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BACKGROUND: Since eye movement can provide a reliable index of the attention allocation, which can assist in understanding pilots’ cognitive state, this study investigated the effect of pilots’ experience and the autopilot mode on their attention allocation on the Primary Flight Display (PFD) and Multi-Function Display (MFD) during an approach task.METHODS: There were 16 pilots who were classified into two levels of aviation expertise depending on the flight hours, and required to fly an Instrument Landing System approach. Their visual scanning behaviors were recorded through an eye tracker and analyzed based on fixation number and dwell time.RESULTS: The results revealed that the pilot experience level, instrument panel and autopilot mode all had significant impact on the fixation time ratio and dwell time. The pilots fixated most often on the PFD and had shorter dwell time. Furthermore, they had a lower fixation number and shorter dwell time on the PFD and MFD when the autopilot was off that they should allocate visual resources to the others (e.g., out-of-the-window) and obtain more information to maintain overall situation awareness under higher time pressure. Compared to pilots with more expertise, pilots with less expertise had an increased fixation number and decreased dwell time on the airspeed after turning off the autopilot.DISCUSSION: The present study indicated that the pilots had different visual scanning modes according to the flight mode and their experience. We expect that pilots’ visual scanning behaviors during tasks will help the training and the design of the human-machine interaction.Lu Y, Zheng Y, Wang Z, Fu S. Pilots’ visual scanning behaviors during an instrument landing system approach. Aerosp Med Hum Perform. 2020; 91(6):511–517.

This paper presents a method for estimating the air data parameters for a small fixed-wing, unmanned aerial vehicle (UAV) using an arrangement of low-cost Micro-electromechinal systems (MEMS)-based pressure sensors embedded in the surface of the UAV. The pressure measurements are used in a machine learning (ML) model to estimate the angle of attack, sideslip angle, and airspeed. Two ML algorithms based on artificial neural networks (NNs) and linear regression (LR) are implemented, tested, and assessed using data collected from wind tunnel experiments and a flight test, and the results are compared to a benchmark flight test. Training the ML algorithms using wind tunnel data was found to introduce several potential error sources that need to be addressed in order to provide accurate estimation on the benchmark flight test, whereas training the algorithms using flight data provides lower estimation RMSE values. The performance of the NN structures has been found to slightly outperform the LR algorithms in estimation accuracy. Finally, results from using different sensor configurations and a pseudo-Reynolds number are presented in an effort to evaluate the influence of sensor number and placement on the accuracy of the method.

The main objective of this paper is to design, calibrate and make functional a horizontal test bench used to carry out the experimental simulation of solar reflectors erosion induced by sand particles. The developed equipment provides the possibility to control the air speed, the impact angle between the fluid flow and the target surface as well as the mass rate of the ejected particles. The originality of this work lies on the introduction of a new parameter, identified as, the unified sand mass received by the samples in each test, without considering the experiments conditions (air speed, impact angle, etc.) by acting on the ejected sand mass poured in the sand container. To make the setup operational, a set of calibration tests was conducted under multiple scenarios. The collected data from the calibration tests were analyzed to choose the appropriate configuration. A multiple linear regression function was applied to analyze the influence of the inputs parameters on the tests repeatability. A descriptive equation calculating the amount of sand needed to ensure the unified sand mass, homogeneity and repeatability of the experiments is introduced. The results of erosion simulation carried on solar glass reflectors are also presented; for an air speed of 25 m/s, the reflectance loss is two times greater in 90° (11.03%) than the registered in 45° (5.31%). The developed bench should help researchers to set up their devices for the conduction of advanced experiments ensuring that the obtained results are as repeatable as efficient.

Nevil Shute was a best-selling novelist, aeronautical engineer and managing director of an important aircraft manufacturer in Britain in the 1930s. This paper looks at his role and the attitudes he had toward labour force management, while working as the managing director of Airspeed Limited. In this role his actions and attitudes to work relations were influenced greatly by the market, labour force composition, and technological aspects of the industry. These in turn influenced the nature of the way he presented work relations in his literature.

In this study, an adaptive step size control algorithm incorporated in the continuation method (CM) is developed and combined with the filtered impulse function method based on aerostructural solve...

A combination of type A (high flow model) or B (low flow model) shrouded probe and appropriate isokinetic air-sampler (IAS) was tested in a wind tunnel that was optimized for high air speed testing...

Concentrating on the issue that the existence of wind has an effect on the attitude estimation of unmanned aerial vehicle (UAV) and thereafter degrades the controllability of the UAV, based on the extended Kalman filter (EKF), an approach of UAV attitude estimation is proposed in the presence of wind interference. Firstly, attitude quaternion and drift bias of gyroscope are selected to construct the state vector, and the state equation is established based on the kinematics model of gyroscope. After that, observation equation can be obtained via using the measurement of accelerometer, magnetometer, and airspeed tube. In what follows, the EKF update equation is exploited to determine the UAV attitude. As compared to the traditional EKF and unscented Kalman filter, experimental results show that the proposed algorithm can depress the divergence of attitude angle obviously, upgrade the attitude measurement accuracy considerably, and lower the attitude angle error significantly.

