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Exhaust System
Published in Ahmed F. El-Sayed, Aircraft Propulsion and Gas Turbine Engines, 2017
Thrust vectoring is the ability of an aircraft or other vehicle to direct the thrust from its main engine(s) in a direction other than parallel to the vehicle’s longitudinal axis. Thrust vectoring is a key technology for current and future air vehicles. The primary challenge is to develop a multi-axis thrust-vectored exhaust nozzle, which can operate efficiently at all flight conditions while satisfying the design constraint of low cost, low weight, and minimum impact on radar cross-section signature. The technique was originally envisaged to provide upward vertical thrust as a means to give aircraft vertical takeoff and landing (VTOL) or short takeoff and landing (STOL) capability. Subsequently, it was realized that the use of vectored thrust in combat situations enabled an aircraft to perform various maneuvers and have better rates of climb not available to conventional-engined planes. Additionally, which is most important, thrust vectoring can control the aircraft by engine forces, even beyond its stall limit, i.e., during “impossible” post-stall (PS) maneuvers at extremely high-nose turn rates [11]. An interesting “definition” for thrust vectoring is introduced in Reference 12 as a maneuver effector that can be used to augment aerodynamic control moments throughout and beyond the conventional flight envelop. Rockets or rocket-powered aircraft can also use thrust vectoring. Examples of rockets and missiles that use thrust vectoring are the space shuttle SRB, S-300P, UGM-27 Polaris nuclear ballistic missile, and Swingfire small battlefield.
UAS Sensing: Theory and Practice
Published in Douglas M. Marshall, R. Kurt Barnhart, Eric Shappee, Michael Most, Introduction to Unmanned Aircraft Systems, 2016
Rotorcraft, or rotor wing aircraft, use spinning wings as their primary source of lift. These take the form of propellers, similar to the ones used to generate motion in the fixed-wing and buoyant aircraft, the chief difference being these are designed to lift the aircraft’s entire weight and control it in flight. Because the spinning blades are used to generate lift, the aircraft is capable of vertical takeoff and landing (VTOL). There are two general types of rotorcraft, single rotor and multi-rotor. The single rotor, what we grew up calling helicopters, use a single main lift rotor to both lift and control the vehicle. The single rotor lift system is marked by complicated mechanical linkages that allow for the adjustment of blade pitch in both the cyclic and collective senses, which allows the vehicle to pitch and roll while varying the overall amount of lift generated. To counteract the single lift rotor’s torque, they also utilize a much smaller tail rotor, the speed of which is coupled with the lift rotor speed and enables the aircraft to yaw on command.
Takeoff and landing
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
Many cities, and, consequently, airports are located on mountainous or non-flat grounds. Thus, their runways have a positive or negative slope. When the runway has a positive slope, the aircraft has to climb during takeoff and landing operations. A runway slope functions similar to a climb/descent angle. To improve takeoff performance, it is recommended to take off in the downhill direction, but land in the uphill direction. This technique will reduce takeoff and landing distances.
Life-cycle analysis of electric vertical take-off and landing vehicles
Published in Transportation Planning and Technology, 2023
Khashayar Khavarian, Kara M. Kockelman
Many companies have suggested air taxis as a means to address urban-area congestion and air pollution. For example, Bell Flight is hoping that the U.S.’s first air taxi services will be between the Dallas-Ft Worth airport, the city of Frisco, and Arlington, Texas’ baseball and football stadia in the year 2025 (CBSDFW 2018). Their announced plan is to have 500 air-taxis, initially with human pilots, so passengers feel more comfortable (rather than autonomously managed aircraft). In collaboration with Uber, they are working on building vertical takeoff and landing aircraft (VTOL) for individuals who want to avoid ground congestion. VTOLs are not a wholly new technology, since helicopters are capable of vertical takeoff and landing, but their intended use in cities, with electrified propulsion (to reduce tailpipe emissions and noise), or eVTOL, is a new concept.
Design and Application of an Airborne Radioactivity Survey System Based on Unmanned Aerial Vehicle
Published in Nuclear Technology, 2023
Guoxiu Qin, Qinghua Yang, Jiarui Cui, Honggang Pan, Liangliang Pan, Fan Li
The system incorporates new devices and new materials and makes full use of highly integrated computer microprocessing technology. It integrates multiple modules, such as data acquisition, data storage, real-time transmission, communication control, and automatic peak stabilization, to reduce the size and weight of the system and reduce power consumption. This addresses the problem that UAVs used for ARS are restricted by a small payload, small space, and low power. In addition, the current practical ARS uses fixed wing aircraft (UAV) as flight platforms. This kind of flight platform is expensive, complex in operation, and requires a dedicated runway for takeoff and landing. It is unable to conduct hover measurements and meet the needs of fixed-point measurements in radioactive contaminated areas. In view of the above limitations, the designed ARS uses a small unmanned helicopter as the flight platform and uses two kinds of scintillators to form a combined detector, which meets the needs of nuclear radiation monitoring under complex terrain conditions. Under the limited UAV load conditions, more ideal spectrum data can be obtained by using two kinds of scintillators.
Assessment of aircraft landing gear cumulative stroke to develop a new runway roughness evaluation index
Published in International Journal of Pavement Engineering, 2022
Shifu Liu, Jianming Ling, Yu Tian, Jinsong Qian
It is worth noting that different aircrafts take off, land, and taxi on the runway at different times and locations, and thus, a certain location on the runway may correspond to different taxiing speeds. Figure 12 shows the taxiing speed of a B737 at different locations during takeoff and landing. Given the representativeness and uniformity of an evaluation index, a random constant speed for the LGCS cannot reasonably be assumed because the aircraft travels at that speed only on a small portion of the runway. Therefore, our strategy was to choose a speed at which the maximum aircraft dynamic response will be induced, and that critical speed is thought to be the most unfavorable for the aircraft. We then determined those critical speeds for our analysis as 100 km/h for the NLGCS model and 60 km/h for the MLGCS model.