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Aerodynamics of helicopter - part 2

Văn bản bắt đầu với một lịch sử kỹ thuật độc đáo của các chuyến bay trực thăng, và sau đó bao gồm các phương pháp cơ bản của phân tích khí động học rotor, và các vấn đề liên quan kết hợp với hiệu suất của máy bay trực thăng và thiết kế khí động học của nó. | 24 AERODYNAMICS OF THE HELICOPTER helicopter. As a consequence of the tilt a component of the rotor thrust vector acts in the direction of tilt. The application of lateral control has therefore resulted in a tilt and sideward motion of the helicopter. Methods for obtaining lateral control are shown in Fig. 2-8. Note that while the initial effect of lateral control is a pure moment for the side-by-side machine the single-rotor helicopter experiences a side force together with the initial moment. Fig. 2-8 Methods for obtaining lateral control. a Tilt of rotor thrust b Differential thrust change 4 Longitudinal control. Longitudinal control is identical in nature to lateral control. Pitching moments are coupled with longitudinal forces. Methods for longitudinal control for various configurations are shown in Fig. 2-9. In the case of multi-rotor ships such as the tandem or side-by-side a fifth control is possible. This would enable control of longitudinal force without an accompanying pitching moment for the tandem or control of the side force without accompanying rolling moments for the side-by-side. Rather than introduce this fifth control force control is usually coupled directly with moment control as described above. A fifth control for longitudinal trim moment which is independent of horizontal force may be available in the tandem by differentially adjusting the pitch of the two rotors just as the horizontal tail is trimmed in the single-rotor or side-by-side machine. Cross effects are in general undesirable. For example in the singlerotor machine an increase in vertical force necessitates an increase in rotor torque so that a correction is required in directional control to maintain the fuselage direction. Such cross effects necessitate considerable coordination on the part of the pilot and result in longer periods of training in order to control the machine. c Fig. 2-9 Methods for obtaining longitudinal control. a Differential thrust change b Thrust variation .