Originally Posted by
actus reus
Energy transfer is also a function of mass. The TAS/IAS you have to wash off is a function of how much above Min Drag (or whatever it is called in the particular aeroplane) before you start into the low speed regime.
Mass appears the formulae for both kinetic energy and potential energy. The mass terms cancel out when you look at the vertical speed needed to get rid of KE at a particular rate. As you note, airframe drag is a huge variable. Engine thrust is also an important variable, as many engines have quite high idle settings at high altitude.