PERF/POF: Vmp - Vmd (Again)
I know I know....this gets repeated every 6 months or so on here (a search of the forums gave me 5-6 threads to read through) however unfortunately none of them, and not even Google seem to be able to help me.
I don't know what it is - so far everything else I've read in POF/PERF makes sense. But I seem to have hit a wall with this particular area, I must be missing a very simple piece of the jigsaw which would make it click.
I could of course learn the answers in the question bank, but I absolutely hate leaving a topic without fully understanding it and hence why I'm here for a bit of help.
Firstly, how/why is Vmp less than Vmd, in practical terms what is the difference?
One thing I don't really understand in my textbook (Oxford) is how it goes in to a long drawn out explanation of how to calculate Vmp...but on the next page immediately tells you that Vy for a jet aircraft is 1.32Vmd. Where does the 1.32 come from, and how is this related to Vmp according to the prior explanation? It doesn't seem like there was any point in explaining Vmp to me - but there must have been otherwise this whole thing might have made sense.
Lastly, we are told in the glide that Vmp gives the the lowest rate of descent. Again in layman's/practical terms, could someone please explain how this comes to be the case? We are told that in the glide, we simply need to balance the drag with the value of W cos y (I'm using y here for Gamma). This would therefore make me come to the conclusion that the less Drag, the less the value of W cos y needs to be. How can it be that there is a speed (Vmp) which is higher up the Drag curve than Vmd, which would give us a lower descent rate? I might be making this too complicated for myself, I'm just struggling to see how any extra Drag above Vmd in a glide descent could possibly be a good thing.
I think that's all that's confusing me for now, apologies if this all seems a bit simple but I just want to get the basic principle clear in my head before I move on.
Thanks in advance to anyone that may be able to help!