How Do Helicopters Fly?

For many people, helicopter flight is a mystery. Photo by Helen Krasner

Many people think it is a complete mystery that helicopters manage to fly at all.

They reckon that a helicopter is like a bumblebee – it shouldn’t be able to fly, but nobody told the bumblebee.

However, helicopters fly by the same aerodynamic principles as any other aircraft, and the basic principles are really not all that complicated.

Lift, Drag, Thrust and Weight

The force needed to keep an aircraft in the air is called ‘Lift.’  Lift is produced by air flowing over the wings.

The shape of the wings is designed so that the air flowing over the top surface has to travel further, and it therefore travels faster, than the air under the wing. This causes the pressure of the air on the top of the wing to be lower, and so effectively the wing – and therefore the aircraft – is sucked up by this lower pressure.




In fact, a certain amount of lift is produced by almost any object in a stream of air.  You can experience the process for yourself if you put you arm out of the window of a moving car.  You will feel your arm start to rise upwards, and this is due to lift.  But of course a correctly-shaped wing produces far more lift than this.

Lift is produced independently of power from the engine. However, the engine produces ‘Thrust,’ which gets the aircraft moving along the runway, so that air flows over the wings. Thrust also overcomes ‘Drag,’ which is the force which tries to oppose the motion of the aircraft through the air. The other force involved is ’Weight.’ and the weight of the aircraft determines how much lift is required to get it into the air.

As long as there is enough lift to overcome the aircraft’s weight, and enough thrust from the engine to overcome the drag, then the aircraft will fly.

What About Helicopters?

While a helicopter is a far more complex machine than an aeroplane, the fundamental principles of flight are the same.  The rotor blades of a helicopter are identical to the wings of an aeroplane –when air is blown over them, lift is produced.  The crucial difference is that the flow of air is produced by rotating the wings – or rotor blades – rather than by moving the whole aircraft.  When the rotor blades start to spin, the air flowing over them produces lift, and this can cause the helicopter to rise into the air.  So, the engine is used to turn the blades, and the turning blades produce the required lift. Very simple!

Controlling the Helicopter

However, there is rather more to it than that.  You need to be able to lift your helicopter into the air when you want to, rather than just have it rise up as soon as you start the engine.  In the case of an aeroplane, flight can start as soon as the aircraft is moving fast enough.  But in a helicopter, for all sorts of reasons, the blades need to turn at the same speed all the time.  So you need a different way to control the amount of lift produced.

Click to Read Page Two: Controlling Helicopter Lift

© Copyright 2012 Helen Krasner, All rights Reserved. Written For: Decoded Science
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Comments

    • Philson Whittle Lawani says

      it is the weigth of the helicopter that will determine the lenght, breight and other condition necessary.

  1. john says

    elecopter movement depends on altering center of it gravity forward and backward with a little tweaking of its speed at the same time

  2. says

    I have created an rc helicopter but the only problem is to make it fly so i promiced my self that this holiday i will take my time and re-construct a new-one
    Now all i just need is money to conplete it so any one out there all i have to say is never give-up if only i gave up i wouldont have goten to this level i am in now
    No dream is too big or too small for any on wether big or small boy or girl man or woman never give-up.
    NEVER GIVE-UP.

    • Philson Whittle Lawani says

      the blade use in a helicopter rotor is not an audinary flat surfase, because if it be so Bernolli’s principle will not be active. The blade structure need to be in an airfoil nature so as to be highly active on principle of lift.

  3. Young engenieer bright says

    I need help in my aeroplane nd helicopter i jst made bt its a toy one nd i need a power source for it,nd if u can help me more cos i really want to be an engenieer nd everybody in my area no me so i need someone to sponsor me pls,nd pls how many secons a toy plane nd copter need to stay on d ground before goin up when put on

  4. says

    i ve adream to make this world proud of me. i feel i can make some thing more than just aflight machine. but put effort on cotper fast,i tried it in asmal experiment i got asmal electric motor(radio mtor),invented plastic blades and aplastic bottle plus a5v battry.am not saying flied, but i felt it working out as the weight reduced as it rotates meang,i lucked ahigh speed rotor.i want to improve my experiment to astandard project, am lucking fund.if any one can fund me, ican make the best one

  5. says

    I will be happy if anyone can answer this questions 4 me!!

