Airbubba: The approach plate I am looking at is dated 25 July 2012, from SE-4, AL-50(FAA). Glide slope noted as 3.28 degrees. The math went like this. (It may or may not reflect said glide slope. I don't have my old GS table at hand ...)
Hmm, you have a point, my calc was to MAP, not touchdown.
I'll try a different method.
If I start at the IAF at 3500 feet (as shown) and arrive at threshold (644 feet), I lose 2856 feet over a distance of 12.8 nautical miles.
150 kts GS gives me 2.5 nm per minute (5.12 minutes) 558 FPM.
180 kts GS gives me 3 nm per minute (4.27 minutes) =670 FPM. (Not far from ~700 fpm)
Granted, one should cross the threshold higher than 0 feet AGL. Call the total delta in alt -2800 feet and decrease ROD slightly to hit the box.
Last edited by Lonewolf_50; 16th Aug 2013 at 14:03.