What instrument measures the rate of change in static pressure to determine ascent or descent?

The instrument that measures the rate of change in static pressure to determine ascent or descent is the Rate of Climb Indicator. This instrument specifically quantifies how quickly an aircraft is climbing or descending by detecting variations in the static air pressure around the aircraft.

When an aircraft ascends or descends, the static pressure changes due to the difference in altitude. The Rate of Climb Indicator uses these pressure changes to provide a readout of the rate in feet per minute or meters per second. This information is crucial for pilots to maintain altitude awareness and control the aircraft during climbs and descents, ensuring safe and efficient flight operations.

In contrast, while the Altimeter measures absolute altitude based on static pressure, it does not provide immediate rate of change information. The Airspeed Indicator measures the speed of the aircraft relative to the surrounding air, and the Turn and Slip Indicator helps gauge the aircraft's orientation and rate of turn, but none of these instruments specifically measure the rate of ascent or descent.