Feds Want to Equipe Gliders With Transponders and Radios

On Sun, 27 Apr 2008 15:03:33 -0700 (PDT), WingFlaps
wrote in
:

On Apr 28, 9:32*am, Larry Dighera wrote:
On Sun, 27 Apr 2008 12:34:55 -0700 (PDT), WingFlaps
wrote in
:

A radar reflector like they use on weather balloon ought be
sufficient. It is just a piece of foil with a large cross section.

That's a constructive suggestion. *

How large must such a radar reflector be? *

It's a retroreflector, I have one in the form of a tube about 3 inches
in diameter and 2 feet long. The corner cubes are inside that. I have
no idea how effective it is compared to a classic reflector which
occupies *a cube about 1 foot across and retroreflects the radar
equally in all directions.
...

Interesting. *Thanks for the information. *

How do you think it might affect a sailplane's L/D?


Well, if the sailplane skin is transparent to radar a big reflector
could be mounted inside, they don't weigh much. On the other hand a
cylinder type reflector could be made quite aerodynamic and even
incorporated into (say) the wing tips?

Cheers

That sounds like a very simple, inexpensive and effective solution to
the issue. Best of all, the pilot can't turn it off. :-)

Larry Dighera wrote:

...
Interesting. Thanks for the information.

How do you think it might affect a sailplane's L/D?

Well, if the sailplane skin is transparent to radar a big reflector
could be mounted inside, they don't weigh much. On the other hand a
cylinder type reflector could be made quite aerodynamic and even
incorporated into (say) the wing tips?

Cheers

That sounds like a very simple, inexpensive and effective solution to
the issue. Best of all, the pilot can't turn it off. :-)

Locally, approach radar has no trouble finding our transponderless
gliders (when we call them), tracking them, and warning/diverting other
traffic. We generally do this within 15-20 miles of our towered
airports. It works well for us, given the altitudes we fly at.

I don't know that a corner reflector would improve on the situation, or
if they would detect the gliders without the radio call. While the pilot
can't turn it off, it may be the controller doesn't notice it without
the radio call, and may not be able to see it because of other clutter,
or perhaps the display filter settings.

It's worth contacting ATC in your area to see if they are willing and
able to do the same for you. It's not practical everywhere, but it's
cheap and easy if it is.

A problem the reflector can not solve is TCAS will still not detect the
glider. This might be deal-breaker for the FAA/NTSB people.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Apr 27, 3:45 pm, Larry Dighera wrote:
On Sun, 27 Apr 2008 15:03:33 -0700 (PDT), WingFlaps
wrote in
:



On Apr 28, 9:32 am, Larry Dighera wrote:
On Sun, 27 Apr 2008 12:34:55 -0700 (PDT), WingFlaps
wrote in
:

A radar reflector like they use on weather balloon ought be
sufficient. It is just a piece of foil with a large cross section.

That's a constructive suggestion.

How large must such a radar reflector be?

It's a retroreflector, I have one in the form of a tube about 3 inches
in diameter and 2 feet long. The corner cubes are inside that. I have
no idea how effective it is compared to a classic reflector which
occupies a cube about 1 foot across and retroreflects the radar
equally in all directions.
...

Interesting. Thanks for the information.

How do you think it might affect a sailplane's L/D?

Well, if the sailplane skin is transparent to radar a big reflector
could be mounted inside, they don't weigh much. On the other hand a
cylinder type reflector could be made quite aerodynamic and even
incorporated into (say) the wing tips?

Cheers

That sounds like a very simple, inexpensive and effective solution to
the issue. Best of all, the pilot can't turn it off. :-)

Unfortunately too simple. The problem is NOT ATC's equipment having
trouble painting a glider. The problem is the threshold of sensitivity
on their radars is set far too high to display us since they
intentionally filter out things as slow as a glider, particularly if
it's thermalling. We are simply filtered out as clutter (according to
the rep Reno sent to address PASCO last winter). That said, I'm sure
we don't all read the same on radar, but gliders are not the stealth
aircraft they are being made out to be. I believe cockpit alone has a
rather large signature, unless of course you paid the extra $1,000,000
for the one molecule thick layer of electrically deposited gold on
your canopy. There's more to a stealth aircraft then it being made of
fiberglass, or even carbon...

Paul

On Apr 28, 6:24*pm, sisu1a wrote:
On Apr 27, 3:45 pm, Larry Dighera wrote:





On Sun, 27 Apr 2008 15:03:33 -0700 (PDT), WingFlaps
wrote in
:

On Apr 28, 9:32 am, Larry Dighera wrote:
On Sun, 27 Apr 2008 12:34:55 -0700 (PDT), WingFlaps
wrote in
:

A radar reflector like they use on weather balloon ought be
sufficient. It is just a piece of foil with a large cross section..

