What is the 3 to 1 rule for descent planning?

A general rule of thumb for initial IFR descent planning in jets is the 3 to 1 formula. This means that it takes 3 NM to descend 1,000 feet. If an airplane is at FL 310 and the approach gate or initial approach fix is at 6,000 feet, the initial descent requirement equals 25,000 feet (31,000–6,000).



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For a 3 degree glideslope, required rate of descent in feet per minute is approximately equal to ground speed in knots multiplied by 5.

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The 1 in 60 rule states that if you're off course by 1NM after 60 miles flown, you have a 1-degree tracking error. Time to correct that heading! Another tip: If you're 60 miles away from a VOR, and you're off course by one degree, you're off course by one mile.

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Many pilots refer to this as the 1-2-3 rule: Plus or minus 1 hour from arrival, ceilings at least 2,000 feet and visibility at least 3 statute miles.

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Rate of descent calculation method 1 The resulting number is our approximate descent rate in feet per minute. For example, if our groundspeed is 100 knots indicated airspeed (KIAS), and we multiply it by 5, that would equate to a 500 FPM descent rate to achieve a 3-degree descent angle.

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This rule of thumb is incredibly powerful in the aviation environment. It states that for each degree off (or displacement) over a distance of 60 nautical miles (NM), it will result in 1 NM off course. It can be applied in various areas of interest when flying, and is easily remembered.

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In general, a comfortable rate of descent for a fit person is 500 feet per minute.

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