Spit/109 sea level speed comparisons in 1.08 beta patch

[Bounder!]

Originally Posted by JtD

Regarding level speed performance of the 109, a question raised by I think MiG-3U puzzled me, maybe you have a good explanation, I'm at a loss for now: How come the 109E is faster than the 109F at less power, if you accept the 498 km/h for the 109E at 990ish hp from the V15 test and the 495 km/h for the 109F at 1065ish hp from the 109F Kennblatt?

Just a stab, Kurfürst is probably the man for this question but looking up the weight of the 109e and 109f and it appears the later is heavier when loaded which might help account for the lack of speed increase over the emil?

[Kurfürst]

Originally Posted by JtD

Regarding level speed performance of the 109, a question raised by I think MiG-3U puzzled me, maybe you have a good explanation, I'm at a loss for now: How come the 109E is faster than the 109F at less power, if you accept the 498 km/h for the 109E at 990ish hp from the V15 test and the 495 km/h for the 109F at 1065ish hp from the 109F Kennblatt?

Its difficult to say how much it is on the 109F Kennblatt because the Kennblatt's figures are with the original ratings of the 601N at 495/515 (1.42/1.3, which were reduced to 1.25). In short the 495ish figure is for 1.3ata.

My best guess is that there was a major difference between the Emil and Friedrich propellers (also according to the propeller effiency curves I have seen), the latter was of smaller diameter and almost certainly meant for high altitudes, and probably less efficient in denser air, hence the relative stagnation of speed near SL. The Friedrich would be probably faster with a different prop.

But all of this is not so extraordinary or a surprise since the same can be noted when it comes to the Mark I / Mark V / Mark IX Spitfires's evolution. Hell the Mark I. at +12 is supposedly faster at SL than the Mark IX at +15 boost, how come..?

[ACE-OF-ACES]

Originally Posted by JtD

The chart Kurfürst posted is not a theory, it's a calculation.

True..

Originally Posted by JtD

Physics and maths are just as relevant as tests and pilot experience. There are methods that are standard and accepted. If you use them properly, they can be more accurate than tests and pilot experience and are imho at least as valid.

Agreed.. Just as relevant.. If used properly

As you (and others) know the old saying..

Garbage in Garbage out!

With regards to flight simulation..

You can think of the 6DOF flight simulation model as a black box.. With an input (plane parameters and current state) and an output (results)

The math in the black box can be good to go.. no errors.. But if you input bad values (plane parameters and current state) you will get bogus outputs (results)

With that in said..

I don't know if the 'results' of the Me262 or Spit used in the IL2Comp graph Kurfust posted have ever been validated.. As in have they ever been compared to any real world data, or checked by someone else to ensure the 'inputs' are correct.

In short, in this case the IL2Comp values are suspect until validated.. Sadly I don't know of any real world turn time data of the Me262 that can be used to validate the IL2Comp, which leaves only for someone to doulbe check the input values and 6DOF math.

[Kurfürst]

Originally Posted by Osprey

Hmmm, this isn't an original document, it's some html from your website. All of the RAE stuff and other docs are originals (except the 12lbs which is measured in test then calculated/translated/projected onto the graph)

You want the original document, Osprey?

Originally Posted by Osprey

Don't be silly Kurfurst. Willy is an old pal of Goering and a few keys of Colombian marching powder and some bonus wraps he'd have been on the hotline to Herr Hitler. We've all seen how Oscar Schindler did it.

Except it just didn't work that way. BAL (the Luftwaffe's QC group) was rejecting Me 262 if they did not do at least 830 kph.. They had a bit of reason and allowed planes even with 825, but no less was accepted.

Again. We are talking 262s. In 1945.

[pstyle]

Thanks Kurfurst, I’d not seen the V15 trials information before, the test-report is quite nice. Although I’d much rather have all of the pgaes in their originals, not just a few, and not have to rely on transcribed text into your html page.

