Send ADSB into FLARM-type traffic display?

[Dan Kvinge]

There are many good FLARM traffic awareness devices that show threats in a simple and easy to understand way.    I own two of them...LXNAV S80 vario, and LXNAV Nano4.   I also like the looks of LXNAV FLARM LED+, and the Air Avionics Traffic Display.

My problem is I don't have a FLARM receiver, and nobody in my area flies with FLARM output anyway.

I know Power FLARM picks up 1090 MHz ADSB signals, and rebroadcasted 978 MHz as 1090 MHz.   But I'm outside of most FAA radar and so would not get the UAT-R signals.  

I do have easy access to ADSB-in via Sentry and other devices, and ADSB is what all of general aviation is using, and what I most fear of crashing into.   Isn't there some type of software converter that would take all the ADSB signals and pump them into a FLARM type traffic display?   

[John Foster]

I have a PowerFLARM Core connected to my S80.  It receives and displays both ADSB and FLARM signals well.  I have two FLARM antennae, and one ADSB antenna connected to the PowerFLARM Core.

[Moshe Braner]

There are of course other devices designed to display ADS-B traffic data as reported by receivers such as Sentry.  But it is nicer, in a glider, to see the traffic right on your glide/nav computer, which may only be possible by feeding FLARM-format data to the glide computer.

Your best action at this point is to get a PowerFLARM, then you'll "see" both ADS-B traffic and FLARM traffic.  There may be few gliders in your area with FLARM currently, but that may change, especially with a cheap FLARM mimic available, called SoftRF.  Alternatively, if you use SoftRF connected to another device, such as Sentry, to receive ADS-B, there may be a way to have SoftRF report ADS-B traffic to devices that display FLARM traffic.  Depending on the data format the other device reports ADS-B traffic in.  SoftRF includes code to process sentences in GDL90 and in DUMP1090 formats.  But it would probably require some additional software development to have SoftRF input from an external device in one data format, and combine with its own data (GPS and FLARM traffic data) and output in another format.

AFAIK only a small percentage of airplanes with ADS-B output in the US use UAT (978 MHz).  Also, ADS-R re-broadcast only happens when an ADS-B  ground station "sees" both the UAT originator and some other aircraft with ADS-B 1090 (so that they know somebody will receive it - can you say "Rube Goldberg"?).  Therefore I don't see the point in worrying about this new feature in FLARM (a software change that they want extra money for).  About 95% of ADS-B traffic is on 1090 and any PowerFLARM will report it.  I'm more worried about the non-ADS-B aircraft, the Cubs and Champs around here who may have ADS-B receivers but no ADS-B output of any sort.  (If the FAA will ever allow low-power ADS-B transmitters like they do in some other countries that may change.)

[son_of_flubber]

On Tuesday, January 30, 2024 at 2:17:01 PM UTC-5 Moshe Braner wrote:

AFAIK only a small percentage of airplanes with ADS-B output in the US use UAT (978 MHz).  

I've read about 1/3 ADSB-out installs in the USA use 978 UAT.   For example, UAVIONIX TAILBEACON, the plug and play low cost ADSB-out solution uses 978 UAT.

I bought the ADS-R license for my PowerFlarm.  Every collision-reduction tool is good, but not PERFECT.  Combine several tools and improve your odds.  I think the biggest bang for the buck is Daytime Conspicuity Lights like https://aeroflash.de/ which works as good as or better than PFlarm and ADSB in the pattern (because both of those throw spurious alerts in the pattern and I prefer to keep my eyes outside the cockpit in the pattern).

I like the Air Avionics Traffic Displays which accept PFlarm, ADSB-in, and Garmin protocol.  I think they accept two protocols simultaneously, so you could combine a GARMIN GDL with PowerFlarm if you don't want to rely on ADS-r..  I prefer a dedicated traffic display that does not have the clutter of a moving map because it is easier to read alerts at a glance.  I also like Air Avionics user interface for displaying alerts and interrogating targets.  Displaying traffic on moving map for situational awareness is obviously a good idea as well.

[Peter von Tresckow]

The stratux auropean edition will do all of the things you are looking for, but you will need to do some reconfiguration.

https://github.com/b3nn0/stratux

I currently have a stratux with a 978/1090 sdr connected. I also hooked up a SoftRf t-beam as the GPS/Flarm/OGN source. I then output the results through a usb to serial adapter to my Oudie. It's a bit kludgy, but it does work pretty well.

