ATA in Inches Hg

[Ivan1GFP]

Thanks Mikewint, Biker Babe,

This seems to be workable at the moment. I don't even have to change the spreadsheet I wrote up.

- Ivan.

 

[mikewint]

Ivan, glad i could help, gave you as many significant figures as possible so you can select the precision you require. to go in the reverse direction multiply by the reciprocal of the numbers i supplied

 

[Ivan1GFP]

Thanks Mikewint,

I did notice the precision. As you can see from the spreadsheet, I have already entered in the formula for conversions. The constants are set in separate cells so that I can alter them if the precision is not correct. The 760 mm conversion and metric conversions are not subject to change so they are hard coded into the formulas.

- Ivan.

 

[sibboh]

Another equivalent boost pressure chart that i found. I don't remeber the link where i found it.

 

[razor1uk]

Ooh, stated statistics strenuously striving for statistical supremacy...

Might some slight variances between each nations chosen methods, and the common base between them be ignoring the 'generally accepted' normal/average outside air temperatre within each nation? of which which hasn't been noted.., let alone variations in testing methods, calibration equipment and staff skills.
If the literature can get with a few decimals/whatever, then unless all engine manifold guages are gathered together and tested by one lab under identical conditions, then I don't think things might get much closer than they seem to be getting.

Don't get me wrong though, statistics can be fun, but after to many times going around in circles, they could make you dizzy and infuriated, just thinking..

Doesn't also different lattitudes and regions of the Earth also have slightly different atmostpherical pressures and 'regional quirks' as well as possibly also related to geological compositions and the localised magnetic distortions or a combination of?

 

[Ivan1GFP]

Ooh, stated statistics strenuously striving for statistical supremacy...

Might some slight variances between each nations chosen methods, and the common base between them be ignoring the 'generally accepted' normal/average outside air temperatre within each nation? of which which hasn't been noted.., let alone variations in testing methods, calibration equipment and staff skills.
If the literature can get with a few decimals/whatever, then unless all engine manifold guages are gathered together and tested by one lab under identical conditions, then I don't think things might get much closer than they seem to be getting.

Don't get me wrong though, statistics can be fun, but after to many times going around in circles, they could make you dizzy and infuriated, just thinking..

Doesn't also different lattitudes and regions of the Earth also have slightly different atmostpherical pressures and 'regional quirks' as well as possibly also related to geological compositions and the localised magnetic distortions or a combination of?

You are attributing a motive to me without any basis.

Here is the primary reason why I started this thread:
I work on flight simulator aircraft as a hobby.
I build flight models for them.
The flight models call for engine manifold pressure specifications in Inches of Mercury (US Rating).
I often get data specified in some other rating.
It is useful to be able to do an accurate conversion since by the laws of physics, there must be one.
It is difficult to analyse something if you do not work with accurate data when it is available.
(Imagine doing length comparisions without knowing the exact Metric to SAE conversions. You would not ever be sure of your results.)

We are not discussing the pressure reading gauges as installed in the aircraft.
We are discussing engine specifications, operating instructions and limits.
There ARE NO Regional adjustments because everything is relative to Standard Temperature and Pressure for this planet.

This issue actually was resolved by my spreadsheet a couple years back.

- Ivan.

 

[Vincenzo]

AFAIK almost for the WW2 time there was not a Standard Temperature and Pressure

 

[Shortround6]

If not a standard then a temp and pressure or altitude would be given. There was an international market in commercial and Military aircraft engines going back into the 20s. In 15-20 years somebody would have figured out if the temp and pressures were way off. By the late 30s many commercial engines were being given an "international" rating to try and stadardise things.

 

[Vincenzo]

i think there were national standard, i think ISA was a 50s adoption probably based on previously british standard

 

[FLYBOYJ]

A standard lapse rate had to be around at least since the late 1920s. In 1929 Jimmy Doolittle flew the first instrument flight and one of his instruments known as a "Kollsman Altimeter" that featured a "Kollsman window," the knob on an altimeter used to adjust the instrument for barometric pressure.

So this would have established sea level as 29.92" @ 59F

 

[Ivan1GFP]

Looks like my mention of Standard Temperature and Pressure got a few people going.
That was not the intent.

What I was getting at was that there is precise mathematical conversion between different measuring standards.
All the different countries were trying to measure the same thing: Manifold Pressure or simply Air Pressure.
The British were using Boost Pressure in PSI above some value they used as Ambient Pressure.
Americans using absolute pressure in inches of Mercury.
Japanese were using millimeters of Mercury above some value they determined to be Ambient Pressure.
Germans were using multiples of what they determined to be one Atmosphere of Pressure.
The Russians were using something involving millimeters of Mercury that I don't happen to know.

Any given condition would produce readings in each system. I just want to be able to convert between the various measurement systems.

As stated earlier, the screenshot with that spreadsheet was probably around the last time I had to change it.
The only thing I am still possibly looking for is the measurement system used by the Russians.

