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Icing is one of the main external environmental factors that causes aircraft to lose control. The flight safety assurance system under icing condition is particularly important. However, most of the systems do not consider the coupling characteristics of aerodynamics and flight dynamics of icing aircraft. This will affect the accuracy of the calculation results. Besides, the icing risk management system helps the pilot to realize the possible dangers in advance and perform correct maneuvers, based on quantitative assessment and visualization methods of flight risk. The envelope protection system realizes flight safety guarantee based on the real-time boundary protection method of key flight parameters. Finally, based on distributed simulation technology, a flight simulator was used as a platform to integrate the icing risk management system and envelope protection system to realize man-in-the-loop simulation. Two fictional but historically motivated icing scenarios are designed to test the system, and the results demonstrate that the icing risk management and protection system would be useful for aviation safety and can also be used for pilot training and reproducing flight accidents to find the causes.

A high-order tiltrotor mathematical model is developed and validated against flight-test data for the XV-15 and simulations of a large civil tiltrotor (LCTR) concept. Rigid body and inflow states, as well as flexible wing and blade states are used in the analysis. Wing flexibility is important when modeling large aircraft where structural modes effect the frequency range of interest for flight control, generally 1–20 rad/s. Details of the formulation of the mathematical model are given, including derivation of structural, aerodynamic, and inertial loads. A novel "quasi-multibody" approach, based on numerical kinematics but without equations of constraints, allows the modeling of complex, flexible aircraft configurations in an easy to set up, and computationally very efficient manner. Assessments of the effects of wing flexibility are given. Flexibility effects are also evaluated by looking at the nature of the couplings between rigid body modes and wing structural modes.

This paper presents a dynamical analysis of a tethered aerostat using a multibody simulation tool called SimscapeMultibody™. Tethered aerostats are lighter than air vehicles that float in the air and are connected to the ground through the tether. Atmospheric winds are a source of disturbance to the aerostat. The wind produces drag force that causes the aerostat to displace from its mean position. This phenomenon is called blow-by. Solving the mathematical model of the motion dynamics with time step is the conventional method used for simulating the flight dynamics of the aerostat. This paper discusses the application of Simscape Multibody™ for the three-degrees-of-freedom flight dynamic simulation of spherical tethered aerostat. Simscape Multibody™, an extension of MATLAB®/Simulink, is a multibody modeling tool in which physical bodies and their interactions have to be defined to simulate the dynamics. The mathematical model of the defined system is automatically generated by the SimscapeMultibody™ solver, and the system dynamics is simulated. The simulation of dynamics using multibody modeling tools provides high fidelity simulation for the tethered aerostats.

The use of finite-state methods is critical to the development of accurate and efficient inflow models used in rotorcraft flight dynamics simulation and control. Recent work in the finite-state fie...

Vertical flight performance of Lighter-than-Air free hot-air balloons is derived and discussed. Novel mathematical model using lumped-parameters has been used to model balloon flight dynamics and steady-state performance in particular. Thermal model was not treated as the super-heat is under the control of aeronauts/pilots. Buoyancy or gross lift, net or effective lift, specific lift, and excess specific lift were derived for a general single envelope balloon and can be applied to hot-air, gas and hybrid balloons. Rate-of-climb, absolute ceiling, rate-of-descent, and the maximum rate-of-descent or the uncontrolled terminal descent have all been modeled and sample computations performed for AX8 or AX9 FAI-class hot-air balloons. Lifting index or the specific net/effective lift have been computed treating ambient and hot air as ideal gases at various pressure altitudes and representative envelope temperatures. Drag coefficient in upward and downward vertical flights have been chosen based on best available data. Experimental scale and full-scale flight tests are suggested for more accurate estimates of external aerodynamics in vertical balloon flights. CFD computations of coupled inner- and external-flows are also recommended in future efforts. Knowledge of free balloon’s vertical performance is essential in flight planning and operational safety of flight.

