109 e4 performance

[Robo.]

Originally Posted by robtek

I really can't understand why there is still disagreement about the max. speed of the Bf109E.

When the manufacturer calculates a speed for a model and verifies this with flight-tests, and sells the plane according to this values

There is no disagreement at all. As you say, manufacturer calculated speeds in certain conditions, but he never verified them with flight tests. The main reason being it was not really possible, the data are simply theoretical speeds. All that is good enough, but these speeds never achieved in any actual empirical tests (again, various reasons). The problem is that this is a matter of opinion. Mine is that average E-4 with DB 601Aa engine was well capable to reach 500km/h at 1.45ata ('1) (take-off power at sea level, rads fully closed or 1/4 open), but it would be unwise to model all Emils in the sime like that or even worse, using more optimistic data (say 525km/h) for average plane in the sim. Therefore, I was trying to come with some rough guideline and some numbers for rated power for bothe engines in questions. I believe this can help getting the FM right (regarding how the real thing flew including certain variability) more than comparing each other opinions.

I pretty much agree with 41Sqn_Stormcrow's insight above, Crumpp's calculated data are still very close and good enough for the sim (Aa engine).

Well basically we can say: the 109 as modelled in the sim is too slow (there is no speed variation in any plane so the in game 109 can be supposed to represent the average 109). It is even slower than the slowest ever performed flight test (on a special unit). It is well below the minimum spec. Conclusion: the 109 should be faster by a good deal. As there is currently no test data concluding that the 109E could reach 500 kph and the best ever obtained data in the tests that we dispose of is 494 kph the average should be in the middle of the 475-494 kph range for the average 109. This is about 485 kph. In case the devs will implelemt a variation they should apply a gaussian with average value 485 kph and 1 sigma = (485-475) / 3 = 3.3 kph.

Now I hope we can have a similar evaluation for all the other planes including the Spit 2a that seems to concord with some data given but we also should evaluate if it is based on average values or if it is based on test data that was more on the upper bandwidth than on the lower (or vice-versa). There is currently no clue whether the Spit 2a is representative of an average Spit2a or a lesser or better performing individual plane.

[robtek]

I still would say that the average, fresh from the factory, Bf109E should be able to reach 500km/h!

Of course the speed later on varies, depending on how the machine is handled.

If the machine is handled carefully, always warmed up enough and never exceeded the power ratings and also didn't have

accidents during the ground handling or damage through enemy action, then it might be even better then during the acceptance trials.

Otherwise, if one or more of the above conditions isn't met, the speed will be lower.

But then, if the speed and/or handling has detoriated to a given point, the aircraft will get a major overhaul or be sent to training units or wrecked.

If there is a variation from the factory-set standard speed it must work both ways, or it is biased, imo.

[Robo.]

Originally Posted by robtek

I still would say that the average, fresh from the factory, Bf109E should be able to reach 500km/h!

I agree, the problems is how to model this in the sim. Crumpp replied earlier, and I have no objections at all, because that sounds very reasonable, the max speed stated was reached on an Aa engine, 2500RPM 1.45ata, rads 1/4 open (or closed). That plus some variation modelled, e.g. some Emils would do slightly more and some slightly less - that would be great.

[CaptainDoggles]

Originally Posted by Robo.

There is no disagreement at all. As you say, manufacturer calculated speeds in certain conditions, but he never verified them with flight tests.

I'm pretty sure we've just spent 4 pages establishing that not only did Messerschmitt conduct test flights to verify their numbers, but so did the RLM. Use logic for a second: If, as you say, nobody did tests between the aircraft coming out the door of the factory and going to operational service, then how did the RLM know they were getting what they paid for? How did Mtt know that the RLM wasn't trying to cheat them?

Answer: They did flight tests. We just don't have the documentation.

The main reason being it was not really possible, the data are simply theoretical speeds.

Are you seriously saying it was "not really possible" for Messerschmitt to conduct flight tests? These are not theoretical speeds, it's a requirement that Messerschmitt was obligated to meet.

but these speeds never achieved in any actual empirical tests (again, various reasons).

I see your agenda beginning to show. What you mean to say is: We don't currently have access to any empirical tests where this performance was achieved. Or perhaps: The (very very small) sample of aircraft that made their way into the hands of the Allies did not achieve rated performance.

[Kurfürst]

Indeed Messerschmitt did proof checking of their airplanes. I've only seen one such paper, this is for Erla licence-produced Bf 109Gs. You can see the nominal (guaranteed) performance with a thick line, and also the upper and lower tolerance on performance (+/- 3%) for acceptance.

The dots are measured values for 13 individual planes - some are a bit worse, some are bit above the specs, and there are couple that will be rejected until the plane is brought up to spec.



The story in short is, however, the nominal specs are guaranteed to be reached within limits. An aircraft is just like any product, the producer has liability to meet the agreed contract, no matter when, and where. In Germany, the LW had its own separate quality control organisation, the BAL. They were pretty strict right until the war's end. Reading Hans Fey comments on Me 262 testing, the lower limit for the Me 262 was 830 (nominal/guaranteed spec was 870 kph), they did accept planes down to 825 but that was it; anything lower would be rejected. And that was in 1945, when the Germans would need as many jets as possible.

http://www.lwag.org/forums/showthread.php?t=484

Now the bottomline: As shown in the Baubescreibung Me 109E document, the specs for the 109E were 500 km/h at SL and 570 km/h at altitude with 1.35 ata or full power and the DB 601Aa engine, within +/- 5 % of that for each individual plane. We have exactly that aircraft modelled in the sim, so E-1, E-3 and E-4 should satisfy these specs. If they are modelled different, its wrong, end of story.

