Jump to content

Severe adverse yaw: Unique characteristic the F1?


Nealius

Recommended Posts

On 8/3/2022 at 3:10 PM, ARM505 said:

Er.....why is everybody calling the spoilers slats?

Good spot, I feel stupid for not spotting that earlier and it's probably my fault due to lack of coffee and overloaded brain; I said "slats" by mistake and just kept rolling with it 😅

Link to comment
Share on other sites

18 hours ago, Tiger-II said:

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.

 

Spoilers are designed primarily to reduce lift, not increase drag.  That is what air brakes do.  Granted there is some crossover and some applications have a combined function, but as I stated earlier, the majority of your drag is induced as a function of lift.  Less lift=less drag. 

I'm not an F14 expert by any means but I believe their spoilers can work as vertical speed adjusters by function of the DLC to allow for correction on landing by directly dumping lift, without reducing aircraft airspeed - they are not adding drag.


Edited by Lace

Laptop Pilot. Alienware X17, i9 11980HK 5.0GHz, 16GB RTX 3080, 64GB DDR4 3200MHz, NVMe SSD. 2x TM Warthog, Hornet grip, Virpil CM2 & TPR pedals, FSSB-R3, Cougar throttle, Viper pit WIP (XBox360 when traveling). Rift S.

NTTR, SoH, Syria, Sinai, Channel, South Atlantic, CA, Supercarrier, FC3, A-10CII, F-5, F-14, F-15E, F-16, F/A-18, F-86, Harrier, M2000, F1, Viggen, MiG-21, Yak-52, L-39, MB-339, CE2, Gazelle, Ka-50, Mi-8, Mi-24, Huey, Apache, Spitfire, Mossie.  Wishlist: Tornado, Jaguar, Buccaneer, F-117 and F-111.

Link to comment
Share on other sites

6 minutes ago, Lace said:

Spoilers are designed primarily to reduce lift, not increase drag.  That is what air brakes do.  Granted there is some crossover and some applications have a combined function, but as I stated earlier, the majority of your drag is induced as a function of lift.  Less lift=less drag.

I think the equation "Less lift=less drag" is true only for regular wing profile. Indeed, speaking about wing profile, the less difference is between extrados and intrados, the less there are lift and drag. An theoretical absolutly thickless flat wing (which does not exist) would have no lift and no drag.

However, here we are talking about spoilers, which are control surfaces that produce turbulence in the wing extrados, turbulence that indeed break the lift (like a stall) but also induce drag.

But, anyway, I am not fluid mechanics physicist.

Link to comment
Share on other sites

Well... spoilers do increase drag ! 

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.417.9297&rep=rep1&type=pdf

Ailerons tend to create adverse Yaw due to increased drag on the lifting wing
Spoilerons tend to create proverse Yaw due to increasead drag on the dropping wing

Two different system that need to work in pair with the aerodynamic design of the airplane to work.
This becomes even more complex as the airplane evolves through different mach numbers. 

I do think at the moment the adverse Yaw is near acceptable on roll entry. This appears to be one of the caracteristics of the mirage F1, especially at very low speeds.
However on roll exit, the yaw rate is unaceptable high. 

In general my feeling is that there are still some things around the flight model to be looked at (Yaw, tad high speeds, engine overly sensitive...). But considering the quality of the work that the team is known for and the early access status of the plane, I am sure these things are going to be improved, some of which are already being looked at !

  • Like 3
Link to comment
Share on other sites

3 hours ago, pierrewind said:

Spoilerons tend to create proverse Yaw due to increasead drag on the dropping wing

And this is exactly why I started wondering about the F1's adverse yaw, furthermore when comparing with the Tomcat's spoilerons. Lace is correct on the DLC, however that is only ~2 panels of the entire spoileron on each wing, activated symmetrically.

