U.K. near-midairs

On Fri, 26 Nov 2004 01:37:03 UTC, Nyal Williams
wrote:

: Boating stores sell radar reflectors made of cardboard
: and covered with aluminum foil.

I have never seen a cardboard one, but I do have a light alloy one on
the boat.

: I inquired about their use in gliders (practically
: no weight and could go in fuselage behind wing) and
: someone told me they would not give a strong enough
: signal for aircraft use owing to the speeds involved.

I have heard that a military ATC who visited one site where I fly said
that it would make a considerable improvement to the radar return from
a glider. It's on my list of things to do.

Ian

: I inquired about their use in gliders (practically
: no weight and could go in fuselage behind wing) and
: someone told me they would not give a strong enough
: signal for aircraft use owing to the speeds involved.

I have heard that a military ATC who visited one site where I fly said
that it would make a considerable improvement to the radar return from
a glider. It's on my list of things to do.

Ian

You could fly a tin AC!!! ;-)

Peter
Pilatus B4

Imagine this scenario.
A gliding competition in southern England with 100+ gliders all with
transponders, Plus non competition gliders flying with transponders, Plus light
aircraft flying VFR, Plus commercial, Plus military all with transponders
bleeping away.

The poor chap on the Radar would have a totally confused picture. The
authorities would then want to make sense of it because they look so close
together on the screen, all these people flying VFR outside controlled
airspace.

Before we know where we are there will be NO uncontrolled airspace and since
gliders cannot maintain nice neat constant heights and headings they would be
banned.
Paranoid me? Maybe

At 03:00 26 November 2004, Ralph Jones wrote:


[snip]

Boating stores sell radar reflectors made of cardboard
and covered with aluminum foil. They are in three
parts and can be disassembled. When put together they
make a sphere about 12-14 inches across and they provide
the 3D right triangles that are supposed to reflect
a signal back.

I inquired about their use in gliders (practically
no weight and could go in fuselage behind wing) and
someone told me they would not give a strong enough
signal for aircraft use owing to the speeds involved.
I have no idea about the validity of this statement.
Couldn't hurt to try it.

That is a corner reflector: three flat, mutually perpendicular
surfaces. It has the special geometric property that
a signal striking
it from any direction will reflect from surface to
surface and wind up
going back exactly the way it came. On radar, it looks
much larger
than an irregular-shaped object the same size.

Apollo crews left at least one optical corner reflector
on the moon,
and astronomers can bounce laser light off it to make
precision
orbital measurements.

Signal strength is not the problem: a fiberglass ship
with a one-foot
corner reflector inside it will look bigger than a
metal sailplane.
The bad news: air traffic control radars are 'moving
target' systems,
which means they filter out returns that don't have
any Doppler shift
to indicate a moving object. I don't know what the
minimum detectable
speed is, but if you're under it, they just won't see
you.

rj



What about the radars in corporate aircraft? If they
can pick it up I might consider stuffing one in the
Discus.

Nyal, corporate radars are WX radars and not designed to me air-to-air
intercept radars..

you'd be better off stuffing in a transponder for their TCAS and for ATC to
really see you.

BT

"Nyal Williams" wrote in message
...
At 03:00 26 November 2004, Ralph Jones wrote:


[snip]

Boating stores sell radar reflectors made of cardboard
and covered with aluminum foil. They are in three
parts and can be disassembled. When put together they
make a sphere about 12-14 inches across and they provide
the 3D right triangles that are supposed to reflect
a signal back.

I inquired about their use in gliders (practically
no weight and could go in fuselage behind wing) and
someone told me they would not give a strong enough
signal for aircraft use owing to the speeds involved.
I have no idea about the validity of this statement.
Couldn't hurt to try it.

That is a corner reflector: three flat, mutually perpendicular
surfaces. It has the special geometric property that
a signal striking
it from any direction will reflect from surface to
surface and wind up
going back exactly the way it came. On radar, it looks
much larger
than an irregular-shaped object the same size.

Apollo crews left at least one optical corner reflector
on the moon,
and astronomers can bounce laser light off it to make
precision
orbital measurements.

