Aircraft Roll Research Articles

Flight dynamics of aircraft incorporating the semi-aeroelastic hinge

Aircraft like the Boeing 777-X use on-ground folding wingtips to meet the airport gate size restriction while increasing the aspect ratio during flight to reduce induced drag. A recent concept of aircraft design is to utilise in-flight floating wingtips as a means of load alleviation, which is known as semi-aeroelastic hinge (SAH). This device allows wingtips to be released during manoeuvre and severe gusts to alleviate wing loads, while locking the wingtips during cruise to maintain an optimum aerodynamic shape. This paper develops a flight mechanics model incorporating flexible wings to study the influence of the SAH device on multiple aspects of aircraft flight dynamics. The dynamic responses of the aircraft to gusts and control surface inputs are computed and compared for various hinge and wingtip configurations and release times. It was found that the gust load measured from the wing with free hinge configuration was approximately 40% lower compared to that of the fixed hinge case. It is also shown that when the SAH is released, it can significantly reduce an aircraft's roll damping and the frequency of the short-period mode, leading to higher roll and pitch rates. Furthermore, it shows that the transient responses following the wingtip release will exacerbate the responses induced by gusts, and greater load alleviation can be achieved by manipulating the hinge release time for each gust length. Finally, a step input of the elevator during the hinge release was found to be beneficial for enhancing the gust load alleviation.

Roll Maneuverability of Transonic High-Aspect-Ratio-Wing Aircraft with Flared Folding Wingtips

This paper investigates the roll maneuvers of a very flexible, transonic high-aspect-ratio-wing aircraft with flared folding wingtips, representing a potential future commercial transport configuration. The computational study leverages a fully coupled nonlinear aeroelastic-flight dynamics framework for simulating roll maneuvers commanded by deflecting control surfaces inboard or outboard of the flared folding wingtip hinge. Releasing the flared folding wingtips during flight makes the aircraft roll faster only when deflecting outboard-of-hinge leading-edge control surfaces. However, the achieved roll angles and rates are much lower than the ones obtained by deflecting inboard-of-hinge trailing-edge control surfaces, whose roll control effectiveness is not impacted or even degrades when releasing the flared folding wingtips. These trends are explained by analyzing the role of sweep-induced washout effects in the very flexible, transonic high-aspect-ratio wing, revealing physical mechanisms not identified in previous studies on straight or swept wings with moderate flexibility. Higher wing out-of-plane bending stiffness increases the effectiveness of flared folding wingtips in enhancing roll maneuvers at low dynamic pressure but plays a slight role at high dynamic pressure. This study highlights the need to consider the impact of washout effects for different flight conditions and levels of wing flexibility when assessing the ability of flared folding wingtips to enhance the roll maneuverability of transonic high-aspect-ratio-wing aircraft.

Using Galvanic Vestibular Stimulation to Induce Post-Roll Illusion in a Fixed-Base Flight Simulator.

INTRODUCTION: The illusions of head motion induced by galvanic vestibular stimulation (GVS) can be used to compromise flight performance of pilots in fixed-base simulators. However, the stimuli used in the majority of studies fail to mimic disorientation in realistic flight because they are independent from the simulated aircraft motion. This study investigated the potential of bilateral-bipolar GVS coupled to aircraft roll in a fixed-base simulator to mimic vestibular spatial disorientation illusions, specifically the "post-roll illusion" observed during flight.METHODS: There were 14 nonpilot subjects exposed to roll stimuli in a flight simulator operating in a fixed-base mode. GVS was delivered via carbon rubber electrodes on the mastoid processes. The electrical stimulus was driven by the high-pass filtered aircraft roll rate to mimic the semicircular canals' physiological response. The post-roll test scenarios excluded outside visual cues or instruments and required subjects to actively maintain a constant bank angle after an abrupt stop following a passive prolonged roll maneuver. The anticipated outcome was an overshot in roll elicited by the GVS signal.RESULTS: The responses across subjects showed large variability, with less than a third aligning with the post-roll illusion. Subjective ratings suggest that the high-pass filtered GVS stimuli were mild and did not induce a clear sense of roll direction. However, uncontrolled head movements during stimulation might have obscured the intended effects of GVS-evoked illusory head movements.CONCLUSION: The mild and transient GVS stimuli used in this study, together with the uncontrolled head movements, did not convincingly mimic the post-roll illusion.Houben MMJ, Stuldreher IV, Forbes PA, Groen EL. Using galvanic vestibular stimulation to induce post-roll illusion in a fixed-base flight simulator. Aerosp Med Hum Perform. 2024; 95(2):84-92.

