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This paper describes an alternative architecture candidate proposal for consideration for the future Dual Frequency Multi-Constellation (DFMC) Ground Based Augmentation System (GBAS). The GBAS architecture candidate builds off the...
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This paper describes an alternative architecture candidate proposal for consideration for the future Dual Frequency Multi-Constellation (DFMC) Ground Based Augmentation System (GBAS). The GBAS architecture candidate builds off the work done over the last 10 years by the Single European Sky Air Traffic Management Research (SESAR) program. However, the proposed alternative architecture is designed to enable more optimal airborne processing that is expected to enable better performance (e.g. higher accuracy and smaller alert limits), increased robustness to loss of civil GNSS signals on either L1/E1 or L5/E5a frequency as well as to the loss of a constellation, and higher availability for DFMC GBAS globally. The alternative architecture is envisioned to support one or more new levels of GBAS approach service. This GBAS Approach Service Type (GAST) will be referred to generically as GAST X in this paper. GAST X is envisioned as a natural extension of the currently defined GAST C and GAST D. The proposal borrows heavily in many respects from the SESAR proposal for DFMC GBAS documented in reference. However, some of the processing has been reallocated to the airborne equipment in order to enable some very desirable capabilities. In the proposed GAST X DFMC GBAS concept, raw measurements from both L1/E1 and L5/E5a civil GNSS frequencies are uplinked in addition to corrections and other parameters that are already uplinked from ground stations that support the existing GAST C and D services. Uplinking raw measurements instead of corrections potentially enables the use of pure carrier phase position solutions such as Real Time Kinematic (RTK) Carrier Phase (CP) based solutions. Moreover, it allows for a low noise long baseline airborne iono gradient monitoring capability. This paper describes the basic architecture to support GAST X and gives some predicted performance results for accuracy, the size of protection levels and the availability based on a simulation study. In addition, the paper discusses a potential set of services and considers the transition between service levels that would result from loss of a frequency or total failure of a constellation.
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The purpose of this presentation is to discuss important considerations for conducting an environmental qualification of a product The scope of this presentation is limited to process considerations and philosophy This presentatio...
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The purpose of this presentation is to discuss important considerations for conducting an environmental qualification of a product The scope of this presentation is limited to process considerations and philosophy This presentation is geared toward Environmental Qualification of products. It may or may not be applicable to other qualification efforts, such as electromagnetic interference/ electromagnetic compatibility (EMI/EMC).
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The purpose of this presentation is to discuss important considerations for conducting an environmental qualification of a product; The scope of this presentation is limited to process considerations and philosophy.
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Single Frequency Satellite Based Augmentation Systems (SFSBAS) systems such as WAAS, EGNOS, MSAS and GAGAN have been providing differential corrections and integrity bounds for the L1 GPS C/A and L1 SBAS ranging signals. These SBA...
