What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

ADSB Anonymous Mode?

Two!

FWIW, browsing around, supposedly ATC will be eventually able to tag up your ADS- B anonymous 1200 VFR code symbol and see your ID.

Also, the "system" will store ALL tags and tracks in a searchable/reviewable format.

True/False?
 
Last edited:
I don’t think they can ever tell who you are if you are in anonymous mode. They go through quite a bit to generate an “almost” random ICAO. It involves taking the 12 least significant bits from both the lat and long of your current position adding that together, multiplying that by 4096 then exclusive “ORing” it with your ICAO (if available). If your assigned ICAO isn’t available it uses current time. So really you don’t even need an assigned ICAO to fly around in anonymous mode.
 
Last edited:
Are you sure about that? I think that all it suppresses is your N number; isn't the raw code of the ADSB unit (which is tied to your N number in the FAA database) still transmitted?
As I understand it anonymous mode transmits a random code. If the random code was tied to your “N” number and could be decifered we would know about it. One would have to assume that manufacturers such as Garmin would be complicit. Not ready to believe that.
 
Last edited:
It involves taking the 12 least significant bits from both the lat and long of your current position adding that together, multiplying that by 4096 then exclusive ?ORing? it with your ICAO (if available).
Very crypto-like.
 
Opinions are interesting / Facts are useful

As much as I respect the VAF braintrust, this thread leaves me cluleless. I have no intention of doing wrong, and share disdain for big brother. But, can somone identify themselves as having bottom line credentials on the topic and tell us the bottom line ?
 
I can say when a parameter wasn?t meeting spec on my navworx unit in anonymous mode, the FAA still called and knew exactly where to track me down to tell me it was out of spec. That confirmed it for me that it may be anonymous to other aircraft, but not to the FAA.
 
Two!

FWIW, browsing around, supposedly ATC will be eventually able to tag up your ADS- B anonymous 1200 VFR code symbol and see your ID.

From FreeFlight Systems' web site:

"How does 978 UAT do it differently? The 978 UAT rules allow for an ?anonymous? operating mode for aircraft flying VFR, and most avionics manufactures? equipment support this (but it?s advised to check first ? it is the manufacturer option to decides if they want to include this feature). If the option is available, it can be enabled during the installation. When the aircraft is on the ground and during the first few minutes of flight (so ATC can establish a track), the 978 UAT sends out the ICAO code and Flight ID. After that, as long as the squawk is set to ?1200,? the 978 UAT automatically scrambles those two fields using a random encoding scheme. ATC is able to maintain track, so you are safely ?in the system? but other aircraft and observers on the ground with receivers (like ?Flight Radar24?) loses all of the identifying info ? with no way to correlate it back to a specific aircraft or aircraft owner."

If this is correct then the anonymous mode really only prevents third parties from seeing your flight ID.
 
Thanks Timberwolf and Alan

So I conclude I can eliminate a "switch" on the panel for anonymous if the purpose is to keep big brother at arms length. That said, why would I care about third parties if the FAA has the data, if a serious accusation should arise ?
 
I followed Gunter's post and read the 68 page RTCA ADSB UAT document. Alan's reply was the info I alluded to earlier.

Free, link below, if you are over-caffinated

https://www.google.com/url?sa=t&sou...Vaw3JGdinXk5kxkHBYzcj_8CO&cshid=1550418096139

It has the schemes for all the data segments.

While the ICAO number is able to be anonomized "self assigned temporary number"- your CALL SIGN or for most here, our N#/registration number field is always active.

So, NOT really anonymous from ATC/FAA and possibly the "how/why" is my conclusion.

I might play with "978dumps" from adsbexchange to do a D.H. level test.

Flightaware and other sites can decode/upload 978mhz UAT, but most only use 1090mhz feeds. As long as they use the ICAO number field, there is the anonymity, to that extent.

giphy.gif
 
So I conclude I can eliminate a "switch" on the panel for anonymous if the purpose is to keep big brother at arms length. That said, why would I care about third parties if the FAA has the data, if a serious accusation should arise ?

