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#161
02-10-2011, 10:58 PM
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 Most people don't seem to be able to articulate what they are seeing. So I'll give it a try. It took me a while to notice but eventually I did. Now that I've noticed... I can tell that the Spitfire is definitely a slightly more challenging ride than before. Before it felt a bit like it was on rails in some cases. Now it does have some "extra character to it". I can't say if it's right, wrong or different. So far the best way for me to test to see the difference is to snap roll 90 degrees left and right and then return to level flight. It seems the aileron movements causes the extra yaw. I'm fairly certain this is called adverse yaw. It is slightly more severe than on many other types (by my approximation) although I can also list several types that have it more extreme than the Spitfire as well. I do know that stability changed between the different Spitfire models and the redesigned tail for the later IX models represented an attempt at correcting some stability issues introduced by the Merlin 60 series installed up front which changed the length, weight distribution and relative stability of the model. I don't have the numbers... just the general details so unfortunately I cannot be more specific. The revised modeling does seem to be across the board but it may be worthwhile to double check Mark V versus early Mark IX versus late IX (and VIII) just to be certain that values are what they should be? Just some thoughts. EDIT: Those of you having more difficulties with this may want to adjust their joystick curves to slightly reduce the sensitivity. Particularly on the rudder. That should help... along with a proper rudder coordination technique to work with excess yaw. Particularly during gunnery.
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#163
02-11-2011, 01:18 AM
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As a P-51 flyer myself I'm also gonna weigh in, prior to 4.10 as everyone knows the P-51 had some yaw instability problems which made it kind of infamous for spinning and wagging its nose back and forth uncontrollably during banking (Applying the normal rudder during bank didn't make a coordinated turn as it should have), and this upset the aim (so everyone was bitching about the .50's instead lol). This was all rectified when the length bug was corrected and its now quite a sweet ride again.
Now the new spitfire FM does not seem as unstable as the old P-51 IMHO in terms of 'wagging' oscillations (I just took out a few la-7s and when the elevator was trimmed correctly it was a nice ride), I think it's mostly an issue of what speed the trim is set for.
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#164
02-11-2011, 01:38 AM
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Adverse yaw is encountered in all aircraft, but maybe the Spitfire's famous wing is partially to blame in this case? From the wiki: Quote:
Why do we care? Well, because more lift means a bigger forward/backward component in the diagram, which means more adverse yaw. If the Spitfire's wing is capable of higher lift than other aircraft (for a given airspeed range, conditions, etc etc) then it will also be prone to more adverse yaw, which means you need to use the rudder more or have oscillations when it goes back to neutral behavior. I don't know exactly how the Spit's wing compares to other aircraft, so if anyone could shed some light maybe we could track down if this is the cause of the instability. In the case that the Spit wing is better at producing lift then incurring extra instability during rolls would be accurate. There's no such thing as a free lunch in physics  On a more humorous note Quote:
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#165
02-11-2011, 05:02 AM
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The Spitfire has a CoG that's somewhat rearward. A bit more than on most other planes. This means that any force input will give you a larger effect - be it control input, adverse yaw or even gyroscopic effects. It also gives the plane a considerable nose up tendency.
That's all there is to it.
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#166
02-11-2011, 09:06 AM
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The spitfire was very light on the controls, especially the elevator.
Also the tail was very light when taxiing and during takeoff. You can read it here. http://www.paulsquires.co.uk/spitfire.html http://www.vintagewings.ca/VintageNe...ke-Potter.aspx I like this sentence from the vintagewings article: And, like all fighters of this era, you need your two feet as well as your hands to fly or she will skid and slip all over the sky. Last edited by ImpalerNL; 02-11-2011 at 09:45 AM.
