Johan Nordqvist wrote on Apr 27^th, 2012 at 6:14am:

Hello! I have a question regarding TOD calculation. How would I know when to start my descent if the STAR consists of radials from VOR beacons that aren't located at the arrival airport? The approach I have in mind is the STAR RWY 32 at ESTA: http://www.lfv.se/AIP/AD/AD%202/ESTA/ES_AD_2_ESTA_4_5_en.pdf Now, let's assume the local DME at the airport, how would one know the distance at which the descent would be initiated? Also, how would one plan the TOD for a NDB approach to an airport without DME? Johan

Ok. Thats not hard. Say you at FL320. At the bottom of Page 2 positions of MISMA and NILEN given in relation to SVD VOR\DME. You need arrive to MISMA not below 5000 ft. so you need to descend from FL320 to 5000 => you need to spent 27000 ft. If you dont follow ATC in that case, then use standard 3x profile. TOD 27*3 = 81 nm from MISMA.  But MISMA located at 35.3 nm from SVD VOR\DME, so add 35.3 nm => you have TOD 116.3 nm from SVD VOR\DME. If you'll stay on profile - you'll arrive to MISMA at 5000 ft. Thats not hard alt, so you can be higher then that at MISMA.
Procedure itself pretty clear and easy flyable. If you need details of it, - ask. In this case DB DME at airport given to help to approach runway at proper descend path. You should'nt use it to plan descend. Use SVD VOR\DME instead. DB DME comes into work just after turn to HDG 312. it'll tell you where FAF is, and provide you with data for final app. descend.

Now about NDB, no DME aproach. You have several options here.

1 - check if airport located within coverage of other DME. And use that DME as reference. For example YMMI has no beacons at all, but it located at intersection of 2 nearby VOR\DMEs. So you can plan approach via that nearby beacons.

2 - In 707 you can use doppler NAV to track last leg of route.  Activate DNS at last VOR you fly over, and it'll tell you distance to airport.

3 - You can use dead reckoning. You'll need to know your GS or at least TAS. 707 DNS gives you that data, but in 727 you gotta use formulae to convert IAS to TAS. as you did that, you can calculate time to TOD from last beacon you flew over.

NDB radius about 60 nm in FSX, so you need to use one of upper methods to avoid circling over airport.