PilotAware
British Forum => Technical Support => Topic started by: dh87b on October 09, 2017, 02:40:41 pm
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Yesterday I was alerted to traffic dead ahead, very close at -100ft. I turned right immediately and did some weaving to look for the traffic, but none was seen. A few minutes later I landed at destination. Some 5 mins later, the registration of the aircraft that was subject to the alert landed at the same airfield. We spoke and decided that although his registration was the one on the alert, there was no way he could have been that close to me and we have since swapped SkyDemon tracks, which seem to confirm this.
On my way home, just about to enter Norwich CTZ, I got another alert and grabbed a screenshot - there was clearly no traffic that close to me, so I'm wondering if this is ghosting or what...
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Hi
Yesterday I was alerted to traffic dead ahead, very close at -100ft.
What type of warning was this, Audio, Visual, Bearingless(ModeS/C) or Positioned(ADSB/P3I) ?
and when you say 'very close' not sure what you mean
We spoke and decided that although his registration was the one on the alert, there was no way he could have been that close to me and we have since swapped SkyDemon tracks, which seem to confirm this.
Can I have the PilotAware track file for the flight, and the Registration of the other plane
On my way home, just about to enter Norwich CTZ, I got another alert and grabbed a screenshot - there was clearly no traffic that close to me, so I'm wondering if this is ghosting or what...
Again, please be specific as the type of alert as above
thx
Lee
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G-CIJO is my plane and I was indeed en route from Cromer.
I will have a look at my Skydemon track.
Anything else I can do?
Brian
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Hi dh87b,
If you were a biplane out of Cromer I saw you take off and climb out. I was in loose formation with another flexwing microlight, we had intended routing round the coast to Kings Lynn. However it wasnt looking good and we decided to route straight back to Sandy. I was visual with you as you slowly gained on me on my right and passed in front. There was no danger of a collision as you were visual to me and I was giving way to let you pass in front.
Regards Brian
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Looking at the RADAR view (bottom left) it looks like G-CIJO (Brian) is about 1km away
Is that what we are referring to ?
I am still not sure whether the issues were positioned or bearingless
Thx
Lee
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That would be my take on it as well, though I don't remember having an audio warning. Well aware the plane was there but not close in my estimation.
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The quote re the first alert.....
Yesterday I was alerted to traffic dead ahead, very close at -100ft.
....doesn't imply a bearingless target, but it could have simply been a misinterpretation of a mode S alert as the 'Aircraft Reg -0.1' banner would appear on screen by default in your 12 o'clock though the aircraft could of course be anywhere through 360 degrees. If it was a 'bearingless' target, 'closeness' could also be misinterpreted by the size of the warning ring, depending on the Mode CS Range setting being used. We really need you to come back on and clarify exactly what type of alert it was and/or provide the track log for analysis.
The second alert (from Brian's aircraft) is clearly a P3i alert (viz the # brackets round the registration). From Brian's account and the evidence of your own screen grab, this was definitely genuine. You probably didn't see Brian on your left due to deteriorating Vis and because Brian effectively passed behind at almost the same level, though I would have expected you to have got alerts much earlier than when you took the screen grab. The distance on screen by the way can be easily misinterpreted - from the 'on screen' scale, Brian was the best part of a mile behind (centre to centre) at the time the screen grab was taken. A case of needing to learn to 'trust the device' and believe what it's telling you - even (especially) when you can't actually see the 'contact'.
Regards
Peter
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Sorry to be slow to respond...there have been lots of husband duties of late ::)
When outbound from Cromer as per the screenshot, I was visual with both flexwings (Brian, and indeed I waggled my [4] wings as I overtook you, to indicate I'd got you both in sight) - I had continued towards Felbrigg House before turning left so that I could be adequate clearance from you both - I trust that was OK. I think the appearance of the CIJO alert only made itself known once I'd gone past the flexwings - which presumably could be something to do with my PAW antenna position...
Lee, I think you've answered my question, because in reading your replies carefully, I begin to understand a bit more about how PAW works. The aircraft on my inbound flight to Cromer was G-CCZD - I don't think I can attach the track file as it's 5.2Mb and apparently I can only attach 512Kb? I don't know what kind of contact it was - I don't recall an audio warning and I'm not sure of the difference between the other types of warning. The pilot of 'ZD said he had an ADSB output if that helps. By very close, it looked less than a mile at 12 o'clock (and stayed at 12 o'clock when I started the lookout weaving turns, so I'm guessing bearingless). So in fact, if he was a bearingless target, he could have been anywhere, as well as dead ahead, yes?
Regards,
Dave
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Dave,
ADSB and PilotAware P3i both show as moving aircraft on your screen - as per the ones on your screenshot. If you have the Pi Audio connected, this type give specific direction based alerts in the form 'Traffic, x o'clock, y Km, zz Ft Above or Below'.
