A Vertical Speed Indicator (VSI), also known as a Rate of Climb and Descent Indicator (RCDI) is an instrument which indicates the rate of climb or descent of an aircraft.
The VSI uses the aircraft pitot-static system to determine the vertical speed and depicts the result on a conventional needle and circular scale instrument, or on a ribbon at the side of an Electronic Flight Instrument System EADI.
Two typical VSI indications are depicted below. The first is a conventional indication while on the second instrument, the vertical speed is indicated on the scale at the extreme right of the instrument.