Aircraft overrun warning systems capabilities and disadvantages

Currently, attention of the aviation community and authorities is being increasingly focused on flight safety in the landing phase. It is accounted for the increased frequency of incidents in the final phase of flight and significant threats associated with the consequences of these events. The statistics of aviation accidents reveals that from 1959 to 2019, 55% of aircraft crashes in the world occurred in the phases of landing and takeoff. The given crashes resulted in 51% of all fatalities on board aircraft. In most cases, causes of these aviation accidents are involved with some kind of human error. Off-design conditions at an aerodrome also have a significant adverse effect on the aviation accident potential and severity. The increasing intensity of flights, airspace congestion, strict ATC-imposed restrictions, the necessity to perform a variety of procedures and general flight crew stress in conjunction with dynamically changing external conditions can disorient a flight crew and lead to a landing with a flight envelope overrange. The search for a solution in terms of preventing aircraft overruns is actively being conducted both by aviation authorities and aircraft manufacturers and operators. Within the framework of this review, the major external and operational factors, affecting the dynamics and the nature of the aircraft roll via the runway, are analyzed, including the context of several accidents that have occurred in recent years. In addition, the article emphasizes the methods to prevent and anticipate aircraft overruns based on the principles of active protection. In particular, the article examines the main operation aspects of onboard avionics systems installed on Boeing and Airbus aircraft and highlights the focus areas of their upgrading. Special attention is paid to the influence of the pilot and the possibility of taking his actions into account to predict an outcome of landing.

Novel active control technique of aircraft flaps asymmetry

This paper proposes an active monitoring strategy to control aircraft trailing-edge high-lift devices (flaps) asymmetry. A variety of system failures can cause asymmetry in the control surfaces, including the transmission torsion bar break down and control surface actuator wear and tear. The authors’ novel asymmetry active monitoring approach detects and identifies flaps position asymmetry. Once the failure side has been identified, the active control activates the wingtip brakes to stop the uncontrolled flap surface. The still controlled flaps are driven to the damaged surface braking point to reduce flap asymmetry. As a result, the undesired aircraft roll moment (due to flaps asymmetry) will be controlled, and the aircraft maneuverability after failure will be (partially) restored. The proposed asymmetry active monitoring technique has been widely tested in different operational and failure conditions, using wear-free or worn-out actuators and considering every failure side scenario. The behavior of the proposed active model is evaluated in terms of time response and stability margin under certain operating conditions.

Stability Augmentation in Lateral Directional Dynamics: A Multivariable Approach

This paper delves into the concept of stability augmentation in lateral-directional dynamics, focusing on a multivariable approach. In aircraft control systems, ensuring lateral-directional stability is crucial for safe and efficient flight. The primary objective is to examine the feedback control system's role in enhancing stability and how it interacts with the aircraft's inherent dynamics. We begin by exploring the basic augmentation system for lateraldirectional dynamics, which includes the feedback of body-axis roll rate to ailerons and yaw rate to the rudder, commonly referred to as the yaw damper. One of the key challenges addressed in this paper is the need to overcome the interference caused by the yaw damper when coordinating turns. This interference results from the constant nonzero yaw rate present during coordinated turns. To address this issue, the concept of "transient rate feedback" is introduced, which uses a washout filter to differentiate the feedback signal and minimize its effect during steady-state conditions. The paper presents mathematical models and transfer functions that describe the behavior of the lateral-directional augmentation system. It discusses the impact of different parameters, such as the time constants of actuators and washout filters, on the system's performance. The design of the feedback loops for roll and yaw control is elaborated upon, emphasizing the trade-offs between roll response, dutch roll damping, and roll-yaw coupling. Simulation results are used to evaluate the effectiveness of the stability augmentation system in improving the aircraft's roll response and dutch roll damping under varying flight conditions. The paper concludes with insights into the challenges and benefits of multivariable control system design for lateral-directional stability augmentation in aircraf