It's not just the FAA that can be an issue. Some of us pre-millennials just don't like sharing our entire lives with anyone and everyone motivated to look/listen. And there can be legit reasons to obscure our movements; business transactions, physical abuse situations, etc. Lots of reasons; we just don't think about them if they aren't affecting us at the moment.
 
As much as I respect the VAF braintrust, this thread leaves me cluleless. I have no intention of doing wrong, and share disdain for big brother. But, can somone identify themselves as having bottom line credentials on the topic and tell us the bottom line ?
Interesting.

Ok, below in my signature are my bottom line credentials, although I fully understand they do not meet the expectation of your intent in asking for them, they never the less, are my 'bottom line' credentials.

Even though you may not have built your airplane it is still experimental. You may do what you will with it when installing ADS-B Out as long as it meets the technical and regulatory requirements of the instrument that are spelled out in the installation manual. You can have someone else install it, you can install it yourself. You can put an anonomous switch in it or not. It appears from other's posts above there is an advisory strongly suggesting there must be a switch but it also appears it will function as the FAA had intended even without a switch.

So here you go, the bottom line:
YOU will have to decide for yourself whether you should put a switch in or not. Further, YOU will have to decide whether you are ethically, morally, legally justified in doing so.
 
Clarification

From Garmin:

"...There are private pilots. And then there are extra-private pilots who want to keep their identities off the traffic screens of other ADS-B ?In? equipped aircraft (containing business competitors, perhaps?). GDL 82 and its UAT technology can allow for this extra measure of identity security with ?Anonymous mode.? Most conventional ADS-B devices are designed to transmit your aircraft?s ICAO number ? a discrete ?hex code? assigned by FAA as part of your aircraft?s certificate of registration. If you?re flying VFR, however, you can have GDL 82 set to mask your aircraft?s ID from being transmitted to other receivers whenever your transponder?s squawk code is set to 1200. ATC can still track you with ADS-B precision. But your GDL 82 simply won?t transmit your aircraft?s N-number to other pilots in the airspace..."

This would seem to imply that only the N number of your aircraft will be masked ONLY to other pilots in the airspace...the FAA would still have your hex code and thus, all of your information.

Seems like much ado about nothing...
 
...Seems like much ado about nothing...

As much as I dislike the thought of the feds being able to track my specific movements at all times now, the threat of anyone with an internet connection tracking my movements with up to the minute precision remains my primary concern.

If I can shield my comings and goings from any dirtbag with a smartphone who would not otherwise know my home is unoccupied or my wife is alone because I'm 200 miles away, I'm going to exercise that option. The ability for a bad guy to know with second by second precision where I am located (and when I will return) is very valuable intel. I prefer to not provide that information to the entire world.

So the "anonymous mode" is of value to me, even in its limited scope.
 
As much as I dislike the thought of the feds being able to track my specific movements at all times now, the threat of anyone with an internet connection tracking my movements with up to the minute precision remains my primary concern.

If I can shield my comings and goings from any dirtbag with a smartphone who would not otherwise know my home is unoccupied or my wife is alone because I'm 200 miles away, I'm going to exercise that option. The ability for a bad guy to know with second by second precision where I am located (and when I will return) is very valuable intel. I prefer to not provide that information to the entire world.

So the "anonymous mode" is of value to me, even in its limited scope.
A voice of reason!
 
As much as I dislike the thought of the feds being able to track my specific movements at all times now, the threat of anyone with an internet connection tracking my movements with up to the minute precision remains my primary concern.

If I can shield my comings and goings from any dirtbag with a smartphone who would not otherwise know my home is unoccupied or my wife is alone because I'm 200 miles away, I'm going to exercise that option. The ability for a bad guy to know with second by second precision where I am located (and when I will return) is very valuable intel. I prefer to not provide that information to the entire world.

So the "anonymous mode" is of value to me, even in its limited scope.

Made worse because the FAA insists that aircraft registries should be freely open to the public. I even asked the FAA once, and they said (misspelling of "our" and all): "Are records are public for safety"

Yet "safety" was the same reason driver's license and DMV registration info was made need-to-know information.

:confused:


My concern is automatic ticket/violation generation (I'm reminded of an early scene from The Fifth Element) coupled with every old yahoo with an internet connection being able to track me and see where I live.