Small UAVs are susceptible to the external disturbance, especially the wind field disturbance in the atmosphere environment. As a result, UAV’s states including attitude, speed, and position are usually unable to track the desired control commands. In this paper, different types of wind fields which easily affect the UAV are summarized; furthermore, the mechanism of their wind fields affecting the UAV is first strictly analyzed. Next, a novel “reject external disturbance” flight mode for UAV is put forward to offset the trajectory deviation caused by side wind, which makes use of the wind speed information obtained by airspeed and ground speed of UAV. In order to implement the “reject external disturbance” flight mode, the Lyapunov stability theory-based variable model reference adaptive control (VMRAC) system is proposed, and it could also deal with the adverse effects of wind shear and turbulence on UAV flight. Finally, simulation results show that the proposed strategy can significantly improve the trajectory following quality of the UAV under wind disturbance.

Air traffic flow becomes denser and more complex within terminal manoeuvering areas (TMAs) due to rapid growth rates in demand. Effective TMA arrival management plays a key role in the improvement of airspace capacity, flight efficiency and air traffic controller performance. This study proposes a mixed integer linear programming model for aircraft landing problems with area navigation (RNAV) route structure using three conflict resolution and sequencing techniques together: flexible route allocation, airspeed reduction and vector manoeuver. A two-step mixed integer linear programming model was developed that minimises total conflict resolution time and then total airborne delay using lexicographic goal programming. Experimental results demonstrate that the model can obtain conflict-free and time optimal aircraft trajectories for RNAV route structures.

This study investigates the thermal comfort, airspeed and temperature distribution, air change effectiveness and importance of the boundary conditions on the selection and performance of Active Chi...

Electronic geofencing is proposed as a means to manage small unmanned aircraft systems in distinct airspace boundaries. A geofence is defined by a minimum and maximum altitude and a polygonal horiz...

The article proposes a control method for autonomous unmanned aerial vehicles (UAVs) group of a fixed-wing type intended to both implement and support flight information with predetermined relative distances between the vehicles. The suggested approach provides any selected geometric formation shape construction and further preservation when UAVs enter a straight-line trajectory described by a given course with arbitrary initial positions of UAVs in the horizontal plane. The proposed method feature is "autopilot—UAV" system’s nonlinear structure consideration, manifesting itself in both the autopilot input commands restrictions existence as well as nonholonomic UAV dynamics. In addition, there is an unlimited multi-UAV system scalability available due to decentralization. We take into account the need to maintain a minimum flight speed of not less than the stall speed and the final speed of the formation equal to the cruising speed of this type of UAV. The nonlinear group control laws synthesized using Lyapunov’s direct method are based on the decentralized consensus interaction topology, initially developed for linear agents, which implies each vehicle to interact with its neighboring vehicles only. Global asymptotic stability for the current control laws has been proved. As a result, proposed control laws determine a non-uniform path-following vector field for each vehicle in the whole UAV group flight space (currently two-dimensional space). The suggested field vector norm at a certain space point is the airspeed command for the vehicle at that point while the vector direction is the course angle command. The proposed approach effectiveness has been successfully tested in the MATLAB/Simulink while using realistic nonlinear six degree-of-freedom (DOF) 12-states fixed-wing UAV models. High fidelity simulation results confirm the suggested approach effectiveness.

The wind field has a great influence on the control stability of Tilt-rotor unmanned aerial vehicle (UAV), especially during the take-off and landing phase. The airspeed of UAV is so small during these phases that it cannot generate stable aerodynamic forces, which will significantly reduce the wind robustness of Tilt-rotor UAV. In this article, the disturbance of wind field is analyzed from two perspectives: the wind field acting on the UAV fuselage, which is regarded as external interference, and the wind acting on the propeller, which is considered as modeling error. After analyzing the interference mechanism of wind field, a generalized extended state observer (GESO) and a $H\infty $ robust control method with mixed sensitivity are proposed, which could empower the Tilt-rotor UAV with good interference suppression ability as well as better performance tracking ability. Finally, the laboratory simulation and flight experiment are studied. The results validate the theory and prove that the proposed method could resist the interference of wind field and shows excellent control effect.

The conversion relationship between power spectral density (PSD) and international roughness index (IRI) was studied based on the filtering white noise method with variable sampling frequency using a quarter vehicle model. Six-degree-of-freedom dynamic equations of the whole aircraft taxiing were obtained considering the lift, upstream and downward bump, roll and pitch motion of the airframe. And then the dynamic load factors of the aircraft wheels under different pavement roughness and various airspeeds were solved by SIMULINK toolbox. The results shown that the mean dynamic load is independent of the pavement roughness, whose values are approximately equal to the load when the aircraft glided on the smooth pavement. The worse the pavement roughness, the greater the maximum dynamic load factor. There are approximately linear relationships between IRI and the maximum dynamic load. When the aircraft glides at low airspeed, the dynamic load increases as the increasing of airspeed. Then the maximum dynamic load factor decreases with the increase of running velocity. Moreover, the formulas for calculating the wheel dynamic load factor under the coupling action of pavement roughness and airspeed were proposed, which could be used to calculated the distribution of the dynamic load in longitudinal direction of the runway and determine the dynamic load values in airport pavement design.

