Feds Want to Equipe Gliders With Transponders and Radios

On Apr 28, 7:44*pm, Larry Dighera wrote:
snip
The issue in equipping gliders with transponders, the way I see it, is
the high power consumption required by transponders. *Here's a typical
glider transponder:http://www.airplanegear.com/becker.htm
It seems to draw 175W to 250W. *That's not insignificant, and way more
than the comm radio consumes. *Then there's the weight and antenna
that reduce performance, not to mention the cost of the equipment,
installation, and maintenance.

You need to find the overall consumption, not what is used when it is
squawking.

As to weight - since we frequently put water in gliders to improve
performance, I can't see a problem there, and the antenna will be
inside the glider so won't increase drag.

But you are right that buying and installing a transponder isn't a
cheap thing.

"Cats" wrote in message
...
On Apr 28, 7:44 pm, Larry Dighera wrote:
snip
The issue in equipping gliders with transponders, the way I see it, is
the high power consumption required by transponders. Here's a typical
glider transponder:http://www.airplanegear.com/becker.htm
It seems to draw 175W to 250W. That's not insignificant, and way more
than the comm radio consumes. Then there's the weight and antenna
that reduce performance, not to mention the cost of the equipment,
installation, and maintenance.

You need to find the overall consumption, not what is used when it is
squawking.

As to weight - since we frequently put water in gliders to improve
performance, I can't see a problem there, and the antenna will be
inside the glider so won't increase drag.

But you are right that buying and installing a transponder isn't a
cheap thing.

-------------new message begins-------------

I 'm confident that the installation is the biggest part of it--especially
when you include enough solar panels to power it all reliably.

Peter

On Tue, 29 Apr 2008 01:44:00 GMT, Eric Greenwell
wrote in A3vRj.3311$WS1.1091@trndny04:

The biggest difference seems to be making that radio call to ATC.

I presume the radio call to ATC is a position report, so that the
controller knows where to look for your primary target.

That seems like a natural programming application for computer
detection of glider targets, which may do away with the necessity of a
radio call to ATC (especially in the event of NORDO aircraft). If
such a glider primary-target detection algorithm could be made to work
reliably, it wouldn't cost too much to implement it, way less than the
cost of equipping gliders with transponders, IMO.

Someone posted a report of a study on radar reflection with and
without a corner reflector that indicated there was little difference.
That doesn't seem intuitive, but I suppose it depends on the distances
involved and the metallic content.

On Apr 30, 4:29*am, Larry Dighera wrote:


Someone posted a report of a study on radar reflection with and
without a corner reflector that indicated there was little difference.
That doesn't seem intuitive, but I suppose it depends on the distances
involved and the metallic content. *

A good 1' boating radar reflector has a radar cross section of about
7m^2. If you compare this to the _visual_ cross section of a glider
then in some directions it is larger and in others smaller. But this
simple comparison ignores the transparency of fiber glass. I imagine
that a major reflector in the glider is the pilot (say 1m^2) and
electronics and about half a bucket of some bolts and hinges? I'd
estimate that this all would add up to no more 3m^2 of cross section
so adding just 1 radar reflector could triple the cross section -but
I'd like to see so real measurements.

Cheers

On Apr 29, 2:53*pm, WingFlaps wrote:
On Apr 30, 4:29*am, Larry Dighera wrote:



Someone posted a report of a study on radar reflection with and
without a corner reflector that indicated there was little difference.
That doesn't seem intuitive, but I suppose it depends on the distances
involved and the metallic content. *

A good 1' boating radar reflector has a radar cross section of about
7m^2. If you compare this to the _visual_ cross section of a glider
then in some directions it is larger and in others smaller. But this
simple comparison ignores the transparency of fiber glass. I imagine
that a major reflector in the glider is the pilot (say 1m^2) and
electronics and about half a bucket of some bolts and hinges? I'd
estimate that this all would add up to no more 3m^2 of cross section
so adding just 1 radar reflector could triple the cross section -but
I'd like to see so real measurements.

Cheers

Once again - This has already been tested. ATC radars do not have
any trouble detecting gliders of any kind as primary targets IF THEY
ARE NOT FILTERED OUT. When reflectors were added, no difference was
noticed by ATC. And from personal experience in G-102s, LS-4s, and
LS-6s, I have never had any problem being picked up by a terminal
radar when I told them where I was.

Transponders are great, and if you can afford one and fly where it is
useful, get one. Larry Dighera obviously hasn't been around a modern
glass glider recently or he would understand that most have electrical
systems and many have transponders. Many are now getting MRX TPAS to
detect transponders - actually a better solution in most of the places
gliders fly (particularly back East).

The NTSB recommendation is just that - a recommendation.

Sheesh, do some research!

Kirk
LS6b 66
TPAS, GPS, radio, moving map, ELT equipped; powered by 2 independent
battery systems.

