Sinking Planes - Do they create Lift?
Lets exaggerate a possible situation how an airplane in flight adjusts its own lift to its own weight.
First have the airplane flying straight and level at cruising speed. The airplanes lift and weight are in equilibrium. More lift than weight it would balloon upward. More weight than lift it would sink. Since it is flying straight and level it is "in balance."
Keeping the planes attitude exactly as it was in straight and level flight reduce the speed by twenty miles per hour. Using the controls keep the nose of the aircraft, relative to the horizon, exactly where it was in straight and level flight.
To see what happens, in just a fraction of time, let these events seem like they take minutes to occur.
If everything remains the same (attitude, relative wind, angle of attack) the wings move through the air at a slower speed and develop less lift.
If you have a 3,500 pound SeaBee and it is only developing 3,000 pounds of lift force it does what a stone does - it drops.
It doesn't drop nose down because you, the pilot, are maintaining the attitude exactly as it was in straight and level flight. You are not allowing the attitude to change with respect to the horizon. The plane does not descend, it falls.
A plane, like a falling stone, falls slowly at first, then falls faster and faster because of gravity. If nothing else happens gravity acts on the 500 pound difference between the weight of the SeaBee and the 3000 pounds of lift force until the airplane crashes into the ground.
Something does happen to stop its falling like a rock. Remember, the SeaBee is sometimes referred to as "The Flying Rock" for it tendency to enter a steep glide angle after you cut power for a landing.
All of the above happens so fast (remember we delayed the events) the plane falls only a few inches. It finds a cushion of new lift and what creates this cushion is the aircraft's sinking. How does this happen?
As the airplane moves downward through the air as well as forward the relative wind now blows at the wings as well from in front. The Angle of Attack becomes greater even when the attitude of the plane hasn't changed. Angle of Attack is the angle at which the wing meets the air. The greater the Angle of Attack means that more lift is created. As the plane reaches a sinking speed at which the Angle of Attack is so high that lift forces are now equal to its weight and the plane acts like an aircraft again.
If the power is maintained at the level you reduced it to the aircraft recovered its equilibrium in descent and it will stay in descent. It is a steady descent.
This is a "Power Descent" much like a modern commercial jet that cuts power many miles from the airport as it begins it approach.
You see, a sinking plane does create lift!
