Fundamental Forces of Flight.

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Fundamental Forces of Flight.

Primarily 4 forces act on an aircraft:

  1. Weight
  2. Lift
  3. Thrust
  4. Drag

 

Fig 1: Fundamental forces of flight

WEIGHT:

Weight of the aircraft is the force that acts at the center of gravity in downward direction (in the direction of acceleration due to gravity). The direction is fixed and doesn’t change during the course of flight, as acceleration due to gravity always point towards the center of earth.

LIFT:

To counter the weight and allow the aircraft to be airborne and not to fall back to earth surface, aircraft must generate force opposite to weight and which is equal to or greater than weight. The lift force is generated by the wings when the airflow causes pressure difference in the upper and lower part of wing i.e. high pressure at lower part of wing and low pressure at upper part. This pressure difference generates lift. Lift acts perpendicular to the direction of motion of aircraft.

THRUST:

Thrust is the force that propels (or pulls) the aircraft forward and is generated by the engines. It is responsible for the forward acceleration of aircraft. Thrust force is always parallel to flight direction.

DRAG:

When the aircraft moves through the air in atmosphere due to the interaction of air with body there will be force that will oppose the motion of aircraft in the forward direction. This force is called drag force. Drag can be generated from various reasons like shape of aircraft body that air hits and friction between air and aircraft. Drag force will always be parallel to airflow and oppose the forward motion of aircraft i.e. opposite to thrust.

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