Littérature scientifique sur le sujet « Hawker aircraft, limited »

Abstract Future aircraft have a high aspect ratio wing (HARW). The low induced drag of the wing can reduce fuel consumption, which enables eco-friendly flight. HARW cannot be designed by using conventional linear aeroelastic analysis methods because it undergoes very flexible motion. Although absolute nodal coordinate formulations (ANCF) have been widely used for analyzing various flexible structures, their application to HAWR is limited because the derivation of the ANCF elastic force for wing cross section is difficult. In this paper, we first describe three ANCF-based beam models that address the difficulty. The three models have different characteristics. Second, an aeroelastic coupling between the beam models and a medium-fidelity aerodynamic model based on unsteady vortex lattice method (UVLM) is briefly explained. Especially, the advantage of ANCF in the aeroelastic coupling is emphasized. Finally, we newly compare the three ANCF-based models in structural and aeroelastic analyses. From the viewpoint of the convergence performance and calculation time, we found the best ANCF-based beam model among the three models in static structural and aeroelastic analyses, while the three models have comparable performances in dynamic structural and aeroelastic analyses. These findings contribute to the development of aeroelastic analysis framework based on ANCF and the design of next-generation aircraft wings.

Since it was first adopted in 1987, Aeronautical Design Standard ADS-33 has been through four major revisions, and the Mission Task Elements (MTEs) used to qualitatively assess aircraft handling qualities have been expanded to cover scout, attack, utility, and cargo missions. However, even the current version of ADS-33 (ADS-33E-PRF) focuses on the hover/low-speed flight regime with limited coverage of high speed (140-150 kts) and conventional rotorcraft configurations. The ADS-33E MTEs are based on legacy vehicles and were developed at an early stage of rotorcraft fly-by-wire technology. The U.S. Army National Rotorcraft Technology Center recently completed a multi-year project to develop MTEs for future high-speed configurations and missions using a series of simulation studies. This paper documents a flight test assessment of two high-speed MTEs - Break Turn and High-Speed Acceleration/Deceleration - using a UH-60M Black Hawk. The MTEs were deemed suitable for assessing high speed handling qualities of the UH-60M. The results of the flight test provided recommended updates to the task descriptions and course cueing requirements, and helped validate the desired and adequate task performance tolerance.

High altitude flight, approaching 65,000 ft and above, is becoming increasingly important for various types of aircraft missions. Unmanned Aerial Vehicles (UAV), either for military reconnaissance or commercial/scientific study, are leading the way. For the military commander, high altitude, long endurance (HALE) flight for UAVs provides a good field of view for a long period of time and provides reasonable safety of flight. The upper atmosphere also provides the possibility for uncrowded, direct commercial flights. In addition, supersonic business jets are looking for a flight regime that also could be in the upper atmosphere. Typically, commercial, off-the-shelf engines are adapted for use in high altitude aircraft. While this has provided some success, the engine performance is marginal and the cycles are not optimized for this high altitude environment. Aircraft such as the Predator C and the Global Hawk are already operating in the high altitude environment with turbofan engines. More study is needed to determine what engine cycle is best suited to high altitudes. The smaller engines currently used in HALE UAVs carry a unique set of challenges which constrain the problem of high altitude propulsion hardware choices. Turbine engines have the most promise, especially turbofans, because of the higher speeds that are possible for the aircraft. Preliminary turbofan cycle analysis indicates that higher bypass-ratios and high compressor pressure ratios will be needed requiring more power output from the turbine however, high altitude limits how large these values can and should be. High altitude flight drives the cycle to be designed and sized at the high cruise altitude resulting in considerable impact on the off-design engine performance. Small gas turbine engine technology predictions show that fan pressure ratios of 1.76, compressor pressure ratios of 16.6, bypass ratios of 4.54, and a thrust specific fuel consumption of 0.393 /hr are possible in the near future (sea level reference). The cycle studied found a fan pressure ratio of 1.57, compressor pressure ratio of 16.7, bypass ratio of 5.45, and a thrust specific fuel consumption of 0.436 /hr (sea level reference) to be typical for a small gas turbine engine designed to fly at 65,000 ft. High altitude flight also brings other issues. Environmental impact must be considered in any high altitude application. High altitude reconnaissance aircraft often carry an increased sensor array adding more electric power requirements to the cycle. Long endurance means the engine cycle must be extremely fuel efficient. If stealth considerations are to be incorporated in the aircraft design, then the engine must be embedded in the fuselage limiting engine cross-section. Last, engine operational control will be a key technology for high altitude, low Reynolds number conditions.