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.

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.

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.

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.


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

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

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