Spit/109 sea level speed comparisons in 1.08 beta patch

[Robo.]

Originally Posted by NZtyphoon

In this case Crumpp is right, just for once - the Spitfire III prototype was built with the Merlin XX, which had a single-stage two speed supercharger - it also had clipped wings, a revised undercarriage which was raked forward by 2 inches, and a revised windscreen with two straight side pieces and flat windscreen with internal glass (the undercarriage and windscreen were later used on the Spitfire VC) . When it was decided to reserve the XX for Hurricane IIs the Mk III was adapted to take the first Merlin 60 series engine, becoming a Mk IX prototype. The Mk IV was very similar to the Mk III but had the Griffon engine.

Very true, thanks for the details NZtyphoon. The key is the different (clipped) wings and therefore different wing load than the one we see at the top right corner of the above sheet.

Crumpp came up with the Merlin XX theory only to prove that the fan plot posted was for different engine with 2 stage supercharger. That is wrong just as was wrong his assumption that the chart posted previously by Banks (post 345) already included RAM effect.

No matter how I look at it, the post 345 makes perfect sense.

[Crumpp]

All I said was that you were wrong in your statement that 400kph fixed trim setting was due to the 'good speed for dogfight' reason

Again, robo...

I asked you if you know how to determine the cruise speeds for an airplane. These are not random figures, pulled from a hat.

They are specific points on the power required and thrust required curves. The cruise speeds points of the thrust required and power required curves are fixed by the design and completely independent of engine settings.

Do you need me to talk you through how to determine them?

It is very easy to proved I am not wrong if you understand how the physics works.

[Robo.]

Originally Posted by Crumpp

Again, robo...

I asked you if you know how to determine the cruise speeds for an airplane. These are not random figures, pulled from a hat.

They are specific points on the power required and thrust required curves. The cruise speeds points of the thrust required and power required curves are fixed by the design and completely independent of engine settings.

Do you need me to talk you through how to determine them?

It is very easy to proved I am not wrong if you understand how the physics works.

No, thank you, that is not necessary at all. I already know you're completely wrong with your 'combat speed default trim setting' statement, no matter how hard you now try to prove that you were actually right.

As for the actual question (sorry I thought it was a rhetorical one) I don't know how exactly to calculate cruise speed for an aircraft, and I don't need it in order to see that you wrote 'combat speed' instead of 'cruise speed'. Now you will probably reply with another graph to prove that it's the same thing. Maybe you're even right, but essentially, you wrote nonsense, hence my reply. Consider my knowledge as limited if you wish, but then if I even can see that you're wrong and that you're bending facts to fit your bizarre theories (maintain rpm by changing it constantly, RAM effect, Merlin XX etc...), that says something about your activity here, not mine.

I am not too sure anymore about what are you trying to achieve on this game's forums, perhaps you enjoy the arguing for the sake of arguing, perhaps you enjoy the advantage you think you're having with your theoretical knowledge. I actually enjoy some of your technical posts and I have no problem to understand what you were saying, but when you're wrong you're wrong. And for some reason you never admit it, you just go on and on and every thread ends up to be about Crumpp vs. the 'sane world' rather than about the original topic. I fond that a bit frustrating to be honest.

Let me ask you a question you also omitted before - how exactly would a 400kph sustained turn in a Bf 109E be useful in actual turnfight vs. a Spitfire Mk.I?

[Crumpp]

I already know you're completely wrong with your 'combat speed default trim setting' statement

In otherwords, forget any facts....

You are going to stick to your immature and emotional reaction.


Well, let's see how it pans out.

You can look in the Bf-109E3 Flugzeug Handbuch and see that the engine out instructions call for the pilot to pitch for 200kph IAS. This is best glide speed and corresponds to L/Dmax.

If our curves are correct, this will be the botton of the thrust required curve and tangent of the power required curve.

First the Thrust and Power Required curves:



200kph = 124mph +10 mph PEC = 134mph CAS * .869 = 117KCAS = 117KEAS at sea level.

Yep, best glide aligns perfectly with our curves so we know the curves are correct.

Using the curves, it is easy to find the other cruise speeds.

Maximum endurance will be at the point of minimum power required. Carson's speed is a modern innovation and is the best balance of fuel consumption and speed.

The trim speed of 400kph IAS does not align with any cruise point on the curves. That means the speed was chosen for a different reason.

Now it we look at the rate of turn, or how fast an airplane can bring the guns on target, we see that 206KEAS is a point the Bf-109E3 maintains a healthy rate of turn advantage and can sustain better maneuvering performance.



So, if it was not intentional, it certainly was a very fortunate turn of fate that the Germans choose 400kph to set the trim for the Bf-109E3.

[Crumpp]

how exactly would a 400kph sustained turn in a Bf 109E be useful in actual turnfight vs. a Spitfire Mk.I?

Robo,

This is the key performance parameter for a fighter. It gives the aircraft which can sustain a higher load factor at a higher velocity the initiative in a dogfight.

This characteristic allows the Bf-109E3 to force the Spitfire to a lower airspeed in order to survive the fight.

The outcome of any dogfight is not predetermined. There are too many "what if's" and pilot skills are the determining factor.

What it tells Spitfire pilots is if you enter a sustained turn fight at high speed, the Bf-109 will win if you don't slow your speed down to the point you have a better sustained turn rate.

