Primary vs. Secondary returns, who views them?

[Pi1otguy]

I thought I'd have figured this out by now but my observations seems to be contradictory and useless so I'll ask you guys.

For the people we talk to during our flights who is seeing primary & secondary returns and who is seeing only secondary returns?

For example, the way most delta airports in SoCal talk to us leads me to believe they have radar (shared from SoCal I assume) and that the ones outside the Mode C veil can see primary returns.

I remember getting the impression somewhere that TraCons and Centers generally turn off primary returns because of clutter. But if thats true then does that impact their ability to provide advisories WRT non-transpondered craft?

 

[gismo]

I thought I'd have figured this out by now but my observations seems to be contradictory and useless so I'll ask you guys.

For the people we talk to during our flights who is seeing primary & secondary returns and who is seeing only secondary returns?

For example, the way most delta airports in SoCal talk to us leads me to believe they have radar (shared from SoCal I assume) and that the ones outside the Mode C veil can see primary returns.

I remember getting the impression somewhere that TraCons and Centers generally turn off primary returns because of clutter. But if thats true then does that impact their ability to provide advisories WRT non-transpondered craft?

Secondary (transponder) returns are what is always used by all ATC facilities whenever they are available. AFaIK all TRACONS (approach) and Centers can revert to primary for all aircraft if the beacon system fails or view the primary return of any aircraft they wish. Control towers (Class D) often have a remote feed from a nearby TRACON and I'm pretty certain that this will only show secondary returns no matter what.

I can't imagine that a controller would ever use a primary return when the beacon was available because the beacon display is more accurate, and has better discrimination.

 

[HPNPilot1200]

To add what Lance said, primary returns are often used to track airspace intruders (who happen to have their transponder off or on standby) or those aircraft not equipped with transponders. Primary returns will also display large flocks of birds or other objects to aid the controller in vectoring traffic around those areas.

In some cases, the primary return is just as important or even more important than the secondary. Rarely do the facilities temporarily disable primary targets from being displayed. Your primary and secondary returns are both displayed when being tracked by ATC.

 

[Pi1otguy]

So then what kind objects can the primary radar pick up? Obviously it can pick up our aluminum planes and the metallic mesh of composites, but what about smaller things like ultra lights or even meat missiles? Is the primary target really that useful without an altitude attached to it?

If this is some how sensitive info then I'll understand you not answering.

 

[HPNPilot1200]

So then what kind objects can the primary radar pick up? Obviously it can pick up our aluminum planes and the metallic mesh of composites, but what about smaller things like ultra lights or even meat missiles? Is the primary target really that useful without an altitude attached to it?

If this is some how sensitive info then I'll understand you not answering.

Surprisingly, it can pick up a lot of small things. Like I said earlier, it often picks up flocks of birds, geese, and other foreign objects. Since I'm not a radar technician, I'm not exactly familiar with what exact specifications an object has to have to be seen, but I'd imagine it's most anything that's larger than the size of a bird.

The A90 (Boston TRACON) controllers find the ASR-11 at Logan picks up a lot of birds, and quite often, non-existent objects. Even without a mode C readout, it's sometimes helpful to notify pilots to use caution due to a flock of birds. After a while, you get to know what a flock of birds looks like on the scope, versus an isolated object that probably doesn't exist. There are a lot of variables involved nonetheless.

 

[flyingcheesehead]

So then what kind objects can the primary radar pick up? Obviously it can pick up our aluminum planes and the metallic mesh of composites, but what about smaller things like ultra lights or even meat missiles? Is the primary target really that useful without an altitude attached to it?

I hear a lot of calls like "N123, traffic 1 o'clock and 1 mile, type and altitude unknown, primary target only, might be a flock of birds" type calls... Or at least, I used to. Now that I mention it, I haven't heard that in a while, but I used to hear it all the time. New controllers, perhaps? Hmmm.

 

[vontresc]

I think the bird calls around MSN are more seasonal. Being this close to the Horicon Marsh with all the migrating Sky Carp (Canada Geese), I guess a flock of them will have a primary return. Maybe we can have the bird banders install micro transponders when they band the

Pete

 

[Pi1otguy]

Thank Lance & Jason.

I suppose the bird thing is of varying use to us as our local birds are pigeons, seagulls, and the occasion hawks and they rarely fly in formations > 4 and like to cross our path on short final or 100' AGL on liftoff.

 

[HPNPilot1200]

I hear a lot of calls like "N123, traffic 1 o'clock and 1 mile, type and altitude unknown, primary target only, might be a flock of birds" type calls... Or at least, I used to. Now that I mention it, I haven't heard that in a while, but I used to hear it all the time. New controllers, perhaps? Hmmm.

Probably not. I would lean towards Pete's inference that the birds are more of a seasonal occurrence. You would be amazed how much bird activity shows up on radar here, I've had the privilege of seeing it myself. The most inhibiting limitation on controllers pointing this activity out is that it's real hard to do when the frequency is just too darn busy, so they usually just end up vectoring you around them unless they happen to be getting in the way of the final.