When to start your descent

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For those that don’t know a simple mathematical formula for REAL WORLD FLYING, not VNAV and auto approach.When to start your descent. Let’s say you are at cruise altitude of FL300 30,000 ft., you keep the first three digits of 30,000, 300. You then divide that by 3 since you will descend at a 3 degree angle just as when you land, giving you 100. That means you start your descent when you are 100nm from the airport you are landing at. Or 21,000 ft. 3÷210=70. Start descent 70nm from airport to get you down to at least 10,000ft. in ample time.

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I always use Arrivals & Approaches, and so I just let VNAV do the work lol

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Yeah, perfectly if ATC (APP) is on

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What about using the wonderful features that were introduced in IF long ago. Like the SID’s and STAR’s and then just use the wonderful VNAV button then you don’t need to calculate your TOD.

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I agree, but I guess it works for airports with no procedures.

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Well of course but in the real world flying you don’t have these features, I should have made it clear use this formula minus the auto land, I knew someone one criticize there always is.

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I’m guessing this is mainly for VFR or airports that don’t have any procedures right ?

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Thats not right the VNAV and SID STAR system are real world systems that are used daily by Comercial Pilots

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Yeah thats correct

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I heard a similar rule of thumb of 3 miles per 1000 ft of descent. Remove the thousand and multiply by 3. For example, a 30,000 ft descent would start 90 miles out.