I wish someone out there had an all-in-one 978 unit that didn't require me to buy and install a new Mode C unit as well--or come up with a way to make 1090ES anonymous.

I'm also researching ways to register my airplane to an LLC, not to get out of taxes or liability but simply so some jackhole can't look my registration up and get my name and home address.


Failing that, I demand that I be able to look up DMV records for everyone around me and track any car I want by GPS. I want to see where my congressmen are going :cool:
 
So the "anonymous mode" is of value to me, even in its limited scope.

I can see how it's valuable to have that feature, but the value is vastly diminished when it's not truly anonymous, and we haven't established whether it is or not.

One vendor says your hex code gets scrambled but ATC still has your ident.
One vendor says your ident isn't transmitted but doesn't mention your hex code.

Regardless, it doesn't help when your entire flight path can be made "not anonymous" by interacting with ATC along your flight. I still maintain that if you are based at a controlled airport or fly to or through controlled airspace where you are given a discrete code, that tag will enable someone to track your entire flight after-the-fact. You'll have an anonymous track that's linked in time and space to a tagged track, and it would be next to impossible to argue that the anonymous track isn't a continuation of your flight. Whether this extends to what a third party could infer live over the internet is unknown... But as they say, the data is out there, and it can't be retracted later.
 
and...

"...If I can shield my comings and goings from any dirtbag with a smartphone who would not otherwise know my home is unoccupied or my wife is alone because I'm 200 miles away, I'm going to exercise that option. The ability for a bad guy to know with second by second precision where I am located (and when I will return) is very valuable intel. I prefer to not provide that information to the entire world..."

I don't disagree with you, but as you said, the data is out there and readily available. It doesn't take very much effort to find your information, N number, hex code, address, phone number etc...

Also consider that there are many apps that easily allow anyone to search aircraft movement by departure airport, and track that aircraft using their ads-b data even without the n number...

Just sayin'
 
I have had Mode-S and ADS-B for five years now and I still remember landing in Texas after a VFR flight without talking to anyone and just as I shut down my phone rang. It was a buddy wanting to know what I was doing in Texas.

That was a bit of an eye opener.
 
This thread is why I occasionally have the insane idea of a non-electric system RV-10. The biggest thing stopping me is the <10k' limitation which is too restrictive.
 
I wish someone out there had an all-in-one 978 unit that didn't require me to buy and install a new Mode C unit as well--or come up with a way to make 1090ES anonymous.

See post #10 of this thread. It looks like the FAA is on board with providing an anonymous option for 1090ES. I’m going to hold off on equipping for ADSB out until I see where this is going. And more specifically i want to know if this will be a software “upgrade” to existing xponders or if it will require the purchase of a new “anonymous mode capable” transponder. They are talking about a technology demo early this year. I’d be surprised if Garmin wasn’t participating. What say you Garmin?
I am aware that anything more than a s/w upgrade will take a year or more to get to market. I’m ok with that, out here in the wilds of Indiana I don’t usually fly in rule airspace so I can wait.

Edit: I just reread the AOPA article referenced in post 10 and they do address the issue of N# being transmitted in anonymous mode by saying the anonymous mode for 1090ES would also include an anonymous call sign. Yea....
 
Last edited:
This thread is why I occasionally have the insane idea of a non-electric system RV-10. The biggest thing stopping me is the <10k' limitation which is too restrictive.

I'm not wild about hand-propping an IO-360... I've had the same thoughts about my RV6 :) What exactly constitutes an electrical system? Let's see - hang a starter on the motor with an external plug for your GPU. Then use handheld everything else for instruments....
 
Last edited:
...I don't disagree with you, but as you said, the data is out there and readily available. It doesn't take very much effort to find your information, N number, hex code, address, phone number etc...

Yes, not a bunch of effort to find your house and park out front.

But do you also want to hand that same individual the means to know with 100% certainty that you are 100 miles away? Or that he has at least XX minutes to do as he pleases with your home/family without fear of interuption from you?

Most criminals are opportunists/cowards. They dont like uncertainty of outcome, so why hand them the tools to make their chances of success significantly higher?

