Behavior Of Aircraft Research Articles

Interplay of unsteady aerodynamics and flight dynamics of transport aircraft in icing conditions

Airframe icing causes significant degradation of aerodynamic characteristics and influences the flight safety. Wind tunnel study of longitudinal steady and unsteady aerodynamic characteristics of a transport aircraft in icing conditions is carried out in order to develop mathematical model of aerodynamics in the extended flight envelope. The wind tunnel results are validated through flight tests conducted for the real aircraft. Large, glaze-horn ice shapes, corresponding to holding flight phase, are considered. Influence of an ice protection system as well as its failure is examined. Effect of icing on the unsteady aerodynamics characteristics is studied not only through wind tunnel tests but also via analysis of subsequent influence on the flight dynamics of the aircraft. The conducted study shows that the ice shapes of the holding phase lead to reduced stall angle of attack (AoA), maximum lift, and longitudinal damping. Flight dynamics analysis demonstrates that dangerous aircraft behaviour in the form of high AoA departure and limit cycle oscillations (LCO) can be observed at smaller elevator deflections for the iced aircraft. The account for icing influence on the unsteady aerodynamics in the flight dynamics simulations revealed degradation of the dynamic response and deterioration of phase portraits of the system. Even for small AoA and elevator deflection, the aircraft might be trapped into the basin of attraction of high-AoA LCO. In addition, incorporating icing effects in unsteady aerodynamics manifest larger amplitude of LCO.

Six degrees of freedom flight simulation of tilt-rotor aircraft with nacelle conversion

This paper presents six degrees of freedom flight simulation with mode conversion between airplane mode and helicopter mode as an application for realizing Digital Flight of the tiltrotor aircraft. The tiltrotor aircraft has the characteristics of both helicopters and propeller planes with changing the flight mode by tilting the engine nacelles. However, much less work with continuously changing these modes has been done so far. In this paper, the main components such as rotors, engine nacelles, fixed wings and a fuselage are considered. In order to perform large deformations of mesh geometry such as the rotation of the rotor and nacelle as well as the change of the position and attitude of the aircraft, the computational domain is decomposed into multiple domains corresponding to each component. Independently moving these domains makes possible to perform the characteristic behavior of a tiltrotor aircraft. To deal with rotations of multiple decomposed domains, the multi-axis sliding mesh approach is applied. As the solver for simulating unsteady flow driven by complicated moving boundaries, the unstructured Moving-Grid Finite-Volume method is adopted. Based on this solver, the Moving Computational Domain method enables the aircraft to fly in any size of region without restriction of mesh size. The airframe is treated as a rigid body, and the coupled simulations considering interaction with surrounding fluid of the aircraft are demonstrated. The result shows complicated fluid phenomena around the tiltrotor aircraft that occur when it flies with mode change.

Engine Modeling for Small-Disturbance-CFD Related to Aircraft Flutter Investigations

Aeroelastic behavior of aircraft is significantly affected by the presence of engines mounted under the wings. Powered engines influence the unsteady aerodynamics on the one hand and lead to additional unsteady forces due to thrust vector oscillations on the other hand. This work focuses on the incorporation of aerodynamic engine effects into a small disturbance CFD framework to enhance the modeling accuracy of unsteady aerodynamics of aircraft. The effects are numerically modeled by mimicking physically reasonable flow conditions at the intake and nozzle planes of the engine nacelle. Subsequently, the influence of the engine effects on the flutter behavior of an aircraft is studied employing the small-disturbance-CFD-based flutter analysis. The basis for the investigation is the Common Research Model, which represents a modern transonic commercial airliner with a cruise Mach number of 0.85. Two configurations are considered: aircraft with passive engines represented by flow-through nacelles and aircraft with powered engines, where the novel small disturbance engine model is applied. The results are compared in terms of the flutter trends and the predicted flutter boundary. Furthermore, the impact of the modal induced thrust oscillations on the aeroelastic behavior of the aircraft is discussed.

