gliders+radar

[[email protected]]

Modern gliders are small and made of materials that show up poorly on
radar.

Are we basically flying stealth aircraft?

Johan Larson

[BTIZ]

A misnomer... I know for a fact that our LS-4 shows up on local approach
control radar.. as does the Grob 103, and the SGS1-26 and 2-33 is a dead
give away.

The problem is not the glider, its the relative motion. Software in the
"digital computer display" will filter out targets that appear not to be
moving to get rid of "clutter" or other atmospheric anomalies.. slow to
below 40knts straight line ground speed and you just may get filtered out
and not displayed.. core a tight thermal.. same effect.. less that 40knts
effective ground speed in a given direction and you will be filtered out and
not displayed... in this case.. "beaming to the doppler notch" is a bad
thing.. Military fliers will know what I mean.

I listen up on the local ATC Radar frequency and have talked to them on
occasions.. they have called me as traffic to other aircraft.. "traffic, 2
o'clock, 3 miles.. appears to be a glider, altitude unknown". Our local ATC
radar looses coverage about 4000ft AGL and below in the valley where our
glider club is.

If you really want to know you are seen, invest in a transponder with ModeC
and squawk 1200.

BT
(too many years on both sides of the radar)

> wrote in message
oups.com...
> Modern gliders are small and made of materials that show up poorly on
> radar.
>
> Are we basically flying stealth aircraft?
>
> Johan Larson
>

[[email protected]]

BTIZ wrote:
> If you really want to know you are seen, invest in a transponder with ModeC
> and squawk 1200.

Thanks for all the advice, but I think you mistake my intentions. I'm
practicing my short-landing technique on an outline of the White House
roof. ;-)

Johan Larson

[Bob]

That knock on your door is the NSA :o
> wrote in message
ups.com...
>
> BTIZ wrote:
>> If you really want to know you are seen, invest in a transponder with
>> ModeC
>> and squawk 1200.
>
> Thanks for all the advice, but I think you mistake my intentions. I'm
> practicing my short-landing technique on an outline of the White House
> roof. ;-)
>
> Johan Larson
>

[[email protected]]

Bob wrote:
> That knock on your door is the NSA :o

Heh. Blue eyes, white skin, and a name like a viking; I must be the
decoy.

But seriously, folks, www.acronymfinder.com turns up some very very
interesting phrases for "NSA"; but, I fear the phrase Non-surgical Spem
Aspiration may have stolen my naivete forever. :-(

Johan Larson

[Don Johnstone]

At 04:06 20 July 2006, wrote:
>
>Bob wrote:
>> That knock on your door is the NSA :o
>
>Heh. Blue eyes, white skin, and a name like a viking;
>I must be the
>decoy.

Vikings? Hells teeth, look at the problems they caused
over this side of the pond with their rape and pillage.
George Dunya better watch out if those babies are on
his case. :-)

[bumper]

For those Vikings out there, always remember it's, "Mayhem, Rape, Pillage,
and *then* Burn". The order in which one engages these activities being
relatively important to a successful raid.

Do you think Vikings used checklists?

bumper

"Don Johnstone" > wrote in message
...
> At 04:06 20 July 2006, wrote:
>>
>>Bob wrote:
>>> That knock on your door is the NSA :o
>>
>>Heh. Blue eyes, white skin, and a name like a viking;
>>I must be the
>>decoy.
>
> Vikings? Hells teeth, look at the problems they caused
> over this side of the pond with their rape and pillage.
> George Dunya better watch out if those babies are on
> his case. :-)
>
>
>

[Big John]

Johan

Look up Luneberg Lens via Google.

We hung them on T-33 target aircraft in exercies to give a radar
return the size of a B-47.

You could make one out of foam and Rennels (sp) Wrap and put inside
your plastic bird and get a much larger radar return for just a few
ounces for the lens.

These are passive devices and no power is required.

