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What happened to the missing plane's transponder?

As the search continues for the missing Malaysian Airlines flight, a key unanswered question is what happened to the Boeing 777's transponder.

Transponders emit electronic signals containing information that shows up on air traffic controllers' screens. The information includes the plane's unique identifying code and its direction, speed and altitude.

Transponder signals are used by air traffic controllers to keep track of flights and are also employed in collision-avoidance systems.

In the case of the Malaysian jetliner, the transponder stopped about an hour after takeoff, when the plane was above the Gulf of Thailand between Malaysia and southern Vietnam.

Transponders can be shut off simply by turning a knob, said Capt. Ross Aimer, CEO of Aero Consulting Experts and a retired United pilot who also was a 777 instructor for Boeing.

Under normal conditions, Aimer said, a pilot would have no reason to turn off the transponder. But he said there are rare occasions when a pilot might have to - say, if the crew noticed smoke coming from the device and feared an electrical fire would break out.

Aimer said the 777 has two transponders, one of them a backup. If one goes out, the other comes on automatically. He said both can be shut off by turning a single knob on a small box, about 2 inches by 5 inches in size, in the cockpit panel.

Shutting off the transponder does not mean radar contact is lost, but the unique identifier and other information would no longer show up on a controller's screen.

"The misnomer is if you turn off the transponder you turn off everything. That's not true. You still have a blip on the radar screen that comes from ground-based radar. You can never turn that off," Aimer said.

The jet would continue to show up on a radar screen if the aircraft were within range of a radar station, a distance that can extend several hundred miles, depending on the terrain and the plane's altitude, said Brent Spencer, air traffic control program director at Embry-Riddle Aeronautical University's Prescott, Ariz., campus.

"It's possible to track an aircraft without a transponder with just raw radar, but it's much more difficult," Spencer said.

And if an airplane flew too low to be picked up by radar, controllers wouldn't have any information about the flight, Spencer added.

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colg10 March 14 2014 at 8:23 PM

Hope springs eternal. I really hope it was a skyjacking and the 287 passangers will be safe.

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bsinghj March 15 2014 at 8:21 AM

this seems to be a trial by the terrorists, to do similiar acts in future. more vigilance and watch will
be required. when one rides a plane, anything can happen till the plane lands back safely.
it i an alarm for what may be coming in future.

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abcstarfox March 14 2014 at 7:58 PM

Do I still think this plane was hijacked???

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1 reply
jrc11340 abcstarfox March 14 2014 at 9:34 PM

they could have reached Iran or Pakistan.The plane has a range of 7,000 miles, and this just in a flight simulator found in a house of someone on flight. Possibly a pilots house. How better to train others to fly and highjack an aircraft?

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Josey March 15 2014 at 11:36 AM

Finally, someone has said something that makes sense. And, if they can't "see" the aircraft, they have to idea which way it is heading. At the end of the day, all these people who are saying all these things, don't have a clue which way that aircraft was going and where it is. If it ended up in the sea, the black box would be emitting a signal. Fox, CNN, etc., needs to get all those clowns off the air, replace them with experienced pilots with 777 experience and stop all the BS. Also, keep in mind that Delta flys 777's each and every week from NYC to Dubai. 16 hours. One way. Non-stop. Last thing, would someone please tell me the actual fuel payload on the aircraft when it departed. Why hasn't the flight manifest been made public? It would show the total amount of fuel, in pounds, that was onboard (for a short flight).

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teezeeone March 14 2014 at 9:51 PM

I think if the plane did not crash, it may have landed in a terrorist group's camp. The reason for taking the plane, could be to find out how to use the planes to achieve their funding -where to put the bomb and how to detonate without raising suspicion.
There just is something disturbing about the whole thing.

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2 replies
eeodjo teezeeone March 14 2014 at 10:43 PM

Funny that you would say something disturbing about the whole thing. Teezeeone, this is so disturbing that the news about the possible takeover of Crimea and perhaps Ukraine, by Russia, or maybe a possible WWIII is almost forgotten. The past week has been nothing but the mystery disappearance of Malaysia MH370 and still being diagnosed diagrammatically. Right now, the authorities are going through a whole lot of process of eliminations. I hope they hit the right button on their next try.

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1 reply
bmwrjw eeodjo March 15 2014 at 11:29 AM

So very true. A plane is missing with about 250 people on it. Russia is poised to start WW3, something that will negatively impact everyone in the world. Here's a theory. Many maybe the Russians hijacked it knowing that everyone would focus on the plane and forget that they are once again on the march to human domination.