Fault Detection, Isolation and Adaptive Augmentation for Incremental Backstepping Flight Control

Uncertainties caused by unforeseen malfunctions of the actuator or changes in aircraft behavior could lead to aircraft loss of control during flight. The paper presents a Two-Layer Framework (TLF) augmenting Incremental Backstepping (IBKS) control algorithm designed for an aircraft. IBKS uses angular accelerations and current control deflections to reduce the dependency on the dynamics model. Nevertheless, knowledge of the control effectiveness is still required for proper tracking performance and stability guarantee and becomes essential in a case of failure. The proposed TLF is designed to detect possible problems such as a failure or presence of unknown actuator dynamics and to adapt the control effectiveness. At the first layer, the system performs detection and isolation of possible failures. After a problem being detected and isolated, the algorithm initiates the second-layer adaptation of the individual effectiveness of the failed control effector. For some critical scenarios, when the input-affine property of the IBKS is violated, e.g., for a combination of multiple failures, the IBKS could lose stability. Meanwhile, the proposed TLF-IBKS algorithm has improved tracking and stability performance.

Industrially Inspired Gust Loads Analysis of Various-Aspect-Ratio Wings Featuring Geometric Nonlinearity

This paper considers the effect of geometric nonlinearity on gust load analyses of high-aspect-ratio commercial aircraft. Three variants of a conceptual aircraft, featuring wing aspect ratios of 10, 18, and 26, are sized using an industrially inspired procedure to obtain realistic structures of existing and future designs. These aircraft are modeled in a nonlinear aeroelastic framework, featuring a geometrically exact beam formulation coupled with unsteady aerodynamics, and subjected to a gust loads process adapted for nonlinear systems. The gust analysis is also carried out using a linear approach (linearizing the equations of motion about an undeformed or trimmed geometry) to understand how nonlinearities influence the loads and dynamic behavior of aircraft as the aspect ratio increases. Load envelopes show that vertical shear and bending moments are predicted well by the linear analyses, even for the aspect-ratio-26 case, providing that the linearization is performed about the trimmed geometry. In contrast, the in-plane and axial loads are significantly underestimated using linear analyses. Torque behavior is problem specific and therefore difficult to generalize. Even on the aspect-ratio-10 case, which would traditionally be considered as a linear problem, it can be shown that the torque loads are considerably affected by nonlinearity.

Numerical and experimental study of aircraft structural health

The purpose of this work is to monitor the structural health of the Portuguese Air Force (PoAF) EPSILON TB30 fleet by measuring the dynamic behaviour of aircraft’s critical components towards the optimization of maintenance programme scheduling. The mission load spectrum and the structural response are simultaneously measured using a combination of accelerometers and strain-gauges, enabling the calculation of individual transference functions for each critical component monitored. The EPSILON TB30 fleet was divided into two different types of aircrafts: a) IMA-Highly Instrumented Aircrafts which are able to capture vertical accelerations and strain at critical locations and b) LIA-Less Instrumented Aircrafts that make use of the transference functions for mapping the captured acceleration data to stress at pre-selected structural hotspots. The fleet operation is continuously analysed to calculate the fatigue damage of each component and predict the operation limit for each aircraft. In this context, finite element models of critical components are used to define the critical locations of sensors used for monitoring stress in those locations. The maximum principal stress zones of the 2nd bulkhead beam was obtained and are consistent with the manufacturer’s reports that place fatigue crack initiation near the bottom filleted joint of the innermost rib, during real scale fatigue test. Mission is analysed using the structural health monitoring platform PRODDIA™ Aero which uses time and frequency-based fatigue models to predict the structural health of the entire fleet.

Safe limits, mindful organizing and loss of control in commercial aviation

In commercial aviation, loss of control (LOC) incidents are currently the single biggest cause of accident fatalities. Although LOC incidents typically have multiple causes, inappropriate flight crew responses to unfamiliar conditions are a major contributor. It has been suggested that restricted exposure to unusual aircraft behavior and limited manual flying are partly responsible for this, both of which are aggravated by high levels of flight deck automation. In this paper, we draw on ideas from human-automation interactions, organizational limits, mindful organizing and sensemaking to explore how systems that are very safe by design may subtly undermine mindful organizing, reducing the ability of operators to handle unusual and expected situations. We discuss “the paradox of almost totally safe systems” (Amalberti, 2001) and argue that as systems become safer by design it is increasingly difficult for operators to handle unusual, extreme events, partly due to an erosion of mindful organizing and partly to the limitations of existing training and simulation.

