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The strategic planning and tactical execution of Air Traffic Control (ATC) provided by Air Navigation Service Providers (ANSP) are often not aligned and lead to inefficiencies in the Air Traffic Management (ATM) system. This paper proposes an analytical framework for the air traffic control system based on a system-of-systems paradigm, with a hierarchy of nested and cascaded feedback control loops—one or more for each type of control service. The framework is then used to assess the stability and response to random variables, such as poor weather and equipment failures. The performance of each control loop is then described qualitatively and validates the framework for investigating the benefit of new policies and technologies.

Propulsion engine low-emission combustion technology evolution of the last 30 years is described with a special emphasis on the most recent development, namely Twin Annular Premixing Swirler, TAPS. TAPS mixer technology has been developed for potential application in Single and Dual Annular Combustors, SAC and DAC. Both SAC and DAC TAPS technology development efforts have gone through full-scale annular combustor demonstration for emissions, pressure and airflow distribution, combustor exit temperature quality, structure temperature levels and gradients, lean blowout and ignition characteristics. The SAC TAPS technology demonstration effort involved full-scale engine testing including sea-level emissions, performance, cyclic durability, operability in regard to ignition, acceleration and snap decel (throttle burst-chop transient) and operation under inclement weather conditions.

Results from plant growth experiments utilizing particulate growth media during space flight revealed difficulties associated with providing reliable reproducible gaseous and water supply to plant roots. These limitations were attributed to insufficient understanding of liquid configuration and growth media transport processes in reduced gravity. The objective of this NASA-funded research program is to develop a framework for modeling and quantitative characterization of physical processes associated with flow of wetting and non-wetting phases in particulate plant growth media in microgravity. This paper provides an overview of research plans and current status of research activities. Characterization and modeling of substrate water retention and transport properties in microgravity is key to management and control of gas and liquid fluxes within plant root zones.

The study of Supercooled Large Droplets (SLD) has received greater attention in the Aviation industry since the ATR-72 accident in 1994, which was attributed to SLD. This type of icing cloud usually consists of droplets of up to a millimeter in diameter and mean volumetric diameter (MVD) greater than 40 microns1. The analyses of the ice accretion process with SLD have focused mainly on the wing and stabilizers, particularly on the leading edges where accretion can occur beyond the ice protected areas. There are several numerical and empirical models to predict the mass and shapes of ice accreted from SLD, but there are few published papers that focus on SLD accretion within aircraft turbofan engines2, 3, 4, 5, 6, 7, 8, 9. SLD droplets have higher inertia than conventional icing droplets, which leads to their trajectories being less influenced by the aerodynamic forces. However, large droplets are more likely to breakup than smaller droplets when subjected to highly shear flows.

An experimental study was performed in a mockup of a Boeing 767 cabin section consisting of eleven rows with seven seats per row. The ventilation system for the mockup is constructed for actual aircraft components and includes linear diffusers that extend the full length of the mockup. Ventilation flow rates representative of an actual aircraft were used for all experiments. Seats in the mockup were occupied by thermal manikins to simulate passenger heat load. A motorized beverage cart traversed the length of the right aisle. Tracer gas and smoke visualization were used to determine the effect of the moving cart on transport of contaminants in the cabin. Carbon Dioxide (CO₂) tracer gas was injected at a constant flow rate at a location adjacent to the aisle until concentrations in the cabin reach steady-state.

The dual-probe heat-pulse (DPHP) method uses temperature increase with time after heating to measure soil heat capacity, which then is related to soil volumetric water content. The coarse-textured plant growth media being considered for spaceflight applications may lead to problems in contact resistance between the medium and the probes of the DPHP sensor, which may limit the effectiveness of the method. The DPHP method was evaluated in 0.25-1 mm and 1-2 mm fritted clay media. Specific heat, determined using differential scanning calorimetry, was 830 J kg−1 °C−1 at 20 °C for the 0.25-1 mm medium and 810 J kg−1 °C−1 at 20 °C for the 1-2 mm medium. Good agreement between sensor measurements and independent water content measurements obtained through oven-drying was indicated by a linear regression of y = 1.00x + 0.0087 and a standard error of 0.04 cm3 cm−3. The DPHP method can be used to accurately monitor water content in the coarse media being considered for spaceflight applications.

This paper describes the complete development of a GPS-aided INS (GPS/INS) system and photogrammetry methods used to validate the system. The GPS/INS is developed using strap down accelerometer and rate gyro sensors for inertial sensors and GPS measurements of position and velocity. These sensors are integrated in an extended Kalman filter using kinematic differential equations. The photogrammetry uses images captured from video footage of flight tests to verify the performance of the system. Experimental data and validation results are presented from flight tests using a small unmanned aerial vehicle.

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.

This paper reviews reportable aviation incidents and associated cost losses. Aviation incidents include visible smoke incidents inside aircraft passenger cabins, occurrences of fumes and oily smells, and illness cases reported by flight crew members in 2012, for US based carriers for domestic flights and all international flights that either originated or terminated in the US. Cost losses include direct and indirect costs endured by different airlines due to diversions from the scheduled flight route, returns to departure airport, expedited arrival procedures, and cancellation of flights on ground. Two case study scenarios are presented to illustrate minimum and maximum costs limits. Sources used to collect data for this article include the Bureau of Labor Statistics, Federal Aviation Administration online database, Research and Innovative Technology Administration database (RITA), and official airline websites.

