During gazelle conversion we were introduced to the effect.
60* nose down, 60* left wing down and pull the cyclic back sharply, whack! instant level attitude and climb.
Next, 30* and 30* to the right, do the same again, with a degree of fear mixed in, whack, onto your right side.
I only had an incipient case once and managed to get out of trouble with a gentle chatter from the jacks as we bottomed out of a dive. (Had to do it my mate was sailing out of Belfast in a sweeper)
An Army pilot lost a gazelle in NI as he turned hard right at low level and hauled it around, airspeed being a contributory factor he entered jack stall and it ploughed in. I believe a Colonel of an infantry regt was killed.