Capturing nonlinear time-dependent aircraft dynamics using a wind tunnel manoeuvre rig

This paper considers a novel multi-degree-of-freedom dynamic manoeuvre rig, with the aim of assessing its potential for capturing aircraft model nonlinear time dependent dynamics in the wind tunnel. The dynamic manoeuvre rig capabilities are demonstrated via a series of experiments involving a model aircraft in a closed section low-speed wind tunnel. A series of open loop experiments show that the aircraft model exhibits nonlinear time dependent dynamics. This nonlinear behaviour manifests itself as limit cycle oscillations that increase in complexity with the number of degrees-of-freedom in which the aircraft is allowed to move. Two real-time closed loop control experiments further illustrate the manoeuvre rig potential: first, using a pitch motion configuration, an experiment is conducted to investigate the limit cycle behaviour in more detail, allowing the stability properties of the pitch oscillations to be assessed; secondly, using a 5-DOF motion configuration, the test motion envelope is extended by using a compensating feedback control law to track the aircraft's roll motion. Together, these experiments demonstrate the manoeuvre rig potential to reveal aircraft nonlinear and unsteady phenomena.

RESEARCH OF THE A380 AIRCRAFT VORTEX WAKE IMPACT ON MS-21 CLASS AIRCRAFT

The paper is devoted to the problem of safe flight in vortex hazard conditions. A vortex wake is always produced behind flying aircraft. This vortex wake is invisible to other aircraft following it. Therefore, getting into a vortex wake from a preceding aircraft often becomes unexpected and quite often leads to flight incidents. This is confirmed by the statistics of flight accidents. With the introduction of aircraft weighing more than 500 tons, the problem of vortex safety has only sharpened. The fact is that the old standards that define safe intervals between flying aircraft are still active. These standards are given in this paper. It is also shown that even if these standards are observed, the flight of a medium-class aircraft at the same level as a heavy-class aircraft is unsafe. To study the effect of the vortex wake from the preceding aircraft, a special computational software complex based on the discrete vortex method was developed. This complex has passed the necessary testing and state registration. A number of measures were carried out to validate and verify the developed complex, confirming the operability of the programs included in it and the reliability of the results obtained. On the basis of this computational and software complex studies on the effect of the A380 aircraft vortex wake on MS-21 class aircraft were performed. The studies were undertaken for various altitudes and speeds of the A380 aircraft and for its various flight configurations. As a criterion for the MS-21 aircraft safe flight, the roll moment that occurs due to falling into the vortex wave, in particular, its coefficient was chosen. If the coefficient of the MS-21 aircraft roll moment when it hits the vortex wake exceeds that from the ailerons, such a flight is considered dangerous. The distances behind the A380 that are unsafe for the MS-21 aircraft flight are given.

A non-iterative design for aileron to rudder interconnect gain

AbstractAileron to Rudder Interconnect (ARI) gain is implemented on most fighter aircraft, primarily to reduce the side slip produced due to adverse yaw from pilot lateral control stick input and to improve the turn rate response. A systematic and non-iterative design procedure for ARI gain is proposed herein based on the evaluation of a transfer function magnitude at the aircraft roll mode frequency. The simplicity of the proposed method makes it useful for real-time flight control law reconfiguration in situations where the aileron control authority is diminished due to damage. This is demonstrated by a simulation example considering an aileron surface damage scenario.

Attitude Measurement of Special Aircraft Based on Geomagnetic and Angular Velocity Sensors

Aiming at the problem of attitude test of special aircraft in flight, the combined test technology of geomagnetic sensor and angular velocity sensor is studied. The mathematical model of special aircraft roll attitude test based on combined measurement is established. The error models of special aircraft roll angle based on yaw angle input and pitch angle input are derived, respectively, and based on the actual flight trajectory data of aircraft, the mathematical model of special aircraft roll attitude test is established The simulation results show that the roll angle error input by yaw angle is between -0.4° and 0.9°, while the roll angle error input by pitch angle is between -0.4° and 1.2°, which shows that the calculation accuracy of roll angle input by yaw angle is higher, and the existence of magnetic measurement blind area is verified. In this paper, the method of judging the blind area of geomagnetic survey and the algorithm model of eliminating the influence of blind area are proposed.

