Revision QuestionsRadio Navigation — DGCA CPL practice questions

Question 1 of 243

VDF — which emergency frequency most commonly used for position fix?

A.121.500 MHz

B.243.000 MHz

C.156.8 MHz

D.406 MHz

All 243 questions — Revision Questions

Radio Navigation · DGCA CPL. The correct option is marked on each.

Q1. VDF — which emergency frequency most commonly used for position fix?
- A.121.500 MHz✓
- B.243.000 MHz
- C.156.8 MHz
- D.406 MHz
Why: — VDF is triggered when aircraft transmits on 121.500 MHz . Ground DF equipment takes a bearing on the transmission.
Q2. Aircraft equipment needed for VDF let-down:
- A.VHF radio only✓
- B.VOR receiver
- C.VOR/DME
- D.Nothing — all ground-based
Why: — VDF needs only a VHF radio in the aircraft. All DF equipment is ground-based.
Q3. VDF station at 400 ft, aircraft at FL090. Max range?
- A.117 NM
- B.124 NM
- C.134 NM✓
- D.140 NM
Why: — 1.23×(√400+√9000)=1.23×(20+94.9)=1.23×114.9= 141 NM . Nearest = 140 NM (d). [Answer key = c for variant with 325/8000 ft: 1.23×(18+89)=134 NM]
Q4. VDF accuracy class 'A':
- A.±1°✓
- B.±2°
- C.±5°
- D.±10°
Why: — VDF Class A: ±1° . Class B: ±2°. Class C: ±5°. Class D: ±10°.
Q5. VDF uses which propagation:
- A.Sky wave
- B.Ground wave
- C.Line of sight✓
- D.Surface wave
Why: — VDF VHF: line of sight propagation .
Q6. Wavelength of 375 kHz NDB signal:
- A.8 m
- B.80 m
- C.800 m✓
- D.8000 m
Why: — λ=300,000,000/375,000= 800 m .
Q7. NDB signal pattern:
- A.30 Hz polar diagram
- B.Omni-directional✓
- C.Bi-lobal
- D.Beam rotating at 30 Hz
Why: — NDB radiates omni-directionally . The ADF loop aerial is directional.
Q8. ADF accuracy within DOC by day:
- A.±1°
- B.±2°
- C.±5°✓
- D.±10°
Why: — ADF accuracy by day: ±5° .
Q9. Night effect on ADF worst at:
- A.Midday
- B.Midnight
- C.Dawn and dusk✓
- D.Noon and midnight
Why: — Night effect (sky wave interference) worst at dawn and dusk when D-layer dissolves.
Q10. Two NDBs — 20 NM from coast vs 50 NM inland. Greatest coastal refraction error?
- A.20 NM beacon
- B.50 NM inland beacon✓
- C.Equal at RB 090/270
- D.Equal at RB 000/180
Why: — Beacon further inland produces more coastal refraction — signal crosses coast at more oblique angle.
Q11. NDB range doubling — power increase needed:
- A.4×
- B.8×
- C.16×✓
- D.2×
Why: — Power ∝ Range⁴. Double range: power = 2⁴ = 16 .
Q12. Quadrantal error in ADF caused by:
- A.Night effect
- B.Metallic airframe re-radiating signal✓
- C.Coastal refraction
- D.Precipitation static
Why: — Quadrantal error: metallic airframe refracts/re-radiates signal at 45° quadrants.
Q13. ADF action for bearing — which aerials?
- A.Loop only
- B.Sense only
- C.Both loop and sense✓
- D.Neither — automatic
Why: — ADF needs both loop (directional null) and sense (resolve 180° ambiguity) .
Q14. Coastal error worst when beacon is:
- A.Inland, acute angle to coast✓
- B.Inland, 90° to coast
- C.Close to coast, acute angle
- D.Close to coast, 90° to coast
Why: — Worst: inland beacon, signal at acute angle to coastline .
Q15. Most significant ADF error:
- A.Quadrantal error
- B.Mountain effect
- C.Night effect✓
- D.Coastal refraction
Why: — Night effect (sky wave) is most significant ADF error.
Q16. ADF bearing inaccuracies caused by: (select best group)
- A.Static interference, height, SA
- B.Mountain effect, SA, night effect
- C.Lack of warning, station interference, static✓
- D.Coastal refraction, slant range, night effect
Why: — Valid ADF errors: lack of failure warning, station interference, static interference (also night, coastal, QE, mountain).
Q17. NDB frequency band:
- A.250–450 kHz
- B.190–1750 kHz✓
- C.108–117.95 MHz
- D.329–335 MHz
Why: — NDB: 190–1750 kHz (LF/MF).
Q18. BFO switch on ADF used when:
- A.Always on
- B.Required for NON emission beacons to produce audible ident✓
- C.Increases range
- D.Reduces quadrantal error
Why: — BFO needed for NON (unmodulated CW) beacons — heterodynes the carrier to produce audible ident tone.
Q19. VOR bearing measurement principle:
- A.Phase comparison✓
- B.Switched cardioids
- C.DDM
- D.Pulse technique
Why: — VOR: phase comparison between 30 Hz FM reference and 30 Hz AM variable.
Q20. VOR variation applied at:
- A.Aircraft for both
- B.VOR station for radial; aircraft for ADF✓
- C.VOR station for both
- D.Aircraft for VOR; station for ADF
Why: — VOR radials referenced to magnetic north at station . ADF uses variation at aircraft .
Q21. Aircraft flies due south of VOR. Var at station 13°W. Radial?
- A.167°
- B.180°
- C.193°✓
- D.347°
Why: — True bearing from station = 180° (south). Magnetic radial = 180° + 13°W = 193° .
Q22. VOR radial 250 selected, CDI 5 dots left (1 dot = 2°). OBS to centre?
- A.240
- B.260✓
- C.250
- D.245
Why: — 5 dots left = 10° right of track. Select 250+10 = 260° .
Q23. VOR frequency band:
- A.190–1750 kHz
- B.108–117.95 MHz✓
- C.329–335 MHz
- D.960–1215 MHz
Why: — VOR: 108–117.95 MHz VHF .
Q24. VOR ident tone frequency:
- A.400 Hz
- B.1020 Hz✓
- C.1350 Hz
- D.3000 Hz
Why: — VOR ident: 1020 Hz Morse every 10 s. DME ident: 1350 Hz.
Q25. VOR scalloping caused by:
- A.Mountains
- B.Multipath/terrain reflections✓
- C.Night effect
- D.Precipitation
Why: — Scalloping: multipath propagation from reflections.
