Are QDM and QDR the same as 'inbound' and 'outbound' courses?
QDM is the magnetic bearing to the station.
QDR is the magnetic bearing from the station.


Not to be confused with course, which is the direction in which the aircraft is moving but has nothing to do with the heading of the aircraft. Imagine having a heading of 270 but a course of 090. That means there is so much headwind that you are moving backwards.

Radials are not the same since a radial is always a magnetic bearing from the station. Therefore flying the radial 180 both inbound and outbound will both give you a position south of the station.

This is not the case with QDM and QDR.


Flying a QDM 180 will give you a position north of the station and flying 180 (without taking the wind into account) towards the station.
Flying a QDR 180 will give you a position south of the station and flying 180 (without taking the wind into account) away from the station.


Let's imagine a VOR and an NDB located on top of each other and there is no wind factor:


Flying QDM 180 will put you on radial 000 with a heading of 180.
Flying QDR 180 will put you on radial 180 with a heading of 180.
Flying radial 180 inbound will put you on QDM 000 with a heading of 000.
Flying radial 180 outbound will put you on QDR 180 with a heading of 180.


Long story short, radials are visualised in relation to the beacon. QDM/QDR are magnetic bearings visualised in relation to the plane's nose.