Spit/109 sea level speed comparisons in 1.08 beta patch

[bugmenot]

Originally Posted by MiG-3U

The French test shows about 494kmh at about 550m and and power chart gives about 1010ps at 550m, these values give 482kmh at sealevel with 990ps.

http://www.rolfwolf.de/daten/E4/Emil.html

Auszüge aus Flugzeugdatenblatt Bf 109 E-1, E-3 nach L.Dv.556/3

Höchstzulässige Horizontal-Bodengeschwindigkeit 485km/h

[MiG-3U]

Originally Posted by Kurfürst

Seems there's then good agreement between the German tests with the E-1 at 1.31ata and the French tests with the E-3 at 1.3 ata then even according to Harri's own estimates.

There is no such german tests of the production E-1. Only one test of the prototype V15a at supposed series condition and calculated projected output well before the E-1 was fully developed or out of production line.

Besides the agreement is much better with Holtzauge's calculation, the difference being less than 1,5%.

Originally Posted by Kurfürst

Good point. Since the two brief trials of 467-475 kph you mentioned fell well out of the official and other measured tests, and they note that some necessary corrections were not made (the first trial mentioning that the SL speeds were simply graphically extrapolated to SL, and both trials noting the figures are not yet corrected to guaranteed engine output) it's likely the scatter is caused by measurment errors.

There is no official tests of production planes to fell of, I quess you are refering the tests of the prototype V15a again. The power output is actually not relevant because these were real production planes performing as delivered, no need to assume some kind of projected power.

All the tested production planes (Wnr. 1792, 1791, J347, 1304) had speeds within range of 18kmh and variation is less than 2%.

And please, don't reply with something on the prototype V15a again, it's a dead horse like the 100 octane discussion. If you have real tests on real production planes, then we have something to discuss.

Originally Posted by Kurfürst

Which can be entirely ruled out given the fact that the low altitude measurements with the V15a were done on a four way record track, the aircraft having flown in four directions, and the (known) distance covered was timed. This method is by far the most accurate and eliminate all possible instrument errors.

There is allways chance of error regardless type of the test; error in timing, error on writing results, errors in calculation etc. If there is an error, it's likely in the outlier.

[NZtyphoon]

Originally Posted by bugmenot

http://www.rolfwolf.de/daten/E4/Emil.html

Auszüge aus Flugzeugdatenblatt Bf 109 E-1, E-3 nach L.Dv.556/3

Höchstzulässige Horizontal-Bodengeschwindigkeit 485km/h

Where are the documents, rather than home made graphs and a translation?

http://www.wwiiaircraftperformance.o...dbookcurve.jpg

Data from the 109E-1/3 handbuch: Actual (wirklich) speed shows 450 km/h or 279 mph at sea level; indicated (anzeige) = 500 km/h 310 mph.

[Holtzauge]

Originally Posted by ACE-OF-ACES

By the way your name rings a bell too.. I seem to recall seeing your C++ stuff a few years back.. Very neat stuff! I have some of Henning Rush's stuff posted at my website.. i.e. www.flightsimtesting.com and would love to post some of yours too! What format is your output files? Simple text I assume? Could I get a copy?

Had a look at your site and it looks promising! Will be even more interesting when you add some more aircraft. I can certainly do some simulations if there are some particular scenarios you would like to see and yes, the output is in text format that I copy to Excel to produce the charts.

I did post some simultion results a few years back about Fw190 dive and compressibility effects which unfortunately came to the attention of a certain Herr Crumpp whom I believe is a mutual aquaintence?

[Holtzauge]

Originally Posted by TomcatViP

Well... and naming the eq. that you use is that so much classified that you can't even do it?

There is no single equation behind it and it's not a FEM program if that is what you mean. The C++ code is an extension of the code I wrote for my masters thesis (In Simula!) which was to access the influence of external stores like missiles etc on the performance of jet fighters. This meant I had to convert it to C++ and add some functions to handle prop performance and ram effect on engine. The prop function is dependant not only on advance ratio and density effects but also includes Mach effects due to prop tip speed. The same goes for the drag which rises steeply at typical dive Mach like 0.7 and upwards. Not much use in simulating dive performance otherwize. This shortcoming not to model compressibility effects is a major flaw in both IL2 and CloD IMHO.

[Holtzauge]

Originally Posted by MiG-3U

The French test shows about 494kmh at about 550m and and power chart gives about 1010ps at 550m, these values give 482kmh at sealevel with 990ps.

The outliers, like the sealevel speed in the V15a test, are usually caused by measurement errors. And given the fact that speeds match better with other tests at high altitude, it is probable that something is not right in the V15A measurements (error can be anything; failing device, typing error, calibration problem etc.).

Yes, the 498 Km/h SL figure for the V15s prototype does not make sense if you assume that the circa 570 Km/h figure at altitude is correct. I have simulated a number of different aircraft and usually it is enough with one data point with both power and speed and then you can with good correlation to historical data work out the others if you have the power/alt curve. This has worked for me on the Fw190A&D, Spitfire 1,5&9, P-51, P-47, Me109F, G and K etc and using the same principle yields around 475 not 500 Km/h at SL for the Me109E.

I also agree that unless some new data on series aircraft emerges that changes the matter, I'm going to stick with the 475 Km/h figure since I'm more inclined to believe the Rechlin reports on actual production aircraft for tuning my model rather than trusting some prototype data or a figure from a Baubeschribung from "circa 1939".

Finaly, Seeing Kurfurst's has been actively promoting the 500 Km/h story I never expected to convince him. My sole purpose with posting my chart was to provide an alternative analysis and in the end it's up to the readers what data they think is more credible and knowing the majority of users want historical not agenda driven performance I can only hope 1C will not be duped.

[Kurfürst]

Originally Posted by Holtzauge

I'm more inclined to believe the Rechlin reports on actual production aircraft

Pity we have not seen any.

Originally Posted by Holtzauge

My sole purpose with posting my chart was to provide an alternative analysis and in the end it's up to the readers what data they think is more credible

A home made chart of which's maker even refuses to share the base data vs. properly flight tested, calibrated, corrected and guaranteed flight test data.

It is going to be a tough call I bet.

[Holtzauge]

Originally Posted by Kurfürst

Pity we have not seen any.



A home made chart of which's maker even refuses to share the base data vs. properly flight tested, calibrated, corrected and guaranteed flight test data.

It is going to be a tough call I bet.

Yes, seeing the sniping is coming from someone with a documented history of always taking the inside envelope of any allied data and the outside envelope of any Me109 data I'm sure it will be a close call.

Over and out.

[fruitbat]

Originally Posted by Kurfürst

vs. properly flight tested, calibrated, corrected and guaranteed flight test data. (of a prototype)

It is going to be a tough call I bet.

yep, it is.

by the way, isn't it peaceful here at the moment, shame its going to end soon......

[Glider]

Does anyone know the differences between the V15 and production E-3. I assume that 20mm guns, armour plate, self sealing fuel tanks, bullet resistant glass, were not included. Did the Germans install additional equipment to the 109 similar to Spit 1's compared to the Spit prototype, such as different radios, IFF, emergency equipment, bulges to accomodate the 20mm. All these things presumably would have impacted the performance to some degree.