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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

• 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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• Thank you

Helicopters are the true flying machines

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How does a Helicopter fly ?

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OolongCha posted on 2022/01/26
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