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This work addresses the critical need for documentation and validation of structural flight loads for Medium-Altitude Long-Endurance (MALE) Unmanned Aerial Systems (UAS). Despite the increasing prevalence of these aircraft, the industrial and research landscape still exhibits a significant data gap regarding loads under extreme operating conditions, particularly for unconventional geometric configurations. This study presents a rigorous and comprehensive load analysis for the certification of a fixed-wing MALE UAS, which is distinguished by its unique V-Tail configuration, characteristic of platforms such as the Elbit Hermes series. The entire investigation was conducted in strict adherence to the requirements of the NATO airworthiness standard STANAG 4671, aiming to precisely define the aerodynamic behavior and structural integrity of the airframe under an exhaustive set of critical flight conditions. The implemented methodology relies on the use of high-fidelity Computational Fluid Dynamics (CFD) data, derived from RANS simulations to create a complete aerodynamic database. This advanced approach is crucial for the accurate modeling of forces and moments, especially those generated by the coupled control surfaces, known as the ruddervators of the V-Tail. The results obtained include the precise derivation of the operational envelope, which defines the maximum load factors for both maneuver and atmospheric gust conditions. A detailed analysis of balancing and specific loads on the control surfaces was performed, leading to the definition of structural load distributions essential for subsequent stress analysis. Notably, the analysis identified the Unchecked Pitch-Up maneuver performed at the maximum load factor as the dimensioning design condition, particularly for the empennage structure. This work not only provides fundamental data for demonstrating compliance with applicable airworthiness criteria but also establishes a robust and repeatable methodology for the evaluation of flight loads in structurally complex UAS configurations.

The future of aviation depends on reducing the environmental impact of the aircraft. Unconventional configurations can be the change the industry needs to achieve that goal. Therefore, the development of a tool that allows analyzing these configurations will contribute to their being considered more easily in future designs. This design procedure is based on an aerodynamic model and a weight methodology validated for unconventional tail designs. The load cases selected to size the structure were extracted from the certification regulations in force. In order to validate the methodology, the V-tail configuration was selected as a case study. The fuel savings reached with this tail configurations are around 0.7%, and the reduction in NOx emissions are even greater. Thus, the methodology has been validated and it can be easily adapted to other unconventional tail configurations.

With the advantages of long-range flight and high payload capacity, large fixed-wing UAVs are often used in anti-terrorism missions, disaster surveillance, and emergency supply delivery. In the existing research, there is little research on the 3D model design of the V-tail fixed-wing UAV and 3D flight environment modeling. The study focuses on designing a comprehensive simulation environment using Gazebo and ROS, referencing existing large fixed-wing UAVs, to design a V-tail aircraft, incorporating realistic aircraft dynamics, aerodynamics, and flight controls. Additionally, we present a simulation environment modeling approach tailored for obstacle avoidance in no-fly zones, and have created a 3D flight environment in Gazebo, generating a large-scale terrain map based on the original grayscale heightmap. This terrain map is used to simulate potential mountainous terrain threats that a fixed-wing UAV might encounter during mission execution. We have also introduced wind disturbances and other specific no-fly zones. We integrated the V-tail fixed-wing aircraft model into the 3D flight environment in Gazebo and designed PID controllers to stabilize the aircraft’s flight attitude.

Flutter is a dynamic aeroelastic instability that may cause structural failure and limits flight envelope of an aircraft. A passenger aircraft is required to be free from flutter and other aeroelastic instability phenomena, as stated in the regulations such as FAR 25. 33 / FAR 23.33. This paper presents the flutter analyses of the WISE aircraft using MSC Nastran. The analyses were carried out to the V-tail, one of the component where flutter might occur, by assuming rigid fuselage. Results of each analysis, in the form of velocity-damping and velocity-frequency curves, were evaluated to determine the critical flutter speed and frequency. First the analysis were conducted for sea level operation using KE, PK and PKNL methods which predict respectively the flutter speed of 1036 knot, 1037 knot, and 1037 knot. The three methods also consistently predict that the mode shapes involved in the flutter are the 5 th mode and the 3 rd mode. Then by using the PK-method, the analysis were repeated for air density variation. It is shown that the lower the air density, the higher the flutter speed is. It is concluded that tail flutter does not occur during the operation of the WISE craft with max operating speed of 80 knot.

