Re: Feds Want to Equipe Gliders With Transponders and Radios

[Larry Dighera]

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. :-)

[Eric Greenwell]

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

[sisu1a]

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

[WingFlaps]

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

[Bertie the Bunyip[_25_]]

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

[Larry Dighera]

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.

[B A R R Y[_2_]]

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.

[Larry Dighera]

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.

[Andy[_1_]]

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

[Tauno Voipio]

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

[WingFlaps]

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

[Larry Dighera]

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/Avionics/MicroairTransponder/microairtransponder.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. :-(

[Larry Dighera]

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.

[Michael Ash]

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

[Michael Ash]

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

[Eric Greenwell]

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

[Eric Greenwell]

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

[Eric Greenwell]

Larry Dighera wrote:

>
> You are correct. Here's another with even less power consumption:
> http://www.sportflyingshop.com/Avionics/MicroairTransponder/microairtransponder.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

[Roy Smith]

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?

[Larry Dighera]

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.

[Cats]

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.

[Peter Dohm]

"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

[Larry Dighera]

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.

[WingFlaps]

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

[kirk.stant]

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.

[sisu1a]

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

[Larry Dighera]

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?"

[BT]

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.

[WingFlaps]

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

[Morgans[_2_]]

"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

[Alan[_6_]]

In article "Morgans" > writes:
>"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.

One doesn't want to run the lead acid battery down past about 1/2 its capacity
to get a reasonable service life from it, so that limits you to 3.5 AH.

Given that they are also probably running some of:

o A com radio.
o An elecronic variometer.
o A gps.
o A flight logger.

and that they are wanting these to run for flights of 5 - 8 hours or more,
it is fairly clear that the 7 AH battery cannot do it.

I would expect they have already trimmed the list of electronic items
in order to get their flight time from the battery, so a transponder would
need another battery, or giving up some of the other equipment.


More thoughts on the basic issue of protecting IFR aircraft from gliders.
How about designating that area as having fairly low speed limits all the
way up to 18,000 feet (where wave windows would take over for separation),
only in this case note that if the aircraft is unable to fly that slowly,
they have to go around the airspace.


Alan

[[email protected][_2_]]

On Apr 29, 5:35*pm, Larry Dighera > wrote:
> 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?" *

Been to a glider field lately? Or a contest, or fun meet?

At my club, we have 5 older generation, non-glass gliders. The rest
of our fleet, club and private, totals perhaps 12 glass ships - all
with electrical systems (and one with a transponder). So that is a
pretty high percentage.

I would estimate that by flight hour, the majority of glider flying in
the US (and the rest of the world) is done in "modern glass gliders".

So if your idea of a typical American glider is a beat-up 2-33, you
might be surprised. While you will still find a lot of them around,
it's amazing how little they fly (with some obvious exceptions, of
course!).

Kirk

[Michael Ash]

In rec.aviation.soaring Alan > wrote:
> In article "Morgans" > writes:
>>"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.
>
> One doesn't want to run the lead acid battery down past about 1/2 its capacity
> to get a reasonable service life from it, so that limits you to 3.5 AH.

What kind of unreasonable service life do you get if you use the full
capacity, and at $20 each do you care if you use it up faster? Unless you
can count the number of cycles on your fingers that may be the simplest
and most cost effective way to go, although of course I may be overlooking
something important.

--
Michael Ash
Rogue Amoeba Software

[Shawn[_5_]]

wrote:
> On Apr 29, 5:35 pm, Larry Dighera > wrote:
>> 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?"
>
> Been to a glider field lately? Or a contest, or fun meet?
>
> At my club, we have 5 older generation, non-glass gliders. The rest
> of our fleet, club and private, totals perhaps 12 glass ships - all
> with electrical systems (and one with a transponder). So that is a
> pretty high percentage.
>
> I would estimate that by flight hour, the majority of glider flying in
> the US (and the rest of the world) is done in "modern glass gliders".
>
> So if your idea of a typical American glider is a beat-up 2-33, you
> might be surprised. While you will still find a lot of them around,
> it's amazing how little they fly (with some obvious exceptions, of
> course!).

