Hello,I know this has been asked before but I cannot actually see an answer in the forum. If it is there apologies.Could somebody please let me know the correct format for making an entry in the ISA Dev/QNH on the Descent Forecast page. I understand what it is for and that standard temp is 15 degrees and what the QNH is but no matter what format I use I get an invalid entry message.Thanks very much for any help.BestDave

Looked in the 747-441 manual I have and didn't find anything. I'll dig round.In fact, the 747-441 manual I have doesn't even mention ISA Deviation! Time for a more current manual I think! :)

Hello Ben,Apologies I am refering to the 737 800.It is in the 737 800 manual, I have read it and it confirms it is modeled but I cannot make an entry. I have tried +06/10.12 - +6/10.12 - +06/1012 - +6/1012 - 6/1012 - 6/10.12 and +6/10.12 there must be a permutation I am not seeing or there is a procedural issue here.Thanks for your reply.BestDave

Hi DaveI havent flown the 800 for a while, but the last time i did, i completed the descent forcast page, but on my fmc the ISA DEV/QNH entry has the QNH part sort of greyed out, so I have only ever been able to input the ISA deviation, it accepts whole positive numbers without the + sign but needs the - sign for negative numbers, but will not accept anything if you do a / then try and input a QNH, so I am assuming the part after the / is not modelled.regardsJohn Calleja

Hi John,I have had a closer look and it does look as though the QNH section is dimmer (only just) than the the Temp section, so I guess that means it is not modelled. I can insert the temp no problem.Thanks for your reply, pointing out the obvious!!!!BestDave