Showing papers on "Required navigation performance published in 2016"

Applying Required Navigation Performance Concept for Traffic Management of Small Unmanned Aircraft Systems

Abstract: In anticipation of a rapid increase in the number of civil Unmanned Aircraft System(UAS) operations, NASA is researching prototype technologies for a UAS Traffic Management (UTM) system that will investigate airspace integration requirements for enabling safe, efficient low-altitude operations. One aspect a UTM system must consider is the correlation between UAS operations (such as vehicles, operation areas and durations), UAS performance requirements, and the risk to people and property in the operational area. This paper investigates the potential application of the International Civil Aviation Organizations (ICAO) Required Navigation Performance (RNP) concept to relate operational risk with trajectory conformance requirements. The approach is to first define a method to quantify operational risk and then define the RNP level requirement as a function of the operational risk. Greater operational risk corresponds to more accurate RNP level, or smaller tolerable Total System Error (TSE). Data from 19 small UAS flights are used to develop and validate a formula that defines this relationship. An approach to assessing UAS-RNP conformance capability using vehicle modeling and wind field simulation is developed to investigate how this formula may be applied in a future UTM system. The results indicate the modeled vehicles flight path is robust to the simulated wind variation, and it can meet RNP level requirements calculated by the formula. The results also indicate how vehicle-modeling fidelity may be improved to adequately verify assessed RNP level.

A Modular Approach to Integrity for APNT

Abstract: The low availability of terrestrial sources is a key chal- lenge in providing alternative position, navigation and timing (APNT) services with integrity to civil avia- tion. This paper proposes a new way of facing this challenge by combining measurements from diverse systems. The proposal includes two different ways of deriving integrity from such a combination. One method is based on combining position solutions from different systems, the other is based on combining measurements from different systems into a single es- timation process. We compute the expected perfor- mance of each method over Germany and study their potential to provide Required Navigation Performance (RNP) services.

Extending Required Navigation Performance to Include Time Based Operations and the Vertical Dimension

