Some pilots aren't totally sure of the differences between a spin and a spiral dive. That's OK in the classroom setting when discussing aerodynamic theory, but it can be dangerous in the cockpit should either flight condition be allowed to develop and the pilot doesn't immediately know what's going on or the corrective actions to take.
A spin is an aggravated stall that develops into a rotation with high angle of attack and at least one wing below stall speed. In a descending spiral, the wings aren't stalled; instead the airplane accelerates around a spiraling path, with the spiral usually tightening on its own as airspeed, bank angle and load factor increase.
The recovery techniques from a spin and a spiral aren't the same since in the spin the object is to break the stall by reducing angle of attack and increasing airspeed and in the spiral dive the goal is to reduce speed.
How should you recover from a spiral dive? First, immediately reduce power to flight idle. Then bring the airplane to wings level with coordinated use of aileron and rudder. Finally, use elevator inputs to bring the airplane to straight and level flight, keeping in mind that at the high airspeed you risk structural failure, and you may eventually need to start applying forward elevator to keep the nose from rising too much.
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