Flight Following ... Close call

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PaulMKE

Pre-takeoff checklist
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PaulMKE
This weekend, returning home from a family visit, short 30 min flight. This plane has a 530 with ADSB in/out, and since I'm using foreflight for navigation I use the 530 mainly as a TCAS. I love the TCAS because I see traffic on the screen long before I can find them in the air. But I force myself to do both whenever possible.

Still, I like having a second set of eyes, so I always ask for FF. Airspace here is quiet so rarely a problem. After a few run of the mill advisories, I noted no targets on the TCAS. Then this (my heading ~160):

9SR, traffic 11oclock 3 miles, northbound no altitude reading.
-9SR is looking. (Nothing on TCAS, hmm)
<very quickly >
9SR, do you have the traffic? Now 12oclock 2 miles.
-9SR, negative traffic.
9SR turn 180 for traffic avoidance.

So I begin my turn, as soon as my nose moved 10 degrees I see a C172 pointed right at me less than a mile, climbing to my altitude. We pass each other about 1/2 mile apart.

-"Uh, 9SR has the traffic now, :eek: that was close."
9SR confirm you have traffic?
-confirm traffic in sight 9SR.
Roger continue on course.

Classic high wing/low wing visual obscuration. So the tools are great, our eyes are great, but nothing like having redundancy and someone to talk to and looking out for you. Thanks to all of you controllers, think I can say very likely that controller saved at least three lives last weekend.
 
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Which TCAS is installed in this aircraft?
 
I'm embarrassed that I don't know. I'll find out.
 
You mentioned ADS-B, then TCAS. Do you have both?

ADS-B traffic is called TIS-B, which is very different from TCAS.

TIS-B often fails to show nearby traffic for me, even though I am equipped for ADS-B out.
 
Thanks. I found this reference:
http://www.maxcraft.ca/blog/confused-about-traffic-systems-tcas-pcas/

I know the aircraft is ADS-B equipped, so I'm guessing it is TIS and not TCAS. I've been referring to it as TCAS because (a) didn't realize the technical differences and (b) one of my CFIs began calling it that and it stuck.

As you say, after the other aircraft passed, the target showed up.
 
Couple of things. As you've seen TCAS and TIS and ADSB are all different things, and ADSB can be implemented in different ways. Recent reports from a number of folks here are seemingly confirming that ADSB isn't always getting the job done. Be cautious relying on it. Well, be cautious relying on any of them.

Second, I have picked up a habit of wanting to make a slight turn whenever it sounds like I'm climbing into someone with a high wing or descending in a low wing, just to take a peek. It doesn't always help, but I've seen that scenario set up a few times now, and sometimes adding a little relative motion for a head on with the rudder will make that traffic "pop" out of the background. Human eyeballs look for motion.
 
denverpilot said:
Couple of things. As you've seen TCAS and TIS and ADSB are all different things, and ADSB can be implemented in different ways. Recent reports from a number of folks here are seemingly confirming that ADSB isn't always getting the job done. Be cautious relying on it. Well, be cautious relying on any of them.
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Good advice. I'm still not sure why ADS-B sometimes does not show targets that ATC sees. In this case, I wonder if it might have been that it was a primary target only (as reported no Mode C, possibly no transponder at all).
 
azure said:
Good advice. I'm still not sure why ADS-B sometimes does not show targets that ATC sees. In this case, I wonder if it might have been that it was a primary target only (as reported no Mode C, possibly no transponder at all).
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We've had some long discussions here about the problems with "no hockey puck" if you're only running ADSB "In" in the Stratux threads, but there's also been hints that folks are running "Out" so they should have a "puck" and still not receiving some targets.

It would be fascinating but a part time job to try to correlate it all from logs from things like Stratux users, or you'd really need some sort of special permission and the full ATC feed and a receiver near all the local 978 transmitters to debug what's going missing, if anything.

Could also be poor reception due to antenna location on an airframe or all sorts of other problems, besides the tower not sending the traffic up.

That's one of the serious downsides to the whole thing if you ask me, there's no end to end Ack/Nak of transmitted data. It's spray and pray over a wireless link, and that's never 100% infallible. Ever.

BTDT, got the t-shirt.

TCAS is totally different and isn't spray and pray. The two airfraft's systems communicate with each other or the system figures out an escape vector from a non-participating transponder. Much more active collision avoidance than ADSB or TIS.

