The reason for the Tucano having 'stick central' in the spin recovery is due to the fact that it has an inverted spin mode as well as the erect spin mode, and 'stick central' works for both. Therefore, the spin recovery is identical for an erect and an inverted spin and a pilot does not have to identify whether the spin is erect or inverted in order to effect a recovery.
The initial spin recovery procedure recommended by Shorts for the Tucano was 'Throttle closed, all controls central'. However, their spin testing was limited and it was discovered during the Release to Service trials that following a left erect spin that had been initiated with 30% torque or more when the power had been maintained for more than 2 turns, the spin would not stop with a centralised recovery. Therefore, the current recovery technique was devised that would work for all spins. The worst case that we flew was left, erect, full power for 4 turns, full right rudder, stick central, 4 more turns then select idle. It recovered satisfactorily which definitely proved recovery from the worst case scenario. Now that one was fun!!!!