Big John
`````````````````````````````````````````````````` ````````````````

On 19 Jul 2006 18:25:38 -0700, wrote:

>Modern gliders are small and made of materials that show up poorly on
>radar.
>
>Are we basically flying stealth aircraft?
>
>Johan Larson

[Nyal Williams]

What kinda Rennels numbers would I get? Is this a new
kinda airfoil?

At 16:48 20 July 2006, Big John wrote:
>Johan
>
>Look up Luneberg Lens via Google.
>
>We hung them on T-33 target aircraft in exercies to
>give a radar
>return the size of a B-47.
>
>You could make one out of foam and Rennels (sp) Wrap
>and put inside
>your plastic bird and get a much larger radar return
>for just a few
>ounces for the lens.
>
>These are passive devices and no power is required.
>
>Big John
>`````````````````````````````````````````````````` ````````````````
>>
>
>On 19 Jul 2006 18:25:38 -0700,
>wrote:
>
>>Modern gliders are small and made of materials that
>>show up poorly on
>>radar.
>>
>>Are we basically flying stealth aircraft?
>>
>>Johan Larson
>
>

[Mike C 17]

http://www.sailorssolutions.com/index.asp?page=ProductDetails&Item=RR01


Big John wrote:
> Johan
>
> Look up Luneberg Lens via Google.
>
> We hung them on T-33 target aircraft in exercies to give a radar
> return the size of a B-47.
>
> You could make one out of foam and Rennels (sp) Wrap and put inside
> your plastic bird and get a much larger radar return for just a few
> ounces for the lens.
>
> These are passive devices and no power is required.
>
> Big John
> `````````````````````````````````````````````````` ````````````````
>
> On 19 Jul 2006 18:25:38 -0700, wrote:
>
> >Modern gliders are small and made of materials that show up poorly on
> >radar.
> >
> >Are we basically flying stealth aircraft?
> >
> >Johan Larson

[Bob Salvo]

Reflectivity is not the problem. We conducted experiments with Boston
control many years ago. They got good radar returns from our glass ships.
The problem is the slow speed we generally fly. Usually the center's radar
uses MTI (moving target indicator), which gets rid of ground clutter returns
and returns from flying birds. When Boston control deactivated the MTI
function, they could easily see us. Adding a lens to increase our
reflectivity would not help. But if we had doppler generator built into the
lens (maybe a spinning wheel propelled by air; we have lots of that
available), the lens would be removed from the clutter notch. Maybe :)


"Mike C 17" > wrote in message
oups.com...
> http://www.sailorssolutions.com/index.asp?page=ProductDetails&Item=RR01
>
>
> Big John wrote:
> > Johan
> >
> > Look up Luneberg Lens via Google.
> >
> > We hung them on T-33 target aircraft in exercies to give a radar
> > return the size of a B-47.
> >
> > You could make one out of foam and Rennels (sp) Wrap and put inside
> > your plastic bird and get a much larger radar return for just a few
> > ounces for the lens.
> >
> > These are passive devices and no power is required.
> >
> > Big John
> > `````````````````````````````````````````````````` ````````````````
> >
> > On 19 Jul 2006 18:25:38 -0700, wrote:
> >
> > >Modern gliders are small and made of materials that show up poorly on
> > >radar.
> > >
> > >Are we basically flying stealth aircraft?
> > >
> > >Johan Larson
>

[Mike Schumann]

Would the MTI also filter you out if you had a Mode C transponder?

Mike Schumann

"Bob Salvo" > wrote in message
. ..
> Reflectivity is not the problem. We conducted experiments with Boston
> control many years ago. They got good radar returns from our glass ships.
> The problem is the slow speed we generally fly. Usually the center's
> radar
> uses MTI (moving target indicator), which gets rid of ground clutter
> returns
> and returns from flying birds. When Boston control deactivated the MTI
> function, they could easily see us. Adding a lens to increase our
> reflectivity would not help. But if we had doppler generator built into
