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]

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]

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]

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/International_Standard_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)

 

[Olympic]

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

 

[wzgrza]

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

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

 

[Olympic]

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

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