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LLv34_Stafroty
03-13-2005, 03:22 PM
How is cobra so awesome in slow speed stall fighting?? how is it able to pull loops in such slow speed and also turn so tight??

just compare weight to engine power and wing area to mass of it and 109G2. and P39 doesnt even have leading edge slats. cant believe that cobra was that good in real in Stall fighting cos the engine mounted behind pilot, and it would have cause nasty stall in such low speeds in real. where does cobra get that good maneuverability in slow speed and also power to engine to make it able to pull those slow speed loops?? can anyone explain?

LLv34_Stafroty
03-13-2005, 03:22 PM
How is cobra so awesome in slow speed stall fighting?? how is it able to pull loops in such slow speed and also turn so tight??

just compare weight to engine power and wing area to mass of it and 109G2. and P39 doesnt even have leading edge slats. cant believe that cobra was that good in real in Stall fighting cos the engine mounted behind pilot, and it would have cause nasty stall in such low speeds in real. where does cobra get that good maneuverability in slow speed and also power to engine to make it able to pull those slow speed loops?? can anyone explain?

BaldieJr
03-13-2005, 03:28 PM
I've always thought the over-all shape of the 39 is what made it fly so well.

civildog
03-13-2005, 03:30 PM
It's because the Cobra "wants" to go into those kinds of stalls in the first place. Once you understand that, rather than fight against it, you can learn to control those things. Popping out the combat flaps helps, and so does learning to ride the edge of that stall. It's a pretty quirky thing for a plane to do, but that' one of the reasons we Irondog drivers love them. They are a challenge.

They are underpowered, though. They don't climb very fast, though they can sustain a climb at some speed better than a lot of planes - it's just shallower. And they were a good, though not excellent, turn fighter down low in real life. That's one of the reasons they did so well in Russia. The US and British didn't want them because they were not very good at high-altitude fighting, which is what those countries were looking for.

And the big, honking cannon is just beautiful.

civildog
03-13-2005, 03:33 PM
See, the thing to remember is this: it's not that the Cobra is "good" at low speed stall turning, it's BECAUSE the engine is behind the pilot that it is so unstable in those kind of trns that a good pilot with one can use that inherent instability to make tighter turns and fast rolls at low speed.

But it's hair raising because if you blow it it's flat-spin city for you!

LLv34_Stafroty
03-13-2005, 03:36 PM
somehow, i dont get the idea from those explanations. http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif try harder to convince me. its still againt my thoughs of law of physics

civildog
03-13-2005, 03:49 PM
How is it against the laws of physics? Planes are inherently stable in flight. The Cobra, as you correctly pointed out, should be inherently unstable in a low speed turn because the center of gravity is well behind the wings instead of over them.

OK, that means that as long as you don't let your airspeed drop too much, the plane's instability will help you roll it into a turn (because it wants to roll) to make the turn faster.

Now if you drop your speed too much, even with flaps out, the beast will pitch itself end over end in a tumbling or flat spin. That's because you didn't treat it gently enough. The real pilots were always cautioned that it was a plane you had to treat gently. You have to "think" it into turns. Not just yank n' bank or it will fall outside that narrow envelope of stability and tumble.

It has personality, more so than any other plane in the game. If you read some accounts by the real pilots of the plane you'll hear the same thing I'm telling you. It was an uncompromising, mean, murder bird unless you survived in it long enough to learn it's quirks and use them to your advantage.

A most excellent memoir on the subject is "Nanette" by Edward Park, an editor for Smithsonian magazine. He flew the Cobra in New Guinea and describes beautifully the personality of the plane. His description of the first time he flew one in just a routine check out flight is hair-raising and sounds exactly like the way it flies in the game.

BaldieJr
03-13-2005, 04:26 PM
Think about the small amounts of force needed to upset a balanced object.

The 109 is fighting inertia during a stall-fight because its CoG is so far forward.

The 39's never fighting inertia when its on the edge of a stall because the engine balances the plane.

The over-all design has to be considered with the 39 because it is so radicly different.

SpartanHoplite
03-13-2005, 04:27 PM
Its the plane AND the pilot, of course!

Hows that for a typical glib answer? http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

SH

JR_Greenhorn
03-13-2005, 10:02 PM
A good example of unstable equilibrium I've heard in a lot of physics classes is balancing a pencil on its eraser end. You can make it balance (equilibrium), but the pencil topples at the slightest disturbance.

Now try to balance the pencil in the open palm of your hand. As long as you move (accelerate) your hand to correct for its tendency to fall, it is fairly easy to balance.

Now think of the P-39. At slow speeds, it "balances" on the forces acting on it (lift, drag, weight, prop thrust, etc.). A small change in magnitude or direction of any of those forces will case the P-39 to tumble. If the pilot offsets the imbalanced force with finesse on the controls, he can mantain an unsteady equilibrium like you can by balancing the pencil.

Unstable equilibrium can also be attained momentarily, such as when the plane makes a hard turn at low airspeed. When the pilot straightens the turn into forward flight, another unstable equilibrium is immediately attained.

JR_Greenhorn
03-13-2005, 10:11 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by LLv34_Stafroty:
just compare weight to engine power and wing area to mass of it and 109G2. and P39 doesnt even have leading edge slats. <HR></BLOCKQUOTE>Be careful making plane comparisons based solely on power loading and wing loading. While you are on the right track to consider the effect of leading edge slats, there are so many other factors to consider before drawing a conclusion as you have.

Other things to consider that will have marked effects on the performance of a plane are the airfoil type, the layout of the plane (in this example, how the center of mass compares to the aerodynamic center), as well as the size of the control surfaces. The design of the wingtips have an effect on how the plane behaves in turns and on the edge of a stall. Propellor diameter and design have an effect on how the engine converts shaft power into thrust.

