Dutch Roll Mode Research Articles

Application of virtual flight test framework with derivative design optimization

PurposeThe purpose of this paper is a development of a virtual flight test framework with derivative design optimization. Aircraft manufactures and engineers have been putting significant effort into the design process to lower the cost of development and time to a minimum. In terms of flight tests and aircraft certification, implementing simulation and virtual test techniques may be a sufficient method in achieving these goals. In addition to simulation and virtual test, a derivative design can be implemented to satisfy different market demands and technical changes while reducing development cost and time.Design/methodology/approachIn this paper, a derivative design optimization was applied to Expedition 350, a small piston engine powered aircraft developed by Found Aircraft in Canada. A derivative that changes the manned aircraft to an Unmanned Aerial Vehicle for payload delivery was considered. An optimum configuration was obtained while enhancing the endurance of the UAV. The multidisciplinary design optimization module of the framework represents the optimized configuration and additional parameters for the simulator. These values were implemented in the simulator and generated the aircraft model for simulation. Two aircraft models were generated for the flight test.FindingsThe optimization process delivered the UAV derivative of Expedition E350, and it had increased endurance up to 21.7 hours. The original and optimized models were implemented into virtual flight test. The cruise performance exhibited less than 10 per cent error on cruise performance between the original model and Pilots Operating Handbook (POH). The dynamic stability of original and optimized models was tested by checking Phugoid, short period, Dutch roll and spiral roll modes. Both models exhibited stable dynamic stability characteristics.Practical implicationsThe original Expedition 350 was generated to verify the accuracy of the simulation data by comparing its result with actual flight test data. The optimized model was generated to evaluate the optimization results. Ultimately, the virtual flight test framework with an aircraft derivative design was proposed in this research. The additional module for derivative design optimization was developed and its results were implemented to commercial off-the-shelf simulators.Originality/valueThis paper proposed the application of UAV derivative design optimization for the virtual flight test framework. The methodology included the optimization of UAV derivative utilizing MDO and virtual flight testing of an optimized result with a flight simulator.

Modeling and Closed Loop Flight Testing of a Fixed Wing Micro Air Vehicle.

This paper presents the nonlinear six degrees of freedom dynamic modeling of a fixed wing micro air vehicle. The static derivatives of the micro air vehicle are obtained through the wind tunnel testing. The propeller effects on the lift, drag, pitching moment and side force are quantified through wind tunnel testing. The dynamic derivatives are obtained through empirical relations available in the literature. The trim conditions are computed for a straight and constant altitude flight condition. The linearized longitudinal and lateral state space models are obtained about trim conditions. The variations in short period mode, phugoid mode, Dutch roll mode, roll subsidence mode and spiral mode with respect to different trim operating conditions is presented. A stabilizing static output feedback controller is designed using the obtained model. Successful closed loop flight trials are conducted with the static output feedback controller.

Effects of Gyroscopic Coupling and Countertorque in a Fixed-Wing Nano Air Vehicle

For the nonlinear equations of motion of the nano air vehicle, including the gyroscopic coupling and countertorque generated by the propulsion system, a linear state-space model is developed for analyzing the effects of gyroscopic coupling and countertorque on the dynamic behavior of the nano air vehicle. By analyzing the trajectories of eigenvector components obtained by increasing the gyroscopic coupling, it is shown that the different modes of the nano air vehicle influence both the lateral and longitudinal variables, thereby losing the conventional characteristics of these modes. The investigation shows that the stability of the coupled phugoid and coupled Dutch roll modes are improved, whereas the stability of the coupled spiral, coupled roll subsidence, and coupled short-period modes are degraded with the enhancement of gyroscopic coupling. Concurrently, increasing the gyroscopic coupling increases the damping ratio of the coupled Dutch roll and coupled phugoid modes. In contrast to this, the gyroscopic coupling reduces the damping ratio of the coupled short-period mode. The frequency of the coupled phugoid and coupled short-period modes is also increased with the increment in the gyroscopic coupling. The analysis also indicates that the countertorque destabilizes the coupled spiral mode.

