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Cmte. Carvalho
10-13-2004, 06:12 PM
...a little problem trying to keep the aircraft in a upside-down condition? It's very easy to keep the wings leveled in normal flight but during in the inverted position, where at least most aircrafts would have the same hability, it's actualy being very hard in the sim... I can imagine how much dificulty the demonstration squads are having with that, especially during formation maneveurs... Does Anybody knows if a correction is being studied for that?

Thanks.

Cmte. Carvalho
10-13-2004, 06:12 PM
...a little problem trying to keep the aircraft in a upside-down condition? It's very easy to keep the wings leveled in normal flight but during in the inverted position, where at least most aircrafts would have the same hability, it's actualy being very hard in the sim... I can imagine how much dificulty the demonstration squads are having with that, especially during formation maneveurs... Does Anybody knows if a correction is being studied for that?

Thanks.

Chuck_Older
10-13-2004, 06:20 PM
I find it a tad difficult, but then again, these aircraft, in many cases, were prohibited from flying inverted for any length of time

Cmte. Carvalho
10-13-2004, 06:28 PM
Really?? Give me some examples (if possible with some evidence)...

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Chuck_Older:
I find it a tad difficult, but then again, these aircraft, in many cases, were prohibited from flying inverted for any length of time <HR></BLOCKQUOTE>

VW-IceFire
10-13-2004, 06:35 PM
Mmmm flying upside down is a whole other ballgame. I believe in-general the wings are designed to work in the rightside up way...when you go upside down...the lift is now directing the nose of the aircraft down instead of up. This means your helping gravity with the wing.

Correct me if I'm wrong.

As for prohibited for flying upside down.

Early Spitfires used gravity to feed the engine. This is why negative G's were prohibitive to the engines operation causing stall outs. True of the Hurricane Mk I, I-16, and other types.

The P-38 training film (Zenos Warbirds I believe) mentions that oil will not be properly getting to the engine components while flying inverted. It was suggested that flying upside down be done for no longer than 7 seconds.

There are other examples but I can't remember the details. In general, none of these aircraft were designed to fly for extended periods like that. Aerobatics aircraft are entirely different beasts.

sunflower1
10-13-2004, 06:39 PM
This one I can field with confidence.

When you're inverted the wing's dihedral angle works against you, in the way it works for you when upright.

I've flown about 100 different model aircraft, ones with flat wings in the low wing position basically can't tell if they are inverted or not, the amount of spiral instability added by being inverted is small.

Add a tiny amount of dihedral and staying inverted is a chore. Nearly all the planes we fly in this game have a pretty healthy amount of dihedral, they should be unstable about the roll axis while inverted. I'll make an educated guess that the weight of the fuselage hanging below the wing while inverted is a second order effect versus the aerodynamic effect of dihedral.

If Oleg "fixes" this you'll have an X-wing fighter on your hands. Honest.

The only full scale a/c I've had upside down needed to be fooled into thinking they were rightside up- which doesn't last long. I think there are some pilots around here that fly full scale who'll say the same thing about them as I have found with models and you've found with the game.

Cmte. Carvalho
10-13-2004, 06:43 PM
Hum... Ok, i made some research and some aircraft really where unadviced to do inverted flight especially due to engine characteristics but, the question i bought it's not exactly that... In the sim when i put an airplane upside down i just cannot make my wings leveled, even the airplanes that have no restrictions to fly in that condition... Well, i never flew a real airplane before but i believe that, at least most of them (especially the aerobatics and fighters, of course) can level their wings with no problem...

sunflower1
10-13-2004, 06:46 PM
The kind of airfoil and the angles of the wing and tailplane to the datum line are the biggies on how a plane acts in pitch while inverted. With a symmetrical airfoil (not found on any of our a/c, I bet) and 0/0 angles, the plane doesn't care which way is up. Just re-trim.

The reason it takes most of the stick's forward travel to maintain level flight is that the airfoils aren't symmetrical and full scale a/c nearly always have some angle of decalage- the wing is positively inclined to the datum line and to the tailplane. This balances the force of the CG lying ahead of the center of lift. When you roll inverted, this relationship is the same, but both forces now point towards dirt. Down you go.

