When an airport is known to have EFIS magnetic interference on takeoff select _____ on the COMPASS switches for takeoff and climb until the ________ is complete.

When an airport is known to have EFIS magnetic interference on takeoff select _____ on the COMPASS switches for takeoff and climb until the ________ is complete.

• A. HDG; climb
• B. NAV; ascent
• C. INS; approach
• D. MAG; takeoff

Answer: (D)

When the EFIS heading information could be distorted by magnetic interference, use a backup, independent heading source during the critical takeoff and initial climb. The magnetic compass (MAG) provides a standalone reference that isn’t tied to the EFIS sensors, so it remains reliable when the EFIS display or sensors are unreliable. By selecting MAG on the COMPASS switches for takeoff and climb, you ensure the aircraft’s heading reference stays stable as you lift off and establish the initial climb. Keep using MAG until the takeoff is complete, then you can revert to the normal heading source once you’re clear of the interference and the EFIS can provide accurate data again.

When the EFIS heading information could be distorted by magnetic interference, use a backup, independent heading source during the critical takeoff and initial climb. The magnetic compass (MAG) provides a standalone reference that isn’t tied to the EFIS sensors, so it remains reliable when the EFIS display or sensors are unreliable. By selecting MAG on the COMPASS switches for takeoff and climb, you ensure the aircraft’s heading reference stays stable as you lift off and establish the initial climb. Keep using MAG until the takeoff is complete, then you can revert to the normal heading source once you’re clear of the interference and the EFIS can provide accurate data again.