Q26. DVOR advantage over CVOR:
- A.Higher power
- B.More channels
- C.Less siting error/scalloping✓
- D.Greater range
Why: — DVOR: electronic rotation → less siting error and scalloping .
Q27. VOT should indicate on any radial:
- A.000° FROM✓
- B.180° FROM
- C.090° TO
- D.Varies by position
Why: — VOT: always 000° FROM (or 180° TO) .
Q28. VOR reference phase transmitted as:
- A.30 Hz AM direct
- B.30 Hz FM on 9960 Hz sub-carrier✓
- C.50 Hz modulation
- D.400 Hz sub-carrier
Why: — Reference: 9960 Hz sub-carrier FM at 30 Hz , omni. Variable: 30 Hz AM rotating pattern.
Q29. VORTAC: civil aircraft uses:
- A.TACAN bearing only
- B.VOR bearing + TACAN DME✓
- C.VOR only
- D.TACAN DME only
Why: — Civil: VOR bearing + TACAN DME .
Q30. VOR site error typical maximum:
- A.±1°
- B.±3°✓
- C.±5°
- D.±10°
Why: — VOR site error (terrain reflections): up to ±3° .
Q31. VOR cone of confusion unreliable signals begin at approximately:
- A.Directly overhead
- B.45° elevation
- C.30° elevation✓
- D.10° elevation
Why: — Cone of confusion starts at ≈ 30° elevation above VOR.
Q32. En-route VOR DOC:
- A.25 NM
- B.50 NM
- C.100 NM
- D.200 NM✓
Why: — En-route VOR: 200 NM .
Q33. OBS 090° TO, CDI centred, heading 080°. Aircraft:
- A.On 090° radial heading to VOR
- B.On 270° radial heading to VOR✓
- C.On 270° radial heading away
- D.On 090° radial heading away
Why: — 090° TO = aircraft on 270° radial. CDI centred. Heading 080° ≈ toward VOR → 270° radial, heading toward VOR .
Q34. VOR emission type:
- A.NON
- B.A9W✓
- C.F3N
- D.P0N
Why: — VOR: A9W .
Q35. DVOR — rotating pattern produced by:
- A.Rotating aerial mechanism
- B.Electronic switching of aerial array✓
- C.Doppler shift of carrier
- D.FM modulation of sub-carrier
Why: — DVOR: electronic switching of aerial array (no moving parts → less siting error).
Q36. ILS localizer frequency band (odd decimals only):
- A.108–117.95 MHz
- B.108–111.975 MHz✓
- C.329–335 MHz
- D.960–1215 MHz
Why: — LOC: 108–111.975 MHz VHF , odd-decimal tenths.
Q37. ILS glideslope frequency band:
- A.108–111.975 MHz
- B.329–335 MHz✓
- C.960–1215 MHz
- D.75 MHz
Why: — G/S: 329–335 MHz UHF .
Q38. ILS glideslope usable range:
- A.5 NM
- B.10 NM✓
- C.15 NM
- D.25 NM
Why: — G/S usable range: 10 NM .
Q39. ILS: aircraft at 3° G/S, 10 NM from threshold. Height?
- A.2000 ft
- B.2500 ft
- C.3000 ft✓
- D.3500 ft
Why: — 3×10×100 = 3000 ft .
Q40. ILS false glideslope strongest at:
- A.1.5× nominal
- B.2× nominal
- C.3× nominal✓
- D.5× nominal
Why: — False G/S strongest at 3× nominal angle (≈9° for 3° slope).
Q41. ILS LOC DDM on centreline:
- A.Maximum
- B.Zero✓
- C.Half-scale
- D.150%
Why: — On centreline: 90 Hz = 150 Hz → DDM = zero .
Q42. ILS outer marker: tone and light:
- A.3000 Hz dots, white
- B.400 Hz dashes, blue✓
- C.1300 Hz alt, amber
- D.400 Hz dashes, amber
Why: — OM: 400 Hz dashes, blue . MM: 1300 Hz, amber. IM: 3000 Hz, white.
Q43. ILS CAT I minima:
- A.DH 200 ft, RVR 550 m
- B.DH 200 ft, RVR 800 m✓
- C.DH 100 ft, RVR 400 m
- D.DH 100 ft, RVR 200 m
Why: — CAT I: DH 200 ft, RVR 800 m .
Q44. ILS CAT II minima:
- A.DH 200 ft, RVR 800 m
- B.DH 100 ft, RVR 400 m✓
- C.DH 50 ft, RVR 200 m
- D.No DH, RVR 50 m
Why: — CAT II: DH 100 ft, RVR 400 m .
Q45. ILS CAT IIIC minima:
- A.DH 100 ft, RVR 200 m
- B.DH 50 ft, RVR 75 m
- C.No DH, RVR 50 m
- D.No DH, no RVR minimum✓
Why: — CAT IIIC: no DH, no RVR minimum .
Q46. Glideslope bar deflects UP — aircraft is:
- A.Above glidepath
- B.On glidepath
- C.Below glidepath✓
- D.Left of centreline
Why: — Bar UP = 150 Hz dominant = aircraft below glidepath — fly up.
Q47. LOC CDI deflects RIGHT — aircraft is:
- A.Right of centreline
- B.Left of centreline✓
- C.On centreline
- D.Above glidepath
Why: — CDI right = selected course is right = aircraft is left of centreline — fly right.
Q48. 90 Hz dominant on glideslope — aircraft is:
- A.Above glidepath✓
- B.Below glidepath
- C.On centreline
- D.Left of LOC
Why: — 90 Hz dominant on G/S = aircraft above glidepath — fly down.
Q49. ILS marker beacon carrier frequency:
- A.108 MHz
- B.75 MHz✓
- C.329 MHz
- D.1090 MHz
Why: — All ILS markers: 75 MHz carrier .
Q50. ILS 3° G/S at 4.6 NM (50 ft threshold elevation). Height?
- A.1380 ft
- B.1400 ft
- C.1430 ft✓
- D.1500 ft
Why: — 3×4.6×100+50=1380+50= 1430 ft .
Q51. ILS back course — CDI sense:
- A.Normal
- B.Reversed✓
- C.Glideslope only works
- D.No change
Why: — Back course LOC: CDI sense reversed — fly opposite needle.
Q52. ILS glideslope auto-paired when:
- A.Manually entered on FMC
- B.LOC VHF frequency selected✓
- C.ILS button pressed on autopilot
- D.Both LOC and GS frequencies entered
Why: — G/S automatically paired when LOC VHF frequency selected .
Q53. ILS glidepath accuracy requirement:
- A.±0.5° either side of nominal✓
- B.±1.0°
- C.±0.25°
- D.±2°
Why: — G/S accuracy: ±0.5° of nominal slope.
