Traffic in sight, does not show up

[scsirob]

Yesterday I flew with PAW fully installed for the first time. My flight was together with two other planes in visual range, less than 1 mile separation, sometimes alongside, both with active Mode-S.

Commercial ADS-B traffic showed up fine, up to 100 miles away. But the Mode-C/S traffic that flew right next to me did not trigger any warnings. Mode-C detection was set to the suggested settings in the manual (2000ft, short range).

While flying I couldn't browse to the PAW (busy flying, not a technical issue), but on the ground I could see a long list of traffic, including mode C and CS traffic.

Any ideas?

[Ian Melville]

Scsirob?
Can you post screenshots of your home page and config page?

Helps a lot to resolve issues.
Ta

[exfirepro]

Rob,

As per Ian’s post screen grabs of Home, Configure and Traffic are worth their weight in gold, so we can see what is going on. As you were seeing ADSB, it’s most likely a settings issue, though at 1 mile on short range and with separation altitude set to +/- 2000ft, I would have expected some alerts. I take it you do have ‘Show Bearingless Targets’ selected in your Nav System (off by default in SkyDemon for example). If that is OK, try going to Medium Range and see what happens next time you are up.

Also remember that Mode S needs to be interrogated by RADAR or TCAS to transmit - ocassionally a problem for us up here in the wilds of Scotland, though I’d be surprised if this was the issue in your case.

Regards

Peter

[scsirob]

Thanks Ian,

A bit hard to do, as the PAW is now fixed in the plane. Are there any specific settings I need to attend to next time I get to the hangar?

Btw, I'm using EasyVFR. While on the ground I did get a few Mode-C alerts (Red bar with an altitude and an arrow up or down). But the two planes I flew in parallel with did not trigger an alert, even when one flew next to me at 100ft distance.

Rob

[scsirob]

Peter,

Thanks for reminding me about the interrogations. I just checked FR24, and neither my flight, nor the flights of the other two planes were recorded. So perhaps this is a case where the local Mode-S radar station was U/S and we never got interrogated. Not reflected in the NOTAMs but who knows..

That would be a good reminder that all this technology is great but only works when the entire chain is working, and looking outside is a must.

Rob

[exfirepro]

Rob,

What type of Mode S transponders are you using? With Trig, some Funke and some others, it’s fairly easy (at least in Permit aircraft) to convert them to ADSB Out by supplying gps data from your PAW. That gets over the issue of needing to be interrogated as ADSB out is (usually) automatic.

There is a paper on the PilotAware website  www.pilotaware.com pointing you to how to do this.

And yes, ‘Eyes Out’ is still a Must!

Regards

Peter

[scsirob]

Peter,

My transponder is a Funkwerk TRT800. I fly an Annex II home-built. The transponder is wired for extended squitter for years already (just checked: wired in 2011), fed by a dedicated Garmin GPS mouse. I wired it as soon as I saw the option in the manual, and only learned much later that the initial firmwares were not really suited for this. Funkwerk never issued any SBs advising against it, so... Got some remarks early on from ATC wondering why I showed up amidst 'the big boys', but never any complaints or requests to switch it off. I have had the firmware updated to the latest last summer, so it should now be on par with UK Permit aircraft.

The other two aircraft also have TRT800 transponders, but not wired for extended squitter. Both have told me they'd do this some time this year.

Usually my flight show up on FR24, but not this time.

Regards,
Rob

[Admin]

Oh this is a familiar story 
So Rob, there is a firmware bug in an early version of the funke firmware, which causes the extended squitter to only occur on interrogation- this explains your findings

So what you have there is I-DSB (Interrogated Dependant surveillance broadcast)

Thx
Lee

[scsirob]

Hi Lee,

No, the firmware is the very latest right now. Updated this summer.

Rob

[Admin]

Hi Rob
Ok, I think the questionable version was 4.9 and earlier, but don’t quote me on this, there is another thread on the forum describing this issue

http://forum.pilotaware.com/index.php/topic,1180.msg13969.html#msg13969

Thx
Lee

[PaulSS]

Let's see if I've got this right and then it might shed some light on Rob's snag.

