Flight Dynamic Characteristics Research Articles

Analysis of flight dynamics for large-scale morphing aircraft

Purpose This paper aims to clarify the flight dynamics characteristics and improve the flight performance for large-scale morphing aircrafts. With specific focus on the effects of morphing on mass distribution, aerodynamics and flight stability, the study aims to develop the dynamic model, outline the morphing strategies design and evaluate the flight stability in transient stage of morphing.

Simulation Method for 3-D Wind Field over Complex Terrain with Asymmetrical Mountains

It is important for the research of flight characteristics to master the distribution of wind field and the character of turbulence intensity in a complex-terrain mountain. Based on the potential flow theories in fluid dynamics, a numerical simulation method of complex terrain including asymmetrical and symmetrical mountains has been developed in this paper. In particular, asymmetrical mountains are simulated by the combination of two transformed quarter-semiellipsoids. Furthermore, mountain-induced airflow is calculated based on potential flow theory, which could reflect the characteristic of wind field. As an example, the wind field near Dingling airport in Beijing has been simulated and analyzed by this method. The results demonstrate that this method is suitable and accurate for engineering practice, and also applicable for flight dynamics characteristics analysis of aircrafts.

Numerical Simulation on Flight Dynamic Characteristics of Elastic Wing Based on Gust Response

In this paper, the numerical method was developed to flight dynamics characteristics of elastic wing under the action of the discrete gust. In this numerical method, the aerodynamic forces of the elastic wing were calculated by solving the unsteady Navier Stokes equations, and incorporating the grid velocity method to simulating the gust response of the typical NACA0006 airfoil to the step changes in the angle of attack of aircraft . it is shown in results that the calculated lift responses of the airfoil agree well with both the exact theoretical value and calculated value in reference. the elastic effect was considered with RayleighRitz method, so that the fluid dynamic,structural dynamic and flight dynamic problems can be coupled to solve. and AGARD445.6 elastic wing for the numerical simulation of the flight characteristics.

Control Effectiveness Analysis of the hawkmoth Manduca sexta: a Multibody Dynamics Approach

This paper presents a control effectiveness analysis of the hawkmoth Manduca sexta. A multibody dynamic model of the insect that considers the time-varying inertia of two flapping wings is established, based on measurement data from the real hawkmoth. A six-degree-of-freedom (6-DOF) multibody flight dynamics simulation environment is used to analyze the effectiveness of the control variables defined in a wing kinematics function. The aerodynamics from complex wing flapping motions is estimated by a blade element approach, including translational and rotational force coefficients derived from relevant experimental studies. Control characteristics of flight dynamics with respect to the changes of three angular degrees of freedom (stroke positional, feathering, and deviation angle) of the wing kinematics are investigated. Results show that the symmetric (asymmetric) wing kinematics change of each wing only affects the longitudinal (lateral) flight forces and moments, which implies that the longitudinal and lateral flight controls are decoupled. However, there are coupling effects within each plane of motion. In the longitudinal plane, pitch and forward/backward motion controls are coupled; in the lateral plane, roll and side-translation motion controls are coupled.

