Can ATC see you under their airspace?

RyanB

RyanB

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The airport I fly to/from is a satellite airport in an outlying class C. On the sectional the airport is just outside the airspace. When i takeoff from it and transition through the C, i will usually call up approach when im around 200-300 ft below the C. For example in the shelf where this airport is the floor of the C starts at 2300' however ill call up approach around 2000' make 2 way they give a beacon code and will usually identify me or have me ident. So the thing i am wondering is if they can see me on the screen below the C or do i have to be at the 2300' feet before they can say "n123 radar contact..." ?
 
Absolutely they can see you under the shelf. You don't need to be inside their defined airspace for them to see you.
 
They're watching you. That can be a good thing.
 
Ryanb said:
The airport I fly to/from is a satellite airport in an outlying class C. On the sectional the airport is just outside the airspace. When i takeoff from it and transition through the C, i will usually call up approach when im around 200-300 ft below the C. For example in the shelf where this airport is the floor of the C starts at 2300' however ill call up approach around 2000' make 2 way they give a beacon code and will usually identify me or have me ident. So the thing i am wondering is if they can see me on the screen below the C or do i have to be at the 2300' feet before they can say "n123 radar contact..." ?
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They can see you outside the Class C airspace.
 
ATC will often filter out 1200 squawk codes to declutter their screens.
 
I wonder how low ATC's radar can pick up traffic. Seems like I hear "radar contact lost" anywhere from 500-3000 depending on airport.

When my transponder went out ATC couldn't even see me as a primary target climbing through 9,000 in their TRSA.
 
Ryanb said:
The airport I fly to/from is a satellite airport in an outlying class C. On the sectional the airport is just outside the airspace. When i takeoff from it and transition through the C, i will usually call up approach when im around 200-300 ft below the C. For example in the shelf where this airport is the floor of the C starts at 2300' however ill call up approach around 2000' make 2 way they give a beacon code and will usually identify me or have me ident. So the thing i am wondering is if they can see me on the screen below the C or do i have to be at the 2300' feet before they can say "n123 radar contact..." ?
Click to expand...

Yep, like the other said that avian see you.

At our local C, the screens are setup to display 1200 codes as just the primary returns. So when I take off from let's say North Little Rock and call up DEP, they will give me a code and tell me to ident. They see you, but like Captain said, there screens might have you filtered completely out or as just a primary. They ask for ident when they need a double check on which aircraft their looking at or to find you if your on the outskirts of the sector.
 
FORANE said:
I wonder how low ATC's radar can pick up traffic. Seems like I hear "radar contact lost" anywhere from 500-3000 depending on airport.

When my transponder went out ATC couldn't even see me as a primary target climbing through 10,000 in their TRSA.
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I know in LIT, if they turn off the declutter filter, they can see the traffic on the nearby freeways. Also their radar picks up our schools aircraft in the training fields. Which is about 70 miles away behind a hill. So either the radar is high enough to see over the hill or their piping in a remote radar feed.
 
Captain said:
ATC will often filter out 1200 squawk codes to declutter their screens.
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That is news to me!

ATC controls IFR well outside the class b or c and they need to provide traffic advisories to all aircraft "work load permitting". We did filter out 1200 if the only airspace we were controlling was FL180 and above.
 
semi-related: My local tower told me they can see composite planes like my DA20 as primary targets (xponder off). I have trouble believing that. Can anyone here confirm or deny?

I understand that DA40s have imbedded wire mesh for lightning protection, but not DA20s ..... (?).
 
I can't confirm or deny it, but it is at least plausible, considering the engine, wires, and other metal (such as fuel tanks?) in the plane.
 
N5922S said:
semi-related: My local tower told me they can see composite planes like my DA20 as primary targets (xponder off). I have trouble believing that. Can anyone here confirm or deny?

I understand that DA40s have imbedded wire mesh for lightning protection, but not DA20s ..... (?).
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Sure they can. Worked many composite homebuilts on approach and never had a problem getting a primary. Obviously metal improves the return but composites are easily seen. If the radar can pick up precip and birds, it can pick up a composite.
 
N5922S said:
semi-related: My local tower told me they can see composite planes like my DA20 as primary targets (xponder off). I have trouble believing that. Can anyone here confirm or deny?

I understand that DA40s have imbedded wire mesh for lightning protection, but not DA20s ..... (?).
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My post above was referring to my Lancair 235/320 which is composite without wire mesh. When my transponder failed - while under IFR - I was advised by departure they could not even see me as a primary target and subsequently center advised they could not see me (level at 9000 I think) for around 40 miles before they intermittently saw me as a primary target.
 
Sometimes the shelf floor is there because of high terrain and therefore there is no radar coverage.

At my home field the controlling entity is Oakland Center but they can't see you or talk to you until you climb to 13,000'


Sometimes ATC cannot see you under their airspace.
 
