Flarm suppression of ADS-B out on Tow Planes

On Friday, March 22, 2019 at 12:44:48 AM UTC-7, Ramy wrote:
This sounds like an interesting possibility as the powerflarm core has a USB port. I’ll let Darryl analyze it...

Ramy

LXNav is waiting for FCC approval for the PowerMouse, which uses the new chip. Updates will probably come after that.
Jim

On Friday, March 22, 2019 at 10:13:51 AM UTC-7, JS wrote:
On Friday, March 22, 2019 at 12:44:48 AM UTC-7, Ramy wrote:
This sounds like an interesting possibility as the powerflarm core has a USB port. I’ll let Darryl analyze it...

Ramy

LXNav is waiting for FCC approval for the PowerMouse, which uses the new chip. Updates will probably come after that.
Jim

I think it would be great to see ADS-R and maybe TIS-B support in FLARM devices.

FLARM has two chips and associated software currently available to OEMs, the actual FLARM chip and a new 1090ES In chip. The new 1090ES In chip is different than what is used in PowerFLARM.

Unfortunately (and this confused me in the past as well) the LXNav PowerMouse does *not* use the new FLARM 1090ES In developed chip, it uses their own developed technology in conjunction with the FLARM chip. The LX Navigation Eagle *does* use the new FLARM 1090ES In and FLARM chips.

I say unfortunately as this may create differences in how these otherwise similar products operate. I guess we'll have to wait and see. Personally I would rather all this technology came from FLARM and all OEM products operate identically. LXNav clearly makes great products so maybe they'll pull this off OK, buy I am concerned that their decision to roll their own stuff here may not have been the best decision.

This stuff is not as simple as "just support xyz protocol", there are for example going to be devil is in the details of different $PFLAU and $PFLAA FLARM warnings being generated for ADS-B direct, ADS-R and TIS-B traffic. There are also operational things that can help improve ease of use and safety that I'd hope vendors implement (from understandable documentation about what TIS-B and ADS-R support there is and the implications of that to say the receiver detecting and warning if the own-ship 1090ES Out does not exist or is not transmitting the capability code for 1090ES In).

A FLARM device comes with more than usual ADS-B In traffic receiver capabilities, the precise traffic warmings, relatively low false alarm rate, ability to operate on tow or in a gaggle etc. The positional accuracy of ADS-R and TIS-B is less than ADS-B Direct, or FLARM and in the case of TIS-B the positional error is much more. So adding extra ADS-R and TIS-B data comes with some challenges, not insurmountable, but this likely needs to be done with a good technical understanding of both the FLARM traffic algorithms, and understanding of how ADS-R and TIS-B works in practice in the USA.

I hope vendors have been testing this stuff in a realistic simulated USA ADS-B/TIS-B/ADS-R environment before any USA product release, and that they explain implications of what what they implement for ADS-R and especially TIS-B (if supported) to users. (Don't forget for reliable operation both ADS-R and TIS-B require your aircraft to have TABS or 2020 Compliant ADS-B Out).

BTW technical aside... be careful when talking about "TIS-B" especially in more technical conversations with vendors. TIS-B can refer to the relay of SSR data from ground stations over ADS-B as implemented in the USA today (as I used it above). But to a more technical person TIS-B may also mean the general data message format used for both that FAA TIS-B and ADS-R services, for example if an engineer is reading the RTCA DO-260B standard they would implement support for the TIS-B message format to receive ADS-R data and might talk about that as "TIS-B support".

I think it would be great to see ADS-R and maybe TIS-B support in FLARM devices.

I had the same idea and made myself a hat with a ADS-B receiver for Raspberry Pi. The Pi is interconnected between the FLARM and the Butterfly display and the ADS-B information is added to the FLARM information.

My plan is to make it open source and open hardware, and provide PCB´s for those who are interested.

Bringing back this old thread.
So last year it seem that the ADS-B alarm suppression during tow was working well as I received only occasional short alarms.
However with most recent firmware and a new tow plane ADS-B installation I and others receiving constant alarm during the tow. Very distracting.
I don’t know if this is a regression in latest firmware or something wrong with the tow plane ADS-B.
I would like to know if others still experiencing ADS-B collision alarm during tow when towing behind ADS-B equipped tow plane.

Ramy

The PowerFLARM and ADS-B in the towplane have to have the same ICAO IDs (likely already done).

Without a PowerFLARM in the towplane, the glider PowerFLARM will see it as an ordinary power plane and can get worried.

Perhaps enrolling the towplane ICAO ID in FlarmNet will help the display logic. Won't hurt to try.

Hi Ramy

We're not aware of any regression. What firmware version are you using?

Sounds like the tow plane configuration is not consistent, either for the FLARM or the ADS-B transmitter. But that's me speculating.

Can you please send (IGC) log files to ?

Thanks
- Urban

Hi Urban,

I am using latest firmware 6.82.
Our tow plane has only ADS-B out, not flarm.
What configuration error in the tow plane could cause such issue?
I also exchanged emails with Daniel and will provide IGC file as soon as I get to my glider most likely next weekend.
Meanwhile I was hoping to hear from others if they still noticing false alarms during tow now that more and more tow planes in the US are equipped with ADS-B out.
I assume from the lack of response that folks no longer experiencing issues, or the season didn’t start yet for them to tell. Maybe the folks at Seminole can tell as their tow plane should be equipped with ADS-B out giving that they are in the Mode C veil.

Ramy

I am wondering if it would help to enroll the towplane ICAO ID in FlarmNet.

Of course the FlarmNet database is carried in the various traffic displays and flight computers, NOT in the Core.

Hi Ramy

Can't think of anything that's wrong here, 6.82 should suppress all ADS-B targets in the "right" relative position indicating a tow train. We'll have a look at the logs to figure it out.

As you mentioned correctly, FLARMNet does not influence alarming.

- Urban