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Turbojet engines have been used for many decades in aviation. Although their share in civil aviation is minimal, with the advent of Unmanned Aerial Vehicles (UAV's) there are new applications. Their operation depends on complex aero-thermodynamic laws, and optimum performance is strongly affected by the control system. The authors have previously investigated how the Turbofan Power Ratio (TPR), originally introduced on Rolls-Royce commercial turbofans, can be used in control of single stream turbojet engines. Based on those results, in the present paper the assessment of flight characteristics is introduced, based on mathematical models, which are available of the particular gas turbine type under investigation. Like the corrected rotor speed, the ratio of TPR and actual thrust depends on Mach number, therefore, this function is determined in this paper. The investigations also included a deteriorated model under control of both corrected rotor speed and TPR, which has shown that TPR can partially recover thrust loss thus improving the safety of the power plant. As a conclusion, TPR is worth of utilizing in control systems as it results in more straightforward thrust correlation and reduced performance loss over time. Furthermore, measuring simultaneously with other common engine parameters, the extent of deterioration can be signalized to the crew before it evolves into a catastrophic failure.

There is seldom research considering propeller torque on the flight characteristics of powered parafoil. To address this insufficiency, this paper establishes a multi-body dynamics model of a powered parafoil and introduces a propeller torque model to investigate the mechanism of torque effect on flight characteristics. The analysis results show that the propeller torque has a significant effect on the lateral-directional motion of the powered parafoil, which is equivalent to handling the asymmetric brake lines with up to 10% deflection. The research also shows that propeller torque will cause an additional yaw motion derived from its mounting position and installation angle. Based on the above results, this paper further proposes several strategies to mitigate the influence of propeller torque by adjusting the propeller mounting position and installation angle.

Insect flight can be fast and agile, making it hard to study its detailed aerodynamics. Karásek et al. designed an untethered, flapping-wing robot with impressive agility that can mimic fruitfly maneuvers (see the Perspective by Ruffier). They studied the robot's motion during rapid banked turns, which revealed that passive motion through the turn generated yaw torque coupling. This correcting yaw rotation propelled the robot toward the escape heading needed for effective turning. Science , this issue p. 1089 ; see also p. 1073 An untethered, flapping-wing robot with impressive agility is capable of mimicking maneuvers of the fruitfly. Insects are among the most agile natural flyers. Hypotheses on their flight control cannot always be validated by experiments with animals or tethered robots. To this end, we developed a programmable and agile autonomous free-flying robot controlled through bio-inspired motion changes of its flapping wings. Despite being 55 times the size of a fruit fly, the robot can accurately mimic the rapid escape maneuvers of flies, including a correcting yaw rotation toward the escape heading. Because the robot’s yaw control was turned off, we showed that these yaw rotations result from passive, translation-induced aerodynamic coupling between the yaw torque and the roll and pitch torques produced throughout the maneuver. The robot enables new methods for studying animal flight, and its flight characteristics allow for real-world flight missions.

Flight costs are predicted to vary with environmental conditions, and this should ultimately determine the movement capacity and distributions of large soaring birds. Despite this, little is known about how flight effort varies with environmental parameters. We deployed bio-logging devices on the world’s heaviest soaring bird, the Andean condor (Vultur gryphus), to assess the extent to which these birds can operate without resorting to powered flight. Our records of individual wingbeats in >216 h of flight show that condors can sustain soaring across a wide range of wind and thermal conditions, flapping for only 1% of their flight time. This is among the very lowest estimated movement costs in vertebrates. One bird even flew for >5 h without flapping, covering ∼172 km. Overall, > 75% of flapping flight was associated with takeoffs. Movement between weak thermal updrafts at the start of the day also imposed a metabolic cost, with birds flapping toward the end of glides to reach ephemeral thermal updrafts. Nonetheless, the investment required was still remarkably low, and even in winter conditions with weak thermals, condors are only predicted to flap for ∼2 s per kilometer. Therefore, the overall flight effort in the largest soaring birds appears to be constrained by the requirements for takeoff.

Over hundreds of millions of years of natural selection, hummingbirds have evolved excellent flight characteristics. This ingenious wing structure provides a new inspiration for the design of bionic flapping wings. In this paper, a kind of bionic flexible flapping wing is designed with a hummingbird as the prototype, its parametric aerodynamic characteristics are analyzed, and its feasibility is verified by simulation. Combined with the simulation results, the aerodynamic parameters such as lift, drag, and lift-drag ratio are comprehensively considered, and the optimal parameter combination is 5 m/s-20 Hz. Under this parameter combination, the aerodynamic performance is the best, and the lift-drag ratio is as high as 13.3. This paper can provide a theoretical basis and technical reference for further development of bionic flapping wing MAV design.

