How far out should a pilot start their descent for a 3° glide?

To determine how far out a pilot should begin their descent for a 3° glide, it's essential to understand the relationship between altitude and distance in a descent. A standard glide path, like the 3° descent angle, allows pilots to calculate how far in advance they should start descending based on the altitude they need to lose.

Typically, a rule of thumb for a 3° glide slope is that the altitude to lose (in feet) is divided by 300 to find the distance (in nautical miles) from the destination at which to start the descent. For example, if a pilot needs to lose 3,000 feet, they would start their descent approximately 10 nautical miles away (3,000 feet ÷ 300 = 10 nautical miles).

This calculation is based on the glide path's angle and typical descent rates, providing a practical method for determining descent planning. Hence, when the correct approach is to divide the altitude to lose by 300, this aligns perfectly with the principles of a standard descent for a 3° glide.