This article presents the design and evaluation of a robust C⁎ control law through Hardware-In-the-Loop Simulation (HILS) of JAXA’s research aircraft called Multi-Purpose Aviation Laboratory (MuPAL-α). The C⁎ control law, which is a widely used flight control architecture in aviation industries, is designed using structured H∞ synthesis. This design method provides robustness of the controller for flight condition changes and uncertainties associated with the dynamics of MuPAL-α. HILS tests allow on-ground evaluation of controllers using actual actuators. The HILS results show that the designed controller adequately tracks pilot commands in the presence of airspeed variation, uncertainties in the modeling of the onboard actuators, and wind gust.

Wind disturbance presents a formidable challenge to the flight performance of multi-rotor small unmanned aerial vehicles (sUAVs). This paper presents a comprehensive review of techniques for measuring wind speed and airspeed for multi-rotor sUAVs. Three categories of sensing techniques are reviewed: flow sensors, anemometers, and tilt-angle based approaches. We also review techniques for generating wind disturbances in simulation. Wind simulation techniques that use power spectral density (PSD) functions, computational fluid dynamics (CFD), and probabilistic models are examined. Finally, we provide an open-source Python implementation of the Dryden wind turbulence model and embedded code to interface with an ultrasonic anemometer.

Highlights The AIXR nozzle and modified vegetable oil reduce drift potential. Downwind spray deposition increases non-linearly as airspeed increases. Nozzle selection is more important than adjuvant to mitigate spray drift. Abstract. Spray drift is a critical concern for pesticide applications and the largest focus for its reduction has been placed on increasing droplet size. The objectives of this research were to evaluate the influence of nozzle type, adjuvant, and airspeed on the droplet spectrum and spray drift deposits from applications of glyphosate plus 2,4-D in a wind tunnel. Two studies were conducted using three 11002 nozzles types (XR, DG, and AIXR) individually attached to a one-tip boom. The working pressure was 207 kPa. The first study evaluated drift from the potassium salt of glyphosate (1260 g ae ha-1) plus 2,4-D amine (450 g ae ha-1) tank-mixed with four adjuvants (individually) sprayed at 2.2 m s-1 airspeed. A glyphosate plus 2,4-D solution with no tank-mixed adjuvants was also evaluated. The second study evaluated drift from glyphosate plus 2,4-D applications in four airspeeds (0.9, 2.2, 3.6, and 4.9 m s-1). Drift potential was determined using 2 mm monofilament line collectors and a 1,3,6,8-pyrenetetrasulfonic acid tetra sodium salt (PTSA) fluorescent tracer added to solutions, quantified by fluorometry. Nozzles and adjuvants influenced droplet size distribution of glyphosate plus 2,4-D solutions. Among the nozzles, the AIXR produced the coarsest droplets and the lowest tracer deposits (12 ηg cm-2) at 12 m downwind regardless of solution type. When nozzles were pooled, the modified vegetable oil (MVO) reduced the spray deposition by 36% at 12 m compared to the solution without adjuvant. At 4.9 m s-1 airspeed, tracer deposit at 12 m downwind was 2-fold lower when applications were made through low-drift nozzles (DG and AIXR) compared to the XR nozzle. Results suggest that drift-reducing adjuvants tested in this study may not reduce drift and nozzle selection should be considered as a more important factor than adjuvants in order to mitigate spray drift.

To cope with the problem of global warming and improve the performance of electric vehicles, the power source of electric vehicles is researched. First, the CFD simulation analysis method is utilized to analyze the heat dissipation effect under the changes of the air intake speed, the number of fins, and the thickness of the fins between lithium batteries. Then, the orthogonal experiment is utilized to select the optimal solution between the lithium batteries. The simulation results show that the heat dissipation effect is optimal under the conditions that the inlet air speed is 8 m/s, the number of fins is seven, and the thickness of fins is 2.5 mm. Then, the orthogonal experiment determines the optimal heat dissipation scheme of the lithium battery pack the air inlet speed is 8 m/s, the number of fins is six, and the thickness of the fins is 2 mm. This optimal scheme can effectively improve the heat dissipation performance of lithium batteries, enhance the performance of electric vehicles, and reduce CO2 emissions.

The paper addresses the problem of calculating energy optimal trajectory for a novel class of hybrid UAV equipped with hydrogen fuel cell and solar photovoltaic energy production technologies. The objective of the design is to minimize the energy used for propulsion by optimally utilizing the finite energy stored in the onboard hydrogen fuel cell and routing the aircraft through the time-varying energy fields of solar irradiance and wind. The optimal guidance task is formulated as a two-point boundary value problem with an objective of finding the minimum energy route and the associated controls. The task is solved by applying Pontryagin minimum principle to the resulting 2D kinematics of a UAV along with its aerodynamics, energy management, and propulsion models. The paper derives the necessary conditions and synthesizes the optimal control laws of the bank angle and the airspeed which depend on the time and position derivatives of the wind, and the total angle of incidence toward the sun. The developed method is used to solve a task of path planning of a long endurance flight of a hybrid UAV over multiple 1000 nmi.

