The article quotes the pilot, Tex Johnston, saying something similar, "The airplane does not recognize attitude, providing a maneuver is conducted at one G. It

The article quotes the pilot, Tex Johnston, saying something similar, "The airplane does not recognize attitude, providing a maneuver is conducted at one G. It knows only positive and negative imposed loads and variations in thrust and drag. The barrel roll is a one G maneuver and quite impressive, but the airplane never knows it’s inverted.”