Definition
An outbound magnetic bearing (MB) is the magnetic direction measured from an NDB (non-directional beacon) station outward to the aircraft. It describes the line, expressed in degrees magnetic, that runs from the station out to where the aircraft is or will be positioned, as opposed to an inbound bearing which runs from the aircraft toward the station.
Plain English
It is the direction, in degrees on a magnetic compass, that points from the radio beacon out to the airplane. Inbound bearings point toward the station; outbound bearings point away from it.
Context Anchor
Seen in instrument navigation when using a bearing to intercept or track away from a navigation station.
Derivation
Outbound' simply means 'heading outward' — away from the station. 'Magnetic bearing' is the direction measured against magnetic north rather than true north. Naming the bearing by the direction it points (away from the station) is the convention pilots use to describe tracks relative to NDBs.
Why Pilots Care
Allows precise tracking of a desired course away from a navigation station during enroute or approach segments.
Intuition Check
Do not read outbound MB as the direction to the station. Outbound means the bearing used after leaving the station, away from it.
Example Sentence 1
After station passage, the pilot turned to intercept the 045° outbound MB from the NDB.
Example Sentence 2
Wind correction was applied to maintain the 180 outbound MB during the departure.