Investigating the potential of using glass foam for an EMAS material to mitigate aircraft overrun accidents

ABSTRACT An aircraft overrun occurs when an aircraft is unable to stop within the runway design length. Commercial airports are required to have a 305 m (1000-ft) runway safety area (RSA) at each runway end to avail an aircraft adequate length for stoppage during an overrun. At airports where this space is unavailable, the Federal Aviation Administration (FAA) allows for an airport to use an Engineered Materials Arresting System (EMAS). An EMAS is positioned within the RSA and is comprised of an energy absorbing material that brings the aircraft to stoppage through drag forces developed at the tire-EMAS interface. EMAS are constructed using low-density 1.21 m × 1.21 m (4-ft × 4-ft) variable thickness cementitious blocks. The blocks are aligned adjacent to one another to form a rectangular EMAS bed within the RSA. This article presents the computer code, SGAS, developed by the author to predict aircraft stopping distance and behaviour of current aircraft types within an EMAS. The SGAS computer code is validated with results from the FAA ARRESTOR computer code. After validating the SGAS computer code, this article investigates the potential for using glass foam blocks as an alternative EMAS material.

Statistical Data Processing of Two Mobile Objects Behavior in Random Environments Using Simulation Modeling Method

The article substantiates the necessity of using simulation in order to study the behavior of mobile aircraft (MA) in non-deterministic random environments. The purpose of research using a simulation model is to obtain statistical data on the behavior of the MA with antagonistic tasks. The processing of statistical data allows concluding which one of the MA and with which characteristics solves the problem more successfully. An analytical review of papers in this research area is carried out. The results of the analytical review have indicated the relevance of these studies. Methods for solving the problem of studying the MA behavior are probability theory and mathematical statistics, as well as simulation. It is shown that a non-deterministic random environment has many random parameters. A simulation model for studying the MA behavior is developed. Algorithms of the MA behavior are developed for the simulation model. It implemented in Unity3d - a software environment for modeling various processes. For simulation, an object-oriented C # high-level programming language is used. In order to solve the problem of studying the MA behavior, a list of estimates (criteria of behavior) from probability theory and mathematical statistics is defined. The use of a simulation model allows getting many statistical data and processing them in order to determine estimates. A description of the source data and the operation of the software application for solving the problem of modeling the interaction of two mobile objects is given. In the study of behavior, the first and second MA are assigned different tasks. This has determined the MA different goals and the algorithms for their behavior. Algorithms for the simulation of the MA behavior are developed and tests are carried out using a software application. As a result of simulation, statistical data is obtained and processed. The use of a simulation model and the method of its development allows solving the problem for any MA number. Simulation allows predicting the achievement of the MA goal, and with a more complex statement of the problem, selecting the MA number in order to solve the problem.

An investigation of a high-speed ground manoeuvre under optimal control

This paper studies the behaviour of a nonlinear aircraft model under optimal control for aircraft ground manoeuvres, specifically for high-speed runway exits. The aircraft's behaviour on the ground is captured by a fully parameterised 6-DOF nonlinear model, which is developed in this work to model the effects of braking through a combined slip tyre model. A pre-defined cost function is minimised using a generalised optimal control algorithm to obtain an optimal control sequence for a particular manoeuvre-cost function combination. In this paper, three scenarios are investigated for a 45-degree high-speed runway exit: the first control sequence minimises the distance between the aircraft's centre of gravity and the runway centreline; the second maximises the distance travelled by the aircraft during the 20 s of simulation time; the third minimises tyre wear. For each scenario, the generalised optimal control algorithm provides the best possible control inputs. The dynamic response of the aircraft throughout the turn is shown to be dominated by its inertia, which suggests that future controllers will need to begin executing a turn far in advance of entering the corner. The results also provide a benchmark against which the effectiveness of future real-time controllers may be judged.

Two-Layer On-line Parameter Estimation for Adaptive Incremental Backstepping Flight Control for a Transport Aircraft in Uncertain Conditions

Abstract Presence of uncertainties caused by unforeseen malfunctions of the actuator or changes in aircraft behavior could lead to aircraft loss of control during flight. The paper presents two-layer parameter estimation procedure augmenting Incremental Backstepping (IBKS) control algorithm designed for a large transport aircraft. IBKS uses angular accelerations and current control deflections to reduce the dependency on the aircraft model. However, it requires knowledge of the control effectiveness. The proposed identification technique is capable to detect possible problems such as a failure or presence of unknown actuator dynamics even in case of redundancy of control actuation. At the first layer, the system performs monitoring of possible failures. If a problem in one of the control direction is detected the algorithm initiates the second-layer identification determining the individual effectiveness of the each control surface involved in this control direction. Analysis revealed a high robustness of the IBKS to actuator failures. However, in severe conditions with a combination of multiple failures and presence of unmodelled actuator dynamics IBKS could lost stability. Meanwhile, proposed control derivative estimation procedure augmenting the IBKS control helps to sustain stability.

