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Re:Wing in ground effect and Oops




> > James Cunningham wrote:
>
> Sam, I don't follow this.  Ground effect acts to reduce the losses to the
vortex
> shed at the wingtips, by reducing spanwise circulation, so it affects the
body
> and wings similarly.  For a given airspeed, the amount OF INDUCED DRAG is
> quantified by the aspect ratio and lift being produced, AND GROUND EFFECT
ACTS
> TO REDUCE THE INDUCED DRAG AS A FUNCTION OF THE SPAN/HAG RATIO.  Why
should
> ground effect pitch the body forward and down? -- I've never noticed that
when
> making a low level pass in an airplane.  What you do notice if you don't
reduce
> power is that, since you are going faster, you have to lower the AOA to
limit
> your lift to the sum of the weight of the aircraft plus the tail download,
so
> you deliberately lower the nose.  It has no tendency to want to do so of
its own
> initiative.
>
My premise for making those comments was that the pterosaur was moving fast
bipedally on land (hence the head tipping of it's own initiative.  I can completely understand your confusion as I believe wing in ground effect is the wrong term for what I mean (WIGE being a working principle while I am talking about one that does not) so apologies for using the wrong term. In essence, what  I meant, though, was:  as running speed is increased, lift increases to a certain degree but only behind the Centre of gravity, pitching an already front heavy animal at a diagonal.  I'm sure I've argued this biped point for far too long now so I'm going to stop - just wanted to clear up the confusion first.
 
Samuel Barnett
PS:  I hope you never DO have to experience that in an aeroplane, because if so, it means your plane is doing a wheely along the runway, it's fuselage is buckled in the middle and it's swing-wing mechanism has become L-shaped: It's a terrible shock to the average commuter's system - one which many people find hard to recover from :)