Examining the stability derivatives of a compound helicopter

ABSTRACTSome helicopter manufacturers are exploring the compound helicopter design as it could potentially satisfy the new emerging requirements placed on the next generation of rotorcraft. It is well understood that the main benefit of the compound helicopter is its ability to reach speeds that significantly surpass the conventional helicopter. However, it is possible that the introduction of compounding may lead to a vehicle with significantly different flight characteristics when compared to a conventional helicopter. One method to examine the flight dynamics of an aircraft is to create a linearised mathematical model of the aircraft and to investigate the stability derivatives of the vehicle. The aim of this paper is to examine the stability derivatives of a compound helicopter through a comparison with a conventional helicopter. By taking this approach, some stability, handling qualities and design issues associated with the compound helicopter can be identified. The paper features a conventional helicopter and a compound helicopter. The conventional helicopter is a standard design, featuring a main rotor and a tail-rotor. The compound helicopter configuration features both lift and thrust compounding. The wing offloads the main rotor at high speeds, whereas two propellers provide additional propulsive thrust as well as yaw control. The results highlight that the bare airframe compound helicopter would require a larger tailplane surface to ensure acceptable longitudinal handling qualities in forward flight. In addition, without increasing the size of the bare airframe compound helicopter’s vertical fin, the Dutch roll mode satisfies the ADS-33 level 1 handling qualities category for the majority of the flight envelope.

Aeroelastic effects of battens on the flight dynamics of a MAV

AbstractWing flexibility is well established as providing gust rejection and delayed onset of stall for micro air vehicles. As such, many designs adopt wings of a flexible material mounted onto a skeleton comprised of a stiff leading-edge spar and stiff chordwise strips, called battens. These battens are shown to provide additional strength at localised regions of the wing and thus improve the gust rejection and delay stall; however, their effect on the flight dynamics is less studied. Using a numerical modeling approach, this paper explores a design space of vehicles with a varied number of wing battens mounted onto a baseline vehicle with a flexible wing. The battens are modelled as stepwise changes in torsional stiffness along the wing span. The resulting trim characteristics, static stability metrics and flight dynamics are evaluated. The battens are shown to improve gust rejection but otherwise have a complicated effect across the design space. A reduction in the number of battens improves the longitudinal static stability derivative slightly but lowers the lateral and directional static stability. The damping is decreased for the short period mode and increased for the phugoid and dutch roll modes as the number of battens is reduced.

Meta Aircraft Flight Dynamics

A meta aircraft is an air vehicle composed of a set of independent aircraft that are connected together in flight to form a larger composite aircraft. This paper explores the dynamics of meta aircraft systems with a focus on the changes in the aircraft flight dynamic modes and flexible modes of the system. Specifically, when aircraft are connected, basic flight dynamic modes such as the phugoid, short period, dutch roll, spiral, and roll modes change as a function of the number of connected aircraft. For aircraft connected in a wing-tip-to-wing-tip configuration, the longitudinal modes remain largely invariant with respect to the number of aircraft, whereas lateral modes are variable for both tip-to-tail and wing-tip-to-wing-tip connection configurations. In addition, connected aircraft exhibit complex flexible modes that change based on the characteristics of the connection joint and the number of connected aircraft. These conclusions are reached using a rigid six-degree-of-freedom representation for a single aircraft, where aircraft are connected through a set of linear and rotational elastic elements modeling the connection mechanism. Aerodynamic loads from all lifting surfaces are computed using a nonlinear lifting-line approach to enable aerodynamic wake interactions between connected aircraft.

