Definition
The angle, measured downward from the horizontal, at which the Earth's magnetic field lines enter the surface of the Earth at a given location. Dip angle is near zero at the magnetic equator and approaches 90 degrees near the magnetic poles, where the field lines point almost straight down.
Plain English
How steeply the Earth's magnetic field tilts down into the ground at the spot where the aircraft is flying. Near the equator the field runs almost flat; near the poles it points almost straight down.
Context Anchor
Seen in magnetic compass discussions, especially when learning why compass indications can be wrong during acceleration, deceleration, and turns.
Derivation
From the everyday word 'dip,' meaning to slope or tilt downward. The magnetic field lines literally dip into the Earth, and the angle of that dip is what the term describes.
Why Pilots Care
The dip angle produces the northerly turning error and acceleration error that pilots must anticipate when using the magnetic compass.
Grounding Statement
Picture the magnetic field as invisible lines running from pole to pole. Near the equator they skim along parallel to the ground; as you fly north or south, they tilt downward more and more, until at the magnetic pole they plunge straight into the Earth.
Intuition Check
“Dip” does not mean the nose of the airplane is dropping here. It means Earth’s magnetic field is tilted relative to the level surface.
Example Sentence 1
Because dip angle increases as you fly toward the poles, compass turning errors become more pronounced at higher latitudes.
Example Sentence 2
Understanding the dip angle helps a pilot anticipate how the compass will swing during a turn from south to north.