Behavior Of Aircraft Research Articles

Assessment on the ADDSAFE Benchmark Simulator of an H-infinity Fault Detection Design for Aircraft

In this article the verification assessment of an aircraft fault detection and diagnosis (FDD) scheme based on H-infinity is presented. The proposed scheme is designed to detect abnormal aircraft behaviour, specifically aileron faults leading to degradation of performance. The design follows a global approach based on an H∞ FDD filter residual generator augmented with simple threshold and time-based logic for residual evaluation. The design development and verification is part of a European 7th Framework Program project entitled “Advanced Fault Diagnosis for Sustainable Flight Guidance and Control (ADDSAFE)”. The verification results show that the proposed FDD scheme satisfies the demanding performance and robustness metrics established for on-board aircraft assessment by the ADDSAFE industrial partners.

Full Envelope Nonlinear Parameter-Varying Model Approach for Atmospheric Flight Dynamics

This paper presents a nonlinear parameter-varying modeling approach to duplicate the aircraft dynamic behavior while moving from one flight region to another. This approach starts by generating a local two-term truncatedVolterra series, which is enough to capture the quadratic andbilinear nonlinearities, at different operating conditions over the flight envelope. The variation of these series’ coefficient matrices are then sought through different interpolation techniques. A nonlinear F-16 longitudinal model was used to assess the proposed approach. The improvement in the accuracy to predict, understand, and analyze the nonlinear aircraft behavior over the previous linear parameter-varying approach, which effectively ignored the second-order stability and control derivatives, is demonstrated through many numerical test cases.

Effects of surveillance failure on airborne-based continuous descent approach

For higher density operation in terminal manoeuvring area, Airborne Surveillance Application System (ASAS) is seen as a promising option in the future air traffic management (ATM). One idea of recent interest in ASAS application is Interval Management (IM), which is expected to support energy-saving arrivals, commonly referred as Continuous Descent Approach (CDA). The questions are how the IM application achieves safety and capacity in the CDA environment, and how to identify any potential emergent behaviour that should be taken into account in the operation design. The motivation for this study is the need to properly understand the nominal and non-nominal behaviour of many aircraft when the ASAS application is applied to the CDA environment. For this purpose, this study has conducted a preliminary safety assessment of the ASAS speed control for multiple trailing aircraft in CDA operation. This article focuses on ASAS surveillance failure as one of the critical events during flight. Using Stochastically and Dynamically Coloured Petri Net (SDCPN), ASAS core components and their interactions are modelled. Through Monte Carlo simulation via the SDCPN models, the impact of the ASAS surveillance failure on the airborne-based CDA operation is assessed.

Trajectory Clustering and an Application to Airspace Monitoring

This paper presents a framework aimed at monitoring the behavior of aircraft in a given airspace. Trajectories that constitute typical operations are determined and learned using data-driven methods. Standard procedures are used by air traffic controllers (ATCs) to guide aircraft, ensure the safety of the airspace, and maximize runway occupancy. Even though standard procedures are used by ATCs, control of the aircraft remains with the pilots, leading to large variability in the flight patterns observed. Two methods for identifying typical operations and their variability from recorded radar tracks are presented. This knowledge base is then used to monitor the conformance of current operations against operations previously identified as typical. A tool called AirTrajectoryMiner is presented, aiming at monitoring the instantaneous health of the airspace, in real time. The airspace is “healthy” when all aircraft are flying according to typical operations. A measure of complexity is introduced, measuring the conformance of current flight to typical flight patterns. When an aircraft does not conform, the complexity increases as more attention from ATC is required to ensure safe separation between aircraft.

Video analysis of the flight of a model aircraft

A video-analysis software tool has been employed in order to measure the steady-state values of the kinematics variables describing the longitudinal behaviour of a radio-controlled model aircraft during take-off, climbing and gliding. These experimental results have been compared with the theoretical steady-state configurations predicted by the phugoid model for longitudinal flight. A comparison with the parameters and performance of the full-size aircraft has also been outlined.