Peter

[Dan Kvinge]

This is great info!  I've looked at SoftRF a bit, but not being a programmer it was too complex for me.  However, we have a few guys in the glider club that will see it as a fun challenge.  

I also have a drone device that receives ADSB traffic and outputs it into MAVLINK, so with a translator to FLARM maybe that's another way to send it into my vario or other simple traffic display device.

Moshe's comment about very few planes having 978 MHz got me wondering.....   I think uAvionix has sold a lot of SkyBeacons and TaiBeacons. 

I went to ADSBexchange and did a simple filter for all USA aircraft from 1000-6000 MSL, and then an added filter for those reporting UAT/ADS-R signals.    Based on the whole USA it was about 8% flying with UAT.

Then I did the same thing where I fly, near the Minneapolis area and about 50 miles beyond the Mode C veil.   As I expected that shows more UAT targets---about 12-15% UAT/ADS-R.      And this data is for a winter Wednesday morning, so I assume the UAT % will go higher on the weekends, or in the summer afternoons as more recreational pilots get airborne.     What it means to me is that where I fly I'd like to catch both 1090 and 978 MHz air-to-air signals, and do it in a glider-friendly display format.   

Thanks again for the good tips!

[Cliff Hilty]

Interesting discussion, in our 170 we installed uavionics sky becon and display adsb traffic on a Ipad mini running fore flight. That gave me an idea for my 27 that I race with. I only had a SN10B as a flight computer and a dedicated powerflarm core and display. Several years ago now I purchased a Garmin 660 aera and GDL 52 ADSB on sale during Oshkosh for less than 1K. I use the aera as my moving map and can get adsb traffic and weather. Its not designed as  a moving map for glider contests not having a landout glides but does have the data for tps as well as airports but works well and I love the SN10B for the contest features of landing tps. Any way its all functional and ivestment of way less than half of the current crop of new flight computers!

CH

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[Moshe Braner]

I've now done that "additional software development".  Version MB114 of SoftRF can now import traffic data in GDL90 format from an ADS-B receiver, via serial cable or WiFi TCP, and integrate it into its internal table of traffic along with FLARM traffic, reporting all the traffic to a glide computer in FLARM format.   This is experimental, and has been partially but not fully tested.  If somebody is interested and can gather the necessary equipment (an ADS-B receiver such as Stratux, and a T-Beam for SoftRF), we can collaborate to fully test this capability, which builds on top of the data-bridging capability.   https://github.com/moshe-braner/SoftRF

On Tuesday, January 30, 2024 at 2:17:01 PM UTC-5 Moshe Braner wrote:

[Dan Kvinge]

This is great news Moshe!  We have an old Stratux and a couple newer Sentry's in the club.  I'll arrange to get the SoftRF and see if we can make them talk FLARM to an LXNAV S80 vario, and a NANO3.   Once we have the required hardware together I'll get back to you.  

[Moshe Braner]

And more recent versions of my branch of SoftRF also allow adding an internal ADS-B (ES1090) receiver module (instead of an external device using GDL90).  That module is very small and relatively inexpensive.  The ADS-B traffic is integrated with the FLARM traffic for display and for alarms.  Note that UAT978 traffic (which is becoming more common) is not received by this module, and would only be reported if the same or a nearby aircraft requests (via transponder configuration settings) ADS-R services.  That limitation is true for PowerFLARM too.  Also, unlike PowerFLARM, this module does not report aircraft with just plain transponders (without ADS-B out).  In theory, with some software tweaks, it could report Mode S transponders - as non-directional targets with only a vague notion of distance based on signal strength.  But are there many aircraft with Mode S transponders, rather than Mode C?  I'm told that Mode S is common in Europe (without ADS-B?).  How about in the USA?

[Mark Mocho]

OK, I admit that 90% of the previous thread is WAY over my head, but it seems to be saying that PowerFlarm is the simplest method of getting ADS-B signals into the flight computers we use (like the LX90xx). My question is, considering the "quality" of the PowerFlarm antennae, just how good is PowerFlarm at receiving, processing and outputting the data?