    1. Pls,what and what are the works of the tail rotor?…

    2. Can the pilot alter the tail rotor pitch angle?….

    3. What type of material is best for helicopter construction?…

    4. Is there any part of a helicopter that is programmed?

    5. Does a helicopter has a speedometer?

    6. What is the work of a cross Bar at the tail of a helicopter?

    7. How does the swashplate works?

    8. Where does a helicopter engine stays?

    9. How many seats are there in a private helicopter?

    10. Can you produce any of the helicopter component locally???

    Thanks for your cooperation!

  6. Nkpandey says

    Can an electric motor run by a battery be used in making a helicopter and can someone may through some light as to how the wings of a helicopter are designed?

  7. Aj says

    What is it about the blade of a helicopter which causes the air which is pushed over them to increase or decrease in speed?

    • Matt says

      The pitch of the main rotor blades can be changed by the pilot using the collective control. This is what causes the change in the speed of the air flowing over the blade.

  8. Henry Amusah says

    Hi, pls I av a problem and I wish someone could help me, it’s one of my biggest dreams to make an aeroplane, I av read a lot abt how aeroplanes fly, its principles n even the forces that acts on a plane, I av gud understanding abt it, but the resources are my problem I tried making a prototype with styrofoam but I couldn’t get the radio transmission parts to buy here in Ghana especially Takoradi where am I pls if anyone can help me out I would be glad n suggestions will also be accepted Tnx.

  9. Okafor G Sylvester says

    I am a young engr I wntd to construct helicopter but I have limited idea abt the movement in the air pls can anyone give me sm clue?? tanz

  10. Jennifer jonse kingwealth says

    I am popurlerly know as young engrin my street.i am 12 yrs old, Am contructing an airplane but i don’t know how to apply more force. Is not that the is there but if it refuses to take off,i don’t know how tocontruct flap,elevator etc but with time i will,i dont have a sponsor i wish to have one, i can also construct many things bu t my problem is the airplane but with time i will prove with your help.wish is to make my country proud my invention.pls text me with any of your information concerning

    • Hephaestus-95 says

      that is good but to craft airplane or any aviation machine need more than just basic physic, it need knowledge in engineering dynamic and static that is specifically motion, material properties and deep understanding in electrical or circuit principle….and of course local aviation department license….

    • hosen ansari says

      Like you I don’t have a sponsor and resources and that is my weakness I have also many ideas to work out .and I think one day my country will proud at me

  11. Engr. Abdul-Fattah says

    I relation to the question; is there any other factor that causes lift apart from blades; yes, air currents can; as in gliders. Gliders don’t have engine but flies with air currents.

  12. Okoronkwo Ikechukwu says

    pls. can tigger gen be used as the rutor? and can the speed of tigger gen be enough to lift the helicopter?

  13. wilson says

    I really love this,tanx to d authur… I have a flying car project dat I plan to involve d principle of helicopter flight(air pressure)… My questions now are:
    1. Can d blades or rotors of a helicopter perform dsame lift operation if it was rather beneath the body?
    2. I intend using solar generated power,hence battery cells so am wondering who knows d average amount of energy or power is to b consumed by d rotor-blades to create a lift,say an average car weight of 1900 Kg to a height of 50 cm above ground level?…any related lift equation??
    3. Can d alteration of air pressure also occur horizontaly,like if I place d rotor lieing down and pointing ahead and fitting d blades to stand vertically,will there b a ”forward lift” against horizontal wind motion such as to propel d whole weight forwards or reverse???
    For any Ideas pls we can rub minds through Gmail…wilsonhoseaking@gmail.com, facebook…. Wilson hosea king, whatsapp no….will b provided via facebook….tanx vey much.

    • wilson says

      I am also puzzled about dat but one obvious thing is dat d heavier d copter,d greater d required force of lift and hence,d greater d required energy or power to be dissipited but not withstanding,since its a toy copter as uses batteries,I suggest dos 5V cuboid-like microphone batteries or even above…like 10V;or try getting acquainted to an elctricity Trainer Panel,(TPS) and keep alterating d output voltage until des enof power to rotate the blades to required speed…. Also u might want to consider the the efficiency or strenght of the rotor u r using…hence its its type of magnetic material…unno,a hard permanent steel magnet can produce faster rotations of the coils and the material of d coil’s wires shuld also b able to entertain high voltages else ur rotor sparks dead!… I hope dis is helpful.

  14. emm jai says

    i constructed a helicopter and i was successeul.. the helicopter lifts ud but cann’t move in the air. what can i do now?

  15. ogochukwu says

    i wish to build my own airplane nd am seeking enybody is going to sponsur me i hav the sence of doing it bt i did nt hav d money let do it in nigeria

  16. Amit srivastava says

    look,all u need a not only sharp blades but also……u know its size that can easily lift up your helicopters….and the length of the….blade should join its least distance….bczzzz…….whenvr its blades rotates faster your helicopters….will push more air down and its help to lift your helicopter up…………as u know ground effect…….

  17. idris adamu says

    for i have already create a helicopter but the only problem is how to control it when i lift it on the air that is my question please?

  18. chetan manorakar says

    if the weight of blade get more ,will it help for easy take off? because as weight increases the centrifugal force will be more and it will be help for take off.

    • Abhishek says

      It is not the centrifugal force which is responsible for the lift produced. It is the flow over the blades which produces the lift. Read how airfoils generate lift and you will understand. If the weight is more, it simply means that the downward pull is more due to gravity, and it will decrease the net upward force, resulting in more power consumption for lifting the helicopter upward.

  19. Cordell says

    I am a student at a charter school,and i am required to do a Genius project,and I chose the subject of how helicopters fly.if you have anything that can help me, can you send me some info? thank you for looking at my comment.

  20. raghu chouhan says

    Sir,how we calculate the ratio of weight,if by there will be more weight as it will not fly so how we get a better idea of its weight.

  21. David says

    Please how can i construct a small helicopter with slippers.what kind of electrical matterials will i use that will make it fly. Please answer me in time please.

  22. maxwell says

    Please. I need more elaborate information to help me construct a mini helicopter. And the kind of materials and electrical instrument I can make use of

    • rahul kumar says

      i know a another way of flying the airplane. in that we not need to more power and more extra electric motor.
      we not need any type of fule.
      in the basic principle of helicopter we need a rotor to rotate the air over the wings(blades) if we change the principle and rotate the air without using the wings(blades) then we xan also fly the cop. with a small distance travels just like a aeroplane. but after some time we can fly this just like a helicopter
      i have the basic project information in this project we not need the fule even in big hellicopter
      but i financial problem.
      if any one can finance me i can make the new generation of airplane that can operate with a small electrical energy.
      thanks.

  23. mike RAL says

    sorry to interrupt, “The rotor blades of a helicopter are NOT identical
    to the wings of an aeroplane”.. actually I have been told that they are somewhat
    symmetrical..If you calculate blade tip speed = blade circumference x r.p.m + forward flight….the answer is near the speed of sound.
    G-CHIS: the photo Robinson possibly could take you to CambridgeCollege over near Bedford…I visited there in 1985 as a friend was having the lads construct a water tunnel…for the study of helicopter main rotor blades.
    …carry on then ………….mikeR: AMT since 1981 (h500D, B206a/b)mostly

  24. Kunal says

    Ma’am is there a formula to calculate the lift for a helicopter. I am making a small Cancopter and want to know how can i judge the size of propellers. please help me out

    • 4k33m says

      A good guess is to make the blades approximately 1 and 2/3rds the total fuelsage length. Increase pitch or headspeed if nesscearry.

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