Basic question: Why and when does ATC assign squawk codes to A/C?

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jeff0000

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jeff0000
I'm pretty fresh to learning about the nuances of ATC and want to know why ATC assigns squawk codes in the first place.

I've seen pictures of an ATC's radar scope, and it includes the ICAO airline designator and the flight number. Without a squawk code, would that information still be there? If assigning a squawk code links a target on the radar scope to that info, that would make sense.

Also, I've listened in on my scanner to my local airport in class delta airspace - Phoenix-Mesa Gateway airport (KIWA). When VFR aircraft call the tower, I'm pretty sure there have been cases where the tower doesn't assign a squawk code at all and just tells the pilot to report a 3 mile left base for runway 30L.

What's the point of assigning squawk codes to aircraft? KIWA is within the Phoenix class bravo within the Mode-C veil, so they have to squawk anyways whether they are above, within, or below the bravo shelves. And I'm guessing that the Phoenix TRACON has both primary and secondary radar, so ATC can obviously see the VFR target and provide traffic advisories.
 
In layman’s terms, a squawk code is just a 4 digit code that helps to identify an aircraft with the radar blip that the controller is looking at on the scope.
jeff0000 said:
When VFR aircraft call the tower, I'm pretty sure there have been cases where the tower doesn't assign a squawk code at all and just tells the pilot to report a 3 mile left base for runway 30L.
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Some Class Delta airports don’t have radar, so assigning them a code wouldn’t have any advantage to the controller at that facility, if that’s the only airspace that the particular aircraft would be operating in.
 
Ryanb said:
In layman’s terms, a squawk code is just a 4 digit code that helps to identify an aircraft with the radar blip that the controller is looking at on the scope.

Some Class Delta airports don’t have radar, so assigning them a code wouldn’t have any advantage to the controller at that facility, if that’s the only airspace that the particular aircraft would be operating in.
Click to expand...

Would you say that most class delta airports don't have radar? I've heard cases where they have radar, but the radar system doesn't meet minimum standards to officially use it (ATC can't say the words "radar contact"), but it can be used to help controllers sequence aircraft.

If a class delta airport doesn't have radar and IMC conditions prevail, how are aircraft sequenced for landing by the tower if the controller cannot see the runway?

For instrument approaches with the words "RADAR REQUIRED", does that mean that the tower needs to have their own radar system, or can the tower use the presiding TRACON's radar?
 
Oh boy....

A Delta tower is only required to provide separation on a runway. That might be something to keep in mind. Approach or Center provides separation for instrument approaches. Tower may help with separating VFR traffic.
 
Oh... yeah. Haha. Kind of forgot about that.

What about when aircraft are flying an instrument approach and they need assistance from ATC to identify that they're passing a certain fix (on many non-precision approaches)? I would assume they would be in contact with tower because they would be past the final approach fix - but how can that be if tower does not have radar?

Sorry, more answers just seems to give me more questions :)
 
jeff0000 said:
Oh... yeah. Haha. Kind of forgot about that.

What about when aircraft are flying an instrument approach and they need assistance from ATC to identify that they're passing a certain fix (on many non-precision approaches)? I would assume they would be in contact with tower because they would be past the final approach fix - but how can that be if tower does not have radar?

Sorry, more answers just seems to give me more questions :)
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IFR aircraft identify fixes on their own. It may just be timing but it is what it is. No external help is required.
 
Shouldn’t the pilot be able to identify when passing fixes? Otherwise I’m not sure there’s much usefulness to an instrument approach.

Edit: Clark beat me to it.
 
I have seen approaches (some years back) where the only way a fix could be identified is by ATC radar. It even had a notation “radar fix”.

I’ll let one of our ATC guys answer your questions, as they would be the best source.
 
jeff0000 said:
Here's an example of an approach: the VOR / TACAN RWY 14 approach at Fort Wayne. It says DME or radar required, and I see "RADAR" under the KABDE and WAINE intersections.
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Radar is required to get you established on the approach because there isn’t a non radar feeder going into it. Once you’re established, then you can use DME or ATC can provide you exact position via the fixes on their video maps. This can be done with a Certified Tower Radar Display. With FWA being a Class C where the local controller could also be qualified on approach, you can bet that they have a CTRD and use it for all radar functions.

Back to the original question, as Ryan said above, assigning a code is a basic means of radar identification. The software will automatically put a tag to that code if a flight plan is entered into the NAS computer. That tag obviously provides a quick ID of the aircraft but also allows for automated handoffs or, transfer of radar ID. The code itself is also used to transfer radar ID to another controller when a handoff isn’t necessary.
 
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jeff0000 said:
Would you say that most class delta airports don't have radar? I've heard cases where they have radar, but the radar system doesn't meet minimum standards to officially use it (ATC can't say the words "radar contact"), but it can be used to help controllers sequence aircraft.

If a class delta airport doesn't have radar and IMC conditions prevail, how are aircraft sequenced for landing by the tower if the controller cannot see the runway?

For instrument approaches with the words "RADAR REQUIRED", does that mean that the tower needs to have their own radar system, or can the tower use the presiding TRACON's radar?
Click to expand...

Most Class D airports do not have radar. Radar required does not mean the tower has radar.
 
jeff0000 said:
I'm pretty fresh to learning about the nuances of ATC and want to know why ATC assigns squawk codes in the first place.