Good example: a buddy was taking a long trip and gave me his Spot tracker info. When he was due to return I was watching his breadcrumbs drop on his inbound leg. At the appropriate moment I wandered out to the porch to watch his arrival. Within seconds of my prediction they came roaring over the field. In this case my use of the info was benign, but imagine if I was a bad guy and had the same info? I could predict within seconds how much time I could spend in his house doing bad things. It astounds me how many people publish their SPOT tracking info on the internet. Just unbelievable.
 
I'm not wild about hand-propping an IO-360... I've had the same thoughts about my RV6 :) What exactly constitutes an electrical system? Let's see - hang a starter on the motor with an external plug for your GPU. Then use handheld everything else for instruments....

Electrical system for purposes of transponder/ADS-B requirements is defined as a battery and engine driven generator. So you can omit the engine driven generator and use a constant loss system or install a wind driven generator and be legal.
But remember that these circumstances must be continuous from original certification. You cannot convert an aircraft and "back" into the configuration.
 
yep...

"...It astounds me how many people publish their SPOT tracking info on the internet. Just unbelievable..."

I am in agreement. Those are the same folks that go on Facebook and advertise, to the known world, that they will be on vacation for the next two weeks...

Yes, the "anonymous" mode would be nicer if it actually did make you anonymous...I think, however, that really isn't the case except for the other pilots within a given volume of airspace.

There is a simple test to determine if you are anonymous. Hypothetically, if you were to enable the anonymous mode and fly into a restricted area, you would get a most definitive answer...:eek::eek:
 
"...It astounds me how many people publish their SPOT tracking info on the internet. Just unbelievable..."

I am in agreement. Those are the same folks that go on Facebook and advertise, to the known world, that they will be on vacation for the next two weeks...

Yes, the "anonymous" mode would be nicer if it actually did make you anonymous...I think, however, that really isn't the case except for the other pilots within a given volume of airspace.

There is a simple test to determine if you are anonymous. Hypothetically, if you were to enable the anonymous mode and fly into a restricted area, you would get a most definitive answer...:eek::eek:
That would not turn out well even if you proved a point. You would violate restricted airspace rules whether the ADS-B provided the FAA info or not. The feds could most likely track me down for such a violation using low tech means also. I for one am not willing to risk my ticket to test a theory on whether they could track me down using ADS-B data or not.
 
Lighten up, Francis!

It was a hypothetical experiment and completely in jest.

If anyone needs to be told NOT to fly into a restricted area, they probably should be flying in the first place.
 
My god..... the paranoia! I have to agree with several other commenters here about the fact that some people obviously believe they're way more interesting to the authorities and others than justified by reality.

If you seriously don't want people to track you or know where you are, then get rid of your phone and do not ever log onto a computer terminal. ADSB and aircraft registration anonymity is the least of your worries! You gave away your ability to stay anonymous and untraceable when you put the SIM card in your iPhone.

And if you unintentionally break the law and they see you, man-up and pay the penalty like everyone else on the planet has to throughout their life. If it was deliberate, well........

An airline colleague had his whole identity stolen recently via bluetooth. Credit cards, bank accounts, insurance details, friends and family contact details, everything. It took him months to get some semblance of normality back in his life. Such high tech theft is a lucrative business and it poses almost zero personal risk to the criminal. The idea that they're tech-savvy enough to track your location via ADSB, get the aircraft owner details, relate that to where you live, but then only use that information to race around with a sledgehammer to knock your door down and kidnap your sleeping first born child is straight out of a Hollywood movie.

Edit: For those interested, the ID theft via bluetooth occurred on an iPhone, in a hotel in China. My understanding is they got most or all of the entire contents of his phone, and used it to open credit cards, etc in his name.
 
Last edited:
The potential for personal data to be used for questionable purposes without the consent of its owners has been well publicized, and is a growing source of concern for many. It doesn?t seem unreasonable include private air travel in this concern.

Getting back to the original topic of the thread, I?m mostly interested in how the different ADS-B systems actually work, in order to make informed decisions. The information floating around the internet seems to be generally rather superficial, and occasionally wrong. The subject is inherently confusing, with two different services (TIS-B, FIS-B) operating in multiple different modes (air to ground, air to air, in/out, anonymous, public) on two different frequency bands, with equipment offered in various different configurations by various different manufacturers, at least one of which is suing another over patent rights! And then there?s Canada.

