Spit/109 sea level speed comparisons in 1.08 beta patch

[MiG-3U]

Originally Posted by Holtzauge

Concerning the French test it looks like very few data points and none at SL as I can tell so your claim that this supports the 500 Km/h seems a stretch.

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.).

[Kurfürst]

Originally Posted by MiG-3U

The facts:
1. Prototype aircraft V15a, tested well before production started
2. Tested speed 493kmh at altitude of 440m, gives 485kmh at 0m

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.

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.

Of course it should be kept in mind that the final E-1 results were corrected to 1.35ata and Standard Day, and resulting in 498 km/h, and that our E-1/E-3/E-4 models have 1.35 ata.

The outliers, like the sealevel speed in the V15a test, are usually caused by measurement errors.

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.

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.).

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.

[NZtyphoon]

On the other hand this thread is about how the Spitfire I and II series performs in CLOD 1.08, which has now been supplemented/superseded by 1.09, not about Kurfurst's interpretation of 109 data which we all know will be skewed in one direction - how about another thread for that?

Fact is neither patch has provided authentic Spitfire performance, with or without +12 lbs, and there are still chronic overheating issues that ATAG_Dutch has helped alleviate.

[Kurfürst]

Originally Posted by NZtyphoon

On the other hand this thread is about how the Spitfire I and II series performs in CLOD 1.08, which has now been supplemented/superseded by 1.09, not about Kurfurst's interpretation of 109 data which we all know will be skewed in one direction - how about another thread for that?

Thread title says: " Spit/109 sea level speed comparisons in 1.08 beta patch"

Updated paper with French trial results included.

[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.

[bugmenot]

Originally Posted by NZtyphoon

Where are the documents

Bf 109 E, LDv 556/3, Flugzeug-Handbuch
http://www.luftfahrt-archiv-hafner.de/messerschmitt.htm

[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.