On Sunday 30 May 2004 01:46, Innis Cunningham wrote:
> Hi Lee
>   Lee Elliott writes
> >In general I'd say no, but specific a/c could be configured to have this
> >feature.
> >
> >Spoilers and speed-brakes have different functions so a link between them
> >wouldn't seem to be appropriate to me.
> Not true on most Boeing commercial A/C the speed brake and spoiler
> function are very much intergrated as they use the same control surfaces.
> And seeing the B52 is a Boeing product and has no ailerons I would not
> be surprised if it did not do the same but I could be wrong.
> To use spoilers as roll control you would only need a property between
> 0 and 1 as the spoilers only go to faired with A/C I am farmilar with.
> This should be able to be implemented with the current property tree
> by summing the output of the aileron property with the speed brake
> position. With regard to the L/E slats the ones I am familar with are
> either in or out predicated on flap position.This does not mean that all
> slats are out at once.
> The 747 has two sets one that comes out at 1deg flap and the remaing
> set at 5deg.
> So if what you are proposing will lead to a more flexable system then. I am
> all for it.
> >Was there a specific a/c that prompted your question?
> Probably MD11 but that is just a guess(LOL).
> >LeeE
> Cheers
> Innis

As I understand it, the spoilers are primarily to dump lift, although they'll 
usually increase drag as well, producing a braking effect, so on a/c that 
only have spoiler surfaces and no specific speed-brake surfaces the spoilers 
may be used to give a braking effect.  The primary purpose of speed-brakes, 
on the other hand, is to dump speed but not necessarily lift.

Ideally, the course of the a/c shouldn't change when speed-brakes are used but 
spoilers should increase sink and this is how the spoilers can be used 
differentially for roll control - on the Buffs, raising the spoilers on one 
wing only will reduce the lift on that wing causing it to drop, producing 

On most of the a/c I can think of, off hand, the speed-brakes are fuselage 
mounted, to avoid effecting the lift from the wings I guess, but spoilers out 
of necessity must be wing mounted if they're going to reduce lift from the 
wing.  Having said that, the Avro Vulcan has speed-brakes mounted in the 
wings that extend vertically above the upper wing, but when they're fully 
deployed they are clear of the airflow over the upper wing surface.

The problem with using spoilers for roll control in YASim is that because the 
spoiler range is clamped to 0 to +1, when you 'split' the input for 
differential control it only works on one side of the a/c - through the 0 to 
+1 range - to get it to work on the other side it needs a -1 to 0 range but 
it can't do it, or at least it couldn't when I last tried.  That was on the 
YF-23, and I was trying to use the flaps differentially, instead of  the 
spoilers, but I think the same thing applies (the YF-23 used the ailerons and 
flaps in opposition for speed-braking and could deploy them on one side only 
for manuevering).

The change I proposed just really allows customisable spoiler settings for 
each a/c, as can be done with the flaps - I needed this for the B-52F, which 
has seven segment spoilers with seven positions (although from a few pics I 
found it didn't look like the segments are fully raised one at a time but 
progressively 'ripple' up, with several segments at intermediate positions, 
but that's beside the point).

Re the slats: I realised that there currently isn't a mapping for them already 
assigned in keyboard.xml and as this is a bit of a hot topic atm I'm not 
going to try suggesting one;) so for the time being the the change I proposed 
will only effect the spoilers.

As Andy R. pointed out, you can assign several control inputs to a surface and 
I've done just that with the BAC-TSR2 and YF-23, where the aileron and rudder 
control inputs, respectively, are bound to the elevator surfaces, so you 
could have the ailerons controlling the spoiler surfaces, except for the 0 to 
+1 range restriction.

To get the effect you want with the slats I think you would need to use 
non-linear interpolation on the flaps control input to the slats and think 
you could do this in YASim using src & dst tags.  I've only used them for 
scaling control inputs i.e. src0="-1" src1="1" dst0="-0.1" dst="0.1" to scale 
the control input by a tenth but I just quickly tried adding a third pair 
e.g. src0, src1, src2 & dst0, dst1, dst2, and it seemed to work, so you might 
be able to get the interpolation you need that way.

Of course, I might have just made a mistake when I tried to operate the flaps 


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