VHF Omni-Directional Range (VOR)

Question 1

What is a VOT?

Answer 1

• A test facility that transmits a test signal which provides users a convenient means to determine the operational status and accuracy of a VOR

Question 2

How do you use the VOT service?

Answer 2

1. Tune in the VOT frequency on your VOR receiver
2. With the CDI centered, the omni-`bearing selector should read 0 degrees with the to/from indication showing “FROM”
   or
   the omni-bearing selector should read 180° with the to/from indication showing “TO” plus or minus 4°

Question 3

What is a DME, and how does it work?

Answer 3

• DME an equipment on an aircraft that measures your distance from a VOR

Question 4

What distance does a DME measure?

Answer 4

The slant range to the VOR

Question 5

How else can an aircraft measure distance without DME equipment, and how is distance measured?

Answer 5

GPS can also measure distance in place of a DME and it’s measured in ground distance, not slant range

Question 6

What’s the 60-1 rule in regards to scale deflection based on distance from the VOR?

Answer 6

• At 60 NM from a station there’s a 1 NM between each radial
• At 30 NM from a station there are 2 RADIALS per NM

Question 7

How does a VOR work?

Answer 7

• Ground station sends out 2 signals. 1 stationary signal that is omnidirectional and 1 rotating signal that sweeps 360° every 30 sec
• Signals are timed so that the sweeping signal is always 90° out of phase with the master signal
• By comparing the sweeping signal with the master, the angle (bearing) to the aircraft from the station can be determined
• The line of position is called the “radial” from the VOR

Question 8

What are the different classes of VORs?

Answer 8

• Terminal
• Low
• High

Question 9

Can I use a VOT test facility while on the ground?

Answer 9

• It is permitted, but use is strictly limited to those areas/altitudes specifically authorized in the Chart Supplement U.S. or appropriate supplement

Question 10

What’s the range of a terminal VOR?

Answer 10

• From 1,000’ above the transmitter height (ATH) up to and including 12,000’ ATH
• 25 NM

Question 11

What is a “L” (low altitude) VOR/DME standard service volume?

Answer 11

• 1,000’ ATH to 18,000’ ATH
• 40 NM

Question 12

What is a “H” (high altitude) VOR/DME service volume?

Answer 12

• 1,000’ ATH to 14,500’ @ 40 NM
• 14,500’ ATH TO 60,000’ ATH @100 NM
• 18,000’ ATH to 45,000’ ATH @130 NM
• 45,000’ ATH to 60,000’ ATH @ 100 NM

Question 13

How does the receiver in the airplane know what radial it’s on?

Answer 13

1. There’s a omnidirectional pulsating signal and a rotating signal sent out by the VOR
2. Both signals are sent out when the rotating signal reaches the 360 radial and the receiver picks up the omnidirectional signal.
3. The receiver measures the time it takes the rotating signal to be received, as the rotating signal is rotating on a 360° rotation, that’s how it knows what radial it’s on.

Question 14

How many degrees of deflection is indicated if the CDI on the VOR is fully deflected?

Answer 14

It indicated a deflection of 10° or more

Question 15

How many degrees of deflection is each dot of the VOR as it moves in from outside to the center?

Answer 15

• It’s 10° or more when it’s fully deflected, and reduces by 2° for each dot as it gets closer to the center (i.e. 10°, 8° ,6°, 4°, 2°)

Question 16

How do you perform a VOT check?

Answer 16

1. Tune the VOR to the VOT signal
2. Set the course either to 0° with the TO/FROM indicator showing a FROM indication; or 182° with the TO/FROM indicator showing a TO indication
3. The bearing error must be within +/- 4°

Question 17

How to conduct a dual VOR check?

Answer 17

1. Tune both NAV radios to the same VOR facility
2. Center the needles of each VOR receiver with a TO indication
3. Note the indicated bearing TO the station from each receiver
4. The max bearing error is 4°

Question 18

How to conduct an Airborne VOR check?

Answer 18

1. Select a VOR radial that lies along the centerline of an established VOR airway
2. Select a ground point along the selected radial preferably more than 20 NM from the VOR ground station, and maneuver the a/c directly over the point at a reasonably low altitude
3. Note the VOR bearing indicated by the receiver when over the ground point
4. The max indicated error is +/- 6°

Question 19

How are VOR ground checks performed?

Answer 19

1. Find the location of the ground VOR check on chart supplements. This will tell you if the airport you’re at has a ground checkpoint station
2. Park inside the circle of the VOR ground check point
3. Instructions on the sign will give you VOR frequency, radial you should tune, and if it should be a TO/FROM indication. Follow the instructions at the VOR ground check

Must be within +/- 4°