Similar in Boulder. 60% of our club fleet is glass (OK it's only three
out of five, but still...) Mile High Gliding is about 50:50, then there
are the 30 or so private ship. I believe there are one or two HPs, the
rest are composite.

Shawn

[Morgans[_2_]]

"Michael Ash" > wrote

> What kind of unreasonable service life do you get if you use the full
> capacity, and at $20 each do you care if you use it up faster? Unless you
> can count the number of cycles on your fingers that may be the simplest
> and most cost effective way to go, although of course I may be overlooking
> something important.

I have found that using 60% or perhaps 70% does not seem to limit their life
noticeably. What does kill them is to charge them too fast, or most
importantly, leaving them sitting around in a discharged state. Doing that one
time could be the end of them.

The better question than asking how much more quickly a higher discharge kills
them for the price, is to ask why not buy an extra one, or two.

Larger gell cells are also available, but I'm not sure where the economics of
buying more small ones versus buying a single larger one come into play.
--
Jim in NC

[Alan[_6_]]

In article > Michael Ash > writes:
>In rec.aviation.soaring Alan > wrote:

>> One doesn't want to run the lead acid battery down past about 1/2 its capacity
>> to get a reasonable service life from it, so that limits you to 3.5 AH.
>
>What kind of unreasonable service life do you get if you use the full
>capacity, and at $20 each do you care if you use it up faster? Unless you
>can count the number of cycles on your fingers that may be the simplest
>and most cost effective way to go, although of course I may be overlooking
>something important.

It depends on the details of the battery. Lead acid batteries come in a
lot of sub-types, with varying ability to handle deeper discharges. The
better ones cost more.

Other factors include the output voltage under load at discharge -- a
lead acid battery is rated to 10.2 to 10.5 volts for a "12 volt" battery
at discharge. Unfortunately, most 12 volt radios and devices are designed
for a charging electrical system, with a voltage of about 14 volts. When
the battery is down to 75% of the expected voltage for the radio, not all
of them work. I have had aircraft radios that would not transmit below
about 11.5 volts, at which point the battery would be still above 50% charged.

Lead acid batteries are normally rated for capacity at a 20 hour rate of
discharge. A 7 AH battery would deliver 7000 / 20 = 350 mA for 20 hours.
Faster discharge rates result in less capacity being available (look up
Peukerts exponent for more details). Discharging faster than that, reduces
the amp-hour capacity of the battery.

Lead acid batteries have less capacity when cold. One guide suggests that
for every 10 degrees centigrade below room temperature, you should add 10%
to the battery capacity needed. High altitude flight tends to get up into
cold places.


Alan

[Tony Verhulst]

> At my club, we have 5 older generation, non-glass gliders. The rest
> of our fleet, club and private, totals perhaps 12 glass ships - all
> with electrical systems (and one with a transponder).


IMHO, in FAA speak, an aircraft having only battery power does not have
an electrical system.

FAR 91.215:

(3) Notwithstanding paragraph (b)(2) of this section, any aircraft which
was not originally certificated with an *engine-driven* electrical
system or which has not subsequently been certified with such a system
installed, balloon or glider may conduct operations in the airspace
within 30 nautical miles of an airport listed in appendix D, section 1
of this part provided such operations are conducted—.......

Tony V.

[Eric Greenwell]

Michael Ash wrote:
> In rec.aviation.soaring Alan > wrote:
>> In article "Morgans" > writes:
>>> "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.
>> One doesn't want to run the lead acid battery down past about 1/2 its capacity
>> to get a reasonable service life from it, so that limits you to 3.5 AH.
>
> What kind of unreasonable service life do you get if you use the full
> capacity, and at $20 each do you care if you use it up faster? Unless you
> can count the number of cycles on your fingers that may be the simplest
> and most cost effective way to go, although of course I may be overlooking
> something important.

According to the Powersonic Technical Manual, you can get about 200
cycles using 100% discharges, and about 500 cycles using 50% discharges,
before the battery is down to 60% of it's capacity. If you need 80% of
the battery capacity, the cycle numbers are about 150 and 400,
respectively. 150 cycles is 3 years or more for most pilots - not bad
for $20.

--
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

[Steven P. McNicoll[_2_]]

"Larry Dighera" > wrote in message
...
>
> 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.
>

So just remove the exemption at and above 10,000 MSL.

