What indicates a properly functioning pitot-static system during preflight checks?

• A. Visual inspection shows clean and unobstructed pitot tube and static ports; all three primary instruments show reasonable readings and no discrepancies.
• B. All three instruments must be in the green.
• C. The engine instrument readings are normal.
• D. The autopilot engages automatically.

Answer: (A)

A properly functioning pitot-static system is shown when the pitot tube and static ports are clean and unobstructed and the three pitot-static instruments display reasonable readings with no discrepancies. The airspeed indicator uses ram pressure from the pitot tube and ambient static pressure; the altimeter and vertical speed indicator rely on static pressure. If the ports or tube are blocked, these instruments can read incorrectly or not respond properly, leading to dangerous indications. Seeing clear ports and consistent, sensible readings across the airspeed, altitude, and vertical speed instruments confirms the system is transmitting accurate pressure signals. The other options don’t test the pitot-static system: “green” readings aren’t a universal, reliable preflight criterion; engine instruments are separate from pitot-static pressures; and autopilot operation isn’t governed by this system.