[Robo.]

Originally Posted by Kurfürst

Now the bottomline: As shown in the Baubescreibung Me 109E document, the specs for the 109E were 500 km/h at SL and 570 km/h at altitude with 1.35 ata or full power and the DB 601Aa engine, within +/- 5 % of that for each individual plane. We have exactly that aircraft modelled in the sim, so E-1, E-3 and E-4 should satisfy these specs. If they are modelled different, its wrong, end of story.

They actually satisfy these specs on the very bottom end. They should certainly be slightly faster on the deck. My point is let's get some figures that might be acceptable for the sim for both Emil engines on all ratings, ideally for all rated powers mentioned in the chart.

Interesting info about the Erla Gs, seen that one before on your website. Does not say anything about top speed being tested on the deck and I can't read the doc good enough to see the actual ata settings etc.

[Robo.]

Originally Posted by Kurfürst

Now the bottomline: As shown in the Baubescreibung Me 109E document, the specs for the 109E were 500 km/h at SL and 570 km/h at altitude with 1.35 ata or full power and the DB 601Aa engine, within +/- 5 % of that for each individual plane.

That's for DB 601Aa indeed. The problem is obviously the huge tolerance of 50km/h - and also, I can't seem to find anything confirming the ata used to achieve that speed. Was it Bodenleistung or did they push it on 1.45ata? Do we know? Makes quite a difference.

Originally Posted by Kurfürst

We have exactly that aircraft modelled in the sim, so E-1, E-3 and E-4 should satisfy these specs.

It's not that easy I am afraid - the Aa and A-1 were slightly different. We don't know which engine is modelled in the sim for each subvariant. That's why I am trying to get some numbers together for both.

[Robo.]

Originally Posted by CaptainDoggles

They did flight tests. We just don't have the documentation.

Of course they did, but did they really strain a brand new engine to verify the max speed on the deck? If you have any further information about the tests conducted by RLM / BAL in order to accept an airframe they have paid for? That would be great to know, but using logic again, would their test pilots push the new a/c to its limits? I believe they would not and if the plane performed within limits, they were happy.

Originally Posted by CaptainDoggles

Are you seriously saying it was "not really possible" for Messerschmitt to conduct flight tests? These are not theoretical speeds, it's a requirement that Messerschmitt was obligated to meet.

No, I never said such thing. I never stated that Mtt failed to deliver what they were legaly bound to. I said they most probably did not perform extensive tests to prove our point. The fact is, no matter what test you look at, no aiframe ever managed to reach the speed in the Mtt chart. That brings you straight back to the beginning of this discussion.

Originally Posted by CaptainDoggles

I see your agenda beginning to show. What you mean to say is: We don't currently have access to any empirical tests where this performance was achieved. Or perhaps: The (very very small) sample of aircraft that made their way into the hands of the Allies did not achieve rated performance.

I've got no agenda at all, I only have interest in aircraft portrayed in the sim and I enjoy discussing them. I said - any many would agree - that the tests available are far from being representative (for various reasons). I also said that the Mtt data is theoretical and can be considered optimistic in relation to the real life performance. Many would disagree and I respect that, especially if that's supposed to be a performance of Aa engine on take off MFP ('1 rating) - fair enough.

I tried to get some figures to the respective rated power of both engines in question in order to establish some base. I find it interesting and I enjoy thinking about such details. There is nothing more to that, perhaps except my wish to have the a/c in the sim as close to the real thing.

What is your opinion on the actual figures, CaptainDoggles?

[CaptainDoggles]

Originally Posted by Robo.

Of course they did, but did they really strain a brand new engine to verify the max speed on the deck? If you have any further information about the tests conducted by RLM / BAL in order to accept an airframe they have paid for? That would be great to know, but using logic again, would their test pilots push the new a/c to its limits? I believe they would not and if the plane performed within limits, they were happy.

It's not "straining" the engine if that's what the engine has been designed to do. The engineers say "you can run at XYZ power settings for 5 minutes." Why would the RLM pay for aircraft they aren't sure can meet the contracted obligations? They must have verified that the aircraft can deliver. It's a simple fact, and continuing to cover your ears and sing LA LA LA LA in face of this fact makes me think you are just another forum troll.

No, I never said such thing. I never stated that Mtt failed to deliver what they were legaly bound to. I said they most probably did not perform extensive tests to prove our point. The fact is, no matter what test you look at, no aiframe ever managed to reach the speed in the Mtt chart. That brings you straight back to the beginning of this discussion.

Either they tested enough to ensure the required performance was being achieved or they did not; there is no middle ground. Either the aircraft met the requirements or it didn't. There is no middle ground. You can't say "I'm not saying they didn't deliver what they were required to deliver" in one breath and then say "they didn't do extensive testing" the very next. HOW DID THEY KNOW WHAT THEY WERE DELIVERING IF THEY DIDN'T VERIFY IT WITH TESTING?

And again you're trying to make it sound as if every single test ever conducted on the 109E shows it not meeting proper speeds. Guess what? We don't have the data from every test ever. Stop trying to re-frame the issue based on your agenda.

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I'm done engaging with you on this subject. You next post is going to be another one saying that the contractual obligations were actually just imaginary, theoretical numbers and blah blah. I don't have the patience to repeat the same facts over and over and have somebody just ignore it and say "but I think it's this way" so I will leave you to it.