What data does the MCS's EHSI display?

• A. TACAN data only
• B. FMS data only
• C. A combination of TACAN data and FMS data
• D. Ground-based NAVAID data only

Answer: (C)

The main idea here is that the EHSI on the MCS is an integrated navigation display that brings in information from more than one source. It isn’t limited to one type of data. You’ll see TACAN information—such as bearing to a TACAN station and range/DME information—paired with data from the Flight Management System that reflects your active flight plan: the current leg, course, and waypoints. This combination gives you situational awareness for both ground-based radio navigation and your planned route, all on one screen.

If you relied on TACAN data alone, you’d miss the pilot’s route from the FMS. If you relied on FMS data alone, you’d lose the immediate TACAN bearing and distance information. Ground-based NAVAID data is part of TACAN/VOR information, but the EHSI is designed to display both TACAN and FMS data together, not just one source. So the display shows a combination of TACAN data and FMS data.