Approach control

[bluerooster]

How close are targets when they merge on your scope?
I was departing FFC today, and contacted ATL approach for the VFR corridor over ATL. I'm climbing through 3000 for 4500, I get a code, then "radar contact, traffic at 12:00 your altitude, 1 mile, turn left now!" I don't see the traffic, nose high, yank it over for a hard 90 degree turn to the left.
As I roll out, I get; "Traffic now 1/2 mile at your 12:00, do you see it?" I see it off my left wing, passing behind me, about 1/2 mile away. I gave that information to ATC. He sounded a little panicked with his reply, (not that I blame him) "You need to reply, why didn't you reply when I told you about the traffic?" I was taught to aviate first, communicate last. I maneuvered as instructed for traffic avoidance, and he came at me as though I might not be able to answer due to a calamity. I'm wondering if he saw the two targets merge, and worried that we may have hit? I'll admit we were pretty close, and had I not made the left turn when I did, we may have collided head on. I did repeat the instruction" NXXX left turn for traffic", as I was unloading, and yanking it into a 60* bank turn, for 90*. I may have been stepped on, or I may have not pushed the mic button. But either way I followed the instruction, and reported traffic when I got it in sight.
After that little bit of excitement, we had a good trip through the Bravo. Had I elected to go around the B, Or had been told to stand by, there could have been a way different outcome. I'm glad that controller picked me up, gave me a squawk, and radar was quick to pick me up.

 

[JAX]

The range on the scope will determine how close the targets look like they get. In a typical TRACON radar updates are 1 second and fed by multiple radars. They are extremely accurate. The scopes are pretty zoomed in compared to a Center. Sounds like the controller gave you a proper traffic alert and the traffic was in fact imminent. Good job.

 

[Bob Noel]

small correction: TRACON radars have approximately a 4 second sweep. a correction to my correction: ~5 seconds.

 

[JAX]

small correction: TRACON radars have approximately a 4 second sweep. a correction to my correction: ~5 seconds.

Most TRACONs are using FUSED radar now. It is several radar feeds fed into the computer which displays the targets moving with around a one second update. Each individual radar spins slower but when you combine 6 radars plus adsb the tracks move fluidly.

 

[luvflyin]

How close are targets when they merge on your scope?
I was departing FFC today, and contacted ATL approach for the VFR corridor over ATL. I'm climbing through 3000 for 4500, I get a code, then "radar contact, traffic at 12:00 your altitude, 1 mile, turn left now!" I don't see the traffic, nose high, yank it over for a hard 90 degree turn to the left.
As I roll out, I get; "Traffic now 1/2 mile at your 12:00, do you see it?" I see it off my left wing, passing behind me, about 1/2 mile away. I gave that information to ATC. He sounded a little panicked with his reply, (not that I blame him) "You need to reply, why didn't you reply when I told you about the traffic?" I was taught to aviate first, communicate last. I maneuvered as instructed for traffic avoidance, and he came at me as though I might not be able to answer due to a calamity. I'm wondering if he saw the two targets merge, and worried that we may have hit? I'll admit we were pretty close, and had I not made the left turn when I did, we may have collided head on. I did repeat the instruction" NXXX left turn for traffic", as I was unloading, and yanking it into a 60* bank turn, for 90*. I may have been stepped on, or I may have not pushed the mic button. But either way I followed the instruction, and reported traffic when I got it in sight.
After that little bit of excitement, we had a good trip through the Bravo. Had I elected to go around the B, Or had been told to stand by, there could have been a way different outcome. I'm glad that controller picked me up, gave me a squawk, and radar was quick to pick me up.

Depends on the Radar. Not merging is called 'Target Resolution.' Some have more 'resolution' than others. Some will be displaying Primary Radar. How fat the blips are will vary. If displaying only Secondary Radar or Digitized displays it will vary. Here be the rules.

5−5−3. TARGET RESOLUTION
a. A process to ensure that correlated radar targets or digitized targets do not touch.
b. Mandatory traffic advisories and safety alerts must be issued when this procedure is used.
NOTE−
This procedure must not be provided utilizing mosaic radar systems.
c. Target resolution must be applied as follows:
1. Between the edges of two primary targets or the edges of primary digitized targets.
2. Between the end of the beacon control slash and the edge of a primary target or primary digitized target.
3. Between the ends of two beacon control slashes.