Flight speed is positively correlated with body size in animals 1 . However, miniature featherwing beetles can fly at speeds and accelerations of insects three times their size 2 . Here we show that this performance results from a reduced wing mass and a previously unknown type of wing-motion cycle. Our experiment combines three-dimensional reconstructions of morphology and kinematics in one of the smallest insects, the beetle Paratuposa placentis (body length 395 μm). The flapping bristled wings follow a pronounced figure-of-eight loop that consists of subperpendicular up and down strokes followed by claps at stroke reversals above and below the body. The elytra act as inertial brakes that prevent excessive body oscillation. Computational analyses suggest functional decomposition of the wingbeat cycle into two power half strokes, which produce a large upward force, and two down-dragging recovery half strokes. In contrast to heavier membranous wings, the motion of bristled wings of the same size requires little inertial power. Muscle mechanical power requirements thus remain positive throughout the wingbeat cycle, making elastic energy storage obsolete. These adaptations help to explain how extremely small insects have preserved good aerial performance during miniaturization, one of the factors of their evolutionary success. Three-dimensional reconstructions of morphology and flight mechanics of the beetle Paratuposa placentis reveal adaptations that enable extremely small insects to fly at speeds similar to those of much larger insects.

The radome is a key component of a high-speed vehicle, generally located in the front end of a missile or an airplane, and its assembly precision will directly determine the flight performance of the vehicle. The connection between the radome body part and the connecting ring currently has bolts, threaded connection, adhesive connection, welding connection, snap connection, flange connection, etc. In this paper, for the actual production of the traditional assembly of the head cone and connecting ring by manual adjustment, there are problems such as poor bonding accuracy, low degree of automation and inefficiency, so the semi-automated bonding method is chosen. Based on the above problems for the radome overall assembly program design, determine the main positioning structure and measurement technology, according to the main structure to determine the cone mask bonding process and the whole cone mask bonding process; for the design of the positioning technology and measurement technology to clarify the key points of the bonding technology and the difficulties and problems to be solved; for the equipment to meet the requirements of the technical specifications, after the bonding of the measurements, the collection of measurement data to verify that Whether to meet the technical requirements of bonding, test equipment functionality.

High-velocity air–fuel (HVAF) is a combustion process that allows solid-state deposition of metallic particles with minimum oxidation and decomposition. Although HVAF and cold spray are similar in terms of solid-state particle deposition, a slightly higher temperature of HVAF may allow further particle softening and because of it, more particle deformation upon impact. The present study aims to produce dense Ti-6Al-4V coatings by utilizing an inner-diameter (ID) HVAF gun. The ID gun is considered a scaled-down version of the standard HVAF with a narrower jet, beneficial for near-net-shape manufacturing. To explore the potential of the ID gun in the solid-state deposition of Ti-6Al4V, an investigation was made into the effect of spraying parameters (i.e., spraying distance, fuel pressure, feeding rate, traverse speed, and nozzle length) on the characteristics of in-flight particles and the attributes of the as-fabricated coatings such as porosity, phases, and hardness. For studying in-flight particles characteristics, using online diagnostics is challenging due to the exothermic oxidation reaction of fine particles, while larger particles are too cold to be detected from their thermal emission. However, DPV diagnostic system was successfully employed to differentiate the non-emitting solid particles from the burning ones. It was found that increasing air and fuel pressure of the ID-HVAF jet as well as increasing the nozzle length led to an increase in the velocity of the in-flight particles and resulted in improved density and hardness of the as-sprayed samples. However, increasing the spraying distance had a negative effect on the density and hardness of the manufactured coatings.

Obtaining the characteristic parameters of the aircraft platform is the main blocking point that takes a long time in aircraft/engine co-simulation, so a fast co-simulation modeling method is proposed. In this paper, the kriging model based on the improved EOEI sampling function is used to quickly fit the lift-drag characteristics of aircraft. Combined with the lift-drag data verification test of typical high-speed aircraft shape, the flight performance of the aircraft is evaluated. The simulation results show that under the condition that the average relative error of lift-drag characteristics is not more than 5%, only 22 to 24 CFD solutions are needed to complete the construction of lift-drag characteristics for the speed range of Mach 0 to Mach 6, and the angle of attack range of-4° to 8°.

The growing interest in unmanned aerial vehicles (UAVs) from both the scientific and industrial sectors has attracted a wave of new researchers and substantial investments in this expansive field. However, due to the wide range of topics and subdomains within UAV research, newcomers may find themselves overwhelmed by the numerous options available. It is therefore crucial for those involved in UAV research to recognize its interdisciplinary nature and its connections with other disciplines. This paper presents a comprehensive overview of the UAV field, highlighting recent trends and advancements. Drawing on recent literature reviews and surveys, the review begins by classifying UAVs based on their flight characteristics. It then provides an overview of current research trends in UAVs, utilizing data from the Scopus database to quantify the number of scientific documents associated with each research direction and their interconnections. This paper also explores potential areas for further development in UAVs, including communication, artificial intelligence, remote sensing, miniaturization, swarming and cooperative control, and transformability. Additionally, it discusses the development of aircraft control, commonly used control techniques, and appropriate control algorithms in UAV research. Furthermore, this paper addresses the general hardware and software architecture of UAVs, their applications, and the key issues associated with them. It also provides an overview of current open source software and hardware projects in the UAV field. By presenting a comprehensive view of the UAV field, this paper aims to enhance our understanding of this rapidly evolving and highly interdisciplinary area of research.