Originally Posted by
JABBARA
however I disagree with the comment "Vmo/Mmo is dependent on weight." No it is not. it is a fixed speed regardless of weight. Below crossover altitude where dynamic pressure is dominating it is given as KEAS; above crossover altitude where shock waves are dominating it is given as Mach No.
Afraid you've misunderstood me.
My point is that VMO and MMO are, as you say fixed absolute speeds.
But if I'm flying on AOA I don't know my speed, just my AOA.
Lets say I'm actually right at VMO (or MMO). If I'm heavy, my AOA may be +1 deg. If very light, maybe -1 deg? So, what is my AOA limit for VMO/MMO? It ends up being a function of weight - alphaMO=f(weight). I dont think anyone would appreciate having to know their weight and look up a chart to know if they had a speed exceedance.
Basically, its very hard to respect a defined speed limit in Knots or Mach if all you have is AOA.