As the JS41 doesn't use VNAV (climbing) via the FMC, I was wondering - how do you calculate when to start your decent?

I've always used the FMS VNAV page calculated TOD point. Then I just try and hold a steady speed in the decent, and keep my actual FPM decent a little below what the FMS is telling me. It's always seemed to work well for me, although you do have to keep a close eye on everything to make sure you don't miss your altitude.

Try this good old standby: http://en.wikipedia.org/wiki/Rule_of_three_%28aviation%29Al

Yes as long as you put your cruise altitude and weight before you set off into the FMC, the VNAV pages will show your distance to your top of descent point and when passed will show your required feet per minute descent to remain on the planned descent path, much like the FMC in a Boeing or Airbus. The only thing it doesn't do is link VNAV to the autopilot, so you just have to initiate the descent manually by setting the autopilot to hold a speed, deselecting altitude hold and reducing the thrust levers. I then use the thrust levers to control my rate of descent according to the FMCs predictions.Regards,Tom Wright

Check out page 86 of the PMDG J41 Pilot Tutorial. The Captain has explained there how he did the math to find TOD. Good to know if your FMS goes AWOL, or you forgot to program it before T/O.Happy flying !

General rule of thumb is the altitude you need to loose ie: I'm at FL200 and need to descend to 4000' for the hold. Use a standard 3deg slope, so I need to loose 16000' (drop the zeros) x 3 = 48nm out.Then to get the correct descent rate just halve your groundspeed and add a zero!!You can also do it the traditional timed way with your watch ie: I need to loose 16000' at 1500FPM ROD = 11min out start your descent.RegardsSteve Forgacs