CPL Navigation and Radio Aids 3 — Questions and Answers
Question 1: What does RAIM stand for and what does it do?
- Radar Altitude Integrity Monitor; verifies altitude accuracy via radar
- Receiver Autonomous Integrity Monitoring; detects faulty GPS satellite signals using redundant satellite data (Correct answer)
- Remote Area Instrument Maintenance; certifies GPS receivers for remote operations
- Radio Altitude Integrity Measurement; cross-checks GPS altitude against radar altimeter
Correct answer: Receiver Autonomous Integrity Monitoring; detects faulty GPS satellite signals using redundant satellite data
RAIM (Receiver Autonomous Integrity Monitoring) compares signals from multiple GPS satellites to detect when one is transmitting erroneous data.
Question 2: On an RNAV (GPS) approach chart, 'LNAV' minima provide:
- Lateral and vertical guidance equivalent to a Category I ILS
- Lateral guidance only, flown to a minimum descent altitude (MDA) (Correct answer)
- Lateral guidance with advisory vertical guidance, flown to a decision altitude
- Full precision approach guidance with baro-VNAV
Correct answer: Lateral guidance only, flown to a minimum descent altitude (MDA)
LNAV (Lateral Navigation) provides horizontal course guidance only; it is a non-precision approach flown to an MDA.
Question 3: During the en route phase of flight, GPS CDI full-scale deflection represents:
- ±0.3 NM
- ±1.0 NM
- ±2.0 NM
- ±5.0 NM (Correct answer)
Correct answer: ±5.0 NM
En route GPS CDI sensitivity is ±5 NM full scale, narrowing to ±1 NM in the terminal phase and ±0.3 NM on final approach.
Question 4: The primary advantage of WAAS (Wide Area Augmentation System) for GPS approaches is:
- It doubles the number of visible GPS satellites
- It provides glideslope-equivalent vertical guidance (LPV) without a ground-based transmitter (Correct answer)
- It allows GPS use in polar regions where standard GPS is unavailable
- It increases GPS signal range to 500 NM beyond normal coverage
Correct answer: It provides glideslope-equivalent vertical guidance (LPV) without a ground-based transmitter
WAAS provides differential correction signals via geostationary satellites, enabling LPV approaches with vertical guidance comparable to ILS without a glideslope transmitter.
Question 5: A Required Navigation Performance (RNP) value of 0.3 means the navigation system must:
- Keep the aircraft within 0.3 NM of the intended path for at least 95% of flight time, with onboard alerting (Correct answer)
- Maintain at least 3 GPS satellites in continuous view
- Ensure vertical accuracy within 0.3 ft at the decision altitude
- Provide autopilot coupling accurate to 0.3 NM
Correct answer: Keep the aircraft within 0.3 NM of the intended path for at least 95% of flight time, with onboard alerting
RNP 0.3 requires the total system error to remain within 0.3 NM of the intended track 95% of the time, with an onboard performance monitoring and alerting capability.
Question 6: A RAIM warning appears immediately before the final approach fix (FAF) on a GPS approach. The correct pilot action is to:
- Continue the approach at a higher MDA as a precaution
- Discontinue the GPS approach and execute a missed approach (Correct answer)
- Reduce airspeed to allow satellite geometry to improve
- Switch to ILS frequency and continue the descent to the same minimums
Correct answer: Discontinue the GPS approach and execute a missed approach
Loss of RAIM before the FAF means GPS integrity cannot be verified; FAA regulations prohibit continuing a GPS approach without RAIM, so a missed approach must be executed.
Question 7: What is the minimum number of GPS satellites required for RAIM to provide approach-level integrity monitoring?
- 3 satellites
- 4 satellites
- 5 satellites (Correct answer)
- 6 satellites
Correct answer: 5 satellites
Approach-level RAIM requires at least 5 satellites (or 4 satellites plus a baro-altimeter aiding) to provide the redundancy needed to detect a faulty signal.
CPL Navigation and Radio Aids 3
What does RAIM stand for and what does it do?