ADS-B Traffic Out...Can someone please help me understand?

VWGhiaBob

VWGhiaBob

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VWGhiaBob
Sporty's and others are pushing and touting the new Stratus' ADSB traffic capabilities on the iPad. But the fine print says, "Note: ADS-B traffic is limited unless your aircraft has ADS-B Out installed in the panel."

So what, exactly, does "limited" mean. If I simply have the Stratus and iPad, what are the limitations?

Someone told me the limitation is that without ADS-B out, I'll still see traffic, but only if another aircraft is in the vicinity. So many questions...

* What does same vicinity mean? 10NM? 5NM? Same Radar Zone?
* If there's no ADS-B plane in the vicinity, will I see ANY traffic? If so, what traffic will I see?
* If there is an ADS-B Out plane in the vicinity, will I still see ALL traffic that ATC sees? Or are there other limitations?
* I fly in So. Cal. where there are always lots of planes with ADS-B out everywhere. So will I usually see all the traffic ATC sees?

If anyone understands these concepts, I'd appreciate the input!
 
Basically, ADSB-Out sends out a broadcast (it's what the B stands for), which is the digital equivalent of "Any traffic in the area please advise". All the other aircraft in the area with then send out their ADS-B data-blocks.

So, without ADSB-Out, you are dependent upon someone else saying ATITAPA, and range of that is partly dependent upon transmitter power, and partly altitiude/line of sight.
 
The ground stations doesn't broadcast all the traffic that they know about over ADS-B all the time. They only do so when there is an ADS-B out equipped aircraft in the area then they send the traffic within the "hockey puck" zone around that aircraft. So, without ADS-B out you will only see other ADS-B equipped aircraft and the traffic in their hockey puck that overlaps with where you are.

If you're in a real busy area you'll get traffic most likely, if not you may not see it until an ADS-B equipped aircraft strays by.

Sort of a herd immunity thing :)
 
Maybe I spoke too soon. I just found 2 great resources that explain this in detail. It's actually very complex. The short answer is that if you don't have ADS-B out, you only see complete traffic if you happen to be within 15 NM and +-3,500 feet of an ADSB-Out plane. In effect, you are seeing a signal intended for that plane.

I'd be interested if there are folks out there without ADS-B Out who have tried the stratus. When you fly in really busy areas, is the traffic information useful and complete most of the time?

I realize there are those who think traffic isn't necessary. I disagree. There are just too many times when I see traffic on the Cirrus that I don't see with my eyes.

Here's what I found:
http://www.youtube.com/watch?v=QPPTzj2G7Yk&feature=share&list=UUDZjCZ1CA_I8VQW0zOxSBPw

http://www.faa.gov/nextgen/implementation/programs/adsb/faq/
 
So a quick conclusion might be that as traffic dangers increase due to volume, the likelihood increases that non-ADS-B planes will get a traffic signal, thus reducing their risk.

Sounds like a Stratus may be worth the investment for those of us who fly non ADS-B out aircraft some of the time or all of the time.
 
Bob,
I do not have a Stratus but a flying buddy of mine does. I have a SkyGaurd TWX UAT which has both ADS-B out and receives on the 978 and 1030 frequencies. We flew to Columbus IN this past Friday and, with him in his Archer and me in my Arrow. As long as my ADS-B is working he gets traffic on his Stratus/Foreflight setup.

The issue I am working through right now is that it comes and goes. I had traffic for 5 minutes then I would loose it for 4 minutes. Then it would come back and so on.

i am working with the SkyGaurd people to try to figure out if it is a problem with my unit or the ground xmtr or was I flying in a fringe area that was not always receiving my signal. He did confirm that every time I was loosing traffic he also lost it.

I will let yo know more when I have it.

I have had a few get a bit testy about traffic saying I need to keep my head outside the cockpit and not be looking at a display for traffic. I completely agree with that statement, but the display gives me a direction, distance, altitude and path long before ATC does. It is a lot easier to find traffic and figure out which way to turn if I need to.

