What is the primary function of the VSI in an aircraft?

The primary function of the Vertical Speed Indicator (VSI) in an aircraft is to calculate and display the rate of climb or descent, measuring how quickly the aircraft is gaining or losing altitude. This information is crucial for pilots as it helps them maintain a desired flight path and ensures a safe and efficient ascent or descent. Understanding the vertical speed allows pilots to manage their altitude changes appropriately, particularly during approaches, takeoffs, and landings.

Monitoring ascent and descent rates with the VSI aids in complying with air traffic control instructions and adjusting flight profiles, ensuring that the aircraft is performing as expected in relation to its altitude changes. While other instruments in the aircraft serve different functions, such as providing airspeed or heading information, the VSI's specific role in monitoring vertical movement is essential for flight safety and performance.