Definition
An automatic direction finder (ADF) instrument whose compass card is fixed in position, with 0 (N) permanently at the top of the dial. The single needle points toward the tuned non-directional beacon (NDB) and shows the relative bearing — the angle from the aircraft's nose clockwise to the station — but does not display the magnetic bearing directly. The pilot must mentally add the relative bearing to the aircraft's magnetic heading to determine the magnetic bearing to the station.
Plain English
A type of ADF gauge where the dial doesn't rotate — north stays at the top no matter which way the aircraft is pointed. The needle shows how far left or right of the nose the radio station is, and the pilot does the math to figure out the actual compass direction to it.
Context Anchor
Seen in instrument flying when using an ADF to navigate to or from a non-directional beacon, often called an NDB.
Derivation
Fixed-card' simply means the card (the dial face with numbers) is fixed — it does not rotate. Contrasted with the movable-card ADF, where the card turns with the aircraft heading so the needle reads magnetic bearing directly.
Why Pilots Care
On a fixed-card ADF, the needle alone does not tell you the direction to the station — only the angle relative to the nose. Forgetting to add the heading leads to flying the wrong direction toward an NDB, which is a classic source of error during partial-panel and instrument approach work.
Grounding Statement
On a fixed-card ADF, the top of the dial represents the airplane's nose, and the needle points toward the beacon relative to that nose.
Intuition Check
Do not assume the fixed card works like a compass that automatically shows direction over the ground. On a fixed-card ADF, the card stays still and the needle shows direction relative to the airplane.
Example Sentence 1
Tracking the NDB on the fixed-card ADF, the pilot read a relative bearing of 030 and added it to the magnetic heading of 090 to determine a magnetic bearing of 120 to the station.
Example Sentence 2
With the aircraft on a heading of 270 and the fixed-card ADF needle at 180, the NDB station lay directly behind the aircraft.