Well IAS will change with altitude whereas TAS or GS, depending on wind presence, I imagine those would be the same with 0 wind. Now mb allows one to choose a speed but I doubt that is IAS as on the gauge . Are you saying I can change that in the mb through the realism settings? Yes one can, but I assume that is what one would see on the gauge as well as on 'Z', and I prefer gauge as IAS and Z as TAS or GS. I assume the mb would not depend on aircraft realism settings, as that would be confusing.