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 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.

On Apr 29, 5:51*am, Larry Dighera wrote:


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.


How slow does a target need to be to be undisplayed -typically? I
would have thought that even a glider is fast (45 knots) compared to
usual clutter.

Cheers

On Mon, 28 Apr 2008 12:49:07 -0700 (PDT), WingFlaps
wrote in
:

On Apr 29, 5:51*am, Larry Dighera wrote:


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.


How slow does a target need to be to be undisplayed -typically? I
would have thought that even a glider is fast (45 knots) compared to
usual clutter.


I have no idea, but just assumed it was a tunable parameter.

Perhaps one of the ATC folks among the readership of these newsgroups
may offer some input on that subject.

In rec.aviation.soaring WingFlaps wrote:
On Apr 29, 5:51?am, Larry Dighera wrote:

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.

How slow does a target need to be to be undisplayed -typically? I
would have thought that even a glider is fast (45 knots) compared to
usual clutter.

A cruising glider is likely to be faster than that. However, gliders
climbing in a thermal are making tight little circles, and I believe this
will look like a stationary target to the radar. Worse, a glider climbing
in wave really will *be* stationary, as the glider will try not to move by
matching airspeed to wind speed at altitude. I have heard stories of
unintelligent GPS units deciding the airplane was parked and shutting
themselves off in this situation.

--
Michael Ash
Rogue Amoeba Software

"WingFlaps" wrote in message
...

How slow does a target need to be to be undisplayed -typically? I
would have thought that even a glider is fast (45 knots) compared to
usual clutter.


There are two windmill farms about twenty miles northeast of Green Bay that
break through the Moving Target Indicator. The windmills are stationary, of
course, but the moving rotors are detected.

In article ,
WingFlaps wrote:

How slow does a target need to be to be undisplayed -typically? I
would have thought that even a glider is fast (45 knots) compared to
usual clutter.

Don't forget that it's the radial velocity that is detected by skin paint.

--
Bob Noel
(goodness, please trim replies!!!)

On May 4, 8:37*am, Bob Noel
wrote:
In article ,

*WingFlaps wrote:
How slow does a target need to be to be undisplayed -typically? I
would have thought that even a glider is fast (45 knots) compared to
usual clutter.

Don't forget that it's the radial velocity that is detected by skin paint.



Aha, someone who understands Dopplewho knows!. data from the secondary
sites can fix that problem.

Cheers

Larry Dighera wrote:

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.

In my local area, some glider are fiberglass with some carbon, like a
spar (like a PIK 20 E), or are entirely carbon. All are motorgliders. At
Ephrata, WA, where most of the state's gliders fly, the construction
varies from fiberglass through carbon. Only a few of the gliders are
motorgliders. I expect materials to make a difference, but it's hard to
tell from the anecdotal information. The biggest difference seems to be
making that radio call to ATC.

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.

My thought is pilots, ATC, and FAA might discover contacting ATC
achieves enough of what everyone wants, that a complete revocation of
our exemption might be avoided. To make the case, we need to try the ATC
system to determine this.


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.

True. I don't know where that is going, but maybe if a jet runs into a
Champ, they'll get their exemption removed, too. Or maybe they are next
to lose it, regardless.

--
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