Aircraft Stability Derivatives Research Articles

Aerodynamic Stability Derivative Calculations Using the Compressible Source and Doublet Panel Method

This work presents the development of closed-form expressions for the aerodynamic stability derivatives of wings and aircraft flying at subsonic compressible conditions using the unsteady subsonic 3D source and doublet panel method (SDPM). The stability derivatives are obtained directly from the frequency domain version of the nonlinear unsteady subsonic Bernoulli equation and can be calculated for negligible additional computational cost around the true geometry of the wing or aircraft for each frequency of interest. The methodology is validated by applying it to an experimental test case of a swept wing oscillating in yaw and sideslip in the wind tunnel, demonstrating that the values of the aerodynamic stability derivatives obtained from the SDPM are in good agreement with the experimental data at low and moderate angles of attack. Then, the methodology is applied to a blended-wing–body unmanned aerial vehicle configuration and the SDPM stability derivative predictions are compared to estimates obtained from both steady computational fluid dynamics calculations and the USAF DATCOM methodology. It is shown that the SDPM approach is accurate and can yield more information about the stability of the aircraft than the DATCOM, given that the latter was developed for conventional aircraft configurations.

Numerical Evaluation of Aircraft Aerodynamic Static and Dynamic Stability Derivatives by a Mid-Fidelity Approach

The present study aimed to investigate the capability of mid-fidelity aerodynamic solvers in performing a preliminary evaluation of the static and dynamic stability derivatives of aircraft configurations in their design phase. In this work, the mid-fidelity aerodynamic solver DUST, which is based on the novel vortex particle method (VPM), was used to perform simulations of the static and dynamic motion conditions of the Stability And Control CONfiguration (SACCON): an unmanned combat aerial vehicle geometry developed by NATO’s Research and Technology Organisation (RTO), which is used as a benchmark test case in the literature for the evaluation of aircraft stability derivatives. Two different methods were exploited to extract the dynamic stability derivative values from the aerodynamic coefficient time histories that were calculated with DUST. The results for the mid-fidelity approach were in good agreement with the obtained experimental data, as well as with the results obtained using more demanding high-fidelity CFD simulations. This demonstrates its suitability when implemented in DUST for predicting the static and dynamic behavior of airloads in different conditions, as well as in reliably predicting the values of stability derivatives, with the advantage of requiring limited computational effort with respect to classical high-fidelity numerical approaches and the use of wind tunnel tests.

Wind Estimation Based on Estimation of Lateral-Directional Stability Derivatives of Aircraft

Wind Estimation Based on Estimation of Lateral-Directional Stability Derivatives of Aircraft

A Preliminary Study of Parameter Estimation for Fixed Wing Aircraft and High Endurability Parafoil Aerial Vehicle

High Endurability Aerial vehicle includes Airship, Powered parafoil aerial vehicle (PPAV). These flying aerial vehicles have excellent endurance and durability. Nowadays, research in lighter than air technology is pacing up fast. In the past years, the design and development of high endurable flying vehicle has grown due to their application in monitoring of floods/ drought, aerial photography, transportation, surveillance in terrain prone areas, reconnaissance missions etc. System Identification is a mathematical tool applied to develop mathematical model of any physical system based on measured data. Research on System Identification of these types of vehicles is on latest trends. Dynamic modelling of these types of vehicles is more complex than fixed wing aircraft. A detail Literature review in system Identification of PPAV and fixed wing aircraft is presented aiming to provide a source of information for researchers to make vehicle fully autonomous from manual controls. Various system Identification Techniques to estimate parameters of flying aerial vehicles are discussed. Longitudinal stability derivatives of fixed wing Hansa-3 aircraft and PPAV are compared. The methodology used in this study to estimate the longitudinal stability derivatives is ML Method. The results obtained in form of stability derivatives of Hansa-3 aircraft and Powered parafoil aerial vehicle are presented in tabular form. This study will give insight of identification techniques used to estimate parameters.