Q54. ILS LOC beam width adjusted to give:
- A.±2.5° fixed
- B.±3° fixed
- C.±35% of runway threshold width✓
- D.±5° fixed
Why: — LOC width: ±35% of threshold width (variable ≈±2°–6°).
Q55. ILS glidepath signal: DDM = 0.175 at:
- A.Course line
- B.Half-scale deflection
- C.Full-scale deflection✓
- D.False glidepath
Why: — Full-scale deflection DDM = 0.155 . [0.175 may appear in some variants — check exam wording]
Q56. ILS CAT IIIB minima:
- A.DH <50 ft, RVR 50–200 m✓
- B.No DH, no RVR
- C.DH 100 ft, RVR 200 m
- D.DH 50 ft, RVR 200 m
Why: — CAT IIIB: DH below 50 ft, RVR 50–200 m .
Q57. Middle marker approximately:
- A.4–7 NM from threshold
- B.1050 m from threshold✓
- C.300 m from threshold
- D.At decision height point
Why: — MM: ≈ 1050 m from threshold.
Q58. ILS number of channels (40-channel system):
- A.200
- B.252
- C.40✓
- D.108
Why: — ILS: 40 channels . MLS: 200. DME: 252.
Q59. ILS LOC emission type:
- A.NON
- B.A9W✓
- C.F3N
- D.P0N
Why: — LOC: A9W .
Q60. ILS outer marker located:
- A.300 m from threshold
- B.1050 m from threshold
- C.4–7 NM from threshold✓
- D.10 NM from threshold
Why: — OM: 4–7 NM from threshold.
Q61. PRF 400 pps. Maximum radar range:
- A.162 NM
- B.200 NM
- C.203 NM✓
- D.240 NM
Why: — 81,000/400 = 202.5 ≈ 203 NM .
Q62. PRF 250 pps. Max range:
- A.162 NM
- B.200 NM
- C.324 NM✓
- D.405 NM
Why: — 81,000/250 = 324 NM .
Q63. PRF 500 pps. Max range:
- A.81 NM
- B.162 NM✓
- C.324 NM
- D.243 NM
Why: — 81,000/500 = 162 NM .
Q64. Echo received 740 µs after transmission. Range:
- A.30 NM
- B.45 NM
- C.60 NM✓
- D.90 NM
Why: — 740/12.36 = 59.9 ≈ 60 NM .
Q65. Pulse width 2 µs. Minimum range:
- A.150 m
- B.300 m✓
- C.600 m
- D.900 m
Why: — 2×150 = 300 m .
Q66. Pulse width 0.03 µs (ASMI). Minimum range:
- A.0.45 m
- B.4.5 m✓
- C.45 m
- D.450 m
Why: — 0.03×150 = 4.5 m .
Q67. Minimum range determined by:
- A.PRF
- B.Transmitter power
- C.Pulse width✓
- D.Beamwidth
Why: — Min range = PW(µs) × 150 m → determined by pulse width .
Q68. Maximum range determined by:
- A.Pulse width
- B.PRF✓
- C.Beamwidth
- D.Transmitter power
Why: — Max range = 81,000/PRF → determined by PRF .
Q69. Azimuth resolution improved by:
- A.Wider beam
- B.Narrower beam✓
- C.Higher PRF
- D.Shorter pulse
Why: — Better azimuth resolution: narrower beamwidth .
Q70. Radial resolution improved by:
- A.Narrower beam
- B.Shorter pulse width✓
- C.Higher power
- D.Lower PRF
Why: — Better radial resolution: shorter pulse width .
Q71. MTI removes:
- A.Second trace returns
- B.Stationary clutter✓
- C.Rain
- D.Side lobe returns
Why: — MTI (Moving Target Indication): removes stationary clutter via Doppler.
Q72. Second trace returns removed by:
- A.MTI
- B.Increasing power
- C.Jittering PRF✓
- D.Reducing beamwidth
Why: — Second trace returns: jittering (varying) PRF .
Q73. AWR frequency:
- A.3000 MHz
- B.9375 MHz✓
- C.13300 MHz
- D.35000 MHz
Why: — AWR: 9375 MHz (SHF, 3.2 cm) .
Q74. AWR is classified as:
- A.Secondary radar
- B.CW radar
- C.Primary radar✓
- D.Doppler radar
Why: — AWR: primary radar .
Q75. AWR colour — weakest precipitation:
- A.Magenta
- B.Red
- C.Yellow
- D.Green✓
Why: — Weakest: Green (0.7–4 mm/h). Black = nothing.
Q76. AWR colour — turbulence/severe:
- A.Red
- B.Yellow
- C.Green
- D.Magenta✓
Why: — Turbulence: Magenta .
Q77. AWR MAP mode uses which beam up to 60–70 NM:
- A.Pencil beam
- B.Cosecant² (fan) beam✓
- C.Omni
- D.Scanning beam
Why: — MAP mode: cosecant² fan beam up to 60–70 NM.
Q78. AWR CONT mode shows:
- A.Increased gain
- B.Rainfall rate zone boundaries✓
- C.Map features
- D.Turbulence only
Why: — CONT: zone boundaries — steepest gradient = most hazardous.
Q79. AWR HOLD function:
- A.Freezes antenna
- B.Freezes display for storm movement assessment✓
- C.Holds gain
- D.Holds range
Why: — HOLD: freezes display to assess storm movement (compare after 2–3 min).
Q80. AWR shadow area:
- A.Area under aircraft
- B.Area behind heavy precipitation✓
- C.Below the beam
- D.Overhead cone
Why: — Shadow: region behind heavy rain — attenuated beam reveals nothing beyond.
Q81. AWR hook/U/finger return on display indicates:
- A.Light rain
- B.Snow
- C.Hail and severe turbulence✓
- D.CAT
Why: — Hook, U, finger shapes: hail and severe turbulence — avoid.
Q82. AWR stabilisation prevents:
- A.False targets
- B.Multipath
- C.Display distortion during manoeuvres✓
- D.Second trace returns
Why: — Stabilisation: prevents display distortion during pitch/roll .
Q83. ASMI scan rate:
- A.6 rpm
- B.15 rpm
- C.60 rpm✓
- D.120 rpm
Why: — ASMI: 60 rpm .
Q84. ASMI purpose:
- A.Long-range surveillance
- B.Aircraft and vehicle surface movement✓
- C.Weather detection
- D.Approach control
Why: — ASMI: surface movement — aircraft/vehicles on runways/taxiways.
Q85. Primary radar cannot determine:
- A.Range
- B.Bearing
- C.Identity✓
- D.Approximate speed (by track)
Why: — Primary radar: no identity — requires SSR transponder.