I've seen pictures of an ATC's radar scope, and it includes the ICAO airline designator and the flight number. Without a squawk code, would that information still be there? If assigning a squawk code links a target on the radar scope to that info, that would make sense.

Also, I've listened in on my scanner to my local airport in class delta airspace - Phoenix-Mesa Gateway airport (KIWA). When VFR aircraft call the tower, I'm pretty sure there have been cases where the tower doesn't assign a squawk code at all and just tells the pilot to report a 3 mile left base for runway 30L.

What's the point of assigning squawk codes to aircraft? KIWA is within the Phoenix class bravo within the Mode-C veil, so they have to squawk anyways whether they are above, within, or below the bravo shelves. And I'm guessing that the Phoenix TRACON has both primary and secondary radar, so ATC can obviously see the VFR target and provide traffic advisories.
Click to expand...
Codes are assigned to identify a target. Before Secondary Radar it was done by identifying turns. Controllers would tell a pilot to turn 30 degrees or more. The target that made that turn could then be identified as that airplane. Next came Secondary Radar, transponders. Controller would say Ident and the target that idented was that plane. Next came SIF, Selective Identification Feature. There were 64 different codes, all the two digit combinations using the digits 0-7. Now the controller could tell the difference between all the planes squawking a particular code and all the other targets on the scope. Next came 4096 Secondary Radar, all the 4 digit combinations of the digits 0-7. Now each airplane has it's own unique code and individually looks different from all the other targets on the scope. Next the computer enters the picture and the controller can tell it that the plane squawking 0423 is N12345 and the computer puts N12345 on the scope.

Most Towers have Radar. How they use it varies. Some are no more than a picture of a Radar scope. There is a scope at the Approach Control or Center that has a camera looking at it and that is sent to the Tower that has a TV to see it. Some Towers have their own Radar scope and it doesn't have to be sent to them via Closed Circuit TV. What the Towers use the Radar info for varies widely. For some it's merely an 'extension' of their eyeballs. They don't say 'Radar Contact' and they don't give Radar 'service.' It goes up there in different degrees of Radar services provided all the way to IFR Radar services, including 'separation' which is delegated to them from the parent Approach Control or Center.
 
jeff0000 said:
Oh... yeah. Haha. Kind of forgot about that.

What about when aircraft are flying an instrument approach and they need assistance from ATC to identify that they're passing a certain fix (on many non-precision approaches)? I would assume they would be in contact with tower because they would be past the final approach fix - but how can that be if tower does not have radar?

Sorry, more answers just seems to give me more questions :)
Click to expand...

Here's the controllers procedure on that.

4. When radar is used to establish the final
approach fix, inform the pilot that after being advised
that he/she is over the fix he/she is to contact the tower
on local control frequency.
EXAMPLE−
“Three miles from final approach fix. Turn left heading
zero one zero. Maintain two thousand until established on
the localizer. Cleared I−L−S runway three six approach. I
will advise when over the fix.”
“Over final approach fix. Contact tower one one eight
point one.”
NOTE−
ARSR may be used for establishment of initial approach
and intermediate approach fixes only. ASR must be used to
establish the final approach fix.
 
luvflyin said:
Codes are assigned to identify a target. Before Secondary Radar it was done by identifying turns. Controllers would tell a pilot to turn 30 degrees or more. The target that made that turn could then be identified as that airplane. Next came Secondary Radar, transponders. Controller would say Ident and the target that idented was that plane. Next came SIF, Selective Identification Feature. There were 64 different codes, all the two digit combinations using the digits 0-7. Now the controller could tell the difference between all the planes squawking a particular code and all the other targets on the scope. Next came 4096 Secondary Radar, all the 4 digit combinations of the digits 0-7. Now each airplane has it's own unique code and individually looks different from all the other targets on the scope. Next the computer enters the picture and the controller can tell it that the plane squawking 0423 is N12345 and the computer puts N12345 on the scope.

Most Towers have Radar. How they use it varies. Some are no more than a picture of a Radar scope. There is a scope at the Approach Control or Center that has a camera looking at it and that is sent to the Tower that has a TV to see it. Some Towers have their own Radar scope and it doesn't have to be sent to them via Closed Circuit TV. What the Towers use the Radar info for varies widely. For some it's merely an 'extension' of their eyeballs. They don't say 'Radar Contact' and they don't give Radar 'service.' It goes up there in different degrees of Radar services provided all the way to IFR Radar services, including 'separation' which is delegated to them from the parent Approach Control or Center.
Click to expand...


591A5EC7-A1F4-46BB-A84B-01D28DBCE523.jpeg
Not that many agencies look at it anymore but military still uses the 2 digit 64 combo for mode 1.
 
Clip4 said:
Most Class D airports do not have radar. Radar required does not mean the tower has radar.
Click to expand...

Yeah, ‘Radar Required’ and Radar ‘fixes’ on an Approach have nothing whatsoever to do with whether a Tower has Radar or not. I’d bet a big majority of Towers have Radar nowadays. How many of those Radars are certified for, and the controllers certified to perform IFR control functions such as ‘calling Final Approach fixes’ is another story.
 
luvflyin said:
yeah. But they may be charging for them someday. $3.95 per squawk will be added to your account plus $.50 per “say again squawk.”
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Cause everyone knows GA pilots flying $60,000 airplanes and wearing $500 headsets can’t afford the additional cost of a Starbucks coffee.
 
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