Для здійснення автоматизованого управління бойовими порядками спільних авіаційних груп необхідно створення системи математичних моделей етапів функціонування бойового порядку, а також засобів реалізації цієї системи, включно з процедурами управління та інтеграції. Найбільш вдало така задача може бути розв’язана при застосуванні логіко-динамічних моделей та теорії логіко-динамічних систем. Метою статті є створення банку моделей, як системи моделей математичного опису етапів функціонування бойового порядку спільної авіаційної групи, що становить основу математичної моделі бойового порядку спільної авіаційної групи пілотованої та безпілотної авіації. Задача синтезу логіко-динамічних моделей полягає у розділенні вихідної моделі на сукупність структурних станів (режимів), причому систему у кожному структурному стані можна розглядати як самостійну. Моделювання кожного з станів полягає у об’єднанні ряду режимів, що характеризуються постійним значенням аеродинамічних характеристик пілотованих та безпілотних літальних апаратів залежно від значення функцій предикат змінних. Відповідно, модель виконання бойового завдання спільною авіаційною групою пілотованої та безпілотної авіації розбивається на ряд етапів. Зміст задачі дослідження передбачає використання повної нелінійної моделі динаміки польоту без розділення руху на повздовжній, боковий та вертикальний, при прийнятих припущеннях. Визначення заданого відносного положення пілотованих та безпілотних літальних апаратів у бойовому порядку дозволить описати їх спільний відносний рух, що формує особливості системи управління бойовим порядком, а обрання системи координат відносно веденого надасть переваги на всіх подальших етапах розв’язання задачі управління.

The longitudinal flight stability of the ducted vertical take-off and landing fixed-wing UAV during the flight state of hovering and transition is studied. Firstly, based on the Blade-Element Momentum Theory (BEMT) and experimental data, a coaxial dual-rotor ducted aerodynamic model and a thrust ducted aerodynamic model based on characteristic cross-section calculations are established. The model parameters are identified according to the experimental data. Secondly, a UAV flight dynamics model with thrust duct deflection is established according to the six-degree-of-freedom equations. Finally, the case UAV was used to solve the longitudinal balance and stability analysis of hovering and transition state with the established model method, and compared with the hovering experimental results. The results show that the UAV flight dynamics model combined with the ducted dynamic model established in the article can accurately describe the longitudinal flight stability characteristics of this type of aircraft.

Dynamic soaring is an emerging flight range-extension technology that effectively reduces UAV's energy consumption by deriving wind energy from lateral gradient wind fields. Comparing with the small UAV's near the surface, the application of dynamic soaring technology in the high-altitude long-endurance flight requires the additional consideration of the influence of sustained side wind, the influence of the sideslip angle cannot be ignored. This puts higher requirements on the flight dynamics model. In this paper, the dynamic model for the high-altitude dynamic soaring based on the six-degree-of-freedom equation is modeled to replace the traditional mass point model; the energy change principle of the high-altitude dynamic gliding is derived; the effect of the high-altitude wind field on the dynamic soaring UAV is analyzed; and the way to get optimal wind field energy acquisition and energy saving efficiency are analyzed. The results show that the dynamics model based on the six-degree-of-freedom equation can more realistically reflect at high altitude; the application of dynamic soaring can effectively improve the range of the high-altitude UAV; the wind direction at high-altitude wind field has a significant effect on the dynamic soaring efficiency.

Spacecraft formation flying in co-planar identical orbits with oppositely directed apse lines (eccentricity vectors) allows simultaneous in-situ measurements in different altitudes and time-sequential measurements in a limited altitude range (rapid revisit); a key enabling factor in understanding many poorly understood phenomena in our atmosphere and its interaction with the magnetosphere. The dynamics and control problem for flying formations in mirrored orbits are investigated using the Mechanisms of Energetic Mass Ejection - Explorer (MEME-X) mission concept as a case study. It is determined that the proposed two-craft and four-craft configurations require routine maintenance to correct their relative motion. The formation maintenance costs are quantified for both configurations and determined to be within the capabilities of small satellites. A high-fidelity end-to-end simulation is developed to model the entire two-craft mission concept, from orbit insertion to decommissioning, providing an approximate baseline for the flight dynamics costs of similar missions using multiple spacecraft flying in mirrored orbits.

