What triggers 'Traffic Alert!' from ATC?

[Matthew]

A few months ago I (VFR) was getting in some IMC time with a CFII.

There was a cloud layer that ATC had cleared us into, and had given us a block of altitude so we could stay in the clouds. The layer we were in was part of a front and not very far from us, at our same altitude, the skies were clear.

We got a pretty excited 'traffic alert' from ATC due to oncoming traffic - probably VFR. We turned left and through some breaks in the cloud layer we were in I saw the other aircraft pass by on our right. If he was really 2000 ft horizontal spacing from the clouds for VFR cloud separation, then that's as close as we got, but still closer than I liked. Had we not gotten the alert, we would have popped out of the wall into severe VFR and things would have gotten interesting.

Another note to self: Just because you're in IMC, doesn't mean there isn't somebody else close by that isn't.

I don't really know how close we were to being on the same altitude or converging courses. What triggers a controller to issue 'Traffic alert'?

 

[tonycondon]

I don't really know how close we were to being on the same altitude or converging courses. What triggers a controller to issue 'Traffic alert'?

a bunch of bright lights and sirens go off in the control room, the controller wakes up, and he frantically vectors you to avoid a midair??

just kidding of course, i have no idea what the criteria for those bells and whistles are

 

[HPNPilot1200]

a bunch of bright lights and sirens go off in the control room, the controller wakes up, and he frantically vectors you to avoid a midair??

just kidding of course, i have no idea what the criteria for those bells and whistles are

Typically, conflict alerts in the terminal environment are triggered when aircraft are separated by less than 3nm horizontally or 1,000 feet vertically (within 3nm). In the enroute environment, conflict alerts are triggered when aircraft are separated by less than 5nm horizontally or 1,000 feet vertically (within 5nm), though there are exceptions (ie: Area E sectors in ZBW use terminal radar to control traffic, allowing them to follow the terminal environment rules). Most radar equipment is configured to play different alert sounds to the controller for the different intensities of alerts (conflict, MSAW, etc), but I don't know what those specific criteria are.

The words "traffic alert" (formally called a safety alert, 7110.65R §2-1-6) are spoken when a controller becomes aware of another aircraft flying at an altitude which they believe places your aircraft in unsafe proximity to that other aircraft. In practical terms, it's typically issued when an aircraft is less than a mile from you and you're in dangerously close to it.

 

[jesse]

Typically, conflict alerts in the terminal environment are triggered when aircraft are separated by less than 3nm horizontally or 1,000 feet vertically (within 3nm). In the enroute environment, conflict alerts are triggered when aircraft are separated by less than 5nm horizontally or 1,000 feet vertically (within 5nm), though there are exceptions (ie: Area E sectors in ZBW use terminal radar to control traffic, allowing them to follow the terminal environment rules). Most radar equipment is configured to play different alert sounds to the controller for the different intensities of alerts (conflict, MSAW, etc), but I don't know what those specific criteria are.

The words "traffic alert" (formally called a safety alert, 7110.65R §2-1-6) are spoken when a controller becomes aware of another aircraft flying at an altitude which they believe places your aircraft in unsafe proximity to that other aircraft. In practical terms, it's typically issued when an aircraft is less than a mile from you and you're in dangerously close to it.

Does every conflict report get investigated or are they pretty normal? If not, is there a level of conflict that triggers an alarm that does result in an investigation?

 

[Sticky1]

You think thats close....? Just wait till you get a buzz cut...........

 

[HPNPilot1200]

Does every conflict report get investigated or are they pretty normal? If not, is there a level of conflict that triggers an alarm that does result in an investigation?

No, in fact most conflict alerts are false because the controller has the aircraft in question separated visually or via an exception to the general rule.

That said, the conflict alerts that cause a legal loss of separation (what controllers informally refer to as a "deal") and a few other criteria I don't know are investigated and reports get written up. The "snitch machine" or the conflict detecting software picks these up.

