航线ATP Flight Controls General

1、12FLIGHT CONTROLSPrimaryTheory & Design3A conventional airplane is one which has a separate main wing and horizontal tail and with the horizontal tail behind the main wing. An example of a conventional airplane is shown to the left. The most common control arrangement on the Conventional Airplan

2、e is Ailerons on the main wing for roll control and a horizontal tail known as the Stabilizer with moveable Elevators for pitch control. There is also a Vertical Fin with a Rudder for directional or Yaw control. Sometimes the fixed stabilizer and separate movable elevators are replaced by a single m

3、oving horizontal tail known as a Stabilator. 4Fixed Slots On most light aircraft slots are formed between the wing and the flaps. We will discuss flaps below. But, first we must consider how slots increase the CLmax of the wing.FLIGHT CONTROLSLeading Edge Devices5The two photos below show a bottom a

4、nd top view of a fixed slot in a light aircraft wingTOP VIEWBOTTOM VIEW6Slats On large transport aircraft, and some light aircraft, the slot closes during cruise. A device called a slat can be extended for takeoff and landing to achieve the same effect as the fixed slot shown above. The photo to the

5、 right shows the slats on a DC-9 The diagram to the right shows how the slot allows high speed air from under the wing to flow through. The slot is designed to accelerate the airflow and merge it with the boundary layer on the top of the wing. As a result, the stall is delayed. 7TYPES OF SLATS8The d

6、iagram to the right shows how the CL vs. AOA graph changes with a leading edge slot. Note that the slot (or slat) has no effect on the lift produced by the wing at small angles of attack.The primary effect of the slot is to increase the stalling angle of attack and thereby the CLmax.When you fly an

7、aircraft with slots you will notice that the aircraft can be flown at a much greater angle of attack, without stalling, than a similar aircraft without slots.,910FLIGHT CONTROLSTypes of Control Devices11At the rear of the fuselage of most aircraft one finds a horizontal stabilizer and an elevator. T

8、he stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight. The horizontal stabilizer prevents up-and-down, or pitching, motion of the aircraft nose. The elevator is the small moving section at the rear of the stabilizer that is attached to t

9、he fixed sections by hinges. Because the elevator moves, it varies the amount of force generated by the tail surface and is used to generate and control the pitching motion of the aircraft. There is an elevator attached to each side of the fuselage. The elevators work in pairs; when the right elevat

10、or goes up, the left elevator also goes up. This slide shows what happens when the pilot deflects the elevator. 12The elevator is used to control the position of the nose of the aircraft and the angle of attack of the wing. Changing the inclination of the wing to the local flight path changes the am

11、ount of lift which the wing generates. This, in turn, causes the aircraft to climb or dive. During take off the elevators are used to bring the nose of the aircraft up to begin the climb out. During a banked turn, elevator inputs can increase the lift and cause a tighter turn. That is why elevator p

12、erformance is so important for fighter aircraft. preventing a loop. If the pilot reverses the elevator deflection to down, the aircraft pitches in the opposite direction.13The elevators work by changing the effective shape of the airfoil of the horizontal stabilizer. As described on the shape effect

13、s slide, changing the angle of deflection at the rear of an airfoil changes the amount of lift generated by the foil. With greater downward deflection of the trailing edge, lift increases. With greater upward deflection of the trailing edge, lift decreases and can even become negative as shown on th

14、is slide. The lift force (F) is applied at center of pressure of the horizontal stabilzer which is some distance (L) from the aircraft center of gravity. This creates a torque T = F * L on the aircraft and the aircraft rotates about its center of gravity. The pilot can use this ability to make the a

15、irplane loop. Or, since many aircraft loop naturally, the deflection can be used to trim or balance the aircraft, thus 14FLIGHT CONTROLSTypes of Control Devices15Sometimes the fixed stabilizer and separate movable elevators are replaced by a single moving horizontal tail known as a Stabilator. 16FLI

16、GHT CONTROLSTypes of Control Devices17 At the rear of the fuselage of most aircraft one finds a vertical stabilizer and a rudder. The stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight. The vertical stabilizer prevents side-to-side, or y

17、awing, motion of the aircraft nose. The rudder is the small moving section at the rear of the stabilizer that is attached to the fixed sections by hinges. Because the rudder moves, it varies the amount of force generated by the tail surface and is used to generate and control the yawing motion of th

18、e aircraft. This slide shows what happens when the pilot deflects the rudder, a hinged section at the rear of the vertical stabilizer. 1819FLIGHT CONTROLSTypes of Control Devices20The V-Tail concept is based upon the removal of the vertical stabilizers drag and weight and combining its function into

19、 the horizontal stabilizer.21FLIGHT CONTROLSTypes of Control Devices22 Ailerons can be used to generate a rolling motion for an aircraft. Ailerons are small hinged sections on the outboard portion of a wing. Ailerons usually work in opposition: as the right aileron is deflected upward, the left is d

20、eflected downward, and vice versa. This slide shows what happens when the pilot deflects the right aileron upwards and the left aileron downwards. The ailerons are used to bank the aircraft; to cause one wing tip to move up and the other wing tip to move down. The banking creates an unbalanced side

21、force component of the large wing lift force which causes the aircrafts flight path to curve. (Airplanes turn because of banking created by the ailerons, not because of a rudder input. 23 The ailerons work by changing the effective shape of the airfoil of the outer portion of the wing. As described

22、on the shape effects slide, changing the angle of deflection at the rear of an airfoil will change the amount of lift generated by the foil. With greater downward deflection, the lift will increase in the upward direction. Notice on this slide that the aileron on the left wing, as viewed from the re

23、ar of the aircraft, is deflected down. The aileron on the right wing is deflected up. Therefore, the lift on the left wing is increased, while the lift on the right wing is decreased. For both wings, the lift force (Fr or Fl) of the wing section through the aileron is applied at the aerodynamic cent

24、er of the section which is some distance (L) from the aircraft center of gravity. 24 This creates a torque about the center of gravity. If the forces (and distances) are equal there is no net torque on the aircraft. But if the forces are unequal, there is a net torque and the aircraft rotates about

25、its center of gravity. For the conditions shown in the figure, the resulting motion will roll the aircraft to the right (clockwise) as viewed from the rear. If the pilot reverses the aileron deflections (right aileron down, left aileron up) the aircraft will roll in the opposite direction. We have c

26、hosen to name the left wing and right wing based on a view from the back of the aircraft towards the nose, because that is the direction in which the pilot is looking. 2526FLIGHT CONTROLSTypes of Control Devices27The amount of lift generated by a wing depends on the shape of the airfoil, the wing ar

27、ea, and the aircraft velocity.During takeoff and landing the airplanes velocity is relatively low. To keep the lift high (to avoid objects on the ground!), airplane designers try to increase the wing area and change the airfoil shape by putting some moving parts on the wings leading and trailing edg

28、es. The part on the leading edge is called a slat, while the part on the trailing edge is called a flap. The flaps and slats move along metal tracks built into the wings. Moving the flaps aft (toward the tail) and the slats forward increases the wing area. Pivoting the leading edge of the slat and t

29、he trailing edge of the flap downward increases the effective camber of the airfoil, which increases the lift. In addition, the large aft-projected area of the flap increases the drag of the aircraft. This helps the airplane slow down for landing.282930Flaps Hinged surfaces attached to the trailing edge of a wing, either to increase maneuverability or to increase lift at the expense of dragThe simplest is the plain flap shown below: 31Split flaps are