What does the term "VSI" refer to in aviation instruments?

The term "VSI" refers to the Vertical Speed Indicator, which is a crucial instrument in aviation. The VSI is designed to indicate the rate of climb or descent of the aircraft, providing pilots with essential data about the vertical performance of their aircraft. It measures the change in altitude over time, typically displayed in feet per minute (fpm). This information helps pilots to maintain desired altitude changes, ensuring that they manage ascent and descent rates appropriately during flight.

Understanding the VSI is vital for pilots because it assists in achieving optimal flight performance and safety, especially during takeoff and landing phases when controlling altitude changes is critical. Accurate interpretation of the VSI readings allows pilots to make informed adjustments to their flight path, enhancing overall situational awareness and flight safety.