The above aside, can you help me with a couple of questions:
1) What can we take from the apparent inability of any subsequent tests of the E1s or E3s (that I can find at least) to get anywhere near the “sea-level” (see question 4 below) speed of 493kmh or 498kmh? How do we explain that the prototype was able to record speeds that no subsequent 109 testing seems to have been able to achieve? I see testing data of 109E3 Nr1972, and 109E1s Nr1774 and Nr1791 (all of which are German tests, not British tests), none of which achieve above 485kmh at their lowest altitude of “0” (average is around 470)

2) Can you provide Blatt 3 of the testing documentation, the full-pressure altitude (Volldruckhohen) results – which I cannot find on your page?

3) Your tabulated summary of Blatt 5 indicates that the achieved speed (with the supposedly suboptimal engine pressures) was 493kpm at 0 altitude relative to the ground. Why does Blatt 6 indicate however that only 485 was obtained? is that because Blatt6 projects the speed down to sea level, whereas the tests were carried out at 0 altitude above ground, at a location (Augsburg?) already elevated (~440m) above MSL? If so, according to the test graph, do we get a sea-level speed of 485(490), not 493(49 for the V15?

4) the tests often make corrections for air pressure of a standard (Augsburg?) day "normaltag". Do we know what that pressure was?

[JtD]

Originally Posted by bongodriver

Oh, have I misunderstood something?...

Some are drawing wrong conclusions from the chart, but that doesn't change the chart. Kurfürst said the 262 can sustain a better turn time than the Spitfire at 400 mph, which is true. This will not win it a sustained turn fight though, as the Spitfire doesn't need to match the 262's speed. It can't do it in straight and level flight, so why bother in turns. Like I said, there's the chart and there's what you make of it.

Originally Posted by Kurfürst

My best guess is that there was a major difference between the Emil and Friedrich propellers...

OK, I can see that at altitude the F is at least faster than the E, even if still at more power. Do you have the propeller efficiencies somewhere so I could take a look at them? Regarding the Spits, the IX was quite a bit more dirty than the I, just like a G-6 was more dirty than an F. So I would expect it to need more power for the same speed. But the E-F issue is different.

Originally Posted by Al Schlageter

Doesn't the V in a designation mean a prototype/test a/c?

Yes, 109E prototype.

Originally Posted by Bounder!

Just a stab, Kurfürst is probably the man for this question but looking up the weight of the 109e and 109f and it appears the later is heavier when loaded which might help account for the lack of speed increase over the emil?

Weight certainly is a factor, but for top speed of high speed fighter aircraft the effect is rather small. It matters much more for climb and turn.

[NZtyphoon]

Originally Posted by Kurfürst

But all of this is not so extraordinary or a surprise since the same can be noted when it comes to the Mark I / Mark V / Mark IX Spitfires's evolution. Hell the Mark I. at +12 is supposedly faster at SL than the Mark IX at +15 boost, how come..?

Lack of documentation for this claim noted. Still waiting for data proving the 109E had less drag than the Spitfire I.

[Kurfürst]

Originally Posted by NZtyphoon

Lack of documentation for this claim noted. Still waiting for data proving the 109E had less drag than the Spitfire I.

[ACE-OF-ACES]

Originally Posted by NZtyphoon

Lack of documentation for this claim noted.

Also noted

Originally Posted by NZtyphoon

Still waiting for data proving the 109E had less drag than the Spitfire I.

Yes that would be something to see!

[TomcatViP]

Originally Posted by Osprey

By the time it was allowed to be a fighter those pilots had little intention of being fighters what with the sheer number of escorts to deal with. No, get fast and whip through the formations with those mighty cannon.

In fact, I am pretty sure that most of the airplane shot down by the 262 were Spitfire and Mustang. There is some video on the net showing 262 involve in turning fight. Some are really dramatics. You shld take a look into that instead of preaching endlessly that nothing came close to the Spit in term of turn fight.

Turning is all about changing direction. If your plane is stuck at the limit of his performances there is no chance for it to turn corners. That's why fighters pilot enjoyed speed as the most valuable perfs... until reliable short range missile came

The Mig17 Vs F4 is quite a good example. Pass the Mach 0.9 and then the F4 had the advantage. Especially in high G pull up and vertical manoevre. Exvatly what was teach at TopGun (see the the story of R. Cuningham). An F105 could turn with a 17... Above the mach

Keep in Mind that BFM is all about E not turning circle. It's pretty easy to understand that with the late gen fighters. But so much could be said.