Xavier Prats

Requirements, Issues, and Challenges for Sense and Avoid in Unmanned Aircraft Systems

The sense and avoid capability is one of the greatest challenges that has to be addressed to safely integrate unmanned aircraft systems into civil and nonsegregated airspace. This paper gives a review of existing regulations, recommended practices, and standards in sense and avoid for unmanned aircraft systems. Gaps and issues are identified, as are the different factors that are likely to affect actual sense and avoid requirements. It is found that the operational environment (flight altitude, meteorological conditions, and class of airspace) plays an important role when determining the type of flying hazards that the unmanned aircraft system might encounter. In addition, the automation level and the data-link architecture of the unmanned aircraft system are key factors that will definitely determine the sense and avoid system requirements. Tactical unmanned aircraft, performing similar missions to general aviation, are found to be the most challenging systems from an sense and avoid point of view, and further research and development efforts are still needed before their seamless integration into nonsegregated airspace

Increasing UAV capabilities through autopilot and flight plan abstraction

This paper presents two novel avionics subsystems that aim at overcoming two clearly identified drawbacks of current UAV technology. Firstly, on board exploitation of autopilot telemetry is a complex and autopilot dependent task. Secondly, the flight plan definition mechanism available in most autopilots is just a collection of waypoints. This approach has several limitations, among them its inability to allow interaction between the flight plan and the mission in progress. The Flight Control System Gateway is a component designed to facilitate exploitation of data obtained from the autopilot. It provides a hardware-independent interface that isolates payload components from the autopilot specificities, thus eliminating dependencies on a particular autopilot solution. The Flight Plan Manager is a subsystem that interacts with the FCS Gateway in order to direct the flight of the UAV. It follows a flight plan described via a novel specification mechanism and sends commands to the FCS Gateway for its execution. The specification formalism improves on current mechanisms by introducing higher level constructs and enabling interaction with other payload components. These subsystems are integrated into an overall avionics solution which is based on an innovative publish/subscribe service based software architecture and a LAN based distributed hardware architecture.

En Route Speed Reduction Concept for Absorbing Air Traffic Flow Management Delays

This paper proposes an en route speed reduction to complement current ground delay practices in air traffic flow management. Given a nominal cruise speed, there exists a bounded range of speeds that allows aircraft to fly slower with the same or lower fuel consumption than the nominal flight. Therefore, flight times are increased and delay can be partially performed in the air, at no extra fuel cost for the operator. This concept has been analyzed in an initial feasibility study, computing the maximum amount of delay that can be performed in the air in some representative flights. The impact on fuel consumption has been analyzed, and two scenarios are proposed: the flight fuel remains the same as in the nominal flight, and some extra fuel allowance is permitted in order to face uncertainties. Results show significant values of airborne delay that may be useful in many situations, with the exception of short hauls where airborne delay may be too short. If cruise altitude is changed, the amount of airborne delay increases, since changes in cruise speed modify the optimal flight altitudes. From the analyzed flights, a linear dependency is found relating the airborne delay with the amount of extra fuel allowance.

Equitable Aircraft Noise-Abatement Departure Procedures

This paper deals with the optimization of aircraft noise-abatement departure procedures. A multicriteria optimization strategy is presented, where the fairness of the optimal trajectories is assessed vis-a-vis the different noise-sensitive locations around the airport of study. This equitable optimization is formulated as the minimization of the maximum noise-annoyance deviation regarding all considered locations. This strategy is complemented with an iterative lexicographic optimization algorithm which, in turn, guarantees the Pareto efficiency condition of the final solution. Aircraft operating costs are also considered by neglecting the marginal benefits of noise reduction below a certain threshold value. An application example is shown (as an illustrative case) based on a departure of runway 02 at Girona airport in Catalonia, Spain. The results show the feasibility of this technique, which is intended to be used by procedure designers or airport authorities.

In-Flight Contingency Management for Unmanned Aerial Vehicles

Contingency analysis and reaction is a critical task to be carried out by any airplane to guarantee its safe operation in a non-segregated airspace. Pilot’s reactions to any kind of incidences that may occur in-flight, like engine malfunctions, loss of electrical power, hydraulic failure, unexpected weather, etc, will determine the fate of the flight. Nowadays, contingency reactions are mainly driven by the airplane manufacturer, with pre-analyzed contingency scenarios covered in the airplane documentation, and by ICAO’s rules as defined in the way flight plans should be prepared and landing alternatives implemented. Flight dispatching is the set of tasks related to flight preparation, such as load and balance, meteorology study and briefing, operational flight planning, contingency analysis and planning, etc. However, managing contingencies on a UAS is a much more complex problem basically due to the automated nature of the vehicle and the lack of situational awareness that pilot’s in command should face. It is well known from the short history of UAS accidents that many of them are directly imputable to pilot errors when trying to manage an unexpected contingency. In this paper we will introduce an structured approach to automate contingency reactions in UAS. Our objective is to classify the contingency sources and up to a certain level abstract their impact on the system operation. Contingencies can be related to four wide aspects of the UAS operation: the flight itself, the mission, the payload, and the awareness systems. depending on the level of severity the contingency reaction may involve changing or canceling mission objectives to canceling the flight itself. In this way, the response to the contingency can be selected from a predefined limited catalog of automated reactions that may reconfigure the UAS operation in all aspects. This structured approximation is only possible because the contingency management is built upon a highly capable architecture called USAL (UAS Service Abstraction Layer) that offers capabilities to properly monitor contingencies and the flexibility to command pre-planned contingency reactions that may affect the flight operation and/or the mission carried out by the system. Contingency management becomes directly dependent upon the UAS dispatching process. USAL provides a dispatching methodology that identified the mission objectives, the UAV airframe and its various characteristics, the software services required for managing the flight and the mission, the sensor and computational payload, etc. All these elements are combined together in an iterative dispatching flow. The result of the process is the actual UAS configuration in terms of fuel, electrical system, payload configuration, flight plan, etc; but also detailed flight plan, alternative routes and landing sites, detailed USAL service architecture and the required contingency planning.

