What term is used to indicate the speed of a closing process or distance?

The term "RATE OF CLOSURE" is commonly used in aviation to refer to the speed at which two objects (such as an aircraft and a target) are converging. It quantifies the distance between the two objects and the time it would take for them to close that distance at their current speeds. This concept is especially important in various contexts, such as during landing approaches and in air traffic control, as it helps pilots and controllers make informed decisions about spacing and timing.

The other terms, while related, may not be as widely recognized in standard aviation terminology. "CLOSING RATE" and "SPEED OF CLOSURE" might convey a similar idea but aren't the terms most commonly used or accepted in the industry. "APPROACH RATE" is contextually related to how an aircraft approaches a target or runway but does not specifically define the combined concept of speed and closing distance as accurately as "RATE OF CLOSURE." Thus, using "RATE OF CLOSURE" is the most precise way to communicate this critical aspect of flight operations.