The paper presents an improved formula for optimal navigation with respect to time which can be applied to the practical methods and numerical techniques for computing minimum-time paths and routing in arbitary winds, i.e. strong, critical, weak including their combinations, considered on arbitrary modelling surface, thought of as a Riemannian manifold of dimension two. It admits space and time dependence of both, a perturbing wind and a self-speed (airspeed) of a ship. The generalized formula stands for the refinement of analogous optimality conditions worked out recently for spherical cases and so, the improvement of the computational aspects of the corresponding algorithms. In particular, the findings can lead to extension of previous models to ellipsoidal with a two-state problem and two controls. The results can be used for air and marine applications which refer to the Zermelo navigation problem. Although the main interest is dedicated to least time solutions, our objective is also to point out and compare the second type of optimal trajectories, i.e. time-maximal in strong perturbation, where speed of a wind (a water current or a stream) is greater than maximum speed of a ship (an aerial vehicle) relative to a flowing water (air). We also obtain the classification results involving time-minimal and time-maximal paths, types of winds and optimal controls. For the purposes of applied modelling an improved optimality condition in the spherical coordinates for time-optimal navigation on a rotational ellipsoid is worked out in the presented example.

A decrease in the efficiency of the tower cooling tower of the TPP was found, especially in the summer. It has been proposed that one of the reasons for the decrease in productivity may be uneven distribution of flows. Experimental studies of the density distribution of irrigation water and air flow of a tower cooling tower have been carried out. The actual operating characteristics of the cooling device are obtained taking into account the uneven flow. Due to the influence of internal and external factors on the performance of the full- scale tower, it was decided to check the performance at its laboratory installation. An experimental analysis of the distribution of irrigation density and air velocity was performed on a laboratory model of a cooling tower. The experimental characteristics of the full-scale tower cooling tower in a laboratory installation were confirmed: the dependence of air speed, temperature drop of water and cooling power on the distribution of irrigation density. Taking into account the uneven flow of water and air is an important task in the design and operation of tower towers. The problem of rational distribution of irrigation density and air flow in a tower cooling tower is formulated.

This paper presents a numerical and experimental wind tunnel study of aeroelastic shape sensing using fiber-optic sensors. Strain measurements via both discrete and distributed dynamic fiber-optic ...

This article describes a flight simulator study to validate a new command control system for longitudinal load factor $n_x$ . The system is called nxControl and actuates thrust, speedbrakes, and wheel brakes that directly influence the total energy state of the aircraft. It aims at manually flying with higher precision and lower workload. After a brief overview of the functionality of nxControl and its cockpit interfaces, the key results of earlier proof-of-concept simulator studies are summarized. The focus lies on the comprehensive flight simulator study with 24 airline pilots to conclusively evaluate the complete system. The task was a highly demanding approach trajectory containing segmented-continuous-descent in gusty wind conditions, touch-down, deceleration, and taxi as well as engine failure at low altitude. With nxControl, the pilots achieved higher precision in airspeed and energy control with lower workload compared to conventional manual thrust control. In addition, nxControl achieved safety benefits in case of an engine failure.

The development of various types of plant factories is central to improving agriculture. In one form, it is expanding from the existing commercial plant factories to home cultivation systems or cultivators. The plant cultivation system grafted into the living space for people produces differences in the growth of the plant depending on the lifestyle (cooling and heating, residence time, number of residents, etc.) of the resident. In this study, identical home cultivation systems that automatically adjust environmental conditions (temperature, photoperiod, light, and nutrient solution supply) other than the carbon dioxide level were set in an office and warehouse. The study confirmed how plant growth can differ depending on the amount of carbon dioxide generated by humans occupying the space. In addition, it was confirmed whether the growth of plants can be further promoted depending on the external air exchange speed by a ventilation fan even if the indoor carbon dioxide concentration is the same. Due to the nature of the cultivation system that controls the temperature, the type and speed of the fan were set to minimize heat loss in the cultivator. The airspeed from ventilation fans attached to the indoor cultivation systems of an office and warehouse was adjusted to one of three levels (0.7, 1.0, or 1.3 m·s−1). In this study with two species, Ssamchoo and Romaine, it was confirmed that the office space was significantly advantageous for the growth of Ssamchoo, especially in terms of the fresh weight, root activity, and chlorophyll content. Romaine also had a significantly higher fresh weight when grown in the office. Shoot length, leaf length, and leaf width were longer, and there were more leaves. When comparing the relative yield based on an airspeed of 1.0 m·s−1, the yield increased up to 156.9% more in the office than in the warehouse. The fan airspeed had an important influence on Ssamchoo. The higher the fan airspeed, the greater the yield, root activity, and chlorophyll. However, fan airspeed had no consistent effect on the growth tendencies of Romaine. In conclusion, carbon dioxide produced by humans occupying the space is a significant source of carbon dioxide for plants grown in the home cultivation system, although both the speed of the ventilation fan that can promote growth without heat loss and delayed growth caused by the photorespiration in a carbon dioxide-limited situation require additional experiments.

