FAA Private Pilot Airplane (PAR)Navigation and Flight PlanningHard
A pilot is planning a VFR flight using a GPS receiver. To ensure the accuracy and reliability of the GPS signal, what information should the pilot check regarding RAIM (Receiver Autonomous Integrity Monitoring)?
- AThat the GPS unit has the latest software update.
- BThat the RAIM prediction for the intended flight path and time is available and adequate.
- CThat the GPS system is receiving signals from at least 12 satellites.
- DThat the GPS unit is connected to an external WAAS antenna.
Show answer & explanationAnswer & explanation
Correct answer: B. That the RAIM prediction for the intended flight path and time is available and adequate.
For non-WAAS GPS units, RAIM (Receiver Autonomous Integrity Monitoring) is crucial for ensuring the integrity of the GPS signal. Pilots must check RAIM availability for their intended flight path and time, especially for IFR operations, as a RAIM 'NOT AVAILABLE' warning indicates that the GPS signal may not meet the required integrity for navigation.
Why the other options are wrong
- A. Software updates are important but do not directly address the real-time integrity monitoring provided by RAIM.
- C. While more satellites generally improve accuracy, RAIM availability is determined by a minimum number (typically 5, or 4 with baro-aiding) and geometric dilution of precision, not just the total count.
- D. Connecting to a WAAS antenna makes RAIM less critical as WAAS provides superior integrity monitoring, but the question implies a non-WAAS scenario or a general check of RAIM.
RAIM (Receiver Autonomous Integrity Monitoring)
A technology within GPS receivers that monitors the integrity of the GPS signals to ensure they meet the accuracy requirements for a given phase of flight.
- Required for IFR operations with non-WAAS GPS.
- Requires a minimum of 5 satellites (or 4 with baro-aiding) to function.
- Alerts the pilot if the integrity of the GPS signal is compromised.
- Pilots must perform a RAIM prediction check prior to flight for IFR operations.
Memory trick: RAIM: 'R'eal-time 'A'lerts for 'I'ntegrity 'M'onitoring.