On Apr 29, 12:53 pm, WingFlaps wrote:
On Apr 30, 4:29 am, Larry Dighera wrote:



Someone posted a report of a study on radar reflection with and
without a corner reflector that indicated there was little difference.
That doesn't seem intuitive, but I suppose it depends on the distances
involved and the metallic content.

A good 1' boating radar reflector has a radar cross section of about
7m^2. If you compare this to the _visual_ cross section of a glider
then in some directions it is larger and in others smaller. But this
simple comparison ignores the transparency of fiber glass. I imagine
that a major reflector in the glider is the pilot (say 1m^2) and
electronics and about half a bucket of some bolts and hinges? I'd
estimate that this all would add up to no more 3m^2 of cross section
so adding just 1 radar reflector could triple the cross section -but
I'd like to see so real measurements.

Cheers

Although the actual x-section of the given reflecting materials may
only add up to that amount as a static total, how it is arranged makes
a huge difference just the as much as how although a composite glider
is only a couple of bolts of glass cloth/and or some carbon/kevlar and
a couple of buckets of resin and some hardware...but depending on how
it's arranged makes the difference of whether it's an ASG-29 or if its
an PW-2 Gappa (OK, not specifically, but I think the point is
made...).

Likewise, how these reflective materials are individually shaped as
well as how they are arranged makes all the difference as to what the
radar sees. Some would vary greatly from type to type, as some have
vastly different materials/structures. Your cockpit rails and other
angular objects in the cockpit (as well as the humy too I suppose)
form lots of the signature, but having nuts/bolts/pushrods extending
out 20'-50' off either side matters too. The F-117 illustrates this
point nicely. BTW, even "stealth" aircraft are still technically
visible to radar, it is just that their signature is usually reduced
to the size of a pigeon or less making them much easier to mask.

It is my understanding though, (as already mentioned) it is NOT out
lack of a readable signature as a primary target (I'm not saying we
have huge signatures, just that they are already readable for the most
part, some better than others...), but our slow/erratic flying gets us
weeded out of the picture the same way it filters out buildings and
mountains. Again, this is from MY recollection from the Reno ATC rep
while addressing this very subject last winter. Any PASCO folks that
also attended care to elaborate?, did you film it Kemp? Whether ATC
can theoretically come up with a better target tracking/filtration
system should really be the question, but I think we ALL know that
would be an answer we should not hold our breath for!

Paul

On Tue, 29 Apr 2008 13:15:46 -0700 (PDT), "kirk.stant"
wrote in
:

Larry Dighera obviously hasn't been around a modern
glass glider recently or he would understand that most have electrical
systems and many have transponders.

As a percentage of the entire sailplane fleet, how many would you
estimate are "modern glass gliders?"

You can't put the antenna on the inside of a carbon fiber fuselage, well,
you could, but it would not work.
Not all gliders have excess usable weight available to carry water.

BT
_____________

You need to find the overall consumption, not what is used when it is
squawking.

As to weight - since we frequently put water in gliders to improve
performance, I can't see a problem there, and the antenna will be
inside the glider so won't increase drag.

But you are right that buying and installing a transponder isn't a
cheap thing.

On Apr 30, 8:40*am, sisu1a wrote:


It is my understanding though, (as already mentioned) it is NOT out
lack of a readable signature as a primary target (I'm not saying we
have huge signatures, just that they are already readable for the most
part, some better than others...), but our slow/erratic flying gets us
weeded out of the picture the same way it filters out buildings and
mountains. Again, this is from MY recollection from the Reno ATC rep
while addressing this very subject last winter.

As far as I know, fixed returns from stationary targets are removed by
simple sweep differencing and thresholding. It may be that target
doppler shift is used to selectr/reject moving targets so the issue
would then be the threshold for that rejection. I read that an
interceptor radar had a threshold of about 20 knots for this purpose
but I can't find any statement (via google) as to what threshold ATC
usually uses. Measurement of small doppler shift is aided by a strong
signal, so weak slow targets would be doubly rejected so to speak. I
doubt they see flocks of birds, but then they mostly fly at less than
30 knots I think (even the african swallow :-) so the could be set to
30knots without degrading system performance (maybe?).

I suspect that if the "powers that be" want to see gliders for traffic
avoidance and gliders don't want transponders it would be in their
best interest to make sure they can be easily seen by passive means.
Beaurocrats like being given options that are win win for both pasties
If offering to mount a really cheap reflector inside the fuse could
assure detectability, it could be a way to go forward (assuming
gliders want $ savings from avoiding the purchase and regular testing
of transponders)...

Just trying to help, I'm not a regular glider pilot.
Cheers

"Peter Dohm" wrote

I 'm confident that the installation is the biggest part of it--especially
when you include enough solar panels to power it all reliably.

Why solar cells? A 7 amp hour lead acid gel cell can be had for about 20 bucks,
and would run a solid state transponder for a whole flight.
--
Jim in NC