https://sci-hub.ru/https://arc.aiaa.org/doi/abs/10.2514/6.1991-3195
here is some information from the pre production trials if you are interested :)
and here is some general comparisons to generic delta canard configurations and their relative performances :)
i think you are talking about different things here, you are saying lift, he is saying lift-coefficient.
you are both correct in your statements just talking about different things and interpreting each other to mean the wrong thing.
if you are interested here is some general comparisons to generic delta canard configurations and their relative performances compared to wing sweep (mirage and gripen have different wing sweep) as well as comparison within the same wing sweep but with and without canards (F-16 and gripen has about the same sweep but gripen has canards)
:)
a canard has the possibility to gain up to 30% more efficiency in lift compared to the same added wing area but to main wing instead of canards (page 6-7 of this document). i’m not saying the JAS39 has maxed this efficiency but still. add to this that the canards are fully movable and thus able to optimize efficiency for any given AoA.
the fact that gripen also weighs about 2/3 that of the F-16 also helps, as it needs less lift converted into turn force to achieve a specific radius compared to F-16 that needs more lift converted into turn force for the same radius.
if you dumb it down into a basic circular motion (not really realistic i know but it shows my thoughtprocess):
the centriputalforce needed for a specific speed at a specific radius is:
a=(V^2)/r
and F=ma gives a=F/m
so
F/m=(V^2)/r gives F=(m(V^2))/r
which means that the force needed at a specific velocity and radius to maintain a constant circle depends on mass. since the mass of Gripen is about 2/3 then generally (and WAY simplified) the force needed to make that specific turn will be 2/3 of what the F-16 needs.
which would also mean that Gripen needs less AoA (and thus less induced drag) to make the same radius turn at the same speed as the F-16.
Now this is as previously stated WAY to simplified and there are LOADS more factors to consider. so its probably not even close to 2/3 the turn-force.
but it still shows something i don’t think i’ve seen others talk about before.
That being said:
Gripen in game is still very much overperforming, but i don’t think it is as egregiously overperforming as people think. like if it is now a 8/10 and people claim it should be a 4/10 i personally think it might be closer to a 5 to 6 /10. (numbers taken out my **** just to show what i ment).
Otherwise a very well written post! GJ! :)
Good stuff. Nice to get a better understanding of the actual relation of weight, aerodynamics/drag and thrust to performance, it’s not all linear and 1:1 as some people make it out to be.
The Gripen is widely known for its ability to “cut through the air like butter” and its advanced aerodynamics. A Gripen pilot also told me regaining / energy retention is where its advantage lies over the F16, not a proper source I could use in a report but still interesting context.
I firmly believe there’s truth to this. It’s a very complex subject, but I don’t think it’s fair to ignore the delta-canard configuration if bug report is going to be based off comparisons and referencing conventional designs. Especially when it seems that the issue in question is very much something the delta-canard would inherently have an advantage in… Do we have any info on the Rafale perhaps to use? @Giovanex05
asligtly off topic but still gripen.
recently released video of an intervew with a Gripen pilot WHILE IN THE AIR ON A SIMULATED COMBAT MNISSION!!!
Oh yeah, great video :) learnt some new stuff in it
Idk i havent had a problem with it but i wont deny the fact that 9m is a much better missile
Imagine the two aircraft performing a sustained turn at corner airspeed. For the F-16 to pitch up, the tail has to generate less lift/generate more downforce. This force is opposing the lift vector of the main wing. In the case of canard delta, to pitch upwards the canards are angled to produce more lift/less downforce. Because they are positioned in front of the wing, the canard and main wing forces are instead complementary whilst pitching up. This partially shows why the design is superior for a manoeuvring aircraft.
Additionally, the canards have beneficial aerodynamic interactions with the main wing which do not occur between the main wing and tail of a conventional layout. @Necronomica has linked the sources in this thread.
At this point I am not interested because I have already read like 3 - 4 different studies about close-coupled canards, leading edge root extensions, and wing strakes. Pretty much all of the studies come away saying more or less the same thing; that all 3 have the similar benefits as far as lift/drag is concerned. I am pretty sure this study is one of the ones that I read around two or three weeks ago.
I think a lot of people are insinuating that the movable canard is a much larger deal than it is. Even the study that you linked concludes the following;
Positive canard deflection causes an increase in drag and decrease
in (L/D) max. Small negative deflections can cause a slight increase in
(L/D) max. Neither positive nor negative deflections have a large effect
on maximum lift coefficient.
The actual adjustment to the Gripen flight model to make it somewhat believable would require substantial adjustments to the Lift/Drag values and the amount of AoA that is required to make the maneuvers that it does.
In-game the Gripen flight model should perform fairly close to the way the Mirage 2000 does on mouse aim with slightly better turn rates and slightly less speed bleed. The only place that the Mirage 2000 should be better than the Gripen is in near-stall scissors fights where the Mirage 2000 has the higher AoA limit.
