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Crumpp 10-26-2011 07:59 PM

Quote:

"Intake pressure".

1 ata is a technical atmospheres (at = technical atmosphere, a = absolut) and 1 at equals 735mm HG. Which makes 990mm 1.35 ata.

1 atm is a physical atmosphere and 1 atm equals 760 mm HG.

Some experts can't tell the two apart and come up with 1.28 ata for 980mm, which is wrong.
Well please, read the French report and enlighten us as to what units the French are using for pressure....

If you are as smart as you think then Google French units of measure.

While the French did use metric, they had their own unique system.

http://en.wikipedia.org/wiki/Units_o...ment_in_France

I don't know what they used but it is not the German Technical Atmosphere and the test was not flown at a 5 minute rating for the duration.

Pffft.....back to ignoring you until you have something to contribute.

41Sqn_Stormcrow 10-26-2011 08:16 PM

His reply was on a bad tone but he might be right with respect of atm being not equal to ata. I myself was not sure if atm = ata that's why I used atm for my calculation.

Unfortunately there is little information about the outdated ata but 1 at (technichal atmosphere = pressure produced by a column of 10m water) is equivalent to 735.56 torr (almost identical to 735.56 mmHg). ata is with a reference point of 0 (I assume 0m that is sea level), so this would be the pressure produced by a 10m column of water at sea level. That's what wiki told me.

I am quite sure they used the ata gauge in the plane to measure it and then translated it into mmHg.

There is one minor uncertainty with respect to the French measurement of the manifold pressure however. The mmHg values depend on the knowledge of the density of mercury. This knowledge may have evolved since ww2 so there is a slim risk that they used a different mercury density for their mmHg units. However I think there is quite a weak chance that knowledge on density of mercury evolved so much that the mmHg values would be impacted by this to the precision that is of interest here.

So basically the French obtained 494 kph at 600m with 2400 rpm and 1.346 ata.
Extrapolating pessimistically to 0m they would have obtained 478 kph at 0m with 2400 rpm and 1.332 ata.

The ingame performances are still enormously off these values.

Crumpp 10-26-2011 09:01 PM

Quote:

So basically the French obtained 494 kph at 600m with 2400 rpm and 1.346 ata.
Where do get that? The French NEVER used the German technical atmosphere.

The French were instrumental in forming the ICAO in 1912 and adopting a standard atmospheric model of that organization, the ISA.

The ISA uses 760mm as 1 ATA.

Once more, the 1.28 corresponds to the 1.3 ata rating. There is NO 1.35ata rating cleared for the DB601A according to any documentation I have seen.

Al Schlageter 10-26-2011 09:10 PM

I suggest looking at this link for Pressure units http://en.wikipedia.org/wiki/Atmosphere_%28unit%29

Crumpp 10-26-2011 09:25 PM

Quote:

So basically the French obtained 494 kph at 600m with 2400 rpm and 1.346 ata.
Extrapolating pessimistically to 0m they would have obtained 478 kph at 0m with 2400 rpm and 1.332 ata.
READ the report!! (You are not the only one either, I did not pay attention to some details either)

The limitations of their own instrument measurements:

Quote:

Due to that, there is an uncertainity about the results. This uncertainty is about 2 to 3%. Thus maximum speed is 570km/h +/-15km/h.
The data is not converted standard conditions.

Quote:

Nevertheless, during the level flight testing done under 5000 meters (external temperature = +6°C on ground
and -17°C at 5000 m.)
If you do convert it to standard conditions then the French conclusion is correct:

Quote:

In general, the first tests made at the Center concerning the
Messerschmidt 109 appear to confirm the performances claimed by the
Germans.
http://kurfurst.org/Performance_test...formanceT.html

Robo. 10-26-2011 09:30 PM

Crumpp calm down dude :o

Crumpp 10-26-2011 09:34 PM

Quote:

I suggest looking at this link
http://en.wikipedia.org/wiki/Interna...n_Organization

http://en.wikipedia.org/wiki/Interna...ard_Atmosphere

p0 sea level standard atmospheric pressure 101325 Pa = 760mmHg....

There is nothing that says WHAT the French used on that report so this whole line of discussion is a complete sidetrack.

Crumpp 10-26-2011 09:43 PM

Quote:

Crumpp calm down dude
I am calm. I just think it is very funny that in all these discussions, the documentation gets ignored by so many and speculated upon so much.

It is what it is and the answers are written in black and white.

There is no need to guess or offer opinions. The report flatly states the data is raw and not converted to standard conditions.

It was flown at a 5 minute rating. We can speculate until the cows come home about which of the 5 minute ratings were used.

980mmHg/760mmHg = 1.289 or 1.3 ata or 1% error

990mmHg/735mmHg = 1.346 ata or 1.35ata or 1% error

It does not matter because in the end, nobody knows for sure.

It is a fact, if you convert the French data to standard conditions, it very much agrees with Mtt's published mean performance of 500kph at 0 meters with a -/+ 5% range.

41Sqn_Stormcrow 10-26-2011 09:46 PM

I dunno but you sound a bit excited.

Al Schlageter 10-26-2011 09:59 PM

Quote:

Originally Posted by Crumpp (Post 354833)
There is nothing that says WHAT the French used on that report so this whole line of discussion is a complete sidetrack.

No it doesn't but it does give info on conversions.:)


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