OK, here is what I object to on a sentence by sentence basis.
Government installing infrastructure to routinely track the movement of citizens is not an easily defensible moral position.
Tracking the movement of citizens is not the issue. An aircraft is uniquely tracked in either case for the purpose of ATC surveillance and separation between such an aircraft and other aircraft that are being controlled by ATC.
ADS-B Out being mandatory in some areas would never have passed scrutiny in the US if there wasn’t a way to turn off identity reporting when outside of those areas.
This is not true. There is no way to turn off identity of the aircraft for those equipped with 1090ES. The same is true of standard mode S transponders. Where flying in airspace where not being in contact with ATC is permitted, but where ADS-B Out is mandated, the UAT can use anonymous mode. For example, under or over a class C or B airspace, inside the 30 NM mode C veil, above 10,000 MSL are airspace that the ADS-B Out is mandated, yet in these areas anonymous mode is permitted as long as the aircraft is VFR and squawking 1200. The point is that there is no distinction between airspace that doesn’t require the use of ADS-B Out and much of the airspace that does require it, as anonymous mode is useful in either.
What annoys me is reading the regulation to become effective in 2020, which requires the system start automatically with ID on and require pilot action to shut it off.
There is no such regulation. 91.225 specifies what equipment is required and where it must be used. It lists certain exceptions for aircraft that don’t have an electrical system. It requires that such equipment, if installed, to be operating at all times. There is no direct reference to anonymous mode anywhere in 91.225. 91.227 specifies what must be broadcast and includes: An indication of the aircraft’s call sign that is submitted on the flight plan, or the aircraft’s registration number, except when the pilot has not filed a flight plan, has not requested ATC services, and is using a TSO-C154c self-assigned temporary 24-bit address.
These are all the same rehashed issues that stopped Mode S in any significant sense for private aircraft in the US.
Not true. Most current production GA aircraft come standard with mode S. Mode S GTX330ES was a very popular upgrade in the US because of the Traffic TIS feature. I installed mine for this very reason. It was sort of a poor man’s traffic system. There are probably 30 thousand of these units installed. The Trig and its OEM variants are very popular as well in the US. It is the relatively low cost of ADS-B upgrade for aircraft owners that already have mode S transponders installed that is inducing so many aircraft owners to go the 1090ES route rather than the UAT route. Cost of upgrade trumps the perceived need for anonymity.
The difference now is that the new law allows a tiny sliver of untracked movement, the very least I think the bureaucracy could get away with, and requiring pilot action to turn it off, not on.
Prior to ADS-B, a mode A/C transponder did not reveal the N number. With UAT, this is preserved. Most pilots don’t consider this a big deal as part of the technology selection for ADS-B, but it is available to them if they choose UAT and keep a mode A/C transponder. Some installations use a switch to activate or deactivate anonymous mode. It can be left in either position and will automatically select anonymous mode when 1200 is set into the transponder. Most VFR aircraft leave 1200 in the transponder at all times they are not interacting with ATC. Exactly what action is required of the pilot that you refer to.
NCYankee, here are a few responses to your new points that weren’t addressed by me before…
Tracking the movement of citizens is not the issue. An aircraft is uniquely tracked in either case for the purpose of ATC surveillance and separation between such an aircraft and other aircraft that are being controlled by ATC.
I disagree, and I think the long term agenda for any of these tracking technologies (for some parties, certainly not all) is automated billing per mile for use of airspace. It certainly makes that a great deal easier. Therefore it is key (to me) that there be a pilot selected option to turn off identity reporting, because it makes automated billing for use of the airspace impractical. You are certainly free to disagree that this long term motivation exists, although I think anybody with a brain can see the potential implication.
There is no way to turn off identity of the aircraft for those equipped with 1090ES.
I was talking about the FAA ADS-B Out mandate and how an individual could comply. UAT based ADS-B Out is one way to comply, and by choosing UAT for his plane the individual can turn off transmission of his identity when desired. Whether another ADS-B system does not have that option is totally irrelevant, the UAT option exists.
These are all the same rehashed issues that stopped Mode S in any significant sense for private aircraft in the US. (quote from Silvaire)
Not true. Most current production GA aircraft come standard with mode S. (NCYankee response)
Given that most of the GA fleet is not in current production, and also that most GA aircraft don’t have Mode S, and also that its required nowhere below 18,000 feet within the US my point of view is that Mode S is not a significant factor in US GA operations. That is especially true with with ADS-B now coming into play. I understand that Mode S can optionally be a component within ADS-B but I think the implementation of Mode S was dealt a death blow in the US when it was made optional years ago, after debate.