주익이 손상된 전익형 무인기를 위한 신경회로망 적응제어기법에 관한 연구

무인항공기가 외형손상을 입는 경우, 비행역학 특성이 변하기 때문에 손상 이전 설계된 제어기는 더 이상 안정적인 제어성능을 보장하지 않는다. 본 논문에서는 주익의 손상이 일어난 무인항공기에 대해서도 강건한 제어성능을 보장하는 신경회로망 적응제어기법을 소개한다. 구동기의 특성에 의한 제어기의 성능저하를 방지하기 위해 Pseudo Control Hedging (PCH)를 추가적으로 사용하였다. 기체고정좌표계의 중심이 항공기의 무게중심에 위치하지 않는 비대칭 동역학을 사용하였으며, 전익형 무인기를 대상 비행체로 하였다. 날개가 손상되지 않은 모델과 손상된 모델의 풍동시험을 통해 얻은 공력데이터를 이용하여 시뮬레이션을 수행하였다. 시뮬레이션의 결과를 통해 제안된 제어기법이 주익의 손상이 발생한 항공기에 대해서도 여전히 안정적인 조종성능을 보장하는 제어기법임을 검증하였다. A damage imposed on an unmanned aerial vehicle changes the flight dynamic characteristics, and makes difficult for a conventional controller based on undamaged dynamics to stabilize the vehicle with damage. This paper presents a neural network based adaptive control method that guarantees stable control performance for an unmanned aerial vehicle even with damage on the main wing. Additionally, Pseudo Control Hedging (PCH) is combined to prevent control performance degradation by actuator characteristics. Asymmetric dynamic equations for an aircraft are chosen to describe motions of a vehicle with damage. Aerodynamic data from wind tunnel test for an undamaged model and a damaged model are used for numerical validation of the proposed control method. The numerical simulation has shown that the proposed control method has robust control performance in the presence of wing damage.

Analysis of partial wing damage on flying-wing unmanned air vehicle

This article investigates the effect of asymmetric wing damage on flight dynamic characteristics of a flying-wing single motor unmanned air vehicle. To construct a six degree-of-freedom model of the damaged aircraft, a flying-wing type unmanned aerial vehicle is designed, and the wind tunnel test for damaged configurations is performed to identify the change of aerodynamic coefficients. The changes of mass, center of gravity, and moment of inertia are also calculated for each damage configuration with CATIA. The changed trim states are calculated depending on the severity of damage, and the movements of poles in longitudinal/lateral-directional flight modes are examined to evaluate the change of the dynamic stability and performance. Numerical simulations and eigenvalue analyses are performed to investigate the altered flight dynamics. It is verified that an asymmetrically wing-damaged unmanned air vehicle shows a sluggish roll behavior with longitudinal instability, and the result of this study can be a cornerstone for the future research on reconfigurable flight controller design against aircraft damage.

Nonlinear Gust Response Analysis of Free Flexible Aircraft

Gust response analysis plays a very important role in large aircraft design. This paper presents a methodology for calculating the flight dynamic characteristics and gust response of free flexible aircraft. A multidisciplinary coupled numerical tool is developed to simulate detailed aircraft models undergoing arbitrary free flight motion in the time domain, by Computational Fluid Dynamics (CFD), Computational Structure Dynamics (CSD) and Computational Flight Mechanics (CFM) coupling. To achieve this objective, a structured, time-accurate flow- solver is coupled with a computational module solving the flight mechanics equations of motion and a structural mechanics code determining the structural deformations. A novel method to determine the trim state of flexible aircraft is also stated. First, the field velocity approach is validated, after the trim state is attained, gust responses for the one-minus-cosine gust profile are analyzed for the longitudinal motion of a slender-wing aircraft configuration with and without the consideration of structural deformation. RBA), while the second aims mainly to the analysis of elastic aircraft experiencing relatively small deformations. The idea to not consider cross-coupling effects between these two disciplines has been commonly justified by the large frequency separation of the characteristic motion which is typical of conventional structures. Nowadays, the focus on weight minimization for aircraft, leads toward more and more flexible vehicles. The resulting underlying structures may not exhibit the usual wide frequency separation among the rigid body degrees of freedom and the remaining elastic modes. So that the approach mentioned above can lead to mistakes/errors in analyses of flight performance, flying qualities, and control systems design. In these cases, an integrated analysis of flight mechanics and aeroelasticity is necessary from the very early stages of preliminary design (6).

Flight Dynamics Modeling and Analysis of Flexible Hypersonic Flight Vehicles

Facing the difficulty of flight dynamics modeling about flexible hypersonic flight vehicles, from view on the Lagrange’s equations based on dynamic first principle, this paper firstly developed kinetic energy and flexibility potential energy of the vehicle, then achieved concise flight dynamics equations by quasi-coordinates which could fully include coupling characteristics of flight dynamics, and lastly made necessary analysis about the equations. The result of study illustrates that flight dynamics equations of flexible hypersonic flight vehicles based on quasi-coordinates can satisfy the research of dynamics, stability, control,couplings and so on.

