Which systems rely on knowing whether the aircraft is on the ground or in the air?

• A. Stick Pusher computer only
• B. ECS only
• C. Propeller de-ice only
• D. All of the above

Answer: (D)

Knowing whether the aircraft is on the ground or in the air determines how several systems operate so they behave correctly during takeoff, flight, and landing. The stick pusher is a stall-protection feature that should be active only in flight; when on the ground, the system uses ground status to disable it and avoid nuisance actions during taxi or rotation. The environmental control system uses the ground-versus-air condition to decide how to manage cabin temperature, ventilation, and pressurization—on the ground the cabin isn’t pressurized the same way as in flight, so the controls follow a different mode than at altitude. The propeller de-ice system also relies on this status to decide when heating is needed; icing protection is crucial in flight, but during ground operations the logic may prevent unnecessary energizing and save power.

Because each of these subsystems uses ground/flight status to choose the appropriate operating mode, all of the above systems depend on knowing whether you’re on the ground or in the air.