Forcing blackout of an enemy at your six is the most common way to evade his attack at med and hi speeds. That is, a really hard break, horizontaly or verticaly. If you are fast, you can repeat this evasion technique forever. But, in real life, how many consecutive blackouts is able to resist a normal pilot? Does the blackout affects only the pilot vision, or is also effected his hability to control de plane.
IMO, pilot fatigue should be included as a main realism factor in AH.