> the
> lens (maybe a spinning wheel propelled by air; we have lots of that
> available), the lens would be removed from the clutter notch. Maybe :)
>
>
> "Mike C 17" > wrote in message
> oups.com...
>> http://www.sailorssolutions.com/index.asp?page=ProductDetails&Item=RR01
>>
>>
>> Big John wrote:
>> > Johan
>> >
>> > Look up Luneberg Lens via Google.
>> >
>> > We hung them on T-33 target aircraft in exercies to give a radar
>> > return the size of a B-47.
>> >
>> > You could make one out of foam and Rennels (sp) Wrap and put inside
>> > your plastic bird and get a much larger radar return for just a few
>> > ounces for the lens.
>> >
>> > These are passive devices and no power is required.
>> >
>> > Big John
>> > `````````````````````````````````````````````````` ````````````````
>> >
>> > On 19 Jul 2006 18:25:38 -0700, wrote:
>> >
>> > >Modern gliders are small and made of materials that show up poorly on
>> > >radar.
>> > >
>> > >Are we basically flying stealth aircraft?
>> > >
>> > >Johan Larson
>>
>
>

[[email protected]]

Mike Schumann wrote:
> Would the MTI also filter you out if you had a Mode C transponder?

Mike, AIUI there are two quite different radar types. The originals,
now know as Primary Radar, send out a signal and deduce your range and
direction (azimuth) from a reflection. That sort does not know whether
you have a transponder or not, reflections could be improved by large
enough Luneberg lenses (of dubious benefit for the size we could get
into a glider fuselage), and is subject to MTI if they switch it on.
Also, on a visit to Stansted UK (London's "third" airport) some years
ago, their ATC explained to me that not only did it fail to see slow
moving targets when MTI was on - which it almost always was, to reduce
screen clutter; it was also blind to anything with a radial speed
towards or away from the radar head at certain harmonics of the wave
length - in practice at 37.5 knots, 75 knots, and multiples. So even
with MTI off, thermalling gliders that were good reflectors would be
invisible half the time, and cruising towards or away from them would
also reduce or eradicate their trace of us.

Transponders use SSR (Secondary Surveillance Radar) which sends out an
APB to all transponders within range - "Oi, anyone out there?" to which
they all respond. No transponder, no response, SSR cannot see you.
With Mode S (for Selective), the Controller can then tweak it to say
next time around "Oi, only those transponders I have Selected - where
are you now?". Gliders etc. not so selected will then not be seen by
ATC. This has three effects (at least):

They have less cluttered screens, seeing only those that they want to
for control purposes;

Each Mode S transponder has a unique code identifying it to the
aircraft it is in, so they never run out of codes (unlike Modes A and
C, where Europe already has problems, because the existing 7xxx - type
codes are too few for ATC's purposes);

And transponders NOT selected by ATC would not be made to transmit a
signal zillions of times per second like a Mode A or C is, only say
once per second, so they still show up to TCAS units in the area but
save a lot of power compared with Mode A or C. This seems to be why,
in Europe at least, the authorities are looking at Mode S, rather than
A or C, as a mandatory standard. They know gliders would never have
enough power for Mode A or C with the expected growth in utilisation of
airspace and hence growing number of interrogations making transponders
squawk.

TCAS etc. in airliners etc., however, will still see all transponders
within their range, so will still give collision avoidance in respect
of gliders.

Hope that helps. Any experts care to correct this if necessary?

Chris N.

[Big John]

Mike

Make one for pennies and few Oz vs 2.2# and $139.95.

Big John
`````````````````````````````````````````````````` ``````````

