At the rise of aviation, spin was the most fearful and invincible enemy of pilots. (Spin is a spiral descent of an airplane, the spiral having a small radius and the angle of attack being large. It is caused by speed loss and stalling.) If the airplane is not straightened out, it meets with an accident in most cases. Spin was the curse of aviation. Any slight speed reduction or delay in putting the aircraft to gliding in case of engine failure caused the refusal of the airplane to respond to the controls, stalling and abrupt spinning.
Why it happened and why airplanes sometimes recovered from it was absolutely inapprehensible. Nobody knew the reasons.
The man who was the first to deliberately enter into a spin and then to recover from it was Konstantin Artseulov. At that time he was a monitor pilot at the Sevastopol aviation school, the commander of a group of Nieuports. Artseulov arrived at a conclusion that trying to recover from a spin, pilots made one and the same mistake. When the airplane lost speed, abruptly lowered its nose and started spinning, rapidly approaching the land, the pilot instinctively pulled the control trying to raise the airplane nose and to straighten out. This aggravated the situation and the speed reduced even more.
Artseulov did vice versa
On a fine day of 1916, his Newpor-21 took off the land and, after gaining altitude, entered into a spin. After the first turning, Artseulov pushed the height control forward against the stop. That allowed him to gain height sufficient for a stable flight and to recover from the spin.
Artseulov's experiment was a sensation not only in aviation. It was a real victory over the unknown, the victory that gave confidence to thousands of pilots.
The importance of this victory is difficult to overstress.