Hey guys,

 

Lastly I was looking around for a tool which would let me calculate the ISA temperature deviation to input into the DES FORECAST page of the FMC, but I couldn't find any.

 

I decided to create my own excel sheet, which you can download here: http://dl.dropbox.com/u/3680035/ISA.xlsx

 

What I do is the following procedure, and I would like to get that validated by you guys, preferably by someone with real life experience in that domain. I perofrm this procedure between 100nm and 50nm or so prior to TOD:

 

1) I bring up the aloft wind data for my flight plan in Active Sky 2012

2) I bring up the FMS LEGS page, and choose 3 waypoints for which the VNAV calculated altitudes are close to the available AS2012 aloft altitudes. I mostly take 30000, 12000 and 6000 if possible.

3) I input the wind info for these waypoints in the DES FORECAST page

4) Then, since the AS2012 info also contains temperature info next to the wind data at each altitude layer, I fire up my Excel sheet, put the temp readings for these 3 waypoints next to the correct altitudes in the Actual Temp column. The Excel file basically then calculates the average deviation from the ISA temps, and I use this rounded figure as input for the FMC in the ISA DEV field of the DES FORECAST page.

 

So, two questions:

 

1) Is this procedure okay ?

2) Is the Excel sheet attached performing the correct calculations ? And are the ISA values correct ? I found them somewhere on the web (not exactly sure where).

 

If everyting looks fine, I plan to upload the sheet to the AVSIM library.

 

Thanks for any input / comments.

 

TJ

Excel isn't attached, might not be a permitted attachment. You can put it in the AVSIM library.

 

I suspect that minor deviations are insignificant, probably looking for +/- 10 or greater, rounded off to the nearest 10 (be my guess).

Thanks,

 

I've put it in my dropbox folder for public download. I'd like to have it validated first by a few people here before I upload it in the AVSIM library

hmm, seems like not much interest for this...

I'd say that most people can't tell if it's right. Of cause I could say "hey, you've had a super idea", but that wouldn't answer your question. I beleave that's why not so many people answer.

 

Anyway it is a great idea to do such a sheet.

Nice idea but it's already been done in the form of a universal aviation calculator called adacalc

available free here: http://www.aero.sors.fr/adacalc.html

vololiberista

oh, thanks for the link, didn't know about that tool.

 

Will check it out

I found this to be great.. very helpful.. thanks for the spreadsheet