On 20 Jul 2006 14:36:09 -0700, "Mike C 17" >
wrote:

>http://www.sailorssolutions.com/index.asp?page=ProductDetails&Item=RR01
>
>
>Big John wrote:
>> Johan
>>
>> Look up Luneberg Lens via Google.
>>
>> We hung them on T-33 target aircraft in exercies to give a radar
>> return the size of a B-47.
>>
>> You could make one out of foam and Rennels (sp) Wrap and put inside
>> your plastic bird and get a much larger radar return for just a few
>> ounces for the lens.
>>
>> These are passive devices and no power is required.
>>
>> Big John
>> `````````````````````````````````````````````````` ````````````````
>>
>> On 19 Jul 2006 18:25:38 -0700, wrote:
>>
>> >Modern gliders are small and made of materials that show up poorly on
>> >radar.
>> >
>> >Are we basically flying stealth aircraft?
>> >
>> >Johan Larson

[Big John]

Bob

I played with rotating Lens some years ago in a project to develope a
high speed radar return that could be detected by Police Radar
Detectors without the results I wanted. I wanted to 'pin the needle'
on detector at max so true speed wouldn't show. (I'm a dirty old man
:o)

Your idea for gliders might work? Not expensive to try/test.

Big John
``````````````````````````````````````
On Thu, 20 Jul 2006 20:43:39 -0400, "Bob Salvo"
> wrote:

>Reflectivity is not the problem. We conducted experiments with Boston
>control many years ago. They got good radar returns from our glass ships.
>The problem is the slow speed we generally fly. Usually the center's radar
>uses MTI (moving target indicator), which gets rid of ground clutter returns
>and returns from flying birds. When Boston control deactivated the MTI
>function, they could easily see us. Adding a lens to increase our
>reflectivity would not help. But if we had doppler generator built into the
>lens (maybe a spinning wheel propelled by air; we have lots of that
>available), the lens would be removed from the clutter notch. Maybe :)
>
>
>"Mike C 17" > wrote in message
oups.com...
>> http://www.sailorssolutions.com/index.asp?page=ProductDetails&Item=RR01
>>
>>
>> Big John wrote:
>> > Johan
>> >
>> > Look up Luneberg Lens via Google.
>> >
>> > We hung them on T-33 target aircraft in exercies to give a radar
>> > return the size of a B-47.
>> >
>> > You could make one out of foam and Rennels (sp) Wrap and put inside
>> > your plastic bird and get a much larger radar return for just a few
>> > ounces for the lens.
>> >
>> > These are passive devices and no power is required.
>> >
>> > Big John
>> > `````````````````````````````````````````````````` ````````````````
>> >
>> > On 19 Jul 2006 18:25:38 -0700, wrote:
>> >
>> > >Modern gliders are small and made of materials that show up poorly on
>> > >radar.
>> > >
>> > >Are we basically flying stealth aircraft?
>> > >
>> > >Johan Larson
>>
>

[Big John]

Cris

FYI. The Lens used on our target aircraft in Air Force were only about
one foot in diameter. Not very big.

Return simuated aircraft size of B-47.

Big John


On 21 Jul 2006 04:13:37 -0700, wrote:

>
>Mike Schumann wrote:
>> Would the MTI also filter you out if you had a Mode C transponder?
>
>Mike, AIUI there are two quite different radar types. The originals,
>now know as Primary Radar, send out a signal and deduce your range and
>direction (azimuth) from a reflection. That sort does not know whether
>you have a transponder or not, reflections could be improved by large
>enough Luneberg lenses (of dubious benefit for the size we could get
>into a glider fuselage), and is subject to MTI if they switch it on.
>Also, on a visit to Stansted UK (London's "third" airport) some years
>ago, their ATC explained to me that not only did it fail to see slow
>moving targets when MTI was on - which it almost always was, to reduce
>screen clutter; it was also blind to anything with a radial speed
>towards or away from the radar head at certain harmonics of the wave
>length - in practice at 37.5 knots, 75 knots, and multiples. So even
>with MTI off, thermalling gliders that were good reflectors would be
>invisible half the time, and cruising towards or away from them would
>also reduce or eradicate their trace of us.
>
>Transponders use SSR (Secondary Surveillance Radar) which sends out an
