Spit/109 sea level speed comparisons in 1.08 beta patch

[JtD]

The general error of the interpretation of a speed advantage is the assumption that the slower plane has to match the faster plane at all costs. That assumption is totally unrealistic.

The general trend is in fact that the faster plane has the biggest advantage while flying straight, true against both better climbers in a sustained climb or better turners in a sustained turn. Entering a climb or turn that will be matched by the opponent, will in return reduce the speed advantage. That's how it works in combat.

[Robo.]

Originally Posted by Crumpp

I admit I have limited knowledge about virtual airplanes. My expertise lies with the real ones.

Do you dogfight in the real ones? Do you dogfight at least in the virtual ones? Apparently not - that's all I am saying. I appreciate your theoretical knowledge of a/c engineering but you're simply wrong here. Not with the physics, there is nothing to argue about - but everything else you're saying makes no sense from the fighter pilot's point of view.

Originally Posted by Crumpp

In actual dogfight, physics does not change.

Of course not but what you're saying has nothing to do with the ability of the aircraft to turn in a combat situation. You got it right with the best performance velocities - and that's all the turnfight is. The fact that the 109 at say 400km/h can turn better than a Spitfire at say 250km/h is irrelevant. Useful in combat, but not for turnfight. It's called 'turn and burn' where the opponents get the best use of turn rate advantage. In this particular case, Spitfire has got the advantage.

Originally Posted by Crumpp

Not an issue and has not effect with what happens in reality. It is hard to overcome the physics of the Bf-109 being lighter with the same power. This is an advantage where performance is thrust limited.

Lighter with the same power = better climbrate but not necessarily better turnrate in typical combat situations. The Spitfire though could still outturn the 109

If you could perhaps describe how exactly would you outturn a Spitfire Mk.I in a Bf 109E, I am very interested. Everything you are saying is true but you would be dead in a turnfight because you're wrong about what is important in actual combat.

[pstyle]

Crumpp, can you advise the source of your graph data? Cheers.

[Kurfürst]

Originally Posted by Glider

I don't know the numbers for the parasitic drag for these aircraft but would expect the difference to be marginal. The Spitfire is a larger aircraft and this would count against it but the 109E has less curves and is less aerodynamic which would balance it out. Indeed the 109F was more streamlined and this contributed to its improved performance. Which has the advantage I don't know but I would expect it to be close.

Parasitic drag is easy to approximate. The 109E needs less power at all altitudes to achieve the same or higher speeds (check for example the power available / speed reached at FTH. The Merlin III has a bit more power, yet both aircraft reach the same speed, 570 kph, which clearly points to less parasitic drag on the 109E.) This is true for the Emil/Mark I., and even more so to later variants. The 109G for example is about 30 kph faster on the same power, the 109K is about 40 kph faster on the same power.

I believe your bottom line re a faster aircraft always outturning a slower one to be wrong. If it were right the 262 would out turn everything

You seem to have missed the "at high speed" part.

And yes, the 262 does outclimb and outturn every prop job at high speed. It is simply to understand, say a Mustang has a top speed of about 600-630 kph even at +25 lbs boost. At this speed it is pulling 1G, drag is about minimal (almost entirely parasitic drag), and thrust equals total drag. It has no excess thrust. If it starts to turn, induced drag and so total will increase, and since the aircraft has no thrust reserves, it will start to decelerate, and loose speed. Its incapable of pulling any sort of sustained turn.

The 262 at about 600 kph still has a LOT of excess thrust - enough for another 230 kph. If it starts to turn, induced drag and so total drag will increase the same, BUT since the aircraft has no thrust reserves, it can use this excess thrust to overcome excess thrust in say, a 2 g turn. The turn is not very fast but its still a steady turn and the aircraft maintains speed.

See attachment for Spit IX. The Spit IX was an excellent turner and runs circles around the 262 at lower speeds. Come 500 kph, and the Spit is simply running out of thrust, can hardly turn at all, while the 262 can still pull a fairly decent turn. The Spits only hope is to go for an instantanous turn and hope for snapshot a few seconds before it blows all speed and becomes hapless. Its an extreme example, but demonstrates very well how things can get very different at high speed where one aircraft has a speed advantage.

Originally Posted by Robo.

Very true, but this has nothing to do with a sustained turn time. Say you're attacking a Spitfire in a Fw 190. You're much faster, he breaks and at that speed difference (him slowish, you very fast), you can turn inside him for long enough to place a burst in front of him. You lose some speed, he loses a wing if you hit, but that's not a sustained turn competitiion. You would never ever even at this theoretical advantage at this particular speeds enter a turn and burn fight and remain in that turn because you would lose the fight.

Hi Robo!

I guess there is some kind of misunderstand, what I meant is when two aircraft turn at (the same) high speed, and one of them is faster. In these circumstances the curves change to the favour of the aircraft with more excess thrust (generally speaking, the faster aircraft). See the Mark Vc vs. 190A-5 turn curve. Again the Mark V runs circles around the 190A-5 at lower speeds. Come 450 kph, and the Spit is simply running out of thrust, can hardly turn at all, while the 190A-5 can still pull a fairly decent turn. The Spits only hope is to go for an instantanous turn and hope for snapshot a few seconds before it blows all speed and becomes hapless.