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Whether they can see a composite aircraft as a primary return really depends on the type of radar, distance, the details of the aircraft design - the engine is a big block of metal, and the pilot is a big blob of water, both of which will reflect the radar signal to some extent. Even things like the lengths of the wiring of the electrical system can cause the radar cross-section to vary substantially, as can the attitude or heading.

The transponder on my VariEze was out of service for a while, and during that period there were definitely times when I could be seen, and provided service, and other times when I could not.
 
A few other factors to a composite aircraft generating a primary return is the aspect angle between the aircraft and the radar receiver as well as the Doppler return off of your prop.
 
FORANE said:
I wonder how low ATC's radar can pick up traffic. Seems like I hear "radar contact lost" anywhere from 500-3000 depending on airport.
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Radar is line of sight, so the lower edge of coverage depends on the height of the radar and the distance you are from it. For low radar and low target the range is in the neighborhood of 40 miles. Out in the weeds with the aircraft far from the radar they may not be able to pick you up below 7000'

TRACON radar depiction is, I believe, always the results from a single site. Center radar is a composite of many sites so the altitude floor is more complex.

Large buildings or other obstructions between a radar and you may also create pie-shaped holes in that particular radar's coverage.

In my experience the controllers know very accurately what the lower edge of their coverage is at a particular location. Just ask.
 
N5922S said:
semi-related: My local tower told me they can see composite planes like my DA20 as primary targets (xponder off). I have trouble believing that. Can anyone here confirm or deny?

I understand that DA40s have imbedded wire mesh for lightning protection, but not DA20s ..... (?).
Click to expand...

That engine is a big hunk of metal. Our local TRACON can see our fiberglass gliders. There is metal in the framework, Control linkages, etc.

That spinning prop is a great radar reflector if you are angled toward the radar site.
 
pericynthion said:
SNIP... and the pilot is a big blob of water, both of which will reflect the radar signal to some extent. Even things like the lengths of the wiring of the electrical system can cause the radar cross-section to vary substantially. ... SNIP.
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I provided "traffic, southbound primary return only, slow moving" the pilot reported back that the only thing he could see was a flock of geese headed south along the river. Sure enough, we were tracking a flock by the water in their bellies.
 
Picked up a weather balloon once while giving a PAR to a T-38. Never called traffic on it either because we thought it was birds. IP later said they had a close call and reported it as a UFO. When in doubt, call the traffic.

I guess with the newer stuff you can actually tag up a primary as well. Heard the other day from a friend that when he's bored he'll tag a primary and label it birds or something. Didn't have that capability with the old TPX-42 Arts. A primary was a primary.
 
parrots are the easiest kind of bird to see on radar, because they're squawking
 
airdale said:
Radar is line of sight, so the lower edge of coverage depends on the height of the radar and the distance you are from it. For low radar and low target the range is in the neighborhood of 40 miles. Out in the weeds with the aircraft far from the radar they may not be able to pick you up below 7000'

TRACON radar depiction is, I believe, always the results from a single site. Center radar is a composite of many sites so the altitude floor is more complex.

Large buildings or other obstructions between a radar and you may also create pie-shaped holes in that particular radar's coverage.

In my experience the controllers know very accurately what the lower edge of their coverage is at a particular location. Just ask.
Click to expand...

Some of the bigger TRACON facilities are becoming equipped with the ability to use multiple radar antennas simultaneously. As a result, we get faster updates (where I work, we get 1 per second) and better low-altitude coverage. No more losing targets flying over the top of an antenna anymore, either.
 
Off hand, the only space Approach could have problems viewing is the Cumulo Granite of the Supersititions under the Phoenix Class B (4 Peaks/Grine area)
:)
 
oldShar said:
Off hand, the only space Approach could have problems viewing is the Cumulo Granite of the Supersititions under the Phoenix Class B (4 Peaks/Grine area)
:)
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:(...
 
FORANE said:
I wonder how low ATC's radar can pick up traffic. Seems like I hear "radar contact lost" anywhere from 500-3000 depending on airport.

When my transponder went out ATC couldn't even see me as a primary target climbing through 9,000 in their TRSA.
Click to expand...
Depends on where you're at, your altitude, how far away from the radar site and the intervening terrain. There're places in central Montana where ATCs radar won't see you below 15,000 feet.
 
I fly a small EAB with no transponder for its a single seat. I am located right outside class c airspace.

Some pilots flew in and told me that ATC saw me. They reported to these pilots possible traffic in the area. it could be birds or traffic. They really believed it was birds but ultralights operate out of that airfield.

I was also told ATC could see me when I taxied. Now that I have a hard time believing.

Tony
 
1600vw said:
I fly a small EAB with no transponder for its a single seat. I am located right outside class c airspace.

Some pilots flew in and told me that ATC saw me. They reported to these pilots possible traffic in the area. it could be birds or traffic. They really believed it was birds but ultralights operate out of that airfield.

I was also told ATC could see me when I taxied. Now that I have a hard time believing.

Tony
Click to expand...

With the right aspect angle on that spinning prop and radar coverage to the ground, it is possible. We could see trailer trucks on the highway if we tuned the gain just right.
 
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