109 e4 performance

Actually, the only thing that one can deduce from the manufacturer's spec is that the maximum speed for a 109E that were delivered would be at least 475 kph. I would never venture so far as to say that the average of all delivered 109Es would be at 500 kph. We simply don't know. The 500 kph +/-25 kph is just a bandwidth resulting from negotiations between the client and the company.

So the average may be anywere between 475 kph and 525 kph when only consulting the specs.

What really matters is the real obtained speed value for each plane. To know where the average was one would have to measure the max speeds for every plane under the same conditions. As all planes were test flown there might have been abundant data albeit probably not under same conditions (weather, pilot, ...). They might also just satisfied themselves with proving that they can reach the 475 kph.

Now we only have a handfull of test data available, all with max speeds below 500 kph. So unless we find test data that shows that the 109 could reach 500+ kph I would assume that the average was somewhere between 475 and 494 kph.

[Robo.]

Originally Posted by CaptainDoggles

There's no such thing as an exact value in engineering. EVERYTHING has a tolerance.

• That hole you drilled? Only accurate to within ±1mm.
• The elastic modulus of steel? It's a statistical range that depends on the microcrystalline arrangement of the atoms.
• The shear stress of your wing spars? Depends on the cross-section which is not accurate because of tolerances in the manufacturing process.
• Horsepower you get from fuel? Depends on chemical composition, which is again subject to tolerances and impurities introduced when it is refined and processed.

CaptainDoggles - this is pretty much what I was talking about, I would really appreciate having certain variations in parameters and performance (I actually believe such a thing is present in the sim now, at least overheating behaviour...). What I am trying to do is, to come with something constructive, e.g. some numbers usable for the devs, from which these say Vmax ranges for the aircraft in the sim might be calculated.

[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).

[Robo.]

Originally Posted by CaptainDoggles

Fighter Combat: Tactics and Maneuvering

I agree, this book is a gem.

Originally Posted by CWMV

Turn fighting is for suckers. Either initiate the attack with a firm advantage or disengage. Never fight fair.
Hence the need for speed!

Very OT, but can't disagree more. Surely, speed is life (even in turnfight), but a good pilot must know how to swing the plane around if it comes to that. And it does sometimes Different topic I know, but fighting in maneuver (not necessarily turn) is not for suckers but for pilots who know what they're doing.

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.

[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.

[bugmenot]

Originally Posted by Crumpp

Ok, we can ballpark the vicinity of the speeds we should be seeing at each of the settings by using the basic math relationships of power required to power available. Most of you won't know what I am talking about but it works.

For these ratings:

2) Startleistung 1175 PS in 0 m Höhe = 500kph
(zulässige Dauer 1 Min.)
bei 2500 U/Min.

3) Bodenleistung 1015 PS in 0 m Höhe = ~474kph
Kurzleistung (5 Min. Dauer)
bei 2400 U/Min.

Erhöhte Dauerleistung 950 PS in 0 m Höhe = ~465 kph
(zulässige Dauer 30 Min.)
bei 2300 U/Min.

Dauerleistung 860 PS in 0 m Höhe = ~449 kph
bei 2200 U/Min.

That is based on Mtt's contractual performance with the RLM and of course has a +/- 5% and assumes the radiator is in the same position as the 1 minute rating. This is a quick ballpark and it can be refined.

There's typo in the Baubeschreibung: M o t o r l e i s t u n g
http://kurfurst.org/Performance_test...chreibung.html

should be 1045 PS in 0 m Kurzleistung (5 Min. Dauer)
bei 2400 U/Min.

[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?