One thing I didn't consider is the wing. The F1 has a high wing as opposed to all the mid-wing and low-wing analog jets we have in DCS. I'm disregarding the Harrier here since it has a stick-rudder interconnect system to deal with adverse yaw. On that note, our Tomcat in DCS has an AFCS system that does not have a stick-rudder interconnect system. 

Anyway, my next question is how does a high wing interact--if at all--with adverse yaw tendencies vs. a mid-wing or low-wing design?


Edited by Nealius
  • Like 2
Link to comment
Share on other sites

3 hours ago, Nealius said:

Anyway, my next question is how does a high wing interact--if at all--with adverse yaw tendencies vs. a mid-wing or low-wing design?

From what I a found, the fact high-wing places the center of lift above the center of gravity tends to increase roll stability (aircraft "want" to stay leveled) which can produce Dutch Roll (result of adverse yaw) in case the roll stability is stronger than the yaw stability.

However, this is a general case for commercial or transport aircraft, which the Mirage F1 is obviously not. This also comes against the statement I quoted in the beginning of this thread, which describe the Mirage F1 as "very stable in yaw" but "unstable in roll".

As general consideration about Dutch Roll (adverse yaw) and wing configuration:

Quote

Aircraft that have wings placed above the center of mass, dihedral wings and swept wings tend to increase the roll restoring force, therefore increase the tendency of the aircraft to initiate a Dutch roll. This is the reason why high-winged aircraft are often slightly anhedral, and swept wing aircraft rely on the operation of the yaw damper.

Source: https://aeronotes.weebly.com/dutch-roll.html


Edited by sedenion
  • Like 2
Link to comment
Share on other sites

Also found an interesting quote about the F-15 (which is also high-wing configuration, with ailerons) adverse (and proverse) yaw, and how it was managed within the hydro-mechanical control system :

Quote

Aileron/Rudder Interconnect (ARI) - Most pilots have excellent instinctive response to pitch and roll, but stupid feet.  When the lateral acceleration has you pasted on the canopy rail, everyone has a pet "memory cue" to rely on, like "step on the hard rudder," "squeeze the ball in the middle," etc.  That may have been okay for "flying the hump," but it just won't do anymore in the fighter business.  We spent an awful lot of time trying to convince Hun and Phantom pilots that nature had intended that any maneuvering at high angles of attack must be done with the feet, but even then it didn't always work.  The ARI "beasty" in the F-15 in an attempt  to cure the "stupid feet syndrome" and put some logic back into "stick back, nose up" and "stick right, roll right"!  The business of stick right-yaw left has made many a fearless fighter pilot pale.  During rolling maneuvers, the F-15 has its share of adverse yaw at positive angles of attack and proverse yaw at negative angles of attack (primarily in the subsonic area, so the hydro-mechanical ARI is cut out during supersonic flight).  Therefore, we simply utilize the roll ratio changer to wash out the yaw producing differential controls at aft or forward stick positions and produce rudder in the direction of the roll at positive (aft stick) angles of attack and against the roll at negative (forward stick) angles of attack.  This is done to keep the adverse yaw from killing the roll rate at positive angles and prevent the proverse yaw from producing extremely high roll rates at negative angle of attack.  Remember, the F-15 has strong positive dihedral effect, which produces strong roll in the direction of yaw at all flight conditions.

https://www.f15sim.com/operation/f15_flight_control_system.htm

  • Like 1
Link to comment
Share on other sites

4 minutes ago, =475FG= Dawger said:

Spoilers are nothing more than flaps. They produce negative lift in the same manner a flap produces positive lift.

An aileron in "upward" position may be compared to "inverted flaps" but not the spoilers. Aerodynamically speaking, flaps "exagerate" (and/or extands, depending design) the wing profile, increasing air flow depression in the wing extrados, increasing lift (and drag by the way). Spoilers act very differently: located on the wing extrados, they are making an obstacle to the air flow, creating turbulance, so kills the lift on that wing section (like a localised stall), and inducts a lot of drag. While flaps are here to increase lift, spoilers are here to create a stall effect (which cannot be reasonably named negative lift).

