ATC operates on secondary radar (transponder data). If there is no transponder, it would not appear on their scope. Some facilities have an option to switch to primary radar, but it is not usually monitored.
Most civilian ATC radars are 'Secondary' radars which depend on cooperative transponders on all aircraft. If you turn your transponder off, the system doesn't work.
US ATC uses 'Primary' radars as backup for locating aircraft that don't have transponders or don't have them on. Militaries use Primary radars for most of their activities. Other articles don't provide distinction on what type of radar was used.
ATC radar regularly loses small planes on 'primary' radar (primary radar being pure radar), and has to rely on the transponder. There are many areas where you simply don't have primary coverage, especially close to the ground. I've flown through military controlled airspace where they lose radar contact with me in a Cessna less than 10 miles from the base.
No you wouldn't have to "fake" the primary radar return.
Civilian Air Traffic Controllers in the US, Australia and numerous other countries only have Secondary Radar.
It used to be the running joke when I learnt to fly.
"How is a Cessna 150 like a Stealth Fighter?"
"With the transponder turned off.. neither will show on secondary radar"
The US Air Force, NORAD and NATO still maintain primary Air Defense radar. Especially in the US, a business jet or airliner without a functioning and active transponder is likely to get intercepted by a F-16 and escorted to land at the nearest suitable airport.
Primary radar is bad at determining speed, especially when the aircraft is not flying directly towards or away from it and even more difficult with a reduced radar signature.
(ATC relies on secondary radar - that is, transponders)
Primary radar[1] is only mostly used in larger airports or military installations. Secondary radar like ADS-B[2] has become really popular and requires the transponder on the plane to be on and working. If you switch that off, for a lot of people you do disappear.
In the case of the radar transponder there is the very prosaic reason that ATC doesn't want their screen filled with all the aircraft sitting at gates.
They can via primary radar, but the default displays secondary radar information (the transponder interrogation) as it tends to be significantly more precise. Surveillance radar has very coarse altitude resolution.
No, literally by the radar... I'm confused what you mean. Surely it's not news to a pilot that ATC facilities save radar data. For how long is a different question.
Regarding posts about spoofing and maintaining radar, it was my understanding that the radar sets that most ATCs used was not actually powerful enough to get direct returns from commercial aircraft, and relied on amplifying transponders to be able to see them. Supposedly only militaries operate radars powerful enough to see aircraft directly. Can anyone who knows more confirm or deny? If that's true, I guess we're already in a world were ATC info could be spoofed.
> It's secondary radar so it only sees planes with a transponder, but that's usually all of them.
In particular we're talking here about aeroplanes on an approach to a major airport (if they aren't on approach then by definition they aren't choosing between ILS and a visual clearance, and if it isn't a major airport why are we trying to bunch them up more?).
All US major airports have a "Mode C veil" which means there's a regulation requiring aircraft near those airports to have transponders ("Mode C" is a transponder mode in which the aircraft reports its own assessment of its altitude based on air pressure as well as a four octal identifier).
You don't need a transponder to show up on radar, it just makes it a lot easier.
Radar operators have a hard job telling a plane from clouds or echos. A transponder makes that job a lot, lot easier.
However, if you have a good radar system, you can happily track the contact without a transponder. In fact this happens all the time, I had a very nice chap at Farnbourgh West LARS (Low Altitude Radar Service) do this for me, when the shed I was flying had a little bit of a failure. For newewer systems such as those used by NATS automatically keeps the data assigned with the trace, using their proprietary algos to filter the noise.
If this happened over the UK, the transponder went off, ATC couldn't reach them, then a couple of Typhoons would be sent up to go have a look, and if need be escort.
With this background understanding of how modern Radar services are used piratically, taking into account a bit of background of the Malaysian authorities (short version: no terrorist attacks have ever happened even with our extremist religious views, honest.) Then this article will make some more sense:
http://www.theguardian.com/world/2014/mar/13/mh370-satellite...
It is becoming clear they knew full well what was going on. They had the ACARS data. They had contacts on their radar, which they would have understood to be the plane, if not at the time, soon after. (But they really should have understood at the time!).
This stuff happens all the time in air safety investigations. See Egypt Air, or Air France!
Three of the four aircraft hijacked as part of the 9/11 attacks had their transponders turned off:
> Controllers track airliners such as the four aircraft hijacked on 9/11 primarily by watching the data from a signal emitted by each aircraft's transponder equipment. Those four planes, like all aircraft traveling above 10,000 feet, were required to emit a unique transponder signal while in flight.
> On 9/11, the terrorists turned off the transponders on three of the four hijacked aircraft. With its transponder off, it is possible, though more difficult, to track an aircraft by its primary radar returns. But unlike transponder data, primary radar returns do not show the aircraft's identity and altitude. Controllers at centers rely so heavily on transponder signals that they usually do not display primary radar returns on their radar scopes. But they can change the configuration of their scopes so they can see primary radar returns. They did this on 9/11 when the transponder signals for three of the aircraft disappeared.
The article says it disappears from radar. When tracking aeroplanes there are two kinds of radar primary and secondary. Primary is actual radar, secondary isn't really radar at all but instead radio transmission of telemetry such as position, altitude, speed etc. This is equivalent to AIS, the system used to track boats that produced your image.
So we were tracking the plane but then the plane stopped transmitting tracking info for some reason (no idea if they even had it on primary radar). Someone could have turned it off or the plane could have crashed.
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