Search Results

The availability of new technologies and the growing interest in the development of autonomous aircraft has created a demand for performance evaluation of aircraft flying at high altitudes over a long period of time for applications such as monitoring, telecommunications, etc. This work presents a study on the use of wings with high aspect ratio for the application in unmanned aircraft, that fly at high altitudes and require great endurance to remain flying as long as possible. With reference to the AeroVironment Helios aircraft, which hit the altitude record in 2001, flying at more than 29,000 meters altitude, a comparison was made between five wings with different wingspan from the aerodynamic and structural point of view. The aerodynamic performance of each wing was calculated and structural design and sizing was performed, assuming that it is the main structural component of the wing.

In this paper it is presented an analysis of the longitudinal and lateral-directional stability characteristics of paragliders. The paragliders stability analysis is part of the thesis named “Paragliders Flight Dynamics”, submitted to the Department of Mechanical Engineering of the Federal University of Minas Gerais (UFMG) - Brazil - in partial fulfillment of the requirements to obtain the master's degree in mechanical engineering. The full thesis presents a complete theoretical analysis of paragliders flight dynamics providing useful information for paragliders conceptual design optimization, and representing a first initiative to incentivize the international aeronautical engineering community to dedicate attention to this particular field.

The need of mass reduction of automotive engines, aiming at greater performance of the vehicle and cost reductions, demands the research for optimized forms of all its components. The mass minimization of all parts of the engine is not limited only to the optimization of the mechanical project of the part in itself. A part with less weight or volume, saves used material, makes it possible to increase the part production, it facilitates transportation, and, therefore, allows reducing the final cost of the part throughout all its productive chain. In this work the method of Topological Optimization (TO) was applied to project a new geometry, using cast iron, for the alternator and air conditioner compressor bracket of an automotive engine, originally in aluminum. Two geometries had been proposed: one where it is considered manufacture process and another one where it is not considered. The last one was used as step for the optimization of final geometry.

This paper presents a theoretical model for the analysis of the longitudinal static stability and control of biplane aircrafts that take into account some effects neglected by the classical approach based on the concept of an aerodynamically equivalent monoplane. Adopting a different approach, the present study considers individually the effects of lift and drag of each wing and the influence of the horizontal tail drag. The study includes the determination of neutral and maneuver points under free and fixed stick conditions and the influence of them over aircraft longitudinal control. Through a practical example, it's shown that, depending on aircraft geometry, an analysis based on the present study can lead to results very different of that furnished by the equivalent monoplane analysis.

Pressure is always a crucial measure in experimental aerodynamics. There are many ways of measuring pressure and nowadays methods that allow integration to computers are preferred. The objective of this paper is to present the development and construction of a full functional displacement capacitive sensor for measuring dynamic pressure by adapting conventional U manometers. The development of the sensor was made low cost and yet presents a fair precision. Experimental data are presented. The sensor is intended to be equipped in the CEA's (Centro de Estudos Aeronáuticos) wind tunnel located in Belo Horizonte (MG).

In this paper, it is developed a descriptive theory of paraglider flight mechanics, a gliding aircraft designed for entertainment purposes. After the analytical representation of the equipment geometry, the equations of longitudinal motion are derived and the most relevant parameters of performance and stability are identified. The developed theory is tried out based on real gliders analysis showing consistent results. The theoretical results here presented about paraglider flight mechanics can not be found in the available bibliography. It's expected that a scientific approaching of the paraglider stability and performance, as a branch in the aeronautic engineering field enables relevant improvements on flying and safety characteristics of these unconventional aircrafts.

This paper presents the development of equations needed to longitudinal stability and control calculus for all-flying tail aircrafts. All-flying tails, although unusual, have been used in some aircrafts since the beginnings of aviation. Nevertheless, don’t have in the literature any specific text showing the equations for longitudinal stability and control calculus adapted to this kind of tail. The development in this paper follows a classic approach adapted to the present case furnishing the expressions needed to determinate the neutral points and maneuver points, as well the equilibrium tail-angle and force curves for longitudinal horizontal flight and maneuvers.

The present paper presents a method for the numerical determination of control laws for aircrafts needed for optimization of a pre-established maneuver, applied to a take-off under requirements of FAR-Part 23. The methodology is based on the minimization of penalty functions through of mathematical programming algorithms with numerical integration of the aircraft equations of motion. With the optimum control law it is possible to elaborate efficient strategies for automatic flight control and for orientation of piloted flights. Numerical aspects of the application of this procedure are discussed, these being important for their adequate performance. Results are obtained for the optimization of the take-off distance of a tail-wheel airplane and are compared with the take-off distance obtained by manual control.

This paper present the instrumentation procedure used in order to determine the performance, stability and control characteristics of the light aircraft CEA-205 CB-9 Curumim. The instrumentation used is: i) autonomous acquisition system using micro controllers; ii) solid state inertial platform; iii) pitot probe; iv) attack and sideslip angle indicators; v) potentiometer on control system; vi) load cell on control system; vii) propeller tachometer; viii) barometer; ix) thermometer and x) GPS. Assembly and calibration detail procedures are presented with some results obtained on typical maneuvers. This work, in development on the Center for Aeronautical Studies of Federal University of Minas Gerais (CEA/UFMG) and on the Department of Aeronautical Engineering of Naples University (DPA), intend to assembly a system in order to perform low cost flight tests on light aircrafts.

This paper presents a numerical process for determination of optimal flight paths for competition soaring. The issue is reduction of flight time in order to soar towards an ascending thermal and climb, through thermal flying, to the initial altitude. The optimization procedure consists in the application of a Direct Method in order to obtain suboptimal solutions through parameterization of state variables, unlike a previous study by the same authors which was based on control parameterization. A mathematical programming procedure is used in order to determine the sub-optimal values for the parameterized state variables. The optimal control law, which is necessary for the generation of the sub-optimal state, is obtained through a step by step penalty technique. The obtained results demonstrate that the optimization of transitory phases is important for the minimization of total flight time.

In this work, sailplane symmetrical motion equations including pitch motion controlled by elevator angle are presented. The following effects are especially taken into consideration: i) tail damping due to pitch motion; ii) air density variation according to altitude; iii) presence of vertical and horizontal atmospheric air motions, and iv) non-linearity of CL ′ a curve near stall angle. The mathematical modeling includes the construction of an objective function for competition flight optimization. Making use of the concept of state variables, the minimum time trajectory problem is formulated as an optimal control problem with state constraints. Using simplified control laws and a mathematical programming algorithm, suboptimal trajectories are obtained for the sailplane PIK-20B.

Using a Simple Genetic Algorithm, the present paper obtains the optimal geometry of a cam with roll follower. In order to evaluate cam performance, an objective function which takes into account the influence of the inertia, the perimeter and of the pressure angle is proposed. The choice for a Genetic Algorithm is justified because, in preliminary tests, the objective function had proven to be multimodal