Link to comment
Share on other sites

Aircraft, such as the F-4, will actually have their aileron/spoiler deflection produce reverse effects at high angles of attack. At high angles of attack, turns in the F-4 are made with the rudder for this reason.

Here is a training film describing this phenomenon in the F-4..

 

 


Edited by Zeagle
  • Like 2

 

 

Link to comment
Share on other sites

43 minutes ago, sedenion said:

An aileron in "upward" position may be compared to "inverted flaps" but not the spoilers. Aerodynamically speaking, flaps "exagerate" (and/or extands, depending design) the wing profile, increasing air flow depression in the wing extrados, increasing lift (and drag by the way). Spoilers act very differently: located on the wing extrados, they are making an obstacle to the air flow, creating turbulance, so kills the lift on that wing section (like a localised stall), and inducts a lot of drag. While flaps are here to increase lift, spoilers are here to create a stall effect (which cannot be reasonably named negative lift).

Flaps increase lift by increasing the angle of incidence of the wing.  It is essentially rotating the wing backwards about the main spar in the lateral plane.

Laptop Pilot. Alienware X17, i9 11980HK 5.0GHz, 16GB RTX 3080, 64GB DDR4 3200MHz, NVMe SSD. 2x TM Warthog, Hornet grip, Virpil CM2 & TPR pedals, FSSB-R3, Cougar throttle, Viper pit WIP (XBox360 when traveling). Rift S.

NTTR, SoH, Syria, Sinai, Channel, South Atlantic, CA, Supercarrier, FC3, A-10CII, F-5, F-14, F-15E, F-16, F/A-18, F-86, Harrier, M2000, F1, Viggen, MiG-21, Yak-52, L-39, MB-339, CE2, Gazelle, Ka-50, Mi-8, Mi-24, Huey, Apache, Spitfire, Mossie.  Wishlist: Tornado, Jaguar, Buccaneer, F-117 and F-111.

Link to comment
Share on other sites

1 hour ago, Lace said:

Flaps increase lift by increasing the angle of incidence of the wing.  It is essentially rotating the wing backwards about the main spar in the lateral plane.

Actually, no. Flaps change wing geometry (for the most common design on fighters, it basicaly increase wing curvature) which allow to increase lift without changing wing incidence (usually the wing extremity still unmodified, this produce a kind of double-properties that reduce stall speed).


Edited by sedenion
Link to comment
Share on other sites

6 hours ago, sedenion said:

An aileron in "upward" position may be compared to "inverted flaps" but not the spoilers. Aerodynamically speaking, flaps "exagerate" (and/or extands, depending design) the wing profile, increasing air flow depression in the wing extrados, increasing lift (and drag by the way). Spoilers act very differently: located on the wing extrados, they are making an obstacle to the air flow, creating turbulance, so kills the lift on that wing section (like a localised stall), and inducts a lot of drag. While flaps are here to increase lift, spoilers are here to create a stall effect (which cannot be reasonably named negative lift).

Any device that changes the camber of the wing modifies its lift.

Flaps increase the existing camber to increase lift which creates parasitic and induced drag.

A "spoiler" is a flap installed to act in the opposite direction. It changes the effective camber of the wing section, simultaneously reducing the "positive" lift and creating lift in the opposite direction.

This is why spoilers are generally installed forward of the trailing edge. This new "lift" force causes a pitch moment and the closer the center of this force is to the center of gravity the more the resulting rotational force is reduced.

Anyone who has ever deployed a spoiler has felt the effect it has on the airplane. It isn't just a "disturbance" in the airflow. It feels just like a flap deployment except for the direction of the pitch change.

You are overthinking the aerodynamics of spoilers.