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#167
02-11-2011, 02:01 PM
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You could look at the adverse yaw as another not-commanded disturbance of direction of the plane's axis, away from the line of flight. The vertical tail ll react to the adverse yaw with a correcting moment in the opposite direction at once, but the value of that moment depends on the 'area' and 'moment arm length/distance to CG' which are bound to have some kind of virtual representation in the planes game FM. This 4.10 change feels similar to 4.09 spit which lost half the vertical tail area (it means the rudder, that makes this a difficult analogy) We didn't mention here the most important stabillity axis- the pitch-axis. Reducing the sensitivity of the controls must end somewhere, or you wont reach the full throw of the rudder in the extreme position. From this somewhere, stick output is bound to rise ever steeper, making holding the plane on the stall limit a very shaky matter; half a millimeter more and you overdrawn it. Furthermore, exponential control output is not a simulated feature, because it exists on no plane. It is only a way of limiting the plane's twitching in level flight because of the potentiometer 'noise'. So you do not need this very counterproductive 'pott-stick/exponential output' duo, if you get a Hall-sensor (or any other contactless) noise-less stick. It doesnt have to be expensive like Saitek X series; Thrustmaster T16000 m is quite moderately priced. Once you get rid of the potts and their completely unnatural input curves, you ll see at once how much you suffered actually , and never want to go back. As for the trimming-after making the output table linear (10,20,30..100) I did not feel a special need to trim any more, cause the plane could be held rather steady in a cruise, with a small stick inclination and force. Only exception I can think of right now was the Ki43, which needs a strong downward trim at lowish speeds already, and this 4.10 Spit, which behaves similar. If rather energy-conscious, you can continue using trim, of course.I am repeating this, becasue this info still seems to be largely unknown. Making the stick output curve even more non-linear is the last thing one should do. I am not sure if the rudder coordination ll help you so much while shooting from a less stable plane. What would help is slow and gradual applying of the controls. For that, the oponent has to be cooperative enough to fly steadily and not too fast, of course. Last edited by PE_Tihi; 02-12-2011 at 08:14 AM.
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#168
02-11-2011, 02:05 PM
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#169
02-11-2011, 05:12 PM
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How much tho is another question entirely....
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#170
02-11-2011, 05:46 PM
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The Spitfire had differential Frise ailerons- that means most effective means available to counter the adverse jaw. Frise has a price of increasing the rolling plane's drag, but Mitchell obviously accepted this trade-off knowing that a fighter has to hit something, too. Spitfire wings were an excellent and beautiful design, but that ellipse is not such a magic as it's fame implies. It was a quite thin profile, large area and low wing loading that did much more for the efficiency of it's wing's then their elegant elliptical planform, which probably did more for the Spit's high unit price. Twisting the tips of a conventional tapered wing-planform brings it very near to the optimal elliptical lift-distribution*, at a fraction of the cost of a wing with an actually elliptic geometry. This goes even for the squared-off wingtip planforms, which do not spoil the lift distribution much additionaly, either (Bf109, P51). Mitchell knew that very well, for sure, but went over to the elliptical wing after additional guns have been demanded - and he had no room for them in the original tapered wing. Moreover, the ellipse solved the structural problems of a thin profile and made his already excellent wing concept a couple of additional percent better aerodynamically; I imagine nobody asked much about the unit price at that time, anyway. Rarely used for the reasons mentioned, the elegant ellipse of the wings made the Spit recognizably different from the other planes, and the chance to create a bit of magic around this has not been missed in a wartime, of course. This famed ellipse of the Spitfire's wing found a way into the British hearts so deep, that redesigning the Typhoon into Tempest, Camm took the semi-elliptical planform partly to inspire confidence of his customers in the ministry, I suspect. Nothing occurs to me as a possible cause for any increased adverse yaw in the spit's wing aerodynamic. Like almost all fighters, Spit has had a lean stability for the sake of being more manoeuverable. Many pylon racers of the period were much more radical in that sense. Polikarpov designs, especialy the I16 had quite narrow stabillity margins, almost like racers. Adverse yaw is only one of the disturbances (like gusts, gyroscopic effects, etc) which the stabilizing surfaces have to overcome, and the gyroscopic precession after a pedal has been kicked should be more noticeable on any prop plane than the adverse yaw. Real Spit probably felt the adverse yaw properly only when rolling quite fast. So, you barking under a wrong tree, my lads * When the lift-force distribution along the wingspan has a shape of an semi-ellipse, it s an optimal case, with the lowest induced drag, i.e highest lift-producing efficiency. Last edited by PE_Tihi; 02-19-2011 at 07:49 AM.
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Linear Mode
