VHF Omnidirectional Range
VOR
- VOR (VHF Omni Range) works primarily with three components:
- The station on the ground which transmits a signal.
- The antenna on the aircraft which receives the signal.
- The instrument in the aircraft that interprets the signal.
- VHF range 108.10 – 117.95Mhz
- Each station has its own frequency.
- Higher the receiver the longer the reception distance.
- 1.34 ×√AGL = reception range.
VOR indicator:
- TRACK – red line.
- TO/ FROM Flag (sometimes reads off-warning flag) – yellow line.
- DOTs: 2 degrees per dot, indicated degrees off track up to 10° maximum deflection of needle – green line.
- CDI: Course Deflection Indicator (needle) – blue line.
- OBS: Omni Bearing Selector – grey line.
Tune and Identifying VOR station
- Tuning in the VOR.
- The VOR works off the NAV portion of your VHF radio.
- Tune in the frequency for the desired station as found on the map.
- Identify the station.
- It’s important to identify the station to ensure that you are not going to be tracking the wrong station.
- Every VOR has it’s own identifier. This identifier is transmitted in Morse code (the identifier and Morse code is located on the map).
- After tuning in the station, turn up the volume and check that the identifier matches with that on the map.
Testing VOR with VOT
- First ensure that the VOR is not indicating an OFF flag.
- Tune in frequency (VOT) and indentify (Ex: YYZ VOT 114.8)
- Set track indicator to 360°
- The needle should be centered within 4°+or- with a from indication (180° TO) (and OFF indication indicates that the VOR is not serviceable).
- VOT is not available at every airport.
Testing VOR with prominent landmark
- Tune and identify.
- Fly over a know point (Set Heading Point for example).
- Identify on the map which radial the point is on.
- Set this radial on the track selector.
- The needle should be centered +or- 6° (FROM indication).
VOR: Radials
- The ground transmitter produces 360 electronic courses, each of which runs through the center of the station.
- Each course is aligned with a specific degree on the compass, with 0 degrees pointing north, 90 degrees pointing east, 270 degrees pointing west, and so on.
- Using your airborne VOR equipment, you can navigate on any one of these 360 courses while going directly to or from a VOR station.
- To determine what radial you are on:
- Tune and identify the station.
- Turn the OBS until the needle is centered and you have a FROM indication.
- The number read off the top of the display will be the radial you are on.
- Note: The VOR does not care which direction the aircraft is heading.
FROM and TO indications
- For any heading set on the top OBS, the VOR will give a FROM indication:
- if your position lies on the same side as the radial.
- The VOR will give a TO indication:
- If you are on the opposite side from the radial
Tracking directly TO the station
- Tune and indentify the station.
- Set the OBS: needle centered and TO indication.
- Follow the heading that is indicated on the TOP OBS (the radial you are will be the opposite and will be indicated on the BOTTOM OBS.
- Keep the needle centered.
- If the needle starts to move to the right: correct by turning to the right to get yourself back on track.
- If you do need to turn to get yourself back on track, don’t turn too much or you will find yourself overshooting your track and ending up having to correct back again. A correction of 10° is usually enough.
- As you get closer to the station the needle will become more sensitive.
- As you pass the station, the flag will change rapidly from TO to OFF to FROM.
- Note: It’s important that you do not track to the station with a FROM indication or track from the station with a TO indication. The VOR assumes that since you have it set with a TO flag that you are going to the station. Therefore, the correction that the CDI needle will show will be opposite if you are not tracking according to the flag.
- The easy to remember:
- ALWAYS FOLLOW THE HEADING ON THE TOP WHEN TRACKING DIRECTLY TO OR FROM THE STATION in no wind condition.
Tracking directly away FROM the station
- Tune and identify the station.
- Set the VOR so the needle is centered with FROM indication.
- Turn to the heading on the TOP of the OBS.
- Keep the needle centered.
- If the CDI migrates left, you are to the right of track and you have to correct by turning to the left.
- If the CDI migrates right, you are to the left of track and you have to correct by turning to the right.
Intercepting a VOR radial TO (inbound) a Station
- Tune and identify the station.
- Determine the radial you want to track inbound (TO).
- Determine the angle that you want to use to intercept the desired radial.
- Note: Most inbound intercepts are done at 90° because, if you use smaller angle of intercept, it’s possible that you will not intercept your radial before passing the station.
- Turn your OBS so that your desired inbound radial is on the bottom OBS and the reciprocal will be at the top (this will be your heading once you have intercepted) This will give you your heading to intercept.
- If the needle is to the right, ADD your intercept angle to the number on the TOP OBS (this is the heading not the radial because you are going to the station). This will give you your heading to intercept.
- Must have TO indication
- Turn to your intercepting heading.
- As your approach the radial, your CDI needle will start to move toward the centre. When the CDI needle centers, turn to the heading that is on the TOP of your OBS to track inbound to the station.
- REMEMBER: Your top heading should always be the heading you are following.
- If you have a FROM indication, then it will also be the radial.
- If you have a TO indication, it will be the reciprocal of the radial and the radial will be on the bottom.
- EASY NOTE TO REMEMBER:
- When determining radials, if you have a FROM flag, the radial is indicated on the TOP of the OBS. If you have a TO flag, the radial will be indicated on the BOTTOM of the OBS.
- FROM TOP TO BOTTOM.
Intercepting a VOR radial FROM (outbound) a Station
- Tune and identify the station.
- Determine the radial you want to track outbound.
- Determine the angle at which you want intercept your outbound radial.
- (45° or 60° are common outbound intercepts). The smaller the intercept angle the longer it will take you to intercept your desired radial.
- Set the OBS with your desired outbound radial on the TOP.
- Determine the intercepting heading:
- If the needle on your VOR is to the RIGHT, then you need ADD your intercept angle to your desired radial.
- If the needle on your VOR is to the LEFT, then you need SUBTRACT your intercept angle from your desired radial.
- Turn to your intercepting heading.
- As your approach your desired outbound, your CDI needle will begin to centre.
- When the needle is centered, you are on your outbound radial.
- Turn to your outbound radial and fly to keep the needle centered.
Passage over the VOR station
- Full deflection of the needle.
- Sense indicator will change from TO (OFF) to FROM.
- As approach station CDI needle becomes very sensitive.
- Can have large deflections when only slightly off track.
- Hold heading that kept you on track until pass the station.
Review questions
- Where can you obtain the frequency for a VOR station ?
- What flag indication do you want if you are tracking directly away from a VOR station ? And what will the CDI indicate ?
- How do you determine your position in relation to the vor station.
- When you know your position how do you track directly to the VOR station .
- How do you identify VOR passage ?
