Fact: Reduced airspeed results in a smaller radius... Don't confuse Turn Rate with radius or compare it to Best Cornering Speed. Two different things.

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.

Having a constant speed prop has nothing to do with Gyroscopic effects... Torque is reduced at a lower power setting and it does effect the turn but it's usually countered with rudder...

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.

No it doesn't. Corner speed gives you the best turn rate and turn radius, though the turn radius does not get significantly larger until the plane reaches very low speeds. Of course, this is the plane limit. It might be easier for a pilot to fly a tight turn at 3 g's than at 6 g's.

If I take your SR71 example seriously, you might be confusing the effects of different designs with the effects of changing speed.

Um, no. there is an optimum speed (the 'best radius speed' I referred to) which results in a lowest-radius turn. Go slower than this and the radius increases again.

With a constant-speed prop, both the rate of rotation and the mass are constant, so gyroscopic forces are constant, over any power range the prop can maintain its 'constant-speed' setting. Torque isn't the same thing at all.

And yes, I'm fully aware of 'power curves'. This is what the debate is about. All I'm saying is that I can see no reason why one will get either a tighter sustained minimum-turn-radius, or a quicker sustained best-turn-rate with a reduced power setting. Again, I'd ask for verifiable evidence of this, either in real life (accurately measured, not mistranslated anecdotal evidence...), nor in the IL-2 sim.

JtD, I think you are mistaken about what 'corner speed' means. As I understand it, as the phrase is used in modern terms it is the highest speed at which you can safely apply any control input without risking structural failure. At lower speeds the wing will stall before G limits are reached, but any higher than corner speed and you may rip the wings off or whatever. Given the necessary safety margins, 'corner speed' is thus more a limit on what the pilot is supposed to do than a limit on what the plane actually can do.

I think I mistated in my last post. That's correct Corner Speed gives the best Rate and Best turn Radius but they are two very different things when talking about a fight. It get's confusing because we are all trying to gain angles to put the bad guy withing a firing solution. If you're above Corner Speed this will result in a larger Radius period end of discussion. You will quickly come up against the G limits of the plane at higher speeds. That's why the SR71 at Mach 3 takes up that much space to TURN.

Here some definitions everyone... This is a cut and past from BFM basics.

Turn rates are further divided into:

1.Instantaneous turn rate: the max turn rate at any given airspeed (energy depleting).

2.Sustained turn rate: the max turn rate available while sustaining energy.The fixed and variable factors begin to interrelate. G is the ratio of lift to weight. As you know,in turns or directional changes, lift must exceed weight, and you must apply G loads greater than one. At a constant TAS, to increase "G", you must increase AOA. Radial "G" will dictate the turn radius and rate. Maximum instantaneous g is the maximum lift a wing may generate at agiven airspeed. Maximum instantaneous g is dependant upon the aircraft airframe capabilities.

@Andy

Corner Speed
Corner speed is an important factor of maximum turn performance. Corner speed is defined as the minimum airspeed at which the maximum allowable g can be generated. At corner speed,the aircraft can attain its maximum turn rate. For our purposes, 280 KIAS is the T-2C cornerspeed. Below this speed, if you attempt to pull more "G", the aircraft will enter buffet and stall at its aerodynamic limit. This results in an increase in the turn radius and a decrease in the turnrate. On the other hand, if the aircraft is maneuvered above the corner speed, the max allowable"G" becomes the limiting factor. The excess airspeed (above corner speed) will result in a turnradius increase and a turn rate decrease. Knowing and flying the corner speed and the appropriate AOAs will give the fighter the mostbang for the buck: the best turn performance for the minimum amount of energy loss.

I don't think I am, and actually think the three of us are on the same page now, just using different words for the same thing or looking at it from a different point of view.

Essentially, below corner speed the plane stalls before it breaks, above corner speed it may break before it stalls. Flying at corner speed gives you best rate and radius of turn. That's about it.

Note: WW2 warbirds are in general not capable of maintaining corner speed.

Thanks for that - more or less what I've already written.

As for turn rates/turn radii, I've only ever been commenting on sustained turns - no WWII fighter is capable (as far as I'm aware) of achieving its best sustained turn rate, or minimum-radius sustained turn, at anything approaching its corner speed - though I'm not sure that 'corner speed' was even a design consideration at the time. I don't recollect seeing this speed being given in the pilots' notes etc I've seen. I'm sure that most pilots were aware that you could cause structural damage by pulling back hard enough in a high speed manoeuvre, but was this ever explicitly stated as a manoeuvring speed limit?

This is true... What is interesting is that corner speed is the Minimum speed needed to pull max G.


Moving forward... I agree I don't think Corner Speed was a consideration given the power to weight ratio they have. We aren't talking about a F16...

I think IL2 gives a pretty good representation of what we are all concerned about. Getting that gun solution. I don't look at my airspeed all that much except when I'm at limits like dive and stall. I look for angles and of course picking when to spend to make a shot. Flying around in circles isn't going to get you very far with someone that will counter with a reversal or an extension.

Absolutely. And even in a turn fight, one can use yo-yos etc to take advantage when appropriate. The whole sustained round-and-round dogfight scenario is so unlikely that I don't think it is even worth considering as historically significant - and of course anyone engaging in it is a sitting duck to an outsider...

It probably helps to know things like best-sustained-turn-rate speed etc, but as TheGrunch has pointed out, you need also to take into account the performance of your adversary.

-Excuse me but let me quote this again as this is too unbelievable: "The whole sustained round-and-round dogfight scenario is so unlikely that I don't think it is even worth considering as historically significant"

Have you ever read a SINGLE WWII fighter combat account in your entire life?!?

I will post a few here that went on for 15 minutes to one side:Most of them go on for at least a full minute (2-3 360s), two minutes being extremely common also: 4-6 360s... Almost none of them last for less than over one full 360°, regardless of the types involved...

By comparison with turn fighting, "Boom and Zoom" is far less significant, except mostly by P-38s against Japan, and on the Eastern and Desert Front by Me-109s (apparently a centralized armament helps). Even then, turn fighting is at least as important as anything else anywhere, and "Boom and Zoom" is virtually non-existent on the 1944 Western Front, which was the most technically advanced front of WWII...

You need to actually read a few WWII combat reports now and then...

For the Me-109G, vertical maneuvers are clearly a compensation for its deficient turn performance, until superior US vertical performance in 1944 forced it out of its stereotypical "see-saw" (the reason Rall called it a "floret")...

I guess you don't realize that once you have committed to a turn fight, and the enemy is close enough behind, you cannot just "step out" of it at will: Any slackening of the turn will give the pursuer an easy kill...

The trouble with Il-2 may be that the roll and especially the pitch response has too little inertia delay ("mushing") to impose a life-like turn contest "lock".

Or it could be that the issue is that the restricted in-game field of view angle is giving too much escape possibilities with a large maneuver...

Once the turn fight has slowed you down (which could be as quick as after 180°), the real-life pitch response may no longer be crisp enough for a fast enough split-s (remember that in WWII fighters, "Corner Speed" is mostly near maximum level speed)... That's why they tend to go on forever unless the pursued uses the pursuer's under-nose "blind spot" (necessary to gain enough sight lead for the pursuer) to push down on the stick and "disapear" at the very moment it was about to be hit...

Even then, you'll note from Hartman's description of this tactic that there is no time for a much more confortable split-s...

In addition, any downward escape (and by definition, most of the time, an escape from a turnfight can only really be downward: Zoom or spiral climb escapes are very rare and require a very large climb performance disparity) will put you in a lower position, which is usually catastrophic: In real-life you cannot easily raise your nose fast and accurately while turning from a lower position: Simply by virtue of being higher, the pursuer can lower his nose easily and accurately while tracking your movements...

Losing the "high ground" is probably not represented severely enough in Il-2, as it meant everything in real-life WWII combat, and is likely the main reason why horizontal turn battles where so common and so prolonged.

(BTW, Anybody outside the turn were offered only limited high-deflection shots that were of not so great value to a real-life 2% gun hit rate, until the introduction of gyro-sights, and maybe even then...)

In jet combat, being lower can actually be an advantage, but that is far removed from the reality of WWII propeller combat...

As to the comment about the real-life guns versus the "magical" ones in-game, it has nothing to do with me complaining about my playing Il-2: I have never played Il-2 and don't intend to do so in the near future. I am playing little enough as it is my own air combat simulation, which I have to admit also fails to reproduce those 15 minutes turn battles, but for reasons of boardgame mechanics.

At least a full 360° is common enough...:

http://forums.ubi.com/eve/forums/a/t...708#5031083708

The research took 14 years, and all the profile drawings except the P-47D were made especially for it, given inaccuracies in most drawings...

Gaston

P.S.: The "weakness" of actual guns is based on Luftwaffe assesments of a 2% average hit rate in real-life...

G.