Simulation of a high-agility model airplane in the presence of severe structural damage and failures, and design of a dynamic inversion controller

The simulation of the aircraft dynamics and behavior of the open loop as well as the closed loop system is a central part in the development of controllers for real flight tests. This paper presents an approach for the systematic development of a nonlinear simulation model in MATLAB/Simulink for a high-agility model airplane, with a total of 16 different control inputs, together with the design of an appropriate rate command attitude hold (RCAH) controller. The simulation model is capable to represent the behavior of the aircraft, including the dynamics of the motors, the actuators and the sensors, for the nominal case as well as in the case of severe structural damage and failures. The highly sophisticated model of the aircraft is used subsequently for the design of a controller. Dynamic inversion (DI) uses the knowledge of the nonlinear plant dynamics to transform the nonlinear dynamics into a chain of integrators, and after this transformation, a controller can be designed using methods from classical or robust control. A relative degree 1 (RD 1) rate command attitude hold controller, based on dynamic inversion, will be presented together with a semi-analytical approach to select and adjust the appropriate controller gains. The paper is completed by some simulation results encountering severe structural damage and failures. The derived controller can either serve as a stand-alone controller or as a baseline controller for more sophisticated control approaches.

Common aspects and differences in the behaviour of classical configuration versus canard configuration aircraft in the presence of vertical gusts, assuming the hypothesis of an elastic fuselage

The paper analyzes, in parallel, common aspects and differences in the behavior of classical configuration versus canard configuration aircraft in the presence of vertical gusts, assuming the hypothesis of an elastic fuselage. The effects of the main constructional dimensions of the horizontal empennage on lift cancelling and horizontal empennage control are being analyzed.

The crashworthiness of civil aircraft using different quadrangular tubes as cabin-floor struts

Quadrangular tubes were used as a cabin floor's struts considering their excellent impact response performance to adequately utilise the energy absorbing ability of struts. The finite element model of civil aircraft under sound simplification was built to simulate its drop test. Several fuselage sections with different thicknesses and strut triggers were considered here. The acceleration history, failure behaviour and energy absorption ability of the civil aircraft were investigated. The result shows that the impact response of civil aircraft with different struts could be divided into two groups in these cases. The cabin floor collides with the hold floor for the first group, and there is a collision between the strut and the ground for the second one. The initial maximal peak acceleration increases with an increase in strut's thickness, and the triangular and quadrangular triggers are not recommended in these cases. When strut's thickness is 0.9 mm, the civil aircraft has the best impact performance, and it would get worse with increase or decrease in strut's thicknesses.

Flight Mechanics Analysis of a Motorized Trike with Composite Wing

In this work, a mathematical model to study the dynamic behavior of a trike ultralight aircraft is developed. This is done because, to the best of the writers’ knowledge, no specific theories are available for powered hang gliders. To do that, in order to take into account the engine thrust, the necessary changes have been made on models developed for hang gliders. The trike, which is a particular case of powered hang glider, is modeled as a compound system made of a wing and an undercarriage. The case of rigid wing, made of composite materials, is considered in the present work. Equilibrium governing equations are written, the trim conditions are evaluated, and the fixed control dynamic stability is investigated for both longitudinal and lateral motion. After that a modified wing configuration, with two additional vertical fins, is investigated and compared. The dynamic response to pilot controls is evaluated to complete the analysis.

Meteorological influences on the design of advanced aircraft approach procedures for reduced environmental impacts

There is increasing interest in the development of aircraft operating procedures that reduce the environmental impacts of commercial aviation through minimization of fuel burn, emissions and noise impacts. Meteorological factors can have a major influence on the behaviour of aircraft in different phases of flight, thus they must be carefully considered in the development of any new procedures. In this paper the most important of these factors are considered (wind profiles and local pressure variations) within the context of development of advanced approach procedures at a major UK airport. Models of the wind characteristics were developed for the region around the airport using data collected from the Natural Environment Research Council Mesosphere-Stratosphere-Troposphere Radar at Aberystwyth and surface wind measurements made at the airport, while an analysis of local pressure effects was based on readings taken at the airport. These models were used in a Monte Carlo flight simulator to determine the suitability of different approach procedure designs in terms of flight and environmental performance. Flight tests of the final procedure design were conducted at the airport with a variety of commercial aircraft. These demonstrated the suitability of the procedures (and hence validated the modelling strategies used) and that significant environmental benefits in terms of reduced noise, fuel burn and emissions were achieved compared to existing procedures. Copyright © 2010 Royal Meteorological Society

Validation Studies for Aeroelastic Trim and Stability of Highly Flexible Aircraft

High-altitude, long-endurance (HALE) aircraft are highly flexible, requiring nonlinear aeroelastic analysis. NATASHA (Nonlinear Aeroelastic Trim and Stability of HALE Aircraft) is a computer program developed to analyze the aeroelastic behavior of HALE aircraft. The underlying formulation is based on the published geometrically exact, fully intrinsic beam equations. This paper presents a wide range of results from NATASHA, comparing them with well-known solutions of beam stability and vibration problems, experimental data, or results from well-established computer codes. Despite the simplicity of the underlying formulation, results obtained confirm the accuracy of the analysis and its suitability for conceptual and preliminary design of HALE aircraft.

