When an airplane is changing attitude in flight, it's moving around one or more of the three axes of motion, that passing through the center of its gravity. At the intersection of the three axes everyone is always at an angle of 90 ° relative to the other two.
The axis that runs from the nose of the aircraft and reaches the tail, is the longitudinal axis, the axis that runs from one to the other wing is the lateral axis and the axis that runs vertically from the center of gravity is the vertical axis.
The movements of the airplane in each of these axes are called Rolling, Pitching and Yawing. To achieve these movements, airplanes need the basic flight control systems, Aileron, Elevator and Rudder.
Aileron
It is a modular surface which controls the airplane's movement on the axis of roll. This surface is usually on the back of each wing. Ailerons are connected in a matter that when one goes up, the other in the other wing goes down correspondingly. So on the first wing we create negative lift and on the other positive. This eventually causing one wing to rise upwards and simultaneously the other downwards. In this way we change the tilt of the airplane around the longitudinal axis, so we have rotation to the left or to the right.
Elevator
Elevator is another flight control system, in which the pilot can control the aircraft in the transverse axis (pitch) for climbing or descending. Elevator is usually on the back of the horizontal tail of the aircraft. It has the ability to move up or down and is controlled by the yoke of the pilot.
Here, unlike ailerons, we have the simultaneous movement of both surfaces creating either negative or positive buoyancy and forcing the horizontal stabilizer to move up or down accordingly. In this way we have change the position of the aircraft, putting it on climb or descent.
Rudder
In an aircraft rudder is a movable blade, connected by hinges to the back part of the vertical tail wing. It's used for movement of the aircraft on the axis of yaw. So when the pilot is moving the rudder, he can move the nose of the aircraft right or left. However, rudder is not used alone to turn the airplane. For turning an airplane, pilots use both aileron and rudder. The combination both of them results in the execution of a coordinated turn and helps to avoid slipping or skidding turns.
Using just rudder, we can turn airplane right or left but in a much lower rate. Sometimes the pilot can operate the rudder and make the plane deliberately on oblique course, compensating appropriately with the aileron, by turning it in the opposite direction.
The reasons that could do this is to overcome the existence of side winds, in an effort to stay aligned with the runway during landing , as well as to increase drag so that he can quickly lose altitude, without increasing the speed. Another use of the rudder on aircrafts with more than one engine, is to keep a steady course in the case of asymmetric thrust, due to the loss or detention of one engine.
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For FlightSimmer.GR
Giannis Evagelinos