The goals of the current research were (1) to identify the information necessary for the air carrier pilot to maintain “traffic awareness” in a system that included a free-flight traffic environment, a pilot, and a Cockpit Display of Traffic Information (CDTI) and (2) to apply and evaluate the utility of the Function Allocation Issues and Tradeoffs (FAIT) analysis (Riley, 1993). One hundred information requirements were identified. The FAIT analysis indicated the following characteristics of the system are highly influential in a free-flight traffic environment: Weather, General piloting skills, Time of day, Terrain, Ownship state (e.g., altitude, attitude, speed, etc.), Level of pilot mental workload, and Perceived time pressure.

During full body fatigue testing, an aircraft wing spar initiated a crack from a rivet hole and crack growth data was obtained unique to the test spectrum loading. Fatigue testing of the 7050-T73511 spar material was used to obtain crack growth rate data and variable amplitude fatigue crack growth tests were performed on specimens fabricated from the spar material. Calculated results were in excellent agreement with these experimental results. A layered analysis of the adhesively bonded spar showed that the stress intensity in the lower cap was approximately constant, independent of crack length. When the constant stress intensity is used in a variable amplitude fatigue crack growth analysis, there is good correlation between the predicted and observed crack growth rates.

This paper identifies critical and relevant variable/adaptive cycle turbine engine and propulsion subsystem technologies for future next generation aviation systems. A comprehensive evaluation of key technology drivers associated with the development and demonstration of advanced Adaptive Power and Thermal Management System (APTMS) technologies applicable to next generation platforms is addressed. Specifically, the paper explores energy optimization through dynamic mission based simulations of an advanced hybrid air cycle / vapor cycle APTMS architecture combining multiple traditionally federated subsystem functions including auxiliary power, environmental control, emergency power, and engine start.

To obtain a system level, integrated perspective on vehicle energy management, the traditional methods for conducting preliminary design, gauging independent requirements, must be abandoned. This method does not capture critical interactions between the various aircraft subsystems. Instead, a more global appreciation for interactions across boundaries needs to be realized with a mosaic scheme, where models are integrated and co-simulated. The advantage of this approach is to enhance the preliminary design stage by predicting integration issues early in the development process. Legacy design practice involved gathering data from multiple vendors in order to produce design iterations. The ability to link models directly is extremely beneficial, as requirements no longer have to be executed independently. This approach reduces cumbersome iterations between model owners and accelerates trade studies.

The optimal integration of vehicle subsystems is of critical importance in the design of future energy efficient fighter aircraft. The INVENT (INtegrated Vehicle ENergy Technology) program has been dedicated to this endeavor through modeling/simulation of thermal management, power generation & distribution, & actuation subsystems. Achieving dual cooling & power generation capability from a single subsystem would be consistent with current efforts in system integration optimization. In this paper, we present a reconfiguration of an archetypal closed-loop air cycle system for a modern fighter as an open-loop gas generator cycle operating interchangeably between refrigeration and auxiliary power modes. A numerical model was developed within NPSS to assess maximum power extraction capabilities of a system originally designed for cooling purposes under different operating conditions.

Recent emphasis on optimization of engine technologies with ancillary subsystems such as power and thermal management has created a need for integrated system modeling. These systems are coupled such that federated design methods may not lead to the most synergetic solution. Obtaining an optimal design is often contingent on developing an integrated model. Integrated models, however, can involve combining complex simulation platforms into a single system of systems, which can present many challenges. Model organization and configuration control become increasingly important when orchestrating various models into a single simulation. Additionally, it is important to understand such details as the interface between models and signal routing to ensure the integrated behavior is not contaminated or biased. This paper will present some key learnings for model integration to help alleviate some of the challenges with system-based modeling.

It is typical in aircraft engine design to explore new configurations in a constant effort to achieve greater efficiency with respect to various considerations. An integral component of this process requires a complete and robust simulation of rotor dynamics. Tuning the design with results of rotor dynamics simulations can be made possible with a tool that has adequate modeling techniques to capture the physics associated with engine behavior under various operating conditions accurately.

An important part of future air vehicle design will be the development of a transient integrated aircraft system model. DC electric power system modeling poses particular challenges because they are highly dynamic and employ short time constant line replaceable units [1, 2, 3]. This paper describes an approach to modeling an aircraft's electric power system that uses simplified non-physics based models of the line replaceable units that are part of future 270VDC aircraft power systems. The model is an alternative to physics based models and is particularly useful for the initial phases of aircraft development before hardware development has occurred. A 270VDC aircraft power system model is constructed as an example using the unit models. Selected results will be presented.

There is a continuing need to simulate power electronic circuits that include magnetic components. It is necessary to determine the interaction of the magnetic component with the rest of the power electronic system so that a dynamic circuit model of the magnetic components including material saturation and iron losses is required. Also, the magnetic component model must be valid when the magnetic component's excitation is not sinusoidal. A dynamic magnetic circuit model derived from Maxwell's equations along with useful theorems for building circuit models from the structure of the magnetic device is reviewed. The developed circuit models are general including magnetic saturation and iron losses. Simulation results for a DC/DC converter employing a conventional gapped inductor and a gapped coupled inductor are presented.

Current industry trends demonstrate aircraft electrification will be part of future platforms in order to achieve higher levels of efficiency in various vehicle level sub-systems. However, electrification requires a substantial change in aircraft design that is not suitable for re-winged or re-engined applications as some aircraft manufacturers are opting for today. Thermal limits arise as engine cores progressively get smaller and hotter to improve overall engine efficiency, while legacy systems still demand a substantial amount of pneumatic, hydraulic and electric power extraction. The environmental control system (ECS) provides pressurization, ventilation and air conditioning in commercial aircraft, making it the main heat sink for all aircraft loads with exception of the engine fuel thermal management system.

This article attempts to provide a big picture of systems engineering in both philosophy and engineering perspectives, discusses current status and issues, trends of systems engineering development, future directions and challenges, followed by certain examples.