>APB to all transponders within range - "Oi, anyone out there?" to which
>they all respond. No transponder, no response, SSR cannot see you.
>With Mode S (for Selective), the Controller can then tweak it to say
>next time around "Oi, only those transponders I have Selected - where
>are you now?". Gliders etc. not so selected will then not be seen by
>ATC. This has three effects (at least):
>
> They have less cluttered screens, seeing only those that they want to
>for control purposes;
>
> Each Mode S transponder has a unique code identifying it to the
>aircraft it is in, so they never run out of codes (unlike Modes A and
>C, where Europe already has problems, because the existing 7xxx - type
>codes are too few for ATC's purposes);
>
> And transponders NOT selected by ATC would not be made to transmit a
>signal zillions of times per second like a Mode A or C is, only say
>once per second, so they still show up to TCAS units in the area but
>save a lot of power compared with Mode A or C. This seems to be why,
>in Europe at least, the authorities are looking at Mode S, rather than
>A or C, as a mandatory standard. They know gliders would never have
>enough power for Mode A or C with the expected growth in utilisation of
>airspace and hence growing number of interrogations making transponders
>squawk.
>
>TCAS etc. in airliners etc., however, will still see all transponders
>within their range, so will still give collision avoidance in respect
>of gliders.
>
>Hope that helps. Any experts care to correct this if necessary?
>
>Chris N.

[BTIZ]

no... because you are sending a coded reply to a specific interrogation.
BT

"Mike Schumann" > wrote in message
ink.net...
> Would the MTI also filter you out if you had a Mode C transponder?
>
> Mike Schumann
>
> "Bob Salvo" > wrote in message
> . ..
>> Reflectivity is not the problem. We conducted experiments with Boston
>> control many years ago. They got good radar returns from our glass
>> ships.
>> The problem is the slow speed we generally fly. Usually the center's
>> radar
>> uses MTI (moving target indicator), which gets rid of ground clutter
>> returns
>> and returns from flying birds. When Boston control deactivated the MTI
>> function, they could easily see us. Adding a lens to increase our
>> reflectivity would not help. But if we had doppler generator built into
>> the
>> lens (maybe a spinning wheel propelled by air; we have lots of that
>> available), the lens would be removed from the clutter notch. Maybe :)
>>
>>
>> "Mike C 17" > wrote in message
>> oups.com...
>>> http://www.sailorssolutions.com/index.asp?page=ProductDetails&Item=RR01
>>>
>>>
>>> Big John wrote:
>>> > Johan
>>> >
>>> > Look up Luneberg Lens via Google.
>>> >
>>> > We hung them on T-33 target aircraft in exercies to give a radar
>>> > return the size of a B-47.
>>> >
>>> > You could make one out of foam and Rennels (sp) Wrap and put inside
>>> > your plastic bird and get a much larger radar return for just a few
>>> > ounces for the lens.
>>> >
>>> > These are passive devices and no power is required.
>>> >
>>> > Big John
>>> > `````````````````````````````````````````````````` ````````````````
>>> >
>>> > On 19 Jul 2006 18:25:38 -0700, wrote:
>>> >
>>> > >Modern gliders are small and made of materials that show up poorly
>>> > >on
>>> > >radar.
>>> > >
>>> > >Are we basically flying stealth aircraft?
>>> > >
>>> > >Johan Larson
>>>
>>
>>
>
>

[BTIZ]

Yes... depends on the clutter... talk to a military pilot about "direct
terrain masking"

"Mike C 17" > wrote in message
ups.com...
> After reading the various posts here, the question arises-Will a radar
> image be lost in clutter if it is the size of a B-47, due to the speed
> of the aircraft?
>
> Mike
>

[Bob Salvo]

Only if the clutter is moving at the same speed. ;)

"Mike C 17" > wrote in message
ups.com...
> After reading the various posts here, the question arises-Will a radar
> image be lost in clutter if it is the size of a B-47, due to the speed
> of the aircraft?
>
> Mike
>

[Martin Gregorie[_1_]]

Big John wrote:
> Mike
>
> Make one for pennies and few Oz vs 2.2# and $139.95.
>