Signal strength is not the problem: a fiberglass ship
with a one-foot
corner reflector inside it will look bigger than a
metal sailplane.
The bad news: air traffic control radars are 'moving
target' systems,
which means they filter out returns that don't have
any Doppler shift
to indicate a moving object. I don't know what the
minimum detectable
speed is, but if you're under it, they just won't see
you.

rj



What about the radars in corporate aircraft? If they
can pick it up I might consider stuffing one in the
Discus.

BTIZ wrote:

you'd be better off stuffing in a transponder for their TCAS and for ATC to
really see you.

I think we all understand that putting in a transponder and a
big battery is a more complete solution. I think those
on this thread are simply looking at the lower tech, less expensive,
no recurrent certification alternatives.

At $50 and one pound, this looks pretty good. At $1000 and
10 pounds (including the extra battery) + $160/every two years,
I suspect we'd see fewer takers.

I personally also love the idea of the "star" multi-faceted
reflective tape. I despise the green and light grey color of
my current airplane, for example.

Cheap, passive, low cost solutions have a sort of engineering elegance,
don't you think?

--

------------+
Mark J. Boyd

Mark James Boyd wrote:
+ $160/every two years,

It's more like $75-100 every two years, as a transponder in a glider
just needs VFR certification (i.e., no static leak-down test).

Marc

In the USA there are simple and fatal flaws with any system that
includes ground based radar and a controller near a high density airport.

First, as already mentioned, the controller's normal display is
processed information. The is often referred to as secondary radar.
Basically it is just the transponder equipped traffic with data tags.

Second, as already mentioned, the system is normally configured to drop
out targets that have a low ground speed or don't have a ground track
that is going somewhere (e.g. circling). So a radar reflector wouldn't
be much help. It isn't the size of the return that gets the target
filtered out under these circumstances.

Third, and probably the greatest problem, if there are too many 12XX
returns (VFR transponder equipped traffic in the USA) the controller can
filter the specific codes or blocks of codes.

The was a mid-air between a commuter flight and a skydiving jump plane
between Denver CO and Cheyenne WY about 15 or 20 years ago. The
commuter flew into the climbing jump plane. Since they we both above
12,500 MSL (about 7,000 AGL), it was assumed the commuter pilots were
heads down in the cockpit. The jump plane was using a transponder code
of 1234 and ATC had 12XX code filtered for the higher altitudes. The
jump plane was not talking to ATC. Oops...

Other than a TCAS installation (aircraft to aircraft), the only way a
transponder will help us is if the ATC facility in the area knows about
the glider operations and can (or will) operate their equipment in a
manner that allows the controller to see the glider traffic. That means
we have to work with the local ATC folks. Otherwise, it is so much extra
ballast and power draw in the glider.

Even when the technology should help, local procedures can negate the
technology. Since the way we operate gliders does not fit in the
general transportation model the ATC system is designed to support,
putting a transponder into a glider without working with the affected
ATC organization does little to help the situation.

Dave Rolley

Mark James Boyd wrote:
BTIZ wrote:

you'd be better off stuffing in a transponder for their TCAS and for ATC to
really see you.


I think we all understand that putting in a transponder and a
big battery is a more complete solution. I think those
on this thread are simply looking at the lower tech, less expensive,
no recurrent certification alternatives.

At $50 and one pound, this looks pretty good. At $1000 and
10 pounds (including the extra battery) + $160/every two years,
I suspect we'd see fewer takers.

I personally also love the idea of the "star" multi-faceted
reflective tape. I despise the green and light grey color of
my current airplane, for example.

Cheap, passive, low cost solutions have a sort of engineering elegance,
don't you think?

--

------------+
Mark J. Boyd

Dave Rolley wrote:
In the USA there are simple and fatal flaws with any system that
includes ground based radar and a controller near a high density airport.

First, as already mentioned, the controller's normal display is
processed information. The is often referred to as secondary radar.
Basically it is just the transponder equipped traffic with data tags.

Second, as already mentioned, the system is normally configured to drop
out targets that have a low ground speed or don't have a ground track
that is going somewhere (e.g. circling). So a radar reflector wouldn't
be much help. It isn't the size of the return that gets the target
filtered out under these circumstances.

Third, and probably the greatest problem, if there are too many 12XX
returns (VFR transponder equipped traffic in the USA) the controller can
filter the specific codes or blocks of codes.