Natural ventilation has been used widely in buildings to deliver a healthy and comfortable indoor environment for occupants. It also reduces the consumption of energy in the built environment and dilutes the concentration of carbon dioxide. Various methods and techniques have been used to evaluate and predict indoor airspeed and patterns in buildings. However, few studies have been implemented to investigate the relevant methods and tools for the evaluation of ventilation performance in indoor and outdoor spaces. The current study aims to review available methods, identifying reliable ones to apply in future research. This study investigates scientific databases and compares the advantages and drawbacks of methods including analytical models, empirical models, zonal models, and CFD models. The findings indicated the computational fluid dynamics (CFD) model is the most relevant method because of cost-effectiveness, informative technique, and proficiency to predict air velocity patterns and ratios in buildings. Finally, widely used CFD codes and tools are compared considering previous studies. It is concluded the application of codes for research is subject to the complexity and characteristics of a studied model, the area and field of study, the desired turbulence model, and the user interface.

This contribution presents the design of an Auto-GCAS algorithm for fixed-wing General Aviation aircraft. The design is implemented for a Diamond Aircraft DA-42NG Twin Star twin-engine piston aircraft along with its integration in a simulation environment. The algorithm has been adapted to account for the technical and operational differences between classes of aircraft. The overall functional architecture comprising trajectory prediction, scan area definition, terrain database query, activation/deactivation logic, and an inner loop autopilot is shared with previous designs. The avoidance maneuvers are re-designed to ensure maximum climb performance by trading airspeed for altitude. The freely available ASTER Global Digital Elevation Model is used as the terrain database. The integration in a Flight Training Device allows for both automated and manual piloted testing and verification of the algorithm.

Atmospheric conditions are known to affect flight propensity, behaviour during flight, and migration route in birds. Yet, the effects of fog have only been rarely studied, although they could disrupt orientation and hamper the accomplishment of the journey. Soaring migrants modulate their flight speed and direction in relation to the wind vector to optimize the cost of transport. Fog could limit the visibility of migrating birds such that they might not be able to detect landmarks that guide them during their journey. Consequently, landmark-based orientation, as well as adjustments of flight speed and direction in relation to wind conditions, could be jeopardized when flying in fog. Using a radar system that operated in a migration bottleneck (Strait of Messina, Italy), we studied the behaviour of soaring birds under variable wind and fog conditions over two consecutive springs (2016 and 2017), discovering that migrating birds exhibited a wider scatter of flight directions and responded differently to wind conditions under fog conditions. Birds flying through fog deviated more from the mean migration direction and increased their speed with increasing crosswinds. In addition, airspeed and groundspeed increased in the direction of the crosswind, causing a lateral drift of the individuals. Furthermore, the response to tailwind was opposite to that predicted by optimal migration theory. Our findings represent the first quantitative empirical evidence of flight behaviour changes when birds migrate through fog and explain why low visibility conditions could risk their migration journey.

Ice accretion or icing is a well-known phenomenon that entails a risk for the correct functioning of an aircraft. One of the areas more vulnerable to icing is the air data measuring system. This paper studies the icing protection offered by a heating system installed inside a multi-hole probe. The problem is initially solved analytically, creating a tool that can be used in order to predict the heating performance depending on the flying conditions. Later, the performance of the real system is investigated with a heated five-hole probe prototype in a wind tunnel experiment. The measured results are compared with the predictions made by the analytical model. Last, the icing protection provided by the system is estimated with respect to flying altitude and speed. As a result, a prediction tool that can be used in order to make quick icing risk predictions for straight cylindrical probes is delivered. Furthermore, the study provides some understanding about how parameters like altitude and air speed affect the occurrence of ice accretion.

The analyses of the traditional and developed means of measuring of parameters of airspeed vector, implementing aerometric and vane, vortex or ion-mark methods of parameters of incoming airflow are performed. The article discloses the theoretical foundations of building of the original electronic sensor of direction angle and module of airspeed vector of unmanned aircraft plane with ultrasonic instrumentation channels. The functional scheme of the electronic sensor is presented, the distinctive feature of which is using of two pairs of combined transmitters and receivers of ultrasonic vibrations propagating along and against the direction of incoming flow. Informative signals of ultrasonic instrumentation channels are registered by the measuring circuit including two instrumentation channels. The analytical models are obtained for forming and processing of informative signals, determining the parameters of airspeed vector of unmanned aircraft plane by frequency, pulse time and phase informative signals of ultrasonic instrumentation channels is presented, which are processing with built-in computer. The expediency of using frequency informative signals, excluding methodological errors of measuring airspeed, has been substantiated. The possibility of measuring the direction angle of airspeed vector in range ±180° without increasing the number of ultrasonic instrumentation channels is revealed. The competitive advantages and prospects of using the electronic sensor of airspeed vector parameters on small unmanned aircraft plane are considered. The obtained results are the theoretical basis for the development, error analysis and ensuring the accuracy of the electronic sensor of parameters of airspeed vector with ultrasonic instrumentation channels for small-sized unmanned aircraft planes of various classes and purposes.

