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Thanks for that Mark. It assists understanding a
lot.
I found it interesting that based on the latter
part of that video, it would be possible to be at the same height and flying
towards (but a tad behind) that other glider ... and not get any warning
unless the tracks intersect or converge ................ and if the
other remains unseen it would be possible to tighten the turn and
converge to get a warning just as they collide.
For some reason I assumed that if you are
constantly getting closer to, but not intersecting with, another Flarm
equipped aircraft, then you would get some type of "heads-up" (poor pun)
warning.
I'm not complaining, mind you, I just want to
understand the way that it operates. It just proves that Flarm is certainly
useful but it is an aid to the "see" of see-and-avoid, but there can never be
any guarantees even if all aircraft are equipped.
On looking at that video again, the LEDs were unlit
during the turn to port and early in the approach to the other aircraft. How
does it indicate proximity as per your 2nd last para?
Regards & thanks for your response
Geoff
----- Original Message -----
Sent: Tuesday, October 25, 2005 2:34
PM
Subject: Re: [Aus-soaring] Zaon Flight
Systems collision avoidance
Geoff Kidd wrote:
> In trying
to understand your explanation, and wanting to fully grasp
> the way
these things work, I looked again at the Flarm video on DG's
> website
http://www.dg-download.de/Videos/flarm-rennes.wmv.
>
In that case the display alarms initially at the 12.30/01.00 LED,
>
which is about where the other glider is, when the tracks of the 2
>
aircraft appear to be intersecting but when there also appears to be a
> reasonable height separation ..... and it looks to me like there was
not
> a "risk of collision".
They were on a converging
heading. The FLARM was essentially saying,
"Even though the
separation is high, if you continue the way you
are at the moment you will
probably hit each other."
Note that the alarm tone was different to
what it was later on when
they were
closer.
> The pilot then bears away to
starboard and turns back to port to fly
> directly at or towards the
other aircraft.
Obviously not directly at it, because they didn't hit
each other.
Unless it's directly in front of you, flying directly at the
position
another aircraft is in *right now* will cause you to miss it,
because
by the time you reach that position the other aircraft won't
be
there anymore.
They were on diverging headings during that phase
of the demo, when
the alarm was silent. They were in close proximity
to each other,
but there was no collision risk, so there was no
alarm.
> It looks to me that there is a
greater risk of collision after he
> turns back to port towards the
other ship when it is visible in his
> screen ........... yet the alarm
doesn't sound again until he is
> reasonably close.
Reasonably
close *and converging*.
There is no mystery to this, Geoff. You
can fly as close to another
glider as you want; but if you're not
converging with it, FLARM won't
bother to sound an alert (it'll still
indicate proximity on its visual
display, but it won't sound an alarm to
indicate an imminent collision)
That's the right answer, isn't
it? Nobody wants a "collision avoidance"
system which chirps
continuously just because you happen to be sharing
a thermal with someone
else, do they? What we really want is a collision
avoidance system
which is silent when you're sharing a thermal with
someone else *unless
you're about to hit each other*.
-
mark
--------------------------------------------------------------------
I
tried an internal
modem,
[EMAIL PROTECTED]
but it hurt when I
walked.
Mark Newton
----- Voice: +61-4-1620-2223 ------------- Fax: +61-8-82231777
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