Flight Dynamics Investigation of Compound Helicopter Configurations

Compounding has often been proposed as a method to increase the maximum speed of the helicopter. There are two common types of compounding known as wing and thrust compounding. Wing compounding offloads the rotor at high speeds, delaying the onset of retreating blade stall, and hence increasing the maximum achievable speed, whereas with thrust compounding, axial thrust provides additional propulsive force. There has been a resurgence of interest in the configuration due to the emergence of new requirements for speeds greater than those of conventional helicopters. The aim of this paper is to investigate the dynamic stability characteristics of compound helicopters and compare the results with a conventional helicopter. The paper discusses the modeling of two compound helicopters, which are named the coaxial compound and hybrid compound helicopters. Their respective trim results are contrasted with a conventional helicopter model. Furthermore, using a numerical differentiation technique, the dynamic stability of each configuration is assessed. The results show that the frequency of the coaxial compound helicopter’s Dutch roll mode is less than that of the conventional helicopter, and there is greater roll damping. Concerning the hybrid compound helicopter, there is greater roll damping and the phugoid mode stabilizes at high speeds.

Stability Features of the Saucer-Shaped Blend-Wing-Body Aircraft

The saucer-shaped aircraft is a novel aircraft adopting blend-wing-body configuration. The linear perturbation theory based on the classic flight dynamics was used to analyze the longitudinal, lateral and directional flight qualities of the saucer-shaped aircraft under low speed conditions. The flight qualities were given. Meanwhile the aerodynamic characteristics of the saucer-shaped aircraft, the conventional aircraft and the flying wing aircraft were also contrasted to discuss their similarities and differences. The results show that the saucer-shaped aircraft has stable longitudinal mode, rollover mode and Dutch roll mode. The spiral mode is unstable. The saucer-shaped aircraft exhibits superior flight qualities and excellent comprehensive performances.

Flight Dynamics and Control of a Vertical Tailless Aircraft

The present work aims at studying a new concept of a vertical tailless aircraft provided with a morphing tail solution with the purpose of eliminating the drag and weight created by the vertical tail structure. The solution consists on a rotary horizontal tail with independent left and right halves to serve as control surfaces. Different static scenarios are studied for different tail configurations. The proposed morphing configurations are analyzed in terms of static and dynamic stability and compared with a conventional configuration. The stability derivatives defining the limits of static stability are calculated for the whole range of tail rotation angles. The aircraft’s dynamic model is developed and feedback control systems are implemented. A sideslip suppression system, a heading control system and a speed and altitude hold system are studied for three different configurations, MC1, MC2 and MC3 configurations. Static results show that the aircraft is longitudinally stable for a wide range of tail rotation angles. Variation of tail dihedral and rotation angles are two mechanisms able to maintain directional and lateral stability but only the last is able to produce lateral force and yawing moment. Dynamic stability results demonstrate no spiral nor Dutch-roll modes due to the absence of the vertical stabilizer. The increase in tail rotation produces an appearance of the spiral mode and an unstable Dutch-roll mode that quickly degenerates into two unstable real roots with the increase in tail rotation. The addition of dihedral to the tail increases the stability of the overall modes while decreasing their variation amplitude with the tail rotation. The morphing tail configuration proved to be a feasible control solution to implement in an aircraft such as a small UAV, with the MC1 configuration being the most simple of the three morphing configurations and also the most reliable one.

PEMODELAN SISTEM DAN ANALISIS KESTABILAN DINAMIK PESAWAT UAV (MODELING SYSTEM AND DYNAMIC STABILITY ANALYSIS OF UAV)

Mission of Unmanned Aerial Vehicle (UAV) “Elang Avionik” is surveillance and aerial photographs. Therefore the flight of UAV must be stable and controlable, and first step activity is dynamic modelling and stability analisys. The problems of UAV system is disturbance, noise of sensor, MIMO and uncertainty dynamic model. For good result using the multivariable robust control, with some step research that is: (1)modeling and stability analysis, (2) design and implementation of PID control system, (3) flight dynamic parameter identification, (4) design and implementation of hardware in the loop simulation, (5) design and implementation of multivariable robust control, (6) test and evaluation of system. Simulation result show that the eigen value in longitudinal is: phugoid mode = –0,061293±0,40526i and non-oscillation mode = –6,1121±4,9253. In lateral directional is:dutch roll mode = –0,91089±5,7994i, spiral mode= –0,036563, and roll subsidence mode = –12,7181. Location of poles system on the left of imaginary axis, the means that the character of system is dynamic stable. But settling time to steady state condition is very long and improved by control system design.
 Key word: State space, Longitudinal, Lateral, Stable static, Stable dynamic