Here's what a conflict alert (CA) looks like on STARS (terminal) radar:

 

[swamppilot]

A traffic alert is issued when, in a controller's judgement, two aircraft are in unsafe proximity to each other. Conflict alert may or may not be involved. Traffic alerts are usually issued between a VFR and an IFR aircraft. Appraoch controls may issue traffic alerts between two VFR's. ARTCC's (centers) do on rare occassions. In ARTCC airspace, there are no separation requirement between IFR and VFR aircraft, and if the situation is such that the conflict alert program recognizes one aircraft as a VFR, it may not generate a conflict alert message.

You probably would not hear a traffic alert between two IFR aircraft. The controller would be issuing a climb/descend or turn IMMEDIALTELY message in that instance.

 

[flyingcheesehead]

I've heard two different horns/buzzers/bleepers/whatever in the background when controllers have given traffic calls, the more insistent of which generally corresponds to an increase in pitch, speed, and volume in the controller's voice...

 

[Matthew]

The words "traffic alert" (formally called a safety alert, 7110.65R §2-1-6) are spoken when a controller becomes aware of another aircraft flying at an altitude which they believe places your aircraft in unsafe proximity to that other aircraft. In practical terms, it's typically issued when an aircraft is less than a mile from you and you're in dangerously close to it.

We were talking to Kansas City Approach, not far enough out to be with Kansas City Center. The controller was trying to get our call sign and 'traffic alert' out as fast as she could. She reported traffic at 1 o'clock, but I don't remember the distance. Had we continued, from what I could tell, we would have been converging on the other a/c at his 1:00. From those 1:00 vs 1:00 positions, it seems as if we would have skimmed past each other, but with our maneuvering, it was hard to tell just how we were oriented. As I said, I really couldn't tell how close we were vertically, we banked prettly steeply to the left. If he was maintaining VFR cloud clearance, we were at least 2000' apart horizontally at the time of the alert, but 2000' can disappear quickly.

It was one of those things that didn't shake me up or really bother me until the next day when I started replaying it in my head.

 

[Matthew]

You think thats close....? Just wait till you get a buzz cut...........

heh - the closest I've gotten was on downwind doing touch/goes, when somebody entered the pattern on the mid-field downwind in front of and underneath me. I pitched up pretty steeply to not run over him. I was just a lowly student back then, my CFI was with me, and I was pretty $)(*%$ mad.

 

[Ted]

Get too low at night landing VFR on a long final will at some Airports get you a Terrain alert from Tower with a bell going off in the background. Exactly the same time the Garmin 530W gives you a Terrain alert. Nice to know they sometimes have that ability!

A month or so ago I was flying in a G1000-equipped 182 in VFR conditions. Visibility was very good (can't remember exact numbers). The G1000 calmly said to us "Traffic". Sure enough, a plane ahead of us that neither the PIC nor I saw. We changed course. Had we not gotten the warning, the plane was still not coming directly for us, but it was a little closer than we wanted.

Lesson: Just because you're in the middle of nowhere at an airport that gets no activity, doesn't mean you're the only one there.

 

[KennyFlys]

A month or so ago I was flying in a G1000-equipped 182 in VFR conditions. Visibility was very good (can't remember exact numbers). The G1000 calmly said to us "Traffic". Sure enough, a plane ahead of us that neither the PIC nor I saw. We changed course. Had we not gotten the warning, the plane was still not coming directly for us, but it was a little closer than we wanted.

Lesson: Just because you're in the middle of nowhere at an airport that gets no activity, doesn't mean you're the only one there.

Last year, I was being vectored west a ways before I could turn southwest. I was in a 172 with G1000, level at 6,000 feet, about 4,000 AGL. TIS indicated traffic but I could not spot a thing. Suddenly, it was showing very close, to my right and headed toward me. Nothing yet. My head was spinning something awful. I killed the AP and banked hard to look each side. Still nothing.

