Descent Calculations-

[Guest]

Brian,The 30 miles is a planning point only for smaller airports ( a target rule of thumb so to speak). Thank you, I should have clairified that. At larger airports ATC will controll you all the time. If you are descending into CHS for example and ATC says, "Pilot's descretion descend and maintain 10,000" I can figure that I want to achieve this by at least 30nm from CHS. This is good planning since below 10,000 life can get real busy.Now when ATC assigns you a restriction to meet at a waypoint you have to plan for that requirement. For example, when ATC says, "Cross X Intersection at 10,000 and 250KTS" the slow down 10kts per 1 mile comes in handy. Typically when you level off at 10,000ft your IAS will be approx 320kts. So for planning you can figure 7 miles to slow down. So you should plan to be level at least 7 miles prior to X Intersection and use the remaining 7 miles to slow.I hope that helps more. Grady Boyce

[CharlieZ 0]

This is what I use. Distance To Decend 1. Take your altitude in thousands and multiply it by 3. That equals your distance in miles to begin your descent.2. Now take half your ground speed. This is your rate of descent in hundreds of feet.Example: If you are flying at 12000ft at a ground speed of 150kts and you need to descend to 2000ft, the difference is 10000ft.Multiply 10x3=30 miles out you must begin your descent. Half your ground speed is 75, add a zero, and 750 ft per minute is your rate of descent.You can do this all in your head while flying.

[LAdamson 240]

I still like to plan for 500 fpm with passengers in an un-pressurized GA aircraft, and base calculations on that figure. 750 fpm is workable, but some people are sensitive to it.........ears as an example.1000 fpm as suggested elsewhere in this thread, can get downright un-comfortable for some.L.Adamson

[Guest]

I appreciate the info, Grady. It's always good to hear how the real people do it, and thanks for taking the time to clarify.Best regards,--Brian ToobyTCA Pilot #2658Pilot's Assistant Home Page:http://www.tooby.demon.co.uk/P_Assist_Home.html