# What is Airfoil?

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One of the most spectacular things to view is the structure and the body of an aero plane. Its concept has always been scintillating and technical. It all started with the answer to how birds can fly. All of us do know that only when an object overcomes the earth’s natural gravitational pull, it tends to fly. The wing of an aircraft helps in gliding it through the wind and also in its landing and takeoff. The shape of such an important component of the aircraft makes a lot of impact on its movements. This shape is what is called an airfoil.

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### How does an Airfoil work?

We all do know how a bird flies; it maintains the pressure of the air around for its body to float. Similarly when a wing moves through the air, it splits and moves above and below the wing. The air passing above the wing gets spread out or expanded and hence the pressure decreases, while the air passing below the wing moves straight enough to maintain its speed and pressure. To maintain equilibrium higher air pressure usually moves towards a region which has lower air pressure. The air above the wing has lower air pressure as compared to air below the wing. Thus the air below is pushed upwards which in turn lifts the wing, sandwiched in between. This lift is due to the angle of attack and shape. When the air hits the wings it results in an opposite force to the direction of deflection. Its components are called as lift (perpendicular) and drag (parallel.) As the speed of the plane increases, more the lift and eventually when the force of motion (lift) is greater than the gravitational pull, the plane starts flying.

### What are the Components of an Airfoil?

A leading edge, a trailing edge, a chord and a camber are the components of an airfoil. The end which meets the air first is the leading edge and the trailing edge is at the end of the airfoil which is where the air with high pressure (below the wing) meets the air with lower pressure (above the wing). The chord is the imaginary line from the leading to the trailing edge. The camber is the curve on top and bottom of the airfoil.
Relative wind is defined as the direction of air flowing past the airfoil with respect to the direction of the flight. It is always parallel and opposite to the direction of flight.

### What are of the some examples of an Airfoil?

Some common examples of an airfoil are : Propellers, fans, turbines, Helicopter rotor blades, aircraft wings. Airfoils are also present in swimming and flying creatures and sessile organisms like sea urchins.

### What are the Various Types of Airfoils?

There are different types of airfoils,

• Semi-symmetrical Airfoil:  Most of the full size planes have this type installed. Its thinner than the symmetrical airfoil and has lesser drag. It has a fully curved top and a half curved bottom.

• Symmetrical Airfoil:  They are curved on both sides, equally. Generate high lifts with change in speed and power. They are generally thick and hence are very strong. The plane maintains its altitude with change in speed.
• Flat Bottom Airfoil:  Flat bottoms are usually seen in trainer flights. They look extremely thin. Its bottom is flat and top is curved. Flat bottom's are speed sensitive. They are similar to symmetrical airfoils. When power and speed is added it produces great lift
• Supersonic Airfoil: A supersonic airfoil is used to generate lift at supersonic speeds. Its need arises when an aircraft is operated consistently in supersonic range.
• Supercritical Airfoil: A supercritical is designed to delay the drag in the transonic speed rangeare a few to name.  A supercritical is designed to delay the drag in the transonic speed range. They have a flat upper surface, a highly cambered aft and a greater leading edge radius.

### What are the Advantages of an Airfoil ?

1. Cambered airfoils (asymmetric) are the kind which can generate a lift at a zero angle of attack.

2. It can increase traction of a vehicle by creating a downforce.

3. The angles of attack can be increased by symmetrical airfoil.

### What causes a Turning moment?

An airfoil has 3 forces. Lift, weight and drag. The lift is usually placed on the same spot as the weight, which is when the airfoil is stable and the plane has no problem, but usually when the lift is placed after weight force it produces instability in the airfoil which in turn produces a turning moment. This turning moment is compensated with the downward pushing force.

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