why do helicopters have tail rotor?

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why do helicopters have a tail rotor?

Image from: - Wikimedia

Have you ever looked at the small fan at the tail of some helicopters? What does that small fan do? What is need of that small fan?

Let's Find it out!

That small fan at the tail of the helicopter is known as the tail rotor. The tail rotor is very important in a case of helicopters. Without a tail rotor, it will become almost impossible to control the helicopter.

Before going to tail rotors lets take a look at how helicopter gets a lift?


How helicopters get a lift?

Image From: - Wikimedia

Helicopter consists of the main rotor at its top. That main rotor rotates and creates a difference in air pressure on top and below the blades. The high-pressure air below helicopter blade pushes helicopter up. It is same as how aircraft wing gets a lift. To know more about how an aircraft wing produces lift check out my this post


What is the need of Tail Rotor?

Image From: - Wikimedia

This was all about the lift to the helicopter. But with the production of the lift, in addition to that torque is produced in helicopter body. Torque is simply a force that tends to cause rotation  As we all know according to newton's third law, every action has an equal and opposite reaction. Similarly, as helicopter main rotor rotates, in reaction to that helicopter body will also start to rotate in the opposite direction to the rotor. If Helicopter rotor is rotating in the clockwise direction helicopter body will rotate in a counter-clockwise direction.

To prevent such rotation tail rotor is needed!

What does tail rotor do?

The Tail rotor is attached vertically to the tail of the helicopter. Similar to the main rotor of the helicopter, the tail rotor also produces lift to the blades of the tail rotor due to the pressure difference. But in this case, lift is horizontal. The Tail rotor simply pushes the tail of the helicopter in the opposite direction of the torque & prevents the rotation of the helicopter.


But not all the helicopters have tail rotors. They have other components to counteract torque.


Alternatives of Tail rotor

  • Co-Axial Rotors
  • Dual Rotors
  • NOTAR

1. Co-Axial Rotors

Image From: - Wikimedia

Such helicopters have two concentric rotors placed one above another. One rotates in Clockwise direction while the other rotates in a Counter-Clockwise direction to counteract Torque.

2. Dual Rotors

Image From: - Wikimedia

Dual rotors have two rotors placed side by side. One rotates in Clockwise direction while the other rotates in a Counter-Clockwise direction to counteract Torque.

Quadcopters (Quadrotors) have four rotors. Two of them rotates in Clockwise direction while other two rotate in Counter-Clockwise direction.

3. NOTAR

Image From: - Wikimedia

NOTAR Stands for NO roTAR. NOTAR system uses the fan inside the tail of the helicopter. Which pushes the high volume of air in the opposite direction of the torque.



Thanks for reading!
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