Magnetic Compass and Heading Instruments

Vocabulary flashcards covering variation, deviation, compass errors, and related cockpit instruments from the lecture notes.

Magnetic Compass

Primary cockpit instrument that shows aircraft heading; reliable only during straight-and-level, unaccelerated flight.

True North

The geographic North Pole; reference direction for true headings, separate from magnetic north.

Magnetic North

Point on Earth toward which a compass needle points; basis for magnetic headings and charts.

Variation

Angular difference between true north and magnetic north; used to convert true headings to magnetic (subtract easterly, add westerly).

“East is Least, West is Best”

Mnemonic for applying variation—subtract easterly variation, add westerly variation when converting true to magnetic headings.

Deviation

Compass error caused by magnetic fields within the aircraft; the difference between installed and uninstalled compass readings.

Heading Indicator (Directional Gyro)

Gyroscopic instrument that provides stable heading information; must be synchronized with the magnetic compass every 10–15 minutes in analog systems.

Magnetometer

Solid-state sensor in modern digital panels that detects Earth’s magnetic field and supplies heading data without manual syncing.

ANDS

Mnemonic for Northern Hemisphere acceleration error: Accelerate North, Decelerate South on east–west headings.

UNOS

Mnemonic for Northern Hemisphere turning error: Undershoot North, Overshoot South when rolling out of turns to northerly or southerly headings.

Acceleration Error (Northern Hemisphere)

Compass shows a false turn toward north when accelerating and toward south when decelerating on E/W headings.

Turning Error (Northern Hemisphere)

During turns, compass lags when approaching north and leads when approaching south, summarized by UNOS.

Straight-and-Level Flight

Flight condition with constant altitude and heading; the state in which the magnetic compass is most accurate.