I fly with PowerFlarm and the aforesaid LX9000, and while Moriarty isn't a "High Traffic" environment, we do get all sorts of other GA airplanes, Military and Commercial Airliners through the airspace. I get at least some of the traffic on my LX000 display, but I am not convinced I am getting it all. In fact, I have seen airliners visually that either never appear on the display or show up AFTER they have gone by. This is also true for Flarm contacts, but I recognize that other gliders' antenna placement is often not optimal, and signal blockage by metal or carbon airframe components is also a factor. I am running a lower fuselage (interior) Flarm antenna, as well as the two dipole antennae upright on either side of the glare shield with clear sky views through the canopy.

The PowerFlarm PFCONFIG file is set to reasonable values to ignore contacts that are too far or too high to worry about. Some of these visually acquired contacts are well within the range parameters I have set, but do not show on the display. Any enlightenment from the RAS users who have successfully come to grips with the acronym-heavy ADS-B world?

(I will be adding ADS-B Out via Trig TN-70 or TN-72 to my Trig TT-22 this winter)

[Paul]

>I will be adding ADS-B Out

This is the way to go.  It's cheap and easy if you already have a Trig TT21/22, and you can DIY the install if you have Experimental R/E airworthiness certificate.  The installation is very easy. 

Gliders are very hard to see, but it seems that many Power Pilots watch their traffic displays very closely and most have ADSB 978 and 1090 dual band recievers.  On the ground, power pilots have told me they're happy to see me on their traffic displays.

I licensed PowerFlarm core ADSB-rebroadcast to get the 978 traffic, but I rarely have line-of-sight to an FAA ground station that is doing the rebroadcast.  It is never a good idea to trust/rely on the ADSB-in traffic display.

My glider is experimental R/E, so I was not required to install an Air Speed Switch.  I've gotten radio calls from confused power pilots just prior to the start of my aerotow.  It's a distraction for everyone, so I'm going to add an airspeed switch next year.

I installed aeroflash.de canopy and belly flashers.  Very positive feedback after flight on the ground from people who've seen the flashes in the air.  I hope that more clubs will install flashers in aircraft that do not have PF nor ADSB.  Amongst the 5000 gliders that have installed flashers (mostly EU), there's a consensus emerging that flashers are extremely effective in the pattern where mid-air collision risk is high.  The flashers are very visible to the crew at the launch point, so they're aware that I'm landing soon.  This is especially true on final leg when the canopy flasher is pointed straight at them.

[Moshe Braner]

Flarm transmits at about 0.025 watts.  Transponders (including ADS-B out on 1090) at about 200 watts.  That is 8000 times more power.  Thus, it is much easier for the receiver, e.g., the one inside the PowerFLARM, to receive the ADS-B signals.  (The frequencies are similar: 1090 MHz for ADS-B, and 915 in US or 868 in EU for FLARM.)  If your PowerFLARM does not show you ADS-B traffic that is within relevant range, that may be because it is busy showing you other traffic (including FLARM traffic).  It can only report a few aircraft due to limitations on the serial connection speed (and the processing power of the device), and it prioritizes closer traffic.  Also note that some airplanes have ADS-B out on UAT978 rather than ES1090, and PowerFLARM does not receive that.  The ADS-R re-broadcast on 1090 only happens if there is an aircraft near you that requests it.  When you install ADS-B out you can configure it to request it, basically it will be telling ATC that you can receive 1090 but cannot receive 978.  You'll also need to pay FLARM the extra license fee before it will show you ADS-R data, which I think is not nice of them, since it's just a small software tweak and a safety issue.

[Paul]

>Flarm transmits at about 0.025 watts.  Transponders (including ADS-B out on 1090) at about 200 watts.  That is 8000 times more power.

A bit off topic, but I've had discussions last summer with some very smart engineer type people who worried that a transponder would drain their glider batteries.  The TRIG TT22 outputs 200 watts, but it only consumes .34 amp.  That's .34 Ah per flight hour. So a TT22 running on a 11 Ah LiPo4 battery takes about 32 hours to drain the battery.  How can power consumption be low, when power output is so high??  Well... the RF output of the transponder is a series of RF pulses. Each RF pulse lasts for a very short time.  And Trig transponders consume very little power between pulses.  The GPS unit that is needed to upgrade the transponder to ADSB-out uses an insignificant amount of power.  

The regulation that exempts 'aircraft without an electrical system' from the transponder requirement is anachronistic.  There's no technical reason to opt out of ADSB-out in a glider.