That's a constructive suggestion.

How large must such a radar reflector be?

It's a retroreflector, I have one in the form of a tube about 3 inches
in diameter and 2 feet long. The corner cubes are inside that. I have
no idea how effective it is compared to a classic reflector which
occupies *a cube about 1 foot across and retroreflects the radar
equally in all directions.
...

Interesting. *Thanks for the information.

How do you think it might affect a sailplane's L/D?

Well, if the sailplane skin is transparent to radar a big reflector
could be mounted inside, they don't weigh much. On the other hand a
cylinder type reflector could be made quite aerodynamic and even
incorporated into (say) the wing tips?

Cheers

That sounds like a very simple, inexpensive and effective solution to
the issue. *Best of all, the pilot can't turn it off. *:-)

Unfortunately too simple. The problem is NOT ATC's equipment having
trouble painting a glider. The problem is the threshold of sensitivity
on their radars is set far too high to display us since they
intentionally filter out things as slow as a glider, particularly if
it's thermalling. We are simply filtered out as clutter (according to
the rep Reno sent to address PASCO last winter). That said, I'm sure
we don't all read the same on radar, but gliders are not the stealth
aircraft they are being made out to be. I believe cockpit alone has a
rather large signature, unless of course you paid the extra $1,000,000
for the one molecule thick layer of electrically deposited gold on
your canopy. There's more to a stealth aircraft then it being made of
fiberglass, or even carbon...


Only perfectly flat surfaces are more stealthy because they bounce the
radar away from the source, whereas a convex surface always bounces
some energy back (falling rapidly with distance). A concave surface
starts to act as a retroreflector. I am sure that the nicely curved
body of a high performance glass glider has a much lower radar cross
section than any aluminium GA aircraft. It's not stealth but
fiberglass is so transparent it's used for radomes.

Cheers

sisu1a wrote in
:

On Apr 27, 3:45 pm, Larry Dighera wrote:
On Sun, 27 Apr 2008 15:03:33 -0700 (PDT), WingFlaps
wrote in
:



On Apr 28, 9:32 am, Larry Dighera wrote:
On Sun, 27 Apr 2008 12:34:55 -0700 (PDT), WingFlaps
wrote in
68afa9fb-b4d2-4620-91e6-f0a85a75d...
@x19g2000prg.googlegroups.com
:

A radar reflector like they use on weather balloon ought be
sufficient. It is just a piece of foil with a large cross
section.

That's a constructive suggestion.

How large must such a radar reflector be?

It's a retroreflector, I have one in the form of a tube about 3
inches in diameter and 2 feet long. The corner cubes are inside
that. I have no idea how effective it is compared to a classic
reflector which occupies a cube about 1 foot across and
retroreflects the radar equally in all directions.
...

Interesting. Thanks for the information.

How do you think it might affect a sailplane's L/D?

Well, if the sailplane skin is transparent to radar a big reflector
could be mounted inside, they don't weigh much. On the other hand a
cylinder type reflector could be made quite aerodynamic and even
incorporated into (say) the wing tips?

Cheers

That sounds like a very simple, inexpensive and effective solution to
the issue. Best of all, the pilot can't turn it off. :-)

Unfortunately too simple. The problem is NOT ATC's equipment having
trouble painting a glider. The problem is the threshold of sensitivity
on their radars is set far too high to display us since they
intentionally filter out things as slow as a glider, particularly if
it's thermalling. We are simply filtered out as clutter (according to
the rep Reno sent to address PASCO last winter). That said, I'm sure
we don't all read the same on radar, but gliders are not the stealth
aircraft they are being made out to be. I believe cockpit alone has a
rather large signature, unless of course you paid the extra $1,000,000
for the one molecule thick layer of electrically deposited gold on
your canopy. There's more to a stealth aircraft then it being made of
fiberglass, or even carbon.



You fly Sisu?


Bertie

On Mon, 28 Apr 2008 04:20:30 GMT, Eric Greenwell
wrote in igcRj.6716$r12.4153@trndny03:

Larry Dighera wrote:

...
Interesting. Thanks for the information.

How do you think it might affect a sailplane's L/D?

Well, if the sailplane skin is transparent to radar a big reflector
could be mounted inside, they don't weigh much. On the other hand a
cylinder type reflector could be made quite aerodynamic and even
incorporated into (say) the wing tips?