1. A squitter is a thingy that transmits various bits of information about the aircraft and it does this periodically i.e without interrogation
2. An extended squitter has GPS info added to the basic squitter and, so, 'becomes' ADSB

3. The early Mode S transponders did not have a squitter and relied on being interrogated
4. The next line of Mode S transponders had a squitter, so sent out information without being interrogated
5. The latest Mode S transponders have an extended squitter and we plug a GPS into them and chuck out ADSB signals without interrogation

Now, I know Rob's transponder has been updated, so in theory he should have No.5 above and with GPS input to his transponder he should be transmitting ADSB.

What about the other two aircraft and their firmware state? If they're No. 3 then they won't appear on the screen unless an ATC unit (or TCAS) interrogates them. If they're No. 4 then they SHOULD appear as they should be squittering away and, likewise, No.5 (even though they may not have GPS plugged in and, therefore, won't appear as ADSB).

I think this theory is correct BUT it would appear that the Funke transponders don't squit without interrogation before No.5 firmware i.e. their squitter is not squitting but squawking with No.3 AND No. 4.

The Trig units seem to work as they should and this is borne out by what has been written in this forum but it would be nice to know the exact state of affairs from Funke themselves because something is not quite right with their boxes of magic.

[AlanG]

Hi All

You should know that EasyVFR has a filter in the software that prevents aircraft within 100mtrs of you from showing up on the navigation screen.  This is to cut down on multiple alerts on the screen when on the ground/apron.  I realise you are not likely to be flying at this distance, (unless you are a certain Peter party who shall remain nameless,) but worth keeping in mind.

Regards
Alan

[exfirepro]

Don’t tell them your name Pike! Oops - I just did 

A number of users have already asked Funke and they have (allegedly) just bought a PilotAware for testing, so we should hear more shortly.

Peter

[scsirob]

What about the other two aircraft and their firmware state? If they're No. 3 then they won't appear on the screen unless an ATC unit (or TCAS) interrogates them. If they're No. 4 then they SHOULD appear as they should be squittering away and, likewise, No.5 (even though they may not have GPS plugged in and, therefore, won't appear as ADSB).

Great analysis, Paul. I will try to find out what firmware the others are running. This may shed some light on the matter

Alan, that's good to know. But with mode C/S and no GPS information, how would EasyVFR know the other plane is within 100m?

[exfirepro]

Let's see if I've got this right and then it might shed some light on Rob's snag.

1. A squitter is a thingy that transmits various bits of information about the aircraft and it does this periodically i.e without interrogation
2. An extended squitter has GPS info added to the basic squitter and, so, 'becomes' ADSB

3. The early Mode S transponders did not have a squitter and relied on being interrogated
4. The next line of Mode S transponders had a squitter, so sent out information without being interrogated
5. The latest Mode S transponders have an extended squitter and we plug a GPS into them and chuck out ADSB signals without interrogation

Now, I know Rob's transponder has been updated, so in theory he should have No.5 above and with GPS input to his transponder he should be transmitting ADSB.

What about the other two aircraft and their firmware state? If they're No. 3 then they won't appear on the screen unless an ATC unit (or TCAS) interrogates them. If they're No. 4 then they SHOULD appear as they should be squittering away and, likewise, No.5 (even though they may not have GPS plugged in and, therefore, won't appear as ADSB).

I think this theory is correct BUT it would appear that the Funke transponders don't squit without interrogation before No.5 firmware i.e. their squitter is not squitting but squawking with No.3 AND No. 4.

The Trig units seem to work as they should and this is borne out by what has been written in this forum but it would be nice to know the exact state of affairs from Funke themselves because something is not quite right with their boxes of magic.

Paul,

There is one minor flaw in your otherwise excellent hypothesis.

Mode S ‘short squitter’ (4.) is automatic, i.e. transmits the ‘short squitter’ without interrogation, but the ‘short squitter’ only includes the device Hex ID. This is useful to Radar units in enabling them to identify and then Selectively interrogate individual transponders (which is what Mode S stands for), but is insufficient information for PilotAware to action an alert, or to be recognised as ‘ADSB’ traffic, without the full ‘Extended Squitter’ data packet.

Regards

Peter