Q86. Super-refraction effect on radar:
- A.Reduces range
- B.Extends range beyond LOS✓
- C.Creates clutter
- D.Increases minimum range
Why: — Super-refraction: extends range beyond normal LOS (may cause spurious returns).
Q87. PRF 1000 pps. Echo at 1050 µs. Situation:
- A.Target at 85 NM — genuine
- B.Second trace return — actual 85 NM✓
- C.False target — reject
- D.Target at 4 NM
Why: — PRI=1000 µs. 1050 > PRI → second trace return . Actual range = 81 + 50/12.36 = 85 NM.
Q88. UK radar separation within 40 NM below FL245:
- A.1 NM
- B.2 NM
- C.3 NM✓
- D.5 NM
Why: — UK radar sep: 3 NM .
Q89. TAR maximum range:
- A.25 NM
- B.75 NM✓
- C.150 NM
- D.250 NM
Why: — TAR (Terminal Area Radar): 75 NM .
Q90. Max PRF for 50 km range:
- A.330 pps
- B.617 pps
- C.3000 pps✓
- D.1620 pps
Why: — PRF = 3×10⁸/(2×50,000) = 3000 pps .
Q91. DME frequency band:
- A.108–118 MHz
- B.329–335 MHz
- C.960–1215 MHz✓
- D.5031–5091 MHz
Why: — DME: UHF 960–1215 MHz .
Q92. DME transponder offset:
- A.±21 MHz
- B.±50 MHz
- C.±63 MHz✓
- D.±100 MHz
Why: — Ground transponder replies at ±63 MHz from interrogation frequency.
Q93. DME transponder delay:
- A.12.36 µs
- B.21 µs
- C.50 µs✓
- D.8 µs
Why: — Fixed delay: 50 µs . Receiver subtracts before computing range.
Q94. DME tracking phase pulse rate:
- A.27 ppps✓
- B.60 ppps
- C.150 ppps
- D.2700 ppps
Why: — Tracking: 27 ppps .
Q95. DME search phase pulse rate:
- A.27 ppps
- B.60 ppps
- C.150 ppps✓
- D.2700 ppps
Why: — Search: 150 ppps .
Q96. DME saturation approximately:
- A.27 ppps total
- B.2700 ppps ≈ 100 aircraft✓
- C.60 ppps total
- D.150 ppps total
Why: — Saturation: 2700 ppps ≈ 100 aircraft in tracking.
Q97. DME slant range error negligible when:
- A.Range > altitude (NM)
- B.Range (NM) > 3 × altitude (thousands ft)✓
- C.Always negligible
- D.Below 3000 ft
Why: — Negligible: Range (NM) > 3 × Alt (000s ft) .
Q98. Aircraft at FL180 directly over DME. Display reads:
- A.0 NM
- B.0.8 NM
- C.3 NM✓
- D.18 NM
Why: — 18,000/6076 = 2.96 ≈ 3 NM .
Q99. Time from interrogation to echo = 1300 µs. Range:
- A.98 NM
- B.100 NM
- C.101 NM✓
- D.103 NM
Why: — (1300−50)/12.36 = 1250/12.36 = 101.1 NM .
Q100. DME number of channels:
- A.40
- B.108
- C.200
- D.252✓
Why: — DME: 252 channels .
Q101. DME emission type:
- A.A9W
- B.P0N✓
- C.F3N
- D.NON
Why: — DME: P0N (pulsed, no info modulation).
Q102. VOR/DME pairing outside TMA — DME within:
- A.100 ft
- B.1 NM
- C.2000 ft✓
- D.2 NM
Why: — Outside TMA: DME within 2000 ft of VOR for auto-pairing.
Q103. VOR/DME pairing inside TMA — DME within:
- A.100 ft✓
- B.1 NM
- C.2000 ft
- D.2 NM
Why: — Inside TMA: DME within 100 ft of VOR.
Q104. DME jittered pulse pairs — purpose:
- A.Higher power
- B.Avoid ILS interference
- C.Identify own replies✓
- D.Increase range
Why: — Jittered pairs: aircraft identifies its own replies by consistent time offset.
Q105. DME squitter purpose:
- A.Ident
- B.Fill capacity to prevent aircraft re-entering search✓
- C.Range calibration
- D.Interference avoidance
Why: — Squitter: fills unused transponder capacity so aircraft detect station is active.
Q106. DME memory duration in tracking:
- A.5 s
- B.10 s✓
- C.15 s
- D.30 s
Why: — DME memory: 10 seconds .
Q107. DME/P accuracy:
- A.±0.5 NM
- B.±1 NM
- C.±100 ft✓
- D.±50 m
Why: — DME/P (Precision): ±100 ft for MLS CAT II/III.
Q108. DME/P used with:
- A.ILS
- B.MLS✓
- C.GBAS
- D.SBAS
Why: — DME/P used with MLS .
Q109. VORTAC: military aircraft uses:
- A.VOR bearing only
- B.VOR bearing + TACAN DME
- C.TACAN bearing + TACAN DME✓
- D.VOR only
Why: — Military at VORTAC: TACAN bearing + TACAN DME .
Q110. DME ident interval:
- A.Every 10 s
- B.Every 30 s✓
- C.Continuous
- D.Every 60 s
Why: — DME ident: every 30 seconds , 1350 Hz Morse.
Q111. DME type of radar:
- A.Primary
- B.Secondary✓
- C.Doppler
- D.CW
Why: — DME: secondary radar principle.
Q112. RNAV DME range shown to:
- A.Real DME station
- B.Phantom station (waypoint)✓
- C.Nearest airport
- D.FIX position
Why: — RNAV DME: shows distance to phantom station (waypoint) .
Q113. DME en-route accuracy:
- A.±0.25 NM
- B.±0.5 NM or ±3% (whichever greater)✓
- C.±1 NM
- D.±2%
Why: — DME accuracy: ±0.5 NM or ±3% , whichever greater.
Q114. GPS system uses what type of ranging?
- A.Secondary radar (2-way)
- B.One-way passive ranging✓
- C.Primary radar
- D.DME-type 2-way
Why: — GPS: one-way passive — satellite broadcasts, receiver measures time of arrival.
Q115. DME acquisition phase rate:
- A.27 ppps
- B.60 ppps✓
- C.150 ppps
- D.2700 ppps
Why: — Acquisition: 60 ppps .
Q116. Aircraft at 5000 ft AGL over DME. Slant range reads:
- A.0 NM
- B.0.82 NM✓
- C.2 NM
- D.5 NM
Why: — 5000/6076 = 0.82 NM .
Q117. DME squitter pulse rate (total with squitter):
- A.27 ppps
- B.2700 ppps✓
- C.150 ppps
- D.60 ppps
Why: — With squitter: maintained at 2700 ppps .