 

  • Like 1

 

 

 

 

EDsignaturefleet.jpg

Link to comment
Share on other sites

15 hours ago, sedenion said:

From what I a found, the fact high-wing places the center of lift above the center of gravity tends to increase roll stability (aircraft "want" to stay leveled) which can produce Dutch Roll (result of adverse yaw) in case the roll stability is stronger than the yaw stability.

However, this is a general case for commercial or transport aircraft, which the Mirage F1 is obviously not. This also comes against the statement I quoted in the beginning of this thread, which describe the Mirage F1 as "very stable in yaw" but "unstable in roll".

Mirage F1 wing has negative dihedral to maintain high roll rate, like Alpha Jet.

And the spoiler + aileron configuration was quite common on jets from the 1970's...

Mirage fanatic !

I7-7700K/ MSI RTX3080/ RAM 64 Go/ SSD / TM Hornet stick-Virpil WarBRD + Virpil CM3 Throttle + MFG Crosswind + Reverb G2.

Flickr gallery: https://www.flickr.com/gp/71068385@N02/728Hbi

Link to comment
Share on other sites

39 minutes ago, IvanK said:

Is this discussion on mirage F1 Adverse yaw based on nose position looking outside  or just the ball being displaced ?

Both. During gentle turns with ~30 degrees AoB it isn't really noticeable on the nose but the ball is asking to be steppd on a bit. If you're at 350kts and quickly snap into high angles of bank, say 60+ degrees, the adverse yaw throws the nose high. Quickly snapping back to level flight there are yaw oscillations. The same maneuver above 400kts the nose stays perfectly straight, and does not have yaw oscillations when snapping back to level flight. I ignore the ball during violent manuvers since it's often unreliable outside of gentle turns, at least in other aircraft.


Edited by Nealius
Link to comment
Share on other sites

11 minutes ago, sedenion said:

Sorry for the current late reply and the too short previous one... yesterday I wasn't patient enough to carefully read your post, and certainly not to properly reply. It is true that I have a brain and I love to use it, sometimes, a little too much. However It appear to me that your understanding of "spoilers", and especially your first assertion as "inverted flaps that create negative lift" comes from several wrong understandings.
 

  Hide contents

Indeed, in car industry, what is called a "spoiler" is a kind of "reverted" wing whose goal is to push the car to the ground, in order to ensure good adherence at high speed. However, here, we indeed are speaking about "spoiler" in aeronautical context and if you had do some search about "spoilers" in aeronautical context, you probably would had found that it exist several spoiler design (mainly two), but, all have the same intend: killing lift, inducting drag (to slow speed): there is no mention of thing such as "negative lift".

So what is the difference between "negative lift" and "absence of lift" ? The lift is an aerodynamic phenomenon resulting of pressure differential between wing extrados and intrados, created by laminar airflow "speed" difference between intrados and extrados. The key concepts here, are: pressure differential and lamirar airflow. An (regular) aircraft wing produce lift effect with a vector pointing upward (if aircraft is in the proper attitude), what one may call "positive lift".

A non specifically profiled object that travel to the air, like, a baseball ball, a meteorite, or a brick, does not produce any lift but only drag. And specificatly speaking of a ball, it will produce sort of lift with a vector pointing in the opposite direction of its current speed vector, this, because its travel through air actually generate low pressure on its "back" and high pressure on its "front", but there is almost no laminar airflow here, this is drag... And this is even worst for a brick, because the absence of any aerodynamic shape create even more turbulence inducing even more drag. That is what one may call "absence of lift".

Not get back to our spoilers:

And, no. The spoiler is located on the wing extrados, and more specifically, where the low-pressured laminar flow produce the suction effect that produce lift. On gliders, those spoilers are simple "walls" more or less oriented along the wing surface's normal vector, in order, to break the laminar flow. First to breaking the suction effect, which drastically decrease lift, and secondly (but this is a mandatory side effect inducted by the first one) produce turbulence and low pressure back the spoiler, high pressure front of spoiler, in one word: drag. In other words, this transform the concerned portion of wing into a brick, there is no "negative" or "inverted" lift, because there is (almost) no pressure differential of laminar flow anymore. The only vector (in simplistic way) that remain in "opposite direction" (relative to plane fling level in the right direction from the ground) is gravity, not lift.