At the outset it was my firm impression that UAT systems allowed complete anonymity, 1090 ES would never have that capability, ADS-B required airspace will be identical to current Mode C required airspace, and that travel outside the U.S. would soon require 1090. Now I?m not so sure of any of those statements!
 
The potential for personal data to be used for questionable purposes without the consent of its owners has been well publicized, and is a growing source of concern for many. It doesn?t seem unreasonable include private air travel in this concern.

Getting back to the original topic of the thread, I?m mostly interested in how the different ADS-B systems actually work, in order to make informed decisions. The information floating around the internet seems to be generally rather superficial, and occasionally wrong. The subject is inherently confusing, with two different services (TIS-B, FIS-B) operating in multiple different modes (air to ground, air to air, in/out, anonymous, public) on two different frequency bands, with equipment offered in various different configurations by various different manufacturers, at least one of which is suing another over patent rights! And then there?s Canada.

At the outset it was my firm impression that UAT systems allowed complete anonymity, 1090 ES would never have that capability, ADS-B required airspace will be identical to current Mode C required airspace, and that travel outside the U.S. would soon require 1090. Now I?m not so sure of any of those statements!

+1. A very nice summary. ?A camel is a horse that was designed by a comittee?.
You forgot ?ground mode?, which is the reason for the ultra high gps accuracy requirements.
 
I’m mostly interested in how the different ADS-B systems actually work...
I installed a Garmin GDL-82 over a year ago and have been very pleased with it. My transponder is a Garmin GTX-327 and it didn't need to be touched. The GDL-82 is just inserted in the coax line between the transponder and antenna. The GDL-82 installation was straightforward, although in my fiberglass airplane I had to fabricate an 18" ground plane in the tail cone. Getting my body back there was difficult. You also have to supply a GPS signal either from the GA-35 antenna that comes with the kit, or from an existing WAAS GPS source in your panel. Wiring is just two wires for power plus two more if you choose to install the Anonymous switch and Fail light on the panel. Simple. The programming via the USB connector was straightforward. I also had to change out my Archer SA-005 transponder for a Delta-Pop blade type.

The combination of the GDL-82 and my Stratus/Foreflight/iPad for "In" is a great safety enhancement, IMHO. In my area, though, the TIS-B has been a real disappointment. There have been numerous times when approach calls out traffic which doesn't show on my iPad although, in theory, it should have. When most aircraft are ADS-B equipped, that should get better.

FWIW, I never use the Anonymous mode. Unless I decide to start running drugs, I don't see the point.
 
FWIW, I never use the Anonymous mode. Unless I decide to start running drugs, I don't see the point.

Will you feel the same way when the 'black box' built into all current cars gets datalinked to a DOT data mine, you you get fined every time you slip 5mph over the speed limit or get closer than the car length-per-10mph rule to the guy in front of you?

Just sayin'...

Charlie
;-)
 
My convert

*** Full disclosure *** I didn't read most of this thread.

Here is my concern with ADSB:

1) I build a tiny box that lets me read ADSB data, and picks up traffic all around me. I have already done this. It cost me under $100.

2) I see an N number and look it up online. I can see where the owner of the airplane lives. It also tells me his address. I routinely do this when I see N numbers reported in crashes.

3) Doing 1 & 2 above, a nefarious person could easily determine if the owner is local, and not likely home, but posses money (since he owns an airplane). Little does this person know that due to the true nature of aviation, there will be no money found.

I think the FAA plays fast and loose with our information by making it publicly available, as soon as situations like what I describe above becomes common knowledge, we will all have a problem. It isn't about what you do while broadcasting your information, it is what people will do knowing you are up in the air, and not likely to be down any time soon.

Could you imagine if the DMV released the name and address of every car owner? (They actually do, but you have to request the information for a given plate, and they notify the owner that you inquired.)
 
The Drivers Privacy Protection Act has been in place since 1994.

