What is Angle of attack?

What is Angle of Attack?

Angle of attack is one of the most important features in an aircraft or airplane because angle of attack effects the lift of the airplane. This angle of attack concept is also used when the plane has to takeoff or land. So, angle of attack is a very useful concept if applied properly in aircraft and airplane.

 What is this angle of attack?

It’s as simple as the name suggest that it is an angle and angle is measured between two lines. So first of all to define the angle of attack and understand it properly. We have to first know about the two lines between which the angle is measured. Here these two lines are known as vectors(It is a line segment with an arrow on one side of line which displays a quantity graphically representing the direction as well as magnitude of that quantity, it’s length of line segment is magnitude of that quantity and arrow facing is the direction of the movement of that quantity ) in technical terms. The first vector is pointing towards the relative motion direction between the body(airplane, aircraft) and the fluid through which it is moving(air). Now what does this relative motion direction means if we analyse the flight of an airplane or aircraft then we see that the direction of the plane flying and direction of the wind striking it is not the same so to sort out this problem we consider a relative motion vector between these directions. Second vector is the reference line (Centreline) of the body of airplane or aircraft. Sometimes the second vector is also taken as chord line of the aerofoil. Here aerofoil is the name given to a particular shape of wing used mostly everywhere in the airplane or aircraft, so the imaginary line passing through the leading edge and trailing edge of the aerofoil shape is known as chord line. The angle between these two vectors is known as angle of attack. It’s a bit confusing but don’t worry we will once again rethink it. The angle of attack is the angle between the chord line of the wing and the vector representing the relative motion between the aircraft direction of movement and the air direction of movement.

 What is the use of this angle of attack ?

As I explained in the first paragraph that it is used for changing the lift of the planes.

How does this angle of attack effects the lift of the plane?

To understand this we have to first understand that how the lift is generated. The magnitude of the lift generated by an object( in our case airplane or aircraft) depends on the shape of the object and how it moves through the air. The lift in the airplane or aircraft is produced by it’s wings. The angle of attack in simple words we can say that is the inclination of the wing to the flight direction of the plane. This has a large effect on the lift generated by the wing.

This phenomenon is used during the takeoff of plane by the pilot when an airplane takeoff, the pilot applies as much thrust( large forward push applied due to engines )as possible to make the airplane roll along the runway. But just before lifting off, the pilot rotates the aircraft  (the aircraft has three axes shown in figure below so the aircraft can be rotated about these three axes by controlling the horizontal & vertical stabilizer provided at the trailing edge of the aircraft) due to this the nose of the airplane rises, leading to increase in the angle of attack and producing the increased lift needed for takeoff.

The angle of attack is determined by calculating the length to width(L/D) ratio of the airplane or aircraft wing as well as body and kept as per requirement to get different outcomes like to achieve good glide , to achieve an increasing lift  etc.      

→For small angle of attack, lift is related to angle of attack

    Greater angle = Greater lift

→For larger angle of attack, the lift relation is complex

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