of embedded thermocouples.

A through-flow based Monte Carlo particle trajectory simulation is used to calculate the ice crystal paths in the low pressure compressor of a high bypass ratio turbofan engine. The simulation includes a statistical ice particle breakup model due to impact on the engine surfaces. Stage-by-stage ice water content, particle size and particle velocity distributions are generated at multiple flight conditions and engine power conditions. The majority of the ice particle breakup occurs in the fan and first LPC stage. The local ice water content (IWC) within LPC is much higher than the ambient conditions due to scoop effects, centrifuging and flow-path curvature. Also the ice particles approach the stators at lower incidence angles than the air flow. The simulation results prompt the need to revisit the approach for properly setting up boundary conditions for component or cascade testing.

Engine module performance trending and engine system anomaly detection and identification are core capabilities for any engine Condition Based Maintenance system. The genesis of on-condition monitoring can be traced back nearly 4 decades, and a methodology known as Gas Path Analysis (GPA) has played a pivotal role in its evolution. GPA is a general method that assesses and quantifies changes in the underlying performance of the major modules of the engine (compressors and turbines) which directly affect performance changes of interest such as fuel consumption, power availability, compressor surge margins, and the like. This approach has the added benefit in that it enables anomaly detection and identification of many engine system accessory faults (e.g., variable stator vanes, handling and customer bleeds, sensor biases and drift). Legacy GPA has been confined to off-board analysis of snapshot data averaged over a stable flight conditions when the engine is in steady state operation.

The global electric and hybrid aircraft market utilizing lithium-ion Energy Storage Systems (ESS) as a means of propulsion, is experiencing a period of extraordinary growth. We are witnessing the development of some of the most cutting-edge technology, and with that, some of the most complex challenges that we as an industry have ever faced. The primary challenge, and the most critical cause of concern, is a phenomenon known as a “Thermal Runaway”, in which the lithium-ion cell enters an uncontrollable, self-heating state, that if not contained, can propagate into a catastrophic fire in the aircraft. A Thermal Runaway (TR) can be caused by internal defects, damage, and/or abuse caused by an exceedance of its operational specifications, and it is a chemical reaction that cannot be stopped once the cell has reached its trigger temperature.