Prediction of aerodynamic force is a crucial issue for parafoil canopy as the strong nonlinear fluid–structure interaction (FSI) between the flexible canopy material and flow field. Flight tests and wind tunnel experiments are difficult to analyze the aerodynamics of parafoil because of the limitation and difficulty of data measurement in an unknown environment. The objective of this study was to computationally derive the aerodynamic characteristics of parafoil, as an alternative to expensive and unrepeatable test regimes. Different from previous works that assume canopy structure as a rigid body and serve for the design of parafoil, this study focused on the precise dynamic modeling of parafoil based on FSI simulations. To investigate the aerodynamic performance of the full-scale canopy with stabilizers for better control, the strong coupling FSI simulations were performed using the incompressible computational fluid dynamics techniques. The highlight of this paper is to explore the effects of canopy inflation and trailing edge deflections on aerodynamic performance. Then the aerodynamic coefficients are identified by a linear regression method using the obtained database of high fidelity lift and drag forces. Furthermore, an accurate six-degree-of-freedom dynamic model of the parafoil system is implemented based on the estimated coefficients. Simulations are conducted to prove the dynamic stability of the model and the feasibility of trajectory tracking. At last, simulation results of basic motions are compared with airdrop testing data, which demonstrates that the established model is capable of accurately predicting the flight behaviors of the parafoil system.

In this paper, a numerical method is proposed for determining the periodic state and control solutions of nonlinear time-periodic systems. Starting from an initial guess at the solution, the algori...

During the subsequent deploying process after the launch, the vehicle experiences dramatic changes in geometry as well as aerodynamics, which cannot be ignored for the flight stability of the aircraft. The investigation on the flight dynamics modeling and stability analysis during the unsteady deploying process is of great significance for the flight control system design and the launch system design. The nonlinear multibody dynamic model of the vehicle, which mainly consists of the airframe and four wings, is established through the Newton–Euler method. Meanwhile, the unsteady vortex lattice method (VLM), which is suitable for tandem wing aircraft and combined with the viscosity effect in light of the strip theory, is proposed to calculate the aerodynamic loads of the vehicle during the deploying process. A series of simulations about the motion of the vehicle after the launch are calculated to analyze the effects of various parameters, including the deploying forms, the start-up time of the power system along with the launching parameters, on the stability of the aerial vehicle in the deployment process. As results indicated, a small difference in the deploying rates of wings and larger deploying rates of wings on the same side are beneficial to the stability of the vehicle during the deploying process. Additionally, it is advantageous to the pitching stability but not the lateral stability of the vehicle when the power system is started earlier. Besides, the attitude control strategy of the vehicle can be formulated in advance by analyzing the attitude of the vehicle with different launch parameters at the launching moment.

This Paper discusses the results of an experimental study to investigate the performance of a converging nozzle with fluidic thrust vectoring, using secondary-jet injection, through the measurement...

An experimental remotely piloted aircraft named X-HALE was designed and built at the University of Michigan to collect experimental data for the flight dynamics of vehicles with very flexible wings...

This paper studies the influence of flared-hinge folding wingtips on the aerodynamic derivatives and flight dynamics of a narrow-body transport aircraft. In addition, the influence of fold angle, h...

Driven by their versatility and autonomy, advanced unmanned aerial systems have indicated substantial promise along the development of current communication networks, as well as in support of new communication platforms. The resulting integration of robotic and communication systems brings increased levels of complexity, which cannot be modeled accurately by conventional approaches. An example of this are aerial synthetic aperture antennas, in which an aerial robotic swarm coordinates their flight patterns and communication exchanges to produce a synthetic aperture. The accurate representation of such a system mandates the careful simulation of wireless communications, antenna radiation patterns, flight dynamics, and even environmental conditions. This article details an integrated communications and robotics simulation framework, which enables the assessment of these emerging systems. The benefits of this new approach are illustrated for the aerial synthetic aperture antenna example, but extend to a wide array of problems stemming from the union of communications and robotics. This novel modeling platform makes it possible to design and analyze joint flight and communication protocols for unmanned aerial systems. The obtained results provide valuable insights into the operation of swarm-based synthetic aperture antennas. Moreover, the methodology introduced in this work is flexible and can be readily applied to other instances of joint communication and robotic systems. acceptedVersion

As an unmanned system, the multirotor has gained widespread attention in practical aviation engineering, because of its ease of use, reliability and maintainability. From the perspective of flight reliability and safety, it is significant and essential for a multirotor to detect anomaly occurrences and evaluate the real-time health performance status in a timely manner. Considering the limitations in the modeling of multirotor dynamics and the state estimation of existing methods, a health performance evaluation method of multirotors under wind turbulence is proposed in this paper. First, a stochastic hybrid system (SHS)-based model is established to describe the dynamic behavior of the multirotor, where the flight dynamics, external disturbances due to wind turbulence, and dynamics of discrete modes are included. The real-time probability distribution of the hybrid state of the SHS-based multirotor model is obtained by a modified interacting multiple model particle filter algorithm. Based on this, the real-time overall health performance status of the multirotor during flight is quantitatively evaluated by the classical health degree and the fuzzy health degree as indicators. Finally, a multirotor suffering from different types of sensor anomalies is simulated to demonstrate the availability and effectiveness of the proposed method.

