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FLIGHT CONTROLS Types of Control Devices
THE ELEVATOR
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At the rear of the fuselage of most aircraft one finds a horizontal stabilizer and an elevator. The 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 the 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 elevator goes up, the left elevator also goes up. This slide shows what happens when the pilot deflects the elevator.
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The two photos below show a bottom and top view of a fixed slot in a light aircraft wing
BOTTOM VIEW
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TOP VIEW
Slats
• 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 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.
FLIGHT CONTROLS - 101
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FLIGHT CONTROLS Primary
Theory & Design
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Conventional Design
A 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 Airplane 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 moving horizontal tail known NTROLS Leading Edge Devices
Fixed 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.
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TYPES OF SLATS
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The diagram 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 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.,