The Vertical Speed Indicator (VSI) displays information related to:

The Vertical Speed Indicator (VSI) is a crucial instrument in aviation that specifically measures and displays the rate of climb or descent of an aircraft. It provides pilots with information about how quickly the aircraft is gaining or losing altitude, typically represented in feet per minute. The VSI does this by sensing changes in atmospheric pressure as the aircraft ascends or descends.

While TCAS (Traffic Collision Avoidance System) provides traffic avoidance and safety information, it is not directly linked to the function of the VSI. Instead, the VSI's primary purpose is to alert the pilot about vertical speed ensuring safe ascents and descents, making the connection between vertical speed and TCAS indirect.

Therefore, the most relevant aspect of the VSI is its direct indication of vertical speed changes, which is critical for maintaining optimal flight profiles and ensuring safe operations in the vertical plane. This clear focus on vertical speed aligns it with the option that best describes the VSI’s function while incorporating the context of flight safety.