The importance of weight in air transport

How an aircraft fly

All aircraft have design limitations and one of them is weight. During the aircraft design there are four Maximum weights that being established by manufacturer: taxi or ramp weight, zero fuel weight, take-off weight and landing weight.

Take-off weight is the amount of weight that aircraft can lift from the ground. “Weight” is a force caused by gravitational force and in direction to the earth (downward). In order to fly, a greater force is required to lift. This upward force is called the force of “Lift”.

Wing provides the necessary force of lift for an aircraft. When air flows over the wing (aerofoil), due to the special design of the wing and the speed of air flows on top and below the wing, it creates a difference in pressure between the top and bottom of the aerofoil (wing). The top surface has lower pressure comparing the lower surface of the wing.  This cause air moving from bottom to the top of the wing and creates the force of lift.

This force of lift will be maximum when the angle is in certain value and being called “Angle of Attack”. If this angel being increased beyond a certain value, then the lift decreases and aircraft will starts coming down slowly.


Four Forces on an aircraft

To move forward aircraft use the engines and this force is called “Thrust”. This force must be greater than the force of friction of air and body (fuselage) of the aircraft which acts backward and being called the force of “Drag”.

This study is called Aerodynamics. Force of “Lift” being upward and force of “Weight” in downward direction cause bending and stress on the wings. Wings may bend upward or even break during extreme conditions. Weight of the fuel in the wings keep them straight. If there is no fuel in the wings and aircraft being loaded to maximum capacity, there will be a tendency for the wings to bend upward.


Centre of Gravity of Aircraft

Centre of Gravity is the point at which the total forces of weight is acting downward. The location of center of Gravity affects the balance and stability of the aircraft and must fall within specified limits established by manufacturer