My total power consumption measured in flight with a DC power analyzer is about 1.3 Ah per hour.  With two 11 Ah LiPo4 batteries, I should get 17 hours of flight time before the batteries are drained.  I have all the gadgets.  Powerflarm, ADSB-out, Digital Vario, Trig Radio, Traffic Display, Canopy and Belly flashers.

[Soartech]

The consumed power is low so not a problem for the battery. The transmitted power is very high so that is a problem for the pilot! The antenna is just inches away from your head. It does not matter much that the duration of the pulse is short. That much RF power can still affect cellular chemistry. Many studies have shown this. A local police chief developed brain cancer after years of carrying his radio in his shirt pocket so the antenna was near his head. He sued the company and won. I wouldn't risk using ADSB out unless I was in an all metal aircraft and the antenna was mounted far away and on the outside Just like it is in most airplanes. (I am an EE.)

[Mark Mocho]

The antenna doesn't have to be "inches from your head." Mine is a stub antenna with a ground plane mounted behind the landing gear, inside and near the bottom of the fuselage. Anybody dumb enough to stick a high-power broadcast antenna near their head might actually benefit from the brain altering rays. It probably won't make it worse. (Yes, that's a joke.)

[Eric Greenwell]

Glider pilots have been using transponders for many years (and airplane pilots many more), but I never heard of any having health problems caused by transponders. I do know of at least one that would have avoided a fatal collision if he'd had the transponder on, and one that miraculously survived, along the people in the business aircraft (Minden event). So, I think my health risks are a lot smaller if I use a transponder. 

[David S]

The available evidence says that radio waves do not cause cancer.  Alas, jury awards are possible even when a demonstration of cause and effect is not.

https://www.cancer.org/cancer/risk-prevention/radiation-exposure/radiofrequency-radiation.html

   ...david

[Paul]

My ADSB-out antenna is inside the tail boom near the empennage. No carbon fiber in my fuselage.

The radiation risk is mitigated by my flying less than 100 hours a year.  The radiation risk is offset by reducing the risk of mid-air collisions.  Two near mid-airs with airplanes motivated me to upgrade to ADSB-out.  A week after turning it on, I listened to Approach twice warn an airplane of a glider circling on their 12, same altitude.  After the 'one mile' warning, the pilot  said, 'I still don't see the glider, but I have him on my fish finder.'  This single incident paid for the cost of the upgrade.

A near midair in the pattern with another glider in 2023 motivated me to install the canopy and belly flashers.  On the ground, the other pilot said he never heard my radio calls, nor did he see me.  I was on midfield crosswind and he was entering downwind.  His glider was slightly lower and hidden behind my panel.  After I crossed the runway, I made a steep turn right 45 degrees and there he was two wingspans from my wing tip, same altitude.  Quite a show for the pilots watching from the ground.

I've had bad luck with too many near midairs.  That is why I have all of the gadgets.  Airplanes have been my biggest problem, and ADSB-out quickly paid off.  Several airplane pilots based at the field have complimented me for installing ADSB-out, so I know that they're seeing me on their traffic displays.

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[Mark Mocho]

In an earlier post I made on this thread, I mentioned that i seemed to be having a problem receiving some Flarm and ADS-B signals. While in the process of adding a Trig TN-72 to the Trig TT-22 transponder, I found that the two PowerFlarm dipole antennae BOTH had broken connections inside the rectangular housing. Therefore, the RX/TX antenna and the ADS-B antenna were not functioning correctly, if at all. Fortunately, repair was simple with a soldering iron. I also "potted" the wires with some hot melt glue. 

The problem undoubtedly arose from my rough handling of the antennae when removing or reinstalling my canopy. I will reevaluate my mounting system to try to avoid the problem in the future. Just a heads up to other Power Flarm users. Note that checking the antenna for connectivity is simple- just remove the two little screws from the rectangular housing and open it up. Both antenna stalks should be soldered to the respective coax wire leads.

[Moshe Braner]

While checking antenna conductivity, I suggest also using an ohmmeter between the shield and center conductor (to test for a short-circuit within the cable or connector) and between each of those "antenna stalks" and the corresponding part of the connector on the other end of the cable (to test for a broken wire within the cable or connector).  (Disconnect the other end of the cable from the FLARM before doing these checks.)