When recovering from a spin, the first step is generally to cut the throttle:
... Otherwise, to recover from an upright spin, the following generic procedure may be used: Power is first reduced to idle and the ailerons are neutralized. Then, full opposite rudder (that is, against the yaw) is added and held to counteract the spin rotation, and the elevator control is moved briskly forward to reduce the angle of attack below the critical angle. Depending on the airplane and type of spin, the elevator action could be a minimal input before rotation ceases, or in other cases the pilot may have to move the elevator control to its full forward position to effect recovery from the upright spin. Once the rotation has stopped, the rudder must be neutralized and the airplane returned to level flight. This procedure is sometimes called PARE, for Power idle, Ailerons neutral, Rudder opposite the spin and held, and Elevator through neutral. ... [Wikipedia]
This is extremely counterintuitive; given that another vital step in spin recovery is to apply full down elevator1 to get the nose down, one would expect that the blowback from the engine (especially for tractor-propeller aircraft) would aid in recovery by striking the underside2 of the deflected elevator, and, thereby, pushing the tail up (and the nose down), making it seem, at first glance, that it would be best to firewall the throttle in order to get the tail up and the nose down as quickly as possible.
In addition, even without the contribution from the elevator, applying full throttle would:
- drag the aircraft forwards through the air, increasing the forward component of its motion and decreasing the angle of attack seen by all the various parts of the aircraft;
- for tractor-propeller aircraft, blow air at high speed backwards over the wings, dramatically lowering the local angle of attack felt by the wings.
Both of these effects would tend to destall the aircraft and transform the spin into a boring old trivial-to-recover-from spiral dive.
So why do spin-recovery procedures for most aircraft generally call for cutting the throttle, rather than firewalling it?
1: Or, if spinning while inverted, full up elevator.
2: Replace "underside" with "upper side" if spinning inverted.