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| IL-2 Sturmovik The famous combat flight simulator. |
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#1
07-09-2010, 04:17 PM
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Just for reference, my summing up made sense to me when I posted it, but JtD's explanation makes much more sense while contradicting my statement.
As such the only explanation I can think of for why reducing throttle could increase turn rate is that it could bring speed down to an aircraft's optimum turn speed, thus producing an increased turn rate. In the case of the Spitfire I tried this with, this is useful, because the Spitfire can maintain this turn rate at this throttle setting without the speed dropping (I would put this down to the Spitfire's high power to weight ratio and low wing loading). The Fw190 can't maintain this (High power to weight ratio but high wing loading), but lowering the speed can produce an immediate and noticeable improvement in turn rate, hence the impression that down-throttling boosts the Fw190's turn rate. If the opponent was something like a P51, which is less manoeuvrable horizontally (and vertically) than a Spitfire, then you might well be able to out turn it. AndyJWest, I noticed your description of trying to turn the Fw190 at reduced throttle involved the words "on the edge of the stall", and when I tried this myself it resulted in immediate and massive speed loss. You need to be turning somewhat outside the stall zone to avoid this and make it possible to turn at reduced throttle. 
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#2
07-09-2010, 04:35 PM
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Wow this thread lost me with all the silly rantings and notions of a person that doesn't understand aerodynamics...
Are we still talking about TURN RATE or TURN Radius? Reducing power can decrease your turn radius to allow for a gun solution. It doesn't always mean a better turn Rate that's a factor of wing loading. They're two different things and of course everything has to do with where the plane is within it's own flight regime or envelope if you will. Can we leave some of the Magical ideas out of this thread for a moment? Last edited by JG27CaptStubing; 07-09-2010 at 04:37 PM.
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#3
07-09-2010, 05:33 PM
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David603, unless you are above best-turn-rate speed, downthrottling a Fw 190 seems to me to have no measurable improvement in sustained rate - in fact it seems to make it worse, as theory predicts. If you've got real evidence to the contrary, please provide it. Arguments about turn rates based on subjective opinions don't really get us far. I've managed to do some basic testing, using my autopilot, but this needs modification to do this properly. I'll try to get around to this soon, but meanwhile any other evidence will be welcome.
At a given sustained power setting, airspeed and turn rate, the AoA will be whatever it needs to be - that the Fw 190 gives better results at a lower AoA than the edge of the stall seems evident from testing - hence the fact that the best rate is faster than the minimum radius. With the Spitfire, the difference is less, suggesting that the best rate is at a higher AoA. JG27CaptStubing, I see no reason why downthrottling would reduce turn radius, if you are already at best radius speed - again, I'd ask for evidence for this. It is just possible that downthrottling is temporarily helping the turn through a reduction in torque and in gyroscopic forces (though this shouldn't be a factor with a constant-speed prop), but I can't really see how. As I see it, the best turn rate at a given speed will otherwise be constant, regardless of power setting - all changing power does is determine whether the plane will accelerate or decelerate at that point in time. As has been pointed out, in the real world, extra power increases the local airspeed in the prop slipstream, which should help a little in high-power turns, but I doubt that IL-2 models this effect (we need to be careful about distinguishing between 'real-world' results and IL-2 ones, while discussing this subject). And as for 'magical ideas', I'd be happy never to see another word on the subject from Gaston. 
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#5
07-10-2010, 04:21 PM
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Quote AndyJWest:
"David603, unless you are above best-turn-rate speed, downthrottling a Fw 190 seems to me to have no measurable improvement in sustained rate - in fact it seems to make it worse, as theory predicts." ------------------------------------------------------------- -LOL... And what was the serial number of the FW-190A you flew that "proved" this??? That was funny though... And if you listen to an actual serious test, by actual test pilots using modern instruments (the only such test ever made in fact), you will find the "best unsustained turn rate" speed in WWII fighters is most often "very close to the maximum level speed" (1989 test of 4 types by "The Society of Experimental test Pilots")... So basically, downthrottling is only helpful while above level speed in a dive?!? 'Scuze me: I think your logic demonstrably sucks... But let's not listen to what actual pilots say about downthrottling: Like I said before, what do these guys know compared to simmers for God's sake!: ""I learned to fly with the "Cannon-Mersu" (MT-461). I found that when fighter pilots got in a battle, they usually applied full power and then began to turn. In the same situation I used to decrease power, and with lower speed was able to turn equally well. I shot down at least one Mustang (on 4th July 1944) in turning fight. I was hanging behind one [2-4 full 360° circles in another interview about the same dogfight], but I could not get enough deflection. Then the pilot made an error: he pulled too much, and stalling, had to loosen his turn. That gave me the chance of getting deflection and shooting him down. It was not impossible to dogfight flying a three-cannon Messerschmitt." " When the enemy decreased power, I used to throttle back even more. In a high speed the turning radius is wider, using less speed I was able to out-turn him having a shorter turning radius. Then you got the deflection, unless the adversary did not spot me in time and for example banked below me. 250kmh seemed to be the optimal speed." - Kyösti Karhila, Finnish fighter ace. 32 victories. Source: Interview by Finnish Virtual Pilots Association." --------------------------------------------------------------------------------------------------------------------------------- -Yes you are correct: 250 km/h (160 MPH) is a terribly high speed that does make downthrottling helpful: You just know the wings are about to fall off right then... As to why engineers and propeller aircraft designers don't know about downthrottling, excuse me, but last time I looked, these guys were not experts at putting bullet holes in other people's aircrafts... Even Hartmann never mentions downthrottling, and was hostile to turn fighting, so it seems it was one of those counter-intuitive things that never got universally acknowledged, even among those who DID put bullet holes in other people's aircrafts... But I have to agree: Simmers put a lot more combat flying hours than those people ever did: What could they possibly have to learn?!? Gaston Last edited by Gaston; 07-10-2010 at 04:25 PM.
