Which sensor could be used to determine that an airplane is in cruise mode rather than takeoff or landing?

• A. 3-axis accelerometer
• B. Radar
• C. 3-axis gyroscope
• D. Tilt sensor

Answer: (C)

A gyroscope that measures angular velocity around the three axes is the right choice. In cruise, an airplane flies with a steady attitude and only small, gradual adjustments, so the angular rates are near zero. During takeoff and landing, the aircraft undergoes rapid pitch and roll changes to climb or descend, which produces noticeable rotations that the gyroscope detects as higher angular velocities.

Other sensors aren’t as well suited for distinguishing cruise from takeoff or landing: a 3-axis accelerometer measures linear acceleration (including gravity) and can be confused by turbulence or thrust changes, not providing a reliable cue of steady flight. A tilt sensor gives orientation relative to gravity but doesn’t track how fast the aircraft is rotating. Radar is used for measuring distance to objects like the ground, not for identifying flight phases.