The V-tail configuration has excellent stealth performance and has been using widely in the aerodynamic shape design of advanced aircraft. Many recent studies have focused on numerical simulation about V-tail configuration flight performance. The relative wind tunnel tests still need to be developed. This challenge is a focused aspect in such research. In the present experimental study, the role of flight control law was investigated in order to keep the test model in the target attitude and height. An effective design method of a full model of the aircraft with twin V-tails is proposed based on CFD evaluation. This model was manufactured based on the design of a two degrees of freedom support system via a Chinese wind tunnel. A longitudinal flight control law was proposed and simulated. Wind tunnel tests were employed to find the effectiveness of the model design and the control law. It is seen from the results that the proposed experimental method via a full model of the aircraft with twin V-tails and a novel longitudinal flight control law is effective. These test results can provide appliable contributions on the development of the support system for wind tunnel experiments. The proposed model design and test methods can be useful for applications in the aeroelastic wind tunnel tests of the full model aircrafts.

A wind tunnel test was conducted to compare the characteristics of low speed stability and control for aircraft with conventional tail and V-tail configurations. Comparison was made in terms of static directional stability at selected test speed of 40 m/s, which corresponds to Reynolds number of 0.1622 x 106 based on the chord. Three types of simplified tail-only model were tested in Universiti Teknologi Malaysia's Low Speed Wind Tunnel (UTM-LST). Results show that the V-tail configuration greatly affects the aerodynamic characteristics in directional stability as the side force and yaw moment tends to vary linearly with yaw angles up to 25 degrees, compared to conventional tail that has linear characteristics up to only 10 degrees yaw

Autonomous unmanned air vehicles (UAVs) are critical to current and future military, civil, and commercial operations. Despite their importance, no previous textbook has accessibly introduced UAVs to students in the engineering, computer, and science disciplines--until now. Small Unmanned Aircraft provides a concise but comprehensive description of the key concepts and technologies underlying the dynamics, control, and guidance of fixed-wing unmanned aircraft, and enables all students with an introductory-level background in controls or robotics to enter this exciting and important area. The authors explore the essential underlying physics and sensors of UAV problems, including low-level autopilot for stability and higher-level autopilot functions of path planning. The textbook leads the student from rigid-body dynamics through aerodynamics, stability augmentation, and state estimation using onboard sensors, to maneuvering through obstacles. To facilitate understanding, the authors have replaced traditional homework assignments with a simulation project using the MATLAB/Simulink environment. Students begin by modeling rigid-body dynamics, then add aerodynamics and sensor models. They develop low-level autopilot code, extended Kalman filters for state estimation, path-following routines, and high-level path-planning algorithms. The final chapter of the book focuses on UAV guidance using machine vision. Designed for advanced undergraduate or graduate students in engineering or the sciences, this book offers a bridge to the aerodynamics and control of UAV flight.

Investigators are trying to determine why a single-engine, private airplane was flying so low in fog Wednesday that it clipped a power line and the tops of trees, crashing near a road about nine miles southeast of Xenia. Thomas E. Saulbeamer , 44, of Sedalia , Mo., was alone in the V-tail Beechcraft Bonanza when it crashed just west of Paintersville-New Jasper Road, then skidded or tumbled across the road and came to a stop on a pond bank.

The textile and fashion industries have forever been at the mercy of rapidly changing styles and fickle customers who want the latest designs while they are still fashionable. The result for these businesses, often forced to forecast sales and deal with suppliers based on volatile demand, is a history of stock shortages, or costly markdowns. But, as the authors disclose in A Stitch in Time, technological advances that began in the 1980s introduced a new concept in retailing—lean retailing. Pioneered by entrepreneurs such as Sam Walton and WAL-MART and made possible by new information technologies for tracking sales data, lean retailing has enabled apparel producers to reorganize the manner in which they related to retail customers, undertook distribution, forecasted and planned production, and managed supplier relations. In an industry that typically suffered from great delays from warehouse to rack, sales data was now captured at the retailer’s checkout through bar coding and immediately transmitted back to distributors, manufacturers, designers, and even to the textile mills that weave the cloth. Armed with up-to-the-minute data about colors, sizes, and geographic sales, everyone in the chain was able to reduce cost, increase efficiency, and keep the customer in style like never before. And today, the broad changes introduced in the apparal industry by lean retailing are rippling through a growing segment of the American economy. A richly detailed and resonant account, A Stitch in Time brilliantly captures both the history and the future of the fashion industry as it offers executives a new paradigm for understanding the challenges of retailing and manufacturing in all segments of our rapidly transforming economy.