Q118. Which PRN codes does GPS L1 carry?
- A.P-code only
- B.C/A and P-code✓
- C.C/A code only (civil)
- D.SPS only
Why: — L1 (1575.42 MHz): carries both C/A code (civil) and P-code (military) .
Q119. DME ground transponder delay ensures:
- A.Collision avoidance
- B.Positive identification of own replies
- C.Positive time offset for range calculation✓
- D.Synchronisation with VOR
Why: — 50 µs delay ensures receiver always has positive elapsed time to subtract and compute range.
Q120. DME interrogation spacing (pulse pair):
- A.6 µs X-channel; 12 µs Y-channel
- B.12 µs X; 36 µs Y✓
- C.Random (jittered)
- D.Fixed at 12 µs
Why: — X-channel pair spacing: 12 µs . Y-channel: 36 µs .
Q121. SSR interrogation frequency:
- A.1030 MHz✓
- B.1090 MHz
- C.960 MHz
- D.1215 MHz
Why: — Ground interrogates on 1030 MHz .
Q122. SSR transponder reply frequency:
- A.1030 MHz
- B.1090 MHz✓
- C.960 MHz
- D.1215 MHz
Why: — Aircraft replies on 1090 MHz .
Q123. Mode A P1–P3 spacing:
- A.8 µs✓
- B.17 µs
- C.21 µs
- D.25 µs
Why: — Mode A: 8 µs .
Q124. Mode C P1–P3 spacing:
- A.8 µs
- B.17 µs
- C.21 µs✓
- D.25 µs
Why: — Mode C: 21 µs .
Q125. Mode A codes available:
- A.256
- B.4096✓
- C.65,536
- D.16,777,216
Why: — Mode A: 4096 (octal 0000–7777).
Q126. Mode S ICAO address size:
- A.12 bit
- B.16 bit
- C.24 bit✓
- D.32 bit
Why: — Mode S: 24-bit address → 16.7 million unique codes.
Q127. Mode C altitude resolution:
- A.100 ft✓
- B.50 ft
- C.25 ft
- D.10 ft
Why: — Mode C: 100 ft increments. Mode S: 25 ft.
Q128. Squawk 7700:
- A.Hijack
- B.Radio failure
- C.Emergency✓
- D.VFR
Why: — 7700 = Emergency .
Q129. Squawk 7600:
- A.Emergency
- B.Radio failure✓
- C.Hijack
- D.Military
Why: — 7600 = Radio failure (NORDO) .
Q130. Squawk 7500:
- A.Emergency
- B.Radio failure
- C.Unlawful interference/hijack✓
- D.VFR conspicuity
Why: — 7500 = Hijack/unlawful interference .
Q131. Garbling occurs when two aircraft within:
- A.0.5 NM
- B.1.7 NM same direction✓
- C.3 NM
- D.5 NM
Why: — Garbling: 1.7 NM in same direction from radar.
Q132. Fruiting caused by:
- A.Garbling
- B.Replies to other ground interrogators✓
- C.Multipath
- D.SA
Why: — Fruiting: aircraft replies to other stations' interrogations → phantom targets.
Q133. IDENT button — SPI duration:
- A.10 s
- B.20 s✓
- C.30 s
- D.60 s
Why: — SPI: 20 seconds .
Q134. SLS — P2 pulse is:
- A.Directional, same as P1
- B.Omnidirectional✓
- C.Higher power than P1
- D.On 1090 MHz
Why: — SLS P2: omnidirectional → if P2>P1, transponder suppresses reply (side lobe).
Q135. ISLS purpose:
- A.Prevent garbling
- B.Synchronise multiple interrogators to prevent fruiting✓
- C.Improve altitude reporting
- D.Enable data link
Why: — ISLS: synchronises multiple ground SSR stations → prevents fruiting.
Q136. Transponder STANDBY:
- A.Reduced power response
- B.No response to interrogations✓
- C.Mode C only
- D.Mode S only
Why: — STANDBY: energised, will NOT respond .
Q137. UK VFR conspicuity squawk:
- A.2000
- B.7000✓
- C.7700
- D.1200
Why: — UK VFR: 7000 .
Q138. Mode S advantage:
- A.VHF frequencies
- B.Selective addressing — eliminates garbling✓
- C.No transponder needed
- D.No LOS needed
Why: — Mode S: selective addressing by unique 24-bit ICAO code.
Q139. ADS-B squitter interval:
- A.1 s
- B.0.5 s✓
- C.2 s
- D.10 s
Why: — ADS-B: every 0.5 seconds .
Q140. Mode C altitude referenced to:
- A.QNH
- B.QFE
- C.1013.25 hPa✓
- D.Local QNH
Why: — Mode C: always 1013.25 hPa .
Q141. SSR reply framing pulses F1–F2 spacing:
- A.8 µs
- B.12 µs
- C.20.3 µs✓
- D.50 µs
Why: — F1–F2: 20.3 µs .
Q142. ACAS/TCAS uses:
- A.Mode A
- B.Mode C
- C.Mode S✓
- D.All modes
Why: — TCAS: uses Mode S 1030/1090 MHz for A/C-to-A/C interrogation.
Q143. ELS (Elementary Surveillance) provides:
- A.Squawk and altitude
- B.Squawk, flight ID, altitude, emergency✓
- C.Full EHS data
- D.GPS position
Why: — ELS: squawk, callsign, pressure altitude, emergency .
Q144. EHS (Enhanced Surveillance) adds:
- A.Nothing over ELS
- B.Selected altitude, airspeed, magnetic heading✓
- C.GPS position
- D.TCAS data
Why: — EHS adds: selected altitude, airspeed, magnetic heading .
Q145. Squawk 2000 means:
- A.Emergency
- B.Entering CAS without clearance✓
- C.Military
- D.Radio failure
Why: — 2000: entering CAS without prior ATC clearance .
Q146. SSR antenna location:
- A.Separate tower
- B.On top of primary radar, co-rotating✓
- C.Inside fuselage
- D.Alongside ILS building
Why: — SSR antenna: mounted on top of primary radar, co-rotating .
Q147. Mode S data link direction:
- A.Downlink only
- B.Uplink only
- C.Bidirectional✓
- D.No data link
Why: — Mode S: bidirectional (downlink + uplink).
Q148. Transponder ALT mode:
- A.Responds Mode A only
- B.Responds Mode A + C (altitude)✓
- C.Mode S only
- D.STANDBY
Why: — ALT mode: responds to Mode A and Mode C .
Q149. ADS-B position source:
- A.SSR ranging
- B.DME
- C.GPS✓
- D.Transponder timing
Why: — ADS-B: broadcasts GPS-derived position via 1090 MHz extended squitter.
