Aerodynamics

               :The four forces that affect the aircraft in the air are

 Gravity-

  Lifting-

  drag-

  momentum-

And gravity is the natural force that attracts the plane to earth direction. Leverage push the plane to the top against gravity. The drag force is normal force  of the air, which goes against the aircraft movement to forward. momentum is balanced with power of drag and
push the plane to forward. there are four major forces Control the aircraft

 Gravity-

Leverage -

the drag-

 momentum-

  gravity is the natural force that attracts the plane to the direction of the earth.  The lifting force is force which pushes the plane upward against the force of gravity.This force is generated due to movement of the plane's wing through the air. The drag force is the force of natural resistance to the air to move the aircraft forward   . the momentum is the force which opposed to the power of drag, it causes the movement of the aircraft to forward. momentum is generated  by plane' fans  or jet engines

When leverage of the plane equal to the force of gravity, and momentum equal to force drag, the plane fly in 

straight . When any changing  of one of these four forces, the plane begins to climb, or turn or change direction or change the situation. his part of  article Discusses   some of the ways in which the four forces effect the plane. The following section discusses how the pilot controls these forces

  Lifting force generated by low air pressure over the wing of the plane upper surface of the convex wing

low air pressure which takes over the convex surface when the plane is moving forward. The high pressure area is trying to always be moving in the direction of the low pressure, so the area of ​​high pressure below the wing rises in the direction of the low pressure so the plane rises up to the air

 The force of gravity and leverage. The force of gravity trying to maintain the viability of the aircraft above the ground or attracted towards the earth when flying in the air.And the force of gravity at the Earth is equal to the weight of the aircraft. it is necessary for the plane to take off  and remain in the air,  to generate leverage to take it up more than the force of gravity down

The lifting force is generated due to changes in air pressure on the aerodynamic section of the wing as the plane moved on the land of the runway  or in the air.  first attempts to fly using the wings Failed, where it was not understood then that the convex top surface of the aircraft wing is the main reason to generate power of lift. After the discovery of this fact, people started making airplane wings so that the upper surface slightly convex. And thus generated the lift power needed, as the bird wing

When the aircraft is parked, the air pressure on the wing from the top and bottom are equal, but when it moves forward, air begins to flow over and down the wing , moving air passing over the upper surface of the convex wing in the curved path increasing speed and less compress at the ssame time the air is moving passing through the lower surface of the wing in a straight line, it remains so consistent speed and pressure. The high pressure area is trying to always move in the direction of low-pressure area. Therefore, the air below the wing tries to move up But the wing stops against it .Therefore, instead of meeting the low-pressure area, the high pressure area lifts the wing in the air. when the plane go faster, a greater leverage generated by the wing. And increasing the speed of the plane during the running on the runway, before take-off, generates an increasing wing lift. In the end, when the pressure below the wing become more than the weight of the plane, and the leverage is greater than the force of gravity, the plane takes off

  How to generate momentum

  Drag force and momentum. Wing can only generate lift  when it is moving  forward through the air. To this plane, the engines are needed to generate the required necessary momentum  to start moving forward . to increase momentum, the plane has to move faster than before. However, with  increasing speed of the plane, increases the drag force.

To Resist this drag, the aircraft need for more momentum.  In jet engines, the momentum is generated by Rapid flow of gases through the engine. The fans generate momentum for helicopters and aircraft turbine reciprocating engines. the fans blades is Similar to the plane's wing .when you rotate the fan, the air pressure drops before it. Here the air of a higher pressure begins to move behind the blades to the direction of low pressure in front of the fan blades and pushing the plane forward. whenever the jet engine or fans rotation increased  generated momentum increased at the same time  To help increasing the momentum, engineers is seeking  for designing the fuselage in a very streamlined form as possible and also  designing a smooth plane surface and tight form, as designing of all outer surface parts  so that it can find its way into the air easily and softness

:Changing height

    when leverage Balance with the force of gravity, and momentum with the power of drag the aircraft fly in a straight and flat. To begin to land the plane the pilot must start to reduced engine capacity "This is done for jet engines and helicopter engines" by reducing the rotation speed of the engine to reduce the generated momentum . With the low momentum, also leverage reduces to start the plane to fall down. At the same time increase the drag force exerting downward pressure on the speed of the aircraft and increases the rate of decline.  To rise, the commander of the aircraft has to increase the capacity of the engines.And spin the propeller, or jet engine, more quickly to generate greater momentum.With increasing momentum, the leverage increases , the plane begins to climb.However, the rise of the lift force and drag , the aircraft need for more leverage. For the highest leverage, the pilot increased the angle of attack, the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. some of control devices is used to push the front of the plane to indicate a slightly higher, even wing makes a positive angle with the flight path and increase the speed of air passing over the upper surface of the wing to become a pressure less than the pressure in lower side and moving high pressure area below the wing to the area of ​​low pressure above generating lift. But continuing to increase the angle of attack eventually lead to turbulence above the surface of the wing and increasing drag force and restores the balance of power, the four pilot acting on the aircraft by increasing the engine capacity to generate greater momentum

Changing direction

 The pilot can rotate of the plane by increasing the lift generated by the wing or the other.  rotation to the left, for example, the pilot uses the control devices that put the plane in a lateral tilt to the left, ie, that  the left wing drops down from the right wing. The lifting force generated is always perpendicular to the surface of the wing. When the wing is not parallel to the horizontal surface of the Earth, the leverage is the other diagonal with the surface of the earth. And increase the leverage on the right wing when he drops the left wing, forcing the plane for rotation. The pilot uses the rudder to maintain stable flight mode. he Does not depend on the rudder to make a rotation, but the tendency of leverage when the wings at an angle with the horizon line is sufficient, that is leading to the plane of rotation.  When the plane begins to rotate, the leverage will be less than the anti-gravity and the plane lose some height. To restore the balance of four forces once again, the pilot can take one of two procedures, namely: 1 - increase the angle of attack increases the lift generated on the wings 2 - increase the capacity of the engines to increase the leverage to greater. In sharp turn, the pilot increase the angle of attack, and the ability of the engine at the same time, to prevent the plane to loss more height