Glideslope Computations

What altitude range does the mach trick work at? Seems like that this one could be incredibly inaccurate depending on your altitude....
 
This is basically the same thing as what everybody else was saying, but I generally take my airspeed, add a zero to the end of it and divide it in half.

In other words:

Groundspeed = 120kts
add a zero = 1200
divide by 2 = 600fpm

Again, it's the same method but for some reason easier for me to do it this way in my head.
 
One I didn't see mentioned is the basic formula for climb and descent gradients:

(altitude to gain or lose ÷ distance) X (ground speed ÷ 60) = VSI required

That and some 9th grade algebra gets you the answer to stuff like
  • What climb rate do I need to meet that 300 feet/NM climb requirement for the ODP?
  • What vertical speed you will need to comply when ATC says "Cross XXOOX intersection at 3000"
  • How far out do I need to start down if I want to descend to the airport at 500 FPM?
 
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