Severe adverse yaw: Unique characteristic the F1?

[Nealius]

I fly a lot of the analog Cold War jets from the F-86 to the F-5 and none of them exhibit adverse yaw unless at slow speeds/high AoA. I took the F1 for a spin and was surprised by the massive amount of adverse yaw and general yaw instability. I had to double-check the yaw/slip swtich was on and it indeed was. I'm finding that I have to use more rudder in the F1 than I do in the Spitfire or any of the WW2 props, which feels very strange. I know nothing of the Mirage, just that typically in fast jets adverse yaw isn't as much of a thing as it is in props, so I'm curious if there's something different about the Mirage's design that creates more adverse yaw compared to other jets of the era.

[Nealius]

Still unable to find sources about the F1's yaw characteristics. The F1 does use slats combined with ailerons: slats should produce proverse yaw and the ailerons, assuming frise or differential, should also reduce or eliminate adverse yaw. Yet we experience adverse yaw in flight regimes where none would be expected. 

So is it a unique characteristic of the F1, and if so caused by what?

Or is it a developmental issue that will be later tuned like the F-14 was when it initially had too much adverse yaw?

Edited August 2, 2022 by Nealius

[Lace]

On 7/22/2022 at 3:19 PM, Nealius said:

just that typically in fast jets adverse yaw isn't as much of a thing as it is in props,

Just thought I'd pull this point.  Adverse yaw is not a result of the propulsion method and is not necessarily more prevalent in props than jets.  It is caused by the downgoing aileron causing more drag as a result of the increased lift, and the upgoing aileron reducing drag and lift.  This is why you will yaw outside the turn, rather than into it, and it is not a product of P-factor.  It can be eliminated or reduced by various methods, such as differential ailerons (i.e. the downgoing moves less than the upgoing), spoiler deployment, or as I suspect is the cause of your confusion - a flight control (FBW, pilot gets a vote type) system as fitted to modern jets, which will automatically counter any adverse yaw and is why the effect is not generally witnessed in those aircraft.

Apologies if you are already aware of this and I'm teaching you to suck eggs, but the wording of that sentence grabbed my attention.

[sedenion]

Here is statement, found in french forum, from who appear to be a former Mirage F1 pilot... Unfortunately it is a very generalist statement, no specific mention of adverse yaw.

Quote

The plane is very stable in yaw, even at low speed. Where it is most unstable is in roll, where the use of spoilers and ailerons guaranteed it a fairly high roll rate for the time. It took two or three flights before being able to fly the wings flat without swinging from one wing to the other!

https://www.checksix-forums.com/viewtopic.php?p=1898881#p1898881

This statement is strangely close to what one could hear about the Mirage 2000 (very stable in yaw, high roll rate) despite the wings design difference and the absence of FBW for the Mirage F1. Could it be a "Dassault touch" ?

TL;DR

Spoiler

My intuition (so, nothing scientific and full of opinion) is that the current Flight Model is like a basis skeleton and need to be adjusted with some "flesh" and "skin". The general characteristics of the aircraft  (max speed, turn rate, roll rate, etc.) are relatively properly reflected, but it need adjustements to better reflect aircraft general behavior and in manovers near aerodynamic "limits". And this is perfectly normal. RAZBAM taked time to make a proper Mirage 2000, this took a lot of tries and errors.

I think many people can think "yeah, this is a non-FBW aircraft, such instability is normal, that is the challenge, let me tame this wild horse, look at the Mig-21, look at the tomcat" (seriously, look at Tomcat, look at Mirage F1, and tell me there is some comparison possible). To be honest, I even think there are biases about French aircrafts... It seem some people cannot imagine a French aircraft could fly as well as an american one for example (not to mention the case where it fly better, such a conspiracy theory !). As mentionned before, like the Mirage F1 currently, the Mirage 2000 was, at begining, compared to the Mig-21BIS... because "Oh, delta wing, so trange, so french, so "like Mirage III", so third-world aircraft"...

But, the fact is that Mirage F1 comes right before the Mirage 2000. Dassault already had a great mastering of aerodynamics and fligh controls optimizations, and actualy, the Mirage F1 is full of automated flight assistances that reflect this "state of art". Main Mirage F1 problem? The same as pretty all french aircraft: underpowered... That is the main indisputable weak point of the Mirage F1, lack of thrust. But in the other hand, Dassault is known to had mastered flight controls and making aircrafts with incredible flight characteristics, so there is no reason to think the Mirage F1 fly as bad as it currently fly in the simulation.

