I have a whole aerodynamics demonstration that I like to teach using the sim. The most simple way to think of it is you’re trimming the tail to be neutral at a certain speed.
For example, if you’re trimmed neutral at 70 knots, doesn’t matter if you’re level, climbing or descending; the plane will want to maintain that 70 knots. Do anything to disturb that and it will eventually return to it (after oscillating due to positive static and dynamic stability).
Either way, your job as a pilot is to anticipate the control changes needed to dampen the oscillations incurred by energy changes, then re-trim until control force is no longer necessary.
Here are some exercises you can do on your own to practice:
Exercise 1: Starting point is a level cruise at 110 knots. Goal is to establish a 110 knot descent.
Reduce the power by a few hundred RPM (or a few inches manifold pressure) and the nose will drop until the airspeed re-establishes around 110 knots, assuming you have the altitude to let it do so. Dampen the oscillations and it’ll establish faster.
Exercise 2: Start in a stable descent at 110 knots, at less than full power (like at the end of exercise 1). Goal is to level off and re-establish a 110 knot cruise.
Add power back in and the nose will rise. Dampen oscillations with the yoke until it’s stable. You can play with the power a little to remain level at 110 knots, or just re-trim to until it’s level and accept the new airspeed (the latter is much easier).
Exercise 3: Start in a level cruise at 110 knots (like at the end of #2). Goal is to establish a 100 knot climb.
Increase pitch using the elevator until the speed slows to 100 knots. You should now be climbing. Use the elevator to maintain that 100 knot airspeed, then once stable, trim until controls are neutral. Accept the climb rate. For a higher climb rate, increase pitch to an even lower airspeed (note: below a certain speed (Vy) the climb rate will drop, and too slow you’ll stall). Then re-trim.
Exercise 4: Start in a stable climb at 100 knots (following #3). Goal is to level off and increase speed.
Push the nose down using the elevator and level off. The airspeed will increase, requiring more and more down elevator. Once stabilized at a faster airspeed, re-trim. Accept the new airspeed.
For a variation on exercise 4 (call it #4A), you could aim to maintain the same speed you had in the climb (100 knots), but in level flight. To do this, reduce the power slightly until it’s no longer climbing - maintain level cruise at 100 knots only by modulating the power. That’s a bit tougher exercise.
Exercise 5: If you didn’t do the level-off method in 4A, we’re going start level, at the faster speed described in #4 and slow the airplane back to 100 knots, all while remaining level.
Reduce power by a few hundred RPM. As we learned in exercise 1, the nose will want to drop. Instead, keep it fairly level and maintain altitude by increasing back pressure (nose-up) on the elevator. As it reaches 100 knots, manipulate the power a bit to maintain that speed and level altitude. You’ll likely need to change elevator pressure at the same time - it’s a combination thing. Once you find a combined power setting and pitch attitude that establishes level flight at 100 knots, re-trim.
Exercise 6: Start in a level cruise at 100 knots (from #5). Goal is to establish a descent at 120 knots.
Push the nose down using the elevator (leave the power alone). The speed will increase. Around 120 knots, use the elevator to bring the nose up a little - maintain that 120 knots using the elevator alone. Accept the rate of descent.
Exercise 7: Start in a 120 knot, stable descent (from #6). The goal is to slow the plane to 100 knots, while still descending.
Slow the airplane by using a combination of power reduction and nose-up elevator. Then when the speed reaches 100 knots, keep it there using the elevator alone. Once the speed is stable, trim the forces out. Accept the rate of descent.
Exercise 8 (advanced): Start in a 100-knot-stable descent (like at the end of exercise 7). The goal is to maintain the airspeed but change the rate of descent.
If you want to decrease the rate of descent (slow the descent), add power. The nose will want to rise. Dampen any oscillations, but it should still settle close to 100 knots, but at a lower descent rate. If you add too much power it might level off completely or even start climbing. Conversely, if you want to increase the descent rate (go down faster) at the same speed, simply reduce power. The key here is using power changes to affect descent rate and the trick is to dampen the natural oscillations using the elevator (pitch) until the speed is stable. Notice this is the only exercise in which we’re paying attention to a specific rate of climb or descent (other than during level flight).
You can do the same technique in #8 for climbs, but understand that eventually you’ll hit your absolute ceiling and no longer be able to climb. This is dependent on weight, balance, and density altitude. Can also be affected by improper leaning on a normally-aspirated piston engine.
Caveat: in any of these examples, you still might need to re-trim a little because changes in density altitude will affect your power and lift. The relationship is never perfect from our standpoint. Moreso if the sim is inducing orographic lift from wind and terrain.
If you want to see this in action with a real-time verbal explanation, I’ll do another demonstration in my stream tonight.