Q150. Minimum range for no garbling:
- A.0.5 NM
- B.1.7 NM✓
- C.3 NM
- D.5 NM
Why: — No garbling when separation > 1.7 NM in same direction.
Q151. AWR wavelength:
- A.1 cm
- B.3.2 cm✓
- C.10 cm
- D.23 cm
Why: — AWR: 3.2 cm (9375 MHz) .
Q152. AWR MAN mode beam:
- A.Fan beam at all ranges
- B.Pencil beam, manual gain✓
- C.Omni
- D.Fan beam beyond 70 NM
Why: — MAN: pencil beam, manual gain .
Q153. AWR cannot detect:
- A.Thunderstorms
- B.Hail
- C.CAT✓
- D.Heavy rain
Why: — AWR cannot detect CAT (Clear Air Turbulence) — no precipitation.
Q154. AWR tilt positive (+) means:
- A.Beam below horizontal
- B.Beam above horizontal✓
- C.No tilt
- D.Gain increased
Why: — Positive tilt = beam above horizontal .
Q155. AWR: rain shadow risk is:
- A.Light rain conceals nothing
- B.Heavy rain attenuates beam — severe weather beyond may be hidden✓
- C.Snow creates shadow
- D.Shadow only below aircraft
Why: — Rain shadow: severe weather may be hidden behind heavy precipitation .
Q156. AWR 'finger' return shape indicates:
- A.Light rain
- B.Hail/severe turbulence✓
- C.Snow
- D.CAT
Why: — Finger shape: hail and severe turbulence .
Q157. AWR scalloped edges on return indicate:
- A.Ground return
- B.Hail✓
- C.Light rain
- D.Icing
Why: — Scalloped edges: hail .
Q158. AWR AGC/STC range:
- A.Up to 25 NM✓
- B.All ranges
- C.Beyond 70 NM
- D.First 5 NM only
Why: — STC (Swept Gain/AGC): equalises returns up to ≈25 NM .
Q159. AWR stabilisation failure — display effect:
- A.Blanks
- B.Lopsided during bank/pitch✓
- C.Gains increase
- D.Range rings disappear
Why: — Stabilisation failure: display becomes lopsided during manoeuvres .
Q160. MLS frequency band:
- A.VHF 108–118 MHz
- B.UHF 329–335 MHz
- C.SHF 5031–5090.7 MHz✓
- D.UHF 960–1215 MHz
Why: — MLS: SHF 5031–5090.7 MHz .
Q161. MLS azimuth coverage:
- A.±20°
- B.±35°
- C.±40°✓
- D.±60°
Why: — MLS azimuth: ±40° of centreline.
Q162. MLS channels:
- A.40
- B.100
- C.200✓
- D.252
Why: — MLS: 200 channels .
Q163. MLS principle:
- A.DDM like ILS
- B.TRSB — time between TO/FRO sweeps✓
- C.Phase comparison
- D.Doppler
Why: — MLS: TRSB (Time Referenced Scanning Beam) .
Q164. MLS glide slope range:
- A.Fixed 3°
- B.0.9° to 20°✓
- C.2° to 10°
- D.Fixed 5°
Why: — MLS G/S: 0.9° to 20° selectable.
Q165. MLS ident prefix letter:
- A.I
- B.M✓
- C.V
- D.D
Why: — MLS ident: prefix M .
Q166. MLS range measurement:
- A.Pulse echo timing
- B.DME/P built-in✓
- C.Phase comparison
- D.Doppler
Why: — MLS range: DME/P (±100 ft accuracy).
Q167. MLS advantage over ILS — azimuth coverage:
- A.±35° same as ILS
- B.±40° vs ±35°✓
- C.360°
- D.±20°
Why: — MLS: ±40° vs ILS ±35°.
Q168. MLS UK usable range:
- A.10 NM
- B.15 NM
- C.20 NM✓
- D.35 NM
Why: — MLS UK: 20 NM .
Q169. AWR U-shape return:
- A.Light rain
- B.Hail/turbulence✓
- C.Snow
- D.CAT
Why: — U-shape: hail and turbulence .
Q170. AWR MAP mode optimal up to:
- A.25 NM
- B.60–70 NM✓
- C.150 NM
- D.All ranges
Why: — MAP (cosecant² beam): up to 60–70 NM .
Q171. ASMI frequency band:
- A.3 GHz
- B.9.375 GHz
- C.15–17 GHz✓
- D.35 GHz
Why: — ASMI: 15–17 GHz (SHF, ≈2 cm) .
Q172. AWR WEA colour for no precip:
- A.Green
- B.Yellow
- C.Red
- D.Black✓
Why: — No precipitation: Black .
Q173. AWR hook return on display:
- A.Light drizzle
- B.Hail/severe turbulence✓
- C.CAT
- D.Snow
Why: — Hook shape: hail/severe turbulence .
Q174. AWR ageing (HOLD) — how long before compare?
- A.30 s
- B.1 min
- C.2–3 min✓
- D.10 min
Why: — Deselect HOLD after 2–3 minutes — compare images for storm movement.
Q175. AWR pencil beam — used in MAN mode beyond:
- A.25 NM
- B.50 NM
- C.60–70 NM✓
- D.150 NM
Why: — Pencil beam (MAN) for weather beyond 60–70 NM .
Q176. AWR — recommended tilt when far from storm cell:
- A.Tilt down to surface
- B.Zero tilt
- C.Tilt up✓
- D.Reduce gain
Why: — Far from cell: tilt up to see tops — determines storm height/severity.
Q177. SSR transponder receives on ___, replies on ___:
- A.1090, 1030
- B.1030, 1090✓
- C.960, 1215
- D.1215, 960
Why: — RX: 1030 MHz , TX: 1090 MHz .
Q178. EGNOS is classified as:
- A.LAAS
- B.GBAS
- C.SBAS✓
- D.RAIM
Why: — EGNOS: SBAS (Satellite Based Augmentation System) .
Q179. LAAS/GBAS transmits corrections via:
- A.Satellite
- B.HF radio
- C.VHF data link✓
- D.UHF beacon
Why: — LAAS/GBAS: VHF data link .
Q180. SBAS — corrections transmitted via:
- A.Dedicated HF stations
- B.Geostationary satellites✓
- C.VHF data link
- D.L-band beacons
Why: — SBAS: corrections via geostationary satellites .
Q181. B-RNAV required accuracy:
- A.±1 NM, 95%
- B.±5 NM, 95%✓
- C.±5 NM, 90%
- D.±2 NM, 95%
Why: — B-RNAV: ±5 NM on 95% of occasions .
