I know it can be tricky, especially during the first practical training lessons:

Understanding the influence of pitch and power to the attitude of your aircraft.

The basic approach seems easy: pitch controls the elevator, power controls the engine(s). So far so good. But the behavior of the plane might look different. Wouldn’t it be logic that if you like to climb you just pull the controls and the aircraft gains altitude? It is not wrong at all. But if you simply pull the controls your plane will, indeed, start climbing and after a couple of seconds your climb rate will decrease. Why? Very simple: you need to add power, otherwise your airspeed will drop – and so the (initially) increased lift.

It is all about energy: during straight and level flight the total energy in your system (aircraft) remains constant. For the easy approach let’s assume there is only two types of energy we deal with. Potential energy (your altitude) and kinetic energy (your airspeed). So if we just pull the controls we only convert kinetic energy to potential energy. As long as our power setting remains the same we will become slower but start climbing. In case you like (and you should) maintain a certain speed for climbing, there will be the need for adding power.

Also vise-versa: if you are maintaining altitude and increase power the aircraft will not simply become faster. No, it will start to climb! Now you might ask why: Again, you are adding energy. And the aircraft deals with it. If you do nothing (so you keep the controls in their position) your plane will climb (and make use of this access energy). Only if you actively control the attitude and try maintaining your altitude you will see that the plane becomes faster.

A few words to the angle of attack: as a law of nature – systems tend to go to their state of equilibrium. And so does your plane. Such a state is a certain attitude at a specific trim setting. What does it mean? In a certain trim setting all forces (lift, drag, propelling force and weight) are balanced. By changing the trim setting you change the equilibrium. So all the forces will change as well until they are balanced again. That means that also your speed will change.

Conclusion:

– Pitch (and trim) will change the airspeed.

– You need a certain amount of power in order to keep the energy level constant (so to maintain altitude)

– excess power of lack of power will result in either a climb or a descent

-> Pitch controls speed, power controls rate of climb or descent
Please also have a look at the explanation video posted below:

Or visit the flight training site for more.

I hope this post cleared things up a little, please feel free to comment if anything is not clear – I will try to explain.
In any case: always Happy Landings!