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jdesbonnet
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Teardown video
jdesbonnet   3/22/2014 1:32:58 PM
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Mike Harrison has a really good teardown video of a Flight Data Recorder on his YouTube channel 

http://www.youtube.com/watch?v=mQehX0rVYuY

Other really great teardown videos there also... 

Andy_I
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Re: Command and Control
Andy_I   3/18/2014 2:51:59 PM
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"The only reason I can think of to stop transmitting data is if flying over hostile territory."

How about while it is on the ground, not flying anywhere?  Think a few hundred planes parked at a terminal or hangar, all transmitting, all the time.  That's why they have switches.

I doubt a COMMERCIAL airliner would turn off a transponder because of flying over hostile territory.  If the land you are over is so hostile, you wouldn't be flying over it.

 

Etmax
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Re: Command and Control
Etmax   3/18/2014 10:03:59 AM
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Yes but there is a big difference between tuyrning off the display (I understand your reasoning here) of the transponder and its signal to the outside world.

Etmax
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Re: Command and Control
Etmax   3/18/2014 10:01:32 AM
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Hi Janine, is it the flight data recorder or the beacon/telemetry radios that was turned off or maybe even the ID transponder? To my mind the ID transponder shouldn't be able to be switched off because that's what decides if you get blown out of the sky or not I would have thought. I think this incident as regrettable as it is may bring about some real changes in the way commercial airlines are instrumented. I'd like to see the GPS data sent to satellite on all comercial planes over 1-2 ton and without an on/off switch, ie. it should be on as soon as the plane leaves the ground. If that data were transmitted (ID, Lat, Long) every minute, it wouldn't break the bank and we wouldn't be wondering where that plane is.

The MicroMan
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Black Box
The MicroMan   3/17/2014 7:51:28 PM
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Turning off a transponder because somebody's screen is too cluttered with data would be just plain stupid.  You just filter what is displayed at the moment. 

I'm thinking we might prefer that a drone captured by the Soviets would somehow loose its memory so we could say "what drone? We've been looking for that wayward boy! Wow, what gas mileage!" rather than "see, here it burst out its photos back to DC..."

In a civi aircraft it might be good to have cockpit recordings (voice, position, data, system...) that can't be turned off, even by personnel - or loss of primary electricity.

These articles are pretty thin on info.  Even the ever-thorough CNN was showing ACARS transmitting every 30 minutes. Seems there was an old Black Box "teardown" at ESC (remember ESC?) five years ago (admittedly, it was a pretty old box).

I think what we need right now is that black box from "2001: A Space Odyssey" to beacon out where it is.

CTHP
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Re: Command and Control
CTHP   3/17/2014 7:08:24 PM
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As a standlone aircraft subsystem, wouldn't the FDR have a dedicated fuse on the flight engineers panel that would allow power to be cut in case of over-current, and secondarily to simply disable it? 

perl_geek
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CEO
Re: Command and Control
perl_geek   3/17/2014 3:52:02 PM
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The transponder signal takes up space on the ATC radar display. (A controller's screen has to show many miles in less that a metre.) If too many signals come from the same point (as far as the screen resolution is concerned), they  overlay and blur each other.

The transponder is switched from "standby" (warming up) at the runway threshold, just before takeoff, and back to standby, or off, after landing. 

Hossmann
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Re: Command and Control
Hossmann   3/17/2014 1:28:10 PM
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Its possible that the tower can request to turn off the Transp. and nobody else, if too many signals coming in. Both the pilot and tower can turn it on only. Also about the recoding box should go off and wake up on demand when request comes, so battery life is preserved.

Sanjib.A
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CEO
Re: Command and Control
Sanjib.A   3/17/2014 12:44:36 PM
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@perl_geek: "It is necessary for the crew to be able to switch transponders to a non-responsive mode, because otherwise the signals can overwhelm the system, (e.g. around airports)."

I was searching for an answer to the question why there is a provision kept for the crew to switch the transponder off. Thanks for the answer to that. A continuing question that occurs to my mind now: is the intention not to overcrowd controller's radar screen or not to "overload" the system with too many signals from all different flights?

perl_geek
User Rank
CEO
Re: Command and Control
perl_geek   3/17/2014 12:28:39 PM
NO RATINGS
You are basically correct.

The military designation of the transponder is IFF "Identification Friend or Foe". Depending on the level of sophistication, a transponder replies to a pulse from ATC's Secondary Surveillance Radar with a  4-digit  code, (Mode A, the basic level),  possibly altitude, (Mode C), and additional information, (Mode S). On request from ATC ("Squawk Ident"), the pilot can make the response pulse distinctive, for identification. Special codes are available to identify hijacking, communications failure, and Mayday situations, in case radio communication is impossible or difficult. 

It is necessary for the crew to be able to switch transponders to a non-responsive mode, because otherwise the signals can overwhelm the system, (e.g. around airports).

The FDR (Flight Data Recorder) records the data from the aircraft's systems and controls, while the CVR (Cockpit Voice Recorder) records the sounds in the cockpit for the last hour (I think). This provides a record of the crew interactions, (and sometimes vital clues as to explosions, decompressions, engine failures, and other events).  The crew have no control over these records.

 

 

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