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
On Thu, 13 Sep 2001, Hire, Ejay wrote:
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.
If true, this is a weird practice. In Sweden, there are several civilian radars that are true radars with transponder receivers mounted on them as a compliment. Having served in the Swedish Airforce and actually having access to information provided by both civilian and military radars, my experience is that as long as you're flying fairly high (ie several thousand feet) even the civilian radars are going to see you fairly far away. Yes, your transponder is visable long before that, but if you turn it off you'll still be visable. We received information from both the transponder and actual civilian radar on our screens and most of the time the civilian traffic including small props were visable as both transponder position/hight and radar echo. What might be the case is that the true radar echo information is not relayed to the individual ATC because even the civilian high altitude radar gets cluttered by false echos. The military low-altitude costal radars are the ones really cluttered. Man, if it was like in the movies with a beep each time the radar swept an echo, all military radar officers would be deaf :) -- Mikael Abrahamsson email: swmike@swm.pp.se
I can't speak for the US, but in Canada we definitely have an abundance of "true radar" installations in most non-military control towers. I don't know the number of times I've heard tower indicating that they have an aircraft out in the practice area--keep an eye out. Altitude is unknown. That's just the standard advisory control tower's radar - and not the large area control centre radar. Canada has 7 area control centres for Canada and the Territories, and one "advisory" tower for each ATC centre at each airport. Edmonton for example, has two "advisory" towers - one for the Municipal airport, one for the International airport slightly to the south of the city. Ejay, you did make me wonder about your comments. I've sent off an Email to Nav Canada. If I get a response as to how the radar in Canada operates, I'll share it with you.
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Mikael Abrahamsson Sent: Thursday, September 13, 2001 3:56 PM To: nanog@merit.edu Subject: RE: Analysis from a JHU CS Prof
On Thu, 13 Sep 2001, Hire, Ejay wrote:
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.
If true, this is a weird practice. In Sweden, there are several civilian radars that are true radars with transponder receivers mounted on them as a compliment.
Having served in the Swedish Airforce and actually having access to information provided by both civilian and military radars, my experience is that as long as you're flying fairly high (ie several thousand feet) even the civilian radars are going to see you fairly far away. Yes, your transponder is visable long before that, but if you turn it off you'll still be visable. We received information from both the transponder and actual civilian radar on our screens and most of the time the civilian traffic including small props were visable as both transponder position/hight and radar echo.
What might be the case is that the true radar echo information is not relayed to the individual ATC because even the civilian high altitude radar gets cluttered by false echos.
The military low-altitude costal radars are the ones really cluttered. Man, if it was like in the movies with a beep each time the radar swept an echo, all military radar officers would be deaf :)
-- Mikael Abrahamsson email: swmike@swm.pp.se
This is long, and off topic. If you don't want to know about air traffic control, delete it now. Most ATC services are not provided by towers. Generally, the tower controls a 5 statute mile radius around some arbitrary point on the airfield (usually the middle) up to 2,500' AGL. Some towers have more airspace, some have less. (For example, Hayward tower has less altitude, and is cut short to the west and north by airspace controlled by Oakland tower and Bay Approach). Most towers don't have RADAR at all. Of the towers that do have radar, usually they receive a feed from the closest TRACON or ARTCC (see my previous message). The RADAR information presented to controllers in the TRACON and ARTCCs is the result of a computer compositing several different RADAR transcievers to produce a digital image presented to the controller. Among the things that can be presented to controllers on these displays are the following: Primary Target* Digital Map Data Fields*** Beacon Code Altitude**** Ground Speed Callsign***** Type***** Destination***** Vertical Change Status (Climb/Descent/Level)**** Heavy Marker(If heavy) ***** Secondary Target*** Weather** *Some facilities do not have Primary target capability. There is talk of decomissioning this altogether, although it has met with substantial opposition in the aviation community. **Only in the facilities with the oldest and newest equipment. The oldest equipment displays weather whether the controller wants to see it or not, and does a very poor job of it. This is the result of poor filtering technology in some of the oldest equipment still in use. This equipment will probably disapper within 5 years. The newest equipment has the capability to integrate information from the NexRAD weather radar sites onto the display. This is a significant improvement. ***Data fields only appear if the target has an active transponder operating. The same is true for secondary target. ****Altitude information only appears if the transponder is active in mode C or mode S (altitude encoding, or Data-Link modes). *****This information is only present if it has been entered by a controller with an ATC flight plan. This is done in order to assign a particular aircraft a unique beacon code for specific tracking. Here are what the terms above mean... Primary Target The depiction on the scope of the actual reflection of radio energy back from something some distance and bearing from the radar. Digital Map This is a terrain and aviation facility map that is encoded into the computer system. It includes things like landmass borders, intersections (aviation waypoints, not roads), navaids, airports, approach gates, etc. It is a depiction of the area to help the controller remain oriented to the traffic flows and guide aircraft to their destinations. Beacon Code The 4-digit octal number programmed into the targets transponder. Altitude The vertical distance between the aircraft and mean sea level. Ground Speed The speed of the aircraft over the ground. Callsign The flight number or tail number of the aircraft. Examples would be things like: UAL563 United 563 N1254M November 1254 Mike AAL952 American 952 Type The type of aircraft. Destination The intended destination of the aircraft Vertical Change Status Provides a blank for level, upwards pointing arrow for climb, or downwards arrow for descent. Represents any altitude change of 100 feet or more since last interrogation. Secondary Target The active reply to the radar interrogation of the transponder. This is generally represented as a single letter which is used to indicate which controller is talking to the specific aircraft at the particular time. Weather Radar can (generally) only measure liquid water in the air. As such, some forms of clouds and precipitation can be displayed on some facilities radar units. Sources: Tour of Palo Alto Tower (BRITE Radar equipped) Tour of San Francisco Tower (Equipped with multiple types of tower radar, including BRITE, SMGCS, etc.) Tour of Bay Approach (TRACON) Tour of Socal Approach (TRACON) Tour of Oakland Flight Service Station (AFSS) Tour of Oakland Center (ARTCC) Discussions with multiple working Air Traffic Controllers in towers, TRACONS, and ARTCCs. Airmans Information Manual ATC Handbook (7110.65J, 1997 edition) Hope that helps clarify things for everyone. If anyone wants to know more about how these components of the system interrelate, let me know off list. Owen "Hire, Ejay" wrote:
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
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participants (4)
-
Hire, Ejay -
Leigh Anne Chisholm -
Mikael Abrahamsson -
Owen DeLong