Anti Collision Warning

Over the last 15 years or so our instrument panels
have become much more interesting, displaying vastly
more information than previously. During the same
period there has been a significant increase in the
number of pilots with the skill (and willingness) to
soar very close to other sailplanes.

The accidents are caused by our willingness to fly
in a close proximity to other gliders, that produces
the level of risk that produces the accidents we have.

A gadget that worked, if such were possible, would
probably have us all flying closer and closer together
until we got back up to the same (maximum acceptable)
perceived level of risk.

At 23:54 01 May 2004, Mark James Boyd wrote:
In article ,
Mike,

The FLARM concept has been painfully obvious, from
a technology point
of view, since the introduction of low-cost GPS. In
fact, it could
even have been partially implemented with LORAN, but
those receivers
were expensive and were never widely deployed.

Unfortunately, FLARM-type collision avoidance is only
going to work if
it's deployed to virtually all aircraft, which would
require the
authorities to insist on it. This won't happen: ADS-B
is the chosen
approach.

Sort of important to this approach is 'is it worth
it?' and
'does the solution cause more death than the problem?'

Kind of like parachutes. If the added weight increases
the
marginal stall speed to the point it causes .001% more
fatal accidents, but only saves .0092% more pilots
in breakups, then it was a bad idea. Of course it's
extremely unlikely anyone can prove the extra 15 pounds
was
the cause of fatality, right?

How many added fatalities will there be because the
pilot
is distracted by the bleepy noise, even though the
aircraft
would have missed by six inches if neither pilot was
aware?
How many will die because of the distraction itself?

This is just too hard to calculate. Huge numbers (hours
of flight)multiplied by tiny estimated numbers (risk
of midair)
makes for a tough comparison. Now instead of risk
use cost in $$$$s to implement, and the true cost vs.
benefit is
very difficult to estimate correctly...

--

------------+
Mark Boyd
Avenal, California, USA

Andy Durbin wrote:
trajectory of each aircraft, but also predict collisions based on all
possible future trajectories for the next say 30 seconds. Try

Say 15 seconds, rather. I think it's useless to predict what will
happen in 30 seconds. Even if concentration is not at its maximum for a
moment, 15 seconds should be more than sufficient to avoid a collision
IF YOU SEE THE OTHER A/C.

resolving that mess when there are 30+ gliders at the top of the same
thermal waiting for a contest start. The false alarm rate would be
unacceptable.

I don't think so. I was at the ``kickoff-meeting'' of FLARM at the ETH
Zuerich, and I can assure you that the developers are very well aware of
this problem and have adressed it. There are algorithms which perform
well in that kind of situation and given that the workload is divided
among all 30+ FLARMs CPU performance is expected to be sufficient. The
developers cited extensive simulations which they did with IGC traces
and it seems that the ``false alarm'' rate was low.

That said, of course I can at the moment only cite and trust the
developers, and a system like FLARM needs to prove itself in practice.
There are too many factors which influence collision probability that
I'd dare a prediction here. But it's an interesting concept and if the
technical/regulatory question marks can be cleared up, we'll soon have
some data on whether it can help reducing accident rates or not.

Kind regards,
-Gerhard
--
Gerhard Wesp o o Tel.: +41 (0) 43 5347636
Bachtobelstrasse 56 | http://www.cosy.sbg.ac.at/~gwesp/
CH-8045 Zuerich \_/ See homepage for email address!

Chris Rollings wrote:
Over the last 15 years or so our instrument panels
have become much more interesting, displaying vastly
more information than previously. During the same
period there has been a significant increase in the
number of pilots with the skill (and willingness) to
soar very close to other sailplanes.

The accidents are caused by our willingness to fly
in a close proximity to other gliders, that produces
the level of risk that produces the accidents we have.

A gadget that worked, if such were possible, would
probably have us all flying closer and closer together
until we got back up to the same (maximum acceptable)
perceived level of risk.

What situations are you thinking of where this would be true?

I don't think it would be true for thermalling together, especially in
contests, as I believe we already fly as close as practical. Flying
closer would make it too hard to maintain safe separation (because of
turbulence, the need to maneuver some, and the inability to hold a
perfect circle), even with a warning device. Possibly, we would even fly
farther apart to reduce the number of alarms (this would likely depend
on the precise behavior of the unit), or because we would realize we
were not as safe as we thought. I believe this requires flight testing
to determine.

Perhaps it would be true for ridge soaring together, but again, maybe
the alarms would actually cause us to maintain greater distance.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

At 11:30 02 May 2004, Gerhard Wesp wrote:

Say 15 seconds, rather. I think it's useless to predict
what will
happen in 30 seconds.

something capable of predicting what a human being
WILL do next whatever the time scale. Now that would
be something.

"Eric Greenwell" wrote in message
...
Don Johnstone wrote:

It seems to me that several people think that the introduction
of technology will be simple, it won't. The problem
is extremely complex.

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. 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.
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.



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?


Still
leaves the problem of how you keep the pilot informed,
display in the cockpit? I don't think so. Having sorted
out all that, what does a pilot do in response to an
urgent warning of collision, turn into another glider
which was not logged as a threat until the sudden evasive
turn was made. Technology might give the warning but
it is the human that has to react.

These are not new questions, so you can be assured that people
contemplating these systems are considering them. Systems do not spring
fully featured and perfect from the mind of an engineer, but proceed
through stages of development and testing. Exactly what problems and
benefits will appear during this process can't be predicted very well.


