G'day Bob,

Just wanted to validate my understanding of the essence of NDB coastal refraction - on page 1.8 of BT IREX July 2013 - picture of the NDB Signal path is over land and sea, and the explanation on the prior page is that the signal (if crossing the coast at an angle) bends TOWARDS the coastline.

Yet in the explanation under the diagram, its says that the "bottom aircraft would get an indicated bearing that was GREATER than the true bearing to the station" but if I look at the angle of the wave, would that not make it a bearing that was LESS than the current reading, given that the wave refracts TOWARDS the coast?

If that signal in the pic bends TOWARDS the coast, would that not result in a ADF reading that was LESS than if the signal had not been bent at all?

Brook

I try to think of it this way...

If we use the diagram where the coastline is running east/west as in the book, and the aircraft is flying from east to west then the indicated bearing TO the station should read something like 310 degrees.

Due coastal refraction, the bearing TO the station indicated on the aircrafts equipment (ADF) would read about 330 degrees. So the ADF indicated relative bearing is GREATER than the true bearing to the station.

If we look at the diagram with the coast running north to south, the book is saying that as the signal crosses the coast from the NDB, it will bend back towards the coastline. This causes the resultant signal to come from a more northerly direction so this is where the ADF thinks the station is.

Hope that helps.

Great answer Vedder. That's exactly it

Cheers,

Rich

Thanks Vedder - that's great! It makes perfect sense!