Which of the following is a vertical mode?

• A. Altitude Select
• B. Roll
• C. Nav
• D. Heading

Answer: (A)

Vertical modes steer the aircraft along the vertical axis, controlling pitch and thrust to reach and hold a target altitude or follow a vertical profile. Altitude Select is a vertical mode because it sets a specific altitude for the autopilot to capture and maintain, guiding climbs or descents to that altitude. The other options operate on the horizontal plane: Roll manages bank angle, Nav provides lateral navigation guidance, and Heading maintains a compass direction. So Altitude Select is the vertical mode.