Dave Siciliano
Final Approach
More perspective from a long time pilot.
Dave
===================================================
Good Evening Pete,
This is just from my recollection, so if somebody else has better information I would be happy to hear it.
The term Victor Airway was first applied to the airways designated by VARs.
The V standing for VHF radio.
VAR stood for Visual Aural Range. The four courses were generally designated by the blue and yellow hemispherical sectors and the A and N sectors. You would look at a CDI to determine if you were in a yellow or blue area and listen to the aural signal to determine if you were in an A or N signal. The CDI indication used a tone indication the same as does the ILS localizer system.
In fact, the tone frequency used was the same as the tones used for a localizer which is why we have yellow and blue segments on localizer indicators.
During the same time as the VARs were being used to replace the Low Frequency Range stations, some brainy guy figured out how to make a signal that was transmitted such that the phase difference between two signals varied depending on the receivers location and direction from the transmitter.
I do not recall the precise angle from North at which the signals were, or are, in phase, but it is somewhere around two hundred and forty degrees from North. Anywhere else around the station, the out of phase relationship can be measured by beating a known correction signal against the transmitted signal
to determine how far one is form the point where the signals are in phase.
We read such information as a radial to or from the transmitter.
That piece of equipment used the same radio frequency spectrum as did the VARs and most VARs were converted to VORs or VHF Omnidirectional Radio stations.
The first VARs were established in mountainous regions as those were the places where the Low Frequency ranges encountered the greatest difficulties.
Most were in service for no more than ten years.
My recollection is that Victor Airways and the Low Frequency colored airways existed side by side for several years during the changeover.
As an aside, there was an argument for couple of years as to whether or not all localizers should be switched over to use phase differentiation rather than tone. If they had done that, it would have made it cheaper to build ILS receivers in conjunction with VOR receivers.
Unfortunately, it was decided that there was too great a cost involved in the changeover, so the tone signal system was retained.
=================================================
And a follow up thread.
Dave
Interesting, Bob. One learns something new every day. Here's more info, including a couple of approach plates:
http://www.airwaysmuseum.com/VAR%20&%20Markers%20Ops%20Notes%201953.htm
Dave
===================================================
Good Evening Pete,
This is just from my recollection, so if somebody else has better information I would be happy to hear it.
The term Victor Airway was first applied to the airways designated by VARs.
The V standing for VHF radio.
VAR stood for Visual Aural Range. The four courses were generally designated by the blue and yellow hemispherical sectors and the A and N sectors. You would look at a CDI to determine if you were in a yellow or blue area and listen to the aural signal to determine if you were in an A or N signal. The CDI indication used a tone indication the same as does the ILS localizer system.
In fact, the tone frequency used was the same as the tones used for a localizer which is why we have yellow and blue segments on localizer indicators.
During the same time as the VARs were being used to replace the Low Frequency Range stations, some brainy guy figured out how to make a signal that was transmitted such that the phase difference between two signals varied depending on the receivers location and direction from the transmitter.
I do not recall the precise angle from North at which the signals were, or are, in phase, but it is somewhere around two hundred and forty degrees from North. Anywhere else around the station, the out of phase relationship can be measured by beating a known correction signal against the transmitted signal
to determine how far one is form the point where the signals are in phase.
We read such information as a radial to or from the transmitter.
That piece of equipment used the same radio frequency spectrum as did the VARs and most VARs were converted to VORs or VHF Omnidirectional Radio stations.
The first VARs were established in mountainous regions as those were the places where the Low Frequency ranges encountered the greatest difficulties.
Most were in service for no more than ten years.
My recollection is that Victor Airways and the Low Frequency colored airways existed side by side for several years during the changeover.
As an aside, there was an argument for couple of years as to whether or not all localizers should be switched over to use phase differentiation rather than tone. If they had done that, it would have made it cheaper to build ILS receivers in conjunction with VOR receivers.
Unfortunately, it was decided that there was too great a cost involved in the changeover, so the tone signal system was retained.
=================================================
And a follow up thread.
Dave
Interesting, Bob. One learns something new every day. Here's more info, including a couple of approach plates:
http://www.airwaysmuseum.com/VAR%20&%20Markers%20Ops%20Notes%201953.htm
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