DEFINITIONS:
Check the explanation of the different forces in the post: reciprocating engine take off
Total Drag (D): As we will see later, on the principles of flight subject posts the total drag is the result to sum two different kinds of drags, called parasite and induced drag.
As you can see from the picture above the minimum of the total drag curve is where the induced drag is the same as parasite drag, and it is only reach at certain speed called minimun drag speed.
Thrust (T): force generated by the power plant, which decreases slightly with speed due to slippage of the propeller.
Power (P) : is the work per time unit ( P=W/t). Let´s change this formula in an useful way for us. Work is Force multiplied by distance ( W=F*d) so P=F*d/t, we also know speed(v) is distance (d) divided by time (t). Our power ecuation finish beeing the force multiplied by speed P=F*v.
Available power (Pa) : Is the power of our engine. Its ecuation P=F*v, where the force in this case is the thrust and the speed is the true air speed. P=T*TAS.
Power required (Pr): It is the power required to win the drag in a specific speed. P=D*TAS
FACTORS THAT AFFECTS THE POWER CURVES :
Weight: if the weight increases
Density Altitude : ( check Density altitude definition) If DA increases .
Configuration : Flaps and landing gear.
Wind : It doesn´t have any effect neither the Pa nor Pr