VHF+Omnidirectional+Range+-+Operation

ASYS 310 – Aircraft Navigation Systems SAIT Polytechnic  Belinda Gonzales

**VOR – VHF OMNIDIRECTIONAL RANGE **


 * Introduction **

VOR is an accurate short/medium range navigation system that is used. It gives “TO” and “FROM” information in reference to the ground station. This “TO” and “FROM” information tells pilots which radial the aircraft is sitting on in reference to the ground station.


 * Frequencies **

Frequencies used for VOR is in the range of 108 – 117.95MHz. Certain Frequencies between 108 – 112.00, every odd tenth are used for ILS and **cannot** be used for VOR navigation.


 * Inputs **

A valid frequency must be inputted, between 108 – 117.95 MHz expect for frequencies between 108 – 112MHz every odd tenth. If an ILS frequency is inputted, the needle on the RMI will park.



Another input needed for this system to work at its best is a course selection. The pilot enters the course they want to travel on through the OBS knob on the CDI.



Inputs needed to allow the RMI to work is the correct VOR frequency, and one of the needles on the indicator selected on VOR


 * Basic Navigation Principles **

The VOR ground station propagates three signals modulated into the carrier signal, an omnidirectional reference signal, a variable directional signal, and a Morse code or voice identification that provides the name of the station.



When the VOR system in the aircraft sees this rotating signal, it converts the signals and displays which radial the aircraft is sitting on in reference to the station.

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">A receiver picks up the signal and sends the information to a manual and automatic converter, which converts the signals and sends the information to an indicator where the pilot can read it.

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">The manual converter compares the received signals to the selected course that the pilot has chosen and gives the pilot To, From, Left and Right information. The pilot must input a desired course through the OBS knob on the CDI to give any kind of to/from/left/right information. The signals in the manual converter are filtered and phase shifted to allow proper readable information on the CDI.

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">The automatic converter takes the information from the VOR receiver and compass information and sends the signals to the RMI, which to information is only displayed.

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">The information sent to the manual converter gives to and from information, and the information sent to the automatic converter converts the signal into relative bearing information.

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">The Morse code is modulated at 30% into the carrier wave as 1020 Hz that lets the crew know what station they have locked into.


 * <span style="font-family: 'Times New Roman',serif; font-size: 13pt;">Outputs **

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">Audio <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> VOR does have an audio tone, some stations provide only Morse code, or voice identification that alternates with Morse code. <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">CDI <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> When the right information is inputted into the VOR (Frequency and Selected Course), the CDI will display To/From and Left/Right information



<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">RMI <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> When the information is inputted (Frequency and Compass information) the RMI will display TO information only. It will display the heading of the aircraft and To <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> information to the VOR station. <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">


 * <span style="font-family: 'Times New Roman',serif; font-size: 13pt;">Equipment **

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> Ground station <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> VOR systems require a ground station to tell the aircraft where it is. <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> <span style="font-family: 'Times New Roman',serif; font-size: 12pt;"> Aircraft <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">In order for VOR to work on an aircraft, it requires a half-wave dipole antenna horizontally polarised, a control panel, indicators, and a receiver, which is usually combined with other navigation systems.

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">If you are interested in seeing how this system would work, check this [|link] out, you can change where the aircraft is sitting, the heading, and move the OBS around


 * <span style="font-family: 'Times New Roman',serif; font-size: 13pt;">References **

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">[]

<span style="font-family: 'Times New Roman',serif; font-size: 12pt;">Aircraft Communications and Navigation Systems; <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">Mike Tooley and David Wyatt, <span style="font-family: 'Times New Roman',serif; font-size: 12pt;">2007 first edition