What I've found is that level inverted flight gives me a little reds. Its been a long time since I've hung upside down and I'm not willing to test this one- I'll just go with Oleg's modelling- but is this right?

LStarosta
10-13-2004, 06:47 PM
My dad used to do his entire traffic patterns inverted, minus the landings, of course.

Cmte. Carvalho
10-13-2004, 06:52 PM
Funny LStarosta... Guys, maybe some of you didn't understood me well... Let me try to explain better... The problem is not with climb movements (nose up/down) but with roll moviments... It's almost impossible to keep the wings straight in relation to the horizon (not about alpha, but about roll) in the sim actually... That's it...

Cmte. Carvalho
10-13-2004, 06:54 PM
What your dad used to fly in these funny situations LStarosta?

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by LStarosta:
My dad used to do his entire traffic patterns inverted, minus the landings, of course. <HR></BLOCKQUOTE>

sunflower1
10-13-2004, 06:59 PM
That's how everything I've ever flown has acted, though, if it had any dihedral at all.

Look at an Extra- the wing is flat, flat, flat. That plane also has its mass balanced above and below the fuselage, it is a perfect mid-wing. It can't tell if its rightside up or not. That plane is probably a breeze to fly upside down.

The stability your plane has while upright is caused mostly by the dihedral in the wing. Very, very few low wing monoplanes were made without dihedral. A Cessna would be a great example of a flat wing, or nearly flat, but that design gets its stability by suspending the a/c below the wing. Its still going to be squirelly
when inverted.

Jungmann
10-13-2004, 07:09 PM
Dihedral ain't it, IMHO. Works the same aerodynamically V up or V down. Plenty of anti-hedral designs that flew--B-47 comes to mind (at least at low speed, until the wings flexed).


The biggest bar to inverted flight for airplanes with standard airfoils, NACA type (round on top, flat underneath) is that with the flat side up and at an angle of attack to the relative wind, you don't get as much lift. So in RL, you have to add down elevator (up pitch) to keep the nose up. That makes for messy trim and squirlley controls in general, with all that elevator deflection.

Competition pilots may post and add that modern aerobatic planes like the Sukhoi and the Extra have symetrical foils--curved on top and bottom--for better performance in inverted maneuvers.

Old 853N wouldn't stay inverted level for very long. Started heading downhill pretty fast.

sunflower1
10-13-2004, 07:14 PM
Jungmann, take a second to map it out on paper. The left wing of an inverted plane rises, as it does it gets closer to parallel with the ground, producing more lift. Right? At vertical it would produce none...

The right wing drops, producing less lift as it get closer to vertical. Right?

This situation doesn't naturally stabilize.

sunflower1
10-13-2004, 07:15 PM
Until the a/c has rolled itself rightside up, which is what dihedral is for.

sunflower1
10-13-2004, 07:20 PM
I'm sorry, I don't mean to come off like an expert, but this is first chapter stuff in any flight training manual. Its dihedral. There are other forces and effects involved, but if inverted roll stability is the issue, dihedral is the culprit. While I have a hard time contributing to the computer talk around here, I do know my way around basic flight stuff though and thought I'd try to explain why these a/c feel so "right." Modelling dihedral's inverted effects is a difference between a cheesy game and one that purports to simulate something.

TX-EcoDragon
10-13-2004, 07:22 PM
Sunflower is correct, and he does understand your question. What he is saying the " v " shape to the wing when viewed from front or back gives the aircraft stability in roll when upright. . . when inverted that shape is now more like " ^ " and this will lead to instability when inverted.

So the aircraft should be less stable when inverted. That said, the way that the sim models dihedral effects is not perfect, and the aircraft do tend to have less stability when at the perfectly inverted attitude than they should, you will also notice that rolling only a few degrees in either direction will give you just a little more stability. . . this is an artifact of the way that the sim is coded. In specially designed aerobatic aircraft you will see not only a semi-symetrical, or fully symetrical airfoil, but also very little, or no dihedral, the wing will not be V shaped instead if will look more like this --o-- this will make the aircraft very responsive to roll inputs, and not stable in roll at all in any attitude, but in this case upright and inverted will be the same to the aircraft.

sunflower1
10-13-2004, 07:34 PM
And we all learn a trick!

