U.K. near-midairs

On 26 Nov 2004 01:37:03 GMT, Nyal Williams
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

"Ralph Jones" wrote in message
...
On 26 Nov 2004 01:37:03 GMT, Nyal Williams
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

I dunno how slow the moving target filter is.

I was working Holoman AFB approach inbound for ALM when they called out a
"large, slow moving target at 12 O'clock, five miles". I looked and saw
nothing in the severe clear. "How large?", I asked. "Really big, sir", came
the reply.

Now the Tularosa Basin is known for its UFO sightings. Maybe I'm going to
see one. I'm thinking a Klingon Bird of Prey with the cloaking device on
'cause I can see all the way to Mexico in the 12 O'clock direction.

Finally, I noticed a line of 18 wheelers northbound on Route 54. "Approach,
does your radar see trucks?" I asked. "Sometimes, sir", came the reply.
Oh, well. Maybe they should require trucks to have transponders.

Bill Daniels

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.

"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?

Ralph Jones wrote:

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

They do not see sailplanes that are thermaling -- tested by Halifax
International Airport controllers

I'm aware of one airplane/glider collision in the UK
not with 4 miles of the gliders base. A piston single
cruising at about 140 knots ran into the back of a
std cirrus on a staight glide. If I remeber correctlythe
glider pilot was probably killed by the aircrafts propeller.
I think the airplane pilot survived.

I'm also aware of one in the UK and one in the USA
where, although near the gliders base airports, both
involved transiting powered airplanes - so not 'landing
related'. In both cases the powered airplane removed
the outboard few feet of the gliders wing. Both gliders
landed safely, both airplane pilots were killed.

Some years ago, as part of a discussion with officialdom
about proposed increases in regulated airspace, I did
a calculation that suggested that incidents that one
might expect an airplane pilot to report as a near
miss (which I reckoned was passing within 500 feet
vertically and 300 yards horizontally of another aircraft
and not seeing early enough to take avoiding action)
would occur about 1000 times more often than actual
collisions.

At 20:30 25 November 2004, Mark James Boyd wrote:
Peter Seddon wrote:
'Gliders in the U.K. were involved in 10 near-midairs

The difference between a mid-air and a near-midair
is
certainly an interesting topic. While in contact with
ATC
in busy airspace I've frequently had jittery airline
FOs
call me as threatening traffic over a mile away. I'd
guess if you're an airline guy and you see ANY aircraft,
and it wasn't on your TCAS, you'd just automatically
call it
a near-midair.

In the US, I'm not aware of any ACTUAL midair collisions
between a
glider and non-glider that are more than 4 miles from
an airport.

I know of lots and lots of talk about near-midairs,
and significant
pressure by the airlines to require transponders in
more
ways. Can we blame them? The FIRST mid-air could
result
in hundreds of deaths...

So there hasn't been one yet, and it's very hard to
tell
how close we've REALLY been to having a glider-airplane
midair
that wasn't very near an airport traffic pattern or
approach.
I'm guessing this is trivial, and requiring transponders
in gliders is a solution looking for a problem.

Have there been any actual airplane-glider midairs
in the UK
that weren't takeoff/landing related (within 4 miles
of the airport)?

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...ull.html#18860
0


e.g.,

Perhaps spam can pilots should look out of the window
more often!!

Another possibility is a radar reflector installed
in the glider.
These things are much cheaper than a transponder, and
would give at least
some info...

I'd love to see if my local boating supply shop has
one that would fit
--

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

Our local Class B airport.. DOES see gliders as they thermal.. they know we
are based south of the Class B and keep an eye out.. primary radar returns..
SGS2-33, 1-26 (lots of metal), Grob 103 and LS4 are all seen on their radar.

It could be your local Halifax controllers are not trying, have to many
filters turned on.. or are just not experienced in radar operation.

BT


"Charles Yeates" wrote in message
...
Ralph Jones wrote:

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

They do not see sailplanes that are thermaling -- tested by Halifax
International Airport controllers

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.

I'm sure I've seen an article about anti-collision
radar available for corporate aircraft. I believe
that they are available, but am unsure how prevalent
they are. There was some comment about this in AOPA(?)
mag a couple of years ago.

At 18:00 26 November 2004, Btiz wrote:
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:

It could be your local Halifax controllers are not trying, have to many
filters turned on.. or are just not experienced in radar operation.


It is the filter settings -- they don't want to see birds {:))