What it tells the Bf-109 pilot is you can maneuver against the Spitfire, just don't drop your IAS below 400 kph. If he breaks off and zooms at the point the Spitfire begins to out turn him, the Bf-109 will be above his opponent, out of reach, and able to engage/disengage at will.

400 kph is not a difficult point for the Bf-109 to maintain especially given the stability of the design. It is the trim speed and given the correct amount of power, where the airplane wants to be....

[Robo.]

Originally Posted by Crumpp

Robo,

This is the key performance parameter for a fighter. It gives the aircraft which can sustain a higher load factor at a higher velocity the initiative in a dogfight.

This characteristic allows the Bf-109E3 to force the Spitfire to a lower airspeed in order to survive the fight.

The outcome of any dogfight is not predetermined. There are too many "what if's" and pilot skills are the determining factor.

What it tells Spitfire pilots is if you enter a sustained turn fight at high speed, the Bf-109 will win if you don't slow your speed down to the point you have a better sustained turn rate.

Yes, I agree, you said that already before, and this is very well known to most virtual pilot on this forums. You're not saying anything new here. Yes, the 109 turns better at higher speeds, Spitfire wins at lower speeds. What I was trying to explain before was that in a TnB fight, it's usually lower speeds that matter and decide the fight.

There is absolutely nothing wrong with what you're saying, it just doesn't make sense in regards to actual combat. If you keep the 109 in 400kph sustained turn, the Spitfire will be able to shoot at you for long enough to kill you, even being slower.

Originally Posted by Crumpp

What it tells the Bf-109 pilot is you can maneuver against the Spitfire, just don't drop your IAS below 400 kph. If he breaks off and zooms at the point the Spitfire begins to out turn him, the Bf-109 will be above his opponent, out of reach, and able to engage/disengage at will.

If he breaks off and zooms we don't talk about sustained turn competition anymore. Everybody is well aware of 109s BnZ characteristics (if he extends vertically). Again, you're not saying anything new. It's the TnB that matter here. Pure TnB rarely happened because it would be a suicide for the 109 pilot.

Originally Posted by Crumpp

400 kph is not a difficult point for the Bf-109 to maintain especially given the stability of the design. It is the trim speed and given the correct amount of power, where the airplane wants to be....

What you're saying with this whole post of yours is basically:

109 can win a turnfight against the Spitfire as long as it won't turn with it

Spitfire has had better sustained turn rate than 109 and it was generally a silly idea to turn with it. This is the case in the sim as well and all other sims.

[Crumpp]

109 can win a turnfight against the Spitfire

Yes, that is correct.

If he breaks off and zooms we don't talk about sustained turn competition anymore.

Sure we are...

The Spitfire has lost and the Bf-109 has used its sustained turn performance to gain advantage and win the dogfight.

it just doesn't make sense in regards to actual combat.

That is because a computer game is not representing reality in this case.....

There is a very good engineering reason designers have strived for speed as the number one performance parameter for a fighter.

[Kurfürst]

Originally Posted by JtD

I agree it looks simplistic, but technically it is sound and I see no reason it not being an original document. No reason for it being one either, but I will accept it on face value as I see no reason to mistrust Mr.Williams on this issue. If you have more than a gut feeling, I'm willing to re-evaluate my opinion.

Its a gut feeling of course - I wasn't there when it was drawn (thank God for that!). To me it just seems that, given that the original was drawn with pen AND was labeled, compared to the rough approximation visibile on the pencil drawn +12 and +16(?!) lines, the latter lines were probably made by some aircraft enthusiast well after the war. The lines/figures look more or less a reasonable guesswork, but I very much doubt it has anything to do with any test establishment.

Originally Posted by Robo.

Yes, I agree, you said that already before, and this is very well known to most virtual pilot on this forums. You're not saying anything new here. Yes, the 109 turns better at higher speeds, Spitfire wins at lower speeds. What I was trying to explain before was that in a TnB fight, it's usually lower speeds that matter and decide the fight.

There is absolutely nothing wrong with what you're saying, it just doesn't make sense in regards to actual combat. If you keep the 109 in 400kph sustained turn, the Spitfire will be able to shoot at you for long enough to kill you, even being slower.

IMHO the real question is how much time to Spit has to shoot at you? Because if the Spit turns at around its peak sustained turn rate - at about 250 kph? 300 max? - its going to be a good deal slower than the 109; maybe slow enough to fall so behind that it will be out of realistic guns range? You cant shoot what is not in range, even if your nose points towards it..

Moreover if say both aircraft start at 400 + kph, the 109 maintains it while the Spit bleeds it off to get a snapshop, all the 109 has to do is to level out with a very significant E advantage, and if the pilot is good at Energy fight, its all cat-and-mouse from there on.

Generally it seems to me a good idea to keep the speed over 400 km/h in a 109. If the Spit tries to follow you in sustained 400 kph turn, or if he slows down to try to get you, he seems to be ... to have gotten into a bad position. Especially in a multi plane enviroment.. you can shoot what is slow, you cant shoot what is fast.

[Robo.]

Originally Posted by Crumpp

In otherwords, forget any facts....

Not at all! The fact is (still) that 400kph was NOT chosen by Mtt because of 'good speed for dogfight' reason, contrary to your statement. No matter how you try to re-pack your words, you were wrong.

Originally Posted by Robo.

Now you will probably reply with another graph

I specifically told you that posting the cruise speed calculation and graph is not necessary and irrelevant, but thank you anyway, it was interesting.

[Osprey]

Did he even read your post Robo? Your point just went whoosh over his head.