 

[Tokirbymd]

How close are targets when they merge on your scope?
I was departing FFC today, and contacted ATL approach for the VFR corridor over ATL. I'm climbing through 3000 for 4500, I get a code, then "radar contact, traffic at 12:00 your altitude, 1 mile, turn left now!" I don't see the traffic, nose high, yank it over for a hard 90 degree turn to the left.
As I roll out, I get; "Traffic now 1/2 mile at your 12:00, do you see it?" I see it off my left wing, passing behind me, about 1/2 mile away. I gave that information to ATC. He sounded a little panicked with his reply, (not that I blame him) "You need to reply, why didn't you reply when I told you about the traffic?" I was taught to aviate first, communicate last. I maneuvered as instructed for traffic avoidance, and he came at me as though I might not be able to answer due to a calamity. I'm wondering if he saw the two targets merge, and worried that we may have hit? I'll admit we were pretty close, and had I not made the left turn when I did, we may have collided head on. I did repeat the instruction" NXXX left turn for traffic", as I was unloading, and yanking it into a 60* bank turn, for 90*. I may have been stepped on, or I may have not pushed the mic button. But either way I followed the instruction, and reported traffic when I got it in sight.
After that little bit of excitement, we had a good trip through the Bravo. Had I elected to go around the B, Or had been told to stand by, there could have been a way different outcome. I'm glad that controller picked me up, gave me a squawk, and radar was quick to pick me up.

Good reason to have ads b display in cockpit. Have been surprised many times on adsb by airplanes I never saw

 

[luvflyin]

Most TRACONs are using FUSED radar now. It is several radar feeds fed into the computer which displays the targets moving with around a one second update. Each individual radar spins slower but when you combine 6 radars plus adsb the tracks move fluidly.

Here's more detail about that for anyone who is interested. https://www.icao.int/APAC/Documents/edocs/cns/grpt_atcmulti_adsbdata.pdf

 

[Velocity173]

If the targets have merged, then they’re combined or overlapped. That’s why ATC in some cases uses merging target procedures. They provide traffic and follow with the phrase “targets appear likely to merge.” Meaning- it looks like they’re going to touch if no one adjusts their course.

And if you were up Atlanta TRACON, they use FUSION so as stated above, it’s a 1 sec refresh rate. 4-5 secs is old school single source radar like what I used. Very few facilities these days are still doing that.

 

[luvflyin]

If the targets have merged, then they’re combined or overlapped. That’s why ATC in some cases uses merging target procedures. They provide traffic and follow with the phrase “targets appear likely to merge.” Meaning- it looks like they’re going to touch if no one adjusts their course.

And if you were up Atlanta TRACON, they use FUSION so as stated above, it’s a 1 sec refresh rate. 4-5 secs is old school single source radar like what I used. Very few facilities these days are still doing that.

Yeah. Here's Merging Target Procedures.

5−1−4. MERGING TARGET PROCEDURES
a. Except while they are established in a holding pattern, apply merging target procedures to all radar identified:
1. Aircraft at 10,000 feet and above.
2. Turbojet aircraft regardless of altitude.
REFERENCE−
P/CG Term − Turbojet Aircraft.
3. Presidential aircraft regardless of altitude.
b. Issue traffic information to the aircraft listed in subparagraph a whose targets appear likely to merge unless the aircraft are separated by more than the appropriate vertical separation minima.
EXAMPLE−
“Traffic twelve o’clock, seven miles, eastbound, Gulfstream 650, one seven thousand.”
“United Sixteen and American Twenty−Five, traffic twelve o’clock, one zero miles, opposite direction, eastbound Seven
Thirty−Seven at flight level three three zero, westbound Airbus Three Twenty at flight level three two zero.”
REFERENCE−
FAA Order JO 7110.65, Para 2−4−21, Description of Aircraft Types.
c. When both aircraft in subparagraph b are in RVSM airspace and vertically separated by 1,000 feet, and either pilot reports they are unable to maintain RVSM due to turbulence or mountain wave, use vectors to prevent the targets from merging.
EXAMPLE−
“Delta One Twenty−Three, fly heading two niner zero, vector for traffic. Traffic twelve o’clock, one zero miles, opposite direction, Seven Thirty−Seven, eastbound at flight level three one zero.”
d. If the pilot requests, vector their aircraft to avoid merging targets with the previously issued traffic.
NOTE−
Because aircraft closure rates can be rapid, issue traffic with enough time for the pilot to decide if a vector is necessary.
e. If unable to provide vector service, inform the pilot.
NOTE−
The phraseology “Unable RVSM due to turbulence (or mountain wave)” is only intended for severe turbulence or other weather encounters with altitude deviations of approximately 200 feet or more.

Of course for a lot of us we aren't above 10,000 a lot, aren't turbojets and aren't the Prez but this pretty much covers the same territory.

