[AU] Light plane sparked terror alert

Peter and Susan wrote:
I have been waiting for someone to mention the drug runner intercepted or
chased by the RAAF C130 [?] up around Darwin many years ago.
Something about
relative speeds and the C130 having to slow down enough?

All the RAAF could possibly do is to track it and wait for it to land.
They would have to call in police or Customs to make an arrest.

Cheers
David

On Mon, 1 Sep 2003 11:51:53 +0100, "Keith Willshaw"
wrote:


"matt weber" wrote in message
.. .
On Sun, 31 Aug 2003 11:11:10 +0100, "Keith Willshaw"
wrote:


"matt weber" wrote in message
.. .
On Sat, 30 Aug 2003 12:18:13 +0100, "Keith Willshaw"
wrote:


They show up on most ATC radars only because they have a transponder.

Nonsense they show up on primary radar very well

Note the difficulties US ATC had in locating 757's and 767's on 9/11
after the transponders were turned off, and 757 or 767 has a far far
larger radar cross section than a single engine cessna.


Again this is nonsense, the radar tracks of those aircraft have been
produced in evidence primary radar is more than adequate
It is more then adequate, as long as they never get more than about 35
miles away from the RADAR.


Actual range depends on height, RCS , transmitted power and
the sensitivity of the radar, However its a matter of historical
fact that during WW2 the primitive Chain Home system could
detect aircraft out to 200 miles

http://www.radarpages.co.uk/mob/chl/chl.htm

However your original claim was that they couldnt be seen
at all unless they had a transponder !

After that, the combination of the inverse square law, and the very
limited RCS of many light aircraft makes them just about impossible to
see. that is one of the reasons that ATC in the USA also receives data
from far more capable military RADAR systems that are not limited by
Civilian energy exposure limits.


Come now make up your mind , are they impossible to see
or is it just that the range is limited ?

Most of the track data for both JFK Jr's crash, and the EgyptAir crash
came not from civilian ATC radars, but Military Radars which share
data with ATC.

I suggest you do the arithmetic sometime on what sort of power you
need to radiate to be able to get a reliably detectable return on a 1
m^2 RCS at 50km. 1m^2 is fairly typical of Cessa single. Some of the
older aircraft with fabric instead of metal are considerably smaller
RCS.


A Cessna in the head on aspect may indeed have an RCS as small
as 1 m2 , this is around the same as an F-16 !


After you have done that calculation, decide how near you would like
to live to that particular radar.

ATC radars generally only see either very large targets, or very
cooperative targets (transponders).

Wrong, ATC radars track light aircraft every day.
Only at short range.


Take a look at the free space coverage diagram for the
Raytheon ASR-23SS surveilance radar at

http://www.raytheon.com/products/asr...docs/asr23.pdf
And how may cars have you owned that have actually achieved the fuel
economy advertised?

You'll find that this civil aradt ssytem is quite capable of detecting
a 2 sq m target at 10,000 ft at 40 nautical miles
Which means 1 m^2 target at 28 nm...

Range isnt the problem, height is, if the aircraft is down in the
weeds you will indeed be limited to 20 miles or less

Thats why we have AWACS

Keith

Keith


Hell the radars of WW2 had no problem tracking aircraft of the
same size, its for damm sure that modern radars are better
My father assures me that was not the case, and he WAS the Radar
officer on a US Carrier in WW II. I'll take his word on that subject
over yours anytime


Yet 1930's era radar could detect an Me-109 over France from
the UK, the Me-109 has a wingspan roughly the same as a Cessna
at 32 ft
You are missing a very suble, but very important point that is
involved in your argument, and the Chain home argument. Microwave
radars are a relatively late development in WWII.


The US Army SCR-270 could detect aircraft at around 120 miles
out. One such set detected the Pearl Harbor raid 30 minutes before the
attack.

