On approach, the auto throttle should be set to SPD; this ensures which of the following?

• A. Speed control at advised value
• B. Altitude hold
• C. Vertical speed hold
• D. Heading hold

Answer: (A)

SPD on the auto throttle keeps the aircraft at the commanded airspeed. On approach you want to hold the advised approach speed so you have enough lift and control authority to respond to gusts and to maintain a stable path to the runway. The auto throttle will automatically increase or decrease thrust to keep that target speed as you descend and maneuver. This is different from altitude hold (which fixes altitude), vertical speed hold (which controls rate of descent or climb), or heading hold (which maintains a direction). So the result of using SPD is maintaining speed at the advised value.