FYI, SkyGaurd does sell a stand alone ADS-B out that would turn the station on so you can receive traffic on your Stratus.
 
VWGhiaBob said:
I'd be interested if there are folks out there without ADS-B Out who have tried the stratus. When you fly in really busy areas, is the traffic information useful and complete most of the time?
Click to expand...

We have a Stratus II in our club 182 and operate around D/FW's Bravo airspace (we are based at KDTO).

I am not seeing that many traffic symbols being shown to me, and I attribute that to very few aircraft equipped with ADS-B out to trigger the tower to broadcast the traffic. And I have been close to other traffic (within 1 mile radius) that I or a passenger spotted that did not show up on the iPad.

I have also used it on a trip from KDTO to KSGR (near Houston). North of College Station, I saw a few tags on the iPad for traffic. One must have been an aircraft with ADS-B out equipment since I did see his tail# and later ATC advised him of some traffic near to him. But some of the other targets (that were actually closer to me) never moved and the arrow appeared to just twist and point different directions.

Summarizing; the Stratus ADS-B receiver does work as designed and works well. But don't rely on it as a sole solution for traffic until you have ADS-B out equipment on your own aircraft. You will NOT see the aircraft that's getting too close for your comfort.

IMO, Best solution remains being on Flight Following with ATC.
 
I have a GDL-39. Without the out signal, you will see a lot of 1090 traffic (airlines) and infrequently a TIS-B UAT target. There are not a lot of people flying around with ADS-B out yet. Even in my heavy traffic area around Philly, I rarely see UAT targets.

As Tim mentions, the SkyGuard TWX is an interim solution to a panel mounted solution. I know Don, the owner of the company is seeking out FAA approval on the unit. I have friends who fly with it using Stratus and GDL-39 antenna and it works as advertised. Just a little pricey at $975 for a portable solution.
 
I thought he was down around $650 for the xmit but I see it is up to $975 and yes that is a bit pricey.
I got the UAT without AHRS for $1300
 
Marauder said:
As Tim mentions, the SkyGuard TWX is an interim solution to a panel mounted solution. I know Don, the owner of the company is seeking out FAA approval on the unit. I have friends who fly with it using Stratus and GDL-39 antenna and it works as advertised. Just a little pricey at $975 for a portable solution.
Click to expand...

What approval is needed?

And I agree on the price point.
 
Chris may have more information but I recently spoke with One of the owners from Adventure Pilot (iFly) that is working closely with Don and I think the only point to get past now is the GPS Puck. The FAA wants to know how the GPS Puck will be mounted permanently and where, since the Puck is not an antenna but is the whole GPS unit.

I understand that once Don has TSO approval he will sell a kit to permanently mount the unit in an aircraft.

Legally the unit broadcasts as a portable and that is ok till the 2020 mandated deadline happens. If if does not have FAA approval by then it will have to be shut off.

I will be talking to Don on the phone later today and will pass on any tidbits he avails me of.
 
Getting a portable solution approved will be a challenge. Since the box produces an outbound signal, interference with onboard electronics will need to be proved not to be occuring.

I wish him well. We need competition to help keep prices in check.
 
tmyers said:
Chris may have more information but I recently spoke with One of the owners from Adventure Pilot (iFly) that is working closely with Don and I think the only point to get past now is the GPS Puck. The FAA wants to know how the GPS Puck will be mounted permanently and where, since the Puck is not an antenna but is the whole GPS unit.

I understand that once Don has TSO approval he will sell a kit to permanently mount the unit in an aircraft.

Legally the unit broadcasts as a portable and that is ok till the 2020 mandated deadline happens. If if does not have FAA approval by then it will have to be shut off.

I will be talking to Don on the phone later today and will pass on any tidbits he avails me of.
Click to expand...

Tim -- when you are speaking with him, can you ask what happens if you do not change the transponder code via his ap? As an example, let's say I am flying IFR with a 4224 squak code. I understand I enter that into the SkyGuard via the app. What happens if I forget to change it to VFR (1200)? Do I create a traffic conflict with myself and/or ATC?
 