The article addresses investigating the possibilities of making a parameterized flight dynamics model in a mixed reality environment. The purpose was to obtain a model for a Mi-17 helicopter. The Mi-17 VI helicopter flight test characteristics were used to evaluate the above model. As a comparative criterion, compatibility between the model’s selected characteristics and the real object was adopted. Simulation tests were conducted on a cabin simulator set made via MR (mixed reality) technology. Test results confirmed the possibility of reconstructing the selected helicopter type’s flight dynamics using the parameterized model.

The new aeronautical structures have become more flexible and light weight to reduce energy consumption, emissions, and noise, and to operate at high altitudes for long periods in the air, such as those required in the NASA Helios project. The increased structural flexibility of these aircraft has reignited concerns related to aeroelastic instabilities, such as flutter. Improving the techniques and methods used in aircraft certification flights is an important concern of the aeronautical community, because current standards and procedures do not provide recommendations and guidelines for aircraft with a high degree of flexibility. The techniques traditionally used in commercial airplanes cannot be used in this new aircraft concept, because they have a high degree of non-linearity in their flight dynamics. Current research indicates an increasing awareness about the importance of vision in the monitoring of UAV structural health. This work presents a new methodology to measure natural frequencies of aeronautical structures using a computer vision system. We also discusses new approaches to sense and acquire vibration data on aeroelastic certification flights test. These new approaches aim to reduce both the time required to identify the aeroelastic phenomenon and the size of the hardware that must be boarded on the aircraft, thus minimizing the risks and costs of the vibration tests. The advance of computer vision systems enables the use of cameras as a motion tracker sensor with millimeter precision and accuracy. Non-contact sensors are suitable for flutter analysis because they do not interfere with the dynamics of the aircraft. Therefore, this new methodology is able to process the obtained images and provide the user with the data about movements in a ready to use vector, at a reasonable cost. Using the data provided by this methodology the natural frequencies of the first bending modes were identified. This new methodology can be a user-friendly tool to support the Brazilian National Civil Aviation Agency - ANAC program called iBR 2020, which aims to certify small aircraft.

During the lifetime of an operational spacecraft, a situation may occur when it faces a close approach with other orbiting space objects. The mitigation strategy for minimizing threat from orbiting space objects is to first carry out proximity analysis for operational spacecraft's (primary) with all other catalogued orbiting space objects (secondary). In case of a possible close approach, to plan an evasive collision avoidance maneuver. The ever-increasing number of space objects around the Earth demands this kind of analysis on daily basis by satellite operators. Presently, ISRO is operating close to 50 satellites in LEO and GEO/GSO orbits and this number is increasing each year at a rapid rate. At present the NORAD TLE catalogue consists of more than 18000 unclassified space objects. The large number of object pairs require enormous amount of computational load to do such kind of analysis on daily basis. Therefore, an efficient and user-friendly tool to predict the future close approaches is necessary for satellite operators. In this paper, methodology is designed and developed for carrying out conjunction analysis for all operational satellites with catalogued space objects. In the design, efficient approach is adopted to reduce the computation time. Each object pair goes through screening process using pre-filters like perigee-apogee test and smart sieves. These filters are based on basic flight dynamics rules. Only those pairs which are passed by all filters are subjected to relative distance function method for finer assessment. For the candidate pairs which violate the specified minimum Inter-Satellite-Distance (ISD) limit, collision probability is computed. For operational satellites, latest available orbit determination results at control centre are used and orbit propagation is done with high fidelity ephemeris model. Orbit propagation of catalogued objects with TLE is done using SGP4 model. Using this design methodology, Close Approach Prediction Software (CLAPS) is developed in C++ language, to predict the future close approaches for multiple operational satellites with complete TLE catalogue in single run. CLAPS s/w is tested for various close encounter cases and results are validated with STK's AdvCAT tool. The close approach time and minimum distance are found to match up to millisecond and millimetre level respectively. The results of few actual close approach scenarios are presented and discussed. CLAPS is being used regularly at ISRO's Master Control Facility, Hassan for routine monitoring of close approaches.

