Navigation by VOR and DME

This lesson covers the basics of VOR navigation - almost everything you need to know can be found here:  VOR Navigation Overview

and in the additional information provided below.  You may also find the Elite Premair video series on VOR navigation helpful - you can view each of the videos in the series here: Video Series - VOR Navigation

The written and practical tests may include other areas where you are expected to be able to demonstrate knowledge and proficiency but in general the minimum requirements include (but may not be limited to):

  • Understand how to identify VOR navigational aids and how they can be used in flight planning

  • Understanding how to read and interpret what the VOR indicator is telling you -

    • How to identify that the VOR is receiving a signal and how to verify that signal is from the desired VOR station

    • The scale of the VOR needle swing and how the accuracy compares to use of an RMI indicator -

      • 10 degrees for full right or left deviation, usually designated by five 'dots' or short lines, two degrees each (note that for a localizer the full swing in only 2 1/2 degrees)

      • RMI indicators typically are small enough that you can only maintain a tolerance of one or two degrees.  With an omnihead or omni bearing indicator (the type of instrument in the Cessna 172 standard cockpit) or HSI display accuracy is usually 1/2 degree or less

    • The function of the TO / FROM indicator

    • How to deal with the "cone of confusion"

    • How to correct your course to maintain flight along the desired VOR radial

      • When the VOR indicator shows the needle is centered, the TO/FROM indicator shows 'TO' and your aircraft's heading is approximately the same as the VOR indicator card heading then you are flying TO the VOR and deviation from course is corrected by "flying into the needle" - turning in the direction of deviation of the needle in the case of a omnihead or course deviation indicator (the 'split portion of the needle on an HSI)

      • Likewise when the VOR indicator shows the needle is centered, the TO/FROM indicator shows 'FROM' and your aircraft's heading is approximately the same as the VOR indicator card heading then you are flying FROM the VOR and deviation from course is also corrected by "flying into the needle" - turning in the direction of deviation of the needle or course deviation inicator (the 'split portion of the needle on an HSI)

      • If you are using an omnihead (omni bearing indicator, like that in the Cessna 172 standard cockpit) flying in the opposite direction of the TO / FROM indicator (the TO / FROM indicator is pointing in a direction opposite of flight - the omnibearing indicator card is set to a heading that is somewhere in the 180 degree half circle that is opposite of  the 180 degree half circle that your heading indicator is in) then you are in a situation that has been termed 'reverse sensing'.  Here, instead of flying into the needle to correct your course you turn away from the direction the needle has deviated to - but this interesting discussion shows that there really isn't any such thing as reverse sensing - the principle is that you always turn towards the heading that appears on the compass rose that is on the side which the needle has deflected to --  Reverse Sensing - No Such Thing   Note that this is not the case with an HSI, since the entire display rotates as the aircraft turns so from your perspective you are still 'flying into the needle'-or in this case, into the course deviation indicator. (Thanks Al !!)

      • See the comments and illustration at the bottom of the page for the principles of establishing and maintaining yourself on a VOR radial if using a radio magnetic indicator (RMI)

  • Understand the proper procedures for flying TO a VOR -

    • Tune your NAV radio to the correct frequency

    • Once the VOR indicator becomes ‘live’ verify the correct frequency (Morse code signal from the VOR)

    • Turn in the general heading of the VOR

    • Rotate the course indicator needle until the course deviation bar aligns with the head and tail of the needle or course indicator card until the needle centers

    • Turn to the heading indicated by the needle or course card

    • Hold that heading. Fly ‘towards the needle’ if the course indicator moves to one side or the other of center
       

  • Understand the proper procedures for flying FROM a VOR -

    • Tune your NAV radio to the correct frequency

    • Rotate the OBS to the FROM radial

    • Once the VOR indicator becomes ‘live’ verify the correct frequency (Morse code signal from the VOR)

    • Turn towards the radial to intercept it. (See the discussion in the VOR Navigation Overview document about distance from the VOR and how this affects the rate of change of each radial degree – the Why Distance Matters section)

    • Hold that heading. Fly ‘towards the needle’ if the course indicator moves to one side or the other of center
       

  • Understand the principles of DME when used in combination with a VOR

    • How to identify your position using the VOR signal and DME distance

    • How the DME distance displayed is affected by the altitude above a VOR when very close to or overflying a VOR station - it is the actual distance from the DME transmitter that is measured (the 'slant distance' or, if you are directly above the DME transmitter, the vertical distance), NOT the lateral (horizontal) component of distance along your coures.  Bottom line - the minimum DME distance that will display is equal to your distance above ground level when you are directly over the DME transmitter - as shown here:

  • Understanding how to use two VORs to identify your position by triangulation
     

  • Understand the basic use of the 'Rule of 60' and how it is used to estimate distance and time when flying across the radials of a VOR (and, you can use it the same way if the navaid is an NDB).  If you don't know - ask an instructor!

 

VOR navigation using a radio magnetic indicator (RMI):

 

This is something that you will see in the lesson on navigation by ADF - the ADF indicator behaves like an RMI (and for all intents and purposes in most cases is just that).  In contrast, a VOR can be flown using an RMI if the aircraft is so equipped (and if so, usually NAV2 is connected to the RMI) or with the standard omni head or HSI indicator. 

 

Three key differences in navigating by VOR using an RMI vs. a standard omni head or HSI are:

  1. The RMI needle always points toward the VOR station (there is no 'TO' or 'FROM' indicator).  So - since VOR radials are defined by the direction from the VOR station then if you are flying TO a VOR station the HSI needle points in the opposite direction of the (defined) radial.

  2. There is no way to 'dial in' the desired radial.  Again, the RMI needle always points toward the VOR station

  3. Moving to the desired VOR radial requires an understanding of the principle of "pull the tail" - or as some think of it: "Push the head; Pull the tail".  However, if you are flying to the VOR station you simply turn to the heading the RMI needle is pointing to and maintain that radial (not the heading - the radial, so to a limited degree the "pull the tail" technique still applies)

The following describes the technique for establishing and maintaining yourself on a desired VOR radial using an RMI.  The principles of using an RMI for VOR navigation are:

  • The head of the RMI needle always points TO the VOR station - so the RADIAL is defined by the direction the TAIL of the needle is pointing.

  • If your aircraft has a heading similar to the HEAD of the needle you are flying TO the VOR

  • If your aircraft has a heading similar to the TAIL of the needle you are flying FROM the VOR

  • To move to the desired VOR radial (or to correct your current position to re-establish yourself on the desired radial) -- "Pull the tail" of the needle.  Imagine that your aircraft is located on the tail of the needle like the red aircraft shown below.  If you want to move to the 160 radial (and fly TO the VOR heading 340 degrees) you would "pull the tail" to the right (pull the tail to the desired radial) which will move the head to the left.