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Airframes and systems - part 5

Oxford Hàng không ATPL Airframes & Hệ thống dạy các đối tượng Airframes, hệ thống và thiết bị khẩn cấp với các tiêu chuẩn theo yêu cầu của giáo trình giấy phép vận tải hàng không của phi công EASA. Mặc dù tất nhiên là có nghĩa là chủ yếu cho các phi công sinh viên chuyên nghiệp | FLIGHT CONTROLS CONTROLS b Horn Balance. The principle of the horn balance is similar to that of the setback hinge in that part of the surface is forward of the hinge line and forces on this part of the surface give hinge moments which are in the opposite direction to the moments on the main part of the surface. The overall moment is therefore reduced but not the control effectiveness. c Internal Balance. This balance works on the same principle as the set-back hinge but the balancing area is inside the wing. Movement of the control causes pressure changes on the aerofoil and these pressure changes are felt on the balance area. For example if the control surface is moved down pressure above the aerofoil is reduced and pressure below it is increased. The reduced pressure is felt on the upper surface of the balance and the increased pressure on the lower surface. The pressure difference on the balance therefore gives a hinge moment which is the opposite to the hinge moment on the main control surface and the overall hinge moment is reduced. d Balance Tab. All the types of balance considered above provide balance by causing some of the pressures on the control surface to act forward of the hinge line. The balance tab causes a force to act on the control surface trailing edge which is opposite to the force on the main control surface. The tab is geared to move in the opposite direction to the control surface whenever the control surface is deflected. 4. 2-4 Oxford Aviation Services Limited FLIGHT CONTROLS CONTROLS Figure 2.7 Unlike the previous types of balance the balance tab will give some reduction in control effectiveness as the tab force is opposite to the control force. e Anti-balance Tab. The anti-balance tab is geared to move in the same direction as the control surface and so will increase the control effectiveness but of course will increase the hinge moment and give heavier stick forces. Figure 2.8 f Spring Tab. The spring tab is a modification of the .