What does HSI stand for in aviation instrumentation?

• A. Head-Up Indicator
• B. Horizontal Situation Indicator
• C. High- Speed Indicator
• D. Helicopter System Interface

Answer: (B)

Horizontal Situation Indicator is the navigation instrument that combines your heading with the course you’re flying, all on one horizontal display. It shows a fixed aircraft symbol and a rotating compass card, with a course deviation indicator that tells you how far left or right you are from the selected course. You can select a course from navigation sources like VOR/LOC or GPS, and the CDI automatically shows deviation from that course. This integration lets you see your direction and how to adjust to stay on the intended track at a glance, which is why it’s the correct expansion. The other options don’t fit as they aren’t standard aviation navigation instruments: a head-up indicator is not what HSI stands for in this context, a high-speed indicator isn’t a typical flight instrument, and a helicopter system interface isn’t used to define HSI.