Mode C or Mode S aircraft are known as 'Bearingless' targets, because we can't determine their location or 'bearing' from our own aircraft. This is determined by Radar units from the bearing of the radar head and the time taken for the transponder response to reach it. All PilotAware can do with this type of alert is advise on the presence of such an aircraft by showing a coloured warning 'ring' around your own aircraft, together with the relative altitude- which we DO know from its transponder transmission - displayed in or near the 12 o'clock position on the edge of the current 'ring' together with either the term 'Mode C' or in the case of a Mode S, the Aircraft Reg, which again we can obtain from the transponder. The colour (Green, Yellow or Red) and size of the ring helps denote the level of perceived risk, based on the strength of the signal your PAW is receiving from the other aircraft. This is regulated (modified) by the Mode CS Detect 'Range' filter you have selected in PAW 'Configure'. If you have the Pi Audio connected, this type of alert takes the form, 'Traffic Notice', Traffic Alert' or 'Traffic Danger' as the degree of perceived risk increases.
Until users get used to the form of Mode C/S alerts, it is easy to confuse the presence of a ring with either 'Mode C' or an 'Aircraft Reg' and the size of the ring as indicating the position or distance of the target, They DO NOT !! They are merely intended to prompt the direction of scan (i.e. above or below you) and advise on whether the risk is increasing due to the target getting closer. For this reason 'Bearingless Target Detection' is set to 'Off' in new units by default.
The fact that the pilot of G-CCZD said he had ADSB out would mean he should have shown up as a 'moving aircraft' long before getting that close to you, so it may in fact have been another aircraft altogether that triggered your first alert.
It would help us understand what was going on if you could post a screengrab of your PAW 'Configure' screen or confirm your present settings.
The 'normal' method for transferring large files such as Track Logs by the way is by using 'DropBox' and posting a link on here to the file, or PM'ing the link direct to Lee. If you don't know how to do this we can help you.
Best Regards
Peter
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I was flying G-CCZD that day and can confirm that the ADSB was functioning correctly.
At the time of the reported alert, we we some 15 miles west of the OP at around 5000ft and travelling eastwards at some 150kts. We continued in an essentially staight path descending along the way to join the circuit and land at Cromer about 4 or 5 minutes after the OP, so not quite catching him up along the way but flying a similar track at an overtake speed of around 60kts.
We did not see anythng ( even bearlingless) on PowerFlarm from him because either he was only outputting Pilotaware rather than mode c or s ( I cannot remember if I asked if he had transponder on board) or more likely, because he was still some 6 miles or so ahead of us when he landed.
We have PowerFlarm and Trig TT21 taking the gps from the Flarm for ADSB feed.
I am away from my office at present but could upload a flight log to dropbox on my return if that might be of some help.
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You should get a PilotAware, then you could see the rest of us! ;)
And you can connect the PowerFlarm into it, so you'd get the lot.
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Can I just query something about PAW settings?
All is working well with ADSB and PAW equipped aircraft. I have my device set to the Mode C/S Filter Beta but all I am picking up is Mode S equipped aircraft.
Is this what others are experiencing, or am I just unlucky. Looking at my flight log from Monday and also the log from the Popham end of season Flyin, although there were Tx equipped aircraft about, I saw very few on SD or in the log.
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Is this what others are experiencing, or am I just unlucky. Looking at my flight log from Monday and also the log from the Popham end of season Flyin, although there were Tx equipped aircraft about, I saw very few on SD or in the log.
Hi Peter
Mode C will only appear on SD if it is deemed a threat.
If you want to check if the ModeC reception is working, then simply look at the traffic page, this will list all targets, but will only forward to the NAV device if the power level surpasses a threshold.
Also, can you confirm you are using the current latest version 20170721
Thx
Lee
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Peter, you may also want to check that SD has 'Show Bearingless Targets' toggled on.
Settings>Navigation Options>(Scroll down to 'Other Traffic' options set)
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Thanks both
Yes I am using the latest PAW version and 'bearingless targets' is on. Obviously there is a difference between Mode C and Mode S signals, but are you saying the threat levels are treated differently with Mode C or Mode S?
I've checked the logs on the days in question but only Mode S equipped (or ADSB-OUT or PAW) show up when I know I was close to Mode C squawking traffic. I'm flying later in the week and will check again
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You should get a PilotAware, then you could see the rest of us! ;)
And you can connect the PowerFlarm into it, so you'd get the lot.
Not a bad idea Paul and one that we will most likely do soon.
However, as far as I can see no one has answered the OPs' query as to why he was seeing us labelled up close to him and at a similar height, when we were transmitting ADSB-out from fifteen or more miles west of him and some 3000 ft above.
Ideas?
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Do you both have GPS tracks to maybe send to Lee and has the OP sent the PilotAware log?