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Single Frequency Satellite Based Augmentation Systems (SFSBAS) systems such as WAAS, EGNOS, MSAS and GAGAN have been providing differential corrections and integrity bounds for the L1 GPS C/A and L1 SBAS ranging signals. These SBAS corrections have been used in computing SBAS corrected position solutions and SBAS based protection levels in aviation receivers. The single frequency SBAS based position and integrity is used in all phases of the flight including when performing precision RNP (Required Navigation Performance) operations and LPV (Localizer Performance with Vertical guidance) approaches. Recently the concept of operations of Dual-Frequency, Multi-Constellation (DFMC) SBAS (also referred to as SBAS L5) has been introduced and the first version of the DFMC SBAS receiver performance document (ED- 259) has been published. DFMC SBAS is designed to augment both GPS and Galileo constellations and it works on the assumption that the on-board GNSS receivers can track both L1 and L5 band signals. ED-259 specifies the airborne receiver requirements for the integration of DFMC SBAS augmenting GPS and Galileo constellations. DFMC SBAS primarily corrects for the GNSS satellite clock and ephemeris errors. Since iono-free pseudo range measurements are required to be used by the receiver, DFMC SBAS does not need to provide ionospheric corrections. All current and future SBAS providers have DFMC SBAS in their roadmap. The objective of this paper is to study the potential benefits of DFMC SBAS from the perspective of an aviation certified GNSS receiver manufacturer. Collins Aerospace has been working on a project funded by the EUSPA (European Union Agency for the Space Programme) known as MUlti-mode GPS and Galileo (MUGG). The objective of the MUGG project is to develop a DFMC SBAS GNSS aviation receiver with real-time SBAS L5 and H-ARAIM functions in order to validate the ED-259 Revision A MOPS requirements currently in development. The MUGG prototype is based on an aviation certified (TSO) Collins Multi-Mode Receiver (MMR), the GLU-2100 whose hardware already integrates the DFMC growth capability. This MMR hardware has been certified on multiple Boeing and Airbus platforms. The potential benefits of DFMC SBAS are expected to be the availability of lower protection levels, faster time to compute a full SBAS precision approach (PA mode) solution (since the single frequency SBAS ionospheric corrections grid does not need to be downloaded) and the potential to expand SBAS service to new areas with limited infrastructure. This paper will begin by briefly describing the main differences between the SFSBAS and DFMC SBAS systems and their impact to receiver processing. Next, real historical broadcast data from WAAS. EGNOS, MSAS and GAGAN satellites will be used to compute SBAS horizontal and vertical protection levels (HPL and VPL) and this will be compared against a hypothetical dual-frequency SBAS system that utilizes on-board iono-free GPS pseudo range measurements. The historical contribution of the ionospheric component to the overall SBAS based protection level will be studied and analyzed. Further the benefits of adding Galileo to DFMC SBAS positions will be studied by modelling Galileo satellite clock and ephemeris corrections and determining its impact to the SBAS performance. Additionally, world-wide availability analysis will be performed using the historical broadcast data. It is expected that this paper will provide insight into the expected benefits of DFMC SBAS and provide a means to perform a cost-benefit analysis for the introduction and adoption of DFMC SBAS for receiver manufactures, air navigation service providers, aircraft manufacturers and airlines.
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The Aerospace & Defense (A & D) industries maintain a high level of interest in the expansive amount of work performed in developing and qualifying Pb-free solder alloys. The three main areas of interest continue to be thermal cycle, mechanical shock, and vibration. The past twenty years have seen an unprecedented increase in alloy development such that the concepts of "generations of solders and "families of solders" have been coined to help manage the numerous individual alloys on the market today. This paper will discuss work done with Pb-free solder alloys, many with the addition of constituents focusing on varying property enhancements. The purpose is to prov ide a "snap shot" summary of progress to date and relate perspectives both as advantages and concerns solely in a constructive manner to aid researchers in planning their next steps in development and qualification of these alloy s....
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The Aerospace & Defense (A & D) industries maintain a high level of interest in the expansive amount of work performed in developing and qualifying Pb-free solder alloys. The three main areas of interest continue to be thermal cycle, mechanical shock, and vibration. The past twenty years have seen an unprecedented increase in alloy development such that the concepts of "generations of solders and "families of solders" have been coined to help manage the numerous individual alloys on the market today. This paper will discuss work done with Pb-free solder alloys, many with the addition of constituents focusing on varying property enhancements. The purpose is to prov ide a "snap shot" summary of progress to date and relate perspectives both as advantages and concerns solely in a constructive manner to aid researchers in planning their next steps in development and qualification of these alloy s.
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This paper presents GPS and Galileo airframe multipath statistics derived from more than 50 flight hours on an experimental Boeing 777 airplane using prototype Collins Aerospace Dual-Frequency, Multi-Constellation (DFMC) receivers...
