Agostino De Marco

Flight Tests, Performances and Flight Certification of a Twin-Engine Light Aircraft

This paper deals with flight test activities performed on P2006T, a twin-engine light aircraft recently designed and produced by Tecnam. Research activities and flight tests have been conducted during the flight certification of P2006T for the normal category under CS23. All the acquired data and flight results presented have been focused on both aircraft certification and on aircraft performances, stability and flight qualities measurement. The data have been acquired through a light, accurate and reliable flight instrumentation available at DIAS (Department of Aerospace Engineering). Some flight data about aircraft leveled speed, stall speed, climb characteristics and ground performances (take-off and landing) will be presented. After preliminary flight tests, winglets have been designed and added to the final configuration in order to obtain good climb performances also in OEI (One Engine Inoperative) conditions. Accurate stall tests have been performed in all configurations and influence of both entry-rate and load factor on stall speed have been highlighted. Excellent ground performances have been measured with short take-off and landing distances compared with similar airplanes. All measured flight performances can be considered very good for this aircraft category and have been used to demonstrate aircraft safety and to obtain CS23 certification.

A General Solution to the Aircraft Trim Problem

Trim defines conditions for both design and analysis based on aircraft models. In fact, we often define these analysis points more broadly than the conditions normally associated with trim conditions to facilitate that analysis or design. In simulations, these analysis points establish initial conditions comparable to flight conditions. Based on aerodynamic and propulsion systems models of an aircraft, trim analysis can be used to provide the data needed to define the operating envelope or the performance characteristics. Linear models are typically derived at trim points. Control systems are designed and evaluated at points defined by trim conditions. And these trim conditions provide us a starting point for comparing one model against another, one implementation of a model against another implementation of the same model, and the model to flight-derived data. In this paper we define what we mean by trim, examine a variety of trim conditions that have proved useful and derive the equations defining those trim conditions. Finally we present a general approach to trim through constrained minimization of a cost function based on the nonlinear, six-degree-of freedom state equations coupled with the aerodynamic and propulsion system models. We provide an example of how a trim algorithm is used with a simulation by showing an example from JSBSim.

Collaborative Aircraft Design Methodology using ADAS linked to CEASIOM

The aircraft design stages, conceptual and preliminary, are necessarily collaborative bytheir very nature. An example design carried out in this paper brings the collaborativeaspects of design to l ...

Progress on and Usage of the Open Source Flight Dynamics Model Software Library, JSBSim

JSBSim is an open source software (OSS) flight dynamics model that can be incorporated into a larger flight simulation architecture (such as FlightGear, or OpenEaagles). It can also be run as a standalone batch application when linked with a stub routine. Since 2004, when JSBSim was formally introduced at the Modeling and Simulation Technology conference, many advances have taken place, and a variety of uses have been demonstrated. This paper will present updates on project status, an overview of XML configuration file format enhancements, details on recent improvements and design choices, and some basic examples of use. A discussion about interfacing JSBSim with Matlab as a Mex-Function or Simulink S-Function is included, followed by a deeper look at a representative usage case study. I. Introduction JSBSim is a high-fidelity, 6-DoF (Degree-of-Freedom), general purpose, flight dynamics model software library written in the C++ programming languages. The library routines propagate the simulated state of an aircraft given inputs provided via a script or issued from a larger simulation application. The inputs can be processed through arbitrary flight control laws, with the outputs generated being used to control the aircraft. Aircraft control and other systems, engines, etc. are all defined in various files in a codified XML format. The library consists of approximately 70,000 text lines in 185 files. The total lines of program code is estimated at about 50,000 lines. Begun in 1997, JSBSim has an international team of active developers and user contributors. As a design goal, JSBSim has attempted to find a balance between high simulation fidelity and data file simplicity, so the task of simulating the flight of any aerospace vehicle can be done with the minimum specific input possible. Most code changes now are a result of minor code tweaks, or the addition of a few new features, as the user base provides inputs. The code has evolved in response to the way it is used, similar to natural selection. But, in some ways, development has shifted from compiled C++ code towards the creation of common XML data files. At the time of this writing, JSBSim is releasing candidate source code archives for version 1.0. The numbering of versions is somewhat arbitrary, but it signals – roughly – that the application has been used reliably for some time in a number of applications, that documentation 1 has reached a level where it is fairly thorough and useful, and the feature set is well defined and mature.

