PilotAware shows Ghost Traffic

[Deepstall]

Hello together!
I've been using Pilotaware for nearly one year.
When I am in flight i often get Traffic Alerts as "Traffic Danger" level or +/100 ft when there is obviosly no traffic. The traffic has the call sign "C-0E01" or similar as you see in the attached pic. I am using the C/S plus Filter mode.

Are there any Ideas to solve this Problem?

Best regards from Germany.

Lars St.

[Admin]

Hi Deepstall

This is most likely your own transponder, the 'C' indicates a ModeC reception, which cannot be filtered automatically because it contains no identifier.

Firstly which version of PilotAware are you running ?

This scenario can happen for 2 reasons
1. During steep ascent/descent
this does not appear to be the case for you.

2. Whilst first coming in to range of ground interrogation
This seems most likely in this case.
Mode-C contains no identifier in order to know this is not your own transponder.
So PilotAware has to 'learn' from your own transponder, this is done by monitoring the highest power Mode-C at your height and ignoring this when it remains constant.
If you are not interrogated for a period of time, then this filter gets dropped - when you are interrogated again, PilotAware has to re 'learn' the signature from your transponder.

Does this sound likely ?

Thx
Lee

[Deepstall]

Good Morning Lee,

thank you for the fast answer.
Yes of course, this seems to be a good explanation.

I disregarded that my Transponder is still transmitting a Mode C Signal when oparated in Mode S.
I got similar warnings a time ago, when i got a wrong call sign in the Mode S Filter, this was my own Transponder, too.

What proves your Statement is, that i first got this problem when climbing out after departure. But at that time i thought this could be a signal from a plane on the ground.

I updatet to 20180129 a month ago. But the indication was still there in the former Version...

I will watch for this in my next flights.

Best wishes!

Lars




 

[exfirepro]

Lars,

Fairly extensive 'fixes' / 'improvements' were added to the software last year to deal with this specific issue and improve Mode C detection generally. These have been continued in the most recent 20180129 release, so if you are now running this version the issue should disappear. If it doesn't, please let us know.

Regards

Peter

[Admin]

Hi Peter, Lars

The one thing you cannot get around is the very first detection

So imagine you are climbing out of your home airfield, you are then just high enough to get interrogated from a RADAR.
At this point, this is the first detection of your own (Mode-C)  transponder, this first detection does 2 things
1. Generates a warning
2. Sets the filter (when in Mode-SC filter mode)

Subsequent interrogations will then be filtered, but not the initial interrogation

I have thought about an algorithm that checks an increasing level (at a specific height) - which indicates an approaching aircraft, versus a ramped signal from 0 to N, where N is some large strength, such as the scenario above.

This however is also fraught with the issue that a (danger) traffic target may also have been interrogated for the first time, which absolutely should generate a warning.

Mode-C is a real pain, but we have to deal with what is out there right now

thx
Lee

[a.alexeev.p]

Was about to ask same question actually... traffic danger 100-800 feet below occurred quite a few times today whereas I am almost certain there was nobody there. My transponder was ADSB... I can’t have ADSB and C at the same time, can I? G-OOMA on flightradar if this helps. Not an expert at all on transponders so might have missed something. Would really appreciate any help.

HEX code set both in configuration and in Sky Demon. Software from January 29 2018. I use the audio cable into headset so those warnings are particulalry scary sometimes 😂

[Ian Melville]

I used to fly G-OOMF, which I am told was Aussie for Get Out Of My Face, wonder what the 'A' stands for 😀

Where you climbing or decending?

[Admin]

In answer to the question, yes adsb and modec will operate together
If you are interrogated, your transponder should respond to any requests
A/C/S

Thx
Lee

[a.alexeev.p]

don’t think I was climbing or decending and that was about 10-15 minutes after departure. Interestingly I don’t think I had that alert when tried to play the recorded track after the flight but might be wrong

Oh, I thought transponders on aircraft are either C S or ADSB, didn’t realise they can be installed same time. Will go read up ob this noW:)

[rogerabc]

Today was my first flight after updating and there were 5 or 6 of these +/_ 100' alerts & warnings spread throughout a 30 minute flight.

None during the previous 15 hours using previous software version.

They do unfortunately undermine the system.

Is there any change to the code?

Regards,

Roger

[Admin]

Roger
Can i have your track file 
Thx
Lee

[rogerabc]

Yes, thanks.
Should be with you tomorrow evening.