FAA Instrument Rating Airplane (IRA)Flight Instruments and SystemsEasy
Which flight instrument uses both pitot (ram air) pressure and static pressure together to produce its indication?
- AVertical speed indicator
- BAltimeter
- CAirspeed indicator
- DHeading indicator
Show answer & explanationAnswer & explanation
Correct answer: C. Airspeed indicator
The airspeed indicator compares dynamic (pitot) pressure to static pressure through a diaphragm to display indicated airspeed. The altimeter and VSI use static pressure only, and the heading indicator is gyroscopic, unrelated to pitot-static pressure.
Why the other options are wrong
- A. The VSI uses static pressure only, through a calibrated leak.
- B. The altimeter uses static pressure only.
- D. The heading indicator is a vacuum or electric gyroscopic instrument, not pitot-static.
Pitot-Static Instruments
The airspeed indicator, altimeter, and VSI all derive data from the pitot-static system, but only the airspeed indicator requires both pitot and static pressure.
- Airspeed = pitot minus static pressure
- Altimeter = static pressure only
- VSI = static pressure through a calibrated leak and diaphragm
Memory trick: 'A' for Airspeed, 'A' for both — Airspeed needs both Air pressures.