PilotAware
British Forum => Technical Support => Topic started by: scsirob on February 18, 2018, 08:55:50 am
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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?
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Scsirob?
Can you post screenshots of your home page and config page?
Helps a lot to resolve issues.
Ta
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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
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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
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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
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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
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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
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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
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Hi Lee,
No, the firmware is the very latest right now. Updated this summer.
Rob
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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
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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.
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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
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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
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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?
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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
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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?
Your quite right, this filter can only work on known position targets so EVFR will still display a "Banner Alert," (and an Audio alert, if you have configured these in the "wearables" settings,) for any Mode C/S traffic that trigger the current Mode S settings in the PAW config screen.
Alan
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Great analysis, Paul. I will try to find out what firmware the others are running. This may shed some light on the matter
Just got confirmed that one of the transponders runs V4.8, and the other had his set to STBY by mistake. Neither has GPS hooked up.
Also, one of them flew with a Pingbuddy and did see me including altitude, speed and callsign. So I guess my V5.2 does do unsolicited squits.
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Thanks Peter; I tried to simplify the short squitter version of the transponder but I did not know PAW cannot use this information. I assume it just becomes, to PAW, another 'plain' Mode S transponder and the list should look like this instead:
1. A transponder will reply to interrogation from ATC or TCAS. This reply (squawk) can be used by PAW to generate a proximate alert based on the strength of the transmission. The reply to interrogation contains no other information that can be used by PAW.
2. A squitter is a thingy that transmits various bits of information about the aircraft and it does this periodically i.e without interrogation
3. A short squitter only transmits a Hex code
4. An extended squitter has GPS and other good stuff added to the short squitter and, so, 'becomes' ADSB
5. The early Mode S transponders did not have a squitter and relied on being interrogated. PAW can only generate a warning when ATC interrogate the transponder because there is no squit for it to see, only a squawk. This will be a 'signal strength' warning.
6. The next line of Mode S transponders had a short squitter, so sent out information without being interrogated. However, because it is only a Hex code PAW cannot generate a warning based on the squitter signal and, so, acts like No.5.
7. The latest Mode S transponders have an extended squitter and we can plug a GPS into them and chuck out ADSB signals. Both Mode S and ADSB transmit without interrogation through the extended squitter. PAW will give us a Mode S warning ('signal strength') if there is no GPS info on the squit and a full ADSB warning if GPS is plugged into the transponder.
We now know why one of the aircraft was dark and it seems the earlier firmware of the Funke transponders is either No.5 or No. 6. The supposition is there was no ATC or TCAS around to interrogate the Mode S transponder and, therefore, no trigger for a Mode S reply for PAW to use.
There is still some question as to the Funke extended squitter and whether it does squit as it should i.e. ALL the time, or whether it only squits when interrogated. Hopefully this is not the case or else it just becomes another plain transponder but with a fancy reply. However, Rob's report on a Pingbuddy seeing him would suggest this is NOT the case. As he could not see the other aircraft (singular) this shows there was no ATC interrogation but as he was picked up on the Pingbuddy it suggests the Funke transponder is working properly i.e. sending out the extended squitter message periodically and without being asked.