High AoA and attitudes, at relatively low airshow speed isn’t what we are talking about.
Again…you are considering when the aircraft is flying straight and level. I’ve said twice now we are talking about when pulling back on the stick in a turn. You can see for yourself in game that the F-16 tail pushes down when you’re at 800 kph and pull back on the stick and hold it in a sustained turn. Even if it wasn’t pushing down, surely you have to acknowledge that the amount of positive force it’s applying needs to decrease for the nose to pitch upwards to initiate a turn? How else do you think the tail is functioning to control pitch?
A source has been linked/referred to in this thread which specifically mentions how canards interact with the main wing to result in a net lift coefficient greater than the sum of them individually. The one @Necronomica linked. The source does not say the positive interaction is only at high AoA.
I may have misunderstood something: are we talking about when an aircraft is rotating (aka AoA is increasing) or when we are pulling on the stick to maintain a certain AoA?
In both cases changes little for the F-16, as in the first one the elevator will just provide a smaller amount of positive force to achieve that rotation while the latter case is the one I described above.
In the case of the gripen I think i have seen canards sometimes deflecting at positive angles to achieve a quicker rotation (quicker AoA increase), but that only happens when the starting AoA is also very low and as soon as AoA increases they need to revert back to doing negative lift to prevent the aircraft from spinning.
Still in a sustained turn you pull the stick to maintain a certain AoA, and in that case the F-16 elevator will, as I said, provide positive lift (the higher AoA the higher that lift), while the gripen canards will provide negative lift (the more negative the higher the AoA).
Also game animations are not to be trusted, gripen canards are deflecting in a completely wrong direction.
I’m a bit confused too, because I’m not really sure what it matters? When an F-16 is turning, the stabilators don’t just pitch the aircraft to a set AoA, and then return to producing “positive” lift. They have to keep providing that force to maintain AoA through the turn as the angular velocity changes. You can see this in test flight doing any speed sustained turn.
Yeah don’t base anything on the current in game gripen animation. It’s probably just copy/pasted code for the fluctuations of the viggens canard-control surfaces. But you can see this stuff on the F-16 in real life too.
I think you’ve over-estimating how unstable these aircraft are. It’s why the term “relaxed static stability” exists, it’s more accurate than negative stability. Look at the angle of the stabilators in this high speed pass https://www.youtube.com/watch?v=cWWK9w5uMgs.
the leading edge rot extension indeed does a similar thing. but ONLY at high angle of attack.
additionally its a static addition meaning its optimized for a specific angle where its effect is greatest. whereas the canard moves to provide that effect to maximum efficiency at every AoA. as well as level flight.
this exactly why LEVCON was later developed to achieve similar efficiency’s with root extensions as with canards. but the F-16 does not have that, only LERX.
There is a whole section that talks about benefits and changes in LD values for adding Close Coupled Canard and removing LERX from YF-17.
Here is another study that compares different configurations of Canard vs LEX. Authors also conclude that LEX and Coupled Canard have same benefit over just adding additional wing area.
Here is first study I can find just Google searching at the bar about LEVCON.
From what I am seeing there isn’t a substantial benefit to LEVCON until higher AoA.
Someone posted the EM diagram for the Lavi in one of the other Gripen threads. I think it makes sense to compare the two planes because they are very similar designs with similar weights, wing loading, and control schemes.
This is the original diagram.
This is the same diagram with the -1000 ft/s SEP line highlighted and red line showing roughly the airspeed at which it occurs. My working assumption is that the EM diagram airspeed is true airspeed and not indicated.
Basically what the diagram shows is that if Gaijin were to implement the Lavi, that it would lose 1000 ft/s in a max performance turn around 450kts.
Here is the current Gripen flight model under the same conditions; 50% fuel, 2x Aim-9L, and 15000 ft elevation. This is a max performance turn while using trim to overcome any compression limits if there is any.
Even if the chart is for IAS…the bigger picture does not significantly change. Actually its arguably even more egregious since the Gripen can make an 11G turn at this speed in the game…which should drastically decrease the SEP value.
At high speeds center of lift shiftes and, compression forces increase the force needed to rotate (if we had to make a comparison it would be a bit like adding a lot of friction to a pulley) and AoA is generally very low.
Also while the elevator there (in the picture) is tilted slightly backwards, the Angle with the airflow is still positive, it is creating a positive lift force
Lex gave improvement in lift of “up to 15%” and drag “up to 40%” at Alfa’s above 10°.
Above 16° Alfa there was a noticeable decrease in lift and an increase in drag.