Neither Chain home, or Ship, or airborne radars or the SCR-270 were
microwave radars by any stretch of the imagination for most of WWII.
VHF RADARS relied on much more 'interesting' effects to work.


With a Microwave radar, the whole game is RCS, with a VHF radar
(typically 40-70Mhz), if you have to depend upon RCS you are blind.
VHF radar relies on picking a wavelength that produced a resonance
with one or more parts of the airframe, turning them into very
efficient re-radiators, making them appear many many times larger then
the real RCS.

Later in WWII, as Microwave radars became available, chaff was
dispensed as 1/4 wave aluminum foil. It produces such strong
reflections that it blinded the radar. It drove the AGC to the point
where the radar couldn't see anything that wasn't the chaff. The point
is the resonance caused the chaff to appear to have much much larger
RCS then it really had, just as various parts of the airframe did for
VHF radar.



Such technology was often used in towed reflector arrays, where a
few such tuned reflectors towed behind a frigate gave it the radar
signature of an Aircraft carrier! So while you could pick a frequency
that might be able to see a Cessna single well, it would be almost
blind to anything that didn't have similar size, or odd multiple sizes
of the airframe feature being used.

A TBD or a Betty could be seen at about 100 miles, but they are a
whole lot bigger than a Cessna 172


A Cessna Skylane has a wingspan of 35 ft, a TBD had a wingspan of
50ft and an Aichi Val a wingspan of 47.1 ft
Perhaps, but the wing probaly isn't the feature they were relying on.
For a VHF radar you need something that is an odd multiple of 1/4 wave
for it to work well. AT 40Mhz, that is roughly 1.9, 5.7, or 9.5 meters

The Radar in an F16 in Air to Air mode has a 50% probability of
detecting a 1 m^2 RCS at 40km..


We arent talking about an F-16 radar, we are talking about the
more capable search radars at ground stations.
I think you'd be surprised at just HOW incompetent many search radars
are. Have you ever used one.

I've operated both a Raytheon and a Siemens search radars. The Siemens
was part of a NATO installation, it was 120Kw, and we were about 60nm
from CPH. It had trouble seeing anything smaller than a D9 at that
range, and the doppler speed information at that range wasn't real
good, +/- about 80kt...

Here's the Aero-News Propwash story about the lightplane intercepted
by a jet fighter. Note the flares.

************************************************** *

It's the kind of trip
that you could almost make in your sleep. Maitland "Sam" Wirig
finished painting his house near Sequim (WA) last week, jumped in
his Cessna 172, and headed for his other house in Kent (WA). He
pointed the nose southeast and probably spent some time trying to
clear the smell of paint from his nostrils.

Imagine Sam's surprise, then, when he looked off the wing and
saw that he was being paced by an F-15 configured for very slow
flight. "I saw this great big F-15 (fighter jet) sitting right off
my wing tip, about 50 yards away, going really slow," he said.
"I thought, 'My God, what the hell is the problem?'"

The problem was, Sam unknowingly busted one of those pop-up
Presidential TFRs. The Bremerton Sun reports he had no idea
President Bush was visiting Seattle Friday. He took off from a
private, uncontrolled airstrip in Sequim and apparently didn't
check the NOTAMs (if, in fact, reasonable notice was even
available...). As you know, aircraft are generally banned from
within 10 miles of the president. From 10 to 30 miles out, aircraft
must have special permission.

Wirig says the F-15
pilot, with whom he was not in radio contact, kept lowering his
landing gear and flaps, trying to get the GA pilot to understand.
"I couldn't figure out what he was trying to get me to do," said
the 69-year-old pilot.

"All you can do is look at them and try to figure out what
they're trying to say. I know I was probably not where I was
supposed to be, but I didn't know why."

Then the F-15 fired three flares. Hmmmm, this might be
important. "That really got my attention," Wirig said. "About that
time I decided that Bremerton (National Airport) was a good option.
I figured the next flare might be a Sidewinder (missile)."

