The next few textbook sections covered basic forces of flight, control surfaces, center of gravity, aircraft stability, and here we are at stalls.
A stall happens when the wing can no longer produce enough lift to support the aircraft. The reference point for this condition is called the critical angle of attack. It can happen in various situations, but the clearest to consider is the climb, when the wings are inclined and the air flowing over the wings is less. You can easily envision a breaking point when the airflow around the wing is just messy, and that's the stall point. We talk about it as stall speed, because the cockpit instrument that measures the airflow over the wing is the airspeed indicator, and the airflow needs to be at least VS1 (or VS0 with flaps out) to keep from stalling the wing.
The stall speed can change. More weight, loading the airplane with a CG too far forward, and the presence of ice or other irregularities on the wing can increase the stall speed. Use of flaps decreases the stall speed, allowing slower controlled flight.
Two main types of stalls are practiced during flight training: power-on and power-off. A power-on stall happens when you typically have the throttle in, such as during take-off or a climb. Stalls during this phase of flight when lift is disrupted due to a too-high angle of attack (nose too high) or retracting the flaps too early. Power-off stalls happen when the throttle is out, such as during landing, and are actually desired to be the last thing to happen as you touch down -- you've "bled off" all the speed you can, stall and settle the last inch onto the runway.
No matter the type or reason for the stall, the recovery process is the same: nose down and power in. As the airflow over the control surfaces is quickly restored, return to straight-and-level flight and adjust the throttle to an appropriate setting.
Stalls usually give me sweaty palms. I can totally deal with the concepts involved, and in practice I have recovered them and used them upon landing to my advantage. However, it's the potential for an unrecovered stall to progress into a spin that freaks me out. So I suppose that spins give me the sweaty palms, but stalling is the first step in spinning! General recovery process (check POH for detailed recovery): power out, neutral ailerons, opposite rudder, return to straight-and-level flight. At a typical loss of 500 ft per turn, and a turn happening in just 3 seconds, there's no time to consult an emergency checklist.
Okay, moving on to maneuvers. Climb, descend, turn. Points to remember:
When climbing, the aircraft tends to turn left slightly due to things like engine torque and asymmetrical thrust produced by the twist of the propellor blades meeting the angle of attack. Slight right rudder is used to maintain a straight flight path.
When descending without power, glide speed and angle are preeeeeetty important. The POH will indicate the best glide speed for the aircraft. Upon engine out, the first thing on the checklist is to trim for best glide speed (then troubleshoot); this will keep you in the air the longest while you attempt a restart or select a landing site. Best glide speed can be affected by wind, so for once you'd be looking to land with the wind.
When turning, pay attention to load factor. The increased Gs on the wings decreases lift and increases stall speed. To maintain altitude, some back pressure will be needed. Load factor that goes too high can damage the structure; for the normal category aircraft we fly, they're limited to 3.8 positive Gs and 1.52 negative. Also relevant here is the maximum maneuvering speed (VA) published in the POH; it's the max speed at which abrupt control inputs or turbulence can be tolerated by the airplane.
That wraps up the fundamentals of flight. Next up are the practical matters of reading charts and understanding airspaces, followed by radio communications, weather, navigation and flight planning. These next parts should go quickly, thanks to continue to fly with Jas and being involved with ForeFlight....
