Which instruments depend on static pressure only?

Which instruments depend on static pressure only?

• A. Airspeed Indicator
• B. Vertical speed indicator (IVSI) and altimeter
• C. Attitude Indicator
• D. Turn Coordinator

Answer: (B)

Static pressure provides the baseline pressure that changes with altitude, and some instruments are designed to respond only to that ambient pressure. The altimeter is built to translate static pressure directly into an altitude reading—the pressure you feel in the air around you decreases as you climb, and the altimeter’s sealed mechanism converts that pressure into hands on the dial. The vertical speed indicator uses the same static pressure source but with a calibrated internal leak so it responds to the rate at which that pressure is changing over time; that rate of change tells you whether you’re climbing or descending and how fast. Other instruments pull on additional pressures or different mechanisms. The airspeed indicator compares pitot (dynamic) pressure to static pressure to determine airspeed, so it’s not static-pressure only. The attitude indicator is a gyroscopic instrument, not based on ambient air pressure. The turn coordinator relies on a gyroscope (or an electromechanical equivalent), not on static pressure for its primary indication. Therefore, the instruments that rely on static pressure alone are the altimeter and the vertical speed indicator.

Static pressure provides the baseline pressure that changes with altitude, and some instruments are designed to respond only to that ambient pressure. The altimeter is built to translate static pressure directly into an altitude reading—the pressure you feel in the air around you decreases as you climb, and the altimeter’s sealed mechanism converts that pressure into hands on the dial. The vertical speed indicator uses the same static pressure source but with a calibrated internal leak so it responds to the rate at which that pressure is changing over time; that rate of change tells you whether you’re climbing or descending and how fast.

Other instruments pull on additional pressures or different mechanisms. The airspeed indicator compares pitot (dynamic) pressure to static pressure to determine airspeed, so it’s not static-pressure only. The attitude indicator is a gyroscopic instrument, not based on ambient air pressure. The turn coordinator relies on a gyroscope (or an electromechanical equivalent), not on static pressure for its primary indication. Therefore, the instruments that rely on static pressure alone are the altimeter and the vertical speed indicator.