Edited August 2, 2022 by sedenion

[Nealius]

1 hour ago, Lace said:

a flight control (FBW, pilot gets a vote type) system as fitted to modern jets, which will automatically counter any adverse yaw and is why the effect is not generally witnessed in those aircraft.

This still does not address the fact that all non-FBW jets we have in DCS do not have adverse yaw. It also contradicts multiple real-world pilots who fly F-5s and T-38s who say that adverse yaw is so minimal that it's barely noticable in fast jets in general, not just their F-5s and T-38s. ED staff have also agreed with this when asked about lack of adverse yaw in the L-39, F-86, and MiG-15. This is also corroborated with Heatblur's flight model tweaks to the F-14, which initially exhibited too much adverse yaw and now does not. Furthermore, the F1's slats should be producing proverse yaw yet they are not. This leaves the F1 standing out from the crowd in terms of adverse yaw modeling. The question is why?

Edited August 2, 2022 by Nealius

[Lace]

6 minutes ago, Nealius said:

This still does not address the fact that all non-FBW jets we have in DCS do not have adverse yaw. It also contradicts multiple real-world pilots who fly F-5s and T-38s who say that adverse yaw is so minimal that it's barely noticable in fast jets in general, not just their F-5s and T-38s. ED staff have also agreed with this when asked about lack of adverse yaw in the L-39, F-86, and MiG-15. This is also corroborated with Heatblur's flight model tweaks to the F-14, which initially exhibited too much adverse yaw and now does not. Furthermore, the F1's slats should be producing proverse yaw yet they are not. This leaves the F1 standing out from the crowd in terms of adverse yaw modeling. The question is why?

 

Agreed, but that is a completely different question.  That is down to EDs flight models, and not real world physics.

[sedenion]

25 minutes ago, Lace said:

Agreed, but that is a completely different question.  That is down to EDs flight models, and not real world physics.

To have developed some physics engine and rudimentary flight model as hoby some years ago, my feeling about the current Mirage F1 flight model is that is typical of a little too simplistic "shape" modelisation based in well simulated physics dynamics. Theses oscilations around center of mass remide me a kind of "too perfect" model with very raw inputs... too perfect mean: not enough complex. But again, this is a feeling, I don't know the DCS engine and my experience still non-professional.

Edited August 2, 2022 by sedenion

[Ala13_ManOWar]

And this is why some ex-F1 pilots were around here and ran away quick, armchair pilots always know better no matter how you explain things .

[sedenion]

7 minutes ago, Ala13_ManOWar said:

 some ex-F1 pilots

Are you ? I am open to ex pilots comments to tell me everything is OK with the current Flight Model.

Edited August 2, 2022 by sedenion

[Nealius]

33 minutes ago, Ala13_ManOWar said:

And this is why some ex-F1 pilots were around here and ran away quick, armchair pilots always know better no matter how you explain things .

A. No one here thinks they "know better." If we did we wouldn't be asking questions.

B. What's your qualifications on the subject?

C. If you don't have anything helpful to add then don't waste our time with useless comments like this.

Edited August 2, 2022 by Nealius

[WinterH]

From the top of my head, the only other module that commands roll with an aileron on one wing and a spoiler on the other is F-14, which also has some degree of adverse yaw as far as I recall, it isn't a type I fly most often in DCS though. So having what is almost an airbrake open on one wing could potentially make it different from F-5 for example, at least I would think so.

Another plane we'll experience this sort of roll control will be the F-4 when it comes, and perhaps the F-8 too, not sure.

While I do agree saying "this is why actual pilots run away from the forums" seems rather unhelpful, no offense but the thread does give off a slight feeling of not liking something on a flight model for an aircraft that has just recently released, thus may not have given all people enough time to get used to idiosyncracies of the way it flies. Let's hear what Aerges have to say rather than bickering among ourselves I'd say

[Ala13_ManOWar]

1 hour ago, Nealius said:

C. If you don't have anything helpful to add then don't waste our time with useless comments like this.

And I go exactly like that. But that of yours is a blatant lie since you started this very topic with nothing good to say instead of searching around what's already written or sources about it anywhere, which is by the way also  how I do, I look for myself before accusing anyone, third party module maker or not, of "it's all wrong" .

Well done mates, well done. Over and out.

[BIGNEWY]

Please stop with the back and forth. 

 

Regarding the flight model, if you have evidence something is wrong bring it to the teams attention and add track replays I am sure they will look into them. 

thank you

 

[Nealius]

1 hour ago, WinterH said:

From the top of my head, the only other module that commands roll with an aileron on one wing and a spoiler on the other is F-14, which also has some degree of adverse yaw as far as I recall, it isn't a type I fly most often in DCS though.