At best, comparing planes based on power loading and wing loading will give you a general idea of performance. Don't be surprized if the plane's performance envalope exceedes or greatly falls short of what its power and wing loading suggest.

VW-IceFire
03-13-2005, 10:18 PM
Case in point: The F-16 was designed intentionally to be a very unstable design. The computer keeps the plane stable but when the pilot wants to make a manuver, the instability of the airframe enhances the manuverability of the aircraft.

Planes like the MiG-29 and Su-27 are also designed with inherent instability.

During WWII, it was generally the idea that planes were designed to be as stable as possible. But you have examples like the FW190 and the P-39 which are a little less stable in some areas which greatly enhances manuverability in some areas.

Comment on slow speed loops: Its possible in all but a very small number of planes in this game.

p1ngu666
03-13-2005, 10:31 PM
ww1 fighters are unstable, think the camel is as unstable as it got

imo the 190 is not that unstable, but it has a higher "saftey" speed. b25 is also pretty deadly in the stall http://forums.ubi.com/images/smilies/16x16_smiley-sad.gif

p39 gets tons of lift from flaps, and u gotta ease it into turns and loops

SabreF-86
03-14-2005, 03:16 AM
Civildog, I gotta correct you on that idea of the CG being behind the wing. Can't be, as the plane would never even get off the ground that way. The CG may be farther back on the wing chord than normal, but it has to be in the right envelope. Eg. the Clark Y airfoil was happy with a CG at 33% of the chord more or less. Too far back, and the aircraft will pitch up and stall with no chance of recovery. Off the wing chord completely and its no chance at all.

Sabre

MZ6
03-14-2005, 10:22 AM
Imagine standing on a spinning platform and holding a weight in your hand. If you hold it out, you will spin more slowly, hold it in towards your self and you will spin more quickly. I remember this experiment from school. Also, the best place for an engine in a race car is the middle for the very same reason. When the first mid engine F1 car was made all the front engine cars became obsolete almost overnight.

TgD Thunderbolt56
03-14-2005, 10:47 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by p1ngu666:

p39 gets tons of lift from flaps, and u gotta ease it into turns and loops <HR></BLOCKQUOTE>



BINGO! The prodigious use of flaps (all the way down to landing flaps!) and prop-pitch, in conjunction with the CoG, Airfoil design decent elevator response, etc,...allow for "on-the-edge" maneuvers that only lighter airplanes with better thrust-to-weight ratios should be able to accomplish.

Add to this the fact that in this sim, people ride that edge EVERY SINGLE TIME they get in the cockpit because they know they can just hit refly and you see many things that you wouldn't ever hear about IRL because many upheld the doctrine that they didn't want to get too close to that envelope because of the inherent danger.


TB

TX-EcoDragon
03-14-2005, 12:56 PM
Yep. . refly does wonders for the things people try in sim aircraft. Also keep in mind that the 39 has a very nice low speed roll response, that makes it more maneuverable without even needing to pull G, so a roll reversal will cause you to have to place mroe emphasis on the elevator pull to play catch up. . . unless they are in a 190. . . but if they are in a 190 they arent going to pull with you anyway.

LLv34_Stafroty
03-14-2005, 05:13 PM
using flaps also with 109, and ride in the edge, also, rads closed, and still uding slats which P39 doenst have!

P39 would rise nose quickly up but continuous turn is other thing, as is loop. i find it much harder to make loops dopwn in deck with 109 as with P39N1. just take some 250KMH and make loop from zero alt. easy with P39. try same with 109G2. both with 25% fuel.

FI_Willie
03-14-2005, 07:01 PM
Agile A/C are inherently unstable. A Cessna 150 isn't very agile but it is stable. Most WWII fighters were designed to operate at the ragged edge of stability. They meant to be FLOWN not herded around.

The guys that flew them were highly trained and taught how to operate that plane in its' worst regimes. THey didn't have the "refly" option if they really FUBARed. THe "washout " rate was high and a lot of times it ended in notification of the next of kin.

One of the reasons insurance is SO exorbitant for warbirds to day is that there is really no way to learn those planes as they were taught to flown in WWII. The rich Doctors and lawyers have a bad habit of buying a P-51 or some such to show off in and then screwing it into the mud when it gets stupid on them. All they've ever done is flown straight and level with maybe a short course of training "in type" rather than months of HARD training by guys that knew what those beasts were capable of. **** waste of an irreplaceable plane.

They were not good "hands off" planes.

AS for how good or bad the actual flight models are, I have no idea. The closest thing to a WWII fighter I've ever been blessed to fly is a Stearman and that is a LONG ways from a fighter.

I've flown a Pitt's S-2 and several clipped wing cubs and a clipped wing T-cart. The clipped wings fly pretty much the same as the long wing stuff but they react faster to certain moves. ( roll) I've flown a lot of "spam can" stuff (Cessna's and the like). They were tame. Even the 150 "Aerobat" was pretty much NOT an aerobatic bird..

Most of the handling characteristics good or bad, come from the location of the center of gravity of the plane rather than lift coefficients and power to weight ratios.

Luring2004
03-15-2005, 09:24 AM
As far as I´ve read, the US pilots in the Pacific, hated the "Pig" P-39, US gladly handled them over to Russia via Lend Lease.

Platypus_1.JaVA
03-15-2005, 09:27 AM
Haaah, ya should've flown it in Il-2 1.0 http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

SeaNorris
03-15-2005, 09:37 AM
I love the P-39 and P-63


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