Saab Viggen

[KJ_Lesnick]

Okay, I got a question for you.  When was it first possible to use canards, and the vortices off the canards to amplify the vortex off the wing?  Could the US have done this by the late 1950's to early 1960's?

[upnorth]

Canards, or similar structures, have been around since the early days of flight.

The 1903 Wright Flyer was of a canard like design, as were several other early aircraft designs.

As for the second part of your question, bieng as how designs like the F-102 and F-106 were of 50s vintage, I see no reason why engineers couldn't have married canards onto those designs.

[rickshaw]

I think the problem was visualising how the canards affected the airflow over the wing.  It wasn't until the advent of grossly swept wings that the problems of airflow over and along the wing were really studied in depth.  Once you get some understanding of that, you get vortex generators appearing, to direct the airflow over the wing.  The canards on the Viggen are effectively large vortex generators, ensuring that the large delta wing is more controllable and generates more lift than it normally could.   By directing the airflow off the canards over the delta, you get better control on the approach and greater lift at lower speeds.   The Viggen made extensive use of computer modelling in its design as well, to arrive at that solution.  It's canards are not used for manoeuvring.  It wasn't until the advent of cheaper, more powerful computers in the 1970s that we start to see close-coupled canard designs appear, which utilise the canards for manoeuvring, again something that required extensive modelling to create.

[KJ_Lesnick]

upnorth

As for the second part of your question, bieng as how designs like the F-102 and F-106 were of 50s vintage, I see no reason why engineers couldn't have married canards onto those designs.

Correct, and a canard would allow the landing speed to be lowered for the same alpha and a lower alpha for the same speed.  However, I'm not sure how much of a difference it would produce over having that effect PLUS the effect of using the vortices off the canard to amplify the vortex off the wing?


rickshaw

I think the problem was visualising how the canards affected the airflow over the wing.  It wasn't until the advent of grossly swept wings that the problems of airflow over and along the wing were really studied in depth.

And that was first studied post WW2...

Once you get some understanding of that, you get vortex generators appearing, to direct the airflow over the wing.  The canards on the Viggen are effectively large vortex generators, ensuring that the large delta wing is more controllable and generates more lift than it normally could.   By directing the airflow off the canards over the delta, you get better control on the approach and greater lift at lower speeds.

How does it compare to a double-delta in terms of lift amplification?  I'm pretty sure there would be an advantage in a canard for trimming purposes though (allowing the elevons to droop).

The Viggen made extensive use of computer modelling in its design as well, to arrive at that solution.

Could a good aero-engineer like Jack Northrop have conceived such a design earlier?  He did shape the nose of the F-5/T-38 in a way that did effectively produce a more controllable vortices off the nose which made for better directional control at high AoA (which is why the nose is wider than deep -- it's nowhere near the same as the shark-nose of the F-20, but nonetheless) so he had some early experience in manipulating vortices.

Regardless, why was the inboard wing-sweep on the Viggen lower than the outboard?

It wasn't until the advent of cheaper, more powerful computers in the 1970s that we start to see close-coupled canard designs appear, which utilise the canards for manoeuvring, again something that required extensive modelling to create.