I don't think anyone would maneuver in response to the alert, they would
maneuver in response to what their eyes told them when they looked at the
threat in response to the alert.

Bill Daniels

"Andy Blackburn" wrote in message
...
I can think of ways to filter for only the most proximate
threats, even in a gaggle (closest proximity, closing
rate, etc). What seems to me would be difficult in
a gaggle setting is figuring out what to do once everyone
starts maneuvering in response to alerts - it could
quickly get overwhelming.

Even so, more information is likely better than less
under most circumstances.

9B


At 21:12 03 May 2004, Eric Greenwell wrote:
303pilot wrote:

'Eric Greenwell' wrote in message


Ony if you think the problem is 40 gliders instead
of 3 or 4, which is
all that was involved in the recent collisions.


I'm not a programmer, but I work with them on a daily
basis. It seems to me
that even a 3 or 4 glider problem is highly complex
because sailplanes fly
in highly irregular paths.

But still more manageable the 40, right :} ? But to
answer the
question, and keeping in mind I don't know any details
of the Flarm
system, it may not be possible or necessary to have
a TCAS-like system.
Though several gliders flying at random may indeed
be complex, the
algorithms chosen can make simplifying assumptions
based on the nature
of glider flight. Also, the pilot arriving at a thermal
might modify his
arrival to keep the threat level low, compared to how
he does it now, so
as not to 'alarm' the pilots already in the thermal
(and for other
situations, also, not just thermals).

We don't even fly straight point to point--we
weave left and right, we dolphin. A ship might be
going (more or less)
straight and a couple hundred feet below me. Not
a threat, right? Maybe,
maybe not--what if I'm in a thermal and he's seen
me and plans to join me.
He suddenly converts speed to altitude and he's in
my blind spot. My GPS
has a 4 second polling cycle. Ooops.

Most GPS receivers we use emit at once a second, though
_flight
recorders_ might record at a slower rate (the newer
ones will also
record at once per second). Rate isn't a problem.

What if two ships are in a thermal but maintaining
separation. Everything's
fine, right? Sure, until we get to the top of the
lift band and he suddenly
tightens his turn to go through the core as he heads
out on course.

This simple situation is likely easy to handle. It
should cause some
alarms in both cockpits, unless it is a diving exit,
which would put him
well below the still thermalling glider!

I'm sure anyone contemplating these systems has thought
of these
situations and more, and intends to cope with them,
and use extensive
testing to validate the equipment. As I mentioned before,
the equipment
might cause changes in pilot behavior, perhaps because
they wish to
avoid causing alarms, or because they now realize better
the dangers
involved.

Have you ever flown in a thermal with even 10 gliders?
I have many
times. I can not keep track of even 10 gliders, but
I can still thermal
safely when there are that many and more. We are not
flying around at
random, but circling in an orderly fashion. Only the
nearby gliders are
a threat that must be monitored. In any case, a system
that deals with
only a few gliders will cover most of the situations.

Orderly? To you and I yes. To a program? Not really.
Think about what happens at cloudbase in a contest
gaggle. The (mostly)
orderly and similar actions (mostly same speed & bank
angle) get more
random. Some pilots increase their radius purposefully
suboptimizing climb
rates, others deploy a bit of spoiler, others leave.
How are these actions
to be predicted?
Even if I have a 1 second polling rate on my GPS &
'traffic
analysis/collision avoidance system', how many variables
can change in that
one second and how fast can my safe separation be
erased?

In one second? Very few. Gliders simply don't react
quickly in roll, and
pilots don't pitch rapidly in the cloudbase gaggle.
The ones I've been
in, everyone is changing direction smoothly and slowly.
Away from a
gaggle, pitch changes can occur rapidly, but one second
still seems
short enough to me. It would be better to seek the
opinion of someone
actually attempting this, of course!

snip

What must we do? Propose something - we're listening.


Here's my modest proposal, eat them. Sorry, trying
again--
Don't ask the system to figure collision potential
and don't introduce
another screen. Just have a system call out 'target
NNW, same altitude,
closing @ x'. If I see it, I say something like 'clear'
or 'check' and the
system stops alerting me to the known target. If
I don't acknowledge the
target the system continues to provide information
at regular intervals to
help me find it.

If I were designing a system, I'd make this capability
the first phase.
Perhaps it would be good enough. I'd try a button on
the stick before
the confirmation.

I might be re-notified of 'cleared' targets if we
continue to fly in
proximity to one another.
Frankly, I can't imagine a user interface that would
be useful in a large
gaggle. That's probably OK because that's where we're
likely to be most
alert to this type of threat.

Brent



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Change 'netto' to 'net' to email me directly

Eric Greenwell
Washington State
USA