Loss-of-control has become the largest fatal accident category for worldwide commercial jet accidents, and any initiative aimed at preventing such events requires an understanding of the fundamental aircraft behavior, especially the flight dynamics at post-stall region at which loss-of-control usually occurred. A series of low-speed static and dynamic wind tunnel tests of the Common Research Model over a large angle of attack/sideslip envelope was conducted and a non-linear aerodynamic model was developed. The bifurcation analysis, complemented by time-history simulation was used to understand the post-stall flight dynamics and the numerical analysis results were preliminary validated by wind tunnel virtual flight test. Several representative post-stall behaviors for the transport aircraft have been identified, including departure, periodic oscillation, post-stall gyration and steep spiral, etc. Furthermore, the predicted periodic oscillation in pitch motion has been perfectly duplicated in wind tunnel virtual flight test. The approach used in this work shows a promising way to uncover the flight dynamics of transport aircraft at extreme and loss-of-control flight conditions, as well as to apply to nonlinear unsteady aerodynamics modeling and validation, flight accident investigation, advanced flight control law design or studying initiative for loss-of-control prevention or mitigation.

A new filtering approach is presented, able to estimate online the aerodynamic characteristics of tethered wings used in airborne wind energy systems. The approach is based on the extended Kalman filter (EKF) and on a representative model of the flight dynamics. The filter is fed with measurements available at the ground station, namely, the line angles and their rates, the traction force on the tether, and the wind speed and direction a few meters above the ground. Convergence and accuracy of the estimates are first evaluated through simulations. Then, the approach is demonstrated using extensive experimental data, collected during field tests with two small-scale prototypes built independently by different research groups and four different flexible airfoils (power kites), of both ram-air type and of leading-edge-inflated type. The experimental results show that the algorithm can effectively estimate both the state and the aerodynamic parameters of the wings, as well as the wind speed and direction at the wing’s altitude, and makes it possible to analyze the kite aerodynamics during highly dynamical tethered flight.

This report investigates the flight dynamics of a small-scale (2 ft) towed system using a quadcopter and actively controlled payload. A towed system includes a main driver to propel the system forward connected to a payload via a tether. The towed system here is unique, and in that the driver is a scratch built quadcopter while the payload is also a scratch built actively controlled aircraft. The payload is designed to carry a small instrument that must be sufficiently far away from all interferences created by a quadcopter. A fully non-linear full state model is created and utilized to reveal that oscillations in the payload are decreased with the introduction of a PD controller on the payload. An experimental setup is built to validate simulation results. Experiments show that an actively controlled payload can decrease the attitude oscillations of the payload.

Successful demonstrations of controlled flight in flying insect-sized robots (FIRs) $ 500 mg have all relied on piezo-actuated flapping wings because of unfavorable downward size scaling in motor-driven propellers. In practice, the mechanical complexity of flapping wings typically results in large torque bias variability about pitch and roll axes, leading to rapid rotation in free flight for vehicles that are not properly trimmed. Manual trimming by watching high-speed video is tedious and error-prone. In this letter, we introduce an alternative, a trimming device that uses feedback from motion capture cameras to determine and correct for bias torques. It does so using an automated feedback loop, without the need for any visual feedback from the user, or airborne flights which can damage the robot. We validated the device on two different robot flies. After trimming with our device, the robots both took off approximately vertically in open-loop and were able to hover in free flight under feedback control. Our system, therefore, reduces the time of essential yet time-consuming step in robot fly fabrication, facilitating their eventual mass production and practical application.

A recent consideration in aircraft design is the use of folding wing-tips with the aim of enabling higher aspect ratio aircraft with less induced drag, but also meeting airport gate limitations. This study investigates the impact of floating folding wing-tips on the aircraft flight dynamics. It is found that a floating wing-tips aircraft has similar handling qualities with respect to an aircraft with no wing extension.

This paper studies the flight dynamics and control strategy for electric solar wind sails based on the nodal position finite element method, where the coupling effects between tether dynamics and t...

As part of the upcoming Mars 2020 rover mission, NASA is planning to include an autonomous helicopter to demonstrate the feasibility and utility of using helicopters for Mars exploration. Helicopte...

