How does a vertical speed indicator (VSI) function?

• A. It shows the aircraft's fuel consumption
• B. It measures the rate of climb or descent in feet per minute
• C. It indicates the aircraft's horizontal speed
• D. It displays the current heading of the aircraft

Answer: (B)

The vertical speed indicator (VSI) specifically measures the rate at which an aircraft is climbing or descending, providing this information in feet per minute. It operates by using a diaphragm that is connected to the aircraft’s altimeter static system. When the aircraft changes altitude, the pressure inside the diaphragm changes accordingly. The VSI then interprets this change in pressure and displays the rate of climb or descent on its dial.

This instrument is essential for pilots to understand how quickly they are gaining or losing altitude, which is critical during takeoff, landing, and while maneuvering. It helps ensure a safe and controlled ascent or descent, allowing for adjustments as necessary to maintain desired flight paths.

The other options presented relate to different instruments or functions not associated with the VSI. Fuel consumption is typically monitored by fuel flow gauges, horizontal speed is measured by a groundspeed indicator, and heading is indicated by a magnetic or directional compass. Each of these functions is linked to separate instruments designed for those specific parameters, emphasizing the unique role of the VSI in providing vertical speed information.