I would like to really understand why when talking about jets we care about thrust but when talking about propeller aircraft we care about power.
(THRUST)="Just a force"
(POWER)= work/time = force x velocity
I know that even though propeller aircraft are called "power producers" and not "thrust producers" as jets, any aircraft needs Thrust because that's what overcomes Drag. The difference is that a prop aircraft uses the Power of the engine to turn the prop while a turbine engine produces Thrust by itself.
I also know that total drag curve comes from induced drag (decreases with airspeed) and parasitic drag (increases with airspeed), so that is exactly what thrust needs to overcome. The total drag you get at a given airspeed is equivalent to the thrust you need to stay level. That makes a lot of sense.
I have no problem with jet theory when thinking about that and the Thrust required / Thrust available curves.
Why is it different for prop aircraft? Why is the power curve important? I mean, aerodynamically. Because I've seen that total drag curve is also the same as Power Required Curve and I don't understand why.
My first thought is: Engine power is important because that is what the prop will use to rotate and generate Thrust. (Propeller efficiency is directly related with HP and other prop aerodynamic factors). However, even with the most powerful engine, if prop efficiency is poor because of the other factors, we won't get too much thrust and that's the only thing that matters. And one more time, thrust is what makes any aircraft fly forward, so total drag is thrust required, not power.
Vx speed is found where the greatest difference between thrust available and thrust required is. Greater excess thrust equals greater angle of climb. (Got it!) that's very logical for me.
But: Vy is where the greatest difference between Power Available and Power Required is found. What?! Why?! How can the power the engine produces relate with airplane's aerodynamic?? It has nothing to do with that. Vy is best rate of climb, the airspeed at which the airplane will get faster to an altitude. I think that the reason should be related with a thrust/drag ratio.
On the other hand, I know that the Power Curve results from multiplying each thrust value times each airspeed value of the thrust curve. That's the fact, just let me explain why it doesn't make any sense to me...
Power=force x velocity, and we can apply that in different ways. If we were talking about electricity we could say Power is measured in Watts, and Watts= Voltage x Current. Because we are talking about prop aircraft, we should use a power unit like HP (for reciprocating engines). HP= Torque X RPM.
Multiplying the Thrust Curves to get Power Curves would mean that Power= Thrust x Airspeed
What kind of power are we getting when multiplying thrust times the airspeed at which the airplane is flying?
Wouldn't that be something like "Aircraft power = thrust x airpeed" or in other words "the amount of power needed to stop that airplane"? Nothing to do with the engine (which is really the reason why a prop airplane is called "power producer")
I'm very confused, even tired of not understanding the exact reasons behind this after reading what should be sufficient. I think I know what power and thrust are, but I just can't understand the way they relate, and to be more specific, how does excess power affect the aircraft flying in real life, aerodynamically. Why to talk about Power instead of Thrust in any case, jets or props. (It's clear there's a good reason not to, and that's what I want to finally understand). Maybe more realistic examples or comparisons instead of graphs and curves would help.
(But those are not a problem either in case you want to try.) I'm a student pilot and I hope I was clear enough with my doubts and explanations.
(Also with English since Spanish is my native language)