SVR-ND Method for Online Aerodynamic Parameter Estimation

Online aerodynamic parameter estimation plays an important role in compensating control system of aircraft under parameter uncertainties and unknown disturbance. In this paper, stability and control derivatives of aircraft are estimated online via support vector regression-numerical differential(SVR-ND) method. Small-sample real-time flight data reflecting real-time aerodynamic characteristics of aircraft is processed as training samples. For the small-size training samples, SVR technique is used for aerodynamic modeling. To pursue good performance in both computation efficiency and estimation accuracy, offline parameter estimation simulations are performed to select training sample size. It is observed that parameter estimation accuracy is related to the number of training samples and the noise level of samples. After that, an empirical formula is proposed to select training sample size according to results of simulations. To adapt the variation of samples, empirical formulas to tune hyper-parameters of SVR are presented based on the estimation of noise variance of samples. Finally, aerodynamic parameters are obtained by numerical differential in real-time. In a simulated maneuver, the proposed method is applied to online aerodynamic parameter estimation, and a Monte Carlo simulation is carried out to validate the robustness of SVR-ND method. Results indicate that the proposed method could realize accurate and robust estimation of aerodynamic parameters online.

New Systematic CFD Methods to Calculate Static and Single Dynamic Stability Derivatives of Aircraft

Several new systematic methods for high fidelity and reliability calculation of static and single dynamic derivatives are proposed in this paper. Angle of attack step response is used to obtain static derivative directly; then translation acceleration dynamic derivative and rotary dynamic derivative can be calculated by employing the step response motion of rate of the angle of attack and unsteady motion of pitching angular velocity step response, respectively. Longitudinal stability derivative calculations of SACCON UCAV are taken as test cases for validation. Numerical results of all cases achieve good agreement with reference values or experiments data from wind tunnel, which indicate that the proposed methods can be considered as new tools in the process of design and production of advanced aircrafts for their high efficiency and precision.

ANALYSIS OF STABILITY DERIVATIVES IMPORTANT TO RECOVERY FROM SPIN

This paper describes the numerical analysis of light aircraft stability derivatives in a wide range of angles of attack, important for recovery from spin. Stability derivatives versus angle of attack and sideslip were calculated using a CFD software, based on Euler equation combined with boundary layer equations. The analysis was performed up to the 40 deg of angle of attack and up to 25 deg of sideslip.

Design and aerodynamic analysis of a twin-engine commuter aircraft

The present paper deals with the preliminary design of a new general aviation Commuter 11 seat aircraft. The commuter aircraft market is today characterized by very few new models and the majority of aircraft in operation belonging to this category are older than 35 years. Tecnam Aircraft Industries and the Department of Industrial Engineering (DII) of the University of Naples “Federico II” have been deeply involved in the design of a new commuter aircraft that should be introduced in the market with very good opportunities of success. This paper aims to provide some guidelines on the conceptual design of this new twin-engine commuter aircraft. Aircraft configuration and cabin layout choices are shown and compared to similar solutions adopted by main competitors. The aerodynamic analyses are focused on some particular effects such as the wing–fuselage interference and the nacelle lift contribution and their effect on wing span loading. The aerodynamic analyses have been also essential to validate the preliminary estimation of aircraft stability and control derivatives (both longitudinal and lateral–directional) and to lead to a right sizing of tail surfaces. These analyses have been carried out through the use of a 3-D panel code. Finally some preliminary wind tunnel test results are presented.

Computing Stability Derivatives and Their Gradients for Aerodynamic Shape Optimization

Aerodynamic shape optimization of aircraft configurations often ignores stability considerations. To address this, a method for the computation of static, dynamic, and transient aircraft stability derivatives and their sensitivities for use in gradient-based optimization is introduced and evaluated. Computational fluid dynamics in the form of a three-dimensional structured-grid multiblock flow solver with both Euler and Reynolds-averaged Navier–Stokes equations is used. To compute the stability derivatives, a time-spectral formulation is used to compute an oscillating solution for the configuration of interest. From this oscillating solution, a series of linear regressions is performed to calculate the various stability derivatives. Because the solution is time dependent, it contains the information required to compute the transient, or “dot,” derivatives for the configuration. An adjoint method is used to compute the gradients of the stability derivatives of interest, enabling gradient-based stability-constrained aerodynamic shape optimization with respect to a large number of design variables. The computed stability derivatives are verified for an airfoil and validated for a generic unmanned combat aerial vehicle. The stability-constrained optimization of a wing demonstrates the viability and usefulness of the method for aircraft design optimization.

