Aircrafts and all the modern airplanes use a variety of engines and techniques to obtain the required flight power but the underlying core techniques however, remains the same. When we want to fly something, the essential ingredients for our recipe are lift and thrust. For beginners, lift and thrust are the two essential forces that account for the vertical and horizontal motion of aeroplanes. Lift is the vertical force acting on the wings of an aeroplane (as the name suggests, it lifts the place or gives it vertical motion) and thrust is the propulsive force generated by the engine (which makes the plane move forward).
Now the question arises. How can one generate sufficient lift? This is answered by an aerofoil (or airfoil). An aerofoil is the term given to the general shape of those bodies which can generate lift. In case of an aircraft, the shape of the wing is called the aerofoil. As shown in the figure below, an aerofoil when placed in the direction of moving air (either the aerofoil moves or the air moves), the air flows at a faster rate through the top of the aerofoil whereas the air at the bottom part moves relatively at slower speeds. The difference between the speeds of the air streams create a pressure difference above and below which causes an upward force on the aerofoil.
(Image courtesy: T-9000, en.wikipedia)
This upward force increases as the speed of motion of the aerofoil increases. The aerofoil is usually kept at an angle to the level ground and this angle is called the angle of attack.
Geometry of an aerofoil / airfoil (aircraft wing’s shape):
The components are: 1 – Zero lift line (along this line, the airfoil will produce zero airlift), 2 – Leading edge, 3 – Nose circle, 4 – Camber (curvature), 5 – Thickness, 6: Upper surface, 7 – Trailing edge, 8 – Main camber line, 9 – Lower surface
Since the problem of obtaining lift is now solved, we can concentrate our study on how to obtain the required thrust. This is the case were our engines kick-start the action. As mentioned above, a number of modifications came to the engines during the course of time but some of the basics can be still sketched out. Two main propulsion systems are recognized –one that uses propellers and the other which uses jet propulsion. The underlying principle in both the cases is that they obtain the forward thrust by forcing air from the back of the system, the difference lies in the way the air is being handled. The thrust is delivered as a result of burning of fuel within the engine and using the heat thus obtained to impart high velocity to the expelled air. Modern commercial passenger jets use air compressors that force air into the engines, which is then mixed with fuel and ignited in a combustion chamber and is made to run an air turbine and finally ejected through the back of the engine. The air ejected exerts a backward force on the engines which drives the aircraft forward.
The tail, rudder and flaps perform most of the balancing functions. But as mentioned above the key parameters are thrust and lift which were explained above.
