How frequently does ADS-out transmit? In/Out confusion?

[TomCC]

This type of question has probably been asked many times. I've spent hours searching trying to find the answers to this and other questions but am left wanting for an answer. I'm sorry if this is a FAQ...

Example scenario:
If I install a KT74 ADS-B "out" transponder and couple it to an approved WAAS source (thus 2020 compliant), and I then simultaneously utilize an ADS-B "in" receiver (any of the mobile types), can I rest assured that my KT74 will be "pinging" any surrounding ADS-out traffic and that such traffic will reliably show up on my ADS-B receiver and displayed on my Ipad app? For those familiar with the GDL-88 in/out, would the above equipment essentially give me the same functional utility?

In the above scenario, would my mobile receiver forever be showing my KT74 signal as a phantom on my screen?

 

[kontiki]

Is it a UAT or a 1090ES transponder? If it's Mode S transponder the broadcast is called a squitter and it transmits at pseudo random intervals (from memory) somewhere between 1/4 and 1 sec.

FARs generally point to a TSO for hardware requirements and may specify some additional performance requirements. The TSO points to Minimum Operational Performance Standards (MOPS) and/or Minimum Aviation System Performance Standards (MASPS) which are usually RTCA documents for US. ICAO uses EUROCAE and I don't know if there are others.

I know for a fact Mode S squitter intervals are listed in DO-181 or DO-260 depending on ADS-B or not because I've looked them up before.

There are separate standards for UAT, I haven't looked into UAT at all.

You probably won't find any copies of RTCA specifications laying around the internet. They are extremely protective of their IP. You can purchase any of their specs though.

 

[Henning]

This type of question has probably been asked many times. I've spent hours searching trying to find the answers to this and other questions but am left wanting for an answer. I'm sorry if this is a FAQ...

Example scenario:
If I install a KT74 ADS-B "out" transponder and couple it to an approved WAAS source (thus 2020 compliant), and I then simultaneously utilize an ADS-B "in" receiver (any of the mobile types), can I rest assured that my KT74 will be "pinging" any surrounding ADS-out traffic and that such traffic will reliably show up on my ADS-B receiver and displayed on my Ipad app? For those familiar with the GDL-88 in/out, would the above equipment essentially give me the same functional utility?

In the above scenario, would my mobile receiver forever be showing my KT74 signal as a phantom on my screen?

I'm pretty sure I get what you are getting at in that you think the 1090 transponder will activate to reporting on other transponders, and you hope that the UAT system will see that reporting, and I believe the answer is "Yes, it will see that." You are worried that there is a critical timing involved between the 'ping' and the receptio, that is not my limited understanding of it.

 

[chartbundle]

In the above scenario, would my mobile receiver forever be showing my KT74 signal as a phantom on my screen?

At least the GDL39 is smart enough to report your 'ownship' position in its datastream. I assume it compares location, speed and altitude between the data it receives and its internal GPS and uses it to remove yourself from the picture. I'd have to assume that any ADS-B in solution not integrated with the ADS-B out would have the same type of ownship removal.

But one other note, ADS-B out is not a query to other traffic, it simply transmits in the blind as will any other ADS-B equipped traffic. What it will do is tell the ADS ground stations that an ADS-B out equipped aircraft is in the area and it should retransmit any non-ADS-B out targets(TIS-B) it has received from radar.

 

[Pedals2Paddles]

My understanding is as above. Your ADS-B OUT will always be transmitting at it's regular interval. It doesn't require there to be radar or other aircraft nearby to do so. It just flies around broadcasting itself. Other aircraft with ADS-B OUT are doing the same thing.

Your ADS-B IN receiver will hear all of those other aircraft with ADS-B OUT. You don't need to ask in order to receive air-to-air ADS-B. Aircraft are always broadcasting it and you will always pick them up.

If you want to receiver the TIS-B from ground towers, that would indeed require you to have ADS-B OUT. The ground towers for TIS-B will not transmit anything without an applicable ADS-B OUT aircraft within range. Furthermore, TIS-B ground towers will only transmit traffic data for a 15 mile and 3000ft radius around an ADS-B OUT aircraft.

So you, having ADS-B OUT, will receive a complete picture of all identified traffic around you. It will be a combination of traffic received directly from other ADS-B OUT equipped aircraft, and full TIS-B data. TIS-B includes all known traffic in that bubble around you. Both ADS-B and ATC radar traffic piped in from radar facilities.

 

[John Collins]

Example scenario:
If I install a KT74 ADS-B "out" transponder and couple it to an approved WAAS source (thus 2020 compliant), and I then simultaneously utilize an ADS-B "in" receiver (any of the mobile types), can I rest assured that my KT74 will be "pinging" any surrounding ADS-out traffic and that such traffic will reliably show up on my ADS-B receiver and displayed on my Ipad app? For those familiar with the GDL-88 in/out, would the above equipment essentially give me the same functional utility?

In the above scenario, would my mobile receiver forever be showing my KT74 signal as a phantom on my screen?

A few basics, your ES transponder will be continuously broadcasting the aircraft position on a regular basis, approximately twice per second. These broadcasts are transmitted along with other types of data such as velocity, identification, and status information, with a total rate close to 5 or 6 transmissions per second. These transmissions are in addition to replies to ground radars and TCAS inquiries. Your ADS-B Out is a broadcast, there is no concept of pinging another unit.

Your ADS-B portable receiver will pass along all of the broadcasts it receives to the iPad application. The iPad application will have to determine through an algorithm which broadcasts are close enough to its GPS position and thus represent the own ship broadcasts. It can then filter them out from being a target. A good algorithm will not show your own ship to be a ghost target. The more likely source of a ghost is from a distant radar feeding your position to a GBT (Ground Based Transceiver). With the positions close but not close enough, the GBT may think there are two targets, the precise one generated by your KT74 position source and the imprecise ground radar. Thus the GBT will send your ghost position as a TISB target. This can wake you up, with this blaring in your headset: "Traffic 12 o'clock, same altitude, less than a mile".

The GDL88 and the 1090ES will give the same results with respect to your portable system. I have both a Stratus/iPad/ForeFlight and a GDL88 and for the most part work great. I did have a ghost on my recent trip back from Oshkosh that stayed with me for about 15 minutes, fortunately I also have a mute switch that suppresses the target alerting if it remains the same target.

 

[winrose46]

For the most part it has worked very well with one ghost that went on a divergent path for at least 15 miles and the controller told me there was nothing on my right for more than 20 miles. The other situation was overflying BWI and a 737 and a lear climbed past me on my left from the airport and while I had a visual they never appeared on the GDL 88 Garmin 430 interface or on my iPad or iPad mini. The other instance was going into KGON and a passenger plane was above and passed me on my left without appearing on any of my displays. Most of the time (99%), I see the aircraft before the controller calls the traffic or I can not see the traffic being displayed. That is 4 targets with some sort of malfunction in more than 40 hours of ADS_B Out flying in the past three months. I would not hesitate to fly VFR cross country without radar following which is something I would never have said without ADS_B Out being installed in my plane.