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ADS-B technology and compatibility (merged thread)

Iridium to capture ADS-B data from space


One has to smile at the infinite ingenuity of mankind when it comes to inventing new ways to make money by grabbing something already "around" and selling it

You can already receive ADS-B from all over Europe with just one receiver located in the middle of Europe, so this must be for stuff like oceanic and other remote-region traffic.

Shoreham EGKA, United Kingdom

I’m just in the process of having my AFMS changed (updated) to reflect the latest Garmin STC approving my avionics fit for P-RNAV. My original application to the FAA for a P-RNAV LOA was rejected because the original 2010 AFMS was just before the latest STC and software (suffix D required).
As a consequence of finding all this out my avionics guy in Denver said “and you need another LOA if we connect up your GNS430W’s, update to software version 5, and connect them to the ES transponder for ADS-B out”.
Look in AC90-114 Appendix 1 Clause 2.
My attitude to both P-RNAV and ADS-B is it costs me very little to achieve both as I have an avionics fit capable of both so why not. The LOA’s are now a challenge not a real need so I will persevere. I’m near to the P-RNAV LOA re-application, early days for ADS-B.
ADS-B is not so stupid for me. My strip at home is shadowed from my local airport EGNS by high hills so I loose them two miles out. They have recently set up some secondary radar stations (boosters/routers) around the island so they can see all transponders and I was astonished to hear they are ADS-B in and out compatible, but that aspect is turned off. They could easily turn it on apparently so they can watch me down to my strip and see all the data involved. Is this a real practical advantage, I guess not? But as it won’t cost me much or them we should have a got. I’ll need the ADB-B LOA first, this could take time and tenacity.

EGNS/Garey Airstrip, Isle of Man

I think the ADB-B LoA is very silly but it seems like they want it so aircraft are able to do the In trail Procedures and the like. Obviously very unlikely GA aircraft will be leapfrogging a 737. I think you are at very limited risk in turning on ADS-B out. But as you say while you are looking for PRNAV you might as well ask for both.

EGTK Oxford

I would not worry at all about radiating all this stuff. The regs are meaningless in practice.

It already happens with every non-European (particularly US based) GA aircraft entering European airspace. Most of them will have something like a GTX330 with a GPS feeding it data via RS232 or ARINC429 and the GTX330 will just radiate the whole lot – lat/long, GPS data, the tail number, etc. If you fly say an SR22 here with the original Cirrus Avidyne glass and the TAS6xx gear connected via the RS232 interface, you see the tail numbers for most N-regs displayed on the TCAS (nice). With MFDs that get the TCAS data over ARINC429 (e.g. G500, G1000, my KMD550) the TAS6xx does not transmit the tail number (I did ask if there is a hack but there isn’t).

The reason is that Elementary Mode S versus Enhanced Mode S is a purely European invention which is not supported by the principal US avionics makers. It’s a bit like Eurocontrol dictating that the Apollo Lunar Module should be RNP compliant. So any US aircraft will be radiating what amounts to some subset (or superset ) of Enhanced Mode S anyway. Some European ones are doing this too

Similarly with ADS-B. I would expect any US-originating modern-equipped N-reg plane to be radiating ADS-B via its GTX330 or whatever. There is a fair bit of discussion of ADS-B on the US forums – I don’t follow it closely but it sounds like it will be mandatory over there eventually, or (like European Mode S is now) it may be mandatory for practical purposes.

Last Edited by Peter at 17 Jan 13:21
Shoreham EGKA, United Kingdom

There is a fair bit of discussion of ADS-B on the US forums – I don’t follow it closely but it sounds like it will be mandatory over there eventually, or (like European Mode S is now) it may be mandatory for practical purposes.

