Which instruments use static pressure only?

Which instruments use static pressure only?

• A. Altimeter and Airspeed
• B. Altimeter and VSI
• C. VSI and Airspeed
• D. Airspeed only

Answer: (B)

Static pressure is the ambient air pressure sensed by the aircraft’s static port. The altimeter uses this static pressure alone to indicate altitude — it’s essentially an airtight barometer that expands or contracts its internal chambers as ambient pressure changes, translating that pressure into a readout of height above sea level. The vertical speed indicator also relies on static pressure, but it looks at how fast that ambient pressure changes over time. An internal mechanism and a small calibrated leak create a lag so the instrument deflects in response to the rate of climb or descent, not to the actual pressure value. The airspeed indicator doesn’t fit here because it requires dynamic (ram) pressure from the pitot tube and compares it to static pressure to determine speed; using static pressure alone wouldn’t yield airspeed. So the instruments that use static pressure only are the altimeter and the vertical speed indicator.

Static pressure is the ambient air pressure sensed by the aircraft’s static port. The altimeter uses this static pressure alone to indicate altitude — it’s essentially an airtight barometer that expands or contracts its internal chambers as ambient pressure changes, translating that pressure into a readout of height above sea level. The vertical speed indicator also relies on static pressure, but it looks at how fast that ambient pressure changes over time. An internal mechanism and a small calibrated leak create a lag so the instrument deflects in response to the rate of climb or descent, not to the actual pressure value. The airspeed indicator doesn’t fit here because it requires dynamic (ram) pressure from the pitot tube and compares it to static pressure to determine speed; using static pressure alone wouldn’t yield airspeed. So the instruments that use static pressure only are the altimeter and the vertical speed indicator.