I personally don't think we have the technology or
expertise to design such a system or indeed the expertise
to put it in a small enough space to fit in a glider
right now, and the cost could be more than the average
glider is worth. I am not saying do nothing, what I
am saying is do something realistic and achievable
now. I have little doubt that what has been proposed
will be with us in 10 years time but it is now that
we have a problem.

I stand by what I originally wrote, humans are the
cause of accidents, humans can prevent accidents. Whether
we have the will to do it is another matter entirely.

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.
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

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



--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

The FLARM device not only provides traffic advisories, it tracks ground
hazards like towers and wires. It's also a IGC logger.

Most handheld computers do several million floating point operations per
second (MIPS) Hundreds of MIPS are available on low power CPU's. That's
enough to compute trajectories on 40+ gliders in the 1/2 second interval
between GPS fixes. Having enough computer power is not a problem.

There are a lot of smarter people than me who could do the programming but
maybe I can help with a flowchart.

Step one: Are there any targets within one kilometer? If yes, provide
count.

Step two: Are any of these targets within + or - 200 meters of my altitude?
If yes, proceed to step three. If not, ignore.

Step three: For any targets within + or - 200 meters of my altitude, is the
slant range increasing or decreasing? If increasing, ignore. If decreasing
go to step four.

Step four: For targets within +- 200 meters and closing, is the relative
bearing changing less than 10 degrees per second? If yes, sound alarm and
provide relative bearing and range. If greater, do nothing.

Step four is a bit of oversimplification, for example, the critical rate of
change for relative bearing increases for closer targets, which would
require a look-up table or formula. Still, this is not a complicated
algorithm.

Bill Daniels


"Eric Greenwell" wrote in message
...
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



--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

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



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

Eric Greenwell
Washington State
USA

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



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

Eric Greenwell
Washington State
USA

On Sun, 02 May 2004 00:19:47 GMT, "Bill Daniels"
wrote:


Yes I do fly in the vast empty skies of the western USA, thank goodness.
However, I'm also a pilot who has survived a mid-air with another glider
while flying in those "empty" skies.

Try to picture this. The little device goes "Beep" and when you look at it,
the 20mm 2-digit LED display says "06" meaning 6 gliders are within one
kilometer. My reaction is to look outside like crazy until I can see all
six. It beeps again and displays 07 meaning that another glider has joined
the gaggle. I look even harder. This uses the "Mark 1 eyeball" to it's
maximum.

Extremely accurate GPS data has nothing to do with this. If the error is
that the 7th glider is really 1.005 Km away instead of 1.000 why would I
care? If a glider joins the gaggle without this device there is a very good
chance I will see him while looking for the others even though the device
does not detect him.

It is not necessary to compute the trajectories of all gliders in the gaggle
to determine those with a collision probability. Those 500 feet above and
below present no danger whatsoever.

Now picture an advanced version. The device still displays "07" but it now
sounds "deedle, deedle, deedle" and an LED at 8 O'clock illuminates meaning
that there is a non-zero probability collision threat at that relative
bearing. The "Mark 1 eyeballs" leap into action and I look over my left
shoulder to see that the other glider will pass clear. Is this a "false
alarm"? Not really. I really wanted to see him if he was that close. I
appreciated the "heads up". The device need only compute probabilities for
those targets near and closing while near the same altitude.

Perhaps the problem is calling this an "Anti-Collision Device" when it is
really a situational awareness aid.

As for battery life, perhaps you noticed the news that a fully IFR equipped
Kestral 17 flown by Gordon Boettger flew 1562 Kilometers in 11:15 from
Minden, Nevada, USA to Steamboat Springs, Colorado. Most of the flight was
in wave above 20,000 feet. Gordon's Kestral was transponder equipped as
well as carrying a lot of other electronics to operate legally in positive
control airspace. Battery capacity didn't seem to be a problem.

The device I'm talking about would weigh less than 200 gms and run on four
AA batteries for 50+ hours. The amount of time spent looking at it will be
fractions of a second and then only when critical information is displayed.

Bill Daniels


"electronically enhanced see and avoid" is what we are really after
here, not a 100% guaranteed collision prevention system.

Nearly all gliders already have a GPS of some sort so part of the
hardware already exists.

For those who insist on greater than once per second updates go to the
Garmin website and look at the new Garmin 16A engine which provides 5
Hz updates. This is however, unnecessary.

As someone said here "the glider you don't see is the one that will
get you".(not necessarily true) An electronic system will help with
this which is why fighters got tail warning radar not long after the
invention of radar itself.

Advocating training or better behaviour by pilots probably won't work.
If it did we'd know by now. The collisions we have are the ones left
AFTER this has already been done. Could some people do better? - yes.

This has been going on for 90 years now. Ask the victims of Manfred
von Richthofen, Billy Bishop, Albert Ball and all the others. Even the
aces got surprised occasionally and survived by luck(Adolph Galland)
or not.

You don't need any display in the cockpit, just a voice.(no panel
space required) Some years ago we owned a Nimbus 3DM and it was
remarkable how often a second pair of eyes would pick up something
that one missed.
The electronic systems like FLARM will provide that second pair of
eyes in single seat gliders.

It isn't necessary to have a 100% system. We already do that with
parachutes and in the military, ejection seats. Neither are 100%
effective.

When the alternative is almost certain death even a 50% mitigator
looks good.

Any National gliding body responsible for regulation could trial such
a system at any given site and then go on to require its use
nationwide.


Mike Borgelt