First, try to visualize a regular spin. It usually happens when one wing stalls while the other is still generating enough lift. This results in a dive where the plane is rotating around its longitudinal axis.
Now, let’s say the tail of this plane is heavier than is should be (due to bad weight distribution or other factor). If it is heavy enough, it may end up being pulled down, causing the plane to be leveled with the horizon, but still falling vertically (while rotating like a boomerang).
If checked carefully, you can notice that all control surfaces (ailerons and stabilizers) will be ineffective, as the air flows perpendicular to them (90 degrees angle of attack).
There is also the Inverted Flat Spin, which is even more dangerous:
For most airplanes out there, a flat spin is an impossible to recover situation, because all pilot inputs will be of no effect.
There are heroic tales about pilots from World War I that had to unstrap themselves in mid-flight and jump from the back to the front seat in order to shift the center of gravity forwards, and therefore recover from a flat spin (I don’t have any reliable sources on this).
Some acrobatic planes can recover from flat spins by using excessive thrust, torque or any other means available. Even in those cases it is still considered a very dangerous maneuver.
Authour – Diego Rodrigues
