>>1588677The theory: when an aircraft is stabilized in a climb, descent, or level flight, the forces are balanced. The confusion behind "pitch for airspeed, power for altitude" is often a lack of understanding behind how the aircraft is trimmed. "Power for altitude" is also a bit inaccurate; the reality is "power for climb/descent rate." Trim is used to hold an airspeed, and the power is used to establish the climb rate. If you are trying to hold level, the desired climb rate is zero.
If I have trimmed the plane to hold 90 KIAS/level, an addition of power only will result in an increased airspeed--initially. If I did nothing but add power and sit back, the aircraft would respond initially by increasing speed. The increased speed results in an increase in lift over the wings, which will result in a climb. The aircraft will oscillate, trading speed for climb rate, and vice-versa, until it finds its equilibrium. If you wait long enough to see it stabilize without touching the yoke, you will see it stabilizes at the original airspeed, 90 KIAS. If I am stabilized at 90 KIAS/level and then spin the trim wheel down (nose up trim), the aircraft will climb--initially. Over a short period of time, the aircraft will trade altitude for speed and vice versa until in finds its equilibrium again, which will be at some arbitrary altitude where it maintains a constant airspeed that corresponds to your new trim setting. It will not hold the original altitude, but rather the new airspeed you've trimmed it for. Something that is often demonstrated to students is what's called an elevator trim stall; this stall is a result of slowing the plane to an approach speed, trimming for that speed, and then advancing power to full. The aircraft will abruptly pitch up to seek its equilibrium, but before the nose can oscillate back and forth the critical AoA is exceeded, and the buffeting/stall occurs. Ask your instructor to do one, I bet they haven't since their CFI ride. 1/2
