>>15886772/2
The practical application:
Pitch + Power + Trim = Performance
I will use the C172S for the description because that is what I teach primary instruction in. If I want to hold straight and level, I set 2-3 degrees nose up pitch, 2300 RPM, and trim for 90 KIAS. If I want to establish a climb, I will first pitch the nose up, then follow with power, and then trim for the airspeed I wish to climb at. Usually it is a Vy climb in the 172, so you pitch for ~7 degrees (horizon level with the glareshield), add full power, and trim the controls neutral once 72 KIAS has been achieved. If you trim before it stabilizes, you may trim for an airspeed above or below 72 KIAS, and it will keep trying to pitch for that airspeed. Once you get familiar with the principle, you can add in an approximate trim setting and fine tune from there, but be patient initially. Descents are the same, except more thought must be given to the airspeed.
If I want to descend at the same airspeed I am holding, NO trim adjustment is required, and only power need be reduced. The pitch will naturally fall to capture the airspeed you've trimmed it for previously. If I want to descend faster, initiate the descent with power, and as the nose falls, it will naturally drop lower than its equilibrium and exceed airspeed you've previously trimmed it for. As it speeds up, trim the resulting control pressure out with nose down trim once you've stabilized at the airspeed you want. To descent slower, pull power and hold your pitch until the airspeed drops to where you want it, at which point you relax the back pressure and trim the control pressures out. YOUR job in all of this is to minimize the plane's nose from oscillating back and forth through the use of smooth yoke inputs and timely trimming.
In reality, its a balancing act of adjusting your pitch and power to see a desired aircraft state. You must always adjust BOTH, but trim is only adjusted for new airspeeds.
