Anonymous Mode

[ATC_RV8OR]

I’m not trying to hodgepodge. Ideally all AFS panel and components with Avidyne Navigators is my goal. I’d like to get it in the air and flying a year or two with the relatively cheap 430s and then drop coin on the Avidyne and be free of Big G all together.

Wanting the anonymous mode is what’s causing the mix match issue. I guess given the choice between anonymous mode or having zero Big G, I think I choose giving up on anonymous mode.

 

[BobTurner]

Mixing and matching avionics has always been a problem. If you enjoy a challenge and the cumbersome operation that is inevitably a result then that’s great.

Challenge? Yes, you have to do your homework.
Cumbersome operation? Not at all, if you did your homework.

 

[olyolson]

I have an Advanced Flight Systems touchscreen 5500 EFIS with the Skyview network, a Garmin GTN 650, a Dynon autopilot, Dynon autopilot servos, a Garmin GDL393D, and a Garmin GDL-82. Yes there’s a bit of mismatched equipment but it all works well and everybody plays nice. Why, because I got a lot of the equipment used right here on the forum to save some money and thought it would all work and it does. I like Walt’s philosophy of using Garmin gear but can’t really afford a new all Garmin cockpit. FYI- Walt did the pre buy on my -8 and if I could have I would have had him gut the plane and put in an all Garmin panel. What I have proves that if you do your homework and try to find some used gear you can get a pretty decent panel that works well.

 

[ve0kog]

From the GDL-82 manual it does not look like Anonymous mode is very difficult to implement. It simply sets the flight ID to "VFR" and transmits a random hex ICAO code (probably from a predetermined reserved range):

“Anonymous” mode (optional) transmits a temporary address instead of the
aircraft’s-assigned ICAO 24-bit address and “VFR” instead of the aircraft’s
registration number, when the interfaced Mode A/C transponder is set to the VFR
code, “1200”

There is already a field to enter the Flight ID and the ICAO code in most of the transponders setup screens. I'm curious if there is any technical reason the anonymous mode is only available with 978MHz UAT. Since the coordinates are known an additional check can be added to confirm that the aircraft is within the U.S. boundaries.

 

[jliltd]

Are there any current product offerings that provide 'anonymous' mode?

The Garmin GDL-82 and the Uavionix UAT have both been discontinued.

I'm assuming a mode c transponder is required for anonymous.

Uavionix Skybeacon. Freeflight Rangr 978 transceiver coupled with Mode C. Garmin GDL-88 coupled with any Mode C transponder. Garmin GDL 84 coupled with any Mode C transponder (GDL 84 can be updated to GDL 88 later if desired)

Garmin makes the digital GTX 325 Mode C transponder still today new. Sandia makes the STX 165 and STX 165R Mode C transponders. Microair makes the T2000 Mode C transponder (spotty reviews). Sandia makes an all-in-one STX 360 that is a combination Mode C transponder and UAT in and out. ACS shows the STX 360 on indefinite back order.

True the GDL-82 and Uavionix Echo have been discontinued. But Skybeacon and Tailbeacon UAT are still available. As well as the equipment listed in the first paragraph above.

Mode C is required for true onboard generated anonymous mode. That is because legacy Mode A and C have always been anonymous. Mode S (1090 Mhz) has always transmitted airframe registration. It is a fundamental part of the original Mode S specification. So no true anonymous mode under Mode S or ES. Mode C with UAT out is not a problem domestically unless you want to fly over 18,000 feet.

 

[ve0kog]

no true anonymous mode under Mode S or ES

I'm still confused about this. If PIA is compatible with Mode S/ES why can't anonymous be? The only difference between the two is that the Flight ID and the icao code in PIA are preregistered with the FAA, while the anonymous mode uses a generic "VFR" flight id and a temporary code.

 

[gyoung]

I'm still confused about this. If PIA is compatible with Mode S/ES why can't anonymous be? The only difference between the two is that the Flight ID and the icao code in PIA are preregistered with the FAA, while the anonymous mode uses a generic "VFR" flight id and a temporary code.

I don't know if there is a technical reason that drove it but the reg specifically only allows anonymous mode with the 978 UAT and not with the 1090 used by Mode S transponders.

 

[jliltd]

I'm still confused about this. If PIA is compatible with Mode S/ES why can't anonymous be? The only difference between the two is that the Flight ID and the icao code in PIA are preregistered with the FAA, while the anonymous mode uses a generic "VFR" flight id and a temporary code.

It’s the gubmit’. No rationality. But basically the way it was explained to me was since Mode C never provided identifying information for the airframe that anonymity was grandfathered in. So the when a UAT out system is used with a Mode C transponder squawking VFR is switched into anonymous mode the circuit board changes the real ICAO code with a random number that is generated by the equipment itself onboard the aircraft. The beauty of that is the registration ID is never sent to the outside world in any form. I have seen “VFR” as the most common target identifier but have also seen “Ping”. And more than one manufacturer engineer has told me since the ICAO is randomized and it’s the one and only number used not even the FAA or Military can decipher your actual ID from it. Not that it would matter as both those organizations can figure out who an airplane is fairly easily and quickly even without a positive ADS-B registration transmission.

 

[ve0kog]

It's hard to believe but the FAA responded to my inquiry about the anonymous mode on the 1090 MHz band.

9-AJE-ADSB (FAA)
1:30 PM (13 minutes ago)

to me

The current avionics standards for 1090 transponders that can support ADS-B, do not have the capability to transmit a non-ICAO address (or an anonymous code). To be acceptable, a new or modified industry standard would be needed, and the regulations accepting the use of equipment built to that standard would need to be published.

For those things to happen, the FAA and avionics/aviation industry (who develop those standards) would need to find a compelling safety or business case. Both the standards development and rulemaking are lengthy endeavors.

Finally, a big safety concern that would have to be addressed is the impact such a system would have on collision avoidance systems that operate on 1090/1030 Mhz.

So, while it is theoretically possible develop an anonymous mode for 1090 systems, it would be challenging to make it a reality.

Unfortunately nothing earth shuttering, except the part that we may need to continue talking to the "avionics industry" to make things happen.

 

[mburch]

we may need to continue talking to the "avionics industry" to make things happen.

FYI, I think they are referring here to entities such as RTCA, not individual hardware manufacturers.

 

[jliltd]

It's hard to believe but the FAA responded to my inquiry about the anonymous mode on the 1090 MHz band.



Unfortunately nothing earth shuttering, except the part that we may need to continue talking to the "avionics industry" to make things happen.

And yet they allow anonymous UAT aircraft to operate with a random ICAO code in the same airspace that the FAA says there may be safety or business issues if 1090ES were allowed to be anonymous.