EASA ATPL — Radio Navigation (062) Exam Prep

Correct answer: C. DH less than 100 ft (or no DH), RVR not less than 200 m

ILS CAT IIIA: Decision Height less than 100 ft (or no DH), RVR not less than 200 m. For comparison: CAT I = DH ≥ 200 ft, RVR ≥ 550 m; CAT II = DH 100–200 ft, RVR ≥ 300 m; CAT IIIB = DH < 50 ft (or none), RVR ≥ 75 m; CAT IIIC = No DH, no RVR limit. CAT IIIA requires autoland capability and appropriate aircraft/crew certification.

Correct answer: B. By comparing the phase difference between a reference signal (omnidirectional 30 Hz) and a variable signal (rotating 30 Hz)

A Conventional VOR (CVOR) transmits two 30 Hz signals: a reference signal modulated on a 9,960 Hz subcarrier (transmitted omnidirectionally) and a variable signal (created by a rotating antenna pattern that produces a 30 Hz amplitude modulation whose phase varies with azimuth). The airborne receiver compares the phase difference between these two signals to determine the magnetic bearing (radial) from the station. A DVOR uses the Doppler principle but achieves the same phase comparison result.

Correct answer: C. A cone approximately 40–60° wide where bearings are unreliable

The Cone of Confusion (also called the Zone of Ambiguity) is a cone-shaped area directly above a VOR station where the bearing information becomes unreliable. It is approximately 40–60° wide (half-angle of about 20–30° from vertical). Inside this zone, the CDI and TO/FROM indicator will fluctuate as the aircraft passes overhead. The size of the cone decreases with increasing altitude above the station.

Correct answer: B. 63 MHz

DME uses a paired-frequency system where the ground station replies on a frequency offset by 63 MHz from the aircraft interrogation frequency. This prevents the aircraft receiver from picking up its own transmitted pulses. The DME operates in the 960–1,215 MHz (UHF) band. The aircraft transmitter sends paired pulses and measures the time between transmission and reception of the reply, subtracting the fixed 50-microsecond transponder delay.

Correct answer: C. The pseudo-range from at least four satellites using signal time of arrival

GPS receivers determine position by measuring the pseudo-range (apparent distance) to at least four satellites. Three satellites are needed to solve for the three unknown position coordinates (latitude, longitude, altitude), and a fourth is needed to solve for the receiver clock error. The pseudo-range is calculated from the time of arrival of each satellite's signal, knowing the speed of light. Each satellite transmits its precise position and an accurate time code.

Correct answer: C. Coastal refraction

Coastal refraction occurs when an NDB's radio waves cross a coastline at an angle other than 90°. The change in propagation speed between land and sea causes the wave front to bend (refract), similar to light entering a different medium. This bending causes the ADF to indicate a bearing that is biased towards a direction perpendicular to the coastline. The error is greatest when crossing the coast at shallow angles and at lower frequencies.