An optical illusion that can result in spatial disorientation for the pilot. This is caused by an abrupt change from climb to a straight and level flight, which can excessively stimulate the sensory organs for gravity and linear acceleration, and which gives the illusion of tumbling backward. The disoriented pilot pushes the aircraft abruptly into a nose-low attitude, possibly intensifying this illusion.
When stimulated by the rapid change in attitude, you feel as if you are tumbling backwards, into what's called an inversion illusion. Such a disoriented pilot may push the aircraft sharply nose-down, which can intensify the illusion.