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Dave

We Need You the Communites Help....

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You guys want the Gripen out? Then its time for you all to help us out. What we are going to need is a detailed explanation of the control surfaces, their functions, range of operation (degrees up/down), etc. I'm going to proceed on the assumption that the surfaces on the wings are elevons and similar to other delta winged control surfaces. If we can't get this info, it s dead in the water. And remember all we need is the FM to get it out to you all. PDF's, websites, dig in your garages.....We need the help.

 

Thanks

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Dead in the water 'eh? :blink:

 

 

Over G had accurate JAS-39A and JAS-39C Models. I'll see what each surface does in there later. I have numerous books that go in detail on the Gripen (and other Swedish birds) :ok:

 

NOTE: The following will be a complete guess until 9:25 EST.

 

I think the canards are the 'elevators' for the Gripen with the wing surfaces being flaperons.

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from what I see it looks like the canards act as airbrakes on the ground the canards move down to almost 90 degrees. The canards work in conjunction with the rear fuseloge lateral breaks. The landing breaks (canards ) are deployed once wheels have touched down at 220 km/h 136 mph. Thats all I have found

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I think the canards are the 'elevators' for the Gripen with the wing surfaces being flaperons.

 

That is a key question: are the wing surfaces flaperons or elevons? Are the canards responsible for all pitch control?

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Well this is all I have...but I will loook further :wink:

"...short-field landing performance is achieved by rotating the canard through almost 90 degrees to aid aerodynamic braking. The triplex digital fly-by-wire (FBW) flight control system controls the aircraft through two canards, the leading edge flaps and four elevon control surfaces. Saab claims the Gripen is the first inherently unstable canard fighter to enter production."

 

And here are some pictures on the ground with control surfaces(rudder,elevon,flaps and canards) brought to max , if nothing else one can judge range of operation by eye: http://ipmsstockholm.org/magazine/2000/04/...l_gripen_07.htm

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So, some additonal questions...

 

1. It appears that the inner control surfaces act as flaps. Is the flap system automatically controlled or manual? I'm going to assume automatic (for now) on an aircraft this advanced.

 

2. Do the wing inner control surfaces also contribute to pitch (elevator) and roll (aileron) control?

 

3. Do the canards operate at such extreme deflection only when the aircraft is on the ground? Seems unlikely that they would move that far in the air.

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Regarding C5's third question. From clips I've seen on landing it would appear almost as if they deploy automatically on touchdown. :dntknw:

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Regarding C5's third question. From clips I've seen on landing it would appear almost as if they deploy automatically on touchdown. :dntknw:

According to everything I've read this is exactly when they go in that extreme position.

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It is the only possible option. I f they were to deplor to the ""extreme" position during high speed 150+ mph it would send the aircraft into a downward stall and probably crush the pilot from the negative Gs. It is too large a wing surface to deploy ant such an angle at high speed. As far as the flaps go. It is best to assume that they work much like the f/a-18 flaps work. They move to creat role but only slightly. The su=-27 does the same. The canards I am certain do not control role.

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If you are going to hold up the Gripen until the FM and control surface movement can me modeled correctly, then it will be on hold indefinitely until TK decides to model complex fly-by-wire systems that mix control surface movements as required by the specific flight/load conditions.

 

For a taste of what you are up against, go here: http://www.dtas2007.nl/userfiles/file/Pape...Ansell-Blom.pdf

 

The canards normally move together and act together with the elevons to balance loads required to achieve desired pitch angles.

So there is some kind of digital schedule that decides how much to move the canards and how much to move the elevons depending on the speed, alt, g-load, etc.

 

In emergencies, the system will automatically move the canards independently as required to compensate for damage to other control surfaces.

 

Some interesting tidbits can be found here: http://www.gripen.com/NR/rdonlyres/4894FED...ws_2000_02.pdff

 

From what I have gathered at various websites/photos/writeups, etc:

Inboard elevons are essentially used as elevators but in such a way to behave as flaps for certain configurations such as landing and takeoff.

There is a very complex interaction between canards and elevons that depends on cg position, aoa, speed, alt, g-load, etc.

 

Outboard elevons definitely perform aileron function, I am not sure if they are used as flaps... but based on the the complexity of the fly-by-wire system, I am sure every surface is used to the fullest extent to minimize drag and/or maximize lift.

 

Here is a quote from a book on controls (Stability and Control of Conventional and Unconventional Aircraft Configurations A Generic Approach):

"The SAAB JAS 39 Gripen control definition includes a movable canard surface in combination with four elevons, rudder, and leading-edge flaps. It is possible to obtain a choice of either max. L/D-ratio or max. lift, depending on what is needed at a specific flight condition, using the canard and the trailing-edge control surfaces in combination. At cruise and manouvre conditions, the canard and elevons are optimized for low trim drag. At low speed, high lift is desired for short field performance rather than low drag. The emphasis is then to carry a high load on the canard to provide a substantial lift increase by deflecting the wing elevon trailing-edge down for trim. Thus, to obtain a high trim load on the canard, good canard high-lift characteristics were important in the choice of the planform for the close-coupled canard layout."

 

I have yet to find any references specifying max deflection angles, but assuming that the surfaces are at max deflection, photos such as these could get you in the ballpark:

http://ipmsstockholm.org/magazine/2000/04/...l_gripen_07.htm

Edited by streakeagle

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let's see...

 

donno if you've found this, but according to my four inch thick book of moderen military aircraft (c.2005) the canard foreplanes act as airbrakes when landing. Sorry, no pics. Everyhing else in here I think has been covered.

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Thanks for all of the info!

 

As usual with this game, we will try to mock up a convincing simulation even though the game's limitations prevent us from getting it perfect. ;)

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If you can somehow link the canard braking position to the wheel-brake key, that would be the best way to model it... especially if the fact that wheel-brakes can't be applied in flight also prevents deployment of the canard in flight.

Any other method I can think of would permit deployment in flight... which is unacceptable.

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