Yes, I find it simplest to use 3 times altitude divided by 1000 to figure my descent point. I know the description sounds complex but it really isn't. Take today for example. I was at FL210 and wanted to be at 2500 feet at 10 DME.
For simplicity, I said that 2500 feet was really 2000 feet, requiring a net height loss of 19,000 feet by the time I reach the 10 DME point. Dividing 19000 by 1000 gives me 19. I multiply 19 by 3, to give me 57, then add the 10 DME, to give a resultant descent point of 67 DME, which I rounded (today) to 65 DME. I then planned to descend at an initial IAS of 220 knots. I divide 220 by 10, to get 22, then halve that, to give me 11, then multiply that by 100, to give me a rate of descent of 1100 feet per minute to maintain profile.
It almost always works out well, unless you've got very strong headwind or tailwind. It didn't today but that was because I had to make a step descent with a Dash-8. It was a tad behind me and above. I knew it would overtake me if I gave it the opportunity and that would be simpler for both of us. As I was thinking that, ATC asked if I could descend early.
I advised that I could descend straight away - I was still around 74 DME at the time. Rather than do any maths at that stage, I just slowed to 200 knots, to ensure that the Dash would overtake quicker and descended at (200/10 = 20. 20/2 = 10. 10 x 100 = 1000 FPM) until reaching a point where there was enough separation between us, with the Dash ahead of me for us both to descend on our normal profiles.
I was about to work that out when I noticed a "live" Glideslope needle. I was, by then, 50 DME. Before using it, I decided to test the signal by intercepting it (it was above me at the time so it wasn't as if I had to fly down, which I wouldn't have done while still so far out). Then adopted my original 220 knots/1100 FPM profile. The GP signal did the right thing so I didn't have to do any further maths and passed the IAP exactly on profile.
So there ya go. When ya don't get any profile disruption, do it the way my plan started out and you'll get the hang of it in no time and be able to short-cut the calculations before you know that you're doing it. If you get a live GS indication further out than you expect, just check its behaviour against the profile you've planned to fly, as already worked out.
Some days, things just go too smoothly!