It doesn't take much to mangle a few packets in the real world.
 
denverpilot said:
We've had some long discussions here about the problems with "no hockey puck" if you're only running ADSB "In" in the Stratux threads, but there's also been hints that folks are running "Out" so they should have a "puck" and still not receiving some targets.
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Not a hint in my case, personal experience. I have a GDL-90 with active Out and so should have the "hockey puck". It doesn't happen often, but it does happen.
 
I've had a few similar close calls. Each time it has involved another airplane not using their radio. One was close enough the airfield manager went out and last I heard he was screaming at a pilot. I was on short final on runway 31 and he decided to drop in a short final on runway 13 about the time i touched the ground.
 
My last close call was in the pattern (RP 28 and Left 10). There were 4 of us closed traffic left pattern RWY 10. I was number one in the conga ... my highly advanced MarkXXV eyes detected opposite direction traffic. I climbed a little, and got a GREAT look at the offender and his N-number and announced on CTAF to the 3 behind me that 123PR is opposite direction in the pattern at my current position ... I got three immediate "thanks" followed by a sheepish "I'm sorry guys my volume was down".
 
I had something like this happen to me on the way back from KMLB. Got to the Zephyhills area and ATC calls out traffic at my 3 O'Clock altitude unknown, 3 miles. So I'm looking...nothing.

All of a sudden this glider comes out from no where straight at me, my altitude, which was an even altitude going west + 500. They were at the wrong altitude with no reporting equipment, no radios. I pulled up to let it pass beneath me, which it did.

Reported it to ATC who told me they weren't even supposed to be there. Gliders have a specific area of operation (usually around KZPH).

Head on a swivel..head on a swivel..
 
These things happen (despite the "big sky" theory) and I am always thankful for the controllers watching over me.
My latest close encounter was south of the DFW Bravo where I got 2 calls from the nice Regional Approach guy about rapidly climbing traffic at 1 o'clock and 3 miles, then 2 miles, then "suggest immediate left turn 20 degrees" in a slightly elevated tone of voice (I assume the ringing wasn't in his ears but instead on his console where our two blips were flashing red).
The light twin passed through our altitude to our right, a few hundred feet from our original course. To us in the cockpit, it felt like normal VFR separation, to him behind the radar screen, it must have felt like an imminent collision so I feel bad for not deviating earlier but all-in-all, it was a non-event.
Again, I am thankful for FF and traffic advisories, they help us stay safe.
 
Caramon13 said:
I had something like this happen to me on the way back from KMLB. Got to the Zephyhills area and ATC calls out traffic at my 3 O'Clock altitude unknown, 3 miles. So I'm looking...nothing.

All of a sudden this glider comes out from no where straight at me, my altitude, which was an even altitude going west + 500. They were at the wrong altitude with no reporting equipment, no radios. I pulled up to let it pass beneath me, which it did.

Reported it to ATC who told me they weren't even supposed to be there. Gliders have a specific area of operation (usually around KZPH).

Head on a swivel..head on a swivel..
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Controlled airspace or not?

Gliders have no particular "area of operation". A great many make cross countries of hundreds of miles and don't have transponders on board.

(Will go ping Tony... For more informed commentary...) :)
 
denverpilot said:
Controlled airspace or not?

Gliders have no particular "area of operation". A great many make cross countries of hundreds of miles and don't have transponders on board.

(Will go ping Tony... For more informed commentary...) :)
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I'd have to look at my track again, but I was either just about to enter Bravo airspace or in it already. I was between KZPH and KPCM. Bravo shelf there is at 3,000. I was at 4500 IIRC. I know they are exempt from the transponder requirements but that is OUTSIDE Bravo airspace, which if I was in, they were too.
 
PaulMKE said:
So I begin my turn, as soon as my nose moved 10 degrees I see a C172 pointed right at me less than a mile, climbing to my altitude. We pass each other about 1/2 mile apart.

.
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Having trouble visualizing the geometry. How does high or low wing affect headon visibility?
 
Where is everyone flying where you are seeing all this traffic? I don't think I've seen another plane while I was flying in months...no joke! I used FF the other day, and didn't get a single advisory in 200 miles.
I flew 20 years ago, and saw planes in this area all the time...I take a 10 year break, come back, and the CTAF's are all dead, and I always feel all alone.
 
tawood said:
Where is everyone flying where you are seeing all this traffic? I don't think I've seen another plane while I was flying in months...no joke! I used FF the other day, and didn't get a single advisory in 200 miles.
I flew 20 years ago, and saw planes in this area all the time...I take a 10 year break, come back, and the CTAF's are all dead, and I always feel all alone.
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Depends on where you are.
 
