I notice that delta jets with canards seem to be fashonable lately...

Just a couple of questions:-

[ul][*] What difference they make in the manoeuvrability of the aircraft?[*] Are they configured like elevators or elevons?
[/ul]

Many Thanks,
=Adrian=

I think it help to pick the nose up on turns and giving you better rotation on take off. The canard works like a reverse elevator

And unlike elevators they also increase lift, and help to avoid stalls too...

Rgds, Enrique

It depends if they're fixed or not.

Daren

Canards not only help with avoiding stalls by acting as a lifting surface on the front of the aircraft but they also allow for greater and slower maneuverability. For slow, high AOA flight canards make all the difference. They work in conjunction with the elevons of a delta. Elevons go up to change pitch axis canards go down. They move together and are not coupled with the roll. Some people have coupled them with the roll and most moved them back to pitch axis only, just B/C on our models that is very hard to make fly right.

Hope this helps

Dave

Check with some Eurofighter Sport flyers. I've seen one that tilts the canrd more in direction of stream flow at high AOA (>45deg) & set to continue working with elevons for pitch control at very slow speeds. Impressive! Need to ask for details of this set-up.

Phil

Hi Dave, Canards help avoiding stalls mainly because of a low pressure vortex that flows over
the wing. this vortex lowers the pressure over the wing and delays the flow separation (stall) at high angles of attack. I also have this draw that perhaps could help. (excuse my poor english and translation).


Adavis, about your second question, the elevons can be used fixed, as elevators, or elevons... the best way to use them depends on the airplane selected and what kind of flying you want to
achieve.

Regards, Enrique

I`m courious about the stall issue here.
Can you explain me how the canards can avoid stalls?

Regards

Gudmund

quote:

ORIGINAL: erbroens

And unlike elevators they also increase lift, and help to avoid stalls too...

Rgds, Enrique


I`m courious about the stall issue here.
Can you explain me how the canards can avoid stalls?


Regards, Enrique

"Canard" generally refers to the surface used on aircraft whose force arrangements are based on the canard being the primary pitch control. The "foreplanes" on aircraft such as the Rafale, Eurofighter, Piaggio "Avanti", etc., are not canard aircraft in that sense, but rather they are 'multi-lifting-surface" designs. (As mentioned above, they assist in pitch, but are not the primary pitch control.) They can increase cruise efficiency, because the extra lifting surfaces help with the plane's equilibrium, reducing the balancing forces required (such as the above-mentioned constant down load on the elevator, in a "standard" plane) and allow the main lifting surfaces to be reduced in size, reducing drag.

The "Avanti" wing, for example, was able to be reduced 20% in size, by the use of the small foreplanes in the front. The horizontal stabilizer on that plane, (an inverted airfoil) which is still the primary pitch control, flies in an almost "no load" condition in cruise, reducing drag.

In a genuine canard aircraft, the force arrangement built into the aircraft is such that the canard is intentionally set to stall first. (i.e., the Long EZ) Theoretically, the main wing NEVER stalls, resulting in a safer aircraft.

Very good explanation Mike.

Here it is a kind of pic that I love to see, the vortex condensation effect of LEX on a high g pull over the wings on a F-16 , same pattern happens on Rafales,Eurofighters, and even the Concorde, that uses a double delta wing planform to achieve the same results.

Regards, Enrique

All I thought about, was the lifting component in the canards. I forgot about the lower pressure on the upper surface of the main wing, as the canards are flexing downards, creating reduced airspeed on this side of the main wings. Thanks to these small funny wings, they cause a reduced airflow on the upper side of the wing, and this is....??? More lift.

A second effect is the dynamic effect to the AOA.

As Albert once said: Allways in learning mode..

I heard way back, that there is no such thing as a stupid question, only stupid answers.
Well, this answer was not.
Thinking about it, it is very logical.

Hmm. Learning by living. Thanks.

Regards

Gudmund

I added a set to my Kangaroo works great...
less reflex needed
which makes ailerons more sensative
landings are smooth as silk no more HOP

Gudmund, most amazing fact in life and in this hobby as well, is that as more I learn, more I learn that I didn't know anything!

we are all in heavy learning mode...

Regards, Enrique

Roos and Hotspots fly great without canards, but they are more sensitive to CG and elevon throws adjustments to achieve good landings without hops. Adding canards, you have a lot more control authority to achieve good results... they also look cool too...[8D]

Regards, Enrique

Assuming the aircraft is a delta with "Eurofighter/Rafale" style canards; do the canards effect the Centre of Gravity location? If so, is there any simple way to calculate this?

Many Thanks,
=Adrian=

Yep, the canards affects the CG location,,, as they move forward the lift forces on the airplane, the CG would move forward too... and of course there is no simple way to calculate this... perhaps the simplest method to find a aproximated CG , is by trial and error with a simpler model, like a chuck glider or a EDF.

Rgds, Enrique