Hi Bob,
Two quick questions, both regarding page 5.41 IREX book
(1) 3rd paragraph down on RHS - Q) where does the time 2.5 mins come from if you don't have a DME
(2) Last paragraph on same page - Q) If you've approached from the South now using a DME, having followed the arc and now established on 042', should the MDA be 4100ft for S-I NDB/DME instead of 4150 S-I NDB
(not considering actual QNH)
Thanks for your help
Gareth
Gidday Gareth
If you don't have a DME, you would have to time the outbound leg from station passage. You can use your own watch or the aircraft's clock for the timing. Many ADFs have a stop-watch function which makes timing a bit easier. Also in some cases, GPS can be used if you don't have a DME. If this is permissible, there will be a note on the approach plate.
As you can see there are two MDAs given. 4150 if you are flying the approach without DME, and 4100 if you have a DME. The example is assuming that you don't have a DME. You could still take 100 off those figures if you can get the actual QNH.
