Pedro J. Boschetti

Stability and Performance of a Light Unmanned Airplane in Ground Effect

The objective of the present work is to understand the effect of ground proximity on the aerodynamic performance and stability of a light unmanned aerial vehicle. The flowfield around the airplane was computed by PAN AIR and Athena Vortex Lattice. The ground effect was simulated using the method of images. The stability coefficients and other aerodynamic characteristics were obtained at different heights above ground and in free flight. The results demonstrate that the airplane is lateral-directional statically stable, longitudinal statically stable in free flight and longitudinal statically unstable in ground effect. The dynamic stability characteristics of the airplane were obtained at different heights above ground. The phugoid mode is considerable influenced by ground effect and a divergent and non-oscillatory mode appears when the airplane is near to the ground. This is called non-dimensional height mode. The short-period, the Dutch roll, the roll and the spiral modes are slightly affected by ground effect. Significant differences were obtained when the z derivatives were neglected in the dynamic analysis for longitudinal motion. The present work demonstrates that the performance and stability of the unmanned airplane are considerably influenced by ground effect.

Design of an Unmanned Aerial Vehicle for Ecological Conservation

§The exploitation of petroleum can cause serious environment problems when oil leakages occur on the marine or lake surfaces. The constant vigilance over exploitation areas helps to minimize the adverse impact of such accidents by means of early detection. This article deals with the activities carried out at present in order to create an unmanned aerial vehicle designed to patrol the petroleum exploitation zones. Among these activities the preliminary design of the aircraft, the structural design of a prototype capable of accomplishing the assigned mission, and the aerodynamic optimization of such a design, are worth mentioning. A monoplane airplane, twin-boom configuration airplane, with a partially metallic structure was designed. The aerodynamic optimization process was realized applying theoretical and experimental methods. In conclusion, the designed vehicle will prove to be satisfactory for the mission for which it was created, and to be used as a tool for future research.

Increasing the Lift-Drag Ratio of an Unmanned Aerial Vehicle Using Local Twist

Recently published works predict that any planform shape may be optimized with twist to reduce the induced drag to an optimum value. When the twist is applied along the span of the airplane, the lift-drag ratio is lower than that with no twist. This can be corrected if twist is applied only in a specific portion of the span. The objective of this paper is to demonstrate that the local twist increases the lift-drag ratio using two different inviscid computational fluid dynamics codes and to describe the method employed to obtain the twist start line to increase the lift-drag ratio. The method was applied to an unmanned aerial vehicle designed for the early detection of oil leakages in the extraction areas, and a variation of 8 cm in the wing tip was obtained. The results show that the lift-drag ratio of the twisted wing is higher than that with no twist in conditions close to cruise flight. The lift-drag ratio increased 2.89 and 0.31%, estimated by Multhopps method and by the vortex-lattice method, respectively. The results demonstrate that the local twist may increase the lift-drag ratio when it is applied in the way explained in the present paper.

Stability and Flying Qualities of an Unmanned Airplane Using the Vortex-Lattice Method

The purpose of the present work is to evaluat e the static stability and open loop dynamic stability for un power ed condition of the Unmanned Aerial Vehicle for Ecological Conservation. Forces and moments were obtained by the vortex lattice method. These were computed for different values of angle of a ttack, sideslip angle, aileron, rudder and elevator deflection, and pitch, yaw and roll rates. Static stability and control derivatives were obtained and used for the analysis of airplane open loop dynamic stability and response. The longitudinal and later al –directional derivates show that the airplane is statically stable. The short period mode and phugoid mode correspond with damped mode. Dutch roll mode and roll mode of the airplane matches with damped mode and convergent mode, respectively. However, spi ral mode re spo nse prediction corresponds to a divergent mode. The airplane reaches flying qualities equal and better than those of Level 2

Ground Effect on the Longitudinal Stability of an Unmanned Airplane

Universidad Simon Bolivar, Naiguata, Edo. Vargas, 1160, Venezuela The objective of the present study is to analyze the effect of ground proximity on the longitudinal stability of the Unmanned Airplane for Ecological Conservation (ANCE). First, the original system of equations that describes the effect of variations of vertical distance was modified in order to consider the influence of ground proximity on the airplane at small angles of attack. The stability coefficients at different heights were computed using the low–order panel code CMARC. Then, the static characteristics were estimated, and a dynamic analysis was performed. The implication of the h derivatives on the aircraft dynamic stability was studied by writing two groups of equations of motion, one includes the h derivatives, and the other one assumes these ones equal to zero. The eigenvalues for each case were calculated at different heights above ground. It can be concluded that the h derivatives have a strong influence on the longitudinal dynamic stability in ground effect, and it would be a mistake to consider only the stability coefficients at a given height to study the dynamic stability of an aircraft in ground effect neglecting the h derivatives.

