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The Yak and its radiators

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If you are taking the altitude from the HUD there might be innacuracies because it gives the altitude to the ground, and even in a rather flat map like Stalingrad it can change depending on the position in the map, (while the plane is flying level at the same altitude above sea level), also you would need to add the difference between Stalingrad's ground level and sea level. That could explain the differences you notice between flights at the same HUD altitude, as it could mean different actual altitudes above sea level.

What I think it's the most practical way to do these speed tests is to make them in the Kuban map flying over the sea, also being in the Autumn season so you are saved from calculating the TAS at sea level , as the IAS at sea level and 15°C equals TAS, so that's one value you don't need to convert ^^

In my case in Stalingrad in summer at 4500 m above sea level (plane altitude indicator calibrated to standard atmosphere), the temperature is around -8°C. With the Yak-1B without radiators and 90% mixture I could manage 482 km/h IAS consistently (almost 300 mph), repeated it 4 times and didn't have variations.

482 km/h IAS at 4500 meters and -8°C are 613 km/h TAS (almost 381 mph), close to the value I got in my previous test (616 km/h at 4000 meters). If you use the calculator you need to use feet (in meters looks like it doesn't take into account the conversion), otherwise the other parameters are fine to use either imperial or metric. Since we are using altitude above sea level, in Altimeter Setting you have to use the standard pressure at sea level which is 1013.25 hPa or 29.92 inches.
 
 

Edited by -=PHX=-SuperEtendard

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If you are taking the altitude from the HUD there might be innacuracies because it gives the altitude to the ground, and even in a rather flat map like Stalingrad it can change depending on the position in the map, (while the plane is flying level at the same altitude above sea level), also you would need to add the difference between Stalingrad's ground level and sea level. That could explain the differences you notice between flights at the same HUD altitude, as it could mean different actual altitudes above sea level.

 

What I think it's the most practical way to do these speed tests is to make them in the Kuban map flying over the sea, also being in the Autumn season so you are saved from calculating the TAS at sea level , as the IAS at sea level and 15°C equals TAS, so that's one value you don't need to convert ^^

 

In my case in Stalingrad in summer at 4500 m above sea level (plane altitude indicator calibrated to standard atmosphere), the temperature is around -8°C. With the Yak-1B without radiators and 90% mixture I could manage 482 km/h IAS consistently (almost 300 mph), repeated it 4 times and didn't have variations.

 

482 km/h IAS at 4500 meters and -8°C are 613 km/h TAS (almost 381 mph), close to the value I got in my previous test (616 km/h at 4000 meters). If you use the calculator you need to use feet (in meters looks like it doesn't take into account the conversion), otherwise the other parameters are fine to use either imperial or metric. Since we are using altitude above sea level, in Altimeter Setting you have to use the standard pressure at sea level which is 1013.25 hPa or 29.92 inches.

 

 

The problem with variation turned out to be tacview. My IAS readings on the hud are the same each time. 

 

Thats why I posted the screens. It would appear we are getting the same numbers, tacview was the issue. 

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