2−1−6. SAFETY ALERT
Issue a safety alert to an aircraft if you are aware the aircraft is in a position/altitude that, in your judgment, places it in unsafe proximity to terrain, obstructions, or other aircraft. Once the pilot informs you action is being taken to resolve the situation, you may discontinue the issuance of further alerts. Do not assume that because someone else has responsibility for the aircraft that the unsafe situation has been observed and the safety alert issued; inform the appropriate controller.
NOTE−
1. The issuance of a safety alert is a first priority (see paragraph 2−1−2, Duty Priority) once the controller observes and recognizes a situation of unsafe aircraft proximity to terrain, obstacles, or other aircraft. Conditions, such as workload, traffic volume, the quality/limitations of the radar system, and the available lead time to react are factors in determining whether it is reasonable for the controller to observe and recognize such situations. While a controller cannot see immediately the development of every situation where a safety alert must be issued, the controller must remain vigilant for such situations and issue a safety alert when the situation is recognized.
2. Recognition of situations of unsafe proximity may result from MSAW/E−MSAW, automatic altitude readouts, Conflict/Mode C Intruder Alert, observations on a PAR scope, or pilot reports.
3. Once the alert is issued, it is solely the pilot’s prerogative to determine what course of action, if any, will be taken.
a. Terrain/Obstruction Alert. Immediately issue/initiate an alert to an aircraft if you are aware the aircraft is at an altitude that, in your judgment, places it in unsafe proximity to terrain and/or obstructions. Issue the alert as follows:
PHRASEOLOGY−
LOW ALTITUDE ALERT (call sign),
CHECK YOUR ALTITUDE IMMEDIATELY.
and, if the aircraft is not yet on final approach,
THE (as appropriate) MEA/MVA/MOCA/MIA IN YOUR AREA IS (altitude).
REFERENCE−
P/CG Term − Final Approach − IFR
b. Aircraft Conflict/Mode C Intruder Alert. Immediately issue/initiate an alert to an aircraft if you are aware of another aircraft at an altitude that you believe places them in unsafe proximity. If feasible, offer the pilot an alternate course of action. When an alternate course of action is given, end the transmission with the word
“immediately.”
PHRASEOLOGY−
TRAFFIC ALERT (call sign) (position of aircraft) ADVISE YOU TURN LEFT/RIGHT (heading),
and/or
CLIMB/DESCEND (specific altitude if appropriate) IMMEDIATELY.
EXAMPLE−
“Traffic Alert, Cessna Three Four Juliett, 12’o clock, 1 mile advise you turn left immediately.”
or
“Traffic Alert, Cessna Three-Four Juliett, 12’o clock, 1 mile advise you turn left and climb immediately.”

 

[bluerooster]

I'll estimate the close rate between me and the other target to be ~200mph. I was at 80 climbing, and traffic was a similar aircraft I'll give ~120. So that would be about 20 seconds to close the gap. About 4 or 5 radar sweeps. Would the controller have seen on his screen my 90* left turn, prior to the two targets coming together? Being APP, I would assume that the resolution to be set pretty high, Especially ATL APP with several sectors. And probably only one or two controllers for all the sectors.

 

[bluerooster]

Yeah. Here's Merging Target Procedures.


EXAMPLE−
“Traffic Alert, Cessna Three Four Juliett, 12’o clock, 1 mile advise you turn left immediately.”

That's the call I got, without the words "advise you".

I'm not trying to bash anyone, but want to understand why the controller came at me as though i did something wrong. And based upon the replys here, I guess it was the stress of watching two targets merge, on his watch, and not knowing If evasive maneuvers were taken in time to avoid a calamity. So, I suppose two of us take a scoop from the bucket of luck, and deposit it into the bucket of experience.
I would like to meet that controller, shake his hand, and buy him lunch.

 

[JAX]

I'll estimate the close rate between me and the other target to be ~200mph. I was at 80 climbing, and traffic was a similar aircraft I'll give ~120. So that would be about 20 seconds to close the gap. About 4 or 5 radar sweeps. Would the controller have seen on his screen my 90* left turn, prior to the two targets coming together? Being APP, I would assume that the resolution to be set pretty high, Especially ATL APP with several sectors. And probably only one or two controllers for all the sectors.

The FAA did some studies a few years ago. The time it takes for a controller to issue a proper traffic alert, the pilot acknowledge, the pilot turn, and the radar pick it up is around 15 seconds. So your math adds up. Probably looked bad on the scope.

 

[Bob Noel]

especially with latency... targets on the glass have a measurable latency.

 

[luvflyin]

That's the call I got, without the words "advise you".

I'm not trying to bash anyone, but want to understand why the controller came at me as though i did something wrong. And based upon the replys here, I guess it was the stress of watching two targets merge, on his watch, and not knowing If evasive maneuvers were taken in time to avoid a calamity. So, I suppose two of us take a scoop from the bucket of luck, and deposit it into the bucket of experience.
I would like to meet that controller, shake his hand, and buy him lunch.

You did fine. Don't worry about a wrapped up tight Controller going off. Many times they are doing it for the audience of the other Controllers in the room. Like 'this ain't my fault it's this guys fault. Many of the audience on the frequency have heard this before and know the score.

 

[PastZTL]

You did fine. Don't worry about a wrapped up tight Controller going off. Many times they are doing it for the audience of the other Controllers in the room. Like 'this ain't my fault it's this guys fault. Many of the audience on the frequency have heard this before and know the score.

I've seen my share of these events and I never saw a response directed at the control-room audience. It is horrifying to see an aircraft on your frequency on a trajectory that will likely collide with another. After the A80 controller gave the safety alert and received no response I'm sure the reaction later was fueled by the pent-up stress created in the moment.