These may be "simple" flaws, but they aren't "fatal" to transponder
equipped gliders:

#1 this isn't a problem for transponder equipped aircraft, since they
will show on the display along with their data tag. Primary returns may
not be displayed, depending on the situation; however, if you call ATC,
they may be able and willing to put your primary return on the screen.

#2 doesn't apply to transponder equipped aircraft, as they are not
filtered by speed or track, but may apply to aircraft without
transponders, as primary returns may be filtered by speed or track.
Filtering out transponder

#3 applies in only a very few, very high density areas that gliders
aren't likely to be flying in, such as the area near LAX (Los Angles).

The was a mid-air between a commuter flight and a skydiving jump plane
between Denver CO and Cheyenne WY about 15 or 20 years ago. The
commuter flew into the climbing jump plane. Since they we both above
12,500 MSL (about 7,000 AGL), it was assumed the commuter pilots were
heads down in the cockpit. The jump plane was using a transponder code
of 1234 and ATC had 12XX code filtered for the higher altitudes. The
jump plane was not talking to ATC. Oops...

Errors happen, and this has got to be a rare one, where both ATC and the
jump plane make them. I've asked the controllers at Seattle Center if
they ever filter out VFR code 1200 - "NO SIR"! The jump plane flying out
of our airport gets every transponder equipped aircraft (including my
glider) called out to him before he lets any jumpers loose.

Other than a TCAS installation (aircraft to aircraft),

This is actually the BEST reason to carry a transponder - so airliners
in particular, but also many corporate aircraft and military aircraft
can avoid you!

the only way a
transponder will help us is if the ATC facility in the area knows about
the glider operations and can (or will) operate their equipment in a
manner that allows the controller to see the glider traffic. That means
we have to work with the local ATC folks. Otherwise, it is so much extra
ballast and power draw in the glider.

THis is definitely NOT true. ATC is operating their equipment so they
can track VFR aircraft (that includes you in your glider), and they
don't need to know if it's an airplane or a glider. If they can see the
airplanes, they'll see you, even if you are circling or moving slowly.


Even when the technology should help, local procedures can negate the
technology. Since the way we operate gliders does not fit in the
general transportation model the ATC system is designed to support,
putting a transponder into a glider without working with the affected
ATC organization does little to help the situation.

The essence of the VFR 1200 code is that ATC _doesn't_ need to "work"
with you: that's why it's a "VFR" code. You just fly around, minding
your own business like the airplanes flying VFR, and their radar will
pick you up. They want to know where the VFR traffic is so they can
direct the IFR traffic away from it. Folks, we aren't that special. The
only place in the USA that I know of that has a different situation is
at Reno, where gliders may use the 0440 code to identify themselves as a
glider. It's not required that gliders use it, only that they are
allowed to use it as an aid to the Reno controllers. If you use 1200,
they'll still see you.

Note that it's not just the IFR and TCAS traffic that can be steered
away from you, but also VFR aircraft using "flight following", and the
already mentioned skydivers.

If you think you need a transponder, but are concerned that it will be
just "so much extra ballast and power draw", please, please, contact the
ATC in your flying area and ask them if they will see you on their
radar! My experience is they will be delighted to have you equipped with
one.


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

Eric Greenwell
Washington State
USA

"Gliders in the U.K. were involved in 10 near-midairs
in the second half of last year, safety investigators
said recently, noting that newer models fly at high
altitudes without transponders and are hard to see,
both visually and on radar...."

http://www.avweb.com/eletter/archive...ll.html#188600


e.g., http://news.bbc.co.uk/1/hi/wales/mid/3763766.stm







Can we believe any of this? A classic case of chinese whispers. Avweb quoting
the BBC quoting unamed MOD officials who are reporting on airmiss reports filed
by power pilots. We all know the perception of an airmiss by some power pilots
is completely different to what glider pilots understand.
I was speaking to one last summer who had just come down from a trial lesson
thermalling with about 12 other gliders.(not unusual at our site) and he was
nearly having kittens.

I am not saying that near misses do not happen between power and gliders but in
my experience gliders are far more aware of what is going on outside the
cockpit. The case of the fast jet pilot nearly hitting two gliders over the
gliding site at Talgarth at 500ft is a case in point. If he could not see the
gliders in plent of time he was going too fast, too low and in the wrong area.
Are powered aircraft not supposed to give way to gliders, balloons etc?