With the movable canard improvements in both lift and drag on one configuration were “above 35%”.
Deflecting canards gave positive lift and drag in increments up to canard stall.
So:
Up to 15% lift and 40% better drag (again assumed better) with lex.
Which means a MAX improvement of those numbers.
And
Over 35% both lift and drag improvements with movable canard. Which means a MINIMUM improvement of 35% for both lift and drag.
Meaning
At its highest result the improvement in lift for lex is still 20% less improvement than a movable canard at its worst result.
And for drag the lex is 5% better at its best compared to canards at their worst.
Edit:
minor spelling and corrections.
so an improvement in lift gradually up to about 10% at alfas above 10 degrees with no real effect on drag to speak of until alfa 15-20 degrees where it is about 5% more.
lift to drag ratio at alfa 5 degrees to 15 degrees is about 10% better and above 15 it gets worse by about 5% until alfa 25 degrees.
you are probably only looking at lift here. lift to drag is more important a number when it comes to sustained turn rate.
that only mentions VATOL and RALS. not the Ejector model that gained the most improvements from canards
again only RALS and VATOL talked about.
the Ejector was the one that gained the most benefits as that model is the only one where they tested different canard positions.
they also write:
Spoiler
“canard produce similar or even more benefits than the LEX”
if you wanted to compare only the two without RALS being optimized post canard tests at different positions and angles.
this test is also very limited as it only tests 3 canard positions on one of the models. and only 3 models in total. not only that but as you said the bodies of the models are also different in addition to the canard/lex difference and the authors even specify (after the paragraph you posted):
Spoiler
so they aren’t factoring in that extra lift from the body in the results as you said.
during the development of gripen they tested a multitude of positions, sweep angles and sizes for the canards and wings to find the best combination (of course not only lift/drag but also some other specification requirements).
but doing more tests of positions, angles, chapes, sizes, sweep and so on gives you a WAY wider scope to choose from to optimize whatever you want optimized.
and as you previously stated;
the paper you linked show on movable canards:
Spoiler
to add to this Gripen is an unstable aircraft to the point where at sub sonic cruising speeds the canards have to negatively deflect about 5-7 degrees (sort of guessing the number here based on visuals, cant remember if i’ve seen the actual number) so to pitch the plane up canards go to neutral position for a short while and then negative again to stabilize the movement.
can be seen here:
That’s at transonic/supersonic speeds. You can find footage of F-16s doing demonstrations in the UK, where there is a strict restriction on airspeed, and the stabilators are still functioning as I’ve said.
Yes similar is correct. My car drives in a similar way to a formula one car. Not quite as well, but similar.
They aren’t moved continuously during flight as far as i understand the paper:
Spoiler
as in they have the deflection ability but where tested statically to generally compare to other changes for future tests to be made with dynamic canards.
at least as far as i understand it.
the section you provided screenshots of is the design section and not a physical build. they continue to talk about computer tested models with actuated canards but as far as i can tell the later tests were done statically at specific deflections of the canards.
(and please start using the spoiler function. its getting hard to scroll and find stuff in the thread to point back to).
Lift is still positive. The only way it would be negative is either the center of lift being behind the center of mass or the momentum created by engine thrust times sin(AoA) being high enough to do enough to prevent the aircraft from spinning.
If you read the article it talks about all performance, it just specifically mentions a large reduction in supersonic trim drag in that conclusion I screencapped.
I’ve never once said that the Specific Excess Power of the Gripen in game is accurate.
Is the FM of the Gripen in game wrong? Yes. That has always been the case, as @MiG_23M points out it is modelled as statically stable. It should be modelled as having relaxed static stability, and until that happens it is never going to be “accurate”. With regards to the SEP, it is probably due to simplifications in the physics engine of War Thunder. They try to recreate set parameters in game as best they can, but as an imperfect simulation not everything will match up until they do improve it.
Is the canard delta planform inherently superior for RSS fighter aircraft when the primary consideration is manoeuvrability? With our current understanding of aerodynamics, yes.
Then the article says basically the same thing that every other article says about canards, LEX, and strakes.
This seems to be the counter-argument you are trying to to form without explicitly stating it.
I am also trying to keep the thread on topic instead of hung up on idiosyncratic interpretations of a whole bunch of studies that more or less conclude the same thing.
There is a reason that conventional tail designs with LEX continue to be viable and why planes like F-16 and F-15 are still winning contracts and there is a reason that the only buyer for Gripen E has been Brazil.
