The unstallable plane that stalled

> If the angle of attack exceeds the permitted limits, some yaw disturbances appear around alpha 25-28°, and at alpha 28-30° there are weak pitch-up tendencies. If the stick is moved forward to counter the pitch-up, the aircraft returns to normal alpha, possibly after overshooting up to alpha ~50°. Note that the angle of attack instrument only shows the area -4° to +26°.

> If the stick movement forward at the pitch-up is too small or is made too late, such that the angle of attack does not immediately decrease, the aircraft departs into superstall or spin. If the pitch-up occurs without aileron input, the departure usually results in superstall. If the pitch-up occurs with any aileron input active, the aircraft is affected by adverse yaw and the likelihood of a spin increases.

In addition to the superstall, the aircraft has two spin modes, in the flight manual referred to as flat and oscillating. The difference is basically the rotation speed and if there are oscillations in pitch and/or roll or not. The recovery is pretty conventional:

> In superstall or spin the pitch authority is good, which eases recovery. Aileron input results in adverse yaw, that is to say rolling right gives a yaw to the left and vice versa. Rudder authority is negligible.

> Recovery from superstall and oscillating spin is accomplished by moving the stick to a position somewhat forward of the neutral pitch position, with ailerons and rudder neutral. To recover from a flat spin, the yawing rotation must be stopped first, which is accomplished with neutral pitch and full roll input in the direction of the rotation ("stick into the spin"). When the rotation has just about ceased, recovery is accomplished with neutral ailerons and the stick somewhat forward of neutral, just like when recovering from superstall and oscillating spin.

In addition to regular stalled attitudes though, the aircraft also exhibits another stalled attitude with autorotation, the "plunging spiral" (sv. störtspiral) which can also be encountered in two variants. I'm honestly not sure how exactly it works aerodynamically. The flight manual says:

> In certain adverse dynamic scenarios, the aircraft can enter an uncontrolled attitude of the autorotating type, here called plunging spiral . The plunging spiral, which can be either right side up or inverted, is considered to be the potentially most dangerous form of uncontrolled flight that has been discovered during the spin tests of aircraft 37.

> The most common form of the plunging spiral is the inverted one. The following attitudes/maneuvers repeatably result in an inverted plunging spiral: 1) somersault into inverted position from oscillating spin (for example while attempting to recover from a spin with the stick fully forward), 2) stalling the tailfin through so-called "knife edge flying". The inverted plunging spiral is characterized by: 1) negative load factor (-1 to -3 G) 2), low nose, 3) very high rate of rotation in the roll axis (≥ 200°/s), 4) high sink rate (≥ 150 m/s).

> Moving the stick back and/or aileron input to either side tends to increase the rate of the roll rotation. The rotation can be stopped by moving the stick fully forward with no aileron input. When the rotation has ceased, the stick is moved back to neutral pitch, and the aircraft recovers to controlled flight.

> The aircraft only departed into a non-inverted plunging spiral on a few occasions during the spin tests. It has not been possible to define any repeatable attitude or maneuver that results in a non-inverted plunging spiral. During the spin tests the non-inverted plunging spiral only occurred on the following two occasions (not repeatable): 1) when recovering from an inverted superstall, 2) when recovering from an oscillating non-inverted spin. The non-inverted plunging spiral is characterized by: 1) positive load factor (+1 to +3 G), 2) low nose, 3) very high rate of rotation in the roll axis (≥ 200°/s), 4) high sink rate (≥ 150 m/s).

> In a non-inverted plunging spiral, aileron inputs have no effect. Instead, the roll rotation must be stopped by pulling gently back on the stick until the rotation ceases. When the rotation has ceased, the stick is moved forward to the neutral pitch position and the aircraft recovers into controlled flight.