If you want to descend from FL370 down to FL220, how far out do you start your descent?

To determine the correct distance to start a descent from flight level 370 (FL370) to flight level 220 (FL220), it is essential to consider the standard rate of descent and the altitude change involved. In this scenario, the altitude difference is 15,000 feet since you're descending from FL370 (37,000 feet) to FL220 (22,000 feet).

A commonly used rule of thumb for calculating the descent distance involves the principle of descending at a rate of approximately 3,000 feet per minute, allowing for a standard descent profile. Generally, a good estimate for the distance required for every 1,000 feet of descent is about 3 nautical miles. Therefore, to calculate the total descent distance:

1. Calculate the total altitude change: 37,000 feet - 22,000 feet = 15,000 feet.

2. For every 1,000 feet of descent, you would require roughly 3 nautical miles.

3. Thus, for 15,000 feet: 15 × 3 = 45 nautical miles.

This estimate aligns most closely with needing to start the descent at least 45 miles from the waypoint. However, opting for an earlier start is often advisable for safety and planning