Is it different mechanism for spoilers design that exists on aircrafts, which are a little more oriented  and differently located ? No. They are simply (in most case) designed inclined to avoid the airflow to brutally hit the structure and produce terrible effects, so they produce only the desired effect which is, first of all, breaking the laminar airflow (ie. lift).

Spoilers are located where engineers need it to produce the desired effect and prevent undesirable effects. The spoilers may be installed more or less close to trailing edge to keep more or less "living" lamiar flow (ie. lift) before the spoiler break it. It is a matter of dosage. In the case the spoiler is close to the trailing edge, when spoilers are deployed the wing continue to produce lift, but, the lift center is translated forward as the back of the wing do not produce lift anymore. This logically results in this "pitch moment" you speak about, which is, then, not induced by a "new lift", but by the lift center moving forward due to lack of lift in back of the wing. The other force that may increase this "pitch moment" is the pressure of airflow against the spoiler surface, which "push" in some manner the wing tail back, but this is not lift, this is drag.

I trust you that deploying spoilers may produce such perception, however, perception and physics are tow different things. Spoilers does not produce lift, they kill lift and produce drag.

 

 

If you would like to believe that placing a flap on top of a wing makes it magically do something different than what it does on the bottom of a wing, more power to you.

Your use of architectural terms for the curves of arches is an interesting choice.

Supersonic airfoils are generally symmetrical. No "Intrados" and "Extrados". 

In any case, its apparent from reading your last post that further discussion will only be frustrating. Enjoy your weekend!

 

 

 

 

EDsignaturefleet.jpg

Link to comment
Share on other sites

7 minutes ago, TLTeo said:

I don't understand why this conversation is still going on when Aerges wrote that they will tune the adverse yaw behavior days ago.

Intead of answering questions or tackling a potential issue (or non-issue) people like to one-up each other on technical knowhow. It's an unfortunate fact of every hobby, it's just worse with highly technical hobbies.

Other than IvanK's question there really hasn't been much of value here since Aerges mentioned the adverse yaw tuning.

  • Like 3
Link to comment
Share on other sites

1 hour ago, =475FG= Dawger said:

If you would like to believe that placing a flap on top of a wing makes it magically do something different than what it does on the bottom of a wing, more power to you.

I deleted my post, but, then. Nothing magic, intents of flaps are (in most common design) to increase wing curvature which increase pressure differential effect of the laminar airflows, increasing suction effect, in two words, increasing lift. What make high-lift flaps increasing lift is not so much the air pushing the flap under the wing than the low pressure and suction effect over the wing (like usual wing profile). both flaps and spoilers are "flat rectangular surfaces" but they do not act the same manner and does not have the same effect.

1 hour ago, =475FG= Dawger said:

Supersonic airfoils are generally symmetrical. No "Intrados" and "Extrados".

And that is a good point for you... indeed, in such case, "killing" lift in one wing side, may create a lift vector pointing in the opposite side, but, not because spoilers act as reversed flaps and rather because spoilers killed the lift on one side.

As I said before, aileron in upward position is more likely to be compared to a "reversed" flap, as the goal is to keep laminar airflow (avoiding drag as much as possible) but varying wing geometry in order to change lift vector direction (or simply magnitude).


Edited by sedenion
Link to comment
Share on other sites

I guess this is somewhat related, but after my first few flights this last 24hrs with the Mirage, I found I am getting a lot of rudder pedal bounce and yaw instability, is this faithful to the real thing ? I do a lot of ground attack type flying so I really notice it when trying to line up for a straffing/bombing run, more simplistic things like lining up for landing are a massive challenge, let alone roll out for take off where I find the plane is generally all over the place compared to everything else except maybe those torquey warbirds and their prop/radial engines ?

