If a standard or fixed speed descent strategy yields VS less than 500 fpm, what should be done?

If a standard or fixed speed descent strategy yields VS less than 500 fpm, what should be done?

• A. Maintain current VS
• B. Set VS to -500 fpm and re-enable A/THR
• C. Increase VS to -1000 fpm
• D. Disengage A/THR

Answer: (B)

When using a standard or fixed-speed descent, you’re aiming for a specific descent profile: a vertical speed around 500 fpm while the autothrust keeps the airspeed on target. If the actual vertical speed is shallower than that (not descending fast enough to meet the 500 fpm target), the immediate fix is to set the vertical speed to -500 fpm and re-engage the autothrust. Setting -500 fpm re-establishes the designed descent rate, and re-enabling A/THR ensures the engine thrust is actively controlled to hold the target airspeed as you descend. Keeping the current, slower VS would keep you off the prescribed descent path, and jumping to a much higher rate (like -1000 fpm) could push you away from the profile and altitude constraints. Disengaging A/THR would remove automatic speed control, increasing the risk of speed drift during the descent.

When using a standard or fixed-speed descent, you’re aiming for a specific descent profile: a vertical speed around 500 fpm while the autothrust keeps the airspeed on target. If the actual vertical speed is shallower than that (not descending fast enough to meet the 500 fpm target), the immediate fix is to set the vertical speed to -500 fpm and re-engage the autothrust. Setting -500 fpm re-establishes the designed descent rate, and re-enabling A/THR ensures the engine thrust is actively controlled to hold the target airspeed as you descend. Keeping the current, slower VS would keep you off the prescribed descent path, and jumping to a much higher rate (like -1000 fpm) could push you away from the profile and altitude constraints. Disengaging A/THR would remove automatic speed control, increasing the risk of speed drift during the descent.