[Steven P. McNicoll[_2_]]

"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.

[Steven P. McNicoll[_2_]]

"kirk.stant" > wrote in message
...
>
> 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.
>

Not all ATC radars are the same. ASR displays primary targets rather well,
ARSR not very well at all. Some enroute radar sites are just beacon
interrogators, no primary radar at all.

[Michael Ash]

In rec.aviation.soaring Steven P. McNicoll > wrote:
>
> "Larry Dighera" > wrote in message
> ...
>>
>> 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.
>
> So just remove the exemption at and above 10,000 MSL.

This is precisely what is being proposed. I don't understand why anything
else is even being discussed.

Note that requiring all gliders flying above 10,000MSL to be
transponder-equipped would still result in a large amount of either
expense or restrictions on flying for a large proportion of the
glider-flying population.

--
Michael Ash
Rogue Amoeba Software

[5Z]

On May 1, 9:41 am, Michael Ash > wrote:
> > So just remove the exemption at and above 10,000 MSL.
>
> This is precisely what is being proposed. I don't understand why anything
> else is even being discussed.

A 3,000' tow at my club will go just a hair over 10K.

-Tom

[Bill Daniels]

"5Z" > wrote in message
...
> On May 1, 9:41 am, Michael Ash > wrote:
>> > So just remove the exemption at and above 10,000 MSL.
>>
>> This is precisely what is being proposed. I don't understand why anything
>> else is even being discussed.
>
> A 3,000' tow at my club will go just a hair over 10K.
>
> -Tom

Yep, we do little soaring below 10,000' - big rocks tend to get in the way.

Bill D

[Sarah Anderson[_2_]]

Don't they also intend to require a mode C transponder inside class B "veils"?

A reading of
> Remove the glider exemptions from the Federal Aviation Regulations
> that pertain to transponder requirements and use.

would seem to imply that. There are a lot of people ( like me ) operating underneath class Bs


Sarah


Michael Ash wrote:
> In rec.aviation.soaring Steven P. McNicoll > wrote:
>> "Larry Dighera" > wrote in message
>> ...
>>> 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.
>> So just remove the exemption at and above 10,000 MSL.
>
> This is precisely what is being proposed. I don't understand why anything
> else is even being discussed.

> Note that requiring all gliders flying above 10,000MSL to be
> transponder-equipped would still result in a large amount of either
> expense or restrictions on flying for a large proportion of the
> glider-flying population.
>

[Michael Ash]

In rec.aviation.soaring Sarah Anderson > wrote:
>
> Don't they also intend to require a mode C transponder inside class B "veils"?
>
> A reading of
> > Remove the glider exemptions from the Federal Aviation Regulations
> > that pertain to transponder requirements and use.
>
> would seem to imply that. There are a lot of people ( like me ) operating underneath class Bs

Yes, the idea would be to make the requirements the same as for powered
aircraft. This would no doubt have a large impact on a lot of people,
particularly our Western bretheren who think nothing of cracking 10,000ft,
and people such as yourself who operate close to class B. But it's not the
same as a blanket requirement as has been implied.

--
Michael Ash
Rogue Amoeba Software

[Alan[_6_]]

In article > writes:
>
>Don't they also intend to require a mode C transponder inside class B "veils"?
>
>A reading of
> > Remove the glider exemptions from the Federal Aviation Regulations
> > that pertain to transponder requirements and use.
>
>would seem to imply that. There are a lot of people ( like me ) operating underneath class Bs

In a sailplane? Wow. Doesn't give much vertical space. How much room do you have from base
of class B to the surface? You must have to find lift pretty often...

Alan

[Sarah Anderson[_2_]]

The issue is the veil. The shelves are high enough (6000/7000 msl) to get in and out staying
clear of class B.


Alan wrote:
> In article > writes:
>> Don't they also intend to require a mode C transponder inside class B "veils"?
>>
>> A reading of
>>> Remove the glider exemptions from the Federal Aviation Regulations
>>> that pertain to transponder requirements and use.
>> would seem to imply that. There are a lot of people ( like me ) operating underneath class Bs
>
> In a sailplane? Wow. Doesn't give much vertical space. How much room do you have from base
> of class B to the surface? You must have to find lift pretty often...
>
> Alan

[Eric Greenwell]

Alan wrote:

> Other factors include the output voltage under load at discharge -- a
> lead acid battery is rated to 10.2 to 10.5 volts for a "12 volt" battery
> at discharge.

