Mode-S problem with SkyDemon

[Chris-TT]

Today we took two very short flights, from Kemble to Gloucestershire and back. PilotAware did its job, however the bearingless readings were overlayed in exactly the same location of the screen making all of the information unreadable. I'm fairly sure this is a SkyDemon problem, however it's quite a major problem. Perhaps one to bring up with Tim and the team? It would work much better if bearless traffic information was listed in the bottom left corner, or a custom location rather than overlayed on top of your aircraft.

[exfirepro]

Hi Chris,

One of the difficulties in developing a system like PAW, is that Lee is to an extent at the mercy of the Navigation System Developers, who each have their own ideas as to how information provided by PAW and similar systems should be displayed on their product. SkyDemon for example normally displays bearingless 'FLARM' targets as a 'circle' which appears round your aircraft, but at an early stage it was decided by the PAW Team that this was confusing as it implies a safe zone around your aircraft, at a distance which cannot be determined from a raw transponder signal as it contains no horizontal positional data. Lee therefore changed the information he presents to the Nav System so that it would (at least on SD) show as the small aircraft symbol piggybacked on top of your own aircraft, with the one piece of positional information which is available - namely the relative altitude.

In early Mode S development versions of PilotAware, when this warning aircraft symbol appeared, it changed colour from green to orange to red, to indicate increasing danger (which I really liked), however when Lee later incorporated data to show the Aircraft Callsign/ID on screen, this for some reason prevented the colour change from operating, so we lost IMO a valuable safety aid - which has been replaced at least to an extent by the new audio warnings.

Other navigation systems show bearingless targets in different ways. At least one system (EasyVFR) displays the presence of bearingless targets by a series of 'banner' alerts, similar to what you are suggesting, which appear top left of their screen and which change colour in response to the increasing danger triggers which are generated by PilotAware. I know from discussions that Lee likes this system, as does my fellow tester AlanG, though I personally like to see a warning symbol appear on top of my aircraft as that is the position on my screen I look at most frequently when flying. Perhaps the ideal would be a combination of the little aircraft symbol and the banner warnings, which would resolve the problem of multiple contacts blocking each other out.

Irrespective of our own preferences, however, we need the navigation system developers to engage with 'us' to discuss and agree the best way forward. I know Lee has tried to put this into practice, but so far it appears with limited success. I'm sure he will keep trying.

Regards

Peter R
(Mode S tester)

[Ian Melville]

Though I know it also has limitations, was there not talk about having only the closest bearing-less threat shown?

[Admin]

Though I know it also has limitations, was there not talk about having only the closest bearing-less threat shown?

Hi Ian
I think the issue is determining 'closest', for example, which of these is the bigger threat ?

+100ft signal level 170
+400ft signal level 220

the only 'known' is the altitude difference, the signal strength is fraught with inconsistency,
the A/C at 170 may actually be closer than the A/C at 220 because of the transponder installation
and transponder power output.

Thx
Lee

[Richard]

Could the signal strength be filtered?

+100ft signal level 170
+400ft signal level 170

Which would be the threat now?

Just a suggestion

[exfirepro]

Hi again Richard / Ian

That is sort of how the Zaons operate - by constantly reassessing and presenting what they see as the greatest risk, in this case probably the one nearest to your own altitude. But... as Lee says, due to the considerable variation in signal output - even from the same model of transponder - due to the vagaries of installation in different aircraft (let alone different types), it is extremely difficult to make this call. The one showing at +400ft could in fact be 'closer' and right above you, descending! So not quite as simple as it appears.

That"s why EasyVFR's banner alerts are attractive as they present you with the big picture, from which you can assess, find the contacts and decide what action is most appropriate in your own particular circumstances.

Regards

Peter

[julianwebb]

I've just got my PAW so still trying to learn how it works with SD in terms of what is displayed.

On the Mode S display the circle around the aircraft for bearing less targets is the "standard Flarm" display which all Flarm displays use. I think an aircraft piggy backed on top of ones own aircraft is confusing and sounds a bit like that old Frank Sinatra song "I did it my way" why not just stick to the standard Flarm way as PAW uses the Flarm interface standard developed and tested over many years by Flarm?

I think it opens a can of worms to move away from developed standards particularly when we talk to SD about enhancements if PAW just decides to do its own thing.

I would be a bit alarmed to see an aircraft piggy backed on my aircraft.

[Paul_Sengupta]

I believe Lee will be going back to the rings in the next software version. (we've tried both in the engineering software guise and I prefer the rings)

[julianwebb]

Hi Paul

Sounds good why try to reinvent the wheel when we have developed standards that have been tested over many years. Will also save development time in the software - ie user testing etc.