U.K. near-midairs

Carl J. Niedermeyer wrote:

I believe the accident Eric is referring to occurred in 1978 between a
Piper PA-32R (Lance or Saratoga, I forget which) and my partner flying
our LS1-f. 5 people were killed, no surviviors.

http://www.ntsb.gov/ntsb/brief.asp?ev_id=39335&key=0

Amazing how long ago this accident happened.

Hmmm...the accident reports don't indicate if this was very near a
gliderport or near Moses Lake (the Piper's departure point).

I'd be interested in more details, if they are available. I suppose
the altitude of the collision is unknown...
--

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Mark J. Boyd

At 20:30 25 November 2004, Mark James Boyd wrote:

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
--

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Mark J. Boyd

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.

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

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

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

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 {:))

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.

This is quite variable, depending on the radar and the operator, but if
you present a bigger primary return, your chances are improved. The
filtering may be adjustable, so if you contact them by radio, they are
more likely to get you on the radar.


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

Eric Greenwell
Washington State
USA

On Fri, 26 Nov 2004 21:22:05 UTC, Eric Greenwell
wrote:

: This is quite variable, depending on the radar and the operator, but if
: you present a bigger primary return, your chances are improved.

Absolutely. No one ever became less visible with a radar reflector...

Ian
--

Nyal Williams wrote:

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.

I'll let you know...
--

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Mark J. Boyd