Stick and Rudder also states on page 5 that we normally teach "theory of building the airplane rather than of flying it." Take the Lift Formula, and let's put it into terms the pilot can control in flight. Lift = coefficient of lift x 1/2 air density x true velocity squared x wing area.
When we teach this in ground school, we instantly see the eyes glaze over on over half of the class. Simplified for Pilots, the Lift formula can be shown as
Lift = (better shown as proportional to) Angle of Attack x KIAS x KIAS.
Now we have only two items that enter into the formula: AoA and the Airspeed dial.
(wing area can't be controlled by the pilot in flight, unless flying something like the F-111 with a wingsweep handle and huge double-slotted Fowler Flaps). True Airspeed Velocity and air density interact to get to Calibrated Airspeed (KIAS when adjusted for installation), and the Pilot's handbook of Aeronautical Knowledge (PHAK) figure 5.5 shows a straight line relationship between Coefficient of Lift and Angle of Attack.
Therefore, when in the cockpit, the only way the pilot can control lift is by adjusting either AoA or KIAS.
Note: Throttle does not enter into the lift equation, unless the pilot is trying to maintain a specific airspeed while maneuvering, which requires throttle movement to counteract changes in drag.
Note: Trim does not enter into the Lift equation. All that trim accomplishes is to reduce/eliminate stick/yoke pressure to maintain a specific hands-off angle of attack (which some equate to attitude or airspeed, but trim really just commands a hands-off AoA).
Langewische is correct about elevator position (which equates to stick/yoke position) commanding a specific AoA. But, as always there are some caveats such as:
- Center of Gravity Location (forward vs rearward CG within range)
- Aircraft configuration (flaps, gear, etc)
- Power downwash over the tail.
So, we can't just paint marks on the control yoke rod "green, yellow, red."
There was some talk earlier saying "what can happen if the engine abruptly quits while an aircraft is in a very steep climb". What will really happen is the airplane will rotate downward to maintain the trimmed AoA and will not stall "unless" the pilot continues to pull the yoke backward (which is what nearly always happens in this stressful situation).
There were some other comments about flying a phugoid to show stability. The pitch phugoid is great to show stability, but it also shows the relationship between AoA, speed, lift, and stick/yoke position.
Here's a great demonstration, which is best accomplished in an airplane with both a G-meter and and AoA gauge. Trim the airplane for 1-G, steady speed, level flight. Slow the airplane to a range where not all of the green bars on the AoA gauge are illuminated (I do this around 80-90 KIAS). Pull the nose about 20 degrees nose up, then take your hand off the stick/yoke. Monitor the yoke position--it will revert back to the same position it was before you pulled (I've used a ruler to document stick position). Watch the AoA gauge (it will remain nearly constant), watch the stick/yoke not move, watch the G-meter go to less one when the airspeed is slow (at the top) and more than one when the airspeed is high (as the airplane pulls out). This is because the amount of lift required is constantly changing (L = AoA x KIAS x KIAS), but the AoA is not changing (or changing slightly, due to mostly to momentum).
As for maneuvering flight, the lift equation remains the same. The airplane doesn't care what attitude it is in, just how much lift is required. When you roll into that 60 degree bank (LEVEL, 2G turn, while maintaining constant speed with throttle), the airplane sees a need to generate twice the amount of lift. Since airspeed is unchanged, the AoA must increase to double the lift--this is done by pulling back on the stick/yoke a specific amount to command that AoA.
Is there some lag? yes, Momentum enters into the equation a bit, but the plane still reacts pretty quickly to elevator inputs (especially when at higher speeds). Can you pull so abruptly that things get out of kilter a bit, yes.
Another great demonstration is to get a flight in an Ercoupe, especially an older one with just a one brake pedal on the floor. Slow up, pull the yoke all the way back, you will not stall (maybe you can get close with a super abrupt pull, but then the plane will stabilize out). You can get into a pretty good rate of descent, but the elevator will not travel high enough to maintain a stall.
So, knowing about the physical position that the stick/yoke will reach stall AoA (in the configuration, CG, etc., that you typically fly) will give you another indication of when you are approaching a stall in either 1G or accelerated G flying. (You don't have to know that position exactly, just be aware of the approximate location, kind of like playing a trombone).
I'm sure this will be controversial, but I hope you will think about these comments and try out the maneuvers before commenting. This is not meant to be a discussion on how to build an airplane (the actual aero formulae get extremely complicated, and heck, we can't agree on whether Bernouli, Newton, or Coanda develop lift), but this is meant how to provide tools to the pilot understand what is happening in flight that they have "control" over.