How does a Helicopter fly ?
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How does a Helicopter fly ?

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 Your support at enables us to make further free educational videos, please support us at Thank you

About Ralph Robinson

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100 thoughts on “How does a Helicopter fly ?

  1. Dear friends, Please be a supporter of LearnEngineering. We can provide you more awesome contents in the future.

  2. Helicopters should have a system that allows thr machine to drop away the blades so your seat can get ejected and not die in this delicate machine.

  3. Yes I knew about the Turning bit because I collect RC helicopters. Modern RC helicopters have 2 propellers spinning opposite directions but I also have a old helicopter that uses the rear propeller that you talked about. I don't have to explain how it works because you did that for me. I can explain how the modern RC helicopters work though. The 2 propeller shafts that spin opposite directions, one of those will speed up to achieve yaw rotation then the rear propeller facing up can control forward and backwards. PS the old helicopter is in a state where it will perpetually Drive forward leeding to no control over hovering. The closest I can get to hovering is right after take off but then it will start moving forwards.

  4. im interested did somebody ever tried to get electric motor for side
    rotor? getting electricity from engine. might be lighter than shaft
    through half of helicopter and also simpler.

  5. im interested did somebody ever tried to get electric motor for side
    rotor? getting electricity from engine. might be lighter than shaft
    through half of helicopter and also simpler.

  6. Easy. They have a big fan in the top blowing down creating a force bigger than gravity making it go up. The wee fan on the back stops controls the body from spinning instead of the blades. I didn’t bother watching the video.

  7. copy is everywhere, and note :LearnEngineering Chinese Partner


    The helicopter is a true flying machine that can take off and land without the need for a runway. It can hover in the air and can be operated in any direction within a 360-degree space. This video will reveal the complex operation of driving a helicopter and the science behind it.
    not just one.

  8. At the first time helicopter made in India…. but all the weastern scientists were cheated with India…..

  9. Oh man, I have seen several other videos explaining the mechanics, I clicked on this thought maybe this one finally makes me understand completely and yes! At 3:58 I am absolutely in the picture and finally, understand what makes the blades doing the job and how it is connected to the control stick. It is pretty easy at the end 🙂 I always thought what the magic is behind the rods and all the stuff at the rotor 🙂

  10. My checkride for PPL AIRPLANE single engine land is tomorrow and I'm here watching videos on how HELICOPTERS fly 😂

  11. I’m sorry but as a qualified Heli instructor, you demonstrated how a small amount of knowledge is dangerous in the wrong hands, I could explain in detail how wrong you are on so many of your descriptions but I honestly don’t have the time, that’s how how many thing you have totally messed up. Your constant use of torque is wrong, your description of gyroscopic precession is completely wrong, and the fact you can’t even pronounce the word cyclic in your digital voice producer is just a laugh. Any one who gives this guy money to produce such utter nonsense deserves a stiff uppercut lol

  12. This video is not correct. Helicopters are not true flying machine. They are too ugly. Helicopters "fly" because the ground repels them in horror every time they start up. Now fighter jets are true flying machines and so they are lifted by the air gods themselves so they can be caressed and enjoyed by said air gods.

  13. How dose a helicopter fly …..well where i live .with no respect for any other liveing sole on the ground .an cause as much damage an dangerous flying as seemly possible as needed to get there hard on …

  14. Mèsi pou videyo sa/ merci pour cette video/ thank you for this video/ gracias por el video/ bedankt voor deze video.

  15. It's incredible! There are years I tried to understand some things explained here, and these are told in a very simple way. Congratulations, great job ☺

  16. Incredibly complicated engineering, had to watch a few times to fully understand everything going on. It's truly amazing.

  17. A explanation for dummies: Very fast fan do push. Push is very hard make helicopter go high as the big fan go taka taka taka taka taka.

  18. Do simplified that in fact wrong… and neverending airfoil story…
    The knowledge become really a rare good today…

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