The articles below give some helpful information for aviation scanners and were
taken from a thread in rec.radio.scanner.
From: BrianB@faa.roc.servtech.com (Brian Berard)
Newsgroups: rec.radio.scanner
Subject: Re: airport talk...HELP!!
twilson3@ix.netcom.com (Tom Moorehouse ) wrote:
>Ive been listening to airport frequencies for about 5 months now and i listen to San Jose
>airport stuff, the tower frequency for san jose is 124.0000. When the airplanes take off,
>the tower tells them to switch from 124.0000 to bay departure which is 121.3000. Then the guy
>from bay departure says "Bay Departure, Radar contact." Can someone please tell me what "radar
>contact" means???
Hello Tom! I work for the FAA as a Radar Tech amongst a lot more
equipment that we are responsible for maintaining. I'm not familiar
with San Joses Freqs nor do I have them handy, but I can tell ya
basically how Air Traffic is controlled. Thus this will give ya some
insight on what happens at your local tower.
First off, all Air Traffic Control Towers (ATC) are responsible for
for Air Traffic within 55NM (Nautical Miles) of their respective
towers. Lets start with a plane taking off.
The Pilot requests permission after filing a Flight Plan to Taxi to
the runway that Air Traffic is currently using. Ground Control in the
Top of theTower directs and Controlls the Ground Traffic, which
includes ALL vehicles and planes on the ground. Most of the time
depending on the Tower location, they have a clear view of the Ground
Traffic. The Controller then when conditions allow, directs Aircraft
to proceed via the Taxi Ways to the runway in preparation for take
off. The Controllers in The Tower Cab are resposible for that plane
for 10NM after which he Hands Off this aircraft to the Controller that
is located at most facilities in the Base of the Tower. That
Controller now has the responsibility from 10NM to 55NM, after which
he Hands off the aircraft to another Tower along that Pilots Flight
Plan. There's a LOT more that goes on than this but Basically that is
what happens at your Local airport. The opposite is true when the
Aircraft enter a Local Towers Air Space after which the reverse of what
I said above occurs.
Keep in mind that we have other Facilities along the way that pilots
tune into which help them Navigate along Safely according to their
Flight plan. This includes VORS, Comm Equip, etc... A lot of times
these Facilities are located in very remote areas. In fact I use to be
stationed in such an area in Nevada. I use to maintain all equipment
within a 200 mile radius. Now I'm stationed at the Local Airport and
maintain All the Equipment in the Tower and at the Radar/Beacon sight.
Yes, it keeps me very busy! --)) Lot's of responsibility here.
I could go on and on but I'll stop here. If ya have any questions
feel free to post here or via Email!
Hope this gives ya a better understanding of what takes place and why
all the different frequecies are used and what for.
From: Curtis Wheeler (cgwh@chevron.com)
Newsgroups: rec.radio.scanner
Subject: Re: airport talk...HELP!!
"Radar Contact" simply means that the controller has positively
identified you on radar and knows where you are. This way the pilot
knows the controller can "see" him. The radar controller cannot
control traffic he can't see. We you drop off a controller's screen
due to terrain, etc., the controller will use the term "radar contact
lost." This does not mean the plane is crashing - just that it left
the "view" of the radar antenna.
Sometimes you will hear "radar service terminated". This means that
the controller is no longer providing traffic advisory or separation
service for the aircraft. This could be because the controller is
too busy to handle some types of traffic, was unable to "hand off"
the traffic to another controller, or has instructed the pilot to
contact a facility that does not have radar (most towers do not have
radar). You will not normally hear "radar service terminated" with
airline traffic on IFR flight plans. It is common with VFR flights
that are using "flight following" services.
From: dhughes@inetdirect.net (D. Hughes)
Newsgroups: rec.radio.scanner
Subject: Re: airport talk...HELP!!
While Brian gave a very conclusive explaination of take-off/landing
procedures, I don't think he explained the term "radar contact", so I'll
try.
The airport radar is a two part antenna system, the radar antenna and an
interrogator. The radar tells the guy in the tower "there's a plane there",
but it doesn't say which plane it is. The interrogator sends a signal, which
the plane receives and responds to with an IFF (Identify Friend or Foe in the
military, I forget the civilian name) code, which identifies the plane. This
code is displayed next to the radar blip on the tower (or bay departure, or
the regional center, or where ever) screen, and this is how the controllers
know which plane is which.
So the controller sees a blip, a code next to it, and he tells the pilot
"radar contact". It's just a fast way to say that he has the pilot's plane on
the radar screen.
From: Curtis Wheeler (cgwh@chevron.com)
Newsgroups: rec.radio.scanner
Subject: Re: airport talk...HELP!!
dhughes@inetdirect.net (D. Hughes) wrote:
>The airport radar is a two part antenna system, the radar antenna and an interrogator. The
>radar tells the guy in the tower "there's a plane there", but it doesn't say which plane it is.
>The interrogator sends a signal, which the plane receives and responds to with an IFF (Identify Friend
>or Foe in the military, I forget the civilian name) code, which identifies the plane. This
>code is displayed next to the radar blip on the tower (or bay departure, or the regional center,
>or where ever) screen, and this is how the controllers know which plane is which.
The "civilian" term you are thinking of is Mode-C. Or more
generically called a transponder "squawk". At least that is
what is currently used. When secondary survailance radar interogates
an aircraft transponder, it replies or "squawks" with a 4 digit octal
code assigned to the aircraft for that flight (the pilot dials in
code given to him by the controller or before the flight when
receiving a clearance). Mode C replies also contain the plane's
pressure altitude from an on board altitude encoder.
ATC computers use the four digit code to determine and disply the
aircraft call sign and altitude (corrected for local altimeter
setting). The computers can also display the ground speed of the
aircraft by traking the target and doing the time and distance
calculations - the transponder does not send speed info to the
computer.
When you hear news stories about FAA ATC computers going down, it
usually means they can't use the transponder replies for information
and have to deal with raw radar, if they have it. An ATC specialist
could address that better - it's been a while since I have toured a
center and asked any questions.
From: BBBV94A@prodigy.com (Bill Rogers)
Newsgroups: rec.radio.scanner
Subject: Re: airport talk...HELP!!
After the plane has taken off and the tower controller has handed the
plane off to the departure controller (the pilot is told to contact
departure on a different frequency), usually the first thing the
departure controller will say is "Radar contact." This just means that
the controller sees the plane on his radar scope and knows which one it
is, of the dozens of planes he sees.
Your library probably has some books that will walk you through the
procedures.
And for folks looking for local aircraft frequencies, just go to some
small airport in the area and at the FBO ("fixed base operator" -- - the
airport manager) office buy a "sectional" chart --- an aviation map of
the area that will have most of the frequencies.
From: Matt Wilson (wa2tpx@acy.digex.net)
Newsgroups: rec.radio.scanner
Subject: Re: airport talk...HELP!!
BBBV94A@prodigy.com (Bill Rogers) wrote:
>And for folks looking for local aircraft frequencies, just go to some small airport in the area
>and at the FBO ("fixed base operator" -- the airport manager) office buy a "sectional" chart,
>an aviation map of the area that will have most of the frequencies.
Better yet:
Go to the same FBO (any place that gives flying lessons will do) and
ask for the "Aiport/Facilities Directory" for your region. It will
give much more information than the sectional charts and also cover
a much much larger geographic "listening" area. The publication
is updated every 90 days and floats around 350 pages at a giveaway
price!