Natural ventilation (NV) represents the most energy-efficient way to operate buildings and, in an attempt to reduce the built environment's global carbon footprint, represents a resource in which usage has to be maximized. This study demonstrates how a combination of an IoT environmental sensing network implemented locally outdoors and indoors can help to determine the NV potential and actual utilization throughout the year with the consideration of outdoor climate variance, air pollution levels, and window open/closed status. An NV potential index was developed by analyzing indoor and outdoor PM2.5, and outdoor air temperature and airspeed throughout the year at different spatial (from room-scale to building level and local weather stations) and temporal (instantaneous, season, and annual) scales. By applying the NV potential index to the case study building, we found that 61.2% of the time throughout the period of the study, conditions were favorable for NV usage. However, actual NV usage was only 35 % of the available potential. This result suggests that actual window use is the factor that restricts the most utilization of the available NV potential. Occupant behavior regarding keeping windows open or closed needs consideration during the planning and designing of the NV strategy. This result demonstrated that with the further development and adaptation of IoT sensing, we need to develop ways to communicate information to the occupants and use more available natural potential while improving the environment they use. The actual window usage behavior (open/closed status) was significantly affected by outdoor climate conditions and air pollution levels. Occupants kept windows open only while the outdoor temperature is neutral to warm and the air pollution level was low.

This study seeks to evaluate thermal comfort in naturally ventilated classrooms to draw sustainable solutions that reduce the dramatic energy consumed in mechanically ventilated spaces. Passive ventilation scenarios are generated using alternations of openings on the windward and leeward sides to evaluate their effects on thermal comfort. Twenty-eight experiments were carried in Bahrain during winter inside an exposed classroom, the experiments were grouped into five scenarios namely: “single-inlet single-outlet” SISO, “single-inlet double-outlet” SIDO, “double-inlet single-outlet” DISO, “double-inlet double-outlet” DIDO and “single-side ventilation” SSV. The findings indicate that single-side ventilation did not offer comfort except at high airspeed, while comfort is attained by using cross-ventilation at ambient temperature between 21.8–26.8 °C. The temperature difference between monitored locations and the inlet is inversely proportional to the number of air changes per hour. The DISO scenario accomplishes the lowest temperature difference. Using cross-ventilation instead of single-side ventilation reduces the temperature differences between 0.5–2.5 °C and increases airspeed up to three folds. According to the measured findings, the DISO cross-ventilation scenario is a valid sustainable solution adaptable to climatic variation locally and beyond with zero-energy consumption and zero emissions.

Thermal comfort is a variable that makes it possible to measure a person’s sensation in a given environment. This variable depends on several factors: ambient temperature, relative humidity, air speed, the clothes that the person wears, and the physical activity that they are doing, among others. Given the number of measurements to be carried out, we must already speak of a sensor node for the development of a sensor that allows the measurement of variables to estimate thermal comfort. This work presents the development and calibration of a low-cost sensor node that allows the estimation of thermal comfort through the Fanger method, for which the PMV (Predicted Mean Vote) and PPD (Predicted Percentage Dissatisfied) are estimated. The development of low-cost sensors for estimating thermal comfort will allow the development of platforms to manage energy use in buildings efficiently. Finally, the experimental results of the sensor node prototype are presented and compared with standard instruments in the laboratory stage, showing the certainty of the prototype.

Oil-air lubrication has been extensively used in mechanical equipment fields. The study aimed to evaluate the tribological behavior of linear contact sliding friction pairs under oil-air lubrication. An oil-air lubrication equipment was developed, and linear contact sliding friction under oil-air lubrication test was carried out on a reciprocating wear test device. Microscopic feature and composition distribution of the wear scars were conducted using scanning electron microscopy, optical white-light interferometer, energy-dispersive X-ray spectroscopy and Raman spectrometer. The influence rule of oil supply, oil pressure, airspeed, air pressure and oil temperature on the tribological behavior of linear contact sliding friction pairs was obtained. Experimental results demonstrate that the friction coefficient curves of different parameters are composed of four stages, namely, the initial stage, the recede stage, the ascent stage and the stable stage. The relationship between oil-air lubrication test parameters and wear was discussed. The wear mechanisms of linear contact sliding friction pairs under oil-air lubrication are delamination wear, abrasive wear and oxidation wear.

An energy reduction strategy for a fixed-wing drone with classic configuration is presented in this paper. The strategy is developed using the longitudinal non-linear motion equations of the aircraft, considering the stall effects in the determination of lift and drag forces. Our strategy imposes the aircraft to track a special trajectory allowing the vehicle to perform a curve in ascend, acting against the gravity force. As a consequence of this tracking, the angle of attack of the vehicle is increased arriving to critical values that need to be compensated for avoiding the crash of the vehicle. Therefore, a strategy to avoid the stall stage and recovering the flight stability in the vehicle is proposed. The strategy is evaluated in simulations for validating the performance of the whole system.