As a licensed dealer, I'm also a designated agent for my state's DMV. I can tap the database for an owner's name and address if I know the VIN...but I cannot tell you. It is federally protected information.

https://www.law.cornell.edu/uscode/text/18/2721
 
Last edited:
I think most folks are blissfully ignorant about how much information about you is already publically available. Also what kind of enemies do you have that you're worried about someone taking advantage of the fact you're out flying? If that's a realistic concern you have bigger problems than someone tracking you on flightaware. Else you should adjust your foil hat some.

That said I'll be in anonymous mode by default because I do agree the less information you volunteer the better. I won't lose sleep over it though...
 
Edited 19 Feb after learning it takes some amount of time more than the 30 seconds I gave anonymous mode for it to take effect. I'll measure it later.


BLUF,
I am able to see both my ICAO number hex code and N# on the saved files with the Skybeacon EITHER Anonymous mode on or off, at least in ground mode.

I was expecting to see the randomized ICAO number hex code in anonymous mode and suspected I would always see my N#.

Just so new thread readers don't have to track post references, I have a KT-76A that replies to ATCBRS interrogations (flashes reply light) so the Skybeacon fully tests on the ground at my hangar. It wasn't flying weather today.

I have a Skybeacon on my wingtip that PAPR flight passed with no exceptions. I have a USB SDR, the type that feeds Flightaware and other websites and 2 reside in the Stratux devices. My "In" device is a Skyradar DX because it easily pipes into my EFIS and portable devices simultaneously.

My Android phone runs AVARE and found for this thread their SDR App called AVARE ADSB Pro. It reads either 1090ES or 978 UA, streams to AVARE and also records them. The antenna, SDR and OTG USB to phone adapter were under $25.

I am able to see both my ICAO number hex code and N# on the saved files with the Skybeacon EITHER Anonymous mode on or off.

I'll see if this somehow happens in ground mode but not flight mode later.

The recorded fields are no where near inclusive, but are enough for the context-

ICAO (6 figure Hex code),Flight (your N#), Squawk, Altitude, Ground Speed, Heading, Latitude, Longitude

I'd post screenshots, but that's not keeping with where this thread has drifted ;).
 
Last edited:
I'll say this and hopefully leave it alone as it has been beaten to death...

It's great that people feel secure enough to not be concerned about bad people doing bad things. Not all of us are in that same boat, however. I happen to live in the Meth capital of the world and near enough to the cesspool of humanity that is the LA Basin that the "Hollywood crime fantasy" is more real than imagined. A simple road rage event can result in gunfire or assault; people are carjacked in broad daylight; a simple Craiglist transaction often results in robbery and assault; and even a shopping trip to Wallyworld sometimes produces an altercation of some kind in the parking lot or inside the store. People are angry, mean and devious. I've seen it first hand often enough to be VERY skeptical about everyone.

Bottom line, personal protection is much like flying- its not risk free, but it needs to be "risk managed". Just because some aspects of my life are not as secure as I'd like does not mean I'm going to hand over everything.

I mean, a determined thief can steal any car, but nobody leaves their keys in the ignition, right?
 
Ah yes, the common problem of meth heads robbing houses when folks file IFR, I nearly forgot.

We can expect at least a ten-fold increase when adsb goes live.

Oh the horror...
 
I'll say this and hopefully leave it alone as it has been beaten to death...

It's great that people feel secure enough to not be concerned about bad people doing bad things. Not all of us are in that same boat, however. I happen to live in the Meth capital of the world and near enough to the cesspool of humanity that is the LA Basin that the "Hollywood crime fantasy" is more real than imagined. A simple road rage event can result in gunfire or assault; people are carjacked in broad daylight; a simple Craiglist transaction often results in robbery and assault; and even a shopping trip to Wallyworld sometimes produces an altercation of some kind in the parking lot or inside the store. People are angry, mean and devious. I've seen it first hand often enough to be VERY skeptical about everyone.

Bottom line, personal protection is much like flying- its not risk free, but it needs to be "risk managed". Just because some aspects of my life are not as secure as I'd like does not mean I'm going to hand over everything.

I mean, a determined thief can steal any car, but nobody leaves their keys in the ignition, right?

Well said, Michael.
 