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I'll pop mine over when I am next in the office but that will not be until 13th Nov.
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Paul,
Dave did try to attach the track log to a previous Forum post, but of course it's far too big. I did suggest using Dropbox, but he may have missed my suggestion, or not know how to do so. If this is the case Dave, please get back in touch.
However, as far as I can see no one has answered the OPs' query as to why he was seeing us labelled up close to him and at a similar height, when we were transmitting ADSB-out from fifteen or more miles west of him and some 3000 ft above.
Ideas?
Without the track log(s), it is very difficult to answer this. In my years of testing, I have NEVER experienced a 'false alert' from a known position aircraft and have only ever heard of two instances (IIRC in the Project Eva Trials Report) where due to a technical issue, one of the aircraft was transmitting its position as the wrong side of the Greenwich Meridian.
The only way we will be able to resolve this issue properly is to look at Dave's PilotAware Track Log, however re-reading the thread yet again, the following points are clear.
Firstly, Dave says of the first alert on his 'inbound' flight to Cromer [My Edits....]
The aircraft on my inbound flight to Cromer was G-CCZD... [ - ]... it looked less than a mile at 12 o'clock (and stayed at 12 o'clock when I started the lookout weaving turns, so I'm guessing bearingless). So in fact, if he was a bearingless target, he could have been anywhere, as well as dead ahead, yes?
Regards,
Dave
The fact that the 'indicator' stayed at 12 o'clock on Dave's screen while he carried out his clearing turns indicates fairly positively that what he was seeing was a bearingless contact indicator. If this had been a known position aircraft (P3i or ADSB), it would have moved round on the screen away from the 12 o'clock position as Dave turned his aircraft (the amount of movement would of course depend on how big / prolonged the clearing turns were, but nevertheless the contact would have moved to some degree). It's also correct that a bearingless aircraft 'could' have been 'anywhere' [round 360 degrees, at the relevant altitude indicated on screen] as well as dead ahead.
A fault with G-CCZD (if for example the PowerFLARM temporarily stopped sending GPS data to the transponder), would cause G-CCZD to (temporarily) revert to Mode S, however it is unlikely that Dave would receive a bearingless target 'Alert' from G-CCZD's Trig TT21 at 15Km. Even if Dave was running Mode C/S Detect on 'Long Range', aircraft normally need to get much closer than this before bearingless target alerts start to appear on screen - except in the case of CAT aircraft running high power transponders!
Is it possible that what Dave saw was a bearingless alert from a CAT Mode S (e.g. Flybee) at long range and somehow confused this with the ADSB alert from G-CCZD, which would have been easily visible at this range, ....or was there a temporary fault on G-CCZD's transponder? Only a hypothesis, and no disrespect or criticism whatsoever intended or implied to either Dave or G-CCZD, but without seeing the log(s), these are the only explanations I can think of that make any sense whatsoever.
As I say, the logs will reveal all - if you can get them to Lee, Dave.
Regards
Peter
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All understood, thanks ( and absolutly no need to worry about airing possible failures, we are all here to learn).
Pretty sure our ADSB was working at the time for two reasons:
1) In the event of loss of gps, the Trig flags up an ADSB error message on the screen and we saw none.
2) I reviewed the Flarm .igc trace after the event and it shows solid gps logging all the way on that flight.
As I mentioned earlier, I shall send the trace ( via dropbox) on my return to the office next week.
PS range at the time of reported hiccup was in region of 15Nm ( not km), not that it makes much difference other than it being even more unlikely that Dave would have seen a TT21 pure Mode S alert at that range.
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Thanks for the update. All understood. Hopefully we will get to the bottom of this soon ???
Regards
Peter
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Thanks both
Yes I am using the latest PAW version and 'bearingless targets' is on. Obviously there is a difference between Mode C and Mode S signals, but are you saying the threat levels are treated differently with Mode C or Mode S?
I've checked the logs on the days in question but only Mode S equipped (or ADSB-OUT or PAW) show up when I know I was close to Mode C squawking traffic. I'm flying later in the week and will check again
Peter G,
The main difference between Mode 'S' and Mode 'C' is the lack of a 'Hex' identifier linking the data in the Mode C transmission to a specific aircraft. When we first started reporting Mode 'S' on PilotAware, it was 'relatively' easy to use the Hex identifier transmitted as part of Mode 'S' to establish which data was coming from which aircraft. Unfortunately, Mode 'C' transponders, don't transmit a Hex address, so we have to 'analyse' all altitude responses from bearingless aircraft very carefully (and for a bit longer) to establish whether they come from a Mode 'C' transponder or are a Mode 'C' 'altitude' response from a Mode 'S' transponder (for two aircraft at the same altitude, the transmitted data packet is the same). Once identified however, 'threat levels' between Mode C and Mode S are treated exactly the same - but at any point in time SkyDemon can only display one bearingless target presenting the highest perceived threat. Also, although the targets all appear on the PilotAware Traffic Screen, threats will only be passed to the Nav device if within your chosen PilotAware bearingless target altitude filter range (show within vertically) and dependent on your chosen Mode C/S Detect 'Range'.
