Definition 1 of 2
Definition
A magnetic compass that displays heading information on a vertical card behind a fixed lubber line, showing the aircraft's heading directly under the index in the same way as a heading indicator. It uses a magnet assembly mounted to drive a vertical card display, eliminating most of the reading and turning errors associated with the traditional liquid-filled whiskey compass.
Plain English
A magnetic compass that shows the aircraft's heading on an upright dial, much like the face of a heading indicator, instead of on a floating disk seen edge-on through a small window.
Context Anchor
Seen on the instrument panel as the airplane’s magnetic direction reference, often used in place of or alongside a traditional magnetic compass.
Derivation
Named for how the compass card is presented. Traditional magnetic compasses use a horizontal card viewed from the side; this design rotates the presentation to vertical so the pilot reads it head-on, like other panel instruments.
Why Pilots Care
Gives stable heading information during turns and is less affected by acceleration errors than liquid-filled compasses.
Intuition Check
“Vertical card” does not mean the compass points up and down. It means the compass information is displayed on an upright card facing the pilot.
Example Sentence 1
After the heading indicator failed, the pilot used the vertical card compass to maintain a steady course back to the airport.
Example Sentence 2
With the electrical system failed, the vertical card compass became the only reliable source of magnetic heading.