Dynamic Ground Effect on the Longitudinal Stability of Airplanes during the Landing

The objective of the work presented herein is to study the influence of dynamic ground effect on the longitudinal stability of airplanes during un-power landing by numerical simulation. A method was developed to design a landing control system which considers dynamic ground effect by the inclusion of the h derivatives in the longitudinal equations of motion. A case study was presented to illustrate with an example the influence of dynamic ground effect on the longitudinal stability using the Unmanned Airplane for Ecological Conservation. Open-loop flight simulations were performed considering dynamic ground effect using a program written in FORTRAN language. When the vehicle achieved heights lower than 2.5935 m during the simulations, an unstable response appears. A landing control system was designed using the methodology presented in this paper, and close-loop simulations were completed using a model created in Simulink. The control system drove the airplane to the runway, only when the h derivatives were included in the equations of motion. The unstable response produced by the dynamic ground effect has a strong influence in the flare manoeuvre, and for this reason, in the design of a landing control system, the h derivatives must be included in the longitudinal equations of motion.

Aerodynamic Analysis of the Unmanned Aerial Vehicle for Ecological Conservation

The present work has as objective to do a comple te aerodynamic analysis of the Unmanned Aerial Vehicle for Ecological Conservation. The panel method code PAN AIR is used to compute the inviscid flowfield. The viscous effects in drag are estimated by the classic Hoerner method, and the maximum lift coeff icient via the classic Valarezo and Chin method. The numerical aerodynamic forces of the complete airplane are compared to experimental data for validation. The spanload and wing pressure distribution are estimated for four configurations: wing, wing -body, wing -body -tail, and wing -body -tail with wing twist. The sources of induced drag for all configurations are achieved graphically via Trefftz plane. All the data were estimated at cruise flight, Reynolds number equal to 1.413×10 6

Linear Computational Fluid Dynamic Analysis of Dynamic Ground Effect of a Wing in Sink and Flare Maneuvers

A numerical investigation has been conducted to analyze the influence of the dynamic ground effect on the aerodynamic characteristics of a rectangular wing. The numerical model is based on a three-dimensional panel method and the ground effect is analyzed using the method of images. Before simulating the wing approaching the ground, the model developed was tested assuming fixed height and the results were examined by comparison to analytical and numerical results showing a good agreement. Then, the dynamic ground effect was investigated for two flight conditions: constant rate of descent and varying rate of descent. The results obtained by dynamic ground effect and those ones computed using static ground effect were compared evidencing that the static ground effect underpredicts the lift coefficient and overpredicts the induced drag coefficient. In addition, for these flight conditions, the lift coefficient increases when non-dimensional height decreases observing that it is more significant for a constant value of rate of descent, and the induced drag coefficient decreases while non-dimensional height reduces evidencing a significant decrease for a varying rate of descent. Finally, the effect of the flight path angle was evaluated demonstrating that the lift and the induced drag coefficients decrease with more negative flight path.

Aerodynamic Performance as a Function of Local Twist in an Unmanned Airplane

Recently published works predict that any planform shape may be optimized with twist to reduce the induced drag to an optimum value. The objective of this paper is to observe how the distance between the wing root and the twist start line is linked to the maximum lift –drag ratio and to the maximum lift co efficient on an unmanned aerial vehicle designed for the early detection of oil leakages in the extraction areas. The aerodynamic analysis was performed using a panel code to compute the inviscid flowfield, a viscous drag built to estimate the viscous drag , and the pressure difference rule to calculate the maximum lift coefficient. The results show that the maximum lift –drag ratio increases and the maximum lift coefficient reduces as the distance between the wing root and the twist start line decreases. The lift –drag ratio increases 1.51%, and the maximum lift coefficient decreases 3.55% respect to the value for the untwisted airplane. The twist start line was placed at 0.815 m as the greatest lift –drag ratio augmentation is located at this station. The res ults demonstrate that the maximum lift –drag ratio and the maximum lift coefficient are linked to the distance between the wing root and the twist start line.

Dynamic Ground Effect on the Aerodynamic Coefficients of a Wing using a Panel Method

A numerical investigation has been developed to evaluate the influence of dynamic ground effect on the aerodynamic coefficients of a wing using a panel method. This simulates unsteady flow by the time-marching method with a deformable free wake. The image method is used to model ground effect. Lift, induced drag, and pitching moment coefficients were obtained considering fixed height above the ground (static ground effect) and the wing in sink and flare maneuvers (dynamic ground effect). The results at static ground effect were compared with analytical and numerical results in order to verify and validate the created panel code, and they are acceptable. Lift and the absolute value of the pitching moment coefficients increase and the induced drag coefficient decreases as the height diminishes. Although the trends in static and dynamic ground effect are similar, the aerodynamic coefficients achieved in static ground effect are less affected than those ones calculated by simulations of the wing approaching the ground. Linear models of the wing in ground effect were developed by using the data of constant rate of descent and flare maneuvers. The sink rate produces significant variations in the aerodynamic coefficients of a wing.