Which instruments are classified as part of the air data system?

• A. Airspeed indicator, altimeter, vertical speed indicator, and Mach meter in advanced aircraft.
• B. Attitude indicator, heading indicator, turn coordinator.
• C. Fuel gauges, oil pressure gauge, tachometer.
• D. Airspeed indicator only.

Answer: (A)

Air data systems gather flight information by using the pitot-static system to measure air pressures, and, in many aircraft, temperature as well. From those pressures, the instruments in this group display several key air data parameters: the airspeed indicator uses the difference between ram (pitot) pressure and static pressure to show speed; the altimeter relies on static pressure to indicate altitude; the vertical speed indicator tracks how rapidly static pressure is changing to show climb or descent rate; and in advanced aircraft, the Mach meter uses the pressures (and temperature) to display Mach number. These instruments are all about interpreting how the aircraft is moving through the air.

The other instruments mentioned belong to different systems: attitude indicators, heading indicators, and turn coordinators are gyro-based instruments that provide orientation and turning information, not air data derived from the pitot-static system. Fuel gauges, oil pressure gauges, and tachometers monitor engine and system parameters, not air data. And having only the airspeed indicator would omit the other essential air data measurements that the system provides.