Radio Navigation AidsAir Navigation — DGCA CPL practice questions
Question 1 of 10
A VOR operates in the frequency band:
All 10 questions — Radio Navigation Aids
Air Navigation · DGCA CPL. The correct option is marked on each.
Q1. A VOR operates in the frequency band:
- A.190–1750 kHz (LF/MF)
- B.108–117.95 MHz (VHF)✓
- C.960–1215 MHz (UHF)
- D.75 MHz (VHF)
Why: VOR (VHF Omnidirectional Range) operates in the VHF band between 108 and 117.95 MHz, providing 360 radials referenced to magnetic north.
Q2. A VOR radial is defined as:
- A.A bearing TO the VOR
- B.A bearing FROM the VOR✓
- C.The aircraft heading to reach the VOR
- D.A great circle from the VOR
Why: A VOR radial is always measured FROM the station. Radial 090 runs due East of the VOR. To fly TO a VOR, the inbound course equals the reciprocal of the radial.
Q3. DME (Distance Measuring Equipment) provides:
- A.Bearing from a ground station
- B.Slant range distance to the ground transponder✓
- C.Aircraft altitude above terrain
- D.Groundspeed only when passing directly overhead
Why: DME measures the slant range (not ground distance) between the aircraft and the ground transponder. Slant range error is negligible at low elevation angles but significant directly overhead.
Q4. ADF (Automatic Direction Finder) homes to NDB signals and displays:
- A.QDM to the station
- B.Relative bearing — angle between aircraft heading and direction to station✓
- C.Absolute true bearing to station
- D.Range to the station
Why: The ADF needle points to the NDB and shows relative bearing (RB) — angle clockwise from the aircraft's nose to the NDB. QDM = magnetic heading to the station = aircraft HDG (magnetic) + RB (adjusted for 360°).
Q5. ILS localiser provides:
- A.Vertical guidance only
- B.Lateral guidance (left/right of runway centreline)✓
- C.Both lateral and vertical guidance
- D.Distance to runway threshold
Why: The ILS localiser transmits on VHF (108–111.95 MHz) and provides lateral (left/right) deviation guidance for runway centreline alignment. The glide slope provides vertical guidance.
Q6. The glide slope of a standard ILS is set at:
- A.1° to 2°
- B.2.5° to 3.5° (nominal 3°)✓
- C.5° to 6°
- D.Variable per approach
Why: Standard ILS glide slope is nominally 3° (range 2.5°–3.5°). Steeper angles (up to 5.5°) are published for terrain/obstacle clearance at specific airports.
Q7. GPS RAIM (Receiver Autonomous Integrity Monitoring) is used to:
- A.Improve GPS signal strength
- B.Detect GPS satellite faults that could cause position errors✓
- C.Provide vertical guidance
- D.Correct for magnetic variation
Why: RAIM uses redundant satellite geometry to self-monitor GPS integrity. If a satellite fault is detected, RAIM alerts the pilot — critical for IFR navigation where integrity is required.
Q8. NDB (Non-Directional Beacon) transmits in the:
- A.VHF band (108–136 MHz)
- B.LF/MF band (190–1750 kHz)✓
- C.UHF band (960–1215 MHz)
- D.HF band (3–30 MHz)
Why: NDBs operate in the Low Frequency / Medium Frequency band (190–1750 kHz). The lower frequency allows longer range and bending over terrain but makes them susceptible to static and night effect.
Q9. Line-of-sight (LoS) limitation applies to which navigation aids?
- A.NDB and ADF
- B.VOR, DME, and ILS✓
- C.HF radio beacons
- D.Loran-C
Why: VHF/UHF navigation aids (VOR, DME, ILS, TACAN) are limited to line-of-sight. Coverage range = 1.25 × √(altitude in feet) NM approximately. LF/MF aids like NDBs are not LoS-limited.
Q10. The CDI (Course Deviation Indicator) on a VOR shows full-scale deflection at:
- A.5°
- B.10°✓
- C.15°
- D.20°
Why: Standard VOR CDI full-scale deflection = ±10° from the selected course. Each dot represents approximately 2°. When flying an ILS localiser, full-scale = ±2.5° (more sensitive).