When must a pilot actively monitor the alternate navigation means?

• A. Only during IFR operations
• B. When RAIM capability is lost
• C. During all phases of flight using GPS
• D. Only when WAAS is unavailable

Answer: (C)

Using GPS as your primary navigation source means you must continually verify you can navigate with an alternative means if GPS becomes unreliable. GPS integrity can be compromised by satellite outages, interference, or RAIM warnings, and WAAS availability can vary. Because these issues can occur at any time, you should actively monitor other navigation sources (such as VOR, DME, Localizer/DME, or inertial guidance) throughout all portions of the flight when GPS is in use. This readiness to revert to an alternate means keeps you prepared for any GPS degradation or failure, not just during specific phases or under particular conditions.