MAGIC THAT MAKE US FLY - LIFT

LIFT:

Lift is one of the four main forces acting on the aircraft. It is the upward force that makes an aircraft move up. If we sum up all the forces around airfoil we can able calculate lift, but it is super hard to do it.

DEFINITION :

The component of the net force perpendicular (or normal) to the flow direction is called the lift.

When the fluid flows past the object or any object move through the stationary fluid, the fluid exerts a force on the object, which can be split into components acting in the same direction as the fluid flow is called drag and the component acting perpendicular to the flow direction is called lift.

FALSE THEORIES:

Some of the widely propagated theories later proved to be false.

1. EQUAL TRANSIT TIME THEORY (OR) LONGER PATH:

This theory says the air molecule hitting at the leading edge of the airfoil, travels in the upper camber faster, and in the lower camber moves slower where exactly meet at the trailing edge of the airfoil at the same time.

Practically measured and found that the molecules never meet at trailing edge at the same time.

2. SKIPPING STONE THEORY:

This theory says that lift is the reaction force to air molecules striking the bottom of the airfoil as it moves through the air. It assumes that all of the lift is produced by the lower surface of the wing.

Practically measured and found upper surface also produces lift.

One more false theory is Venturi theory.

LIFT FORMULA:

It is dervied for bernoullis's principle.

L= 1/2 * rho * V^2 * A * CL

where,

rho - density

v - velocity

A- area of the wing

CL- Co-efficient of lift.

let's discuss each one by one

RHO (DENSITY)-

it is the ratio of mass to volume. Its unit is Kg/m^3. In order to get more lift, we need higher density. A higher density is achieved by higher atmospheric pressure, lower altitude, lower temperature, lower moisture.

VELOCITY (V)-

The greatest effect on the lift is by velocity. If velocity is doubled, the lift will quadruple.

AREA (A)-

It is the plane form area of the wing or surface area of the wing. This makes sense larger the wing, the higher the lift.

CO-EFFICIENT OF LIFT (CL)-

Amount of lift that particular airfoil produces. It is a dimensionless co-efficient. The lift coefficient is determined by many factors but three important ones are The Camber of the airfoil, The Shape of the plane form, Angle of Attack.

• The value of the lift coefficient at zero angle of attack is determined by the camber of the airfoil

• Stalling angle is influenced by the radius of curvature of the leading edge of the airfoil.

What does this lift equation mean to the pilot?

• In the lift equation, 1/2*rho*V^2 is dynamic pressure, the velocity in dynamic pressure is True airspeed, where the pilot manipulates True airspeed based on IAS(Indicated Air Speed). NOTE: Where the dynamic pressure is viewed as IAS in the cockpit.

• In lift coefficient the leading edge curvature and plane form area are fixed, the only thing left for us is AOA (Angle Of Attack)

HIGH LIFT DEVICES:

Flaps and Slats are known as high lift devices because based on various flight conditions it is used to produce or reduce lift other than wing itself, say during takeoff we need a high lift so the flaps and slats are extended in certain angle which makes the camber area to increase to provide more lift.

As for the pilot, IAS, AOA, High lift devices are used to manipulate the Lift.

QUICK QUESTION:

Does only wing produce lift?

Not only wing produce lift, but any object in motion under air will also produce lift.