Flyin'Dutch' wrote:TopCat wrote:But that doesn't change the fact that max(L/D) doesn't happen at Vy, except by accident.
Physics rarely has anything to do with 'by accident'
Well of course, by 'by accident' I was neither saying nor implying that physics is non-deterministic. "By accident" in this context means 'as a deterministic consequence of at least partially different causes'.
I am sure that Vy is not exactly the same as best glide as a power off (of idling engine) airframe is a different airframe than that with a pulling engine, but it will be close.
No one is disputing that it will be close. What is neither obvious, nor shown in anything I've read on the subject, is a relationship between Vy (the airspeed for max(power available - power required)), and the airspeed where L/D happens to be a maximum in the glide, which of course has nothing to do with the engine.
Flyin'Dutch' wrote:Best glide = Vy if Best glide is furthest glide.
... but what is clear, is that this is not so.
Any more detail than this is above my pay grade, so hopefully someone with real knowledge of aeronautics will be along. It would be nice to know in detail why the numbers are close.