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This paper presents GPS and Galileo airframe multipath statistics derived from more than 50 flight hours on an experimental Boeing 777 airplane using prototype Collins Aerospace Dual-Frequency, Multi-Constellation (DFMC) receivers. These results are an important step toward validation of the integrity and accuracy algorithms that will be used in the first aviation industry standards for use of combined GPS and Galileo for safety of life services such as navigation, landing, and surveillance for aircraft separation. This paper presents the experimental flight test program and equipment setup. Prior work to derive airframe multipath is referenced, then the algorithms and methods used to estimate multipath on GPS L1 and L5, Galileo E1 and E5a, and the ionosphere free combinations of those signals are described in detail. Multiple potential techniques for estimating airframe multipath and deriving integrity bounds appropriate for precision approach and landing are described. Handling of antenna group delay variation with angle of arrival, ionosphere delay, and receiver noise are discussed, and multiple ways to visualize the results are presented to address various trades for consideration in standards bodies. Multipath error statistics are shown to be minimally dependent on the signal direction of arrival for this particular test setup. By aggregating data from all satellite elevation angles, enough samples were available to evaluate the impact of carrier smoothing time with statistical significance. The effect of carrier smoothing on multipath error bounds is explored using 100, 300, and 600 seconds smoothing time constants, showing larger smoothing times as a viable means to reduce multipath errors and increase availability of DFMC position accuracy and integrity bounds.
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The International Civil Aviation Organization (ICAO) Ground Based Augmentation System (GBAS) Working Group (GWG) is working on development of standards for Dual-Frequency Multi-Constellation (DFMC) GBAS. In the initial stage of th...
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The International Civil Aviation Organization (ICAO) Ground Based Augmentation System (GBAS) Working Group (GWG) is working on development of standards for Dual-Frequency Multi-Constellation (DFMC) GBAS. In the initial stage of the development, an architecture trade study is being conducted in order to select the overall architecture and to develop the concept of operation (ConOps) for DFMC GBAS. A previous paper discussed an alternative architecture candidate proposal for consideration for the future DFMC GBAS based on uplinking raw measurements in addition to the differential corrections that are already uplinked to support legacy GBAS service types. That paper discussed various advantages and disadvantages of the proposed architecture known as GAST X. This paper extends the work done in that paper to provide greater clarity regarding proposed ionospheric gradient monitoring techniques. This paper describes three strategies for Ionospheric Gradient monitoring and compares the relative performance of those strategies. Two of the strategies are based on the GAST X architecture and the third is based on the architecture proposed by Eurocontrol developed under the SESAR program. The paper defines the test statistics and processing for each strategy. The paper then expands on expected noise characteristics and errors sources relevant to observation of the iono gradient monitor with each strategy. Methods for bounding residual ionospheric errors and for detection and isolation of ranging sources with large iono gradients are discussed. Finally the results of an availability study comparing the performance of the three different strategies is presented. The results presented in the paper show clearly the advantages of the GAST X architecture for ionospheric anomaly monitoring. Also the paper highlights areas where validation by analysis of measurements in representative environments is needed.
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Since the beginning of aviation, aircraft designers, researchers, and pilots have monitored the skies looking for clouds to determine when and where to fly as well as when to deice aircraft surfaces. Seeing a cloud has generally c...