Is there a pedal damper maybe ?


Edited by Phantom_Mark
Link to comment
Share on other sites

On 8/6/2022 at 2:07 PM, Nealius said:

Intead of answering questions or tackling a potential issue (or non-issue) people like to one-up each other on technical knowhow. It's an unfortunate fact of every hobby, it's just worse with highly technical hobbies.

 

It's not about one-upping anyone, it's correcting simple misunderstandings - your OP (which you have since edited) claimed adverse yaw was a result of p-factor, made no mention of parasitic or induced drag.  You called spoilers slats.  There are a lot of pilots who also play DCS, and having a basic understanding of aerodynamic principles will help you and improve your flying.  I've read some gross errors of thinking by non-pilot gamers on this forums (one even claimed that the rudder was to correct the difference between course and heading in crosswind conditions!! - imagine a real pilot flying a whole leg with the aircraft uncoordinated, just so the nose was pointed in the 'right' direction!).  It is easy for novices to pick up this stuff and assume it is lore because the post count of the poster implies some level of knowledge or experience (often incorrectly).  Anyone reporting a technical or handling issue should at least have an understanding of that issue in reality.  I learn things on this forum all the time, and am happy to do so, but I am also happy to explain and point out errors of understanding if I see them.  It is not meant to shame anyone, so apologies if you took it that way, but we should all be striving to improve our understanding.  Aerodynamics and aircraft design is a complicated field, and as with many complicated fields, there is often more than one way of achieving the same result.

  • Thanks 5

Laptop Pilot. Alienware X17, i9 11980HK 5.0GHz, 16GB RTX 3080, 64GB DDR4 3200MHz, NVMe SSD. 2x TM Warthog, Hornet grip, Virpil CM2 & TPR pedals, FSSB-R3, Cougar throttle, Viper pit WIP (XBox360 when traveling). Rift S.

NTTR, SoH, Syria, Sinai, Channel, South Atlantic, CA, Supercarrier, FC3, A-10CII, F-5, F-14, F-15E, F-16, F/A-18, F-86, Harrier, M2000, F1, Viggen, MiG-21, Yak-52, L-39, MB-339, CE2, Gazelle, Ka-50, Mi-8, Mi-24, Huey, Apache, Spitfire, Mossie.  Wishlist: Tornado, Jaguar, Buccaneer, F-117 and F-111.

Link to comment
Share on other sites

On 8/9/2022 at 7:39 PM, Lace said:

claimed adverse yaw was a result of p-factor

I did no such thing. This is a straw man fallacy. If you're going to present a counter argument, do not make baseless claims.

On 8/9/2022 at 7:39 PM, Lace said:

You called spoilers slats.

Yes, and I acknowledged that mistake later. Not to mention, it is a very superficial mistake when contextually it was known that we were talking about spoilers. Attacking someone's entire argument because they mixed up a term is invalid. 

Again, I started this thread because the F1 did not fit a set pattern against other modules and I wanted to learn:

1. Is it accurate?

2. If so, why?

THIS WAS CLEARLY STATED IN MY OP.

I AM TIRED OF DEALING WITH THESE STRAW MAN FALLACIES AND AD HOMINEMS.

I OPENED THIS THREAD TO LEARN, AND INSTEAD GET THIS BULL<profanity>.

GOOD DAY.

  • Like 3
Link to comment
Share on other sites

2 hours ago, Nealius said:

<...> AND AD HOMINEMS.

Is this an "ad hominem"?:

image.png

Just curious.

Or is it when somebody disagrees with you?


Edited by Hiob

"Muß ich denn jedes Mal, wenn ich sauge oder saugblase den Schlauchstecker in die Schlauchnut schieben?"

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...