Flight dynamics of a pterosaur-inspired aircraft utilizing a variable-placement vertical tail

Mission performance for small aircraft is often dependent on the turn radius. Various biologically inspired concepts have demonstrated that performance can be improved by morphing the wings in a manner similar to birds and bats; however, the morphing of the vertical tail has received less attention since neither birds nor bats have an appreciable vertical tail. This paper investigates a design that incorporates the morphing of the vertical tail based on the cranial crest of a pterosaur. The aerodynamics demonstrate a reduction in the turn radius of 14% when placing the tail over the nose in comparison to a traditional aft-placed vertical tail. The flight dynamics associated with this configuration has unique characteristics such as a Dutch-roll mode with excessive roll motion and a skid divergence that replaces the roll convergence.

Flying qualities reduction of fly-by-wire commercial aircraft with reconfiguration flight control laws

As to guarantee flight safety when system failures occur, modern fly-by-wire flight control systems for commercial aircraft incorporate reconfiguration control modes. While relaxed static stabilities (RSS) are utilized on most new designed fly-by-wire airliners, the flying qualities design become a major concern when reconfiguration flight control laws are developed. The aim of this paper is to analyze the reduction of flying qualities when reconfiguration laws are activated. Longitudinal and lateral-directional control laws, along with their alternative and direct modes, were developed for a commercial aircraft with relaxed longitudinal and directional static stabilities. Flying qualities assessment with reconfiguration laws were carried out based on the handling qualities rating method (HQRM), which has certification levels connected to military specifications such as MIL-STD-1797A. The analysis indicated that short period mode and Dutch roll mode are most affected in the downgrade of flight control law. It is suggested that qualities of these modes should be guaranteed as priority when reconfiguration laws are designed.

Flight Stability of an Airplane on Mars

We compared the flight stability of an airplane on Mars and on Earth. Two kinds of airplanes were used in our analysis: a centimeter-sized indoor airplane with a very thin and light main wing, and a meter-sized airplane flying outdoors. Our comparisons show the following. (1) A longer period is required to damp or diverge disturbances on Mars than on Earth. (2) On Mars, the added mass and added moment of inertia can be ignored for a light wing, whereas the added mass and added moment of inertia cannot be ignored on Earth. (3) The natural circular frequencies in the short period, the phugoid, and the dutch roll modes are smaller on Mars than on Earth. The reduced frequencies, based on the natural circular frequencies on Mars, are smaller than those on Earth. The smaller reduced frequencies and the smaller added mass and added moment of inertia imply that the significance of unsteady aerodynamic force due to fuselage motion is lower on Mars than that on Earth.

DAMPING OF OSCILLATIONS IN FLIGHT CONTROL CIRCUITS OF SCHOOL AND TRAINING AIRCRAFT

The specific developments of Dutch roll mode have shown a number of flight dynamics deficiencies, prevailing in aircraft with fixed (non-assisted) controls in which the damping factor is at level 2. The project deals with the lateral motion damping (damper of gyration) issue according to the flight regulations, for an envelope as wide as possible, but mainly referring to missions involving the Dutch roll type developments. The undertaken analysis takes as a reference the school and training aircraft IAR – 99. The execution equipment, an actuator assisted by a servo valve, ensures the system efficiency of self-stabilization system SAS providing low execution times and high precision. The relationship between the flight quality parameters related to characteristics of lateral-directional motion modes, depending on gravimetric-inertial and aerodynamic parameters of the airplane is envisaged to meet the regular levels of flying qualities. The proposed calculation method can be used both for flight qualitative analysis and for defining the overall conditions for meeting the quality flight regulations. These conditions can serve as a basis for assessing the possibilities to remedy the abovementioned deficiencies mater.

