What does the Vertical Speed Indicator (VSI) measure?

The Vertical Speed Indicator (VSI) measures the rate of climb or descent of the aircraft. This instrument provides crucial information to the pilot by indicating how quickly the aircraft is gaining or losing altitude, usually expressed in feet per minute. This information is vital for maintaining safe flying practices during takeoff, landing, and in-flight maneuvers, helping pilots make informed decisions about altitude adjustments.

Understanding the rate of climb or descent is essential for various aspects of flight, including managing approach paths for landings and ensuring safe altitude changes while en route to a destination. The VSI relies on static pressure changes in the atmosphere to provide these readings, making it a key instrument in an aircraft's cockpit alongside others like the altimeter and airspeed indicator.