Powersonic uses 10.5 volts for 5 to 20 hour discharge rates.

> Unfortunately, most 12 volt radios and devices are designed
> for a charging electrical system, with a voltage of about 14 volts.

Most panel mounted radios (definitely for Dittel and Becker radios)
bought new in the last 20 years (and even some older ones) meet the
current requirements to function properly to 10.5 volts, and at even
lower voltages, but with reduced power output. "Very old" radios likely
will have problems at 10.5 volts. I have no idea what the percentage of
"old" and "new" are.

> When
> the battery is down to 75% of the expected voltage for the radio, not all
> of them work. I have had aircraft radios that would not transmit below
> about 11.5 volts, at which point the battery would be still above 50% charged.

Powersonic shows it's batteries have only 25% capacity left at 11.5
volts. I haven't checked other brands, but believe they are the same for
the batteries we use in our gliders.
>
> Lead acid batteries are normally rated for capacity at a 20 hour rate of
> discharge. A 7 AH battery would deliver 7000 / 20 = 350 mA for 20 hours.
> Faster discharge rates result in less capacity being available (look up
> Peukerts exponent for more details). Discharging faster than that, reduces
> the amp-hour capacity of the battery.

At a current drain of 700 ma (10 hour rate) that you might have with
transponder, radio, etc, Powersonic shows a capacity of 90% of the 20
hour rate. That's not a show-stopper, but worth taking into account.

> Lead acid batteries have less capacity when cold. One guide suggests that
> for every 10 degrees centigrade below room temperature, you should add 10%
> to the battery capacity needed. High altitude flight tends to get up into
> cold places.

This corresponds with the Powersonic chart, so at -10C (15F), you have a
30% loss of capacity. For winter flying, and spring or fall flying in
places where you can climb to, say, 10,000' agl, it's an important
factor. Especially so, when you know your encoder will likely be using
it's heater, adding 50-150 milliamps to your current drain.

--
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

[Morgans[_2_]]

"Eric Greenwell" > wrote >
> This corresponds with the Powersonic chart, so at -10C (15F), you have a 30%
> loss of capacity. For winter flying, and spring or fall flying in places where
> you can climb to, say, 10,000' agl, it's an important factor. Especially so,
> when you know your encoder will likely be using it's heater, adding 50-150
> milliamps to your current drain.

Put a insulated cover around the battery, and the heat of discharge will keep
it warm and the capacity up, unless it is seriously freakin' cold.
--
Jim in NC

[Eric Greenwell]

Morgans wrote:
>
> "Eric Greenwell" > wrote >
>> This corresponds with the Powersonic chart, so at -10C (15F), you have
>> a 30% loss of capacity. For winter flying, and spring or fall flying
>> in places where you can climb to, say, 10,000' agl, it's an important
>> factor. Especially so, when you know your encoder will likely be using
>> it's heater, adding 50-150 milliamps to your current drain.
>
> Put a insulated cover around the battery, and the heat of discharge will
> keep it warm and the capacity up, unless it is seriously freakin' cold.

Insulating it will keep if from cooling off as quickly, but I'm
skeptical about the amount of self-heating. Do you know how much it is,
or where I can find a reference to it that applies to the batteries we
us? Insulating my battery is difficult due to it's location, so I'd like
to know it's worth the effort before attempting it.

--
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

[Bob Noel]

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!!!)

[WingFlaps]

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

[[email protected]]

In rec.aviation.piloting WingFlaps > wrote:
> 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.

The FAA radars are what they are.

You can arm wave forever about what they could be, but that isn't going
to change them.


--
Jim Pennino

Remove .spam.sux to reply.

[Larry Dighera]

On Sat, 03 May 2008 23:15:03 GMT, wrote in
>:

>
>
>The FAA radars are what they are.
>
>You can arm wave forever about what they could be, but that isn't going
>to change them.

But decommissioning them, as part of the ADS-B implementation, will
make them moot.