Thanks.
- Ivan.

 

[sibboh]

Germans used also and principally ATA or AT (technical atmosphere). 1 technical atmosphere = 0.9678411 * 1 standart atmosphere (atm)
If we use mmHg, technical atmosphere is 735,559 mmHg, instead standard atmosphere is 760 mmHg
Italians used mmHg and ATA. French used mmHg.

 

[sibboh]

Sorry, i had no read all reply. So i repeated things just written.

 

[Fokker D21]

If anyone is interested. I made some formulas some time ago.

BBR = British Boost Rating in lbs per square inch
GBR = German Boost Rating in ATA
ABR = American Boost Rating in "HG

GBR = (BBR/14,223327) + 1,033227

BBR = (14,223327*GBR) - 14,695949

GBR = ABR/28,958992

ABR = 28,958992*GBR

BBR = (ABR/2,036021) - 14,695949

ABR = (2,036021*BBR) + 29,92126

 

[Wild_Bill_Kelso]

Another equivalent boost pressure chart that i found. I don't remeber the link where i found it.

View attachment 228489

Somebody needs to make an extended version of this that goes up to +16 or +20

 

[Joe Broady]

The ATA (Technische Absolut Atmosphare) was designed so that 1 ATA or at = 1 kilogram per 1 centimeter squared. which is an incorrect unit since pressure is defined as FORCE per unit of area and kilogram is a mass unit. Nonetheless it is convertible to other pressure units:

1 at = 1 kg/cm squared
= 14.223343307119565 pounds per square inch
= 0.9678411053540588 atm or standard atmosphere
= 28.95902519867009 inches of Hg (0 degrees Celsius)
= 735.5592400690826 Torr or mm of Hg

According to NIST (US National Institute of Standards and Technology) Special Publication 81, "Guide for the Use of the International System of Units (SI)":

1 kg force per square cm = 98.0665 kPa (exact)
1 lb force per square inch = 6.894 757 kPa (approx.)
1 inch Hg (32 F) = 3.386 38 kPa (approx.)
1 inch Hg (60 F) = 3.376 85 kPa (approx.)
1 inch Hg (conventional) = 3.386 389 kPa (approx.)
1 mm Hg =0.133 322 4 kPa (approx.)

"Conversion factors for mercury manometer pressure units are calculated using the standard value for the acceleration of gravity and
the density of mercury at the stated temperature. Additional digits are not justified because the definitions of the units do not take into
account the compressibility of mercury or the change in density caused by the revised practical temperature scale, ITS-90. Similar
comments also apply to water manometer pressure units. Conversion factors for conventional mercury and water manometer pressure
units are based on Ref. [4: ISO 80000-4]."

Therefore:
1 ATA = 14.223 344 lb per square inch
1 ATA = 28.959 02 inch Hg (conventional)
1 ATA = 735.5591 mm Hg

The values agree with those in the quote above, within one count in the last digit. I followed NIST guidance on rounding to appropriate precision.

International System of Units (SI)

 

[GregP]

Multiply ata by 28.958 to get inches of Mercury ( in Hg).

Take inches of Mercury times (14.696/29.92) and subtract 14.696 to convert from absolute pressure to manifold gauge pressure.

OK, I attached an Excel spreadsheet to convert boost.

Inputs are in Orange border and all the rest of the values on that row convert to the input value. Some are absolute pressure and some are gauge pressure.

The U,S,A, uses absolute pressure. 29.92 i Hg = 0.0 psi boost. We know that one atmosphere is 14.7 psi, which also equals 2.92 in Hg. Since the British use gauge pressure, 1 atmosphere is zero psi boost, and 14.7 psi boost is 2 amtospheres absolute, but only one atmosphere of boost. So, it's 29.92 * 2 = 59.84 in Hg, but only 14.7 psi boost.

 

[GregP]

German ata may have been measured in bars,

1 atm = 101.3 kPa
1 bar = 100 kPa

Therefore,

1 atm = 1.013 bar

or

1 bar = 0.987 atm

You need to specify gauge pressure or absolute pressure. So, is the ata unit gauge or absolute? From the chart above that has been floating around for, oh, 70 years or so, it looks very much like ata is absolute pressure.

29.92 in Hg (U.S.A.) looks equivalent to 1.033 ata or 1.033 "absolute technical atmospheres." That corresponds to zero psig British "boost," which is a manifold gauge pressure reading. The Russian and Japanese used mm Hg (gauge) or mm H2O (absolute).

 

[Daggerr]

From the chart above that has been floating around for, oh, 70 years or so, it looks very much like ata is absolute pressure.

29.92 in Hg (U.S.A.) looks equivalent to 1.033 ata or 1.033 "absolute technical atmospheres.

ata is indeed absolute pressure, that's what the last a stands for. 1 ata = 1 kgf/cm2. 1 standard atmosphere is 1.033 kgf/cm2.

For gauge pressure the German abbreviation is atü (überdruck = overpressure).