QTW 무인항공기의 종축 비행동역학에 관한 연구

본 논문에서는 고정익항공기와 회전익 항공기의 장점을 결합시킨 신개념 복합형 무인항공기인 QTW(Quad Tilt Wing)의 종축 동특성을 연구한 결과를 기술하였다. 설계된 QTW 무인항공기는 Tandem Wing 형상을 가지며 각 주익의 끝단에는 프로펠러를 구동하는 모터를 장착하였다. 비행역학적 분석을 위해 모멘텀 이론을 이용해 추력을 계산하였으며, 틸트 각도에 따른 프로펠러의 Slip stream에 의한 양력과 항력을 고려한 비선형 모델링을 구축하였다. 또한 트림분석을 통해 설계된 비행체가 적절한 비행속도 대비 틸팅각을 가짐을 보여주었으며, 각 트림 점에서의 성분별 힘을 분석하였다. 각 비행 모드의 선형모델 고유치 분석하여 동적 특성을 분석하였으며 고정익모드로 전환됨에 따라 안정한 부분으로 극점이 이동함을 확인하였다. A Quad Tilt Wing UAV is a new concept hybrid UAV having the advantages of both fixed-wing and rotary-wing aircraft. This paper presents longitudinal flight dynamic characteristics of a Quad Tilt Wing UAV. The designed Quad Tilt Wing UAV is a configuration of a tandem wing type aircraft with an actuating motor and propeller mounted at each wing. Momentum theory is used to calculate the thrust, and nonlinear modeling is performed considering lift and drag generated by slip stream effect of propellers. Also, Force and moment variation at each tilting angle is considered. Static trim on longitudinal axis is analyzed via numerical simulation. Componentwise force contribution was analyzed at each trim mode. Dynamic characteristics were evaluated through eigenvalue analysis for a linear model at each flight mode. It is verified that longitudinal dynamic characteristics are changing from unstable to stable state by continuous transition of dominant poles.

Longitudinal Flight Dynamics of a Single Tilt-wing Unmanned Aerial Vehicle

A single tilt-wing UAV has a new-concept hybrid configuration for adopting the advantages of both fixed-wing and rotary-wing aircraft. This paper presents longitudinal flight characteristics of the single tilt-wing UAV whose design is based on a tapered wing type aircraft with an actuating motor and a propeller mounted at each wing. Momentum theory is used to calculate thrust, and nonlinear modeling is performed considering lift and drag generated by slip stream effect of the propellers. Force and moment variation is considered for tilting angle change. Also, static trim on longitudinal axis is analyzed for operation airspeeds from 0 to 30m/s, and numerical simulation shows the flight dynamic characteristics of the UAV. It is verified that the single tilt-wing UAV has stable dynamic characteristics at fixed-wing mode.

Experimental study on the flight dynamics of a bioinspired ornithopter: free flight testing and wind tunnel testing

This study experimentally shows the flight dynamics of a bioinspired ornithopter using two different types of approach: (1) free flight testing, and (2) wind tunnel testing. An ornithopter is flown in straight and level flight with a fixed wingbeat frequency and tail elevation angle. A three-dimensional visual tracking system is applied to follow the retro-reflective markers on the ornithopter and record the flight trajectories. The unique oscillatory behavior of the body in the longitudinal plane is observed in the free flight testing and the detailed wing and tail deformations are also obtained. Based on the trim flight data, a specially devised tether device is designed and employed to emulate the free flight conditions in the wind tunnel. The tether device provides minimal mechanical interference and longitudinal flight dynamic characteristics similar to those of free flight. On introducing a pitching moment disturbance to the body, the oscillation recovered to the original trajectory turns out to be a stable limit-cycle oscillation (LCO). During the wind tunnel testing, the magnitude of LCO is effectively suppressed by active tail motion.

