TW (pdf, most recent version) p. 84 gives rules for the minimum straight movement between "free" facing changes for ASFs, conventional fighters, and aerodyne craft in atmosphere as a function of their velocity. Additionally, it states that they may expend Thrust Points to make additional facing changes "at any point" except in their first hex of movement or if they have already made a facing change in the hex in question.
When we go to ground maps, per p. 92 the same rules for facing changes are used, except that a new more-detailed table is given in terms of Battletech-scale hexes. Question: do these minimum straight movement values represent only the minimum straight movement between "free" facing changes, or the minimum movement between any two facing changes?
For whatever it's worth, Megamek uses these values for the distance between allowed "free" changes and as a minimum distance before the first facing change, but allows MP to be used to make facing changes every eight ground-map hexes following regardless of velocity. I can't find support for this particular decision anywhere, which prompted my question.