Measuring Aerodynamic Characteristics Using High Performance Low Speed Wind Tunnel at Universiti Teknologi Malaysia

This paper describes the capability and activities on utilizing a low speed wind tunnel facility at Universiti Teknologi Malaysia (UTM -LST) since its first operation in year 2001 till 2012. The laboratory is setup to meet the educational, research and industrial needs of Malaysia’s developing aero industry. The wind tunnel has high flow quality and can deliver speed up to 288 km/hr. UTM-LST has experiences on a wide range of testing such as aircraft, automotive, civil structure and building, ship and offshore structure. The wind tunnel is primarily equipped with flow visualization facility including Particle Image Velocimetry (PIV), pressure measurement, force measurements and Constant Temperature Anemometer (CTA). Most of the primary aerodynamic parameters can be measured in this facility such as measurement of aerodynamic lift and drag, static stability and control derivatives of aircraft. Measurement of automotive drag, down force and crosswind stability, and measurement of wind loads on civil structures. Correlation between wind tunnel measurements and numerical simulation using Computational Fluid Dynamics (CFD) are becoming more demanding especially related to unsteady aerodynamics. Currently, research related to unsteady aerodynamics such as helicopter rotor wakes, automotive wake turbulence and oscillating aerofoil are more demanding and requires upgrading to the current facility.

Computation of Aircraft Stability Derivatives Using an Automatic Differentiation Adjoint Approach

Computation of Aircraft Stability Derivatives Using an Automatic Differentiation Adjoint Approach

Stability, flying qualities and longitudinal parameter estimation of a twin-engine CS-23 certified light aircraft

This paper presents some results of the flight test campaign conducted on the Tecnam P2006T aircraft, on the occasion of its certification process. This twin-engine propeller airplane is certified under the normal category CS-23 and FAR 23. A prototype of this light aircraft has been tested in flight for a post-design performance optimization and for the assessment of flight qualities. These experiences have led to the application of two winglets to the original wing. The final configuration has been extensively tested for the achievement of CS-23 certification. The longitudinal and lateral-directional response modes have been assessed and quantified. At the same time the longitudinal airplane model, through a dedicated set of flight maneuvers, has been characterized by means of parameter estimation studies. The aircraft stability derivatives have been estimated from the acquired flight data using the identification technique known as Output Error Method (OEM). Some estimated stability derivatives have been also compared with the corresponding values extracted from leveled flight tests and from wind tunnel tests performed on a scaled model of the aircraft.

Unmanned aerial vehicle aerodynamic model identification from a racetrack manoeuvre

The determination of aircraft stability and control derivatives from wind-tunnel and computational fluid dynamics data can be an expensive and time-consuming procedure. This case study shows how linear system identification techniques can be used to obtain this information with sufficient accuracy to design a satisfactory flight control system for an aerial target of the Royal Thai Air Force. Just one flight was undertaken, using a racetrack manoeuvre, to provide the data for identification and validation. The system parameters were identified and a flight control system was designed. Hardware-in-the-loop simulation was used to perform initial tests on the controller and to test the control system hardware and software. A second flight was performed to test the resulting controller, and a satisfactory performance was obtained without the need to adjust the controller gains.

New methodology and code for Hawker 800XP aircraft stability derivatives calculation from geometrical data

AbstractThe new FDerivatives code was conceived and developed for calculating static and dynamic stability derivatives of an aircraft in the subsonic regime, based on its geometrical data. The code is robust and it uses geometries and flight conditions to calculate the aircraft’s stability derivatives. FDerivatives contains new algorithms and methods that have been added to DATCOM’s classical method, presented in a USAF Stability and Control DATCOM reference. The new code was written using MATLAB and has a complex structure which contains a graphical interface to facilitate the work of potential users. Results obtained with the new code were evaluated and validated with flight test data provided by CAE Inc. for the Hawker 800XP business aircraft.

