Ghosting

[exfirepro]

James/All,

[Edited after looking back through my testing notes]

We did have an incidence of something like that back in Jan/Feb 2018 (Version 20180129 - Ian C - RV7 out of Perth), where a Positional aircraft persisted on SD - following Ian’s aircraft in exactly the same position relative to his aircraft - for a considerable time after the other aircraft’s PilotAware signal had dropped out. It turned out to be due to a bug causing the aircraft’s last known relative position (from P3i) to persist because Ian’s PilotAware was still receiving an ongoing Mode-S signal from the same aircraft. But the bug was found and the problem resolved - so I’d be very surprised if it was the same sort of thing.

I'm still waiting for an answer from John about what he ‘disconnected his GPS Mouse’ from (to discount the fact that there still may be another device lurking in there somewhere) and if not, clarification from Lee about what happens if the two GPS sources were both plugged into the PAW at the same time (with presumably very slightly different GPS coordinates)?

Regards

Peter

[Deker]

I have also seen a persistent 'ghost' aircraft follow at a relative position, but this was a number of updates ago and appears to have been fixed for some time.

[jbone]

All,  Thanks!

Peter, Sorry for disappearing (I've been distracted by something else since Monday).   The original PAW GPS dongle (that looks like a datastick), is connected to the PAW by a USB extension.   When I pull the extension out of the PAW, it loses position.   Maybe if I booted it up with that disconnected, it would 'find' the one that looks like a mouse.   I will try that when I put it back in the aircraft.  I've also done the sortware update, so hopefully  one of these changes will fix it.   I confirm there is no other EC on board apart from the Garmin GTX328.  It looks as if it's going to be a few months before the next flight, so the acid test will have to wait for a bit I'm afraid.   I've just ordered a Skyecho, so I'll have some fun setting that up too.

Thanks for the help, John

[exfirepro]

Hi John,

Thanks for the reply and OK on no other EC devices installed in your aircraft.

You stated previously that when you unplug the USB extender your unit loses its GPS position fix and in an earlier post that ‘disconnecting the ‘mystery’ mouse does NOT cause loss of GPS signal’.

With the PAW Classic, 3 of the 4 USB ports should normally be in use, with the small black WiFi dongle, the 1090MHz SDR (the larger black one with the thin antenna cable coming out of the end) and either the USB extender cable with your original ‘UBlox’ GPS plugged into the other end or the cable from the GPS Mouse (but not both). That means that the 4th USB port should be empty (unless the cable from the GPS Mouse has also been plugged into it in error - which is simply what I am trying to establish).

If not, I am at a loss to think what you ‘disconnected the ‘mystery’ mouse’ from? Clarification of this point may help us solve the mystery of your ghost.

Best Regards

Peter

[jbone]

Hi Peter,  Yes, both GPS antenna were connected at the same time (all 4 USB ports on the PAW were in use).  This stems from me being confused and thinking the larger one was a Flarm antenna.  I will remedy that before I fly again and hopefully that will be it sorted.  Thanks to everyone for the help!   John

[exfirepro]

Hi John.

Thanks very much for that clarification. That makes the situation much clearer. No criticism from me as to connecting both units, I fully understand your confusion.

Hopefully Lee can now advise whether that is likely to have been responsible for your 'Ghost', though I'm not sure he will ever have tried that scenario - I know I certainly haven't , but I can do so locally to see what happens if required.

Once again, thank you for being so frank and open.

Best Regards

Peter

[Admin]

Hopefully Lee can now advise whether that is likely to have been responsible for your 'Ghost', though I'm not sure he will ever have tried that scenario - I know I certainly haven't , but I can do so locally to see what happens if required.

This would not cause a ghost to appear
The issue is most likely a misconfiguration of ICAO code
I think we need to wait for John to provide the settings to determine this

Thx
Lee

[jbone]

Lee, what do you need please? 

[Admin]

Hi John

apologies, I was going to ask for Screenshot of PAW Configuration screen, just gone back through thread and see you did post that previously.

In which case, simply a Track file of any flight where a ghost was seen should be sufficient

thx
Lee

[exfirepro]

Hopefully Lee can now advise whether that is likely to have been responsible for your 'Ghost', though I'm not sure he will ever have tried that scenario - I know I certainly haven't , but I can do so locally to see what happens if required.

This would not cause a ghost to appear
The issue is most likely a misconfiguration of ICAO code
I think we need to wait for John to provide the settings to determine this

Thx
Lee

Hi Lee,

Like you, my first thoughts on reading this thread were that there must be two or more devices - one of which had the wrong Hex ID, but John reported having only his PAW Classic and Garmin GTX328 transponder and that both were running the correct Hex ID. This was borne out by subsequent screenshots and the fact that Mode-C/S and Mode-S/3D were both disabled seemed to rule out the transponder.