Q182. P-RNAV required accuracy:
- A.±1 NM, 95%✓
- B.±5 NM, 95%
- C.±0.5 NM, 95%
- D.±2 NM, 90%
Why: — P-RNAV: ±1 NM on 95% of occasions .
Q183. FMC navigation database update cycle:
- A.7 days
- B.14 days
- C.28 days (AIRAC)✓
- D.90 days
Why: — FMC nav DB: 28 days (AIRAC cycle) .
Q184. RNAV erratic: aircraft beyond LOS of reference VOR/DME:
- A.True✓
- B.False
- C.Only in TMA
- D.Only in cone of confusion
Why: — Yes — beyond LOS or DOC of reference VOR/DME → erratic RNAV .
Q185. GPS horizontal accuracy (SPS, 95%):
- A.±100 m
- B.±22 m
- C.±13 m✓
- D.±50 m
Why: — Horizontal: ±13 m (95%) .
Q186. GPS vertical accuracy (SPS, 95%):
- A.±13 m
- B.±22 m✓
- C.±50 m
- D.±100 m
Why: — Vertical: ±22 m (95%) .
Q187. GPS time accuracy (SPS, 95%):
- A.1 µs
- B.40 ns✓
- C.100 ns
- D.1 ms
Why: — Time: 40 nanoseconds (95%) .
Q188. GPS — why pseudo-range not true range?
- A.Ionospheric delay
- B.Receiver clock error not yet eliminated✓
- C.SA applied
- D.Multipath
Why: — Pseudo-range: uncorrected for receiver clock error .
Q189. GPS minimum SVs for 3D fix + time:
- A.3
- B.4✓
- C.5
- D.6
Why: — 4 SVs for 3D fix (lat, lon, alt, time).
Q190. GPS RAIM — SVs for fault detection only:
- A.4
- B.5✓
- C.6
- D.7
Why: — RAIM detection: 5 SVs .
Q191. GPS RAIM — SVs for fault exclusion:
- A.4
- B.5
- C.6✓
- D.7
Why: — RAIM exclusion: 6 SVs .
Q192. GPS orbital height:
- A.19,099 km
- B.20,180 km✓
- C.23,222 km
- D.35,800 km
Why: — GPS: 20,180 km .
Q193. GPS orbital inclination:
- A.55°✓
- B.56°
- C.63°
- D.65°
Why: — GPS: 55° inclination.
Q194. GPS orbital period:
- A.24 h
- B.12 h
- C.11 h 56 min✓
- D.11 h 15 min
Why: — GPS: 11 h 56 min .
Q195. GPS L1 frequency:
- A.1227.6 MHz
- B.1575.42 MHz✓
- C.1602 MHz
- D.1246 MHz
Why: — GPS L1: 1575.42 MHz .
Q196. GPS L2 frequency:
- A.1227.6 MHz✓
- B.1575.42 MHz
- C.1602 MHz
- D.1246 MHz
Why: — GPS L2: 1227.6 MHz .
Q197. GPS geoid reference:
- A.PZ90
- B.ETRS89
- C.WGS84✓
- D.GRS80
Why: — GPS: WGS84 .
Q198. GLONASS geoid reference:
- A.WGS84
- B.PZ90✓
- C.ETRS89
- D.GRS80
Why: — GLONASS: PZ90 .
Q199. Galileo geoid reference:
- A.WGS84
- B.PZ90
- C.ETRS89✓
- D.GRS80
Why: — Galileo: ETRS89 .
Q200. GLONASS orbital inclination:
- A.55°
- B.56°
- C.63.4°
- D.65°✓
Why: — GLONASS: 65° .
Q201. GLONASS orbital period:
- A.11 h 56 min
- B.11 h 15 min✓
- C.12 h
- D.14 h 8 min
Why: — GLONASS: 11 h 15 min .
Q202. Galileo orbital height:
- A.20,180 km
- B.19,099 km
- C.23,222 km✓
- D.35,800 km
Why: — Galileo: 23,222 km .
Q203. GPS almanac used by receiver to:
- A.Determine SA
- B.Compute position
- C.Identify which SVs visible✓
- D.Correct clock error
Why: — Almanac: receiver determines which SVs are above horizon for faster acquisition.
Q204. GPS ephemeris — sub-frames:
- A.1
- B.2 and 3✓
- C.4 and 5
- D.5
Why: — Ephemeris data: sub-frames 2 and 3 .
Q205. GPS navigation message transmitted at:
- A.50 Hz✓
- B.1 kHz
- C.9960 Hz
- D.1575 MHz
Why: — Nav message: 50 Hz (50 bps) modulation on L1 and L2.
Q206. GNSS altitude cannot be used alone for DH/MDA because:
- A.GPS too inaccurate
- B.WGS84 ellipsoid differs from geoid (MSL) by up to 50 m✓
- C.Update rate too slow
- D.ILS always more accurate
Why: — WGS84 ellipsoid ≠ MSL geoid → difference up to 50 m .
Q207. SBAS geostationary orbit altitude:
- A.20,180 km
- B.19,099 km
- C.23,222 km
- D.35,800 km✓
Why: — Geostationary: 35,800 km .
Q208. GPS dual-frequency advantage:
- A.Higher power
- B.Eliminates ≈99% ionospheric error✓
- C.Better coverage
- D.Faster acquisition
Why: — Dual-frequency (L1+L2): eliminates ≈99% of ionospheric error .
Q209. GPS integrity warning time (non-precision approach):
- A.2 s
- B.8 s✓
- C.30 s
- D.10 s
Why: — Non-precision: 8 seconds . Precision (CAT I): 6 s. ILS equivalent: 2 s.
Q210. 4D RNAV adds to 3D capability:
- A.Vertical guidance
- B.GPS
- C.Timing (RTA)✓
- D.TCAS
Why: — 4D RNAV: lateral + vertical + timing (RTA) .
Q211. FMC auto-tunes DMEs for:
- A.Nearest station
- B.Pilot's selection
- C.Best geometry (angle of cut)✓
- D.Highest power stations
Why: — FMC selects DMEs for best angle of cut .
Q212. External input to FMC:
- A.INS
- B.Pressure altitude
- C.Compass
- D.VOR/DME✓
Why: — External (ground-based): VOR/DME .
Q213. ADC input to FMC:
- A.Heading
- B.Groundspeed
- C.TAS✓
- D.Position
Why: — ADC provides: TAS, pressure altitude, SAT .
Q214. RNAV course line computer function:
- A.Direct to VOR/DME facility
- B.Rho/theta → track and distance to waypoint✓
- C.ILS approach guidance
- D.TCAS alerting
Why: — RNAV: uses rho/theta to compute track + distance to phantom waypoint .
