Spit/109 sea level speed comparisons in 1.08 beta patch

[Glider]

First thanks for the replies

My first observation was that the Spit test you used didn't include the extra power from the 100 octane fuel

Originally Posted by Crumpp

It does not change the outcome or outlook. Despite the higher wingloading, the Bf-109 has more excess thrust because it is lighter.

I say it does make a difference as the extra boost came with a significant increase in power which significantly improves the power weight ratio. Also lighter is a factor but a bigger one is drag which is where the 109 loses out.

Re your second reply

Don't confuse high load factors found in instantaneous performance with low load factors achievable in sustained performance

You have a point but nowhere have I seen anything that says that the 109 had a better sustained performance. Also what is sustained? Everyone seems to agree that the SPit turned tighter and faster so what is sustained. Are you trying to say that after X turns the 109 would start catching up because it has a better sustained performance?
My understanding is that a sustained turn rate is one that can be maintained for long periods of time without losing altitude, maximising the turn rate and radius of turn.
On both these counts the Spit will beat the Me109 as proven in the Rae tests which were sustained turns without losing height

Re the Graph,s I still don't understand what you are trying to prove. Lift limit is a new term to me but I assume it has something to do with the max lift the wing will generate given a certain angle of bank, but how load factor impacts this I don't have a clue, as the load doesn't impact lift. Load factor increases with bank which will increase the amount of lift required but lift available in the wing is a constant
Thrust Limit is also a new term to me I assume its a power to weight thing, but again don't understand how load would impact it as thrust is a given depending on height etc but not as far as I am aware load factor. The thrust required is increased as the bank increases but in a given aircraft it is a fixed amount.

[Crumpp]

I say it does make a difference as the extra boost came with a significant increase in power which significantly improves the power weight ratio

What power and speed? I will recalculate and repost.

You have a point

If you understand stability and control engineering, Mtt did a good job on the Bf-109.

Also what is sustained?

It is the performance the engine can perform until it runs out of gas.

My understanding is that a sustained turn rate is one that can be maintained for long periods of time without losing altitude, maximising the turn rate and radius of turn.

Yes

On both these counts the Spit will beat the Me109 as proven in the Rae tests which were sustained turns without losing height

The RAE test's were of turning ability. If you look at the test the RAE flew the airplanes at ~115KEAS in their evaluation.

[Crumpp]

Lift limit is a new term to me

Lift limit is the aerodynamic limits of the wing. Propeller aircraft are called power producers and are aerodynamically limited at the stall point.

The lift line is the stall line.

load doesn't impact lift

Load does impact lift.....

Thrust Limit is also a new term to me

It is the thrust limited portion of our envelope. Here the aerodynamics of the wing are not the limiting factor but rather how much excess thrust the aircraft can produce.

[Glider]

Originally Posted by Crumpp

Load does impact lift.

I think you will find that load increases the lift required in a certain situation and if I remember correctly roughly doubles at 60 degree bank

[Glider]

Originally Posted by Crumpp

What power and speed? I will recalculate and repost.



If you understand stability and control engineering, Mtt did a good job on the Bf-109.



It is the performance the engine can perform until it runs out of gas.



Yes



The RAE test's were of turning ability. If you look at the test the RAE flew the airplanes at ~115KEAS in their evaluation.

So to sum up you do not disagree that the Spit had a better sustained turning ability, your position is that the 109 had a better sustained straight line performance because the engine had a better sustained performance.

Just trying to get things straight in my mind before going any further

[Kurfürst]

Originally Posted by Glider

Also lighter is a factor but a bigger one is drag which is where the 109 loses out.

Actually drag is the factor where the 109 may win out at high speeds. Parasitic drag is much lower on the 109 than on the Spitfire, and parasitic drag is what dominates total drag at higher speeds. The Spitfire turns better at low speeds because it has lower induced drag, and induced drag is what dominates total drag at low speeds.

Sustained turn is just the maximum g-load at which drag = thrust. Maximum sustained turn (i.e. the number usually quoted for turn times) is always achieved at lower speeds, but that doesn't mean the trends continue to high speeds and may be reversed. I am not sure if there is much to it - it can be well true that both aircraft can only turn so slowly in a sustained fashion that there is no tactical point in it.

Bottom line, a faster aircraft will always outturn a slower aircraft at high speeds, the question is not really wheter this happens or not, but: by how much?

[Glider]

Originally Posted by Kurfürst

Actually drag is the factor where the 109 may win out at high speeds. Parasitic drag is much lower on the 109 than on the Spitfire, and parasitic drag is what dominates total drag at higher speeds. The Spitfire turns better at low speeds because it has lower induced drag, and induced drag is what dominates total drag at low speeds.

Sustained turn is just the maximum g-load at which drag = thrust. Maximum sustained turn (i.e. the number usually quoted for turn times) is always achieved at lower speeds, but that doesn't mean the trends continue to high speeds and may be reversed. I am not sure if there is much to it - it can be well true that both aircraft can only turn so slowly in a sustained fashion that there is no tactical point in it.

Bottom line, a faster aircraft will always outturn a slower aircraft at high speeds, the question is not really wheter this happens or not, but: by how much?

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.

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

[Robo.]

Originally Posted by Kurfürst

Sustained turn is just the maximum g-load at which drag = thrust. Maximum sustained turn (i.e. the number usually quoted for turn times) is always achieved at lower speeds, but that doesn't mean the trends continue to high speeds and may be reversed.

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.

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). 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.

Originally Posted by Kurfürst

I am not sure if there is much to it - it can be well true that both aircraft can only turn so slowly in a sustained fashion that there is no tactical point in it.

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.

Originally Posted by Kurfürst

Bottom line, a faster aircraft will always outturn a slower aircraft at high speeds, the question is not really wheter this happens or not, but: by how much?

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.

[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.