The main objective of this paper is to describe a tool for the aircraft autopilot deployment only based on a flight database. Flight simulators such as X-Plane turn out to be powerful and efficient tools for creating such database and controller experimentation. The paper outlines the development of a co-simulation framework between Matlab and X-Plane using the User Datagram Protocol (UDP). The flight data collected during a first step are then used for the training of neural controllers. The approach is based on the neural network imitation ability to learn the piloting skills implicitly stored in the dataset. Also, in order to include fault-tolerant control, a Neural Multiple Model Adaptive Control (NMMAC) based on previously learned networks is implemented. This architecture consists of a bank of local controllers and a switching logic using a bank of estimators. As an illustration of the proposed platform, it is assumed that the airspeed is unmeasured for the flight director. A neural guidance autopilot based NMMAC is therefore performed on different airspeed values. Experiments show that the designed neural autopilot can successfully track both heading and altitude reference signals, while the method is not restricted to this scope.

A novel Data-driven State Awareness (DSA) framework is introduced for the next generation of intelligent “fly-by-feel” aerospace vehicles. The proposed framework is based on two entities: (i) bio-inspired networks of micro-sensors that can provide real-time information on the dynamic aeroelastic response of the structure and (ii) a stochastic “global” identification approach for representing the system dynamics under varying flight states and uncertainty. The evaluation and assessment of the proposed DSA framework is based on a prototype bio-inspired self-sensing intelligent composite wing subjected to a series of wind tunnel experiments under multiple flight states. A total of 148 micro-sensors, including piezoelectric, strain, and temperature sensors, are embedded in the layup of the composite wing in order to provide the sensing capabilities. A novel data-driven stochastic “global” identification approach based on functionally pooled time series models and statistical parameter estimation techniques is employed in order to accurately interpret the sensing data and extract information on the wing aeroelastic behavior and dynamics. The methods’s cornerstone lies in the new class of Vector-dependent Functionally Pooled (VFP) models which allow for the analytical inclusion of both airspeed and angle of attack (AoA) in the model parameters and, hence, system dynamics. Special emphasis is given to the wind tunnel experimental assessment under various flight states, each defined by a distinct pair of airspeed and AoA. The obtained results demonstrate the high achievable accuracy and effectiveness of the proposed state-awareness framework, thus opening new perspectives for enabling the next generation of “fly-by-feel” aerospace vehicles.

The design of adaptive control for an aeroelastic wing using structured $H_{\infty}$ synthesis is presented in this paper. The algorithm uses a polynomial interpolation of controller parameters for a wide airspeed range. The structure of control law is fixed, with its parameters determined for a given airspeed range. We demonstrate the possibilities of such a controller for active flutter suppression on the linear parameter-varying (LPV) servoaeroelastic wing model with two ailerons.

High-Altitude Ice Crystals (HAIC) constitute a hazard to commercial aircraft flying near deep convective weather due to jet-engine power loss and air data probes malfunction. HAIC can stick to warm metal surfaces in jet-engines and cause engine surge, stall, flameout and rollback, power loss, as well as engine compressor damage due to ice shedding. Along with these events, disruption to aircraft systems are noted when HAIC are ingested into air data probes (Pitot tube and/or Total Air Temperature -TAT- sensor), causing erroneous measurements of temperature and air speed. Particularly, the TAT probe incorrectly reporting zero degrees Celsius or in error is known to be evidence of ice crystals in the atmosphere surrounding the aircraft. These TAT anomalies are due to the accumulation of ice crystals in the TAT sensor, producing a zero degrees Celsius reading, generating failures in airspeed indicators and acting as potential incident/accident precursors. In this paper, TAT events from pilot reports and Flight Data Monitoring (FDM) are analyzed. TAT FDM data analysis covers two types of engines, which are used on short, medium and long-range routes. The study includes eight aircraft fleet types. Based on these analyses, we present a sensor-failure-tolerant heuristic that generates a reliability indicator, founded on the differences between the TAT and the engine's inlet temperature sensors. It aims to provide early warnings to pilots regarding HAIC events and prevent potential data errors and system failures.

The engine failure, according to the flight safety inspection of the Federal Air Transport Agency, caused 4 of 6 aviation accidents in 2017, including 2 air disasters. In general, from 2001 to 2017, events related to the engine failure became the second most frequent cause of aviation accidents (13% of aviation accidents and 12% of air disasters). The worst consequences are associated with the engine failure at the most difficult and crucial stage of the flight landing. For example, it was the engine failure on the final approach that caused the crash of the L-410UVP-E20 RA-67047 aircraft near the Nelkan airfield on November 15, 2017. The article discusses a limiting situation in some sense – the landing of an aircraft with all failed engines under the wind conditions. The authors have proposed for this situation a methodology of calculating the landing approach of an aircraft under the wind conditions in case of failure of all engines of its power plant to an aerodrome equipped with an outer marker. The key features of such methodology are, firstly, the absence of necessity to link the path to the landmarks in the landing aerodrome area, and, secondly, the simplicity of the synthesis and the implementation of the aircraft control based on the proposed methodology during landing in both manual and director or automatic modes. To calculate the approach using the proposed methodology, the crew only needs to know the following values: the minimum drag airspeed on final approach, the height of the flight over an outer marker before landing and spiral approach leg. The content of the methodology in the article is illustrated by the results of the approach calculation when all of the main engines of the Russian short-medium-range MS-21 aircraft fail under the wind conditions.