Remember also that Mode C transponders only transmit in response to an interrogation from a Radar Head or aircraft TCAS system, so won't transmit if out of radar coverage.
Regards
Peter
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Thanks for that. It shows how tricky things are for you.
Peter
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Hi Dave,
Lee, I think you've answered my question, because in reading your replies carefully, I begin to understand a bit more about how PAW works. The aircraft on my inbound flight to Cromer was G-CCZD - I don't think I can attach the track file as it's 5.2Mb and apparently I can only attach 512Kb? I don't know what kind of contact it was - I don't recall an audio warning and I'm not sure of the difference between the other types of warning. The pilot of 'ZD said he had an ADSB output if that helps. By very close, it looked less than a mile at 12 o'clock (and stayed at 12 o'clock when I started the lookout weaving turns, so I'm guessing bearingless). So in fact, if he was a bearingless target, he could have been anywhere, as well as dead ahead, yes?
Finally got time to investigate.
I can tell you this aircraft did come close to you, the closest he came was here
$PFLAA,3,149,-559,151,1,404B40!GCCZD,32,,49,1.5,8*79
$PFLAA,3,211,-522,150,1,404B40!GCCZD,34,,49,1.5,8*7C
$PFLAA,3,253,-498,150,1,404B40!GCCZD,36,,49,1.5,8*78
$PFLAA,3,285,-474,150,1,404B40!GCCZD,40,,48,1.5,8*71
$PFLAA,3,330,-439,150,1,404B40!GCCZD,42,,48,-1.5,8*58
$PFLAA,3,334,-444,151,1,404B40!GCCZD,44,,48,-1.5,8*51
$PFLAA,3,414,-373,151,1,404B40!GCCZD,46,,48,-1.5,8*55
$PFLAA,3,449,-338,143,1,404B40!GCCZD,47,,47,-1.5,8*5F
$PFLAA,3,482,-313,151,1,404B40!GCCZD,47,,47,-1.5,8*52
$PFLAA,3,514,-273,143,1,404B40!GCCZD,52,,47,-1.5,8*5C
$PFLAA,3,547,-232,143,1,404B40!GCCZD,55,,47,-1.5,8*58
$PFLAA,3,553,-234,143,1,404B40!GCCZD,55,,47,-1.5,8*5B
$PFLAA,3,599,-171,143,1,404B40!GCCZD,57,,47,-1.5,8*5D
The fields are
PFLAA, <Threat>, <Metres N>, <Metres E>, <Metres Above>
so for example
$PFLAA,3,334,-444,151,1,404B40!GCCZD,44,,48,-1.5,8*51334 Metres North
444 Metres West
151 Metres Above
I think PilotAware was doing its job correctly, if it helps, this was your GPS Position at the time
$GPGGA,122901,5253.557,N,00119.023,E,1,10,0.9,60.4,M,45.8,M,,*76
Paste the above into here
https://rl.se/gprmc
If you have a specific time for when you thought there was a threat I could take a look at that moment.
I also saw some ModeS Warnings of less than a 50ft below for GRVUK
$PFLAA,3,1500,,-12,1,405020!GRVUK,,,,6.1,8*30
$PFLAA,3,1500,,-14,1,405020!GRVUK,,,,6.1,8*36
$PFLAA,3,1500,,-14,1,405020!GRVUK,,,,0.0,8*31
$PFLAA,3,1500,,-16,1,405020!GRVUK,,,,0.0,8*33
$PFLAA,3,1500,,-17,1,405020!GRVUK,,,,0.0,8*32
this generated audio messages (if you are connected)
$PALOG,405020,AUDIO,MODES,,,189*60
your position was here when this threat was raised
$GPGGA,121735,5257.118,N,00102.552,E,1,09,1.0,244.4,M,45.9,M,,*4B
Thx
Lee
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Lee,
Thanks for looking into this.
However, I have some doubts that this bit of the flight is where the initial reported in flight conflict/ warning occured
I certainly did come close to him at the location indicated above and would hope that it would have generated the report you highlighted - because, if I am reading it right, that was at Cromer airfield where we both landed( and the time coicides with his final approach and touchdown as I entered the circuit at around 600ft under low cloud - the time matches Dave landing and my touchdown some two minutes later.
His inital report ( as described to me by Dave himself) of the in flight conflict alert was some minutes earlier than that when he was west of Cromer at around 1000ft agl and I was some fifteen miles further west than that and quite likely several thousend feet higher than him.
Ishall send my file to you tomorrow in the hope it might help.