What does progressive spin refer to?

Progressive spin refers to a condition in which an aircraft experiences an uncommanded motion that results in an increasingly steep rotation around its vertical axis, commonly associated with a loss of control. In this scenario, the aircraft may begin to rotate more quickly and uncontrollably as the spin develops, which can significantly diminish pilot control and increase the risk of an unrecoverable spin situation. Understanding progressive spin is crucial for pilots, as it highlights the importance of recognizing and reacting to the early signs of a spin before it escalates beyond recovery.

The other choices do not adequately capture the characteristics of a progressive spin. For instance, a controlled descent with gradual banking pertains to routine flight maneuvers rather than a loss of control, and normal operations with slight adjustments are indicative of standard piloting practices. Similarly, a gradual increase in speed during a maneuver does not correlate with the phenomena of progressive spin, which is characterized specifically by an uncommanded and increasing rotational motion.