センチメートルサイズの飛行機の安定性に関する一考察

The All Japan Student's Indoor Flying Robot Contest has been held every year since 2005. The Mayfly and its revised airplane were winning airplanes at the 3rd, 4th and 5th Contest. The most remarkable features of the Mayfly are its low aspect ratio wing (about 1) and its high dihedral angle (about 15deg). In this paper, the stability of the Mayfly was analyzed. The results revealed the followings. (1) The high stability of spiral and dutch roll modes are caused by the high dihedral angle. (2) Added mass of the wing affects the flight stability strongly because of the small body mass.

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

Stability analysis of gliding flight of a swallowtail butterfly Papilio xuthus

Preliminary observation of the flights of swallowtail butterfly Papilio xuthus revealed that its dihedral angle is larger than 30° and that the section of its left hind wing close to its body and the counterpart of its right hind wing actually clap and form a “vertical tail”. In this study, the effects of these two features on the lateral-directional dynamic flight stability of these butterflies were analyzed theoretically and revealed the following: (a) when the dihedral angle is larger than 30°, the lateral-directional motion of the swallowtail becomes stable; (b) the vertical tail stabilizes the dutch roll mode; (c) the effects of the dihedral angle on the roll and spiral modes of a swallowtail are qualitatively the same as those of a meter-sized airplane; and (d) with increasing dihedral angle, the stability of the dutch roll mode decreases for a meter-sized airplane with vertical and horizontal tails but increases for the swallowtail. A possible explanation for the latter effect is the smaller Reynolds number of the insect that causes the drag coefficient of the swallowtail wings to increase more rapidly with an increasing angle of attack compared to a large airplane.

Periodic motion suppression based on control of wing rock in aircraft lateral dynamics

Wing rock prevention is an important objective for an aircraft that needs to fly and maneuver at moderate to high angles of attack. This phenomenon is characterized as a periodic motion (or limit cycle), and needs to be avoided at all costs. A candidate mechanism for the wing rock limit cycle is the inertia coupling between an unstable lateral-directional (Dutch roll) mode with a stable longitudinal (Short period) mode. The coupling mechanism is provided by the nonlinear interaction of motion related terms in the complete set of motion equations. A methodology for preventing the limit cycle accomplished by adding a control function to the original equation of wing rock motion is presented in this paper. To analyze the state variables of the system, the complete set of nonlinear equations of motion including effective linear control function was solved. Numerical model constructed for A-4D and a Mig-21 Aircraft is solved to illustrate the results. The numerical results show that it was sufficient to use a linear control function including both roll attitude and roll rate for suppressing wing rock motion without any error in desired time. A good agreement between the numerical results and the published work is obtained for limit cycle oscillation existence at different values of damping ratio for almost the same roll angle.

T-50 가로-방향축 비행제어법칙 설계 및 궤환이득의 변화에 따른 항공기 동특성에 관한 연구

The T-50 advanced trainer aircraft combines advanced aerodynamic features and a fly-by-wire flight control system in order to produce a stability and highly maneuverability. The flight control system both longitudinal and lateral-directional axes to achieve performance enhancements and improve stability. The T-50 employs the RSS concept in order to improve the aerodynamic performance in longitudinal axis and the longitudinal control laws employ the dynamic inversion with proportional-plus-integral control method. And, lateral-directional control laws employ the blended roll system both beta-betadot feedback and simple roll rate feedback with proportional control method in order to guarantee aircraft stability. This paper details the design process of developing lateral-directional control laws, utilizing the requirement of MIL-F-8785C and MIL-F-9490D. And, this paper propose the analysis of aircraft characteristics such as dutch-roll mode, roll mode, spiral mode, gain and phase margin about gains for lateral-directional inner loop feedback.

1210 不安定ダッチロール・モードの機体に対する横揺れを加工した外部視界による飛行性改善(OS4-1 航空機を中心に,OS4 ヒューマンインタフェース,TRANSLOG 2006)

1210 不安定ダッチロール・モードの機体に対する横揺れを加工した外部視界による飛行性改善(OS4-1 航空機を中心に,OS4 ヒューマンインタフェース,TRANSLOG 2006)