Does the Tomcat have ailerons? I only recall spoilers and horizontal stabs that also move with roll input. The F1 is interesting in that it has both ailerons and spoilers, but the horizontal stab only moves with pitch input, not roll input. I've flown the F-14 extensively since release, and the current F-14 flight model does not exhibit adverse yaw except in slow-speed high AoA (prior to the regime where you need 100% rudder due to lack of airflow over spoilers/horizontal stabs), but only if you "fly the cross." If you give blended inputs it might do something different, but since I haven't been giving her blended controls I can't say if that's the case. I would still expect the F1's slats to produce more drag on the inside wing, therefore create proverse yaw or cancel out the adverse yaw. 

1 hour ago, WinterH said:

no offense but the thread does give off a slight feeling of not liking something on a flight model for an aircraft that has just recently released

The first two posts are an unbiased question of if it's accurate or not. Unfortunately some other actors here have derailed the thread by injecting straw man fallacies and accusing the OP of having bias. God forbid anyone question almighty developers on anything. We should be blind, thoughtless sycophants, apparently. 

However, within the last hour or so Aerges themselves posted in the project thread that adverse yaw needs to be tweaked, so at this point the topic is rendered mute until they come through with the next few updates.

Edited August 2, 2022 by Nealius

[sedenion]

Projecting Mirage F1 aerodynamic behavior from the Tomcat is close to non-sens to me. They are hugely different aircraft, hugely different shape and design... Some will scream, but the Mirage F1 rather should be compared to F-16, an underpowerd, non-FBW, F-16.

[Fromthedeep]

1 hour ago, Nealius said:

The first two posts are an unbiased question of if it's accurate or not. Unfortunately some other actors here have derailed the thread by injecting straw man fallacies and accusing the OP of having bias. God forbid anyone question almighty developers on anything. We should be blind, thoughtless sycophants, apparently. 

 

In my experience, people, especially the ones who derive enjoyment out of imaginary street cred the delude themselves with by "mastering" old, non FBW fighters that are rumored to be difficult to handle care very little about how the actual aircraft functions in real life. There's this trend in flight simming (which is likely the result of the simplistic modelling of very old sims) that difficult is more realistic. So if the aircraft is bobbing and weaving all over the sky it's surely going to be more realistic than a well mannered aircraft because the real aircraft must be difficult to fly, even if this doesn't reflect real behaviour. 

[=475FG= Dawger]

1 hour ago, Fromthedeep said:

In my experience, people, especially the ones who derive enjoyment out of imaginary street cred the delude themselves with by "mastering" old, non FBW fighters that are rumored to be difficult to handle care very little about how the actual aircraft functions in real life. There's this trend in flight simming (which is likely the result of the simplistic modelling of very old sims) that difficult is more realistic. So if the aircraft is bobbing and weaving all over the sky it's surely going to be more realistic than a well mannered aircraft because the real aircraft must be difficult to fly, even if this doesn't reflect real behaviour. 

Amen, brother. It is a very strange phenomenon. They seem to glory in behaviors that are obviously ridiculous while denying the existence of physics in other behaviors. 
 

Compensating for something that a therapist could have a field day with. 
 

Personally, I find portions of the F1 yaw behavior feels like swept wing aircraft I have flown while the high speed yaw behavior seems odd. I like the flight model but fully expect it to modify over time into, hopefully, something even better. 

[Pikey]

1 hour ago, Fromthedeep said:

In my experience, people, especially the ones who derive enjoyment out of imaginary street cred the delude themselves with by "mastering" old, non FBW fighters that are rumored to be difficult to handle care very little about how the actual aircraft functions in real life. There's this trend in flight simming (which is likely the result of the simplistic modelling of very old sims) that difficult is more realistic. So if the aircraft is bobbing and weaving all over the sky it's surely going to be more realistic than a well mannered aircraft because the real aircraft must be difficult to fly, even if this doesn't reflect real behaviour. 

I don't think its that, I think it's that older flight models have more inertia and quirks and feel more alive and thus immersive. I am not aware of any quantative data set that you can draw this conclusion from. Was there a poll I missed? We are entitled to opinions but shoudln't offer them as fact.

[AdrianL]

 Adverse yaw behaviour is being adjusted, amongst other things. See 

 

[Nealius]

9 hours ago, sedenion said:

Projecting Mirage F1 aerodynamic behavior from the Tomcat is close to non-sens to me.

