J.M. Hoekstra

DESIGNING FOR SAFETY THE FREE FLIGHT AIR TRAFFIC MANAGEMENT CONCEPT

Abstract This paper describes the conceptual design and validation of an air traffic management (ATM) concept and the role the safety and human factors played in this design and validation process. The free flight (FF) concept is characterised by being a direct route concept where the pilots, instead of the air traffic controller, are responsible for the separation assurance. Moving this task to the cockpit has consequences for the man machine interface in the cockpit, which needs to be modified to accommodate this new task (micro level design). On top of that, a set of rules and procedures are required to ensure an efficient and safe traffic flow (macro level design). Both the micro and macro aspect of this design are intertwined and require an accurate tuning to arrive at an overall acceptable solution. Both micro-level (flight simulator) experiments and macro-level (traffic simulations) experiments have been conducted to investigate the feasibility of this concept after optimising the initial conceptual design.

CONCEPTUAL DESIGN OF FREE FLIGHT WITH AIRBORNE SEPARATION ASSURANCE

The study described in this paper originally only aimed at studying the human factors problems of airborne separation hi a Free Flight environment. However to define the Free Flight environment with sufficient detail, a concept was designed at NLR. This conceptual design includes rules-of-the-sky, a conflict resolution algorithm, conflict detection, cockpit display recommendations, system description as well as operational implications. The feasibility of the design has been evaluated in three sub-studies: (i) off-line traffic simulations with very high traffic densities and a total of up to 300 aircraft, (ii) a safety analysis comparing the resolution method with current day ATC and (iii) a man-in-the-loop simulator experiment hi traffic densities up to three times the average WestEuropean traffic density with eight air line crews. None of these studies could refute the feasibility of the Free Flight conceptual design.

GRACE - a Versatile Simulator Architecture Making Simulation of Multiple Complex Aircraft Simple

Versatility is an essential asset of any research flight simulator but at the same time a high level of realism is needed to create the right experimental environment. How can a research flight simulator combine both efficiently and become the ultimate research platform? The answer to this question lies in the design of the architecture of the research flight simulator and the software techniques used to enhance its versatility. Each research project poses its specific requirements on the research flight simulator. Different projects require different aircraft types to address specific operational issues. To cope with these ever changing requirements a research flight simulator must be modular not only in software but also in hardware. Flight training simulators need a high level of realism because its essential for the quality of flight training to create a cockpit environment that closely matches the real live cockpit. For a research flight simulator the focus of attention is aimed at the research objective and the changes it brings to the flight deck. In order to produce a high level of realism for a number of aircraft types, as in the case of a research flight simulator, the simulator must be reconfigurable to represent these aircraft types. A cost-efficient solution is one cockpit which can be reconfigured to represent different aircraft types by exchanging hardware components. To combine both versatility and a high level of realism in a research flight simulator a special versatile modular architecture is needed that facilitates both. The National Aerospace Laboratory (NLR) has developed such an architecture and has implemented this architecture with the construction of its new research flight simulator called Generic Research Aircraft Cockpit Environment (GRACE). Both the hardware and the software used for GRACE are constructed to fit in this versatile modular structure. To make it easy to exchange components of the simulator the interfaces between the components must be designed to be generic. Generic in this sense means that the interfaces can support the superset of signals that any module may use. Special attention is needed to control the configuration of the simulator. Flexible configuration of the communication interfaces is the key to easy introduction of new and research specific modules to the architecture. Another technique applied to increase versatility is the use of adaptive software modules. The described versatile modular architecture and all the applied techniques to enhance this architecture are successfully demonstrated for the first time ever in the GRACE research flight simulator. In the most recent research projects GRACE was operated in four different aircraft configurations consisting of Fokker F100, Boeing B747400, Airbus A320 and A330. A lot of research specific software and hardware was integrated into GRACE with low effort and in a short time span. Its unique architecture has made GRACE the most versatile research flight simulator in the world today.

A conceptual third party risk model for personal and unmanned aerial vehicles

A conceptual third party risk (TPR) model is developed, implemented, and tested to demonstrate the capability of determining the risk to the population in a metropolitan city exposed to personal aerial vehicles (PAVs) and unmanned aerial vehicles (UAVs) traffic operations. The conceptual model that is primarily based on the methodology and experience of risk modelling for conventional aircraft is modified and the parameters are adjusted suitable for a determination of risk in the arrival, departure and cruise phase of flight for those new aircraft types. Without the availability of the empirical accident data of these aircraft, however, a validation of the conceptual model is not possible. For the purpose of comparison of different future operation concepts and different scenarios in a metropolitan area the model suffices the need. Two examples of operation concepts and traffic scenarios for PAV and UAV aircraft movements, respectively, are demonstrated.

