#### chunk75

##### Well-Known Member
Anybody have any RADAR questions? It's an area I know something about and I don't mind answering. It keeps it fresh in my noodle.

Chunk

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Anybody have any RADAR questions? It's an area I know something about and I don't mind answering. It keeps it fresh in my noodle.

Chunk

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I have one,
Do you think he ever got to sample Hot Lips??

!!!!!!!!!!!!

I remember one episode where Radar took a paternity test....I guess he had too much Grape Ne-Hi one night.

Chunk

What the hell are you guys talking about?

I knew there was a MASH joke in here somewhere!!!!

ok here goes.....

I have been in atcs for quite sometime now... how do the radars track the expected altitude IAS etc.. of the aircraft,,,,

General one: wouldnt it be bad if someone using a radar can estimate an A/cs settings;;;;

haree....can you clarify/amplify your question a bit...

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how do the radars track the expected altitude IAS etc.. of the aircraft,,,,

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the expected altitudes are on the flight plan for each aircraft.

the air speed is of no real importance (ICAS/TAS) as it is all relaitive to the other airplanes in the the line. you will be told to slow down or speed up to keep the spacing.

you may get:

Atc: Lear N34J, say airspeed.
us: .78
atc: Lear N34J, maintain .7 in the decent.
us: 4J

or a decent climb at PIC descretion,

once below the FLs it switches over to kts vs M.

Also, RADAR doesn't give a lick about IAS/TAS, it only works in GS.

Distance from antenna @ 'paint' A minus Distance from antenna @ 'paint'B divided by the difference in time in between paints = GS. Distance from antenna is determined by total time from pulse to return of echo divided by 12.36 microseconds (the time required for RADAR waves to travel one mile and back).

Of course, you're talking about multiple paints in one sweep. A paint is one pulse and one echo.

Chunk

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Distance from antenna @ 'paint' A minus Distance from antenna @ 'paint'B divided by the difference in time in between paints..

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chunk, is it "paints" or "POINTS"??

Paint = like an image "painted" on the screen?

Thanks
R2F

A 'paint' is a unofficial, or technical slang, term for "illuminating" a target. Bouncing RADAR energy off of a target is called painting. Sometimes you'll hear the term "skin paint" which is getting a RADAR return unamplified by transponders. It is fairly uncommon for ATC RADAR to skin paint targets unless the aircraft has a large RADAR cross section (RCS) or they are close to the antenna. Approach RADAR's are more likely to get skin paints than Center RADAR because of the precision of the set. Center sets are long range EW (Early Warning) sets meant for max range at the expense of precision. Of course, precision is a relative term....center RADAR may have a resolution of .5nm while an approach set may have a range resolution of .01nm. These numbers are educated guesses...without the parameters of the set, I can't be certain. ATC RADAR relies on transponders to make targets noticable. Military RADAR, on the other hand, has to be powerful enough to rely on skin paints. An enemy target certainly isn't going to have a transponder on to boost the reply.

Clear as mud?

Chunk

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Clear as mud?

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Ah. Clear as mud. Thanks.

Gee...Thanks That was few of the great replies...

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Also, RADAR doesn't give a lick about IAS/TAS, it only works in GS.

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which is sorta interesting,

figure you are doing 150kts ICAS, but your GS is 200kts. ATC sees 200kts and will make all assignments based on that, so you have a 50 kt tailwind, everyone does, that is headed your way. Many times I have heard. N1234 what kind of airplane are you? we are a baron sir, ATC.. huh, N1234, yeah winds. ( Assuming this guy is getting plowed with a headwind. the converse is also true I have heard Skyhawks begging ATC for a GS because they are in a 30-50kt tailwind. I don't know but can find out if anyone is really interested, if ACT keeps the head/tail winds in mind when you are given course changes.

I've got a question actually. Can ATC see the Transponders when you're on the ground waiting for takeoff? I'm assuming they can when you have it switched to altitude but I wasn't sure.

[ QUOTE ]
I've got a question actually. Can ATC see the Transponders when you're on the ground waiting for takeoff? I'm assuming they can when you have it switched to altitude but I wasn't sure.

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I belive it depends on where their radar is located and where you are on the airport. If the secondary radar antenna can't pick up your transponders signal then no, if there is nothing blocking the path between your transponder antenna and the radar than they can see you.

Yeah it absouletely depends on where the radar antenna is located; if you fly out over the ocean here in socal and descend below 500 - 1000 AGL you are virtually guarenteed to get a great big 'RADAR CONTACT LOST' from ATC. If they lose you at 500 feet over nothing but water I'd say it's a great bet they can't see you at all on the ground unless the antenna is actually on the field.

....which brings me to another question: where are the antennas usually located? ...airports? hilltops?

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