From Garmin:

"...There are private pilots. And then there are extra-private pilots who want to keep their identities off the traffic screens of other ADS-B “In” equipped aircraft (containing business competitors, perhaps?). GDL 82 and its UAT technology can allow for this extra measure of identity security with “Anonymous mode.” Most conventional ADS-B devices are designed to transmit your aircraft’s ICAO number — a discrete “hex code” assigned by FAA as part of your aircraft’s certificate of registration. If you’re flying VFR, however, you can have GDL 82 set to mask your aircraft’s ID from being transmitted to other receivers whenever your transponder’s squawk code is set to 1200. ATC can still track you with ADS-B precision. But your GDL 82 simply won’t transmit your aircraft’s N-number to other pilots in the airspace..."

This would seem to imply that only the N number of your aircraft will be masked ONLY to other pilots in the airspace...the FAA would still have your hex code and thus, all of your information.

Seems like much ado about nothing...

Bob,

Your interpretation of the written description is logical at first glance. But Garmin didn't do a good job with the detail. Their technical writer's bad. So this was clarified by Garmin Steve the G3Xpert early on. Despite the ambiguous language Steve uncategorically stated that nobody's system, not even FAA, can get your aircraft's identity from the data stream when the GDL 82 is in anonymous mode. Freeflight has confirmed same for their UAT products. Here is the link to G3Xpert's confirmation of this here on VAF:

http://www.vansairforce.com/community/showthread.php?t=151516&highlight=GDL+anonymous&page=2

I can also provide contact information for a Freeflight field engineer to confirm same for their product.

I had ordered two GDL 82 units at their introduction at Oshkosh 2017. I had been installing the Freeflight RANGR Lite UAT units with anonymous mode up to that point. Later I wandered by the Garmin tent and was told by a Garmin employee in a blue shirt that the GDL-82 anonymous mode didn't cloak aircraft identification from ATC. That concerned me as the Freeflight product had true anonymous mode so I felt maybe Garmin caved in to the FAA in order to expedite approval or something. I promptly cancelled my GDL 82 orders and put out the word here on VAF in case anybody else was considering the 82 anonymous option. That post was run up the flag pole at Garmin and they immediately responded from on high and clarified that the employee had been wrong and not properly briefed on the new GDL product. This response was from the engineering team who actually designed it. The GDL 82 does in fact not transmit identifying information of any kind to anybody, even the FAA, when sqwaking VFR with the anonymous switch enabled. You will see that in the referenced thread above.

Jim
 
Last edited:
Jim,

Thanks for the additional information, this is very helpful. Its also not very encouraging that even some of Garmin's own staff are confused about this issue!

AC-165B has more to say (copied below). If I'm reading this right you are allowed to broadcast a randomized 24-bit code and no call sign under certain conditions (978, squawking 1200, no flight plan). However...you are required to broadcast your aircraft's actual 24-bit code plus a call sign when the unit is initially powered on. If anyone is listening at that point you would not be anonymous.

The vague part would seem to be how long the powering-on phase lasts. According to what FreeFlight says on their web site (see Post #59 above), it lasts through the first few minutes of the flight. After that you are not broadcasting any identifying information, but if the system has already acquired your target and associated it with your callsign this may not matter. I don't doubt ATC could continue to track you solely based on your GPS position.

Unless of course the FreeFlight website is simply wrong!


 
Last edited:
Flew today. The randomized ICAO number shows on a recorder app and the callsign/n# replaced my N# with, "VFR"

Skybeacon used.

I agree, it takes a bit for the Anonymous mode to take hold. I'll see later if I can time it better.

20190219-153557.jpg
 
ADSB anonymous

Like snopercod says above, have the switch on before the unit is powered up and you will be anonymous from the get go. And about that AC- this is an ADVISORY circular so I don?t think it is regulatory. No reason I can?t see to ground pin 5 and be in anonymous mode any time 1200 squawk is selected. If you power up on code 1200 in this configuration you should be anonymous all the time until such time as ATC gives you a squawk.
 
so...

So now we need to get that same "screenshot" from someone in ATC to see exactly what they see on their screen when you are in anonymous mode...

Anyone?
 
Jim

AC-165B has more to say (copied below). If I'm reading this right you are allowed to broadcast a randomized 24-bit code and no call sign under certain conditions (978, squawking 1200, no flight plan). However...you are required to broadcast your aircraft's actual 24-bit code plus a call sign when the unit is initially powered on. If anyone is listening at that point you would not be anonymous.