[Jennifer Allen[_3_]]

Larry Dighera wrote:

> On Sat, 03 May 2008 23:15:03 GMT, wrote in
> >:
>
> >
> >
> >The FAA radars are what they are.
> >
> >You can arm wave forever about what they could be, but that isn't going
> >to change them.
>
> But decommissioning them, as part of the ADS-B implementation, will
> make them moot.

What is being lost? Primary radar is making a comeback after 2001, not
going away.

[Larry Dighera]

On Sat, 03 May 2008 20:15:32 -0400, Jennifer Allen >
wrote in >:

>
>
>Larry Dighera wrote:
>
>> On Sat, 03 May 2008 23:15:03 GMT, wrote in
>> >:
>>
>> >
>> >
>> >The FAA radars are what they are.
>> >
>> >You can arm wave forever about what they could be, but that isn't going
>> >to change them.
>>
>> But decommissioning them, as part of the ADS-B implementation, will
>> make them moot.
>
>What is being lost? Primary radar is making a comeback after 2001, not
>going away.

I would enjoy reading supporting documentation for that assertion.


As this message thread refers to painting glider primary targets, it
would seem that post ADS-B, the FAA primary radars will be
decommissioned with the exception of those around the peripheral of
the US, hence my statement above.

http://72.14.253.104/search?q=cache:rZePC9G7HCAJ:www.library.unt.edu/gpo/NCARC/whitepaper/costsav.doc+%2Bads-b+%2Bfunding+%2Bdecommissioning+%2Bradar+%2Bfaa&hl=en&ct=clnk&cd=5&gl=us&client=firefox-a
Decommissioning only the primary radar would result in both cost
avoidance (no upgrades) and maintenance cost-savings. Annual savings
estimates are approximately $30M per year. (Note: For purposes of
national defense, the primary radars around the peripheral of the
United States, would not be decommissioned in the near term).



http://astra.aero/downloads/ABIT/ABIT07-Minutes_of_meeting_final.pdf
The FAA envisions decommissioning. more than 300 en route radars. ...



http://www.fcw.com/print/12_23/news/94989-1.html
Radar is an outdated technology, the FAA says. Moving to ADS-B will
let the agency eventually decommission some of the current ground
radars. According to an FAA report, radar is imperfect and sometimes
has trouble distinguishing airplanes from flocks of birds or patches
of rain.



http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast
FAA segment 3 (2015-2020)

ADS-B In equipage will be based on user perceived benefit, but is
expected to be providing increased situational awareness and
efficiency benefits within this segment. Those aircraft who choose to
equip in advance of any mandate will see benefits associated with
preferential routes and specific applications. Limited radar
decommissioning will begin in the time frame with an ultimate goal of
a 50% reduction in the Secondary Surveillance Radar infrastructure.



http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/enroute/surveillance_broadcast/program_office_news/media/Follow%20Up%20Contract%20Award_ADS-B%20Q&As_8-30-07_Final.pdf
Will there be a back-up system for ADS-B?

Yes, the FAA recognizes that a back-up system is needed in case of
problems with the satellite system. In 2006, a team from the FAA,
industry, and the military performed an analysis, taking into account
such things as the operational capability needed during an outage, the
length of time the back-up system would be expected to operate during
an outage, and any overlap between the back-up and ADS-B that would
result in a vulnerability. The agency adopted the team’s
recommendation to maintain about half the current network of
*secondary* radars as a back-up system in case of a GPS outage.

[Alan[_6_]]

In article > "Morgans" > writes:
>
>"Eric Greenwell" > wrote >
>> This corresponds with the Powersonic chart, so at -10C (15F), you have a 30%
>> loss of capacity. For winter flying, and spring or fall flying in places where
>> you can climb to, say, 10,000' agl, it's an important factor. Especially so,
>> when you know your encoder will likely be using it's heater, adding 50-150
>> milliamps to your current drain.
>
> Put a insulated cover around the battery, and the heat of discharge will keep
>it warm and the capacity up, unless it is seriously freakin' cold.

With a resistance of a few milliohms, a 1 amp discharge will only give a
few milliwatts of heat. I really doubt the battery will keep itself warm.
(After all warming the battery would consume energy from its stored capacity.)

