back to article Boeing's X-Wing 737 makes first flight

Plane-maker Boeing has conducted the first test flight of the 737 MAX, the next version of the world's best-selling passenger airliner. The new plane offers the usual cocktail of new and lighter materials to keep weight and therefore costs down, along with technologies to keep the plane quiet and therefore less likely to annoy …

  1. xenny

    Less drag, not more lift

    The benefit of the winglets is a reduction in what's called 'induced' drag rather than any increase in lift.

    They do this by reducing the strength of the tip vortices (and presumably the amount of energy transferred to them, hence helping efficiency).

    1. Simon Sharwood, Reg APAC Editor (Written by Reg staff)

      Re: Less drag, not more lift

      I thought it was a bit of both. More wing area doesn't hurt. Smaller vortices help by smoothing out the air immediately adjacent to the plane. Together, PROFIT!

      1. xenny

        Re: Less drag, not more lift

        NASA seem pretty confident it's drag:

        https://www.grc.nasa.gov/www/k-12/airplane/winglets.html

        The winglets themselves are near enough vertical, so they don't really increase projected wing area.

        1. AndyS

          Re: Less drag, not more lift

          xenny's right here, in fact any non-vertical portion of the winglet is normally going to be producing a down-force, reducing total lift from the wing. This is what cancels out the wing-tip votex: Although across the vast majority of the wing the pressure is greater on the lower surface, at the tip it is reversed, to stop air from "slipping" round the tip to cause a vortex. This is called "wash out," and in a winglet design, the washed-out section is bent to near vertical so that the force produced is horizontally away from the aircraft, not towards the ground.

          Putting one up and one down cancels out this horizontal force to some extent (the lower one will push in, the upper one out). However the winglet will not be generating lift - just because it's a surface attached to the wing doesn't mean it's lifting the aircraft.

          1. Bronek Kozicki Silver badge
            Coat

            Re: Less drag, not more lift

            Given that lift force is proportional to the volume of low pressure air above the wing, if certain (small) volume of air is stopped from "slipping" round the tip, that would indirectly increase the volume of air producing lift, no?

            1. SkippyBing Silver badge

              Re: Less drag, not more lift

              'Given that lift force is proportional to the volume of low pressure air above the wing'

              Not according to NASA oddly enough https://www.grc.nasa.gov/www/k-12/airplane/right2.html

              Also the maths doesn’t work out if you calculate the force the pressure drop would produce.

      2. TeeCee Gold badge

        Re: Less drag, not more lift

        You have it. Without an endplate of some sort, high pressure air below the wing spills around the end and equalises pressure, meaning that the last couple of feet of a naked wing contribute nothing to lift (but still to drag).

        By preventing spillover, this air forms a neat vortex. Drag is reduced and lift improved. They serve the same purpose as the five large feathers that stick out from the end of an eagle's wing, which is where the A380 design team got the idea from (and as they came up with the system and are adamant it contributes to lift........!).

        A necessity for the 380 to keep the wingspan down to acceptable levels and retrofitted to other aircraft as more lift and reduced drag reduces fuel burn on takeoff and climb.

        Maybe when retrofitted to an older wing design it merely serves to reduce drag but when coupled with a wing surface designed to get the most out of the system...................?

        1. Martin Budden
          Joke

          infinite improvements

          The winglets help reduce wasteful wingtip vortices. But I'm concerned about the tips of the winglets: there is nothing there preventing them having their own little vortices. The winglets need wingletlets, and the wingletlets need wingletletlets, etc. A branching fractal wing.

          1. Highroads

            Re: infinite improvements

            Like the verse by Lewis Fry Richardson

            Big whirls have little whirls that feed on their velocity,

            and little whirls have lesser whirls and so on to viscosity.

          2. Alan Brown Silver badge

            Re: infinite improvements

            What surprises me is that wing fences haven't made an appearance on large aircraft. I guess the extra weight outweighs the benefit of preventing "sideslip" on the wing surface, but it'd be interesting to see what they'd contribute to lowering the stall speed.

        2. AC Wilson

          Re: Less drag, not more lift

          I thought Burt Rutan was doing this (winglets) many years ago.

        3. Anonymous Coward
          Anonymous Coward

          Re: Less drag, not more lift

          Maybe biplanes will be making a comeback. Thinks of all the space savings at the gate from reduced wingspans. And the roll rates - yippee...

    2. Anonymous Coward
      Anonymous Coward

      Re: Less drag, not more lift

      I wonder if this causes a significant reduction in wake turbulence. I hope someone googles that for me...

  2. Somone Unimportant

    Did anyone else think "Australia II winged keel side view?" when they saw that picture?

  3. Anonymous Coward
    Anonymous Coward

    Will they start back fitting these winglets to current aircraft?

    I think they did that with the current tips didn't they?

  4. Unep Eurobats
    Trollface

    World's most popular airliner

    In the sense that two is the most popular number of arms.

    1. boltar Silver badge

      Re: World's most popular airliner

      "In the sense that two is the most popular number of arms."

      Did you get to choose how many arms you were going to have at birth then?

      1. Magnus_Pym

        Re: World's most popular airliner

        As in the mode rather than the most beloved

      2. Anonymous Coward
        Anonymous Coward

        Re: World's most popular airliner

        I chose two, didn't you?

  5. casaloco

    IIRC...

    IIRC, the wingtips stop lift "bleeding off" the end of the wing. Essentially some of the air that would go under/over the wing to generate lift goes sideways off the end of the wing instead. The odd wingtips reduce that. IIRC it wasn't some egghead in a design office who came up the the idea, it was some common Joe on the factory floor. There was a "how do they do that" on Discovery channel a while back about it.

    1. Fruit and Nutcase Silver badge
      Happy

      Re: IIRC...

      before Joe on the factory floor, Mother Nature was equipping birds with drag and noise reducing wingtips

  6. Fruit and Nutcase Silver badge

    Big Wing, Small Wing

    Telegraph, "Pictures of the day" has the following today...

    'Wingmen' Yves Rossy and Vince Reffet flying alongside an Emirates A380 plane (the worlds largest passenger aircraft) during the world's first human twin formation flight

    http://www.telegraph.co.uk/news/picturegalleries/picturesoftheday/12139058/Pictures-of-the-day-4-February-2016.html

    http://i.telegraph.co.uk/multimedia/archive/03567/POTD_Wingmen_3567246k.jpg

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