I did a search for info about Luneberg Lenses - found plenty of
definitions/explanations/units for sale but nothing on DIY Luneberg,
how to make a ball with a radially varying refractive index or sources
of materials with suitable refractive index gradations.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Capt. Geoffrey Thorpe]

"Martin Gregorie" > wrote in message
...
> Big John wrote:
>> Mike
>>
>> Make one for pennies and few Oz vs 2.2# and $139.95.
>>
> I did a search for info about Luneberg Lenses - found plenty of
> definitions/explanations/units for sale but nothing on DIY Luneberg, how
> to make a ball with a radially varying refractive index or sources of
> materials with suitable refractive index gradations.
>
>
> --
> martin@ | Martin Gregorie
> gregorie. | Essex, UK
> org |

A corner reflector is easy and effective...

<http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/142806/0/0/radar%20reflector/All_2/mode+matchallpartial/0/0>

If you make one out of foam core board and aluminium foil, be sure to keep
all the angles at 90 degrees. The overall shape can be whatever you want.


--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Eric Greenwell[_1_]]

Ian wrote:
> On Fri, 21 Jul 2006 04:47:04 +0000, Mike Schumann wrote:
>
>> Would the MTI also filter you out if you had a Mode C transponder?
>
> Yes, it can do, depending on the settings of the filters. We had this
> problem with the ATC at Cape Town International in South Africa.
>
> There was a problem with Mode C Transponder equipped gliders flying in
> wave, disappearing off the radar screens. The problem was found to be due
> to speed filters in place on the equipment. Worse still the controllers
> had call a technician if they wanted the filters adjusted. As I understand
> the filters were set to filter out aircraft taxing on the ground at low
> speed.
>
> The local pilots and the controllers are now aware of the problem and the
> radar has since been upgraded so this problem is under control.
>
> But the problem is worth knowing about if you have a transponder in your
> glider.

I'm not aware of this being a problem the USA. As I understand it, the
taxiing problem can be dealt with by by using proximity and altitude
filters, not speed filters. I'm told there are places where aircraft
squawking the VFR code (1200) may be filtered out, such as the Los
Angeles airspace, but these (very few) places are not where we are soaring!


--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

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

[Martin Gregorie[_1_]]

Capt. Geoffrey Thorpe wrote:
> "Martin Gregorie" > wrote in message
> ...
>> Big John wrote:
>>> Mike
>>>
>>> Make one for pennies and few Oz vs 2.2# and $139.95.
>>>
>> I did a search for info about Luneberg Lenses - found plenty of
>> definitions/explanations/units for sale but nothing on DIY Luneberg, how
>> to make a ball with a radially varying refractive index or sources of
>> materials with suitable refractive index gradations.
>>
>>
>> --
>> martin@ | Martin Gregorie
>> gregorie. | Essex, UK
>> org |
>
> A corner reflector is easy and effective...
>
> <http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/142806/0/0/radar%20reflector/All_2/mode+matchallpartial/0/0>
>
> If you make one out of foam core board and aluminium foil, be sure to keep
> all the angles at 90 degrees. The overall shape can be whatever you want.
>
>
> --
> Geoff
> The Sea Hawk at Wow Way d0t Com
> remove spaces and make the obvious substitutions to reply by mail
> When immigration is outlawed, only outlaws will immigrate.
>
>
Indeed. They've been discussed here in the past.

I think a Luneberg is not omnidirectional because the side with the
reflector on it will block incoming signals from that side, hence the
natty marine three-ball unit that gives 360 degree coverage. If I'm
right, you'd need to add another two balls (facing up and down) for
omnidirectional reflection.

OTOH a "spherical" corner reflector made from three equal sized disks of
of coreboard set at right angles (hence forming eight corner reflectors)
should be omnidirectional and probably lighter too.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |