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What were the advantages of biplanes?

  1. Aug 15, 2007 #1
    What were the advantages of biplanes??

    what were the advantages of biplanes??:confused::confused: i mean they were structurally more complex, had more drag and many things, then why the earlier flying machines were biplanes?? what made them more advantageous in earlier times??
    was their only purpose was to provide more lift?? if so, why aren't they used now(i mean, in air not in meuseums:wink:)
     
  2. jcsd
  3. Aug 15, 2007 #2

    mgb_phys

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    You get (almost) twice as much lift for a given wingspan.
    It was difficult to create long wings that were stiff enough to support themselves and the aerodynamic forces. Biplanes not only give you shorter wings but you can easily brace them against each other.
    The problem as you pointed out is that they are complex and give lots of drag.

    Some are used today, tandem wings (with one wing in front of the other) or canards (small wing near the nose) - they are more manouverable and usually don't need horizontal tails.
     
  4. Aug 15, 2007 #3
    More "lift" also means a lower stall speed in many cases and shorter/stronger wings. In both cases this adds to rough field performance and in air maneuverability.
     
  5. Aug 15, 2007 #4
    As I understand it in a canard both sets of wings create and add to the lift.

    In a main wing wth tail wing the tail wing creates a down force to counter some of the lift and maintain a level flight.
     
  6. Aug 15, 2007 #5
    so the complex built is the only reason behind the demise of such planes
     
  7. Aug 15, 2007 #6
    They are still around for all the reasons they first found favor (see stunt planes).

    The need for speed, paved airports, time is money.............call it what you will they are just not mainstream in todays world.
     
  8. Aug 15, 2007 #7

    russ_watters

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    Also remember the importance of thrust to weight ratio - those planes didn't have the option to fly faster to generate more lift.
     
  9. Aug 15, 2007 #8

    Danger

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    As far as I can remember (and it's been a while), the main advantage to canards is that they lower the stall potential for the main wings. You can have a steeper angle of attack at low power without falling down.
    The elevators don't counter lift; they simply change the pitch axis of the aeroplane. You get the same effect with elevons on a delta layout, which doesn't even have a 'tail'.
     
  10. Aug 15, 2007 #9

    mgb_phys

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    Yes, the canard has a higher angle of attack than the wing and stalls first, this pushes the nose down, increases the speed and automatically recovers.

    I'm guessing also that since the canard isn't in the wash of the main wing the aerodynamic controls on it are more effective than on a conventional tail.
     
  11. Aug 15, 2007 #10

    Danger

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    I'm not sure about that last bit, Mgb. It makes sense, but I've never seen canards with control surfaces. Usually, the whole thing moves (both sides together as a unit).
     
  12. Aug 15, 2007 #11
    why so??? why cant biplanes fly faster
     
  13. Aug 15, 2007 #12
    As mgb_phys already said, more drag.
     
  14. Aug 16, 2007 #13
    As far as I understood, at the dawn of aviation there was this widely accepted notion that the wing should be like a flat plate only cambered to give lift, which gave it poor structural integrity. Therefore they couldn't build a strong and light enough single wing to support more capable and heavier WW1 airplanes, although the first true WW1 fighter, Fokker Eindecker of 1915, was, as the name implies, single-winged. The thin-wing hypothesis was finally disspelled at the turn of 1920's by the folks from Gottingen.

    Once the structural problems were resolved, two wings simply didn't equate any more weight/drag-wise in most any practical use. Short span is good for roll-rate, therefore, as mentioned, aerobatics may profit. Also, biplane can be usefull for STOL design if efficiency is not an issue; An-2, designed in 1947 way after biplane concept was abandoned, can fly at about 55 km/h with light load.

    --
    Chusslove Illich (Часлав Илић)
     
  15. Aug 16, 2007 #14

    russ_watters

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    I'm talking historically - engines were not very advanced when biplanes wre in their heyday and their power to weight ratio was pretty low.
     
  16. Aug 16, 2007 #15

    FredGarvin

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    Engines were wretched back in the era of WWI. Horrible thrust to weight. They were definitely the weak link.
     
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