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Since the beginning of aviation, aircraft designers, researchers, and pilots have monitored the skies looking for clouds to determine when and where to fly as well as when to deice aircraft surfaces. Seeing a cloud has generally consisted of looking for a white / grey puffy orb floating in the sky, indicating the presence of moisture. A simple monitoring of a temperature gauge or dew point sensor was used to help determine if precipitation was likely or accumulation of ice / snow on the airframe could occur. Various instruments have been introduced over the years to identify the presence of clouds and characterize them for the purposes of air traffic control weather awareness, icing flight test measurements, and production aircraft ice detection. These instruments have included oil slides, illuminated rods, vibrating probes, hot wires, LIDAR, RADAR, and several other measurement techniques. Each technology has its own strength and weakness including the particle size range and water content that can be measured and its ability (or lack thereof) to discriminate different types of icing conditions. The FAA release of 14 CFR Part 25 Appendix O and 14 CFR Part 33 Appendix D regulations for SLD and ice crystals has spawned an increased need for detecting and differentiating these icing conditions from the traditional Appendix C clouds. In order to perform these functions, changes to the measurement technologies and flight crew identification methods are needed. To assist ice detector and aircraft manufacturers in the design and certification of systems with these expanded functionalities, an update to ED-103 (AS5498) was recently released. Revision A of this document now provides requirements for the detection and differentiation of Appendix C, O, and D clouds. In 2009, the FAA released Amendment 25-129 which added paragraphs (e) through (h) to § 25.1419 adding focus to the operation of ice protection systems. Amendment 25-140 was released a few years ago adding the Appendix D and O icing environments. While the use of primary and advisory ice detection systems to meet the requirements of § 25.1419 (e) and (g) have steadily increased, the addition of the new icing envelopes has substantially increased the performance demonstrations required. Performance verification is typically performed through icing wind tunnel tests, icing flight tests and comparison to reference instrumentation to show compliance with FAA requirements via the methods described in AS5498A. Demonstrating compliance to these new detection and differentiation requirements over the wide variety of icing conditions presents a significant challenge - particularly as particle sizes increase and water content decreases. The capabilities of facilities and instrumentation used in demonstrating performance have limitations that complicate the evaluation. Some have assumed that an ice detection system failing to meet all expectations would be certified as advisory, giving the flight crew the primary responsibility for detecting icing conditions. This strategy, however, is not clear cut and has its own issues. The discussion herein is intended to shed some light on the certification challenges that exist for verifying the means to detect / differentiate all types of clouds and offers some suggestions on how to resolve this conundrum.
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In this paper we introduce the Agile Model-Based Integration Framework (AMBIF), a multi-domain modelling and simulation environment. Relying on open-standard interfaces, AMBIF enables the virtual integration of a Cyber-Physical Sy...
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In this paper we introduce the Agile Model-Based Integration Framework (AMBIF), a multi-domain modelling and simulation environment. Relying on open-standard interfaces, AMBIF enables the virtual integration of a Cyber-Physical System (CPS) subsystem models for advanced SW Validation & Verification (V&V) analysis. Leveraging AMBIF, we propose a methodological approach where the integrated system model evolves together with the development cycle of its subsystems: the more the subsystem design processes advance and refined subsystem models are available, the more the accuracy and the details of the full system virtual prototype increase. As a result, system-level V&V analyses can be performed all along the product development cycle, spanning among different virtualization abstraction levels including MiL, SiL, VPiL and HiL simulations and continuously assessing system expected behavior and performance. We evaluate the AMBIF capabilities on two industrial use cases: an Air Management System and an Electro-Mechanical Actuator system.
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A recurring debate in product qualification concerns criticality of article orientation during dynamics testing. Conflicts arise where an ideal of accurate environment simulation is pitted against schedule and budget realities. Wh...
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A recurring debate in product qualification concerns criticality of article orientation during dynamics testing. Conflicts arise where an ideal of accurate environment simulation is pitted against schedule and budget realities. When "non-standard" orientation is the most expedient approach, extra care is required to produce a valid test that adequately stresses the product. Although no universal methodology exists, this study attempts to fill the void by identifying technical factors to consider and providing test implementation recommendations. To mature the conversation, the investigation initially focuses on a simple oscillator to demonstrate that although linear system response is not sensitive to direction of gravity, the presence of stiffness nonlinearities can have a significant influence. One obvious application is products protected by passive base isolation. Secondly, the impacts of gravitational pre-stress effects are investigated. Finally, the merits of orientation are weighed against standard test assumptions like single-axis excitation and rigid fixtures. While the outcome of this study is not a "one-size-fits-all" solution, orientation considerations are recommended, with the goal of reducing difficult discussions late in the development cycle. Additionally, guidance is given for products of various size, structural characteristics, and risk. The hope is that this study will ultimately spur development of best practices within the industry.
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