nanog mailing list archives
Re: Analysis from a JHU CS Prof
From: Owen DeLong <owen () delong sj ca us>
Date: Thu, 13 Sep 2001 16:28:03 -0700
Leigh Anne Chisholm wrote:
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.
That depends. The FAA has begun removing "Primary Target" service from some of it's control center, citing cost-savings, etc. Some ARTCC and TRACON facilities (Air Route Traffic Control Center and Terminal Radar Approach Control) have primary-target capabilities on their scopes, some do not. Some of the recording systems record the primary targets, some do not. As to the height at which you are undetectable, there are so many determining factors, that it's on a location by location basis. Factors include height of the antenna, terrain, distance from the antenna, number of radar sites covering the area (yes, there is an overlap in most of the US these days), etc. For example, I know bay can see me on the ground at PAO if I leave my transponder on. However, Oakland Center can't see me in some parts of Northern CA if I drop below 12,000 feet MSL (~4000 AGL in some of those areas).
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...
Yes and no. There was a time when this was so poorly publicized that many of my fellow pilots didn't know that there was a hijack code. The fact is, this has always been published in the AIM, so anyone who cared could easily pick up a copy of the AIM (Airmans Information Manual) at their local pilot shop and find out. I don't think the knowledge of the code necessarily prevents the pilot from using it. Any hijacker that's going to know about the code from any publicity it may have will already know enough to turn the transponder off anyway for other reasons.
-- Leigh Anne
Owen DeLong PP ASEL, Instrument Airplane
-----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 ProfAt 06:05 PM 9/12/2001, you wrote: Quite more interesting is why nobody noticed that 4 airliners wherehijackedalmost 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 ownproblemsto work) unless it impacted Center "B". Furthermore, unlesssomeone TELLSCenter they're being hijacked, there's no way for a controller -looking ata blip - to know what's up. And any controller can tell youthat 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
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Current thread:
- RE: Analysis from a JHU CS Prof, (continued)
- RE: Analysis from a JHU CS Prof Deepak Jain (Sep 13)
- Re: Analysis from a JHU CS Prof Joel Baker (Sep 13)
- RE: Analysis from a JHU CS Prof Deepak Jain (Sep 13)
- RE: Analysis from a JHU CS Prof Borchers, Mark (Sep 13)
- FW: Analysis from a JHU CS Prof Borger, Ben (Sep 13)
- RE: Analysis from a JHU CS Prof Leigh Anne Chisholm (Sep 13)
- Re: Analysis from a JHU CS Prof Jeff Mcadams (Sep 13)
- RE: Analysis from a JHU CS Prof Deepak Jain (Sep 13)
- Re: Analysis from a JHU CS Prof Joel Baker (Sep 13)
- RE: Analysis from a JHU CS Prof Matt Levine (Sep 13)
- RE: Analysis from a JHU CS Prof John Fraizer (Sep 13)
- RE: Analysis from a JHU CS Prof Leigh Anne Chisholm (Sep 13)
- Re: Analysis from a JHU CS Prof Owen DeLong (Sep 13)
- Re: FW: Analysis from a JHU CS Prof Majdi S. Abbas (Sep 13)
- RE: Analysis from a JHU CS Prof Matt Levine (Sep 13)
- RE: Analysis from a JHU CS Prof Mikael Abrahamsson (Sep 13)
- RE: Analysis from a JHU CS Prof Leigh Anne Chisholm (Sep 13)
- Re: Analysis from a JHU CS Prof Owen DeLong (Sep 13)