Estimation of lateral-directional parameters using neural networks based modified delta method

AbstractThe aim of the study described herein was to develop and verify an efficient neural network based method for extracting aircraft stability and control derivatives from real flight data using feed-forward neural networks. The proposed method (Modified Delta method) draws its inspiration from feed forward neural network based the Delta method for estimating stability and control derivatives. The neural network is trained using differential variation of aircraft motion/control variables and coefficients as the network inputs and outputs respectively. For the purpose of parameter estimation, the trained neural network is presented with a suitably modified input file and the corresponding predicted output file of aerodynamic coefficients is obtained. An appropriate interpretation and manipulation of such input-output files yields the estimates of the parameter. The method is validated first on the simulated flight data using various combinations and types of real-flight control inputs and then on real flight data. A new technique is also proposed for validating the estimated parameters using feed-forward neural networks.

IMPROVED DELTA METHOD FOR PARAMETER ESTIMATION FROM REAL-FLIGHT DATA USING NEURAL NETWORKS

The aim of the study described herein was to develop and verify an efficient neural network based method for extracting aircraft stability and control derivatives from real flight data using feed-forward neural networks. The proposed improved Delta method (Modified Delta method) draws its inspiration from feed forward neural network based the Delta method for estimating stability and control derivatives. The method is validated first on the simulated flight data using real-flight control inputs and then on real flight data. A new technique is also proposed for validating the estimated parameters using feed-forward neural networks.

System Identification for Retrofit Reconfigurable Control of an F/A-18 Aircraft

We summarize a retrofit reconfiguration methodology that augments the production flight control system of an F/A-18 to compensate for changes in aircraft stability and control derivatives caused by aerodynamic control surface failures. The retrofit architecture relies on an indirect-adaptive model-following control approach that exploits onboard models of the closed-loop aircraft dynamics in the control computations. An output-error parameter identification process is used off-line to model the nominal behavior of the F/A-18 inner closedloop (airframe and baseline controller). The identified models are employed to describe the desired behavior for the controller and to provide regularization for an online parameter identification process. The online system identification algorithm updates the parameters of the models used for control decision, and a regularized recursive least-squares method is chosen to enable rapid adaptation to unforeseen failures and unmodeled dynamics while being robust to periods of low excitation. The retrofit reconfigurable controller was evaluated in high-fidelity F/A-18 simulations across a wide envelope of flight conditions with single and multiple control surface failures

Estimation of Stability and Control Derivatives of Light Canard Research Aircraft from Flight Data

In this paper, stability and control derivatives of light canard research aircraft generated through the flight test using parameter estimation technique has been presented. The maximum likelihood estimation, based on output-error minimisation technique, is used to estimate the derivatives from the aircraft response data. The validity of the estimates has been checked by the cross validation method, wherein the estimated model response is matched with the flight-test data that are not used for estimating the derivatives.

About the propeller influence on aircraft stability derivatives

AbstractPropellers can significantly effect aircraft flying characteristics and stability. Depending on the aircraft configuration this influence of propeller on aircraft stability derivatives can be more emphasized, as for example with single pusher propeller. Methods still used in prediction of propeller stability derivatives are based on blade element theory with the axial component of induced velocity determined from the classical propeller momentum theory. This could lead to uncorrect prediction of induced flow near the propeller and its wake. In presented paper propeller model and prediction of its influence on the aircraft stability derivatives is based on the propeller vortex theory. The numerical model is using discrete vortices to form vortex sheet that is leaving each propeller blade. This model is suitable for implementation in component build–up method used in prediction of propeller driven aircraft stability derivatives and it can be applicable for different aircraft configurations.

Predicting the Contribution of Running Propellers to Aircraft Stability Derivatives

Predicting the Contribution of Running Propellers to Aircraft Stability Derivatives