Innovative exploration of safe in-flightcrew escape options

PurposeThe purpose of this paper is to explore various in-flight crew escape options of a prototype transport aircraft and finalize the option offering safest crew egress for different combinations of contingencies and flight conditions.Design/methodology/approachVarious egress options were explored through simulation in a computational fluid dynamics (CFD) software using aircraft 3D CAD model and scalable digital mannequins. For this, certain important contingencies which best describe the extreme aircraft behaviour were identified. Crew escape options, which have least external interference in expected egress trajectory, were selected. Several test simulations representing each feasible combination of contingency, escape option and flight condition were simulated. The option which offers safe crew escape in each test case is deemed to be the safest egress option for the test aircraft.FindingsAmong five options explored, crew escape through forward ventral hatch provided the safest crew escape for all test cases. The selected option was validated for robustness with additional test cases modelling different anthropometric characteristics of 5th and 50th percentile pilot populations with different postures.Originality/valueIn-flight validation of safe crew escape option is infeasible by actual trial. Exploration of safe crew options for required number of test cases by any analytical method or by wind tunnels tests is tedious, time consuming and extremely expensive. On the other hand, exploration of safest crew option by CFD, besides being first of its kind, provides convenient option to configure, test and validate different test cases with unmatched benefits in time, cost and simplicity.

Data Mining-Based Analysis of Alert Messages of Executive Aircraft

Once the years, a large number of alert messages have been stored by aircraft manufacturers, which characterize the aircraft behavior and performance. This way, some aspects such as component failures and aircraft health can be obtained by means of these messages in order to make decisions and better manage the aircraft. However, these messages are stored faster than can be processed by the reliability engineering team. Motivated by this fact, this paper proposes the use of Data Mining to determine sequential patterns of messages. In this context, it can be observed that the use of Data Mining may contribute to prevent aircraft accidents and reduce the time of maintenance. Therefore, this paper presents a methodology based on the Apriori algorithm to extract association rules from a database of messages sent by executive aircraft operating in Latin America. It is important to highlight that the proposed method was validated using a databaseprovided by a real aircraft manufacturer. Finally, the results obtained by the Apriori algorithm were analyzed in contrast with specialist's knowledge, for known messages, where the method robustness could be validated since the associated messages always had a systemic cause for such emergence.

Study of morphing winglet concepts aimed at improving load control and the aeroelastic behavior of civil transport aircraft

Study of morphing winglet concepts aimed at improving load control and the aeroelastic behavior of civil transport aircraft

Research on Modeling Maritime Patrol Behavior of Aircraft on Station in Theater-Level Operation Simulation

In order to meet the needs of multiple types of maritime patrol aircraft for patrol missions in theater-level operation simulation, this paper builds a patrol behavior model for maritime patrol aircraft based on search type and on-station type. First of all, the search types of maritime patrol aircraft were divided into patrol, orbit, buoy and buoy/patrol based on the motion characteristics and the ability of searching submarine of different types of maritime patrol aircraft (fixed-wing patrol aircraft, patrol helicopter and patrol unmanned aerial vehicle system). Secondly, a comprehensive analysis and description of the geometry of on-station area (point, line, surface and complex) was made based on the movement characteristic of the target assets and the on-station types were divided into picket, barrier, screen, fixed region, sector and complex. Finally, the patrol behavior rules of maritime patrol aircraft on station were described based on search type and on-station type and got the patrol behavior model of the maritime patrol aircraft, which is suitable for multiple types of maritime patrol simulation.

ESWIRP: European Strategic Wind tunnels Improved Research Potential program overview