Measuring and Recording Systems Used in Flight Tests of Aircraft

Flight tests and measurements are usually performed for newly built or modernised aircraft utilised by the Polish Armed Forces. In the course of flight tests the airborne equipment is also investigated. The main goal of the performed tests is to verify tactical performance and to identify technical parameters of aircraft and/or equipment under examination. The airborne experimental data is also applied to the aircraft flight dynamics modelling, subsequently used for the design and construction of a flight simulator. The equipment is usually arranged of the following components: ̶ sensors/measuring devices capable of converting physical parameters into optical, mechanical, or electrical signals (indicators, transmitters, sensors, transducers); ̶ conditioning systems - intermediary devices used to amplify and/or adjust any signal gained to some required value or form; ̶ recording and storing devices (data recorders, cameras, etc.); ̶ devices applied to the decoding and processing of the acquired data (decoders, computers). Some selected problems of aircraft flight tests will be discussed in the paper. A brief description of the applied experimental apparatus will be provided first. Next, the attention will be focused on the experimentally gathered data utilised in the identification of aircraft flight dynamics characteristics and on the data applied to the evaluation of selected design parameters.

On the Benefits of In-Flight System Identificationfor Autonomous Airdrop Systems

A unique feature of airdrop systems is the inherent and large variability in flight dynamic characteristics. The same physical article dropped on two different occasions will exhibit significantly different dynamic response. The problem only becomes worse for different test articles. Control systems for autonomous airdrop systems explicitly or implicitly assume knowledge of the flight dynamic characteristics in some way, shape, or form. A question facing autonomous airdrop designers is whether to use precomputed dynamic characteristics inside the control law, or to compute the needed flight dynamic characteristics in-flight and subsequently employ them in the control law. This paper establishes conditions when in-flight identified characteristics, with a focus on the turn rate dynamics, should be used, and when it is better to use precomputed results. It is shown that with expected levels of system variability, sensor noise, and atmospheric wind, in-flight identification generally produces significantly more accurate dynamic behavior of the lateral dynamics than a precomputed model of the nominal system, even when the in-flight identification is performed with highly inaccurate sensor data. The only exception to this rule observed in this work is the situation where atmospheric winds are high and a direct heading measurement is not available. In this situation, a precomputed estimate of the time constant of the lateral dynamics is more accurate than an in-flight estimate. These conclusions are reached though a comprehensive simulation study using a validated airdrop flight dynamic model applied to both a small and large parafoil.

Hazardous Levels of Commercial Aircraft Response to Atmospheric Turbulence

Jet commercial aircraft in flight are frequently subject to atmospheric turbulence resulting in rapidly varying aerodynamic and flight dynamic characteristics. These varying characteristics not only pose threats to flight safety, but also may cause structural damages and reduce fatigue life. The sudden plunging motion in severe turbulence is the major reason to cause the flight injuries. To express the turbulence intensities as the hazardous levels, the root-mean-square g-load, usually for structural load, has been examined in the past twenty years. The present study is to examine alternative ideas to express the hazardous levels of sudden plunging motion in atmospheric turbulence. The flying-quality parameters of the plunging mode and integrated turbulence-induced downwash will be proposed as more reliable parameters for the turbulence hazard levels.

Navigation Aids Performance Evaluation for Precision Approaches

The paper deals with the evaluation of the expected performance of aircraft approaches and landings operated with different navigation systems, both traditional and satellite-based. Flight dynamics characteristics and control authority of the approaching aircraft are considered in order to obtain an overall manoeuvre evaluation. The technique from the presented analysis applies to different operative conditions, taking into account aircraft requirements, navigation systems features, and environmental constraints. The aim is to offer a tool to be used in the very preliminary design phase for system performance analysis in different scenarios, such as airport ground systems adoption and air traffic control requirements compliance; later, the same tool can be tuned to complement and direct the required real flight trials to validate an already fielded solution. A numerical code referring to the presented analytical model has been implemented and some applications concerning the system's performance evaluation and planning are proposed to illustrate the algorithm capabilities. The tool and the proposed analysis technique indeed are successful in providing a quantitative assessment of the differences among several possible approaches.