S!

TX-EcoDragon
10-13-2004, 07:43 PM
see how the Raven's wing (the wing is a Zivko Edge wing) is flat when upright and compare it to the p-51 in the back that has that upward angle to the wings:

http://www.txsquadron.com/uploaded/TX-EcoDragon/114-1459.jpg

This makes the Raven happy as can be when inverted, the wing is still flat:

http://www.txsquadron.com/uploaded/TX-EcoDragon/ribbon%20small.jpg

compared to the upward tilt to the wings of the P-40 shown here:

http://www.pacific-fighters.com/ss/P-40_formation%2001.jpg

TX-EcoDragon
10-13-2004, 07:48 PM
The airfoil and incidence of the wing will not change roll stability when inverted so much as it will change the pitch attitude required to maintain level flight, as well as the amount of forward stick and elevator travel required on the stick to maintain inverted. even flat bottom airfoils will maintain inverted flight, however an extreme nose high attitude is required which requires significant elevator authority as well as sufficient flying speed.

Cmte. Carvalho
10-13-2004, 07:58 PM
Hey, i never said that IL-2 was a game or unrealistic due to that... In fact i apreciate it but due to some experience that i also have as a aircraft enthusiast and lover overall, i just tought that something were wrong with upside-down flight cachteristics in the SIM. And i know what is dihedral... Tell me one thing please: if that is what really matter in wing stabilization during inverted situations, why it's also hard to keep the YP-80 inverted in the simulator? It's wings looks flat to me...

Thanks.

Lemky
10-13-2004, 08:01 PM
When upside down just use your rudders to keep your self level.The rudder will bring the dropping wing up.Try it my Friend

TX-EcoDragon
10-13-2004, 08:08 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Cmte. Carvalho:
Hey, i never said that IL-2 was a game or unrealistic due to that... In fact i apreciate it but due to some experience that i also have as a aircraft enthusiast and lover overall, i just tought that something were wrong with upside-down flight cachteristics in the SIM. And i know what is dihedral... Tell me one thing please: if that is what really matter in wing stabilization during inverted situations, why it's also hard to keep the YP-80 inverted in the simulator? It's wings looks flat to me...

Thanks. <HR></BLOCKQUOTE>

First of all, in the game, the visual model and the FM are not linked, and the ability of the sim designers to change dihedral effect is limited. This means that what you might expect from the P-80 given its relatively flat wing, and what you get in game are not the same. Regarding that I will restate what I said in my first post ". . .the way that the sim models dihedral effects is not perfect, and the aircraft do tend to have less stability when at the perfectly inverted attitude than they should, you will also notice that rolling only a few degrees in either direction will give you just a little more stability. . . this is an artifact of the way that the sim is coded" and it is not an example of how the actual aircraft behaves in this particular situation. Also, this has improved quite a lot since the origianal version of IL-2. . . maybe with BOB we will see a different type of dihedral effect modeling.

Cmte. Carvalho
10-13-2004, 08:15 PM
Unfortunatelly i realized that TX-EcoDragon... So, there are plans to correct this at least in flatwinged airplanes?

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by TX-EcoDragon:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Cmte. Carvalho:
Hey, i never said that IL-2 was a game or unrealistic due to that... In fact i apreciate it but due to some experience that i also have as a aircraft enthusiast and lover overall, i just tought that something were wrong with upside-down flight cachteristics in the SIM. And i know what is dihedral... Tell me one thing please: if that is what really matter in wing stabilization during inverted situations, why it's also hard to keep the YP-80 inverted in the simulator? It's wings looks flat to me...

