Spit/109 sea level speed comparisons in 1.08 beta patch

[Crumpp]

You're saying the 109 is flying at the Spitfires best turn performance speed, I am saying the 109 is flying at its own best turn performance speed. Quite a difference.

No I am not. I am saying both aircraft are flying best turn performance.

Best turn performance is a specific speed.

In the single point analysis of best turn performance, the airplanes are at different speeds.

When we look at the entire envelope, the Spitfire must be at a slower speed in order to outturn the Bf-109.

[Igo kyu]

That graph must be rubbish.

I don't pretend to understand what it's supposed to mean, but the aircraft leave the graph in opposite directions. That just doesn't happen in graphs of real world effects.

[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.

[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?

[ACE-OF-ACES]

Originally Posted by JtD

No, it says the Spitfire at its best turn performance velocity beats the 109 at its best turn performance velocity. According to these figures, the 109 cannot outturn a Spitfire in a sustained turning fight at sea level unless the Spitfire lets it happen, however, the Spitfire can outturn the 109 in said scenario no matter what the 109 does.

Bingo!

[Crumpp]

I still don't understand what you are trying to prove.

Not sure you understand much of the science at all. I certainly don't like the attitude or implication I have something to prove or a vested interest in the outcome.

The math is what it is.....

[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

[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