Not all that close, really, at GA speeds. . .slight turn, still at diffrent altitudes, and 1/2 mike lateral.
 
I have ADS-B in and Out on my Cherokee. It has always shown traffic that is within range of the local Radar facility. (Until the other day) I was leaving Louisville International's Class C airspace around 1am. There was very heavy UPS traffic and all of them were showing up on my screen.. (TIS-B, and 978/1090 direct traffic) Then I see a large aircraft flying 500-1000' above me and nothing at all on my screen.. So I am not sure why I didn't see him. I am guessing he possibly didn't have his transponder switched to ALT or something was wrong with it. I figured the ADS-B system filtered him out. It seems that primary targets without altitude encoding will not be relayed.. but I have also seen TIS-B targets without altitude.. So I dunno!
 
tawood said:
Where is everyone flying where you are seeing all this traffic? I don't think I've seen another plane while I was flying in months...no joke! I used FF the other day, and didn't get a single advisory in 200 miles.
I flew 20 years ago, and saw planes in this area all the time...I take a 10 year break, come back, and the CTAF's are all dead, and I always feel all alone.
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You're really teeing it up for those of us with "LA basin" comments. :D
 
Indiana_Pilot said:
I have ADS-B in and Out on my Cherokee. It has always shown traffic that is within range of the local Radar facility. (Until the other day) I was leaving Louisville International's Class C airspace around 1am. There was very heavy UPS traffic and all of them were showing up on my screen.. (TIS-B, and 978/1090 direct traffic) Then I see a large aircraft flying 500-1000' above me and nothing at all on my screen.. So I am not sure why I didn't see him. I am guessing he possibly didn't have his transponder switched to ALT or something was wrong with it. I figured the ADS-B system filtered him out. It seems that primary targets without altitude encoding will not be relayed.. but I have also seen TIS-B targets without altitude.. So I dunno!
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Why would the assumption be that he wasn't squawking alt properly instead of the ground computer of a relatively new system screwing up and not sending the data (bug, whatever), or the receiver in your aircraft missing the data due to noise in the environment since the system is spray and pray?

Doesn't make any sense to me as a data engineer. All of those are as likely as the other, considering its limitations.

It's what design engineers call a "best effort" data system. No guarantees you'll get anything useful from it, but you probably will get something.

It's not a two-way ack/nak "guaranteed delivery" type of system. Not designed to be. Stuff is guaranteed to go missing.

Anyway, even if it was because he wasn't squawking an altitude, that's completely permissible with a waiver/ferry permit at lower altitudes, so ... Going to happen then, too, if the system doesn't send those up.
 
Just so everyone should know, ADS-B TISB targets are not generated for Mode A only or primary targets. If the controller calls the traffic as altitude unknown, you will not see it with TISB. This is one case where a TCAS, TAS, or TIS system will provide the target azimuth without a relative altitude being provided. TIS is aka TIS-A for folks who like to use acronyms without a meaning.
 
tawood said:
Where is everyone flying where you are seeing all this traffic? I don't think I've seen another plane while I was flying in months...no joke! I used FF the other day, and didn't get a single advisory in 200 miles.
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When I visit my son in Austin, there is very heavy traffic from Llano on in to Austin Exec ... lots of airports in that last 40 minutes of flight. I have TCAS and TIS running, but that sometimes doesn't catch everyone that is nearby. Out in my area maybe only 4-5 near the pattern and then clear if heading cross country.
 
John Collins said:
Just so everyone should know, ADS-B TISB targets are not generated for Mode A only or primary targets. If the controller calls the traffic as altitude unknown, you will not see it with TISB. This is one case where a TCAS, TAS, or TIS system will provide the target azimuth without a relative altitude being provided. TIS is aka TIS-A for folks who like to use acronyms without a meaning.
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Most "folks" don't even know there are a mountain of systems, let alone care what they're called. Nor should they really. They call it "I have traffic" on their "gadget".

Nor does one see any marketing material from anyone selling anything based on ADS-B for "traffic" as having the limitations that it does, which are baked in. You *might* find it in the docs that came with the "gadget" but usually not.

It'd make for a decent FAASTeam seminar though, explaining the multitude of possible failure modes of all of them. Title would be "Don't trust your traffic gadget [we didn't engineer it that well]."
 
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