# MaxFledglingFact: ARRIVAL DESENT RATE COMPUTATION (Rule of Thumb)

MaxSez: Here’s “When” you Should Start Your Descent for Arrival at your Terminal Destination. A simple “Rule of Thumb”;

So, 3 degrees is a comfortable descent rate in just about any aircraft. But when you’re approaching an airport, how do you know when to start down?

Divide the altitude you need to lose by 300 .

For example, if you’re at 11,000’, and you need to get down to a pattern altitude of 2,000’, you need to descend 9,000’.

9,000/300 = 30 miles.

If you start a 3-degree descent 30 miles out (ATIS Range) you’ll hit pattern altitude as you reach the airport. Keep in mind, you’ll want to add a few miles on to your number, so you hit pattern altitude slightly before you get to the airport.

(Pattern Altitude: Turbine/1500ftAGL… Aspirator 1000ftAGL)
MaxSends

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Good quick calculator Max!
However, this really varies by aircraft and speed. A 172 will have a much different required descent rate then a 767 or A380.

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Another quick question: when you say 30 miles, are you referring to nautical miles, or customary miles?

@HiFlyer. MaxSez: Let’s “Keep it Simple” (KISS) shall we. Since most IF’ers don’t have WizWheels, or access to A/C owners manuals/QRF etc Rules of Thumb are great memory aids. If your a Flight School Grad or hold tickets go for it. (This is a “Fledgling” Topic, Da!)
G’day, Max

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Think nautical miles!

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What’s a “customary mile?”

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Not sure if I worded that properly. I meant to say, are we using a mile as 5,280 feet (standard mile), or 6,076 feet (nautical mile).

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The ”mile”* is an English unit of linear measure equal to 5,280 [feet](https://en.m.wikipedia.org/wiki/Fooby international agreement in 1959.

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