Nick 1...the only time Ive ever had to do that,is in the SIM...if you load the box with all the correct #,s it shouldnt be a problem,and personally have never seen it.....I do on occasion check the GW/GWFL on the AIDS page with the Fuel pred page,and the A/C weight on the lower ecam,but as company policy,it,s not required...would be interested to find out why you would do it in the first place(as I only do it out of curiosity)/....PB