Do aircraft using GPS navigation need an alternate means of navigation?

• A. Yes
• B. No
• C. Only for en-route navigation
• D. Not necessary if RAIM is available

Answer: (A)

Using GPS as the primary navigation method introduces a potential single point of failure. GPS signals can be lost or degraded for various reasons—satellite geometry, receiver malfunctions, interference, or atmospheric conditions—so you must be prepared to navigate by another means if GPS becomes unavailable. Even with RAIM monitoring, which checks receiver integrity, it does not guarantee that GPS will always be usable; it only alerts you when integrity is compromised.

Therefore, in IFR operations you should have an alternate navigation capability available so you can determine your position and continue the flight or execute procedures without GPS. This alternate could be a conventional system like VOR/DME, NDB, or an inertial navigation system, or another approved backup method.

The other choices aren’t correct because the requirement isn’t limited to en-route portions only, and it isn’t eliminated by RAIM being available. Redundancy is a general safety requirement when GPS is used for navigation.