A Numerical Study on a Vertical-Axis Wind Turbine with Inclined Arms

This work focuses on a particular type of vertical-axis wind turbine, in which a number of inclined arms with airfoil-shaped cross-sections are mounted to connect the principal blades to their hub. While the majority of the known studies on vertical-axis turbines is devoted to the role of principal blades, in most of the cases without taking into account other parts of the wind turbine, the objective of this work is to investigate the effect of uncommon arm geometries, such as the inclined arms. The inclined arms are known to have a potentially beneficial role in the power extraction from the wind current but, due to the complexity of the phenomena, the investigation on aerodynamics of this type of turbine is often impossible through analytical models, such as blade-element momentum theory. It turns out that adequate studies can only be carried out by wind tunnel experiments or CFD simulations. This work presents a methodical CFD study on how inclined arms can be used on a selected wind turbine configuration to harvest additional power from the wind. The turbine configuration, geometry, and some fundamental definitions are introduced first. Then an in-depth CFD analysis is presented and discussed.

Harnessing marine current energy with tethered submerged systems: Experimental tests and numerical model analysis of an innovative concept

An innovative system concept in marine/river current technologies is presented. A floating submerged body is used as a support to turbines and a casing for electrical and control systems. A series of experimental test has been performed in a towing tank on a test model using already characterized turbines, in order to evaluate its behavior in response to current actions. The present paper is aimed to report the results of such tests and to obtain a simple dynamic model to compare with experimental results.

Development of a Java-Based Framework for Aircraft Preliminary Design and Optimization

T HEconceptual and preliminary design phases play a very important role for the development of the future transport aircraft. A computational framework capable of finding an optimal configuration satisfying several basic requirements would be an essential tool for industrial aircraft designers. Such software should be developed around all those basic principles and approaches to aircraft preliminary design well described in several textbooks on the subject [1–9]. Amodern preliminary aircraft design tool should be characterized by a certain level of accuracy and reliability (albeit using fast and simple semiempirical procedures), the capability to perform multidisciplinary analyses, and reasonably short computational times. Because of the particular relevance of production costs, noise, emissions,maintenance, andoperative costs in the commercial success of a transport aircraft, amodern software framework should be developedwith amultidisciplinary optimization (MDO) approach inmind.Another important aspect is the user-friendliness of the interface that should allow the user to interact with the design framework in an easy, fast, and efficient way. Of the same or even of more importance is the possibility to include in the software multiple fidelity analysis methods or to modify and develop new semi-empirical models to achieve better accuracy. It should also be possible to export the aircraft configuration geometry (e.g., as a CADmodel or a surface mesh) in one or more standard formats and to execute high-fidelity analyseswith external tools (e.g., computational fluid dynamics or Finite ElementMethod (FEM) solvers). Many aircraft design computational tools have been developed by several universities, companies, aeronautical industries, and research centers in the past and recent years [10–17]. In many recent papers [18–21], the importance of including a knowledge-based engineering approach in modern aircraft design tools is highlighted. The present note introduces the ongoing development of the Java Program Toolchain for Aircraft Design (JPAD), a Java-based desktop application for aircraft designers. The aim of JPAD, which eventually will be released as open-source software, is to provide a library and a set of companion tools based onmodern software technology as a support for typical preliminary design studies. The software has been conceived to be used in an industrial environment across conceptual and preliminary design phases. In these phases, a lot of different configurations have to be considered, and so the proposed software relies mostly on semi-empirical analysis methods and is capable to quickly provide results. A comprehensive study of the methods available in the literature has been first carried out to improve the accuracy of the results; each method has been tested against experimental data (produced in house or drawn from literature) so that statistical quantities (e.g., standard deviation) could be estimated either to find the best method currently available or to make a merger of different methods. The use of middleand high-fidelity methods (e.g., in aerodynamics, numerical lifting line, vortex lattice method, or computational fluid dynamics) is beneficial in preliminary studies, provided that their computational time is reasonably short. In this respect, the development of new semi-empirical methodologies or improved analysis approaches (especially for innovative aircraft configuration) is an important item that has been extensively reported in several recent works [21–26]. The aircraft design research group at the University of Naples has matured in the past two decades experience in design of light and turboprop transport aircraft [27,28]. Recent aircraft design activities carried out by the authors on a commuter 11-seat aircraft has been described and illustrated in some recent papers [29,30]. The matured know-how in aircraft aerodynamic designs has also found confirm through specific flight-testing research [31,32].