Cheers

That sounds like a very simple, inexpensive and effective solution to
the issue. Best of all, the pilot can't turn it off. :-)

Locally, approach radar has no trouble finding our transponderless
gliders (when we call them), tracking them, and warning/diverting other
traffic. We generally do this within 15-20 miles of our towered
airports. It works well for us, given the altitudes we fly at.


Thank you for this information.

Would the gliders you mention be of glass-fiber, aluminum, or
carbon-fiber composite construction? I would expect a glass ship with
few metal parts to be rather transparent to radar.

I don't know that a corner reflector would improve on the situation, or
if they would detect the gliders without the radio call. While the pilot
can't turn it off, it may be the controller doesn't notice it without
the radio call, and may not be able to see it because of other clutter,
or perhaps the display filter settings.

I would guess the controller would need to adjust his scope from it's
usual setting to see primary targets, so a radio call may be
necessary. While a corner reflector would doubtless increase the
radar energy returned to the radar antenna and provide a brighter
primary target, I doubt that would be sufficient to cause the glider
so equipped to become visible on ATC's scopes without reconfiguring
them to display slow-moving primary targets.


It's worth contacting ATC in your area to see if they are willing and
able to do the same for you. It's not practical everywhere, but it's
cheap and easy if it is.


I'm not so much concerned about my personal situation as I am about
the FAA rescinding the glider exemption from FARs that require
transponder use. If we can give the FAA some guidance on this issue,
the outcome will likely be more acceptable, than if the draft their
NPRM without pilot input, IMO.

A problem the reflector can not solve is TCAS will still not detect the
glider. This might be deal-breaker for the FAA/NTSB people.

I agree. But rescinding the glider exemption from FARs requiring
transponder use won't address that issue with powered aircraft that
lack an electrical system either. It looks like the FAA's response to
this NTSB recommendation is destined to be a compromise at best.
Hopefully it won't result in all gliders and aircraft without
electrical systems being grounded until they have transponders
installed and signed off.

Larry Dighera wrote:


Perhaps it would be possible to modify ATC procedures or display
software to overcome that issue. That would certainly be preferable
to requiring electrical systems be installed in all gliders.

Not to ATC.

On Sun, 27 Apr 2008 23:24:48 -0700 (PDT), sisu1a
wrote in
:

[radar corner reflector suggestion snipped]


That sounds like a very simple, inexpensive and effective solution to
the issue. Best of all, the pilot can't turn it off. :-)

Unfortunately too simple. The problem is NOT ATC's equipment having
trouble painting a glider. The problem is the threshold of sensitivity
on their radars is set far too high to display us since they
intentionally filter out things as slow as a glider, particularly if
it's thermalling. We are simply filtered out as clutter (according to
the rep Reno sent to address PASCO last winter).

Perhaps it would be possible to modify ATC procedures or display
software to overcome that issue. That would certainly be preferable
to requiring electrical systems be installed in all gliders.

That said, I'm sure we don't all read the same on radar, but gliders
are not the stealth aircraft they are being made out to be. I believe
cockpit alone has a rather large signature,

What is there in the glider cockpit of a typical glass ship that
reflects radar energy? I suppose the instruments are metal, and some
of the control linkage and gear are metallic, but I would expect the
corner reflector to provide a much stronger return.

unless of course you paid the extra $1,000,000 for the one molecule
thick layer of electrically deposited gold on your canopy. There's
more to a stealth aircraft then it being made of fiberglass, or even
carbon...

Paul

I would think carbon-fiber composite would be nearly as reflective to
radar energy as aluminum.

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.

On Apr 28, 3:18*am, WingFlaps wrote:
*I am sure that the nicely curved
body of a high performance glass glider has a much lower radar cross
section than any aluminium GA aircraft. It's not stealth but
fiberglass is so transparent it's used for radomes.


The RCS of glass gliders is quite large because of all the metal push
rods. Tests with local radar (Luke Air Force base) showed no
significant improvement in primary target return if a corner reflector
was added.

I have been easily tracked by approach control in my ASW19 and had
them vector traffic round me as I climbed. They do have to want to
see you though and, as others have pointed out, it's likely that the
radar display will be set to filter out a slow moving primary target.


Andy

Larry Dighera wrote:
radar energy as aluminum.

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 may have made a small mistake: 175 to 250 Watts
is the pulse output power. In the same document, the
current consumption is about a half ampere at 14 V,
which is 7 Watts.

--

Tauno Voipio (CPL(A), avionics engineer)
tauno voipio (at) iki fi