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How does a Helicopter fly ?



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Helicopters are the true flying machines

They can take off and land without the need for our runway

They can hover in the air it can maneuver in any direction in a 360 degree space

This video will unveil the complexity in science behind flying a helicopter

After going through the physics behind the helicopter flying you will also understand why helicopter pilots are doing an incredibly complex job

Helicopters use the Airfoil principle to generate lift

When the blades rotate relative to the air the special airfoil shape will generate lift force and make them fly

the blades derive rotation from an engine more specifically a turbo shaft engine

The compressor sucks the air in and pressurizes it fuel is burned in this pressurized and hot air

The hot exhaust leaves the combustion chamber passes through a series of turbine stages and make them turn

There are two Sets of turbines one turbine set turns the compressor and the other set turns the helicopters rotor shaft

Jet Engines of Airplanes are used to generate thrust force

However the primary function of the helicopters jet engine is to turn the rotor shaft

The most challenging part in helicopter operation is its controls that means how can it fly forward?

how can it fly backward

sideward

Or how can it Take a turn

The answer is quite simple just rotate the helicopter towards the direction you want to move and just fly

When the helicopter is at an angle the Force produced by the blade is not vertical

The horizontal component of this Force will make the helicopter move in the desired Direction

the vertical component of the Blade Force will Balance the gravitational force

Now the real challenge is how to turn the helicopter in the desired way?

To learn the science behind helicopter turning we need to learn more about the airfoil principle

the lift produced by an airfoil varies with the angle of attack

Generally the greater the angle of attack the more the lift

Now think for a moment what happens if the one blade were at one angle of attack and others were at a different angle?

The lift forces acting on the blades will be different in this case

The variations in the lift forces will definitely result in a torque that can turn the helicopter

You can observe the beautiful blade motion required to achieve this non-uniform Lift Force distribution

It is clear that the blades must keep on changing angle of attack so that at one particular location the angle of attack is

always the same

Such complex Of the blades is easily achieved by a swash plate mechanism

Get an exploded view and understand the basic components first

The bottom Swash plate does not spin, but it can move and tilt as shown

A top swash plate is fitted on the bottom swash plate Via a bearing

So the top Swash plate kid inherit all the motion of Bottom Swash plate while at the same time it can rotate independently

Top swash Plate is attached to the rotor Shaft with the help of a driver. So the top swash plate will always move with the blades

The blades are connected to the top swashplate with the help of control Rods

The interesting thing about this arrangement is that just by tilting the bottom swashplate

We will be able to achieve the varying Angle Criterion of the blades

That means with this swashplate tilt

We will always be able to maintain a positive

Angle of attack at the rear and a negative angle at the front portion of the rotor disk

in short Swashplate tilting backwards produces a torque as shown

This kind of control is known as cyclic pitch

now back to the basic helicopter control

How will this torque affect the helicopters motion?

The most obvious answer is that the helicopter will turn forward and move as shown

Unfortunately this answer is completely wrong

What happens in reality is the helicopter will turn sideward as shown this is definitely a weird effect

By applying torque in One direction to a rotating object the object turns in Different direction

This effect is known as gyroscopic precession

Gyroscopic precession is not a new phenomenon of physics if you carefully apply Newton's second law of motion to rotary objects

You will be able to predict this phenomenon according to Newton's second law Force is the rate of change of linear momentum?

Similarly torque is rate of change of angular Momentum

Let's consider this rotating blade. It will have an angular momentum as shown now

assume that the helicopter has tilted as shown due to some torque action if

You victoria lee subtract the first angular momentum from the second you can figure out the torque required for this operation it

Is interesting to note that to turn the helicopter forward the torque applied should be towards sidewards that means to tilt the helicopter?

Forward the Swash plate should tilt sidewards as shown

You can again verify from Newton's second law of motion

that if you keep the front portion at negative angle of attack and the back portion at positive Angle the

Helicopter will simply turn sidewards

Gyroscopic precession is a truly intriguing phenomenon, but it conforms perfectly with Newton's second law of motion

if you just lift the bottom swashplate without tilting it you can see how the angle of attack of all three blades will vary by

the same amount

This means that the helicopter lift Force will be the same in all three

Blades and the helicopter can move up or down without any tilt

Such blade control is known as collective pitch

If you have ever seen a helicopter you are all sure to have seen a tail rotor

every single rotor helicopter needs this tail rotor for effective operation

Without the tail rotor the helicopter fuselage would have spun as shown

This is due to a consequence of Newton's third law of motion

To Understand it let's focus on the Force transmission part of the rotor

We know the rotor gets the force of rotation Via a bevel gear connected to the engine the engine?

Bevel gear Transmits Force to the rotor bevel gear as shown however according to Newton's third law of motion

the Rotor bevel gear should Transmit an equal and opposite Force to the engine bevel gear

This reaction Force will make the whole helicopter turn opposite to the blade rotation along the helicopter center of gravity

The function of the tail rotor is to prevent such helicopter rotation by producing a force at the tail

By properly adjusting pitch angle of the tail rotor

Blades the Pilot can easily manipulate the tail rotor Force this way with the help of the tail rotor

Yaw motion of the helicopter can also be achieved

All the physics behind helicopter operation means that flying a helicopter is a truly challenging task

minut variations in Blade Angles make huge variations in Helicopter Behavior

Often the pilot has to do two or more operations together to achieve the desired motion

moreover the helicopter does not respond instantaneously to your inputs so the pilot should possess a good sense of balance and

coordination to navigate the Helicopter properly

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