“European Strategic Wind tunnel Improved Research Potential” ESWIRP was a project in the EU 7th Framework Program (FP7—Grant agreement no: FP7-227816), which was aiming at improving the performance capabilities of three strategic wind tunnels in Europe, by strengthening the cooperation between these wind tunnels in a new consortium. The research consortium members are Office National d’Etudes et de Recherches Aérospatiales (operating the S1MA as its largest sonic wind tunnel), German–Dutch wind tunnels [operating the large low-speed facility (LLF) as its largest low-speed wind tunnel], and European transonic wind tunnel (ETW) (operating its cryogenic wind tunnel). Together, these wind tunnels cover a wide range of experimental capabilities of relevance to civil aviation and aeronautical research in general. The project started in October 2009 for a period of 5 years. The European financial contribution was €7.2 million. The project consist of two major parts: (1) improvements to the testing infrastructure; and (2) the provision of wind tunnel access to research groups which do not usually have the means to access such large-scale test facilities. These topics also involved public dissemination and information activities. Although the tunnels covered in this project are of a complementary nature, the infrastructure activities were joined together, by a common representation of, and approach to, the tunnel performance characteristics. To this end, a generic model of a virtual wind tunnel was developed, enabling operators to assess the effect of the control parameters upon the testing conditions. The final aim of all participants was to provide the user community with an improved set of capabilities to test their innovative ideas. To provide better access to these three major wind tunnels, mainly research groups from European universities were contacted. The approach taken has included maximum transparency of the process and support of the researchers by the organizations responsible for the tunnels. In addition, when possible, we encouraged research groups to work together, to obtain the full benefit of economies of scale in research projects. ESWIRP responded to the targeted approach of the Integrating Activities of the FP7 Capacities Work Program: Networking activities, essentially focused around four topics: (1) organization of information campaigns, lectures and workshops to disseminate knowledge between the partners and future users. (2) Opening of a website for the consultation of wind tunnel standards. (3) Exchange of personnel between the Consortium partners, to foster the spread of good practices and the exchange of technical know-how. (4) Joint development of a reference wind tunnel parameter database. Trans-national access and/or testing services: after the call for proposals by the facility providers, groups of researchers had the opportunity to benefit from free wind tunnel services, including technical assistance to support the corresponding scientific research team(s). Joint research activities, innovative modeling of wind tunnels has helped designers to make better decisions, before the implementation of any novel hardware. Based on a generic finite volume type of modeling approach, the operational behaviour and the time-dependent flow quantities around the wind tunnel circuit have been simulated. Such model can be used, for example, to conceive and tune particular sub-system control laws, or explore the implications of hardware changes. Based on a common approach, dedicated models were developed for S1MA, LLF and ETW. The infrastructure improvements targeted the capability to obtain unsteady test data (with high accuracy) in the ETW, to improve the capability to simulate aircraft behaviour in ground effect in the LLF, and to establish a reliable closed-loop control of test Mach number in the S1MA wind tunnel. European Strategic Wind tunnels Improved Research Potential Program is European support for strategic wind tunnels, key research infrastructures in the development process of current and future aircraft. This is the first time that European authorities have given such support.

Research on Modeling Maritime Patrol Behavior of Aircraft on Station in Theater-Level Operation Simulation

Research on Modeling Maritime Patrol Behavior of Aircraft on Station in Theater-Level Operation Simulation

Analysis of safety characteristics of flight situation in complex low-altitude airspace

This article studies on the analysis of safety characteristics of flight situation in complex low-altitude airspace with Agent-based simulation. Several aircraft behavior models are proposed taking...

Development of Nonlinear Flight Mechanical Model of High Aspect Ratio Light Utility Aircraft

The implementation of Flight Control Law (FCL) for Aircraft Electronic Flight Control System (EFCS) aims to reduce pilot workload, while can also enhance the control performance during missions that require long endurance flight and high accuracy maneuver. In the development of FCL, a quantitative representation of the aircraft dynamics is needed for describing the aircraft dynamics characteristic and for becoming the basis of the FCL design. Hence, a 6 Degree of Freedom nonlinear model of a light utility aircraft dynamics, also called the nonlinear Flight Mechanical Model (FMM), is constructed. This paper shows the construction of FMM from mathematical formulation, the architecture design of FMM, the trimming process and simulations. The verification of FMM is done by analysis of aircraft behaviour in selected trimmed conditions.

The AutoSOAR autonomous soaring aircraft, part 1: Autonomy algorithms

AbstractAutonomous soaring has the potential to greatly improve both the range and endurance of small robotic aircraft. This paper describes an autonomous soaring system that generates a dynamic map of lift sources (thermals) in the environment and uses this map for online flight planning and decision making. Components of the autonomy algorithm include thermal mapping, explore/exploit decision making, navigation, optimal airspeed computation, thermal centering control, and energy state estimation. A finite state machine manages the aircraft behavior during flight and determines when changing behavior is appropriate. A complete system to enable autonomous soaring is described with special attention paid to practical considerations encountered during flight testing. A companion paper describes the hardware implementation of this system and the results of a flight test campaign conducted at Aberdeen Proving Ground in September 2015.