You aren't looking past the surface. On the surface the Tomcat and F1 are being compared because they both have slats (the only two such modules in DCS). The essence of the topic was about the aerodynamic effects of the slats, which logically should be the same whether they're on a Tomcat, F1, or an airliner. That effect being proverse yaw. 

Now, what makes the F1 different is that it also has ailerons in addition to the slats, the slats are swiss-cheesed, and the horizontal stab does not control any roll. I don't know how these--or if these--change things, and no one has come forth with any answers. (Except for the news that adverse yaw is going to be tweaked, so obviously there is something off with it).

9 hours ago, Fromthedeep said:

In my experience, people, especially the ones who derive enjoyment out of imaginary street cred the delude themselves with by "mastering" old, non FBW fighters that are rumored to be difficult to handle care very little about how the actual aircraft functions in real life. There's this trend in flight simming (which is likely the result of the simplistic modelling of very old sims) that difficult is more realistic. So if the aircraft is bobbing and weaving all over the sky it's surely going to be more realistic than a well mannered aircraft because the real aircraft must be difficult to fly, even if this doesn't reflect real behaviour.

Agreed. Every hobby has its noisy gatekeepers who want to feel superior to other hobbiests, unfortunately. Add anonymity on the internet and you get a disaster.

 

Edited August 2, 2022 by Nealius

[ARM505]

Er.....why is everybody calling the spoilers slats? Or am I misunderstanding something? Sure, it has slats - but since they're not aerodynamically deployed (like, say, an Me109), they deploy symmetrically, so this isn't a 'roll' issue - you're surely talking about the spoilers, and their assymetric deployment for roll control (a la Tomcat)?

Slats - leading edge devices designed to practically increase the camber of the wing, increase lift, increases drag associated with production of lift.

Spoliers - on the upper surface of the wing, deployed to 'spoil' the airflow, reducing produced lift, as well as increasing drag.

 

Unless I'm confused...

[Lace]

22 minutes ago, ARM505 said:

Spoliers - on the upper surface of the wing, deployed to 'spoil' the airflow, reducing produced lift, as well as increasing drag.

 

Unless I'm confused...

Another point of order here - spoilers do not necessarily increase total drag, they increase parasitic drag, but by virtue of the reduced lift they 'spoil', they reduce induced drag.  generally less lift=less drag.  Spoilers are used to reduce lift without affecting the aircraft speed, otherwise frequent roll inputs would necessitate power changes to correct.

 

[sedenion]

8 hours ago, Nealius said:

You aren't looking past the surface. On the surface the Tomcat and F1 are being compared because they both have slats (the only two such modules in DCS). The essence of the topic was about the aerodynamic effects of the slats, which logically should be the same whether they're on a Tomcat, F1, or an airliner. That effect being proverse yaw.

I assume you mention slats instead of spoilers, anyway, jumbo jets also have spoilers, and slates... One will say they are not used the same way, ok, but the main consideration, before the presence of this or thes control surfaces: The Tomcat is a giant chopping board of almost 30 tons with variable geometry wings, while the Mirage F1 is a small 10 tons dart with short fixed swept wings. It is basicaly like comparing a Hummer with a Renault Fuego...

Edited August 3, 2022 by sedenion

[Tiger-II]

I think some people need to hit the books again and refresh themselves on the various flight controls and their effects.

Right roll = left aileron down, right spoiler up.

Aileron down = increased lift, increased drag. We are turning right, so yaw here is adverse.

Spoiler up = increased drag, loss of lift. Drag may be more or less than the opposite control due to various factors (speed, area, deflection, location). Yaw effect may be variable based on location (inboard will have least yaw effect even if very high drag).

Just because you lose lift doesn't mean the spoiler is neutral for drag. It is still stuck out in the airflow and has an associated turning moment. The only question is whether the forces ultimately balance out to be noticable or not.

Edited August 3, 2022 by Tiger-II

[sedenion]

[Disclaimer, this is a 'My Two Cents' post]

From what I understand about adverse yaw and spoilers (yes that is pretty new for me, but I learn quickly) the Mirage F1, due to its short swept wing configuration (like F-5 or F-16) should not have noticable adverse yaw except at very low speed. It is reasonable to think that Dassault even added spoilers (which is unusual on such wing configuration) to counter the little (but existant) adverse yaw to allow an almost perfect roll behavior. One can even suppose that spoilers are not active at all above a specific speed.
In other words, it may be an error to think that Mirage F1 have spoilers to counter a naturally severe adverse yaw. It may be rather the inverse: Spoilers may be here to "kill" the small amount of adverse yaw that exists at low speed.