I only see this working if low cost antenna can be used for the signal out and a way to get a GPS puck outside the aircraft as well. Both are needed to give the FAA a good fix for the aircraft. There is however the GPS vs Pressure Alt issue.

Exterior antenna will be the best way to guarantee good signals.
 
Maybe I'm slow today, but ADS-B out only transmits information - there is no receive path in a system that only provide ADS-B out.

what am I missing here?
 
The concern I have is the signal download. One of my buddies who has it working with his Stratus said that it was causing Comm problems. He relocated it to the back of the plane and it has been working fine.

I think he is transmitting somewhere around 30 watts.
 
I don't think your missing anything Bob, the out signal from an aircraft is like the occupant sensor that turns on the lights in your office. The out signal turns on the ground transmitter that broadcasts the traffic ATC is seeing.
 
Marauder said:
The concern I have is the signal download. One of my buddies who has it working with his Stratus said that it was causing Comm problems. He relocated it to the back of the plane and it has been working fine.

I think he is transmitting somewhere around 30 watts.
Click to expand...

Yep, 30 watts is correct. My plan is to move it back to the hat rack and purchase the blade antenna for xmit and 978 rcv. I get a constant pop pop pop in my headsets and radio with the xmit antenna on the glare sheild
 
Bob Noel said:
Maybe I'm slow today, but ADS-B out only transmits information - there is no receive path in a system that only provide ADS-B out.

what am I missing here?
Click to expand...

I don't think you are missing anything. It is transmitting out only. But it does have a WAAS GPS in it to collect the position data and the unit also accepts a squawk code to transmit with the signal.

Tim is talking about the placement of the required WAAS antenna and I am asking about the transmitter antenna.
 
Bob Noel said:
Maybe I'm slow today, but ADS-B out only transmits information - there is no receive path in a system that only provide ADS-B out.

what am I missing here?
Click to expand...

We started the thread talking about how to get traffic up into our aircraft with the Stratus II. (ADS-B in)

And now have evolved into talking about solutions for our aircraft to trigger the traffic broadcast with a device for the ADSB-out.
 
tmyers said:
Yep, 30 watts is correct. My plan is to move it back to the hat rack and purchase the blade antenna for xmit and 978 rcv. I get a constant pop pop pop in my headsets and radio with the xmit antenna on the glare sheild
Click to expand...

And if that is anything that will give him issues with certification is the verification that it does not cause interference. I wonder if he does get it approved that there will be requirements on where to install the hardware.

Let us know how he is doing on this. I applaud his effort. See if you can get him to lower his price for us! :D At $699, I would buy today...
 
Book states to keep the xmit antenna at least 18" from the GPS Puck and 8" away from your body. I am thinking a xmit antenna on the belly under the hatrack and a clear dome above that same area for the GPS Puck would be the ticket, but time will tell.
 
Without ADS-B Out, traffic on a portable unit is next to useless. It is not totally useless, just next to it, as any traffic one observes on the portable could be a potential threat, that is of course, unless the traffic is own ship or an airliner 30 thousand feet above. What it doesn't show could ruin your day. Assuming you have a dual frequency receiver, the likelihood of being inside a "hockey puck" of a participating aircraft and observing TISB traffic of a third party aircraft that is a collision threat is way overrated. Remember, you can already see the participating aircraft, it is the other non participating aircraft that must be in a hockey puck near enough to your aircraft trajectory to present a threat.
 
John Collins said:
Without ADS-B Out, traffic on a portable unit is next to useless. It is not totally useless, just next to it, as any traffic one observes on the portable could be a potential threat, that is of course, unless the traffic is own ship or an airliner 30 thousand feet above. What it doesn't show could ruin your day. Assuming you have a dual frequency receiver, the likelihood of being inside a "hockey puck" of a participating aircraft and observing TISB traffic of a third party aircraft that is a collision threat is way overrated. Remember, you can already see the participating aircraft, it is the other non participating aircraft that must be in a hockey puck near enough to your aircraft trajectory to present a threat.
Click to expand...

