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 …
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.
'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.
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...................?
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.
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.
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
The Register 
Biting the hand that feeds IT
Copyright. All rights reserved © 1998–2024