Auditory Alerts: An Intelligent Alert Presentation System for Civil Aircraft

The principal role of the auditory interface on civil aircraft is to inform pilots of dangerous or potentially dangerous system states. Efficient alerts provide information that is uniquely identifiable with one aspect of the aircraft's behavior and do not form a nuisance by being too intrusive and overly persistent. It is known that excessive auditory alert intensity can impair human performance; however, simply lowering alert intensity is not sufficient because there is a need to ensure detection and safety are not compromised. In an attempt to address this problem, an automated alert system, the Intelligent Alert Presentation system, was constructed. The system analyzes flight deck noise in real time, and alerts are then presented at a fixed ratio above the noise (+10 dBA). The system has alert muting capabilities that can be activated following detection. The intensity is attenuated to −5 dBA below the noise level, where the signal is partially masked but remains detectable and comprehensive, according to the findings of 2 experiments reported here. It is suggested that this would provide the pilot with a more suitable environment for carrying out higher order cognitive, more demanding tasks.

Airspace Encounter Models for Estimating Collision Risk

Airspace encounter models, providing a statistical representation of geometries and aircraft behavior during a close encounter, are required to estimate the safety and robustness of collision avoidance systems. Prior encounter models, developed to certify the Traffic Alert and Collision Avoidance System, have been limited in their ability to capture important characteristics of encounters as revealed by recorded surveillance data, do not capture the current mix of aircraft types or noncooperative aircraft, and do not represent more recent airspace procedures. This paper describes a methodology for encounter model construction based on a Bayesian statistical framework connected to an extensive set of national radar data. In addition, this paper provides examples of using several such high-fidelity models to evaluate the safety of collision avoidance systems for manned and unmanned aircraft.

Modelling and analysis of air traffic control systems using hierarchical timed coloured Petri nets

Hierarchical timed coloured Petri net (HTCPN) models have been utilized as a visual formalism for the modelling of complex reactive systems. They brighten the features on describing properties of causality, concurrency and synchronization. This paper focuses on the use of HTCPNs to model and analyse a dynamic procedure of an air traffic control (ATC) system. The advantage of the proposed approach is the clear presentation of the aircraft behaviour in terms of conditions and events. To our knowledge, this is the first work that employs HTCPNs to obtain models of ATC systems.

Aeroelastic simulations using gridless boundary condition and small perturbation techniques

This paper examines the use of stationary Cartesian mesh for non-linear flutter computations involving complex geometries. The surface boundary conditions are implemented using reflected points which are determined via a gridless approach. The method uses a cloud of nodes in the vicinity of the surface to get a weighted-average of the flow properties using radial basis functions. To ensure computational efficiency and for local grid refinements, multigrid computations within an embedded grids framework are used. As the displacements of moving surfaces from their original position are typically small for flutter problems, a small perturbation boundary condition method is used to account for the moving surfaces. The method therefore does not require repeated grid re-generation for the deforming surfaces. The overall method is both accurate and robust. Computations of the well-known Onera M6 wing, RAE wing-body configuration, the AGARD 445.6 wing flutter test case show good accuracy and efficiencies. Simulations of the aeroelastic behavior of a complete fighter-type aircraft with wing tip missiles at high transonic speeds further demonstrate the practical usefulness of the present boundary conditions technique.

Piecewise Global Volterra Nonlinear Modeling and Characterization for Aircraft Dynamics

Evaluating global aircraft dynamic behavior by Volterra theory as an efficient nonlinear approximation method is investigated. In previous research, Volterra theory was implemented to evaluate the system behavior in a selected local region, which restricts the ability to capture the aircraft behavior while moving from one flight region to another. The current research presents a global piecewise Volterra kernel approach, which uses submodel Volterra kernels to build global kernels. A piecewise interpolation is employed to switch between the submodels. An approximate nonlinear pitch-plunge model for a high-performance aircraft was used to assess the proposed approach. A set of experimental simulations is conducted to verify the capability of the proposed model. The approach is compared with a global linear approach while employing the nonlinear simulation as the benchmark.

