ISA Definition

[majorityof1]

It seems as though this would be an easy google but I am coming up short...

What is the difference between celsius and ISA celsius. Moreover, which one is commonly used in weather (ATIS, etc..). Why have two different ones?

Thanks in advance.

[tgrayson]

Originally Posted by majorityof1

What is the difference between celsius and ISA celsius. Moreover, which one is commonly used in weather (ATIS, etc..). Why have two different ones?

Can you quote the context?

I would be inclined to say that "ISA Celsius" is merely quoting the International Standard Atmosphere (ISA) temperatures in Celsius; normally, they'd use Kelvin. Celsius = Kelvin - 273.15.

[majorityof1]

Sure can. I am reviewing the dash limitations and the ambient temperature limit is the lower of +48.9 degrees celsius or ISA +35 degrees celsius. Besides being really hot which one is the Celsius that I know and love from ATIS reports?

[surreal1221]

What is ISA?

And add 35 degrees to that.

So, ISA + 35 = 15+35 = 50C.

Hopefully that clears up any confusion.

There is only ONE Celsius, and ONE Fahrenheit.

[Clocks]

Originally Posted by majorityof1

Sure can. I am reviewing the dash limitations and the ambient temperature limit is the lower of +48.9 degrees celsius or ISA +35 degrees celsius. Besides being really hot which one is the Celsius that I know and love from ATIS reports?

I think this is referring to the fact that the standard temperature changes with altitude.

At sea level ISA+35 = 15+35 = 50C. At 1000' MSL ISA+35 is 48C. At 2000' its 46C. At FL200 its -5C, etc.

The ERJ has a similar limitation. ISA+35 is the max temperature for the aircraft. But max temperature for takeoff is 52C. How is that possible? Its because we can take off at -1000MSL, where ISA+35 is 52C.

[tgrayson]

Originally Posted by majorityof1

Sure can. I am reviewing the dash limitations and the ambient temperature limit is the lower of +48.9 degrees celsius or ISA +35 degrees celsius. Besides being really hot which one is the Celsius that I know and love from ATIS reports?

I agree with Clocks analysis.

[majorityof1]

Well that makes some sense. What does ISA stand for?

[Clocks]

International Standard Atmosphere

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

The basic number to remember (as it relates to those temperature limitations) is standard temperature at sea level is 15 C, and it changes at a rate of -2C per thousand feet you go up in the troposphere (and +2C for every thousand feet you descend)

[IcarusGR]

1.98C just to be exact ... JAA guys understand.

[stoki]

Originally Posted by IcarusGR

1.98C just to be exact ... JAA guys understand.

And im thinking of converting.. this is gonna be a pain in the ass

[IcarusGR]

Originally Posted by stoki

And im thinking of converting.. this is gonna be a pain in the ass

I use 2 but for the exams they will have 1.98 and 2 .... damn JARS.