Alan

[WingFlaps]

On May 4, 11:15*am, wrote:
> In rec.aviation.piloting WingFlaps > wrote:
>
> > 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.
>
> The FAA radars are what they are.
>

I agree

Cheers

[Bob Noel]

In article >,
Larry Dighera > wrote:

> >What is being lost? Primary radar is making a comeback after 2001, not
> >going away.
>
> I would enjoy reading supporting documentation for that assertion.
>
>
> As this message thread refers to painting glider primary targets, it
> would seem that post ADS-B, the FAA primary radars will be
> decommissioned with the exception of those around the peripheral of
> the US, hence my statement above.

I doubt that the primary radars in the US will be decommissioned

The air defense systems in the west (WADS) and the one in Rome, NY (NEADS)
have added the capability to take in feeds from domestic radars, including the
FAA enroute radars. This all occured post-9/11. (HI and AK systems also have
been upgraded). Search for Battle Control System Fixed.

Since before 1996, the FAA has been looking to get rid of primary radars.
9/11 was yet another excuse to try to get someone else to pay for the maintenance
and upgrades for NAS radars.


> http://www.fcw.com/print/12_23/news/94989-1.html
> Radar is an outdated technology, the FAA says. Moving to ADS-B will
> let the agency eventually decommission some of the current ground
> radars. According to an FAA report, radar is imperfect and sometimes
> has trouble distinguishing airplanes from flocks of birds or patches
> of rain.

As antiquated as RADAR is, I don't think we can rely on the "bad guys" using
cooperative surv technology like transponders or ADS-B out.

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

[Larry Dighera]

On Sun, 04 May 2008 08:47:53 -0400, Bob Noel
> wrote in
>:

>In article >,
> Larry Dighera > wrote:
>
>> >What is being lost? Primary radar is making a comeback after 2001, not
>> >going away.
>>
>> I would enjoy reading supporting documentation for that assertion.
>>
>>
>> As this message thread refers to painting glider primary targets, it
>> would seem that post ADS-B, the FAA primary radars will be
>> decommissioned with the exception of those around the peripheral of
>> the US, hence my statement above.
>
>I doubt that the primary radars in the US will be decommissioned
>
Although that is inconsistent with the FAA information cited in the
link I posted, we can only hope that your intuition is accurate It
would be a grave mistake in my lay opinion. I believe decommissioning
radars was only mentioned by the FAA as a hastily considered attempt
to overcome the financial disincentive of implementing ADS-B; while
we're speculating, it was probably initially suggested by the
contractor(s) who is(are) lobbying for NextGen.


>The air defense systems in the west (WADS) and the one in Rome, NY (NEADS)
>have added the capability to take in feeds from domestic radars, including the
>FAA enroute radars. This all occured post-9/11. (HI and AK systems also have
>been upgraded). Search for Battle Control System Fixed.
>

How do the upgrades you mention imply that primary radars, located
other than around the periphery of the US, may be spared
decommissioning?

>Since before 1996, the FAA has been looking to get rid of primary radars.
>9/11 was yet another excuse to try to get someone else to pay for the maintenance
>and upgrades for NAS radars.
>

Without primary radars there is no way, other than intercepts, of
knowing the true position of a flight. To intentionally lose that
empirical capability seems shortsighted. But then my opinion is only
based on incomplete knowledge of the system. Perhaps there are
alternate sources for such information (doubtful). For some reason
(possibly because contractors believe that if they don't mention it,
no one will notice) the loss of empirical flight location is not
addressed in the proposed ADS-B implementation.

>
>> http://www.fcw.com/print/12_23/news/94989-1.html
>> Radar is an outdated technology, the FAA says. Moving to ADS-B will
>> let the agency eventually decommission some of the current ground
>> radars. According to an FAA report, radar is imperfect and sometimes
>> has trouble distinguishing airplanes from flocks of birds or patches
>> of rain.
>
>As antiquated as RADAR is, I don't think we can rely on the "bad guys" using
>cooperative surv technology like transponders or ADS-B out.

Precisely.

Why is it that you and I are able to recognize that, and the FAA
cannot? What are we overlooking?

