Principle of flight

Principle of flight

Lift

Lift is an essential force in aerodynamics, which keeps an airplane in the air. Airplanes can fly because they generate lift by pushing air downwards. To do this the front edge of the wings are designed to be slightly higher than the rear of the wings, and the wings must also curve downwards. The angle of the wings to the horizontal is called the angle of attack. This helps to deflect air downwards as the airstreams follows the shape of the wings by the Coanda effect. The reaction to this force pushes the airplane upwards, explained by Newton's third law. The greater the angle of attack the greater the lift.

Thrust is also essential as it is the force that propels an airplane forward, created by propellers or jet engines.

Bernoulli effect

The speed of airflow is related to the amount of lift generated, which is why airplanes need a runway in order to create a greater speed of airflow. Te speed of airflow is greater on the top of the wing because air travels a greater distance but by the same length of time. The Bernoulli effect states that a faster moving fluid, such as air, would have a lower pressure than a slower fluid. So the lift pressure would be the difference in the air pressures between the top of the wing and the bottom of the wing, i.e. P2- P1. Therefore the amount of resultant force would be the lift, as Force= Pressure x Area

Force1 = P1 x Area of wing. Force2= P2 x area of wing

Resultant force (lift)= Force2- Force1

Limitations

The limitations in aviation are weight and drag, which are the other forces that are acting on an airplane. Weight acts in the opposite direction to lift, so the first thing airplane has to do is create more lift than its own weight. More lift can be created by increasing the angle of attack, but there is a limit to it as airstreams becomes disrupted and stalling the airplane. More lift can also be created through using larger wings, however larger wings also mean more drag, which is the frictional force between the airplane and air. Airplane produces drag because it pushes air out the way as it moves, but as technology improves, smaller wings and aerodynamic airplanes reduce drag.

Effects of controls

Once the aircraft is in the air, it is important that it could be manoeuvred. This can be done by deflecting airflows in different directions. There are three types of movements in the air, pitch, roll and yaw. Each controlled by different components. The pitch is the vertical rotations of the nose, controlled by the elevators. Roll is the rotations of the wings, controlled by ailerons and the rudder controls yaw, horizontal rotation of the nose.

Helicopters

The same physics applies in the flight of helicopter, however they use high-speed rotors that are tilted in the same way wings are to create lift. As rotors rotate at a high speed, they create an air stream above the helicopter, and the tilted rotors pushes this air stream downwards and air pushes the helicopter upwards. However, the rotation of the rotors creates rotation of the body to rotate in the opposite direction, known as the torque, so a vertical rotor is used eliminate torque.