Use of Orthogonally Linearly Polarized Waves Radiated from a Radio Beacon in the Modulation Methods for Measuring Aircraft Bearing and Roll

On the basis of using the Jones vectors and matrices, we develop the polarization-modulation method for determining the aircraft bearing and roll by the radio-beacon radiated waves with orthogonal linear polarization, which was proposed in [1]. The waves are simultaneously radiated from two points with the known coordinates, which are spaced in the measurement plane. The engineering realization of the method, which is based on using the polarization modulator placed in the single-channel microwave transmission line of an onboard receiving antenna of an aircraft, is considered. The polarization modulator has the form of the rotating segment of a circular waveguide with a built-in half-wave phase plate. Mathematical expressions, which provide a clear physical understanding of the aircraft bearing and roll relation to polarization and spectral characteristics of the resulting onboard-recorded wave field of the radio beacon in the linear polarization basis, are presented.

Aircraft wing rock oscillations suppression by simple adaptive control

Roll angular motion of the modern aircraft operating in non-linear flight modes with a high angle of attack often demonstrates the limit cycle oscillations, which is commonly known as the wing rock phenomenon. Wing rock dynamics are represented by a substantially non-linear model, with parameters varying over a wide range, depending on the flight conditions (altitude, Mach number, payload mass, etc.) and angle of attack. A perspective approach of the wing rock suppression lies in the adaptation methods. In the present paper an application of the simple adaptive control approach with the Implicit Reference Model (IRM) is proposed and numerically studied. The IRM adaptive controller is applied to ensure smooth tracking the roll angle of the reference (desired) trajectory with the simultaneous wing rock prevention. As compared with the previous authors' work, in the present paper more complex and realistic model is employed, where interdependence between aircraft roll and sideslip motions and the limitations on the aileron deflection angle are explicitly taken into account at the stage of the controller design. To this aim, the modification of the IRM control scheme is suggested and numerically studied. The simulation results obtained demonstrate high efficiency of the proposed method.

Comparison and analyses of a variable span-morphing of the tapered wing with a varying sweep angle

ABSTRACTThis work presents a comparative study of design and development, in addition, of analyses of variable span morphing of the tapered wing (VSMTW) for the unmanned aerial vehicle (UAV). The proposed concept consists in the sliding of the inner section into the fixed part along the wing with varying the angle of the inner section inside the fixed part (parallel with the leading edge and the moving-wing axis is coincident to the fixed-wing axis) within two configurations. The wing design is based on a NACA 4412 aerofoil with the root chord of 0.675m and the tip chord of 0.367m for the fixed segment and 0.320m for the moving segment. Morphing wing analysis occurs at three selected locations that have been specified for extending and modifying span length by (25%, 50%, and 75%) of its original length to fulfill various flight mission requirements. The main objective of this paper is to compare the aerodynamic characteristics for several span lengths and sweep angles and to find their most efficient combinations. The wing is optimised for different velocities during all phases of flight (min speed, loiter, cruise, and max speed) which are 17, 34, 51, and 68m/s, respectively. The analyses are performed by computing forces (drag and lift) and moments at various altitudes, such as at the sea level, at 5,000 and 10,000ft. Two-dimensional aerodynamic analyses are carried out using XFLR5 code, and the ANSYS Fluent solver is used for investigating the flow field on the three-dimensional wing structure. It has been observed that a variable span morphing of tapered wing technology with a variable sweep angle can deliver up to 32.93% improved aerodynamic efficiency. This concept design can also be used for the aircraft roll motion technique instead of conventional control devices. Furthermore, the range flight mission increases up to 46.89% when the wing is placed at its full length compared to an original position. Finally, it has been concluded from this study that the wing design is more sensitive to the changing angle of the inner section and more efficient in terms of aerodynamic characteristics.