Absolutely correct. Hence the discussion we are having on portable "out" solutions. The "traffic" picture below was taken right after a small plane passed directly over me. Never saw him coming towards me, only saw a shadow and the blur as went from above in my 2 o'clock position to descending below me in my 8 o'clock position.

My "in" only solution showed nothing in the vicinity. It made me :sad:
 

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I think Don and I have narrowed the problem with my transmitter to the antenna. My unit arrived with an old antenna that he no longer provides so he is sending a new one to me to try out. All the discussion points to a transmit issue and the antenna is the weak link in this scenario.

We discussed at length the TSO process and what may or may not need to be done.

I also put a bug in his ear that the word around town is that he is asking too much for his ADS-B out unit and that it should be $700 or less.

I will let you know what he tells me.
 
tmyers said:
I think Don and I have narrowed the problem with my transmitter to the antenna. My unit arrived with an old antenna that he no longer provides so he is sending a new one to me to try out. All the discussion points to a transmit issue and the antenna is the weak link in this scenario.

We discussed at length the TSO process and what may or may not need to be done.

I also put a bug in his ear that the word around town is that he is asking too much for his ADS-B out unit and that it should be $700 or less.

I will let you know what he tells me.
Click to expand...

He gets it into that price range, I'll buy. Thanks for asking...
 
I guess I'll try clarifying.

If you have an ADS-B traffic receiver (GDL-39 for example), you will get two types of traffic:
  1. ADS-B traffic from another airplane that has ADS-B "out" and is broadcasting it's position.
  2. ADS-R (Rebroadcast) traffic from a ground station that is uploading the traffic data from the system fed by both ADS-B aircraft and the surveillance radar.

However, the ADS-R feed is only triggered when the ground station receives an ADS-B "out" broadcast from an aircraft, and it replies with traffic data of interest to that target.

So if I'm flying along with my Nexus7 and GDL-39, and that's the ONLY ADS-B equipment I've got, I'll only see:
  1. Traffic from broadcasting airplanes nearby with ADS-B "out"
  2. ADS-R traffic broadcast from the ground to airplanes near to me that have ADS-B "out". And depending on how far away they are, that traffic broadcast to them may not include other airplanes near me.
That's better than nothing, but it's nowhere near as good as if I had ADS-B "out" on my airplane.
 
Tim,

You are close, but you have a terminology problem. ADS-R is a GBT service used only to glue together the two links. Both aircraft involved have to have ADS-B Out, but be on opposite links. The R stands for Rebroadcast. If an aircraft has a dual frequency receiver, ADS-R is redundant as the receiver should receive both frequencies air to air. In theory, if an aircraft reports its "In" capability to be either both or neither, ADS-R need not be generated. ADS-R also has a thicker hockey puck when it is broadcast, +/- 5000 feet.

TIS-B is what you were describing. This is a GBT service based on a mode C transponder return of an aircraft that does not have ADS-B Out installed. Since the target aircraft doesn't generate an ADS-B broadcast, it is invisible to a client aircraft unless the GBT broadcasts a TIS-B message. The TIS-B broadcast is only generated when a mode C radar target is within the hockey puck of a client. Since any aircraft with a dual frequency receiver (or has one of the same frequency as the TIS-B ) can receive the broadcast as long as the aircraft is within line of sight of the GBT. At altitude, this could be over a 100 NM. However, the TIS-B broadcast is only useful if it points out a threat to your aircraft, which means two things, both you, the client, and the other mode C target have to be near one another. That is three aircraft in the same area. It doesn't cover the area around your aircraft, but rather the area around the client.

Some examples that won't do you much good, you are 3000 feet directly above the client, making the same speed and direction, but the target is above you. You are each going at 180 Kts in the opposite direction and the client is 10 NM behind you, but the target is 15.5 NM from the client in the same direction as the client and at your altitude. So sorry. The point is that it will offer very little relief from collision with three aircraft in up to three different speeds, altitudes, rates of climb or descent, and directions with only a short period of time where a collision threat that wasn't already know to you will become visible to assist you with detection and avoidance.

