According to the ROD rule of thumb, what is the formula used for calculating descent rates?

The formula used for calculating descent rates according to the Rate of Descent (ROD) rule of thumb is derived from the relationship between ground speed (GS) and the appropriate descent rate for a given altitude. When the ground speed is multiplied by 5, this gives a straightforward and effective descent rate in feet per minute.

This method simplifies the calculation for pilots, allowing for a quick estimation during descent planning. The idea is that for every 10 nautical miles of distance, the altitude lost should be approximately 5000 feet if following the ROD = GS x 5 rule. Therefore, multiplying the ground speed (in knots) by 5 effectively translates the speed into an altitude loss per minute, making it a practical guideline for managing descents while considering operational safety and efficiency.

Other methods, such as subtracting from ground speed or dividing it, would not yield the necessary altitude change in a scalable and manageable format that pilots need during flight operations. Hence, ROD = GS x 5 is the recognized and widely adopted formula in aviation operations.