The vague part would seem to be how long the powering-on phase lasts. According to what FreeFlight says on their web site (see Post #59 above), it lasts through the first few minutes of the flight. After that you are not broadcasting any identifying information, but if the system has already acquired your target and associated it with your callsign this may not matter. I don't doubt ATC could continue to track you solely based on your GPS position.

Unless of course the FreeFlight website is simply wrong!



I?m interpreting 3.7.2.3.1 and 3.7.2.3.2 to simply require the default power up to be your valid ICAO and last flight ID. This seems perfectly reasonable, you wouldn?t want to have to manually enter all that info every time you powered the system ON. I don?t see anything that precludes you from powering up in anonymous mode if desired.
As far as the requirement to fly around ?in the system? for ?awhile?:
It took some digging to find that quote on the Freeflight website. It turns out to be a blog post from 2016, so it?s far from a statement of any kind of actual ?requirement?.
In addition if this was a ?requirement? then all the other UAT manufacturers would know about this and presumably would include this in their operators manuals and it would probably have to be added to your aircrafts POH. So, I?m saying Freeflight is wrong, until they or anyone else can point to this in an official requirements doc of some kind.
 
From reading how the anonymous ICAO number is created, the UAT WAAS GPS source needs a lock. That is from where the position and timing comes that creates the string.

So, IF your ADSB UAT has the WAAS gps installed IN the unit, there is no way to get enough data to populate the self generated anonymous ICAO inputs immediately. If a WAAS source exterior to and feeding position to the UAT has a good position before powering the UAT, then Anonymous mode should be available sooner. Immediately? 5 seconds? Don't know.

So, not just on, but good gps lock at the UAT position source.

This would be the transmit side of anonymity. On the receiver side, an In device nearby can see you right away, but ATC does not see you until an ADSB GBT receives your Out.

My PAPRs say I had a valid flight as low as 200'. Not sure if that correlates to Mode C during a Valid flight, or actual UAT valid reception at the FAA GBT. I am not at a surface airport in the PAPR decoder link.

https://www.google.com/url?sa=t&sou...AegQIAhAB&usg=AOvVaw0aL_PlXuSIwz8GbtBlGyDyThe self-assigned temporary address shall be generated as follows:
Let: ADDRP = the ICAO 24-bit address that has been assigned to the aircraft;
ADDRT = the temporary address that is to be generated;
M(1) = the 12 least significant bits (LSBs) of the ownship “LATITUDE”
field (per §3.2.1.5.2.1) at the time the temporary address option is
selected;
M(2) = the 12 least significant bits (LSBs) of the ownship “LONGITUDE”
field (per §3.2.1.5.2.1) at the time the temporary address option is
selected;
M(3) = 4096 × M(1) + M(2); and
TIME = the number of seconds that have elapsed since UTC midnight at the
time the temporary address option is selected, represented as a 24-bit
number."
 
Last edited:
Well the plot thickens. I shot off an email to Freeflight systems asking if they do in fact suppress entry into anonymous mode for a set time period. And if so what requirement is driving them to do this. Received this reply today:

?When Anonymous mode is active (pilot actuated switch) the FDL-978 broadcast the ICAO and the Flight ID for the first 90 seconds after the unit is powered up. After this time the FDL-978 will broadcast a self assigned random temporary address for the ICAO and no Flight ID as long as the Squawk code is set to 1200.

In response to the ?what requirement is driving this behavior? the response was:

?Additionally AC20-165B describes the requirements of the Anonymity Feature for ADS-B out. Refer to Para. 3.7.2.3 thru 3.7.2.3.6?

This still seems wrong. I don?t see anything in the referenceed paragraphs that stipulates a ?lockout period? before anonymous mode is enabled. So is this just Freeflight?s interpretation? Does anyone with a UAT setup other than Freeflight see any such description in their owners manual?
If this is truly a requirement then I guess on the plus side there?s a chance you won?t see any towers on the ground so by the time you are airborne the anonymous mode will have become active. I guess I could tear a little tinfoil off my hat and stick it over the transponder antenna for 90 seconds........
 
Back
Top