Most ATC towers do not have true radar. I.e. the ability to detect flying objects above altitude x by bouncing radio waves off of the object and computing the time vs. Doppler shift vs. inclination to determine altitude/heading/speed. In modern (non-military) atc systems, this info is relayed by the transponder to atc. Source: "How to become a Pilot" Bantnam Press. -----Original Message----- From: Leigh Anne Chisholm [mailto:lachisho@tnc.com] Sent: Thursday, September 13, 2001 5:11 PM To: Borger, Ben; nanog@merit.edu; Hire, Ejay Subject: RE: Analysis from a JHU CS Prof 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 hijacked 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 problems 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.
-b