Limited by its low energy capacity, small UAVs have short flight time. Therefore, it is of great significance to improve the endurance performance of small UAVs by applying solar energy technology and dynamic soaring technology which can obtain external energy. This paper analyzes the energy exchange principle of small UAVs using solar energy technology and dynamic soaring technology, and works out the strategy of maximum energy gain. Small UAV flight dynamics model combined with solar power-energy system was built, choosing surround flight path at twilight moment for simulation validation. The advantages of small solar UAV using dynamic soaring technology in energy acquisition in hovering flight and pure dynamic gliding flight are verified, compared with traditional solar vehicle. The significance of combining the two energy acquisition technologies to improve the endurance of small UAV is proved, which provides a basis for further study of all-weather uninterrupted flight in the future.

A comparative evaluation of the use of various metals and nonmetals as fuel components of a solid propellant containing ammonium perchlorate as an oxidizer and rubber as a binder was performed using the flight range criterion of a rocket-ramjet aircraft taking into account the expected completeness of combustion of individual components. The influence of the energetic properties of the propellant on the technical and economic characteristics and flight performance of the aircraft was also taken into account. The aircraft flight range was calculated by numerical integration of flight dynamics equations. Based on the results, it is recommended that a number of fuel components should be studied in more detail, in particular, for the purpose of the full or partial replacement of boron currently used in solid propellants for rocket-ramjet engines.

An accurate description of the transition corridor is of great significance for the flight process of the vertical take-off and landing (VTOL) fixed-wing unmanned aerial vehicle (UAV). To study the transition flight process of vertical take-off and landing fixed-wing UAVs, the dynamic model and transition corridor model of this type of UAV are established in the current article. The method for establishing the model is based on a reasonable match of the power and aerodynamic force of this type of UAV. From the perspective of flight dynamics, the ducted lift-increasing system’s deflection angle–speed envelope is studied with the maximum lift coefficient of the wing and the system’s available power. The influence of the overall parameters and energy parameters of the UAV on the deflection angle–speed envelope of the ducted lift-increasing system is analyzed, and a method is proposed to expand the vertical take-off and landing fixed-wing UAV’s transition corridor. Taking the UAV as the object, using the established model, the transition flight corridor of the UAV is obtained, the influence of the control parameters on the transition flight is studied, and the appropriate transition flight control strategy is determined. At the same time, the influence of the overall parameters and energy parameters on the transition corridor is calculated. According to the calculation results, the effect of expanding the flight corridor of the UAV is more obvious when increasing the available power than when increasing the aerodynamic parameters by the same proportion.

RocketPy is a new open-source Python library specialized in trajectory simulations of sounding rockets and high-powered rockets. Having a modular structure and being built on top of a six d...

INTRODUCTION: Aerobatic flight operations involve a higher level of risk than standard flight operations. Aerobatics imposes considerable stresses on both the aircraft and the pilot. The purpose of this study was to analyze civilian aerobatic aircraft accidents in Australia, with particular emphasis on the underlying accident causes and survival outcomes.METHODS: The accident and incident database of the Australian Transport Safety Bureau was searched for all events involving aerobatic flight for the period 19802010.RESULTS: A total of 51 accidents involving aircraft undertaking aerobatic operations were identified, with 71 aircraft occupants. Of the accidents, 27 (52.9) were fatal, resulting in a total of 36 fatalities. There were 24 nonfatal accidents. In terms of injury outcomes, there were 4 serious and 9 minor injuries, and 22 accidents in which no injuries were recorded. Fatal accidents were mainly due to loss of control by the pilot (44.4), in-flight structural failure of the airframe (25.9), and terrain impact (25.9). G-LOC was considered a possible cause in 11.1 of fatal accidents. Nonfatal accidents were mainly due to powerplant failure (41.7) and noncatastrophic airframe damage (25). Accidents involving aerobatic maneuvering have a significantly increased risk of a fatal outcome (odds ratio 26).DISCUSSION: The results of this study highlight the risks involved in aerobatic flight. Exceeding the operational limits of the maneuver and the design limits of the aircraft are major factors contributing to a fatal aerobatic aircraft accident. Improved awareness of G physiology and better operational decision-making while undertaking aerobatic flight may help prevent further accidents.Newman DG. Factors contributing to accidents during aerobatic flight operations. Aerosp Med Hum Perform. 2021; 92(8):612618.

