Feds Want to Equipe Gliders With Transponders and Radios

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 19:20:20 GMT, Tauno Voipio
wrote in
:

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.

You are correct. Here's another with even less power consumption:
http://www.sportflyingshop.com/Avion...ansponder.html
Microair T2000 Transponder, $1,825
Wiring harness for T2000, $149
Ameri-King AK-350 Blind Encoder, $179

Power input: .25 amps @ 27.50 volts;
.4 amps @ 13.75 volts TX,
80 mA RX

I wonder if those power consumption figures include the heater in the
encoder.


Perhaps it's a good idea to require equipping all gliders with
transponders after all. :-(

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

In rec.aviation.soaring Larry Dighera wrote:
I wonder if those power consumption figures include the heater in the
encoder.


Perhaps it's a good idea to require equipping all gliders with
transponders after all. :-(

Keep in mind that the recommendation is not to require equipping all
gliders with transponders. It's to remove the exemption given to gliders
and give them the same rules as powered aircraft with electrical systems,
to require them to have a transponder for flight into a mode C veil or
above 10,000ft. In some places this would do almost nothing; where I fly
we are outside the veil (barely) and hit 10,000ft maybe a couple of times
a year. In other places it would severely limit activity for gliders
without transponders to the extent that it would essentially be required.

The power requirements are a secondary concern, the primary concern is
cost. Power requirements of course influence cost. There are gliders with
transponders out there, so obviously it can be done. But there are a lot
of gliders for which the cost of a transponder installation would be a
sizable fraction of the total value of the aircraft, and this change could
put their owners in a very bad spot.

--
Michael Ash
Rogue Amoeba Software

WingFlaps wrote:

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.

But, gliders have been made with carbon fiber for decades now, and even
fiberglass gliders have metal parts. Do pilots in your area find ATC
(typically "approach" ATC) unable to detect ANY of your gliders?

--
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

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

Larry Dighera wrote:


You are correct. Here's another with even less power consumption:
http://www.sportflyingshop.com/Avion...ansponder.html
Microair T2000 Transponder, $1,825
Wiring harness for T2000, $149
Ameri-King AK-350 Blind Encoder, $179

Power input: .25 amps @ 27.50 volts;
.4 amps @ 13.75 volts TX,
80 mA RX

I wonder if those power consumption figures include the heater in the
encoder.

No, that figure doesn't include the encoder. The heater can be 200-300
ma when it's fully on, but the typical unit won't be fully on unless
it's "really" cold outside. In my glider, that seems to be lower than
~10 deg F - winter wave flying for me. There are encoders with less low
temperature draw, but they tend to be expensive.

--
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

In article dSuRj.7182$r12.6971@trndny03,
Eric Greenwell wrote:

But, gliders have been made with carbon fiber for decades now, and even
fiberglass gliders have metal parts.

Is carbon more reflective than glass?

On Mon, 28 Apr 2008 22:34:56 -0400, Roy Smith wrote in
:


Is carbon more reflective than glass?

Carbon, being conductive, would be expected to be considerably
reflective of radar energy, IMO.