Not to mention G-load and blackout. Or if you're in a 109 the elevator stiffness at high speed would be (and is) a massive issue, too. In a sustained turn entered from higher speed, you happen to slow down anyway and the best you can do as a pilot is keep your speed at optimum (not to slow down too much) and watch the G load because if you can't see you can't shoot. We're talking pure TnB fight where the sustained turn rate plays a huge role (and pilot's skill is another 50% because).

In sustained turns - no. Few if any aircraft could pull more than 2.5 g, some of the best like the Mark IX at +25 could hope to pull around 3 g and sustain airspeed. 3 g is very easy to pull even in a 109 with one hand, and blackout doesnt start until about 5 g. This the best turn possible at about 270 kph, at higher speeds the aircraft can pull even less, so g load is not a factor - unless you are going for an unsustained turn (lead pursuit) at which you blow speed to get a snapshot.

Obviously, this rarely happens in RL (or virtual skies) because you don't want to burn all your Es in a sustained turn, especially so in a 109.

You would be surprised how many 109 pilots still enter TnB fight vs. Spitfires. And they will almost always lose because (surprise surprise) the Spit has got much better sustained turn.

Bad tactics. Spitfires are tougher nut to crack, because they are about as fast as 109s - but for example against Hurricanes, which are much slower, a slow turn above 350 km/h might bring surprising results. The Hurri may try to blow speed, but that's usually a death sentence against a good pilot who knows how to exploit superior E-state.

In theory. I would really like to see how a Me 262 outturns a P-51 in a sustained turn even at very high speeds.

It simply has much more excess thurst at high speed - hence it can maintain a sustained turn while the P-51 cannot at all - provided both aircraft are at high speed.

[bongodriver]

See attachment for Spit IX. The Spit IX was an excellent turner and runs circles around the 262 at lower speeds. Come 500 kph, and the Spit is simply running out of thrust, can hardly turn at all

So are you suggesting aircraft can't turn without thrust?......so every glider I have seen change direction is purely my imagination?

surely you really mean to say the Spitfire will simply loose some ground, but it will without doubt still be able to turn.........some of these theories are getting bizarre.

[Crumpp]

Crumpp, can you advise the source of your graph data? Cheers.

It is a spreadsheet that calculates turn performance I made.

It is a sophisticated analytical tool that determines relative turn performance using standard incompressible flow theory. That was the predominate theory in use during WWII and is the same one used by the RAE.

By using EAS, all you have to adjust power production and you are in the ballpark for the Indicated Airspeed you should see performance.

I did it that way so it would be useful for the game. If you know the PEC, it is not hard to have the spreadsheet convert EAS to IAS directly.

It takes a little time but it can reworked for any aircraft.

[Crumpp]

So are you suggesting aircraft can't turn without thrust?......so every glider I have seen change direction is purely my imagination?

Now we have to teach people the basics.

Aircraft cannot sustain performance without excess thrust and the forces in balance.

Any airplane without excess thrust can use gravity and momentum to achieve instantenous performance.

A glider uses gravity to propel itself which is why we don't use them on transatlantic flights. They exist in a purely instantenous performance condition. They cannot sustain performance under the power of gravity alone and must constantly trade altitude for airspeed without an alternate form of energy.

Gliders seek an alternate form of energy in the form of rising air currents to stay aloft.

Flying a sailplane is probably the closest thing any human will come to feeling like a bird. Powered only by gravity and air currents, these gliders move silently through the sky, often for hours at a time.

http://www.mansfieldct.org/Schools/M...ightglider.htm

Bongodriver, try to make a turn from maximum level speed in an airplane maintaining both airspeed and altitude.

[macro]

Originally Posted by bongodriver

So are you suggesting aircraft can't turn without thrust?......so every glider I have seen change direction is purely my imagination?

surely you really mean to say the Spitfire will simply loose some ground, but it will without doubt still be able to turn.........some of these theories are getting bizarre.

no mate he means (i think if i got it right) turning without loosing speed. any spit pilot can turn and loose a EA on his tale in clod but will loose speed instantly. he is talkign about going into a turn and keeping the turn without loosing speed. which isnt that bigger deal imo

this isnt all bad for the spit tho as this can be used so the plane behind overshoots and misses, i.e turning inside his turn so he cant get guns on you. puts you out of the fight but also keeps you alive, at least a while.
a 109 couldnt do this to a spit, this is why you go into a fight with a 109 always with higher energy or dont bother at all, so you can afford to loose that speed.

[Crumpp]

better climbrate but not necessarily better turnrate in typical combat situations.

The readers understand that a better climb rate is indicative of more excess thrust?

Once again, the Spitfire shines in lift limited performance while the Bf-109 shines in thrust limited performance.

[Crumpp]

this isnt all bad for the spit tho as this can be used so the plane behind overshoots and misses, i.e turning inside his turn so he cant get guns on you. puts you out of the fight but also keeps you alive, at least a while.
a 109 couldnt do this to a spit, this is why you go into a fight with a 109 always with higher energy or dont bother at all, so you can afford to loose that speed.

Any airplane can do this to another airplane.