Flight Dynamics of High Aspect-Ratio Flying Wings: Effect of Large Trim Deformation

Analysis of flight dynamics of conventional airplane configurations usually begins with a rigid body approximation of the undeformed airplane structure. However, for high aspectratio flying wing configurations, static aeroelastic eects generate significant structural deformation and thus the aircraft configuration in flight is significantly dierent from the initial undeformed shape. As a consequence, flight dynamic studies conducted on a rigid body model based on the initial undeformed structure do not give an accurate assessment of the behavior of the airplane in flight. To overcome this, the deformed shape generated when the flying wing is subjected to static aeroelastic forces at trim, is used to define the rigid body configuration used for flight dynamic analysis. This paper studies the flight dynamic characteristics of the new rigid body configuration in relation to those of the rigid undeformed flying wing, and in relation to the stability characteristics of the complete aeroelastic model. The flight dynamic roots and the stability boundaries of the statically deformed rigid body configuration and the complete aeroelastic model are compared. It is found that staic aeroelatic deformation has a significant influence on the flight dynamic characteristics of high aspect-ratio HALE configurations.

Flight Dynamics of Highly Flexible Aircraft

An analysis and parametric study of the flight dynamics of highly flexible aircraft are presented. The analysis extends previous work of the authors, used to predict the atypical flight dynamic characteristics of highly flexible flying wings, to conventional configurations with one or more fuselages, wings, and/or tails. The aircraft structure is represented as a collection of geometrically exact, intrinsic beam elements, with continuity conditions enforced where beams intersect. The structural model is coupled with an aerodynamic model consisting of two-dimensional, large-angle-of-attack, unsteady theory for the lifting surfaces, and a fuselage model based on application of slender-body theory to a cylindrical beam. Influences of various design parameters such as wing flexibility, horizontal/vertical tail aerodynamics, and offset are investigated for aeroelasticity and flight dynamics of highly flexible aircraft. Results for prototype configurations illustrate the relationships between its design parameters and flight dynamic behavior.

Flight Dynamics of Highly Flexible Flying Wings

The paper presents a theory for flight-dynamic analysis of highly flexible configurations. The analysis takes into account large aircraft motion coupled with geometrically nonlinear structural deformation subject only to a restriction to small strain. A large motion aerodynamic loads model is integrated into the analysis. The analysis can be used for complete aircraft analysis including trim, stability analysis linearized about the trimmed-state, and nonlinear simulation. Results are generated for a typical high-aspect-ratio flying-wing configuration. The results indicate that the aircraft undergoes large deformation during trim. The flight-dynamic characteristics of the deformed aircraft are completely different as compared with a rigid aircraft. When the example aircraft is loaded sufficiently, the pair of complex-conjugate short-period roots merges to become two real roots, and the phugoid mode goes unstable. Furthermore, nonlinear flight simulation of the aircraft indicates that the phugoid instability leads to catastrophic consequences.

An investigation of the flight dynamic characteristics of gyroplanes by use of flight tests

AbstractAn analysis is presented both of flight test and simulation data obtained from a gyroplane aircraft. This class of rotary-wing vehicle has found limited application in areas other than recreational flying, however the accident rate has been such that it has prompted the study of the configuration’s stability and control characteristics. It is concluded that the flight dynamic response of the gyroplane examined is dominated by a fast, non-stable mode, affecting all states and thus increasing pilot workload. Simulation results indicate that the position of the centre of gravity significantly influences the stability of this mode.

Flight Loads and Dynamics of Flexible Air Vehicles

Based on the equations of motion of flexible air vehicles including rigid-body modes and elastic structural modes, and applying influence coefficients of linear aerodynamics, a set of equations are derived and a method is presented for analysis of flight loads and dynamic characteristics. The problems in the fields of flight mechanics and aeroelasticity such as static aeroelastic divergence, trim and deformation, aerodynamic loads distribution, flutter and flight dynamics can be solved by the procedure. An airplane with high aspect ratio wings is analyzed, and the results show that the coupling between rigid-body modes and elastic modes is distinct and should not be overlooked.