Definition
The set of predictable errors and behaviors of a magnetic compass in flight, caused by the way Earth's magnetic field acts on the compass card during acceleration, deceleration, and turns. The main characteristics are magnetic dip, northerly turning error, southerly turning error, and acceleration/deceleration error (ANDS).
Plain English
These are the quirks of the magnetic compass. It does not always show heading correctly when the airplane is turning or changing speed. Pilots learn these quirks so they can read the compass properly.
Context Anchor
Seen in instrument flying when making compass turns, checking heading information, or using the magnetic compass when other heading instruments are unavailable or being checked.
Derivation
Characteristic comes from a Greek word meaning a distinguishing mark or feature. That helps here because compass characteristics are the distinguishing behaviors of the compass—the ways it predictably acts in flight, not random mistakes.
Why Pilots Care
Knowing these behaviors lets a pilot complete accurate timed turns to a heading using only the magnetic compass and turn coordinator.
Grounding Statement
In a turn, the airplane may be changing direction smoothly, while the magnetic compass may lag, lead, or swing before it settles.
Intuition Check
Do not read “characteristics” as a vague description or personality trait. In this context, it means specific, predictable compass behaviors that can affect the heading shown to the pilot.
Example Sentence 1
During partial-panel practice, the instructor reviewed compass characteristics before asking the student to roll out on a north heading.
Example Sentence 2
When accelerating on an east heading the pilot watches for the compass to momentarily swing toward north.