VOR and Doppler VOR

What does a VOR give you, and why did it take over from the NDB?

A bearing from the station

• 360 radials • A vor (VHF omnidirectional range) is a radio station on the ground that sends out 360 radials, like the spokes of a wheel • It tells you your radial: your magnetic bearing from the station, wherever you are round it
• Why VHF • 108–117.95 MHz: VHF travels in straight lines, with no sky wave and almost no static • So unlike the NDB it is good day and night, but only within line of sight
• What it is used for • Marking airways (start, end, centre line) · position lines en route · a fix to hold over · let-downs to airfields • With a DME beside it you get bearing and distance at once: rho-theta (rho = distance, theta = angle)
• VOR or localiser? • 108–112 MHz is shared: an even first decimal (108.2, 108.25…) is a VOR, an odd one (108.1, 108.35…) a localiser • Memory aid "LOVE": Localiser Odd, VOR Even • 112–117.95 MHz: VOR only, a channel every 0.05 MHz

How can one beacon tell every aircraft a different bearing?

The lighthouse

• A lighthouse • Think of a lighthouse: a beam turns clockwise, and a lamp flashes all round each time the beam points at magnetic north • Everyone sees the flash at the same moment; the beam reaches each person at a different time
• Time it • See the flash, then count until the beam reaches you • The longer the wait, the further round from north you are: the wait is your bearing
• The radio version • The VOR sends two 30 Hz signals. The reference signal is the same everywhere: it is the flash • The variable signal comes from a turning pattern: it is the beam, so its timing depends on where you are • The set measures the gap between them, the phase difference: that is your radial (phase comparison)
• Move the aircraft • Due magnetic north of the station the two peaks line up: R360 • Anywhere else the variable signal lags by exactly your radial, in degrees. Move the aircraft and watch

Worked questions: the phase difference tells you the radial

Phase difference is the radial

This lesson is part of the Navigation plan. See plans

How do you know the VOR is the right one, and working?

Ident, monitoring and types

This lesson is part of the Navigation plan. See plans

How far can you trust a VOR?

Range, DOC and accuracy

This lesson is part of the Navigation plan. See plans

What is a Doppler VOR, and what happens overhead?

Doppler VOR and the cone

This lesson is part of the Navigation plan. See plans

How does the needle know where the course is?

The needle

This lesson is part of the Navigation plan. See plans

Why is the HSI easier to read than the OBS?

HSI and OBS

This lesson is part of the Navigation plan. See plans

Fly from A to B, VOR at A, B on R050 — and back

A to B on one radial

This lesson is part of the Navigation plan. See plans

Worked questions: OBS 080 — needle sense for four aircraft, and outbound on R060

Which way the needle goes

This lesson is part of the Navigation plan. See plans

Worked questions: OBS 080 — which aircraft get TO and which FROM?

TO or FROM

This lesson is part of the Navigation plan. See plans

Worked questions: going inbound on R060 (and R280) — which course to set?

Inbound and reverse sensing

This lesson is part of the Navigation plan. See plans

Free VOR simulator: fly a real Cessna in 3D, tune a VOR and find your way home

VOR simulator

• You are flying • A real Cessna over real-looking country, with eight VOR stations standing in their fields • ← → steer · ↑ nose down · ↓ nose up · W S faster and slower. On a phone: the stick and the lever
• Tune and turn • Set the frequency with the MHz and kHz knobs, press ⇄, press IDENT to hear its Morse. Or tap the station on the Chart • The CRS knob is on the instrument, bottom right, as on a real HSI. Drag it, or tap its left or right side
• Get lost • Lost flights: you do not know where you are. Tower gives a frequency. Find the station, the airfield, the lake • No guides unless you pay a star for them. Wind, hills that block the signal, three-leg trips

Worked questions: how many degrees is the needle off, and the airway edge

Dots and degrees

This lesson is part of the Navigation plan. See plans

Worked questions: the heading bug, where the aircraft is, and drift

Heading bug, and "heading does not matter"

This lesson is part of the Navigation plan. See plans

OBS 330, 3 dots fly right, FROM. QDM?

Q1: three dots fly right

This lesson is part of the Navigation plan. See plans

Worked questions: heading 287°M with 14° starboard drift; heading 280 on R180

Phase and OBS questions

This lesson is part of the Navigation plan. See plans

Worked questions: radial 120, heading 300, OBS 330 — and radial 225, heading 090, OBS 190

Q5 and Q6: the CDI

This lesson is part of the Navigation plan. See plans

Solve it: TO/FROM, needle side and dots

Solve it: the CDI

This lesson is part of the Navigation plan. See plans

How do you join a new radial?

Intercepting a radial

This lesson is part of the Navigation plan. See plans

What does the bar do as you fly through a VOR?

Inbound, overhead, outbound

This lesson is part of the Navigation plan. See plans

How is a hold flown, and how do you join it?

Holding patterns

This lesson is part of the Navigation plan. See plans

Test yourself on chapter 39

Test yourself

This lesson is part of the Navigation plan. See plans