If an HSI displays that NAV is inoperative, what does this indicate?

If an HSI displays that NAV is inoperative, what does this indicate?

• A. The function is active
• B. Data is being updated
• C. The HSI is malfunctioning
• D. The NAV function is inoperative

Answer: (D)

NAV inoperative means the navigation function feeding the HSI is not working. The HSI relies on navigation sources (like VOR/LOC or GPS) to drive the course needle and display; when the NAV subsystem is out of service, those nav signals can’t be used. This doesn’t imply the whole HSI is faulty, nor that data are actively being updated. It simply indicates the navigation data feature is unavailable, so you’d need to rely on non-nav instruments or backup navigation methods until the NAV function is restored.

NAV inoperative means the navigation function feeding the HSI is not working. The HSI relies on navigation sources (like VOR/LOC or GPS) to drive the course needle and display; when the NAV subsystem is out of service, those nav signals can’t be used. This doesn’t imply the whole HSI is faulty, nor that data are actively being updated. It simply indicates the navigation data feature is unavailable, so you’d need to rely on non-nav instruments or backup navigation methods until the NAV function is restored.