Wirig landed at Bremerton National Airport near Gorst (WA). The
F-15 circled overhead until the fighter pilot was certain the 172
had landed. On the ground, deputies from the Kitsap County (WA)
Sheriff's Department were on hand to give Sam a special
greeting.

"It was the first time I've done a traffic stop on an airplane,"
said Deputy Krista McDonald.

After the president left Seattle at 3:15 p.m. local time, Sam
was free to go. "I'm not too proud of it," Wirig, who's been flying
since 1969, said of the experience.

"I'll wait until it all blows over and if I don't hear from the
Secret Service or FAA, then I'll feel better. It was just a lack of
knowledge. I didn't know (Bush) was here."

"I didn't get shot down. That's the good news."

Indeed...
FMI: www.faa.gov

For the WHOLE story, go to
http://www.aero-news.net/news/genav....44f5&Dynamic=1
all the best -- Dan Ford
email: www.danford.net/letters.htm#9

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

On Mon, 1 Sep 2003 22:05:25 +1000, "Peter and Susan"
wrote:

I have been waiting for someone to mention the drug runner intercepted or
chased by the RAAF C130 [?] up around Darwin many years ago. Something about
relative speeds and the C130 having to slow down enough?

I thought about it, but then, it was unarmed...


....

cheers,

Paul Saccani,
Perth,
Western Australia


old turkish proverb: 'He who tells the truth gets chased out of nine villages'

"matt weber" wrote in message
news
On Mon, 1 Sep 2003 11:51:53 +0100, "Keith Willshaw"
wrote:

Me-109 has a wingspan roughly the same as a Cessna
at 32 ft
You are missing a very suble, but very important point that is
involved in your argument, and the Chain home argument. Microwave
radars are a relatively late development in WWII.


The US Army SCR-270 could detect aircraft at around 120 miles
out. One such set detected the Pearl Harbor raid 30 minutes before the
attack.

Neither Chain home, or Ship, or airborne radars or the SCR-270 were
microwave radars by any stretch of the imagination for most of WWII.
VHF RADARS relied on much more 'interesting' effects to work.


Quite so


With a Microwave radar, the whole game is RCS, with a VHF radar
(typically 40-70Mhz), if you have to depend upon RCS you are blind.
VHF radar relies on picking a wavelength that produced a resonance
with one or more parts of the airframe, turning them into very
efficient re-radiators, making them appear many many times larger then
the real RCS.

Later in WWII, as Microwave radars became available, chaff was
dispensed as 1/4 wave aluminum foil. It produces such strong
reflections that it blinded the radar. It drove the AGC to the point
where the radar couldn't see anything that wasn't the chaff. The point
is the resonance caused the chaff to appear to have much much larger
RCS then it really had, just as various parts of the airframe did for
VHF radar.



Incorrect

The British used strips of aluminium foil 30cm long by
1.5 cm wide , codename window , to blind the German
radar which was assuredly NOT on microwave frequencies
since they lacked the cavity magnetron


Such technology was often used in towed reflector arrays, where a
few such tuned reflectors towed behind a frigate gave it the radar
signature of an Aircraft carrier! So while you could pick a frequency
that might be able to see a Cessna single well, it would be almost
blind to anything that didn't have similar size, or odd multiple sizes
of the airframe feature being used.

A TBD or a Betty could be seen at about 100 miles, but they are a
whole lot bigger than a Cessna 172


A Cessna Skylane has a wingspan of 35 ft, a TBD had a wingspan of
50ft and an Aichi Val a wingspan of 47.1 ft
Perhaps, but the wing probaly isn't the feature they were relying on.
For a VHF radar you need something that is an odd multiple of 1/4 wave
for it to work well. AT 40Mhz, that is roughly 1.9, 5.7, or 9.5 meters

Guess what 9.7 metres comes out as in feet


The Radar in an F16 in Air to Air mode has a 50% probability of
detecting a 1 m^2 RCS at 40km..