Backstepping-based control methodology for aircraft roll dynamics

This article investigates a backstepping-based control method for aircraft roll dynamics. The research starts with a formulation of backstepping control law for a general class of a strict-feedback form of nonlinear dynamic systems. The backstepping control law is formulated by introducing a normal tracking error. Then, control and virtual control inputs are selected by addressing each layer of the design process with a chosen corresponding control Lyapunov function. The parameter assignment in each design layer is selected to ensure the stability of the entire system. Next, a backstepping-based control algorithm with online-gain schedule or variable gains is provided for the standard strict-feedback system. In order to validate the proposed method, application of roll dynamics of aircraft is implemented. Dynamic equations of free-to-roll aircraft model is restructured in a standard strict-feedback model for formulating the backstepping control. Then, a backstepping control–based control strategy is provided for aircraft free-to-roll dynamics. Indoor experimental and simulation studies of roll angle control for the L-59 free-to-roll aircraft model at NASA Langley Research Center are implemented to verify and validate the proposed approach.

Fuel Quantity Estimation of Aircraft Supplementary Tank Using Markov Chain Monte Carlo Method

This paper presents an aircraft fuel quantity estimation method using the Markov Chain Monte Carlo (MCMC) method. Using the proposed method, fuel quantity uncertainty of an aircraft supplementary tank can be estimated when the roll and pitch attitudes of an aircraft change. Through reflecting uncertainties, the conservative bound of fuel quantity estimation results can be found, which is necessary for a reliable aircraft operation. The first step of the estimation process is a mathematical modeling of the fuel quantity in a supplementary tank. In the model, the fuel quantity is represented as a multivariate polynomial function of sensor output (i.e., frequency), aircraft roll and pitch angles. The parameter of the mathematical model is then estimated using the MCMC method. As an estimation result, the probability density function of the fuel quantity is provided, which accounts for the uncertainties caused from the developed mathematical model and measured data. The lower bound in the estimation result can be utilized as a conservative fuel quantity value for a reliable operation. To validate the proposed fuel quantity estimation approach, a test with known fuel quantity is performed.

Identification of In-Flight Wingtip Folding Effects on the Roll Characteristics of a Flexible Aircraft

Wingtip folding is a means by which an aircraft’s wingspan can be extended, allowing designers to take advantage of the associated reduction in induced drag. This type of device can provide other benefits if used in flight, such as flight control and load alleviation. In this paper, the authors present a method to develop reduced order flight dynamic models for in-flight wingtip folding, which are suitable for implementation in real-time pilot-in-the-loop simulations. Aspects such as the impact of wingtip size and folding angle on aircraft roll dynamics are investigated along with failure scenarios using a time domain aeroservoelastic framework and an established system identification method. The process discussed in this paper helps remove the need for direct connection of complex physics based models to engineering flight simulators and the need for tedious programming of large look-up-tables in simulators. Instead, it has been shown that a generic polynomial model for roll aeroderivatives can be used in small roll perturbation conditions to simulate the roll characteristics of an aerodynamic derivative based large transport aircraft equipped with varying fold hinge lines and tip deflections. Moreover, the effects of wing flexibility are also considered.

DESIGN CONCEPTS OF AN ONBOARD EARLY WARNING SYSTEM OF PILOT ABOUT ENTERING WAKE VORTICES FROM ANOTHER AIRCRAFT

An airborne aircraft forms a wake vortex behind itself dangerous for other entering it aircraft both piloted and unmanned. Wake vortex intensity depends on parameters of the aircraft creating it, so the greater the aircraft mass is, the higher its impact on other aircraft is. It is not possible to register visually the wake vortex, since in fact it is invisible. Introduction of wide-body aircraft like A380 into service leads to the revision of separation rules with the aim to increase admissible distance between aircraft. There is a quite demonstrative case when Challenger 604 got into the wake vortex after A380: though separation rules at the altitude were observed, Challenger performed an out-of-control rotating descent from the altitude of 10000 m to 3000 m. At present, in spite of multi-year research there are no real verified suggestions on wake vortex safety of aircraft flights. The paper presents the methodological basis and design concepts of an onboard early warning system of a pilot about entering wake vortices from another aircraft. The main task of the proposed system is to reveal wake vortices according to pressure decrease in their cores; to do it we perform on-line measuring of pressure in front of an aircraft. Measurements are done by a standard onboard air data system and an onboard inertial satellite system in order to control the consistency of “barometric” altitude readings and those of altitude defined by an inertial satellite system. The value of wake vortices rarefaction measured by an onboard air data system allows estimating the influence degree of wake vortices on the aircraft roll moment with the help of a special hardware and software complex and to determine the necessity to change the flight mode. It is proposed to use a missile bench for the dimensioning wake vortices on aircraft models in order to test computational methods of wake vortices dimensioning

