Which instrument measures the helicopter’s rate of climb or descent?

The Vertical Speed Indicator (VSI) is the instrument responsible for measuring the helicopter’s rate of climb or descent. It provides pilots with crucial information about how quickly the aircraft is gaining or losing altitude, typically expressed in feet per minute.

The VSI operates by comparing the current static pressure inside the instrument with the ambient atmospheric pressure outside. When the helicopter climbs, the static pressure decreases, and when it descends, the static pressure increases. This differential pressure allows the VSI to respond and display the rate of altitude change.

Understanding the rate of climb or descent is vital for pilots during various phases of flight, such as smooth ascents or safe descents, especially in conditions where maintaining a specific altitude is crucial for avoiding obstacles or managing airspace.

The other instruments mentioned serve different purposes and do not measure vertical speed, which distinguishes the VSI as the appropriate choice for this specific function.