E6B Descent Gradient: How do I find distance and rate?

Question

Using a descent gradient of 3:1 (333 feet per nautical mile), use a mechanical (non-electronic) E6B to calculate the distance in NM required for a descent and the rate of descent in feet per minute for a given ground speed, without turning the wheel. How would I set this up in my E6B? Setting the rate arrow to 333 gives me accurate information for the rate of descent, but I cannot find where I could see the distance required to descend a specific amount.

Answer 1

You would use the time scale as a substitute for required distance.



You have already set it up correctly by aligning the arrow with 333 on the outer scale. The arrow equals 60kts on the inner scale. That is one mile per minute at 333fpm. The arrow also equals one hour on the time scale. You can now substitute hours for miles. One hour equals one mile, aligned with 333 on the outer scale, so 2 hours equals the 2 miles you would need to descend 666ft. Six hours equals the 6 miles you would need to descend 2000ft at 333fpm.



Aligning the arrow with 333 gives you the ratio you wanted. The inner scale now shows speed. The outer scale shows required rate for a given speed. The time scales shows required distance for a given descent, albeit diplayed as hours.



I hope the explanation was clear, I know it was redundant.

Answer 2

For VFR flight suppose your flying at FL 20000 the best way to start a descent is to get rid of the last three digits in this case its 000 and you land up two digits thats 20. Now you multipy 20 x 3 which gives you 60NM to start your step descent with a descent rate of -1000 - 1500FPM. Safe flying

Answer 3

really? use the same setup like for fuel consumption.



set number (fuel consumption, descent rate per min) against 60 in the box. find time of descent against the total altitude descended. elaborate to find the descent distance.