Abstract: New Air Traffic Management (ATM) concepts aim at enabling an increase in air traffic while at the same time maintaining the same or a better level of safety. Key enablers for these new ATM concepts are evolving technologies which are successively included in aircraft guidance and control functions. Some components of theses evolving ideas were already introduced in the ATM environment– such as Required Navigation Performance (RNP) - or are in the process of being researched and tested such as Required Time of Arrival (RTA) or advanced RNP. Moreover, with the evolution of air to ground datalink communications, full four-dimensional trajectories could be negotiated between air traffic control and the aircraft and flown in free route airspace [0]. While research into datalink communications, the trajectory management process and conflict resolutiosn are actively being pursued by the ATM research community, so far no requirements for a continuous four dimensional airborne navigation performance have been investigated or specified. Four-dimensional navigation requirements would describe the minimum capability of the aircraft to adhere to the trajectory that was assigned by or negotiated with ATC in the cross-track, along track, vertical and temporal dimension. As such, they would define a 4D RNP concept evolving from the current cross-track RNP specifications [1]. Presently, RNP is a designator for an area navigation system for use within a performance based navigation concept. RNP also includes continuous monitoring of navigation performance and alerting of the pilot in case of failure [1]. Only lateral (or cross-track) RNP accuracy is indicated by a number following the letters RNP, (i.e. RNP 0.3 for 0.3 nm accuracy). In this case, accuracy relates to the Total System Error (TSE) which is a combination of the Flight Technical Error (FTE) and the Navigation Sensor Error (NSE), and designates the 95% uncertainty bounds. Vertical guidance during an RNP operation is accomplished using barometrical vertical navigation (Baro VNav). Limiting factors for vertical navigation are the barometric uncertainty of the altimeter and the human factor in determining the pressure value for the pilot to set in the airplane and no monitoring or position error estimation exists for such Baro VNav systems. In the work presented here, we derive requirements for the missing dimensions vertical, along track and time from high level ICAO prerequisites and presently applicable separation standards. In addition, we introduce new algorithms based on augmented GNSS that continuously monitor the system performance in those additional dimensions. A four dimensional RNP concept needs to be seen as an extension of the current RNP definitions and must include a required navigation performance for the vertical and the along track dimension as well as for time. The along-track or longitudinal component is tightly connected to the time component by means of speed and the RTA at each given waypoint. Thus, from a top-down point of view, it makes sense to define requirements jointly for the along-track / longitudinal component and time through the concept of required time of arrival and speed control. Vertical Required Navigation Performance (vRNP) could be specified as a separate component, since it is largely independent of the other dimensions. Vertical performance requirements are already formulated to some degree for legacy systems. Attachment A to Volume 2 of [1] describes the accuracy requirements of the altimeter system for Baro VNav approach operations. The ICAO documentation on Reduced Vertical Separation Minimums (RVSM) [2] specifies the integrity requirements for altitude in a high density enroute traffic environment. For the vertical RNP, we merge the existing requirements from both documents. Assuming a zero mean Gaussian distribution for the altitude error, a system with a standard deviation of 5.05 m can fulfill this requirement. The limiting factor is the accuracy required by [1], whilst [2] would allow a tail heavy distribution. It is notable that RVSM requires about the same error probability for a vertical error exceeding 90m which the PBN manual requires for an error exceeding 15m during instrument approach. In order to complete the requirement for vRNP, we suggest a monitoring and alerting function which warns the pilot in the case of malfunctions of the barometric altimeter. The monitor performance must also comply with the previously defined error curve. We show that an algorithm using a GNSS solution augmented by a regional augmentation system such as WAAS or EGNOS can be used for monitoring the barometric altitude. The suggested system is capable of monitoring altitude deviations in level flight and up to a certain descent or climb path angle. In the case of longitudinal and time navigation performance no such prerequisites as for vertical RNP exist. Same track separations considerations are largely based on collision risk models that are specifically tailored to a target airspace. Here, for along track RNP and the desired target level of safety given by ICAO, we define requirements for arrival at any point on a trajectory at a given time. Required arrival time accuracy at waypoints is be closely linked to a minimum along track separation requirement as well as separation requirements at merging points of trajectories. We found that the required along track accuracy depends largely on the number of aircraft on a specific route and their respective speed. Results show that, for example, in order to reach a target level of safety of 5x10^-9 with 10 aircraft per hour on a given route crossing a given point, an along track accuracy of 2875 m is needed. With a speed of 400 knots this is equivalent to a required temporal accuracy of 13.5 s assuming no uncertainty on the speed. Along –track position and velocity monitoring is already accomplished by the algorithm for receiver autonomous integrity monitoring (RAIM). The onboard clock needs to be synchronized to a common time base, preferably UTC as it is already used as common reference time for aviation. Since satellite navigation systems are time based, the navigation solution already incorporates clock synchronization with the GNSS time base accurately up to a few milliseconds. Therefore, if the flight management computer is synchronized with GPS time, a precise time reference is always assured, as long as a navigation solution is available. Regional augmentation systems can support the clock accuracy by detecting common system biases in the satellite navigation system that would otherwise map to the clock correction. For redundancy of the clock monitoring, we recommend that two independent systems are used to derive separate clock solutions. One form of cross checking can be a comparison of the UTC time derived from GPS with the UTC time derived from EGNOS or Galileo.

Trajectory Specification for Terminal Air Traffic: Arrival Spacing

Abstract: “Trajectory specification” is the explicit bounding and control of aircraft trajectories such that the position at each point in time is constrained to a precisely defined volume of space The bounding space is defined by cross-track, along-track, and vertical tolerances relative to a reference trajectory that specifies position as a function of time The tolerances are dynamic and are based on the aircraft navigation capabilities and the current traffic situation A standard language will be developed to represent these specifications and to communicate them by datalink Assuming conformance, trajectory specification can guarantee safe separation for an arbitrary period of time, even in the event of an air traffic control system or datalink failure; hence, it can help to achieve the high level of safety and reliability needed for air traffic control automation As a more proactive form of air traffic control, it can also maximize airspace capacity and reduce the reliance on tactical backup systems during

Aircraft navigation performance prediction system

Abstract: Systems and methods for predicting aircraft navigation performance are provided. In one embodiment, a method can include determining that one or more navigational aid measurements are not available to the aircraft. The method can include estimating a future actual navigation performance of the aircraft for a future point in the flight plan. The method can include determining a future required navigation performance associated with the future point in the flight plan. The method can include comparing the future actual navigation performance to the future required navigation performance to determine if the future actual navigation performance satisfies the future required navigation performance. The method can include providing, to an onboard system of the aircraft, information indicative of whether the future actual navigation performance satisfies the future required navigation performance.