Q215. GPS range measurement: time measured from:
- A.Receiver to SV and back
- B.SV to receiver (one-way)✓
- C.Control segment to SV
- D.SV to control segment
Why: — GPS: one-way time from SV to receiver.
Q216. GPS number of orbital planes:
- A.3
- B.4
- C.6✓
- D.8
Why: — GPS: 6 orbital planes , 4 SVs each = 24 SVs.
Q217. GLONASS number of orbital planes:
- A.3✓
- B.4
- C.6
- D.8
Why: — GLONASS: 3 orbital planes , 8 SVs each = 24 SVs.
Q218. Galileo number of orbital planes:
- A.3✓
- B.4
- C.6
- D.8
Why: — Galileo: 3 orbital planes , 10 SVs each = 30 SVs.
Q219. GPS C/A code chipping rate:
- A.1.023 MHz✓
- B.10.23 MHz
- C.50 Hz
- D.9960 Hz
Why: — C/A code: 1.023 MHz . P-code: 10.23 MHz.
Q220. Selective Availability (SA):
- A.Still active on civilian GPS
- B.Intentional degradation of SPS; switched off in 2000✓
- C.Used only by military
- D.Replaced by RAIM
Why: — SA: switched off 2 May 2000 . No longer applied.
Q221. RNAV erratic most likely cause:
- A.Cone of confusion of phantom
- B.Beyond DOC/LOS of reference VOR/DME✓
- C.FMC failure
- D.INS drift
Why: — Most likely: beyond DOC or LOS of reference VOR/DME .
Q222. P-RNAV accuracy requirement:
- A.±5 NM, 95%
- B.±1 NM, 95%✓
- C.±0.5 NM, 95%
- D.±1 NM, 99%
Why: — P-RNAV: ±1 NM, 95% .
Q223. Multi-sensor FMC + GPS discrepancy — action:
- A.Trust GPS
- B.Trust multi-sensor; display multi-sensor output✓
- C.Select nearest VOR
- D.Declare emergency
Why: — Discrepancy: trust multi-sensor ; GPS may have failed.
Q224. GBAS/LAAS accuracy for CAT I:
- A.±16 m horizontal, ±6 m vertical✓
- B.±100 ft
- C.±0.5 NM
- D.Same as ILS
Why: — GBAS CAT I: ±16 m horizontal, ±6 m vertical (95%) .
Q225. GPS constellation: total operational SVs:
- A.21
- B.24✓
- C.27
- D.30
Why: — GPS: 24 SVs (operational); up to 32 with spares.
Q226. GALILEO constellation: total SVs:
- A.24
- B.27
- C.30✓
- D.32
Why: — Galileo: 30 SVs .
Q227. GLONASS constellation:
- A.21
- B.24✓
- C.27
- D.30
Why: — GLONASS: 24 SVs .
Q228. GPS PRN codes — how many available?
- A.24
- B.32✓
- C.64
- D.252
Why: — GPS PRN codes: 32 available (SVs numbered PRN 1–32).
Q229. GNSS integrity definition:
- A.Accuracy of the position solution
- B.Ability to alert users when system should not be used✓
- C.Number of SVs visible
- D.Signal continuity
Why: — Integrity: ability to provide timely warning when system unfit for navigation.
Q230. RAIM — what does it detect?
- A.Ionospheric error
- B.Failed SV causing position error exceeding limits✓
- C.Multipath
- D.Clock drift in receiver
Why: — RAIM detects: failed SV causing excessive position error .
Q231. GPS almanac download time:
- A.30 s
- B.12.5 min✓
- C.30 min
- D.1 hour
Why: — Full almanac download: 12.5 minutes (25 frames × 30 s).
Q232. GPS cold start — time to first fix:
- A.30 s
- B.1–2 min
- C.12.5 min✓
- D.Up to 30 min
Why: — Cold start (no almanac): up to 12.5 min for almanac download.
Q233. PDOP (Position Dilution of Precision) — best geometry:
- A.High PDOP
- B.Low PDOP✓
- C.PDOP = 1 always
- D.PDOP irrelevant
Why: — Best geometry: low PDOP (SVs spread widely across sky).
Q234. GPS ionospheric model corrects approximately:
- A.10%
- B.50%✓
- C.75%
- D.99%
Why: — GPS ionospheric model: ≈50% correction. Dual-freq: ≈99%.
Q235. SBAS integrity monitoring provided by:
- A.Ground reference stations✓
- B.Control segment only
- C.RAIM
- D.Aircraft receiver
Why: — SBAS: network of ground reference stations monitors satellite integrity.
Q236. Galileo orbital inclination:
- A.55°
- B.56°✓
- C.63°
- D.65°
Why: — Galileo: 56° .
Q237. GPS Week Number rollover issue — period:
- A.10.9 years (1024 weeks)✓
- B.19.7 years
- C.7 years
- D.Every year
Why: — GPS week: 10-bit number → rolls over every 1024 weeks (≈19.7 years) . [Some say 19.7 — check ICAO doc for exact value used]
Q238. GNSS continuity of service — definition:
- A.System accuracy
- B.Probability of system performing without interruption during operation✓
- C.Integrity
- D.Number of SVs
Why: — Continuity: probability of uninterrupted operation during intended use .
Q239. GNSS availability — definition:
- A.Accuracy spec
- B.Proportion of time system provides navigation with required accuracy✓
- C.Integrity
- D.Continuity
Why: — Availability: proportion of time system meets accuracy and integrity requirements .
Q240. GPS L1 C/A code — chip length:
- A.30 m
- B.300 m✓
- C.1 km
- D.3 km
Why: — C/A chip length = c/f = 3×10⁸/1.023×10⁶ = 293 m ≈ 300 m .
Q241. GNSS approach — LPV (Localizer Performance with Vertical guidance) provides:
- A.Lateral only
- B.Lateral + baro-VNAV
- C.Lateral + SBAS vertical guidance (like ILS CAT I)✓
- D.No approach minima
Why: — LPV: SBAS approach with lateral + SBAS vertical guidance , minima approaching CAT I.
Q242. GPS time offset from UTC at receiver:
- A.Zero — GPS = UTC
- B.GPS ahead of UTC by integer seconds (leap seconds)✓
- C.GPS behind UTC
- D.Varies daily
Why: — GPS time: ahead of UTC by integer leap seconds . Receiver subtracts leap second count to display UTC.
Q243. GNSS — which error source causes errors of hundreds of metres without correction?
- A.Multipath
- B.Clock error
- C.Selective Availability (when active)✓
- D.Tropospheric delay
Why: — When SA active: errors up to 100 m (horizontal). SA now off.