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

Windplayer nice answer for the 3* profile approach and STAR.

Bit more on the NDB. You can use GPS in lieu of DME, set the GPS NRST to the NDBs AIP code e.g CKN for Cooktown QLD Australia, its on the NDB Approach Chart anyway. If you don't want to do that I would use the nearest DME that could give me a distance to use to about 30 nm from the NDB, if not time it - the key thing with the NDB is that you only have a positive fix and position by passage over the aid. Then you must use timing only and the approaches are designed to allow for tolerances for timing to a point and you are able to apply corrections for known wind to shorten tracking or increase tracking as required.

I recommend a 3x profile descent adding in the legs outbound, turning inbound, inboud to MAP, this will give you the approximate distance to fly, lets say a 2mins out at 180 knots = 6nm, then 1 min turn inbound, generally about 180 degrees of arc so on a rate 1 turn @3 nm, then 2 mins inbound at 150 kts = 5nm so you need to subtract this from your nominal TOD point based on 3x your altitude.

Once you get the hang of it you can fly a whole reversal turn NDB on profile and be nicely above the minimums and it is all incorporated into your managed descent from your inbound cruising altitude.

Just a final note for those without much IFR experience and NDB is a non precision approach, it is designed to get you to a safe circling altitude within 5 nm of the aerodrome where the NDB is located. Most are not runway aligned so your offcentre or even 90 degrees on some, so your MDA is always about the visual circuit height anyway.

The NDB has been around a long long time, I have a copy of a 1938 NDB approach for Chicago in the US I found it in a an old textbook on radio navigation in a bookshop. Nothin much has changed procedurally since then even the chart looked identical. In real life they are a bugger to fly because of all sorts of issues with signal strength location weather time of day etc which is not reproduced in FSX thank goodness otherwise you guys would all go nuts trying to work out what is going on, I've see real NDB needles dance around all over the shop, swing from side to side and sometime just go and point at the nearest thunderstorm instead. Most I ever did was 8 NDB approaches for real in one day in my flying career, not a record but by number 8 I was fed up with them I can tell you, especially in rain at night. In Australia the ILS is a rarity the NDB is the norm and most common approach for most airports.

Thank you for your help!

I seem to have missed that the altitude restriction of 5000ft starts at MISMA.

As for the NDB calculations, I'm assuming that the GPS is unavailable.
In other words, it requires either:

1. Circling over the NDB while descending from FL320 down to MDA.
2. Planning the approach in advance so that the TOD can be calculated from waypoints or such.

On the upper pic you arriving from the NWW. Say you flying magnetic HDG 110 on that pic. You know that at MISMA you gotta be at 5000, so you kno that TOD located 81 nm from MISMA. Thats correct for all directions from MISMA. From map you know position of MISMA. So you know 2 sides of triangle. Angle alfa is Your HDG - 35(radial of SVD VOR) = 75.

Then use cosine theorem X^2= 81^2 + 35.3^2 - 2*81*35.3 * cos(alfa)
Thats how you'll know distance to TOD from SVD VOR. Now you can find the angle between X, and 35.3 nm side using ptolemey's theorem, or using sin, or cosine theorem.

Thats links for required theorems in usable forms:

http://en.wikipedia.org/wiki/Law_of_cosines
http://www.cut-the-knot.org/proofs/sine_cosine.shtml

It is better to obtain not only TOD distance from SVD VOR, but radial, you have to cross at TOD distance. Upper trigonometric nuts can look overwhelming, but actually it is very simple, so you need calculator only (and you'll need it anyway for 707, 727 flying)

I was PhD in Solid state physics two lives ago
Now i almost forgot how to divide with piece of paper and pen, but 727 gives me some chance to recall it, coz i dont use calculator inflight

As for real world, - NDB approaches not precise, so this numbers are used to have at least some control over approach and to stay within safe minimums, and surely in bad weather it helps not to get lost

So just quick calc will do the job fine

P.S. Lately i find out that VFR flying require much more planning using Google Sat photos  
I did VFR YBLN to YCUN in DC3, took a wrong turn on highway, and got lost No triangles could help in that case  

Thats something real interesting to fly. i'll definitely try it

P.S. Im still having some difficulties to stay on 3x profile, not a big problem, im working on it Just need more concentration, while flying, and talking to ATC

Yep. Thanks! Its really interesting to dig how it all done. It makes flying FSX interesting