Definition
The downward tilt of the Earth's magnetic field lines as they approach the magnetic poles, which causes a magnetic compass needle to angle downward rather than lie flat. This vertical pull on the compass needle is the underlying cause of the turning and acceleration errors a pilot sees in a magnetic compass.
Plain English
The Earth's magnetic field doesn't just point north — near the poles it also points down into the ground. That downward pull tips the compass needle, and that tipping is what makes the compass behave oddly during turns and speed changes.
Context Anchor
Seen in magnetic compass discussions, especially when learning northerly turning errors in instrument flying.
Derivation
From Latin 'magneticus' (magnetic) and Old English 'dyppan' (to dip or plunge downward). 'Dip' captures the idea perfectly: the needle is being pulled downward, not just sideways. Knowing that helps a pilot picture what the field is actually doing to the float inside the compass.
Why Pilots Care
It creates predictable compass errors in turns and requires specific pilot techniques to maintain accurate headings.
Analogy
Think of a compass as being pulled in two directions at once: sideways toward magnetic north and partly downward. That downward pull can make the compass tilt and misread during motion.
Grounding Statement
Imagine the Earth's magnetic field as lines running from pole to pole. Near the equator they run roughly horizontal, so the compass needle sits flat. Near the poles they plunge into the ground, so the needle wants to follow them downward — and that tilt is what throws the compass off during maneuvers.
Intuition Check
Magnetic dip does not mean the airplane is dipping. It means Earth’s magnetic field itself is sloping downward or upward, and that slope affects the compass.
Example Sentence 1
Magnetic dip is why the compass momentarily shows a turn toward south when the aircraft accelerates on an easterly heading.
Example Sentence 2
Pilots account for magnetic dip by using the timed turn method rather than relying solely on the magnetic compass during instrument flight.