We arent talking about an F-16 radar, we are talking about the
more capable search radars at ground stations.
I think you'd be surprised at just HOW incompetent many search radars
are. Have you ever used one.


You seem to be forgetting that most aircraft radar see only a
narrow cone ahead of them.

I've operated both a Raytheon and a Siemens search radars. The Siemens
was part of a NATO installation, it was 120Kw, and we were about 60nm
from CPH. It had trouble seeing anything smaller than a D9 at that
range, and the doppler speed information at that range wasn't real
good, +/- about 80kt...

So now our range has gone from not seeing light aircraft
at all to 60nm

Keith

"matt weber" wrote in message
...

That rather depends on what the intent of the intercepting aircraft
is. The cubans had little problem shooting down a couple of Cessna's
in 1996 as I recall. They had been detected on both Cuban and US
radar systems.
And both had their transponders turned on... It is easy when the
transponder is turned on. It is a cooperating target.

In fact both they and the Cuban Migs were tracked on primary radar
as testified to by radar specialist Jeffrey Houlihan of the U.S. Customs
Agency
who as usual was on the lookout for drug smugglers at the time.

Keith

On Sun, 31 Aug 2003 02:29:16 GMT, "JB" wrote:


"smithxpj" wrote in message
.. .
Except that it was sitting ready at Amberley on alert!

And in the loop of threat analysis based on dedicated radar
surveillance of a specific intrusion zone established around the
meeting location.

They were a tad more prepared for something other than an event
resembling a routine ATC 'unauthorised penetration of controlled
airspace by a lightie' scenario.


I wonder how much damage the supersonic charge to the intercept point would
have caused?

JB


Err...yair, probably would get the local political and public hackles
up a bit I'd imagine.

I ballparked a dash of about 70 nautical miles at, say, 450 knots
giving a rough 10 minute transit. Add in the time for a 'hot-systems'
scramble departure from the ORP and it really gets down to how the
threat to the exclusion zone was managed. It's a fair bet that the
speeds and track of *anything* converging towards the zone that merely
had a whiff of looking like becoming a threat would have set the
wheels in motion.

In either case, Maroochy Tower would have been part of the events,
and anyone on the tower frequency would have been fully aware of
what was happening. Including me. I didn't hear a thing.

Don't you just hate it when people drag *facts* into a perfectly good
uninformed discussion?

all the best -- Dan Ford
email: www.danford.net/letters.htm#9

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

"matt weber" wrote in message
...

That rather depends on what the intent of the intercepting aircraft
is. The cubans had little problem shooting down a couple of Cessna's
in 1996 as I recall. They had been detected on both Cuban and US
radar systems.
And both had their transponders turned on... It is easy when the
transponder is turned on. It is a cooperating target.

You do realise that Secondary Surveillance Radar and Primary Radar are
different things right?

A transponder will not make your primary return show up one little bit
brighter. The SSR image at the time I
was in SY was literally superimposed on the same display as the primary
radar, but came
from a different antenna/rx combination. The SSR antenna was visible as
a long narrow rectangle
underneath (or on top of, can't remember now) the primary radar dish.
Newer systems probably
combine the two, but you can have a primary target without the secondary
and vice versa and/or
both together.

BTW, I can assure you from personal observation that single engine all
metal lighties
painted very well on both the Terminal Area and Route Surveillance
Radars at
Sydney KSA in the 80's. The SSR target (when they were squawking) was
obviously
visible a lot further out/lower down than the primary target, but to
suggest they are too
small to show up is simply not so.

The CO
(Ex CAA)

On Tue, 2 Sep 2003 07:47:46 +0100, "Keith Willshaw"
wrote:


"matt weber" wrote in message
news
On Mon, 1 Sep 2003 11:51:53 +0100, "Keith Willshaw"
wrote:

Me-109 has a wingspan roughly the same as a Cessna
at 32 ft
You are missing a very suble, but very important point that is
involved in your argument, and the Chain home argument. Microwave
radars are a relatively late development in WWII.