Mirage 2000 vs Gripen vs F-16 dogfights are something that should be won or lost on very small margins. Currently the Gripen wins all of its fights fairly easily by more or less doing lag pursuit with max elevator deflection. The only real counter-move that Mirage 2000 and F-16 have against it is to just dump airspeed to force an over-shoot in the first turn and try to perpetually one-circle the Gripen to try to use its excess speed against it; and this is negated as soon as Gripen player understands that he can drop throttle and airbrake.
On the other hand the F-16 vs Mirage 2000 fight plays out in-game largely the way that you would expect it to. F-16 can consistently win against Mirage 2000…if it sticks to a pretty strict flight regime focused on rating and gaining an energy advantage.
This is something that is fairly hard to do in a pure guns-only fight and becomes incredibly hard if missiles are also considered. This is especially true now that the Magic 2 was buffed and that the radius that it can pull now will punish an F-16 that gives the Mirage 2000 too much space to work with; which is something that it will almost inherently do while rating at optimal speed. Just the presence of missiles means that the F-16 will most likely end up having to fight at a lower speed range where the Mirage 2000 has the advantage.
that is literally not at all the conclusion they come to?
Here are some graphs from that document about specifically lift/drag relations:
They write in the conclusion section as point 4 (page 44):
“The close-coupled canard delays stall of the wing and reduces drag at high lift conditions.”
and point 5:
“An optimum axial and vertical position exists which maximizes both
lift and (L/D) max* This position is at the point where the canard is
slightly forward of the wing-exposed root leading edge. Vertical separation
should be between 0.1C and 0.25C.”
that is for a static canard. the deflections are made pre test to see changes over the range of AoA at that deflection. meaning they only see a benefit in a small envelope of AoA for that angle and negative effects on the rest of the scope so not worth it over all. they don’t test movable canards and thus wont see how it looks when that canard angle is optimized for each AoA at the same time.
also specifically with “small deflections”. gripens canards move A LOT during high alfas at lower speeds.
and it still adds more total lift compared to adding the same area to the wing alone.
believable is firstly subjective and secondly believable to you.
this is very hard to quantify since they would win very much depending on the pilots knowledge on what to do to gain an advantage. in game most people just pull max turn as fast as they can and hope a one-circle turn into a rate fight will win them the duel no matter what plane they are in (at least in my personal experience).
Right now I don’t, can look into it thought
I will do them this evening for sure
The elevator requires positive trim to keep nose level, the lifting force is not downward… It is up. It is positive lift.
Likewise, the canard requires negative trim to maintain level flight and produces ‘downforce’. Previously I misunderstood the canard layout for the Gripen, when it fully deflects it serves to redirect airflow at low speed… But interestingly, it increases the instability margin.
While the close coupler canard “energizes airflow over the wing”… the only time this matters is at high angles of attack beyond the FLCS limits. LERX work just as well at lower angles of attack when combined with leading edge flaps and the canards on the Gripen not adding to the overall lift in a turn… instead requiring additional down force throughout actually may negatively impact turn performance over the F-16s design.
That’s right
That’s not necessarly true. While canards to downwards lift they are energising the flown on a delta wing, which has very high area relative to the weight.
Delta wings in without canards in general offer large area and low drag but at the same time it’s easier for the flow to detach/get unstable/lose energy. Canards are working to prevent that
How would this matter only at AoA beyond the FLCS limits?
At maneuvering airspeeds airflow over the wing even at FLCS limits shouldn’t be limited or significantly detached compared to the F-16. Increasing airflow over the top to the best of my knowledge isn’t going to further enhance L/D over the F-16 design.
Firstly, that depends on airspeed and attitude.
Secondly, I specifically said for an aircraft which is turning and pulling gs.
…
For the F-16 to pitch up in a turn, the force produced by the tail surfaces needs to to change so that the tail moves down in relation to the centre of gravity. The more the F-16 wants to pitch up, the less positive/more negative the force needs to be. The opposite is the case for delta canards. For them, the more they want to point the nose up, the more the canards are producing lift in the same direction as the turn.
Not quite, see above.
That’s wrong, remember that we are talking about unstable aircraft, so the center of mass is behind the center of lift.
Since rotations are determined by momentums, to do this properly we must set a frame of reference and define in which direction rotation (and by consequence momentum) is positive and which one is negative.
For convenience i’d say we say that a positive rotation correspond to pitch up motion.
Since the center of lift is in front of the center of mass (through which passes the axis any moving object will rotate around) lift will cause a positive momentum, and the higher the rotation angle (which is angle of attack) the higher the lift.
Since lift momentum is positive we need a negative momentum (which will increase as well with AoA) to prevent the thing from spinning (without that the F-16 nose would just go upwards while tail goes downwards).
That negative lift momentum in the F-16 is provided by the stabilator, which is behind the center of mass. This means that in order to create a negative momentum the lift force must be positive (aka to prevent the tail from going downwards we need something that pushes it up).
The situation with canards is the opposite, as canards are in front of the center of mass, just like the lift coefficient, and since they are both on the same side canards have to do a negative force to do that negative momentum (aka since nose wants to go up they do a force to push it down).
That also can be seen by looking at gripen canards in airshow, at high AoAs they have a negative angle of attack (since they need to create that downward lift).
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.