Purpose The purpose of this study is to analyze the effect of using a ceiling fan with central heating system in the winter on thermal comfort and heat transfer rate in a three-dimensional numerically. Design/methodology/approach The geometry had certain dimensions, and an occupant was modeled to be in the room. In models which were used, the flow was turbulent, and turbulence models were used for simulating turbulence. Between all the models, k-ε model had best matching. Findings Results show that using the ceiling fan during the winter had an efficient and considerable effect on improving the thermal comfort and energy saving inside buildings. By the use of ceiling fan, the effective room temperature has increased by 2.5°C. Furthermore, results show that by using ceiling fan in the winter, the predicted mean vote and the predicted percentage dissatisfied indexes improved. At the end, the case Room 11-0.05-15 with temperature of 87°C for radiator and normal fan velocity of o.25m/s were the optimal model that caused the complete thermal comfort and reduced energy consumption up to 28 per cent. Originality/value In the present study, the effects of using the ceiling fans on human comfort condition and heat transfer field during the winter (heating system) are studied. Following are the goals for all models: getting the appropriate temperature for radiator so that thermal comfort condition can be applied at the height of 75 cm of the room, velocity for fan so that air speed can be 0.25m/s at the height of 2 m or lower of the room and position to place the fan.

Mode tracking is one of the critical problems in aeroelastic stability analysis. A novel mode tracking method is discussed in this paper using both left and right eigenvectors of aeroelastic system...

Solar-powered aircraft promise significantly increased flight endurance over conventional aircraft. Although this enables large-scale inspection missions, their fragility necessitates that adverse ...

The development of a multiple model-based identification algorithm is addressed in this paper for nonlinear modeling of a conventional aircraft in the entire flight envelope. The dynamic model of an aircraft varies significantly depending on changes in the flight condition of the air vehicle including the altitude and the equivalent air speed. Therefore, the conventional identification approaches for generating a single nonlinear model with time-invariant parameters cannot be used in the entire flight envelope of an aircraft. Accordingly, a multiple model-based approach using nonlinear autoregressive exogenous neural networks is introduced in this paper as a powerful tool in identifying complex nonlinear dynamic systems. Different methods of validity function determination are introduced in order to aggregate the separate local models into a single model. The obtained results show that the proposed approach using the extreme learning machine-based validity function determination method has a significant capability to predict the aircraft outputs in various flight conditions. Further, the proposed identification scheme can be used effectively as a precise multistep ahead predictor of nonlinear multivariable systems outputs.

Blower is a device that is often used because it is able to increase or add gas that will be flowed in a particular room as well as suctioning or vacuuming gas. At present the blower is comprehensive, starting from laboratories, office buildings and industries which are widely used as a component in the production process. There are several classifications of blowers, namely centrifugal blowers which include radial blade, forward curve blade and backward curve blade. Then, the positive displacement blower includes the vane blower. This study aims to determine the performance of centrifugal blowers when adding the number of blades to the centrifugal impeller blower. There are 3 impellers that are used with variations in the number of different blades, 6, 8, and 10 in testing to find the performance of centrifugal blowers. Air speed is measured using an anemometer while pressure drop measured using a manometer U pipe containing oil fluid. The number of blade impeller affect the increasing performance of blower.

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.

Thermal adaptation can play a significant role in defining thermal comfort levels for evaporatively cooled office buildings commonly found in India. However, there are no dedicated studies to record the occupant perception and indoor thermal comfort in these buildings. The contribution of adaptive thermal comfort theory on occupant perception remains unclear for accurate design and operation of evaporatively cooled office buildings in India. Therefore, a multi-year field study of thermal comfort was conducted in ten office buildings operated under evaporative cooling systems in the composite climate of Jaipur, India. Transverse type questionnaire following Class II measurement protocols was carried out for recording office occupant's sensation and preferences for different indoor variables using ASHRAE 55 seven point and five-point scales, respectively. A total of 1554 datasets were collected spread over a total period of eighteen months, covering the entire summer season which includes very hot and dry days as well as few rainy days. Comfort temperature calculated using the Griffiths method was found 28.8 °C (SD=±1.9 °C). Results from the field study showed acceptable indoor humidity and airspeed range of 35–85% and 0.75–1.5 m/s for office subjects. Furthermore, 80% and 90% acceptability limits based on operative temperature and SET* were determined for present field surveys and results were compared with the existing adaptive models in National Building Code of India for different building types. This work is the first step towards the formation of an adaptive comfort model for evaporatively cooled buildings in the composite climate of India.

Aviation is often seen as an innovative sector eager to seek technological solutions. It is often assumed that aircraft cockpits have panels with electronic displays and many buttons, some labeled "auto." While this might be the case for commercial aviation (Figure 1), the vast majority of noncommercial civil aircraft cockpits look nothing like these modern cockpits. Non-commercial civil aircraft, known as general aviation (GA), typically have cockpits that mainly consist of analog instruments that show the heading of the aircraft, the altitude, and the air speed (Figure 2). While flying, the pilots make calculations using a compass and an aviation calculator. Due to the slow entry rate of new, glass-cockpit aircraft [1], the composition of the GA aircraft fleet is not going to change any time soon.