The Transition Towards Free Flight: A Human Factors Evaluation of Mixed Equipage, Integrated Air-Ground, Free Flight ATM Scenarios

This paper describes the initial results of a simulation experiment in which the human factors implications of three Mixed Equipage, Integrated Air-Ground, Free Flight Air Traffic Management (ATM) scenarios were investigated. The experiment primarily addressed how to accommodate a fleet of mixed equipped aircraft, with and without Airborne Separation Assurance System (ASAS), in a transitional free flight era in which both air and ground players have defined responsibilities. All three transitional ATM operational concepts evaluated, were designed with the idea that equipping aircraft should be immediately beneficial to the airlines.

Taxonomy of Conflict Detection and Resolution Approaches for Unmanned Aerial Vehicle in an Integrated Airspace

This paper proposes a taxonomy of conflict detection and resolution (CD&R) approaches for operating unmanned aerial vehicles (UAVs) in an integrated airspace. Possible approaches for UAVs are surveyed and broken down based on their types of surveillance, coordination, maneuvering, and autonomy. The factors are combined back selectively, with regard to their feasibility for operation in an integrated airspace, into several “generic approaches” that form the CD&R taxonomy. These generic approaches are then attributed to a number of available methods in the literature to determine their position in the overall CD&R scheme. The attribution shows that many proposed methods are actually unsuitable for operation in an integrated airspace. Furthermore, some part of the taxonomy does not have an adequate representative in the literature, suggesting the need to concentrate UAV CD&R research more in those particular parts. Finally, a multilayered CD&R architecture is built from the taxonomy, implementing the concept of defense in depth to ensure safe operation of UAVs in an integrated civil airspace.

Three-Dimensional Velocity Obstacle Method for Uncoordinated Avoidance Maneuvers of Unmanned Aerial Vehicles

This paper proposes a novel avoidance method called the three-dimensional velocity obstacle method. The method is designed for unmanned aerial vehicle applications, in particular to autonomously handle uncoordinated multiple encounters in an integrated airspace, by exploiting the limited space in a three-dimensional manner. The method is a three-dimensional extension of the velocity obstacle method that can reactively generate an avoidance maneuver by changing the vehicle velocity vector based on the encounter geometry. Adverse maneuvers of the obstacle are anticipated by introducing the concept of a buffer velocity set, which ensures that the ownship will diverge with sufficient space in case of sudden imminence. A three-dimensional resolution is generated by choosing the right plane for avoidance, in which the unmanned aerial vehicle conducts a pure turning maneuver. Implementation of the three-dimensional velocity obstacle method is tested in several simulations that demonstrate its capability to resol...

Three-dimensional velocity obstacle method for UAV deconflicting maneuvers

Autonomous systems are required in order to enable UAVs to conduct self-separation and collision avoidance, especially for flights within the civil airspace system. A method called the Velocity Obstacle Method can provide the necessary situational awareness for UAVs in a dynamic environment, and can help to generate a deconflicting maneuver.This paper focuses on the assessment of the Velocity Obstacle Method application and its ability to resolve various conflict situations in three dimensional space. This assessment results in a redefinition of the criteria of avoidance. A novel technique is introduced to support the avoidance decision, by representing the conflict situation in various avoidance-planes. Several new definitions to support the method are introduced. This method is then implemented in three-dimensional simulations for UAVs in cases of conflict, in which more than one option of resolution is provided.

Man-in-the-loop part of a study looking at a free flight concept

The paper describes the man-in-the-loop part of a study looking at a free flight concept with detection and resolution of conflicts during cruise flight by means of airborne systems. The overall study included fast-time simulations to define a base-line concept, a safety analysis, and a man-in-the-loop simulator experiment to investigate human factors issues. Part of the human factors study was the integration of traffic information, conflict detection and conflict resolution advisories in the displays. Based on the results of the three sub-studies, the feasibility of the free flight concept as defined in this study, could not be refuted.

Aircraft Performance for Open Air Traffic Simulations

The BlueSky Open Air Traffic Simulator developed by the Control \& Simulation section of TU Delft aims at supporting research for analysing Air Traffic Management concepts by providing an open source simulation platform. The goal of this study was to complement BlueSky with aircraft performance models in order to enable performance-related Air Traffic Management studies. The aircraft performance model developed within this work consists of a kinetic Flight Dynamics Model, which stores the required performance characteristics in a database with type-specific aircraft and engine coefficients. Currently, sixteen commercial turbofan and turboprop aircraft from different range and weight categories are represented. To evaluate the quality of the aircraft performance model, its outputs were compared to results from literature as well as from real flights. It was found that the applied methodologies for the determination of aircraft performance accurately model high-speed drag polars as well as fuel consumption for cruising and taxiing aircraft. The fuel consumption model of climbing and descending aircraft, however, leaves room for improvement. Possible strategies for obtaining a more precise estimation of fuel burn over the entire flight are recommended based on the results of this study. With this work, the BlueSky Open Air Traffic Simulator considers individual aircraft performance. This is an important step in the creation of an open simulation platform for Air Traffic Management research.