What is the recommended rate of descent if you need to lose altitude rapidly at a groundspeed of 400 knots?

To determine the recommended rate of descent when needing to lose altitude rapidly at a groundspeed of 400 knots, it’s essential to understand the relationship between the groundspeed and the rate of descent.

When flying at a high groundspeed such as 400 knots, a quicker descent is essential to ensure altitude is lost efficiently—especially in situations like rapid descent for emergency or traffic avoidance. Generally, a common rule of thumb for a rapid descent rate is that the descent rate in feet per minute (fpm) should be equal to or greater than twice the current groundspeed in knots. This means that at a groundspeed of 400 knots, a descent rate of about 2000 fpm would be necessary to achieve a rapid descent. This descent rate allows pilots to lose altitude effectively, maintaining control of the aircraft while adhering to safety protocols.

Therefore, choosing a rate of 2000 fpm or higher would be appropriate for safely and effectively descending from a high altitude while flying at this speed. The selection aligns with standard operating procedures for rapid descents in aviation.