GBAS airport availability simulation tool

Abstract: A global navigation satellite system augmentation system availability analysis tool has been developed to simulate a ground-based augmentation system (GBAS) prototype, an integrity monitor test bed, to evaluate its operational benefits at an airport of interest. The proposed availability simulation tool includes all GBAS ground facility algorithms as well as a graphical user interface that allows the user to modify simulation options and parameters. The output of the simulation tool is presented in a Stanford chart to help visualize the performance. The chart indicates the availability and integrity. The performance is evaluated primarily in the vertical position domain because of the weaker satellite geometry and more stringent required navigation performance as compared to those of the horizontal position domain. The simulation tool is implemented in Qt (http://www.qt.io/), an open-source cross-platform toolkit, allowing the tool to run on various devices. The computations are performed in the associated C++ code. The Newark Liberty International Airport (ICAO code: KEWR) is used as a simulation example to demonstrate the utility of the developed tool for investigating how reduced error models impact GBAS availability at the airport.

Community noise management with aircraft dynamic path variation

Abstract: An example method for flight path variation of an aircraft for noise management includes receiving noise inquiries of a community related to aircraft noise during flight over the community, receiving an output from noise sensors positioned within the community, determining a noise distribution plan for additional aircraft flying over the community so as to steer the additional aircraft and distribute additional aircraft noise in response to the noise inquiries and the output from the noise sensors, and based on flight path data of the additional aircraft and the noise distribution plan, assigning a flight path modification to aircraft via a data communication link. The flight path modification informs the aircraft to adjust the flight path to remain within associated margins of a required navigation performance (RNP) instrument flight procedure and to reduce noise impact to the community underneath the flight path.

Evaluation of advanced receiver autonomous integrity monitoring performance on predicted aircraft trajectories

Abstract: The development of new GNSS constellations, and the modernization of existing ones, has increased the availability and the number of satellites-in-view, paving the way for new navigation algorithms and techniques. These offer the opportunity to improve the navigation performance while at the same time potentially reducing the support which has to be provided by Ground and Satellite Based Augmented Systems (GBAS and SBAS). These enhanced future capabilities can enable GNSS receivers to serve as a primary means of navigation, worldwide, and have provided the motivation for the Federal Aviation Administration (FAA) to form the GNSS Evolution Architecture Study (GEAS). This panel, formed in 2008, investigates the new GNSS-based architectures, with a focus on precision approach down to LPV-200 operations. GEAS identified ARAIM as the most promising system. The literature, produced through a series of studies, has analysed the performance of this new technique and has clearly shown that the potential of ARAIM architectures to provide the Required Navigation Performance for LPV 200. Almost all of the analysis was performed by simply studying a constellation's configuration with respect to fixed points on a grid on the Earth's surface, with full view of the sky, evaluating ARAIM performance from a geometrical point of view and using nominal performance in simulated scenarios lasting several days. In this paper, we will evaluate the ARAIM performance in simulated operational configurations. Aircraft flights can last for hours and on-board receivers don't always have a full view of the sky. Attitude changes from manoeuvers, obscuration by the aircraft body and shadowing from the surrounding environment could all affect the incoming signal from the GNSS constellations, leading to configurations that could adversely affect the real performance. For this reason, the main objective of the algorithm developed in this research project is to analyse these shadowing effects and compute the performance of the ARAIM technique when integrated with a predicted flight path using different combinations of three constellations (GPS, GLONASS and Galileo), considered as fully operational.