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#7
07-10-2010, 04:50 PM
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Love it how the same quotes get misunderstood, removed from their context and cherry picked, on and on, to support a claim(note, something that can be solved with Physics and Maths alone) that nothing else does. Veterans cant be wrong, no way, they were there, even if one would take whatever they said completely out of context.
I see no reason to repeat the 150 pages of Ubizoo here. By the way, perhaps go and see your own post, Gaston, I dont think even YOU would think a turning radius can be quick, do you? Karhila didnt.   EDIT: by the way, 250kmph IAS is well below 109's speed for best rate of turn.
Last edited by Erkki; 07-10-2010 at 04:52 PM.
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#8
07-10-2010, 04:53 PM
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Haha, is he still comparing a poor low-speed turnfighter with no high-lift devices to the 109 as a turnfighter and concluding that its poor performance at said speeds makes the 109's best turn speed really low? Booooring! If you're turn-fighting in the sense of just flying circles you don't necessarily fly at your best turn speed, but the speed which maximises your advantage relative to the opponent. Against the laminar-wing Mustang's poor low-speed turn rate and lack of leading edge slats and so on, the 109's advantage probably IS maximised at much lower speeds than you'd expect. That doesn't make this situation universal, though, does it? Mainly since the whole tactic still relies on the Mustang pilot committing to the turn instead of just pulling high and laughing at the 109 pilot's inability to follow because he's now going at a hair over walking pace.
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#9
07-10-2010, 07:44 PM
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Quote Erki: "EDIT: by the way, 250kmph IAS is well below 109's speed for best rate of turn."
Yes, the best UNsustained turn rate (Corner Speed) for the Me-109G, especially if trimmed tail-heavy, is probably in line with what was found by the only modern-instrument test ever made of WWII fighters, for the P-51D, F4U, F6F and P-47D, as found by "The Society of Experimental test pilots" in 1989: "VERY close to the maximum level speed"... Which confirms that Karhila is NOT talking about that: He is talking about the best SUSTAINED turn rate, and since 160 MPH is well below some of the highest sustained turn speeds the Me-109G can pull (it can probably sustain quite tight turns up to 280 mph at least, if not more) it demonstrates, as he intends to say in the clearest way possible, that the fastest speed the engine will allow in sustained turns is not the best way to go... In other words, this demonstrates that being as close as possible to the 320?-400 MPH "Corner Speed", while sustaining level turns, is NOT helpful to the cause of sustaining the highest possible sustained turn rate, or at least the best sustained turn rate/radius combination. Therefore full power is NOT helpful, and he contrasts very clearly his method to that of fellow pilots: "I found that when fighter pilots got in a battle, they usually applied full power and then began to turn. In the same situation I used to decrease power, and with lower speed was able to turn equally well." In WWII combat "turning" typically lasted at least 2-3 full 360° circles, AT A MINIMUM, and 45(!) full 360°s not being unheard of (15 minutes + of continuous turning to one side), but that sounds unfamiliar to simmers who are obsessed with unsustained turns that were meaningless in real-life WWII combat with real, non-magical guns... This is why he felt the need to emphasize the need for downthrottling in SUSTAINED turns, quite apart from the issue of brief overrun avoidance that was mostly a preoccupation of some of the faster US fighters while in dives... In any case, the REAL best UNsustained turn rate (Corner Speed), is so high in most WWII fighter types, that downthrottling to it would practically be limited to being in a dive... So again, downthrottling is obviously not meant here for a quicker turn while in a dive or in a high-speed overrun, despite the best efforts here of those who would muddy up everything with imaginative fiction... Poor Karhila tried to be clear about what he was saying, and his general purpose is perfectly obvious, but then he is up against quite valiant efforts to confuse everything he says into a pile of mush... I greatly admire this argument that says the quotes I made are taken out of context, but then doesn't ellaborate on what the intended context is... I'll give it a try...; Get this: The intended context here is that when Karhila is at 400 MPH while in combat (typical in-combat speed when you light up the twin JE after-burners you know...), then this COMMON situation requires that he downthrottles to his "Corner Speed" of 350 MPH where he will THEN throttle back up to maintain speed as close as possible to this best unsustained turn speed... Oh, he forgot to mention anything about throttling back up? Well it's understandable: Old age you know... But throttling back up IS part of the "context" you know, when you reach the "right" speed: It's just that this "context" is invisible in this particular case... Trust them... Not! Gaston
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#10
07-12-2010, 03:52 PM
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Quote:
The SR71 takes over 70+ miles to turn around when it was slowing for landing. That's also turning when it was at a very high Mach number. It's a gross example but I think you get the idea. Quote:
Power and elevator is used during a turn to make up for the loss of Vertical Lift Component. When you turn you're vectoring the vertical component of lift into the horizontal. You will need more lift to keep the plan level hence power and back pressure. Remember airplanes can fly in various flight regimes.. You can be in different places in the power curve. Very high power low speed versus very high power high speed. You still have the same power setting but your in a different place in the curve. The point in illustrating this is to show why there is so much confusion with some of these discussions.
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