Hello everyone!
So, you probably experienced a stall once in your life. But what exactly is a stall? To find this out, we will first have to understand the four forces, or what makes a airplane fly.
The four forces
In aviation, the four forces are lift, weight, thrust and drag. In a unaccelerated flight, such as straight and level, all forces are in equilibrium. When a 2 ton heavy aircraft is flying level, the wings are producing exactly 2 tons of lift. Not more, not less. The powerplant, which could be anything from a piston engine to a jet engine to a rocket engine, produces enough thrust to get enough wind flowing over the wings, and drag is what slows the aircraft down.
Let’s explain them a bit more:
Lift is what pulls the aircraft up. It is made by the wing, which has a special shape. With this special shape, the air under the wing is slower than the air over the wing. A pressure difference is made, and since high pressure want to go to low pressure, the air pulls the wing, and so the aircraft up. However, what the wing also does is push air that went over the wing down. This is due to Bernoullis theory and Newton’s third law. What ultimately determines how much lift is made is not only speed, but the angle of attack. The angle of attack, or AOA, is the angle at which the relative wind hits the chord line ( a straight line that goes from the foremost point to the rearmost point of a wing). Since all this is complicated stuff where you need a lot of time to understand all of this, we won’t go as much into depth here. In normal flight, the air flows smoothly over the wing, making it possible for the wing to get pulled up and air pushed down. The higher the AOA is, the more lift can be produced, but only if there’s enough speed too. This is because pitch controls speed, and power controls pitch. A aircraft can pitch up but not climb when there’s no speed, and vice versa. However, on this curve is a point where the critical angle of attack(about 16 to 18 degrees on much aircraft) is, and when this point is reached, the air starts burbling over the air, and the air can neither be pushed down nor pulled up. As a result, the wing creates more drag than lift, and the aircraft falls. A pilot can recover from a stall by pushing the stick or yoke down to reduce the AOA. Full power is also required to lose the least amount of altitude. A unfortunately common problem is that the student pilot instinctively pulls the stick up, all the way to his stomach and only worsens the stall, and might even enter a spin. It takes time and guts to override your instincts, since it might seem a bad choice when you’re stalling at 1000 feet to push down rather than pull up. However, there is only one real way to recover form a stall, reduce the angle of attack. Many student pilots think that you can recover from a stall by adding power alone, but this isn’t true. You can get into a power on, departure stall with 100% power and still not recover as long as you don’t push that stick down.
When you’ve got lift and airspeed again, make sure to advance to 100% power (if not done yet) and climb at the Vx airspeed of your aircraft. What is Vx? Vx is basically a v speed where your aircraft will climb the most altitude per mile, rather than Vy, where you will climb the most altitude per minute. You should check and remember your aircraft’s V speed. For example, in a Cessna 172, Vx would be 60 knots and Vy at about 78. Vx is also used in short field takeoffs, where the aircraft should use all power and distance available to clear all obstacles.
The 3 types of stalls
There are 3 types of stalls (as far as I know), these are power on (departure), power off (approach) and spin.
Power on:
A power on stall is a stall where you stall with throttle advanced to wide open. This is common during departures. When climbing out at Vx, make sure you never go below your stall speed. You can find out your stall speed by looking into the V speed information of your aircraft.
Power off
A power off stall is a stall where you stall with throttle closed, sometimes with full flaps. This is common during approaches and short finals, mostly during the base or final leg. Make sure you never go below your VREF or stall speed. This can also happen when closing the throttle to soon when making a three point landing in a tail dragger.
Spin
A spin is a worsened type of stall. This can happen due to a variety of reason, including not applying enough right rudder against P-factor andd all the other left turning tendencies, which get worser at slow flight. In a spin, you, as the name says, spin. To recover, apply full rudder in the opposite direction of the spin, idle power, stick down, and once airspeed is alive again and you got stabilized, climb at Vx. Before you climb out, make sure to have your wings level! This is to get the most lift from your wings. Always check your ADI.
What else to remember
Many student pilots think that you can only stall when you’re at stall speed. But this is not true! Your stall speed can get lower, but only very slightly, for example in a power on stall where the propwash is hitting the root of the wings and gifting lift. But it can also get higher. In a 60 degree turn, you must increase your AOA a lot to not descend. This can crate up to 2 g-forces, making you and your plane double as heavy as it was just a few seconds ago. This can increase stall speed at about 1,5 times. For example, your stall speed can go from 60 to 90 knots in a 60 degree turn. Your stall speed can also differ, based on weight and weather.
That’s it! Now you know a bit more about stalls.
Thanks for reading!
Soft landings, and goodbye!