Hi, my ATPL text is a little bit confusing on this topic so I hope someone here can help to clear things up.
So far, I've learnt that max range is obtained at 1.32 Vimd and that the angle of attack where this is achieved is constant. So when fuel is burn off during cruise and the aircraft becomes lighter, in order to fly at 1.32 Vimd (and at constant angle of attack), the aircraft will need to fly slower at the same altitude. BUT, as an alternative to flying slower, a lighter aircraft can choose to climb and fly at a higher altitude.
So, my question is, when it chooses to do this, ie, climb to a higher altitude as a result of fuel burn off and becoming lighter, is this aircraft still flying at 1.32 Vimd and at the same IAS as it was before the climb?