The mention of a FlarmMouse, however, raised the possibility of a second ‘positional’ device, especially as they are (as you know) habitually supplied coded with a non-ICAO ID, which would clearly cause this effect, though I was very sceptical as I could see no FlarmMouse, merely a Mouse GPS (as has since been confirmed). This leaves only the PAW Classic and John’s Garmin GTX328 transponder in the Aircraft.

As stated above, I had already discounted the transponder, as from John’s Configure Screen, he also clearly had both Mode-C/S and Mode-S/3D disabled in his PAW Classic, though in hindsight this of course also means that the transponder filter is (presumably) not selected.

Realisation of this made me reconsider the GTX328, but not being familiar with it I have googled it and managed to find and download copies of the Installation Manual and the Pilot’s Guide (from 2007, so not necessarily the most up-to-date versions, but the best I could find).

From these, it is obvious that the GTX328 is a sophisticated unit, with a very complex setup procedure. It is, however, reported as being incapable of broadcasting (or being converted to broadcast) Mode-S/ES (ADS-B) though it does transmit Mode-S acquisition squitter replies about once per second whether [external] interrogations are received or not.

It also appears to be the case that the GTX328 can be programmed to transmit both its ICAO Hex ID AND a separate ‘Flight-ID’ which - depending on the configuration at the time of installation, may be the normal Aircraft Reg OR a variable Flight-ID (e.g. for commercial use) ‘which may be the aircraft registration number or other call sign’ - configurable by the Pilot and changeable prior to each flight, though the manual states clearly that this can only be done if the unit is configured at installation by the installer to enable the user to alter the Flight-ID. The Pilot’s Guide makes no mention whatever of setting a Hex ID and this is covered solely by the Installation Manual.

Having read through the entire manual, it seems that depending on how the unit was configured at the time of installation, it would be possible to get to a situation where the unit was transmitting two different ID codes, though even if this were the case, surely it would only display as a Bearingless target and not a known position target - or am I way off the mark in that assumption?

I would certainly recommend that John updates his PAW as a matter of urgency to 20201101 and enables ‘Mode-C/S + Filter’ with realistic Range and Altitude Settings and ‘Mode-S/3D’

The plot thickens.

Best Regards

Peter

[jbone]

Peter,  Yes, that's right, the GTX 328 is a mode S, non-ABSD transponder (incapable of being upgraded to ADSB - don't get me going!).   It is programmed with just the HEX code in (I uploaded a photo previously).

The question for me is "what has changed".   I have flown, probably well over 100 hours with the PAW set up like this with no problem) then suddenly I get this problem.  Since nothing in the aircraft has changed, I initially assumed it was something external. The answer might lie in the following:

Lee,  there problem was the last time I flew the plane.   There is no track file for the flight.   There is a file for the previous flight and files from when I've been recently fiddling around with it on the ground, but nothing for the approx 90 minute flight where the ghost appears.  Weird!

I'm not sure we are going to get much further.  Why don't we wait and I'll report back when I next get to fly (although that could be a while)?  thanks everyone, I'm very grateful for the help, John

[exfirepro]

Hi again John,

Yes, I guess we’ll have to wait to do more flight testing. VERY frustrating for me too as we have lots of new stuff to test as reported elsewhere. Main priority however (having got this far) is to avoid catching the dreaded bug at this late stage until our turn for vaccination comes round!

One minor ‘gap’ in the evidence that has been rattling at the back of my head is the question of your USB Port Settings. They are presumably default, and may have no effect whatsoever, but the fact that they are not visible on the screenshot of your Configure Screen you posted earlier just makes me wonder. As your aircraft is ‘home-based’, could you please (at your convenience) take and post a screenshot showing the whole of the Configure Page with your current settings - to complete the evidence picture. I would appreciate it. No rush and Stay safe!

Best Regards

Peter

[jbone]

Peter,  I learned my lesson and kept the PAW unit here on my desk!   Here is the screenshot.   By the way, I have updated the software on a fresh SD card, but I put the old SD card back in for the purpose of taking this screenshot, so it would be on the old software (just to reduce the number of variable).  thanks, John

[jbone]

Just to close this thread off.  Now I've been able to fly for a little while now, the 'ghost' aircraft has vanished.   I've no idea why; it's just been one of those things.  thanks to all who helped.  John

[exfirepro]

Hi John,

Thanks for the update. I’m still puzzled by the reasons for the problem as we have still never identified a definite cause. There are certainly no issues with the USB Port Settings. You say the new updated software/card appears to have resulted in your ghost ‘going away’, but I know of nothing in the update that would have caused that result.

Let’s just hope the ‘exorcism’ proves permanent, whatever the cause