[Peter Dohm]

"Alan" > wrote in message
...
> In article > "Morgans"
> > writes:
>>
>>"Eric Greenwell" > wrote >
>>> This corresponds with the Powersonic chart, so at -10C (15F), you have a
>>> 30%
>>> loss of capacity. For winter flying, and spring or fall flying in places
>>> where
>>> you can climb to, say, 10,000' agl, it's an important factor. Especially
>>> so,
>>> when you know your encoder will likely be using it's heater, adding
>>> 50-150
>>> milliamps to your current drain.
>>
>> Put a insulated cover around the battery, and the heat of discharge will
>> keep
>>it warm and the capacity up, unless it is seriously freakin' cold.
>
> With a resistance of a few milliohms, a 1 amp discharge will only give a
> few milliwatts of heat. I really doubt the battery will keep itself warm.
> (After all warming the battery would consume energy from its stored
> capacity.)
>
> Alan

The greater problem might be a need to remove the problem during charging,
when a lot more heat is likely to be generated.

Peter

[Tony Verhulst]

> (After all warming the battery would consume energy from its stored capacity.)

Sure, but a warm battery can deliver more power than a really cold battery.

Tony V.

[Steven P. McNicoll[_2_]]

Bob Noel wrote:
>
> The air defense systems in the west (WADS) and the one in Rome, NY
> (NEADS) have added the capability to take in feeds from domestic radars,
> including the FAA enroute radars. This all occured post-9/11.
>

Initially, it was the other way round. Many of the present FAA enroute
radars are former ADC radars. The FAA expanded their enroute radar coverage
in the late fifties and early sixties by acquiring feeds on USAF radar.

[Martin Gregorie[_1_]]

On Sun, 04 May 2008 09:37:13 -0400, Peter Dohm wrote:

>
> The greater problem might be a need to remove the problem during charging,
> when a lot more heat is likely to be generated.
>
I use an automatic charger with bulk charge and float modes.
This unit is designed for 12v batteries in the 6-15Ah capacity range.
It outputs 14.7v at 1.5 amps in bulk mode. My batteries never even get
warm to the touch when on charge.

I'd suggest that if your batteries get hot on charge then there are only
three possibilities:

- you're using a fixed-rate charger with far too high a rate for
the battery.
- you're overcharging with a fixed-rate changer.
- your automatic charger is faulty.


--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot

[Bob Noel]

In article >,
Larry Dighera > wrote:

> >The air defense systems in the west (WADS) and the one in Rome, NY (NEADS)
> >have added the capability to take in feeds from domestic radars, including
> >the
> >FAA enroute radars. This all occured post-9/11. (HI and AK systems also
> >have
> >been upgraded). Search for Battle Control System Fixed.
> >
>
> How do the upgrades you mention imply that primary radars, located
> other than around the periphery of the US, may be spared
> decommissioning?

There would be little value in adding the ability to use the 200+ FAA primary
radars if they were going away soon. (ok, some of that 200+ number might be
beacon radar only)


> >As antiquated as RADAR is, I don't think we can rely on the "bad guys" using
> >cooperative surv technology like transponders or ADS-B out.
>
> Precisely.
>
> Why is it that you and I are able to recognize that, and the FAA
> cannot? What are we overlooking?

The FAA beancounters know that the FAA's responsibility does not include
tracking and identifying bad guys. The b'crats are only thinking about
their budget and ways to get other agencies to pay for things.

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

[Morgans[_2_]]

"Bob Noel" > wrote

> I doubt that the primary radars in the US will be decommissioned

> Since before 1996, the FAA has been looking to get rid of primary radars.
> 9/11 was yet another excuse to try to get someone else to pay for the
> maintenance
> and upgrades for NAS radars.

Is there a way that all of the TV station doppler weather radars could be made
to see airplanes, at the same time as looking at the weather?

I know they operate on different wavelengths, but could addition
transmitter/receivers be installed and used to supplement FAA radars?

Seems a shame to have all of those weather radars around, that could be helping
out tracking, or supplementing tracking aircraft.

I know there are probably a dozen reasons for this to not work, but could anyone
give a shot explaining what they are?
--
Jim in NC

[Frank Whiteley]

http://www.aopa.org/training/articles/2008/080508data.html