Thanks. <HR></BLOCKQUOTE>

First of all, in the game, the visual model and the FM are not linked, and the ability of the sim designers to change dihedral effect is limited. This means that what you might expect from the P-80 given its relatively flat wing, and what you get in game are not the same. Regarding that I will restate what I said in my first post ". . .the way that the sim models dihedral effects is not perfect, and the aircraft do tend to have less stability when at the perfectly inverted attitude than they should, you will also notice that rolling only a few degrees in either direction will give you just a little more stability. . . this is an artifact of the way that the sim is coded." <HR></BLOCKQUOTE>

TX-EcoDragon
10-13-2004, 08:42 PM
Well, I am not saying that things will change, I am just saying that there is room for improvement, and that I will keep my hope that improvement will be made over time, as has happened over the evolution of the IL-2/FB sim line in the past. It doesn't hurt to point these things out, though I trust that Oleg is aware that the FM could be improved, and that he will do it as he is able.

Lemky
10-13-2004, 08:53 PM
Hi may be you could tell me what the wing dihedral does.I allways was under the understanding that it holds the layer of air longer to lower the stall on the wing.

heywooood
10-13-2004, 09:26 PM
lift is generated at 90 deg. angle to the top surface of the wing so that if the wing has dihedral (angling the lift force inward toward the fuselage) it creates equal pressure against the fuselage from both sides thus making for good lateral (anti-roll) stability in the upright attitude. In inverted attitude with a positive dihedral all of this stability is lost as lift is now provided by the wings' lower surface which, on a warbird, is not a symmetrical airfoil shape as that adds an undesirable drag coefficient.

So now you have less lift and far less air pressure being generated against the fuselage even at high speeds.

Much less stable in a low wing warbird than a dedicated aerobatic airframe in sustained inverted flight regimes.

TX-EcoDragon
10-14-2004, 11:38 AM
Lemky see these links, but in summary it causes the low wing to generate a greater amount of lift than the higher wing, which results in a tendency towards rolling the aircraft back towards wings level (the fuselage may be above or below the wing with the same effect, however the need to augment stability in this manner is reduced by the addition of the pendulum effect in the high wing configuration so the amount of dihedral is less for an equal measure of stability):

http://142.26.194.131/aerodynamics1/Stability/Page5.html


http://www.centennialofflight.gov/essay/Theories_of_Flight/Stability_II/TH27G8.htm


Also, I might add that what you are describing sounds like either leading edge cuffs/slats, or vortex generators.

WTE_Galway
10-14-2004, 06:07 PM
its more than dihedral .. the entire aircraft is designed for normal rather than inverted flight

- the wing section is usually designed for normal flight .. this means inverted you get less lift and thus must fly nose up causing lift vs CoG issues

- an aircraft with a low centre of gravity suddenly acquires a high one also effecting stability

- flaps if engaged are going to work incorrectly when inverted (duh!)

- the tail plane and vertical stabiliser also can function oddly when inverted

LStarosta
10-14-2004, 09:06 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Cmte. Carvalho:
What your dad used to fly in these funny situations LStarosta?

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by LStarosta:
My dad used to do his entire traffic patterns inverted, minus the landings, of course. <HR></BLOCKQUOTE> <HR></BLOCKQUOTE>


He flew Zlins.

ELEM
10-15-2004, 02:02 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Cmte. Carvalho:
Hey, i never said that IL-2 was a game or unrealistic due to that... In fact i apreciate it but due to some experience that i also have as a aircraft enthusiast and lover overall, i just tought that something were wrong with upside-down flight cachteristics in the SIM. And i know what is dihedral... Tell me one thing please: if that is what really matter in wing stabilization during inverted situations, why it's also hard to keep the YP-80 inverted in the simulator? It's wings looks flat to me...

Thanks. <HR></BLOCKQUOTE>

You did actually say in your initial post "Does Anybody knows if a correction is being studied for that?" Which implies you think the FM is wrong in the ways you describe. Which in fact it's not. Also the YP-80 does have dihedral. You will notice that MOST pure aerobatic a/c have mid mounted wings, zero dihedral and almost zero wing incidence. This means they will handle almost the same whether upright or inverted.

http://img.photobucket.com/albums/v107/Elem_Klimov/LOCKHEED_P80B_SHOOTING_STAR_1-b.jpg