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Gracie GirL teezeeone March 14 2014 at 10:50 PM

I agree with you. It is very, very disturbing and full of suspense! very unsettleing.

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mafazyt March 15 2014 at 8:40 AM

If we know that the plane was hijacked and is actually on land, we would not reveal this in order to stage a surprise rescue. I'm hoping this is the case.

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2 replies
chatrbox9c mafazyt March 15 2014 at 8:56 AM

My thoughts ,someone knew where the radar would be weak,knew when to turn off both transponders,fly 50 ft off the deck, and landed this plane on a abandon strip,either a old military strip or drug smuggling strip.The plane is covered in camouflage and hopefully the passengers and crew are alive.Was the plane beyond the point of no return?(ref. Point BINGO)If so,why would they start to turn around.No,this smells Perhaps
a shallow landing along a coast 25,35 ft of water would submerge a plane.

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2 replies
mafazyt chatrbox9c March 15 2014 at 9:26 AM

This was well planned, all intentions were sinister. They knew the plane and knew the expected reactions of Malaysia and the world and were prepared. Jihad is their obsession, not ours, so they knew where to go and how to do it. But, all the different water searches have seemed almost deliberately wrong/confusing. I think if USA suspects a dry landing somewhere then they know it is a mega plan by terrorists and are not going to release that info in order to plan a counter attack/rescue. Hope its a rescue.

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leoganz chatrbox9c March 15 2014 at 9:36 AM

a 777 needs a mile and a half to stop...jungle air strips are never that long

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HIEP HOI NAILS mafazyt March 15 2014 at 9:53 AM

The terrorists are smarter than us this time ! So don't even think to rescue . I think after we capture and killed Osama Bin Laden , they learn a lot of experience with Navy Seals to prevent another attempt .

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ae12wrangell March 14 2014 at 10:44 PM

Is it possible that 370 actually made it to it's destination but the transponder etc., was turned off? Not everything in China is Kosher. I think it was sabotage, and it all started at Kuala Lampur International Airport. Whatever the team was that cleaned up the plane, before-hand, and made everything nice and neat - kicked the tires, refuel, remove the trash, etc, somebody had to be playing in the cockpit, or with something else in the section below, where the luggage is kept. There's a lot of tricky wiring that can disable a plane while in the air. In fact, despite the cold* weather, somebody could have stowed away, then at point X cut this wire, so the plane diverts right, or something.

*How cold is it? At 35,000 ft, about -70.

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1 reply
gailee5907 ae12wrangell March 14 2014 at 11:57 PM

or just blows up?BIG BIG BOMB

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1 reply
ae12wrangell gailee5907 March 15 2014 at 12:04 AM

A bomb? Not a chance. Even if it was over open water, the sound from the expllosion would have been so deafening that people on land, in various Asian countries would've heard it. THEN the 'search' parties would concentrate in that one section for debri and bodies.

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thomas stephen March 15 2014 at 7:36 AM

Most likely, the plane is at the bottom of the sea. A tragedy, but, the criminals wouldn't go through all this traveling to land the jet and save everyone, the islands are not fit for a jet liner to land, A true tragedy, , innocent people murdered by idiots.

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jebby1 March 15 2014 at 1:48 AM

When such loss of transponders happen, it's almost a given that the air traffic controller will alert the pilot and inquire about it. A loss transponder capability, regardless f the reason, can trigger a number of consequences. In some areas the aircraft may have to land or divert rather than continue to its intended destination. It could be that the pilot isn't aware of the failure. So it's expected that with a transponder loss or failure there would be at least a few sentences of conversation between the pilots and the air traffic controller. There's also the expectation that when aircraft are handed over (passed) from one controller to another, as the flight advances on it's route, there would be a change of transponder codes and a transponder "flash" or "ID" request by a controller on the initial contact with the gaining controller.

There seems to be a lot of very normal protocol that's missing from all the press reports. Like I can't imagine a loss transponder without the air traffic controller immediately alerting the aircraft about it, and the pilot immediately verifying or acknowledging.

Besides the mystery of what happened to the aircraft I'd add the mystery of the lack of information about what happened between takeoff and when someone decided that the plane was missing.

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1 reply
bmwrjw jebby1 March 15 2014 at 11:14 AM

Perhaps they are keeping the info quiet so they can do their jobs. They certainly do not need a bunch of know nothings like those of us on this site second guessing them. Anything anyone on this site has suggested has been considered and acted upon by the those in charge. What we know or think we know does not really matter.

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walterb611 March 15 2014 at 1:22 AM

Transponder turned off and plane flew below radar. No matter how you look at it you see foul play.
Question next what come next in this riddle

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