Only in congested areas of the US, mainly on the coasts. ADS-B Out (note Out only) is scheduled to be mandatory in 2020 in the airspace areas where Mode C transponders are currently required. That means around 35 US airports airports with Class B (Mode C Veil) airspace and 122 with Class C airspace, plus over 10,000 ft and one geographic area where drug trafficking is common. However, most US airspace, including Class D airspace (associated with most ATC controlled airports) and Class E airspace will continue to require no transponder or ADS-B. Details here…

I’ll likely still be flying a non-transponder, non-ADS-B aircraft within Mode C veils quite often, as aircraft with no engine driven electrical system will continue to be exempt except in Class B and C airspace itself. The aircraft is based at a Class D ATC controlled airport within a Mode C veil that will become subject to the ADS-B Out requirement. It has one handheld radio.

Last Edited by Silvaire at 17 Jan 15:36

ADS-B compliance in the US will be pretty high, but not as high as a transponder. We use two separate frequencies, 1090 MHz and 978 MHz. The latter is called UAT and offers more features for the GA pilot. Above 18,000 MSL, 1090ES will be required, so airliners and aircraft that fly at or above these altitudes will require the ES but can also have the UAT. A defacto standard is evolving for dual frequency ADS-B In avionics in the US. ADS-B Out will be split between the two technologies. In my Bonanza, I have a GNS530W as a position source. I also have a GTX330 but it is not upgraded to ES as that provides me no benefit. I installed a UAT GDL88 that has UAT ADS-B Out and a dual frequency In. I get free weather and traffic with this combination for about half the cost of an active TCAD system. There are no international mandates for low level flight, so I won’t need to upgrade my GTX330 to ES. The GTX330 is EHS capable, but only a glass cockpit will have the required inputs to be considered EHS (example selected altitude).

I did some flight testing with Jason Miller, Cofounder of ForeFlight LLC. He has a 2010 SR22TN with the G1000 Perspective and an Avidyne 610 TCAD. He upgraded his GTX33 to ES. He doesn’t trust the Avidyne after flight testing when comparing it with his Stratus 2 traffic as the Azimuth does funny things and the target (my Bonanza) occasionally was dropped from his traffic screen. The Stratus 2 never lost my UAT Out position.

KUZA, United States

radiate the whole lot … the tail number

Unlikely. The reason the tail number is displayed for N regs is likely because the algorithm for computing the tail number from the Mode-S address is known. It’s also known for HB and other countries (but unlikely US avionics companies bother to implement it), but for G reg and D reg, there’s no algorithm (for “privacy”), you need a database.

LSZK, Switzerland

Yes – exactly. That is what the Avidyne TAS boxes appear to be doing.

The problem is that Avidyne make this available only on the RS232 data which is a proprietary data stream for driving Avidyne MFDs.

I didn’t wish to imply that only N-regs are visible. What I meant was that it was only Avidyne MFDs fed via their proprietary RS232 stream which display any tail numbers at all.

Actually one could decode any tail number if one could be bothered. The spotter products such as the Kinetic SBS-3 do it. You just need a database lookup. They must have grabbed the public Mode S ID databases such as that on G-INFO. I often wondered if ATC have that capability but apparently not in most cases. I know London Control have it for airline traffic, but reportedly it is suppressed for GA (possibly suppressed for targets which are presumed Elementary Mode S … who knows).

Shoreham EGKA, United Kingdom

ADS-B OUT for homebuilts

I was taking to one owner today.

He has a Mode S transponder (not Garmin but I forgot the name) and when I asked him what he will be using as the position source for it, he said it will be a POWERFLARM box which contains a GPS.

Impressive, considering the tight restrictions on ADS-B equipment in certified aircraft, and what kind of GPS can be used as the “approved” position source!

It also occurred to me that if/when ADS-B becomes mandatory (for IFR, say) then if only a WAAS GPS is an approved position source, that will force the installation of an RNAV1 GPS (loads of €€€€, for many owners) even before any RNAV1/PRNAV airspace mandates…

Shoreham EGKA, United Kingdom


I’m not surprised. When I asked Becker about ADS-B using the BXP64xx, they knew it would take NMEA but never heard about “aviation format”.

Very likely this installation transmits NIC/NACp 0, meaning no known containment radius. While this is likely fine for collision warning purposes, it’s not enough to fulfill the FAA mandate (which requires NACp at least 7, I think).

LSZK, Switzerland
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