Roll performance assessment of a light aircraft: Flight simulations and flight tests

A methodology is presented for the roll performance assessment of a light aircraft. The study is based both on flight simulations and flight tests, focusing on the accurate determination of the lateral control power. The chosen test airplane was a Tecnam P92, a two-seat ultralight aircraft which was specifically equipped with a lightweight and accurate instrumentation for the planned set of flight data measurements. A matrix of flight experiments for the test campaign was established with the support of 6-degree-of-freedom simulations, implementing a carefully constructed baseline dynamic model of the aircraft. The article discusses first the general problem of a reliable evaluation of aircraft roll performance indicators, i.e. the estimation of the aerodynamic derivatives that mainly influence the airplane ability to roll. Next, the results of extensive flight test activities are presented. The analysis of several roll maneuvers performed at different flight speeds and with different aileron maximum deflections showed interesting rolling characteristics for this non-aerobatic aircraft. One notable finding was a clear nonlinear dependency of the aileron efficiency index on aileron deflection amplitude. A control power derivative extracted from flight data in the form of lookup table was used to correct the baseline flight dynamics model. Flight simulations outputs based on the updated model showed a satisfactory agreement with experimental time histories. According to this, the present effort proposes a new method to estimate the aileron control derivative in whole the flight envelope for light aircraft.

Two-step rectification method for distortions caused by aircraft roll in push-broom hyperspectral images

Aircraft roll is an important reason for geometric distortion of airborne push-broom hyperspectral images. A two-step rectification method is proposed to correct the geometric distortions of push-broom hyperspectral images caused by aircraft roll. According to the distortion characteristics of hyperspectral images, image distortion is mainly classified into two categories: high frequency distortion and large amplitude distortion. For high frequency distortion, the first-step correction is implemented by slide matching of segmented windows between adjacent scan lines. For large amplitude distortion, the second-step correction is achieved using ground control points and linear features between a reference map and an uncorrected image. Experimental results show that the proposed method can eliminate image distortion caused by aircraft roll effectively.

Air-Ground Channel Characterization for Unmanned Aircraft Systems—Part IV: Airframe Shadowing

Applications of unmanned aircraft systems (UAS) are expected to expand dramatically in the coming decades. In order to provide safe and reliable links for UAS, NASA Glenn Research Center sponsored a measurement campaign in 2013 to characterize air-ground (AG) channels. In the first three of our AG channel characterization series papers, path loss, small scale fading, stationarity distance, root mean square (RMS) delay spread, spatial correlations, and tapped delay line models were presented for a range of ground site environment. In this paper, we expand the results to a unique and little-studied characteristic of the AG channels—airframe shadowing—for a medium-sized aircraft. Airframe shadowing occurs when the line-of-sight signal is obstructed by the airplane itself in some specific maneuvers. Based on over 200 aircraft wing/engine shadowing events in both C-band (5060 MHz) and L-band (968 MHz) collected in the measurement campaign, shadowing depth, duration, multiple antenna diversity gain, and small scale fading results and their statistics are reported. Algorithms are proposed to simulate a random shadowing event based upon shadowing depth and duration cumulative density functions. Airframe shadowing characteristics are independent of the local ground site conditions and link distance. The shadowing loss is modeled as a function of aircraft roll angle, but shadowing loss and duration are essentially uncorrelated. The maximum shadowing loss measured was over 35 dB and the duration was up to 74 s. As expected, deployment of multiple aircraft antennas is shown helpful to mitigate this shadowing.