FAA Commercial Pilot Airplane (CAX)Navigation and Flight PlanningMedium
A pilot planning an IFR flight using GPS for primary navigation checks the receiver's RAIM prediction before departure. What is the purpose of this check?
- ATo determine the magnetic variation value being applied by the GPS unit
- BTo verify the navigation database is current for approach procedures
- CTo confirm the autopilot is properly coupled to the GPS receiver
- DTo confirm sufficient satellites are available to detect a position error along the route and at the destination
Show answer & explanationAnswer & explanation
Correct answer: D. To confirm sufficient satellites are available to detect a position error along the route and at the destination
Receiver Autonomous Integrity Monitoring (RAIM) verifies that enough satellites are in view with adequate geometry to detect a faulty signal, ensuring position integrity for IFR operations along the planned route and at the destination.
Why the other options are wrong
- A. Magnetic variation is a stored database value, not something RAIM evaluates.
- B. Database currency is a separate check unrelated to RAIM prediction.
- C. Autopilot coupling is a system function unrelated to satellite integrity monitoring.
RAIM (Receiver Autonomous Integrity Monitoring)
RAIM is a GPS receiver function that uses redundant satellite signals to detect and, in some units, exclude a faulty satellite, ensuring position integrity for IFR navigation.
- Requires at least 5 satellites for fault detection
- RAIM prediction should be checked before an IFR GPS flight
- A RAIM outage may require an alternate navigation method or delayed departure
Memory trick: RAIM = 'Reliable Aircraft Integrity Monitor' — checks satellites, not autopilot.