It is the relatively low cost of ADS-B upgrade for aircraft owners that already have mode S transponders installed that is inducing so many aircraft owners to go the 1090ES route rather than the UAT route. Cost of upgrade trumps the perceived need for anonymity.
Perhaps in ‘your world’, the number of US aircraft that have existing Mode S transponders is significant, in ‘my world’ the number of aircraft with existing Mode S transponders it is essentially zero. I think my world is bigger than your world 
Prior to ADS-B, a mode A/C transponder did not reveal the N number. With UAT, this is preserved. Most pilots don’t consider this a big deal as part of the technology selection for ADS-B, but it is available to them if they choose UAT and keep a mode A/C transponder. Some installations use a switch to activate or deactivate anonymous mode. It can be left in either position and will automatically select anonymous mode when 1200 is set into the transponder. Most VFR aircraft leave 1200 in the transponder at all times they are not interacting with ATC. Exactly what action is required of the pilot that you refer to.
All that is clear, except that I think many pilots think its a big deal. You are again free to disagree. Obviously, the required pilot action is moving the switch to maintain anonymity. The FAA ADS-B Out regulation (which I have read) as I understood it requires that the design of the system (1) start up in a mode to report identity and (2) require the pilot to select non-identity reporting mode after start up if he wishes to report only position and not report identity. I would prefer if both items were not so and if my interpretation is incorrect, I’ll be happy to hear it.
Just to clarify, NCYankee, may I ask if you have a financial interest in avionics installation? Thanks much.
The other up-and-coming issue is how GA will fit in with drones, when they become ubiquitous. Mandatory Mode-S would presumably make it easier to integrate them with other air traffic.
Hello dear forum members,
Lately, I invested in the flight radar app for my smartphone out of curiosity.
I’been browsing it for a couple of days and wondering how the aircraft position was acquired. I understand that liners are equipped with ADS-B. From time to time I see bunch of gliders appear and after a few google searches found out that they are using a so-called “FLARM” (Flight Alarm) system to broadcast their position and altitudes.
But more surprisingly, I sometimes see GA aircraft pop out (not many of them), and not only upmarket ones (which I understand could be equipped with ADSB). Sometimes an old Maurane or a DR400 comes out.
Does anybody know why?
Thanks
Most likely multilateration. If a signal is received by at least 3 suitably equipped receivers, the position of the originator can be computed using time of flight of the signal.
It’s pretty well described here http://www.flightradar24.com/how-it-works – I’m running an ADS receiver at home and upload my data to FR24. As a thanks I get a free premium account (and provide great low level MLAT coverage and ground coverage at Sturup).
FR24 seems to keep GA tracks for only a short time, and which ones it keeps are random.
For example a URL like this shows stuff back a few days – example – but that’s unusual.
Is there any way to log the data, for say a trip writeup? One can get an alert on a smartphone (the paid-for FR24 app) but by the time one goes to the alert, usually after one has landed, the data is gone. This happens on every short flight I do too.
So there seem to be two operating modes in FR24: one where a flight is kept for a few days, and one where it is discarded (as far as the app and the website are concerned, anyway) immediately after landing.
My responses are in italics and embedded in your quote.
Silvaire wrote:
NCYankee, here are a few responses to your new points that weren’t addressed by me before…Tracking the movement of citizens is not the issue. An aircraft is uniquely tracked in either case for the purpose of ATC surveillance and separation between such an aircraft and other aircraft that are being controlled by ATC.
I disagree, and I think the long term agenda for any of these tracking technologies (for some parties, certainly not all) is automated billing per mile for use of airspace. It certainly makes that a great deal easier. Therefore it is key (to me) that there be a pilot selected option to turn off identity reporting, because it makes automated billing for use of the airspace impractical. You are certainly free to disagree that this long term motivation exists, although I think anybody with a brain can see the potential implication.
Since I have a brain, I certainly wouldn’t waste my time with a charging system that charges per mile when all I have to do is charge per year or per flight. Much simpler and doesn’t need a sophisticated collection system. After all, the rest of the world’s governments have had no difficulty charging for services without the need of ADS-B
There is no way to turn off identity of the aircraft for those equipped with 1090ES.