The US Army SCR-270 could detect aircraft at around 120 miles
out. One such set detected the Pearl Harbor raid 30 minutes before the
attack.

Neither Chain home, or Ship, or airborne radars or the SCR-270 were
microwave radars by any stretch of the imagination for most of WWII.
VHF RADARS relied on much more 'interesting' effects to work.


Quite so


With a Microwave radar, the whole game is RCS, with a VHF radar
(typically 40-70Mhz), if you have to depend upon RCS you are blind.
VHF radar relies on picking a wavelength that produced a resonance
with one or more parts of the airframe, turning them into very
efficient re-radiators, making them appear many many times larger then
the real RCS.

Later in WWII, as Microwave radars became available, chaff was
dispensed as 1/4 wave aluminum foil. It produces such strong
reflections that it blinded the radar. It drove the AGC to the point
where the radar couldn't see anything that wasn't the chaff. The point
is the resonance caused the chaff to appear to have much much larger
RCS then it really had, just as various parts of the airframe did for
VHF radar.



Incorrect

The British used strips of aluminium foil 30cm long by
1.5 cm wide , codename window , to blind the German
radar which was assuredly NOT on microwave frequencies
since they lacked the cavity magnetron
You do not need a cavity magentron to product microwaves, it is a lot
easier to do that way, but I suggest you do some homework on something
called a ring oscillator. It can get you to about 1Ghz, and in fact
that is how a lot of early Microwave radars were operated.

30cm would be a 250Mhz Radar, not microwave, but UHF. It is enough
shorter then VHF radar to behave like a microwave radar.

Such technology was often used in towed reflector arrays, where a
few such tuned reflectors towed behind a frigate gave it the radar
signature of an Aircraft carrier! So while you could pick a frequency
that might be able to see a Cessna single well, it would be almost
blind to anything that didn't have similar size, or odd multiple sizes
of the airframe feature being used.

A TBD or a Betty could be seen at about 100 miles, but they are a
whole lot bigger than a Cessna 172


A Cessna Skylane has a wingspan of 35 ft, a TBD had a wingspan of
50ft and an Aichi Val a wingspan of 47.1 ft
Perhaps, but the wing probaly isn't the feature they were relying on.
For a VHF radar you need something that is an odd multiple of 1/4 wave
for it to work well. AT 40Mhz, that is roughly 1.9, 5.7, or 9.5 meters

Guess what 9.7 metres comes out as in feet
Unless the wing is a single conducting piece, not useful. A good DC
connection is often a poor radio frequency connection. Really needs
to be a single piece, or welded togther to be useful. The connection
between the pieces is a huge impedance discontinuity usually, so it
won't resonate.


The Radar in an F16 in Air to Air mode has a 50% probability of
detecting a 1 m^2 RCS at 40km..


We arent talking about an F-16 radar, we are talking about the
more capable search radars at ground stations.
I think you'd be surprised at just HOW incompetent many search radars
are. Have you ever used one.


You seem to be forgetting that most aircraft radar see only a
narrow cone ahead of them.
Which is why they are either mechanically or electronically steered,
the result is most actually see a pretty good sized chunk of sky in
front of them unless they have locked onto a target (in which case
they stop scanning).

I've operated both a Raytheon and a Siemens search radars. The Siemens
was part of a NATO installation, it was 120Kw, and we were about 60nm
from CPH. It had trouble seeing anything smaller than a D9 at that
range, and the doppler speed information at that range wasn't real
good, +/- about 80kt...

So now our range has gone from not seeing light aircraft
at all to 60nm
A D9 has more than 10 times the RCS of a Cessna. That means the
120kw Radar would have trouble seeing a cessna at 20nm. 120Kw radar is
not something I'd advise standing in front of. It isn't BMEWS class,
but it isn't anything to mess with either.

Keith