A 6DOF Flight Simulation Environment for General Aviation Aircraft with Control Loading Reproduction

This paper presents the main features of a six-degree-of-freedom (6DOF) flight simulation laboratory operated by the authors at the University of Naples. The aim of the flight simulator is twofold: serving as a research tool for model characterization and for the investigation of flying qualities of very-light and ultra-light aircraft; and offering a training options to the pilots of such airplanes. For these reasons the simulator cockpit has been conceived and set up as a generic cabin of a general aviation aircraft. The software suite that guides the various components of the system is based mainly on the features of FlightGear, an open-source flight simulation software. The simulation of aircraft motion, the cockpit instrument panel and flight controls, the outside scenery are all managed by a number of instances of FlightGear. All FlightGear instances are appropriately executed on different machines and communicate with each other via net protocols. Simulations are also supported by two other software modules. The first one controls the 6DOF motion of the cockpit. The second module implements a force reproduction system on the cockpit controls. An overview of all these modules is given in the paper, along with the discussion of the advantages and potentialities given by the source code accessibility and the high configurability of FlightGear. The force feedback model is particularly important to the purposes that this flight simulation facility has being designed for. To obtain an enhanced realism in piloting efforts, particular care has been taken to implement hinge moment equations in the simulation software. The result is a reliable closed-loop force-feedback system on all aircraft commands. Two useful and noteworthy generalizations have been implemented in this context: the effect of the mechanical linkage dynamics on the control surface motion and the effects on the control displacement due to the mechanical friction and to the presence of springs. The geometric, mass, inertia characteristics of each control surface and the hinge moment coefficients are managed by the control loading software. All the details of this model are given in the paper.

Game theory and evolutionary algorithms applied to MDO in the AGILE European project

In this paper, an optimization technique in aircraft design field, based on game theory and evolutionary algorithms to define the key variables for Multi-Disciplinary aircraft Optimization (MDO) into AGILE (Aircraft 3 Generation MDO for Innovative Collaboration of Heterogeneous Teams of Experts) European project, is presented. This work represents one of the contributions given by UniNa (University of Naples “Federico II”) research group within the AGILE project, which is coordinated by the DLR and funded by EU through the project HORIZON 2020 that aims to create an evolution of MDO, promoting a novel approach based on collaborative remote design and knowledge dissemination among various teams of experts. Since the aircraft design field is very complex in terms of number of involved variables and the dimension of the space of variation, it is not feasible to perform an optimization process on all the design parameters; this leads to the need to reduce the number of the parameters to the most significant ones. A multi-objective optimization approach allows many different variables, which could be a constraint or an objective function for the specific investigation; thus, setting the constraints and objectives to reach, it is possible to perform an optimization process and control which parameters significantly affect the final result. Within AGILE project, UniNa research group aims to perform wing optimization processes in a preliminary design stage, coupling Nash game theory (N) with typical genetic evolutionary algorithm (GA), reducing computational time and allowing a more realistic association among objective functions and variables, to identify the main ones that significantly affect final result and that consequently must be considered by the partners of the AGILE consortium to perform MDO in the final part of project, applying the proposed optimization technique to novel aircraft configuration.

Java framework for parametric aircraft design – ground performance

Purpose This paper aims to introduce the take-off and landing performance analysis modules of the software library named Java toolchain of Programs for Aircraft Design (JPAD), dedicated to the aircraft preliminary design. An overview of JPAD is also presented. Design/methodology/approach The calculation of the take-off and landing distances has been implemented using a simulation-based approach. This expects to solve an appropriate set of ordinary differential equations, which describes the aircraft equations of motion during all the take-off and landing phases. Tests upon two aircraft models (ATR72 and B747-100B) have been performed to compare the obtained output with the performance data retrieved from the related flight manuals. Findings The tool developed has proven to be very reliable and versatile, as it performs the calculation of the required performance with almost no computational effort and with a good accuracy, providing a less than the 5 per cent difference with respect to the statistical trend and a difference from the flight manual or public brochure data around 10 per cent. Originality/value The use of a simulation-based approach to have a more accurate estimation of the ground performance with respect to classic semi-empirical equations. Although performing the simulation of the aircraft motion, the approach shown is very time-saving and can be easily implemented in an optimization cycle.