Corrosion behaviour of aircraft coating systems in acetate‐ and formate‐based de‐icing chemicals

AbstractCorrosion behaviour of four coating systems, which are commonly used in aircraft components; namely cadmium‐coated and subsequently chromate‐treated steel AISI 4340, aluminium‐coated steel AISI 4340, anodised aluminium alloy 7075‐T6 and chromate‐treated aluminium alloy 7075‐T6, were investigated in six commercial acetate‐ and formate‐based de‐icing chemicals. The results show that the aluminium‐coated steel specimens experience least corrosion among the four coating systems; no corrosion is detected in potassium acetate‐based de‐icing chemicals (Safeway KA HOT, Safegrip and Safegrip+), although some corrosion is observed in the other three chemicals (Safeway SD, Safeway SF and Meltium). In contrast, the coatings in the other three coating systems are damaged in all six de‐icing chemicals. The thickness of the coating does not necessarily predict how well the coating will protect the substrate; the thickest coating, several tens of micrometres, is apparent on the cadmium‐ and chromate‐coated steel specimens, while only a few micrometres thin aluminium coating on the steel substrate is the only coating system that can survive the corrosion tests in some of the de‐icing chemicals. Comparison of the results from the two test methods used in this research, polarisation measurements and chemical exposure tests, shows that, for each coating system, the extent of corrosion, as evaluated on the basis of weight changes calculated from corrosion current density values and those experienced during chemical exposure tests, is different: the weight changes that materialise during exposure tests are, at least, from one to two orders of magnitude higher than those predicted by calculations. In this paper, these observations are discussed and explanations for them are presented.

Intelligent Automatic Fault Detection for Actuator Failures in Aircraft

This paper applies an intelligent technique based on fuzzy-genetic algorithm for automatically detecting failures in aircraft. The fuzzy-genetic algorithm constructs the automatic fault detection system for monitoring aircraft behaviors. Fuzzy-based classifier is employed to estimates the time of occurrence and types of actuator failure. Genetic algorithms are used to generate an optimal fuzzy rule set for the classifier. The optimization capability of genetic algorithms provides an efficient and effective way to generate optimal fuzzy rules. Different types of actuator failure can be detected online by the fuzzy-genetic algorithm based automatic fault detection system. Simulations with different actuator failures of the nonlinear F-16 aircraft model are reported and discussed.

EXPERIMENTAL INVESTIGATION ON A PITCHING MOTION DELTA WING IN UNSTEADY FREE STREAM

As combat aircraft becomes more and more maneuverable, the need to understand the unsteady behavior of aircraft in dynamic flow fields becomes more important. Usually researchers pay more attention to the effects on the changes of AOA, but ignore the effects of velocity variations. It is known that the velocity of aircraft changes greatly when the aircraft undergoes a high angle of attack maneuver, like "cobra" maneuver. To completely simulate and study the effect of rapid changes in both free stream velocity and angle of attack, a pitching motion setup is developed in the unsteady wind tunnel of NUAA. By measuring unsteady loads, unsteady pressure distribution and flow visualization, the unsteady aerodynamic behavior of a pitching isolated delta wing and the pitching delta wing coupled with unsteady free stream are investigated. It is found that the oscillating free stream velocity affects the hysteresis characteristics of the pitching delta wing further. The pressure distribution and flow visualization measurements show that the changes in the structure of the leading-edge vortices are the main reason. These studies conclude that a good understanding of the unsteady aerodynamics is vitally important in the design of super-maneuverable aircraft.

Generation of flexible aircraft LFT models for robustness analysis

In the aeronautical industry, the robustness properties of an aircraft are usually assessed using intensive and time-consuming simulations. Fortunately, several optimization techniques can be implemented and applied for clearance of flight control laws, in order to improve the efficiency and reliability of the certification process. Some of them, such as Lyapunov-based analysis and μ-analysis, require the considered models to be written as Linear Fractional Representations (LFR), which is unfortunately not the case of the aeroelastic models available in an industrial context. A whole methodology is thus proposed in this paper to convert a set of numerical flexible aircraft models into a suitable LFR which depends on the aircraft configuration and the flight conditions. This is a challenging issue, since the size of the initial models is very large and the state vector does not have the same physical meaning for the whole model set. Nevertheless, an LFR is obtained, which is representative of the aircraft behavior in the sense that its eigenvalues and frequency responses almost exactly match those of the initial flexible models. Moreover, its complexity proves compatible with the use of robustness analysis tools. Numerical results indeed show that the considered clearance problem is computationally tractable., clearance of flight control laws, LFT modeling and reduction techniques, aeroelastic models, robustness analysis.