I am not saying you won't see a lot of irrelevant traffic, you will, particularly with a dual frequency receiver, because these signals are line of sight. But if you think that it substantially improves your traffic awareness, this is a pipe dream. With ADS-B Out, it is a very good service.
 
In simple terms, you will not see traffic next to you unless you are ADS-B out equipped. Without ADS-B out you will see traffic far away but will not know if you are clear of traffic or on a head on collision.

Any ADS-B out equipment 1090MHz or 978MHz must be FAA TSO approved. There is no such thing as portable ADS-B out. Don't waste your money on non-approved equipment.

José
 
Piloto said:
In simple terms, you will not see traffic next to you unless you are ADS-B out equipped. Without ADS-B out you will see traffic far away but will not know if you are clear of traffic or on a head on collision.

Any ADS-B out equipment 1090MHz or 978MHz must be FAA TSO approved. There is no such thing as portable ADS-B out. Don't waste your money on non-approved equipment.

José
Click to expand...

José - the SkyGuard TWX is a portable solution and it does perform an "out" function. It's just not TSOd at this point and may never be. So, is it better to spend your time looking out the window and trusting in the big sky theory or is it better to have a non approved solution that does work?

I have seen enough of your posts to know you are not a supporter of anything less than a fully certified traffic system. That's fine. It's your opinion based on your experience. Unfortunately, those systems are out of the financial reach for most owners and certainly not available to renters. I have seen enough of Brett's experience (over at MooneySpace) with his SkyGuard equipment to know that it is a much better solution than no solution.
 
The portable solution is perfectly legal at this time. If it does not become TSO certified by 2020 it will have to be turned off. That gives the developers 6 years to get the issues resolved.
 
VWGhiaBob said:
I'd be interested if there are folks out there without ADS-B Out who have tried the stratus. When you fly in really busy areas, is the traffic information useful and complete most of the time?
Click to expand...

Not so much. The only time I've ever seen traffic right in my area reliably was down around Daytona Beach, where all of the Embry-Riddle planes are triggering the TIS-B traffic feed showing other traffic as well.

Otherwise, it's been pretty hit or miss so far. Certainly not something to rely upon, and it never will be until you get your own ADS-B Out installed.
 
flyingcheesehead said:
Not so much. The only time I've ever seen traffic right in my area reliably was down around Daytona Beach, where all of the Embry-Riddle planes are triggering the TIS-B traffic feed showing other traffic as well.

Otherwise, it's been pretty hit or miss so far. Certainly not something to rely upon, and it never will be until you get your own ADS-B Out installed.
Click to expand...

Even then, there will always be someone out there without a transponder on board...
 
I just hope that I am not EVER flying in the vicinity of some idiot with one of those rip off ADS-B traffic devices and NO ADS-B traffic out, because if they don't see me on their silly little traffic map and are blindly relying on it now we have just doubled the probability of a mid air collision.

Either do it properly, or not at all! Put down the toys and look outside the window please.
 
Agreed, that's why I bought the ADS-B out, even if it is only useable for the next 6 years.
 
I have a DIY 1090 receiver and it shows only targets high up (at 33000 ft). Why is that? Airliners suddenly stop broadcasting Mode S when they descend?
 
John Collins said:
Without ADS-B Out, traffic on a portable unit is next to useless.
Click to expand...

I've had pretty good luck with my sporty's stratus unit. Yeah, it does NOT catch everything. But anything that does show up on there, is very accurate.

I also find that in busy, high traffic areas there is typically someone with an ADS-B out in the area and I get pretty much all of the traffic. For example I was at MBT last week, they have a busy flight school. At one point on the ground I could track four airplanes visually in the pattern, and they all showed up in their exact positions on my ipad. I could see them turning base, final and dropping off the screen at about 400 AGL.

Some traffic is better than no traffic.
 
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