Considerations on aviation standards for simultaneous independent and dependent parallel approaches

Abstract: Required Navigation Performance (RNP) procedures to parallel runways that include curved approaches offer many benefits to the flying public, airlines, and nearby residents on the ground. Fewer track miles are required during approach, thus enabling decreases in missed connections, fuel burn, emissions, and noise footprint.

Alternative Positioning, Navigation, and Timing Applicable to Domestic PBN Implementation

Abstract: Republic of Korea has established its performance-based navigation (PBN) implementation plan in 2010 for ensuring a smooth transition to PBN operations and relevant new flight procedures are being developed in accordance with the roadmap. Various Navigation aids (NAVAIDs) like global navigation satellite systems (GNSS), distance measuring equipment (DME), VHF omnidirectional range (VOR), inertial navigation system (INS) are used to support PBN procedures. Among them, GNSS would play a central role in PBN implementation. However, vulnerability of satellite navigation signals to artificial and natural interferences has been discovered and various alternative positioning, navigation and timing (APNT) technologies are under development in many countries. In this paper, we study whether continuous PBN operations can be achievable without GNSS signals. As a result, it shows that some of the domestic airports require the construction of APNT in the approach area.

A Novel GNSS Integrity Augmentation System for Autonomous Airport Ground Operations

Abstract: In recent years, the degree of vehicle automation is continuously increasing in all modes of transport. Automated Guided Transport (AGT) systems, which were conceptualised a couple of decades ago are now being realised as unmanned aircraft systems and autonomous ground/sea vehicles. Autonomous ground vehicles are an emerging tool that provide a safer, more cost-effective and sustainable alternative to traditional methods. Furthermore, they offer the capability to detect, alert and compensate for any deviations from the required system performance. In this paper, the system architecture and mathematical modeling of a Global Navigation Satellite System (GNSS) based Navigation and Guidance System (NGS) for autonomous airport surface vehicle operations is presented. Specifically, an integrity augmentation system is implemented in the NGS by modeling the key GNSS error sources (including masking, multipath and signal attenuation). The GNSS based integrity augmentation system is designed to be capable of monitoring the Required Navigation Performance (RNP) and providing usable and timely alerts (by the generation of caution and warning flags). The system is also capable of issuing suitable steering commands to an on-board trajectory re-optimization module; in the event of GNSS signal degradations or losses. One of the key focuses is on modelling the multipath error, which is determined using a ray tracing algorithm. The vehicle position error is obtained as a function of relative geometry between the satellites, receiver antenna and reflectors in realistic airport ground operation environment. Additionally, the airside surface vehicle dynamics and reflective surfaces of buildings located in the airport premises are modelled in order to simulate a 2D trajectory (assuming a flat surface) in a representative airport scenario. Simulation results corroborate the validity of the mathematical models developed for the GNSS based integrity augmentation system, as well as the capability of the system to generate predictive and reactive alerts. Keywords: Airside Operations, Global Navigation Satellite System, Integrity Monitoring and Augmentation, Avionics Based Integrity Augmentation, Model-Predictive, Integrity Flags.

Advanced RNP to ILS Autoland Approaches for Optimal Benefits from PBN: Flight Testing Procedures with an A320

Abstract: We report on the the performance of our Airbus 320 during novel advanced required navigation performance (RNP) procedures which contain a fixed radius turn that delivers the aircraft onto a short ILS precision final. The three main areas of interest of the flight trials were the performance of the autoland capability, vertical path following during the RNP part of the procedure and lateral path following during the transition from RNP to localizer guidance.

Rnav gnss flight validation approach procedures for epkt rwy27

Abstract: The purpose of this document is to present evidence of the work carried out as part of the flight validation activities of the RNAV approach involving the instrument flight procedures (IFPs), down to the localizer performance with vertical (LPV) minima, for RWY27 at Katowice Airport (EPKT). The presented material constitutes the second part of the “Preflight validation RNAV GNSS approach procedures for EPKT in the EGNOS APV Mielec” project. The following issues were addressed: flight validation conditions, list of performed approaches, flight path analysis and pilot feedback.