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Old June 1st 21, 01:22 PM posted to rec.aviation.soaring
Dan Daly[_2_]
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Default Flarm Target direction

On Tuesday, June 1, 2021 at 1:15:57 AM UTC-4, wrote:
Earlier in the year I had a close call, the Flarm was going off with multiple targets most of which I could visually identify. One I did not see, we both had to turn sharply left to avoid a straight on collision.
Apparently Flarm calculates the potential collision taking into account all directions of movement including turn radius. If I had the Flarm view on the S100 set to the correct zoom I most likely would have picked up the circling glider heading my way. Same possibly goes for the other glider.
Accepting the Flarm view may have shown the exact position of the target, when it switches to the warning mode is it still pointing to the target or the potential collision point?
To clarify I was flying straight and level the target was in a thermal, probably banked 30deg turning left.
Cheers
Anton L


I can't speak to the FLARMview (you might try reading the manual), but from the Butterfly Display, it says in "Traffic Warnings":
"The warning-screen shows the viewing angle to the most dangerous collision threat. A
compass-style indicator gives information about the horizontal viewing angle to the threat."

In addition, the FTD-012 Interface Control Document (version 7.12, July 2019), page 20, speaking on PFLAA sentence (data on other proximate aircraft), says it delivers " Relative position in meters true north from own position... Relative position in meters true east from own position... Relative vertical separation in meters above own position. Negative values indicate that the other aircraft is lower.")

So, it points to where the threat currently is, which makes sense, because it gives a direction for you to look in. If it pointed to where the threat will be, there will be nothing there.

I am interested why you both turned left. I was taught that aircraft approaching head-on both were required to alter course to the right. Perhaps it's different where you fly.