I was talking about the FAA ADS-B Out mandate and how an individual could comply. UAT based ADS-B Out is one way to comply, and by choosing UAT for his plane the individual can turn off transmission of his identity when desired. Whether another ADS-B system does not have that option is totally irrelevant, the UAT option exists.
It does exist in the US and even so, the statistics on adoption of ADS-B show that 1090ES is being adopted as the technology over UAT by a factor greater than 2 to 1.
These are all the same rehashed issues that stopped Mode S in any significant sense for private aircraft in the US. (quote from Silvaire)
Not true. Most current production GA aircraft come standard with mode S. (NCYankee response)Given that most of the GA fleet is not in current production, and also that most GA aircraft don’t have Mode S, and also that its required nowhere below 18,000 feet within the US my point of view is that Mode S is not a significant factor in US GA operations. That is especially true with with ADS-B now coming into play. I understand that Mode S can optionally be a component within ADS-B but I think the implementation of Mode S was dealt a death blow in the US when it was made optional years ago, after debate.
Your understanding of the US market is incorrect. Many GA aircraft decided to install Mode S transponders because in the US they could get a poor man’s version of a traffic system. The FAA 2013 Avionics equipage survey indicates that over 32,000 GA aircraft are equipped with mode S. This data is 2 years old and more GA aircraft have adopted mode S transponders such as the KT74 or Trig TT31 to satisfy the ADS-B Mandate. These aircraft do the bulk of the GA flying.
It is the relatively low cost of ADS-B upgrade for aircraft owners that already have mode S transponders installed that is inducing so many aircraft owners to go the 1090ES route rather than the UAT route. Cost of upgrade trumps the perceived need for anonymity.
Perhaps in ‘your world’, the number of US aircraft that have existing Mode S transponders is significant, in ‘my world’ the number of aircraft with existing Mode S transponders it is essentially zero. I think my world is bigger than your world
I assume you mean the lower end of the market has a smaller penetration of mode S, and that is certainly true. But I am in the $50K to $100K segment of the market and the penetration of mode S transponders, many of them inexpensive ($2500) is fairly common/
Prior to ADS-B, a mode A/C transponder did not reveal the N number. With UAT, this is preserved. Most pilots don’t consider this a big deal as part of the technology selection for ADS-B, but it is available to them if they choose UAT and keep a mode A/C transponder. Some installations use a switch to activate or deactivate anonymous mode. It can be left in either position and will automatically select anonymous mode when 1200 is set into the transponder. Most VFR aircraft leave 1200 in the transponder at all times they are not interacting with ATC. Exactly what action is required of the pilot that you refer to.
All that is clear, except that I think many pilots think its a big deal. You are again free to disagree. Obviously, the required pilot action is moving the switch to maintain anonymity. The FAA ADS-B Out regulation (which I have read) as I understood it requires that the design of the system (1) start up in a mode to report identity and (2) require the pilot to select non-identity reporting mode after start up if he wishes to report only position and not report identity. I would prefer if both items were not so and if my interpretation is incorrect, I’ll be happy to hear it.
That is not my understanding and I have obtained trace data from aircraft to demonstrate that, at least with a switch. Without a switch, I think the Garmins work as you say, but I am not positive. Regardless, avionics shops don’t usually discuss the anonymous feature with their customers when choosing or installing UAT systems. I find myself asking UAT owners if it is installed with anonymous mode and the vast majority have no idea what I am talking about. Many of the aircraft, for example mine, already had a mode S transponder installed when they add a UAT for ADS-B Out and with this combination, the UAT anonymous mode can’t be enabled as it would generate two addresses and two targets for ATC.
Just to clarify, NCYankee, may I ask if you have a financial interest in avionics installation? Thanks much
I have no financial interest in avionics installation other than in my own Bonanza.
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Peter, from my experience I concluded (rightly or wrongly) that it is only A-DSB tracks that are kept. Anything derived from triangulation or Flarm seems not to retained. Since you do not have A-DSB out I assume your position is calculated by triangulation, which would also fit with your position being lost whilst having radar coverage.
I can establish one data point: my flight Shoreham to Malmo has just dropped off the URL in my last post above.
That was on 22/7 so it looks like they keep them for 7 days.
And I don’t have ADS-B; only Elementary Mode S (only the 24-bit code and the aircraft reg gets emitted).
