Quoted from my personal notes I keep…
When to Descend.
Using trigonometry to calculate …
1mile = 5280ft therefore…
3deg glide = 277ft per mile.
4deg glide = 369ft per mile.
5deg glide = 462ft per mile.
Remember though that airfields quite often aren’t at zero ft, so use AGL or subtract the airport altitude from your actual altitude.
Most approaches will be a 3° glide slope. A quick and convenient way to calculate these in your head is…
If you multiply your distance from the airport by 300 and add it to field elevation.
SXM airport elevation is 26 ft
3 miles from SXM you should be 900 feet
2 miles from SXM you should be 600 feet
1 mile …"…" 300 feet
1/2mile …"…" 150 feet
Another tip on long decent and knowing when to start decending is…
Multiply altitude by 3 so 22000 x 3 = 68000 remove the 0s, your then left with 68, so you would descend 68nm from your desired airport. For the VS divide your ground speed by 2 which can be found in the bottom left corner of your HUD display. so of your ground speed was say 300 KTS you would descend at -1500 FPM
Ps your icon appears normally to me, and I’m guessing to others. Might be a glitch with your browser.