I called Atlanta and asked "Verify traffic my immediate vicinity." The controller said there was traffic behind me but not a factor. "Not a factor"??? Try telling the yellow aleart icons on my screen that! The odd thing is, within five seconds after she said it was no factor, the icon disappeared from the display.

The only thing I could figure was an aircraft climbing toward me from below and well out of my vision. He continued to behind me but came close enough for a stronger alert from TIS.

Or, it was a UFO....

 

[Matthew]

I was aproaching an airport to circle overhead - coming in from the south. I heard a traffic call from a cirrus coming in from the north, but he didn't mention his distance or altitude. I gave another position report as I got closer, still looking for the cirrus. Cirrus gave another report without distance or altitude. I think I was overhead the airport and had to ask, twice I think, for a better position report from the cirrus. His response was "it's OK, I have you on TCAS" - my best guess is that he was somewhere below me, but I never did see him until he was on final.

 

[SkyHog]

Want fun? Fly in Albuquerque's Class C sometime, and listen to the controllers. You'll hear constant "beep beep beep beep" behind almost every call, because they are always putting GA too close to the Southwest jets. Not sure why, but its interesting to hear "Cherokee, traffic, 12 o'clock, 2 miles, 737, same altitude" with "BEEP BEEP BEEP BEEP BEEP BEEP" in the background.

Of course I see it.

 

[flyersfan31]

Lesson: Just because you're in the middle of nowhere at an airport that gets no activity, doesn't mean you're the only one there.

Last summer I was enjoying an evening flight to my favorite airport for building XC time, 9D4 (Myerstown/Deck, 50.3 mi from Wings). I remember thinking how nice it was to have the 330 transponder with TIS in my Sundowner, because it really helped with traffic spotting. Fortunately, I was still scanning outside, but content in figuring the box would warn me long before there was a problem.

All of a sudden I spot something close by on my right, same altitude, heading for an intercept. It was a friggin ultralight - no transponders on those suckers. Powered up and pulled up, but it was a bit exciting. He was in the twilight haze, low enough so he wasn't silhouetted against the sky.

It was like someone had been reading my thoughts and decided to send me a little reminder.

 

[Teller1900]

Had to make a go-around at LGA because a 737 didn't clear in time. On the climb out, we have to cross the arrival cooridor for both LGA and JFK, as well as the VFR Fly-way over the Hudson. LGA Tower and NY Approach give us a few vectors around a couple airliners in the area that had our TCASII lit up. Just then another yellow target pops up on the TCAS, acompanied by the obnoxious "Traffic, Traffic" aural alert...1000feet below and climbing as we're leveling off at 3000. Nothing from approach.


We wait a second or two, still scaning the horizon, but the TCAS says he's still decending. Then the oral "Monitor Verticle Speed" sounds as the target turns red. We now have a red bar painted on our VSI from -6000fpm up to 500fpm with everything else green. I start to pull a little bit..."Traffic, Climb Climb Climb, Traffic, Climb..." I slam the power levers forward and pull the yoke back hard to put the VSI into the green arc, now at 2000fpm and above."

There seems to be about a 6-8 second delay in the approach radar, because it was about three seconds from when the power went forward until "Colgan 4832, Traffic Alert, VFR traffic 12 o-clock less than a mile descending through your altitude - immediate climb...expidite the climb, I'm not talking to him!"

No altitude assigned from approach, still no visual, and the TCAS is screaming (and I'm pretty sure half the passengers just soiled themselves)...I keep pulling.

Long story short, we were blasting through 5000 feet at 2700fpm before the TCAS announced "Clear of Conflict" and I felt comfortable lowering the nose.

"You still with us, Colgan?" approach asks next. That's encouraging.

"Who the hell was that??" my CA practically yells into the mic.

New voice on approach..."Colgan 4832, contact New York Approach on 120.8. Nice job."

There was beeping in the back ground for that one.

 

[Ted]

That seems like an "Oh ****" situation, with excellent response to said situation.

 

[wsuffa]

Welcome to New York.