ISA DEVIATION

[Kyle Sanders]

Hello,

 

I am posting here because I use the CRJ2 for 99% of all my flights and the following scenario is applicable to the CRJ2.

 

 

 

With the attached document in mind for a flight from KMIA-KATL in the CRJ2 (i know it is a bit far but just for this example)

 

I have done my load planning and fuel planning. I have figured that my TOW is going to be about 20,000kg.

 

I have looked up the KMIA METAR and it is 25C. Which is 10 degrees Celsius higher than the ISA standard: "15C at sea level"

 

So I figure that the ISA deviation is +10C. (this is the part im not sure if im doing correct)

 

So now I go to that chart and do the math. I see that the 20,000kg goes up and meets the "ISA +10C" line.

 

Where those two meet, I see that it is at FL380. (rounded up for CLB fuel burn)

 

 

Am I doing this correctly?

CRJ Flight Planning LRC.pdf

[cessna729]

Please del this empty post (firewall probs)

Edited December 14, 2012 by cessna729

[cessna729]

Hi Kyle, Yes, that's more or less how I would have used that chart, the only difference is that I would have looked at the forcast winds and temperatures aloft for my intended route,(rather than just the temp at my destination, i.e. most of the route may be alot warmer/colder than the destination), then use that temp (ISA deviation) in your chart.

See here is an ISA chart http://home.anadolu.edu.tr/~mcavcar/common/ISAweb.pdf

Note: ISA at SL is +15C, then decreases at -1.98C/1000ft up to 36089ft (tropopause) when it stays at -56.5C as you climb, hense the "bend in your chart!".

If you checkout this link you will see the actual speed/alt profile of a flight by another aircraft (not a CRJ, but you get the idea) http://uk.flightaware.com/live/flight/EGF3512/history/20121213/1230Z/KMIA/KATL

They filed for FL360 and CRZ'd at FL370, so your planed FL390 is not bad.

cessna729.