Thanks for that, too. I understand the maths that fixes the relastionship between VMP, VMD and Best range speed still air once you make certain assumptions about the shape of the drag curve. I'm more interested in the relationship between VS and VMP, which depends in turn on the relationship between VS and VMD, so that I can explain the subject, with examples if possible, to ATPL students. It is always comforting, as well, to find real life data supporting the theory!