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RE: Analysis from a JHU CS Prof
From: "Leigh Anne Chisholm" <lachisho () tnc com>
Date: Thu, 13 Sep 2001 15:11:15 -0600

I despise posting off-topic, but I want to say two things...

1.  If a transponder is turned off, it doesn't mean that you don't show up
on radar--a blip appears on the radar screen as long as you're high enough
to be detected.  If however you fly low enough, you can fly below the
radar's detection capability.  I don't offhand recall what height that
is--it's been years since I was active as a pilot and prospective Air
Traffic Controller.

2.  What's the point of having transponder codes for hijacking if they're so
well published everyone is aware of them?  The purpose of the codes was so
that the pilot could communicate this information without the hijacker
becoming aware of what was happening.  I have always REALLY DISLIKED the now
common practice of advertising this information.  You're taking away one of
the pilot's best tools...

  -- Leigh Anne

-----Original Message-----
From: owner-nanog () merit edu [mailto:owner-nanog () merit edu]On Behalf Of
Hire, Ejay
Sent: Thursday, September 13, 2001 2:35 PM
To: 'Borger, Ben'; 'nanog () merit edu'
Subject: RE: Analysis from a JHU CS Prof

The transponders, like most avionics, has a handy-dandy off switch.

-----Original Message-----
From: owner-nanog () merit edu [mailto:owner-nanog () merit edu]On Behalf Of
Borger, Ben
Sent: Thursday, September 13, 2001 2:32 PM
To: 'nanog () merit edu'
Subject: FW: Analysis from a JHU CS Prof

At 06:05 PM 9/12/2001, you wrote:

Quite more interesting is why nobody noticed that 4 airliners where
almost the same time.

Not surprising.  Aircraft are "flight followed" by a series of control
centers across the nation, each responsible for a given chunk of
airspace.  Something happening in an area controlled by Center "A", for
example, wouldn't be passed on to Center "B" (which has it's own
to work) unless it impacted Center "B".  Furthermore, unless
someone TELLS
Center they're being hijacked, there's no way for a controller -
looking at

a blip - to know what's up.  And any controller can tell you
that pilots do

Somehow the people who did this managed to turn off the transponders on
these planes.  Normally a plane flying in controlled airspace squawks a
unique id and altitude which is decoded by their radar and associated with
each blip.  Sometimes low cost homebuilts/ultralights fly with no
transponder, but Boeings <sarcasm>usually</sarcasm> do.  If you set a
transponder to XXXXX, it means you're being hijacked.

BTW if you see your friend Jack at the airport, be sure to say,
"What's up,
Jack!" instead of "Hi Jack!"

So how do you deal with this?  Blowing up a whole country?  I
wonder if the
US should adopt a 'fire w/ fire' approach and invest in
intelligence, covert
ops and assassinations.  It would seem that it is open season on terrorism
by every democratic nation, I expect to see very conspicuous
Samuel Jackson
style ass whoopins on whiny extremist groups to satiate America's anger.
Terrorize the terrorists.

Oh yeah, obviously Echelon should probably have MacOS loaded on it.


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