What does a vertical speed indicator measure?

The vertical speed indicator (VSI) measures the rate of climb or descent of the aircraft, providing pilots with essential information about how quickly they are gaining or losing altitude. It displays this rate in feet per minute, which helps pilots make informed adjustments to their control inputs during ascent or descent phases of flight.

By understanding the rate of climb or descent, a pilot can determine if they are maintaining a desired altitude, safely approaching a landing, or avoiding potential obstacles. This instrument is crucial for effective altitude management and overall flight safety.

While choices such as the amount of fuel remaining, the heading of the aircraft, or the airspeed of the aircraft are important aspects of flying, they are measured by different instruments entirely: fuel gauges, heading indicators (or magnetic compasses), and airspeed indicators respectively. Thus, the specific function of the vertical speed indicator is solely focused on providing information about altitude change rates.