An abrupt change from climb to straight-and-level flight can create which illusion?

The correct answer is that an abrupt change from climb to straight-and-level flight can create the illusion of tumbling backwards. This phenomenon is related to how the body perceives changes in motion. During a climb, the body is experiencing a sensory input that indicates an upward movement. When the aircraft then suddenly levels off, the change in acceleration can confuse the vestibular system, which is responsible for balance and spatial orientation.

As the pilot transitions from climb to level flight, the sudden reduction in vertical acceleration may lead them to feel as though they are still climbing or potentially falling backward. This perceived backward motion is often due to the brain's reaction to the rapid change in forces acting on the body, especially if the pilot is not aware or prepared for the transition. Such an illusion can impact pilot performance and situational awareness, making it crucial for pilots to maintain control and to rely on instruments during such transitions to avoid potential disorientation or misinterpretation of flight conditions.