The flight dynamics and flight envelope of coaxial ultralight helicopter CoAX 2D were investigated. For this purpose, series of flight tests was carried out. This paper presents the computation of the fuselage aerodynamics of the CoAX 2D with the DLR flow solver TAU. For cruise flight, fuselage polars with different angles of attack and yaw angles without rotor downwash were calculated. Furthermore, different airspeeds, climb and sink rates were simulated in combination with rotor downwash. To simulate the rotor downwash from the coaxial rotors, the Actuator Disc approach is used. The lift of the horizontal stabilizer is compared between flight test and simulations for validation purposes. The lift was determined in the flight test by deflection of the tail boom. Finally, concepts for the optimization of the fuselage were developed. The landing gear was selected as a possible optimization potential. The changes from an aerodynamic point of view related to the shape of the skid supports. The aerodynamics of the new landing gear were compared with the old configuration and a reduction of drag could be shown.

In this study, the observational arc-length effect on orbit determination (OD) for the Korea Pathfinder Lunar Orbiter (KPLO) in the Earth-Moon Transfer phase was investigated. For the OD, we employed a sequential estimation using the extended Kalman filter and a fixed-point smoother. The mission periods, comprised between the perigee maneuvers (PM) and the lunar orbit insertion (LOI) maneuver in a 3.5 phasing loop of the KPLO, was the primary target. The total period was divided into three phases: launch–PM1, PM1–PM3, and PM3–LOI. The Doppler and range data obtained from three tracking stations [included in the deep space network (DSN) and Korea Deep Space Antenna (KDSA)] were utilized for the OD. Six arc-length cases (24 hrs, 48 hrs, 60 hrs, 3 days, 4 days, and 5 days) were considered for the arc-length effect investigation. In order to evaluate the OD accuracy, we analyzed the position uncertainties, the precision of orbit overlaps, and the position differences between true and estimated trajectories. The maximum performance of 3-day OD approach was observed in the case of stable flight dynamics operations and robust navigation capability. This study provides a guideline for the flight dynamics operations of the KPLO in the trans-lunar phase.

An enhanced nonlinear aeroelastic-coupled-flight dynamics framework that enables the investigation of propeller aerodynamics and inertial effects on the response of a very flexible aircraft is pres...

Airborne Wind Energy (AWE) is a promising new technology, and attracts a growing academic and industrial attention. Important research efforts have been deployed to develop prototypes in order to test the technology, generate control algorithms and optimize the efficiency of AWE systems. By today, a large set of control and optimization methods is available for AWE systems. However, because no validated reference model is available, there is a lack of benchmark for these methods. In this paper, we provide a reference model for pumping mode AWE systems based on rigid wings. The model describes the flight dynamics of a tethered 6 degrees of freedom (DOF) rigid body aircraft in form of differential-algebraic equations, based on Lagrange dynamics. With the help of least squares fitting the model is assessed using real flight data from the Ampyx Power prototype AP2. The model equations are smooth and have a low symbolic complexity, so as to make the model ideal for optimization and control. The information given in this paper aims at providing AWE researchers with a model that has been validated against flight data and that is well suited for trajectory and power output simulation and optimization.

This paper presents a real-time simulation model for the analysis of the helicopter flight tasks in turbulent atmospheric environment. First, recursive algorithms are developed for independent turbulence components by discretizing the high-order turbulence filters deduced from the von Karman model. Then, the discrete filters are related according to the spatial correlation on transverse planes. The related filters are distributed in front of a helicopter and their turbulence components are transported along the longitudinal direction of airspeed to establish a distributed turbulence model. Next, the turbulence model is integrated into a flight dynamics model, and a real-time simulation model is formed and validated against flight test data. Finally, the model accuracy and computational speed with simulation step are investigated using numerical simulations. Results show that the model computational speed increases with the increment of simulation step. However, the lower-frequency helicopter motions may be distorted by the higher-frequency turbulence disturbance when a too large simulation step was used. Following the results, appropriate simulation steps are proposed. The model accuracy and computational speed meet the real-time requirements for the helicopter flight simulations in atmospheric turbulence.