Flight Plan Specification and Management for Unmanned Aircraft Systems

This paper presents a new concept for specifying Unmanned Aircraft Systems (UAS) flight operations that aims at improving the waypoint based approach, found in most autopilot systems, by providing higher level fligh plan specification primitives. The proposed method borrows the leg and path terminator concepts used in Area Navigation1 (RNAV). Several RNAV leg types are adopted and extended with new ones for a better adaptation to UAS requirements. Extensions include the addition of control constructs that enable repetitive and conditional behavior, and also parametric legs that can be used to generate complex paths from a reduced number of parameters. The paper also covers the design and implementation of a software component that manages execution of the flight plan. To take advantage of current off-the-shelf flight control systems the constructs included in the flight plan are translated to waypoint navigation commands. In this way, the advanced capabilities provided by the flight plan specification language are implemented as a new layer on top of existing technologies. The benefits and the feasibility of the proposed approach for UAS flight plan management are demonstrated by means of a simulated mission that performs the flight inspection of Radio Navigation Aids.

An Assessment for UAS depart and approach operations

Unmanned Aerial Systems (UAS) have great potential to be used in a wide variety of civil applications such as environmental applications, emergency situations, surveillance tasks and more. The development of Flight Control Systems (FCS) coupled with the availability of other Commercial Off-The Shelf (COTS) components is enabling the introduction of UAS into the civil market. The sophistication of existing FCS is also making these systems accessible to end users with little aeronautics expertise. However, much work remains to be done to deliver systems that can be properly integrated in standard aeronautical procedures used by manned aviation. In previous research advances have been proposed in the flight plan capabilities by offering semantically much richer constructs than those present in most current UAS autopilots. The introduced flight plan is organized as a set of stages, each one corresponding to a different flight phase. Each stage contains a structured collection of legs inspired by current practices in Area Navigation (RNAV). However, the most critical parts of any flight, the depart and approach operations in an integrated airspace remain mostly unexplored. This paper introduces an assessment of both operations for UAS operating in VFR and IFR modes. Problems and potential solutions are proposed, as well as an automating strategy that should greatly reduce pilot workload. Although the

Model Rocket Workshop: A Project-Based Learning Experience for Engineering Students

A Project-Based Learning (PBL) experience for undergraduate students of aerospace engineering is described in this paper. The experience allows the students to build a model rocket using materials which can be easily obtained. They also compute all the relevant quantities to design and characterize the rocket and they test the robustness of their design. They furthermore launch the rocket with the corresponding payload and verify the flight parameters using an on-board altimeter. Finally, they also compare the flight parameters with the theoretically expected values. Using this simple scheme the students are later introduced in the simulation of complex flows, using standard techniques. We find that our students get rapidly involved in the project, allowing them to acquire several practical abilities, besides developing an accurate knowledge of the physics of rockets and of fluid dynamics.

Autopilot Abstraction and Standardization for Seamless Integration of Unmanned Aircraft System Applications

Nowadays many autopilot manufacturers are available in the commercial market for fixed wing small/mini Unmanned Aircraft System. Several autopilot configurations exist with a wide variety of selected sensors, sizes, control algorithms, and operational capabilities. However, selecting the right autopilot to be integrated in a given Unmanned Aircraft System is a complex task because none of them are mutually compatible. Moving from one autopilot to another may imply redesigning from scratch all the remaining avionics in the Unmanned Aircraft System. This paper presents the Virtual Autopilot System to facilitate exploitation of data obtained from the autopilot to be used by other applications on board. At the same time, it provides a hardware-independent interface that isolates payload and mission components from the autopilot specificities, thus eliminating dependencies on a particular autopilot solution. This subsystem is integrated into an Unmanned Aircraft System mission-oriented architecture called Unmanned Aircraft System Service Abstraction Layer, which promotes the development of automated concepts of operation keeping the Unmanned Aircraft System pilot fully under control. The VAS and its surrounding architecture have been implemented for a variety of autopilots, ranging from the commercial AP04 from UAV NAVIGATION, to the Paparazzi autopilot and even autopilots for ground-based vehicles. In all cases the selected Virtual Autopilot System interface was maintained, overall capabilities increased due to the flight-plan and mission-oriented perspective offered by the surrounding architecture, and development times exponentially reduced as the Virtual Autopilot System design is consolidated. This wealth of experimentation demonstrates that employing a standardized interface

Red-Eye: A Helicopter-based architecture for tactical wildfire monitoring strategies

T]his work introduces a flexible and reusable architecture designed to facilitate the development of remote sensing applications. Based on it, we are developing a helicopter system, called Red-Eye, devoted to the detection, control and analysis of wild land forest fires in the Mediterranean area. The design of the proposed system is composed of five main components. Each component will work collaboratively to constitute a platform of high added value. The general architecture designed for wildfire monitoring is being tailored for two relevant objectives within the particular Mediterranean scenario: tactical day/night fire front evolution, and post-fire hot-spot detection.