This paper focuses on the flight mechanical characteristics of an active high-lift supported transport-type aircraft. The presented configuration combines a boundary-layer controlled flaps system with the benefits of propeller slipstream deflection. The underlying aerodynamic models and assumptions are provided. The extraordinary flight performances especially at low airspeed will be pointed out, as well as potential weaknesses. Special attention is paid to the unusually strong aerodynamic couplings in the lateral motion. Therefore, flight dynamics characteristics will be presented and their challenges discussed. The key influences are pointed out and an outlook will be given, how to exploit this knowledge for safe and satisfactory aircraft operation and handling.

Cases of failure (shutdown) of all the main engines of a multi-engine powerplant in flight, unfortunately, occur both in Russia and abroad. The causes of such situations may be, for example, a flying in volcanic ash cloud, as in the case of the incident with Boeing 747 over the island of Java in 1982, or the cessation of fuel supply, as in the cases of an emergency landing of Boeing 767-233 in 1983 on an unused military airfield Gimlii and Tupolev-204 in Omsk in 2002. At the same time, in the management documentation, the crew’s actions for this case are either not prescribed at all, or spelt out so concisely that they do not imply a specific list of actions, or, in other words, they require the crew to search for the necessary aircraft control actions within the circumstances of time shortage and increased stress levels. The proposed article reveals the content of the methodology that provides for the withdrawal of an aircraft with an inoperative power plant in a safe landing environment at every airfield with an outer marker. A distinctive feature of the considered approach is the absence of the need to bind the parameters of aircraft movement to explicitly stated landmarks. In addition, this approach is simple to implement and at the present stage of development of automatic control systems may well be implemented on board an aircraft in an automatic or director mode. The minimum information required for the calculation of the landing approach is limited to three parameters: the minimum drag airspeed in the landing configuration, the height of the flight over an outer marker before the landing and the height loss on turn spiral on the prelanding manoeuvre. The content of the method in the article is illustrated by the results of the calculation of landing in case of failure of both engines of the power plant for the prospective domestic short-medium-range aircraft MS-21.

The detection and identification for aircraft icing and actuator/sensor fault has been a lasting topic in flight safety researches. The current algorithms are usually tailored for some specific cases (faults/icing locations, magnitude, etc.). Although the performance of the algorithm in the designated cases may be good, the transferring of it to other different cases is usually heavy as parameters tuning or even algorithm redesigning may be required. In this paper, the author advocates exploring a comprehensive scheme that balance both good performance and wide transferability for different cases. Referring to the current advances in other research communities, we follow the state-of-art Deep Learning (DL) and transfer learning (TL) concepts. A scheme for the icing/actuator fault detection using the DL technique is firstly constructed. The TL is then adopted to transfer this scheme to other different tasks, e.g. fault/icing identification, sensor fault detection. Test results show that the TL-enhanced DL scheme exhibits not only good performance for the designated detection task, but also reflects flexible transferability at low tuning efforts. Via this paper the author advocates furtherly exploring the potentials of the novel DL and TL technique as to advancing the researches/techniques in the flight dynamics and control realm.

Airborne wind energy (AWE) is a power production technique aiming to harvest energy from high-altitude winds through tethered aircraft. In the ground-based power generation concept, the aircraft fl...

Since projectiles with large slenderness ratio are prone to elastic deformation, the effect of structural deformation is necessary to be taken into consideration for dynamic modeling. In order to obtain the precise aerodynamic performance and flight dynamic characteristics of flexible projectiles, a new numerical flight simulation system is developed based on computational fluid dynamics and generalized dynamic-mesh technique. Furthermore, flight dynamic stability of a typical flexible projectile is carried out in detail by introducing PID controller. By means of installing the sensors at various locations, the effect of different mode shapes on the characteristics of the closed-loop flight dynamic system is researched. Numerical results indicate that, when the disturbance due to elastic vibration is added into the mixed signals gained from the angular velocity/acceleration sensors, the feedback response of the closed-loop system becomes adversely divergent. In contrast, the stability of the closed-loop system is not sensitive to the elastic disturbance added to the centroid velocity and acceleration. Moreover, the stability of closed-loop system is much less affected by the unsteady aerodynamic loading due to elastic vibration than the interference of the elastic vibration on the dynamic signals detected by the sensors. The phenomenon can be explained by the requirement on the stability of the long and short period modes of flight dynamics, which can provide some guidance for the layout of the sensor and the design of control system of the projectiles with large slenderness ratio.