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Wreckage of MH370 washing up on Reunion Island?

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pickle9000:

--- Quote from: Psi on August 01, 2015, 02:13:22 am ---Does anyone know how long the black boxes can survive in salt water while still having some hope of recovering data?
Is it already too late, or could they recover some data after many years in the ocean?

Assuming they are intact and not ripped apart of course.

--- End quote ---

Air France May 2009 - May 2011 recovery of last black box, both survived. So 2 years is possible, I remember hearing that 3 years or earlier is desirable but not sure where I heard that or what it relates to.

One thing that has bugged me for a while is that reports say the transponder was turned off. They do not say lost contact. I expect that's a direct reading from the acars but would a loss of power generate the same message? It would also be interesting to know if shutting off the transponder is recommended or detailed on any of the onboard emergency checklists. This is the first event so you'd think it would be covered in more detail.

cimmo:

--- Quote from: pickle9000 on August 01, 2015, 02:54:01 am --- It would also be interesting to know if shutting off the transponder is recommended or detailed on any of the onboard emergency checklists.

--- End quote ---
Shutting it OFF (or standby)? No, not in flight. That switch is only deliberately used on the ground.
But the selection of an emergency code IS mandated in all checklists for serious events.
It is possible that during this code selection, the on-off switch was inadvertently operated, but personally I find that highly unlikely.

pickle9000:

--- Quote from: cimmo on August 01, 2015, 03:18:16 am ---
--- Quote from: pickle9000 on August 01, 2015, 02:54:01 am --- It would also be interesting to know if shutting off the transponder is recommended or detailed on any of the onboard emergency checklists.

--- End quote ---
Shutting it OFF (or standby)? No, not in flight. That switch is only deliberately used on the ground.
But the selection of an emergency code IS mandated in all checklists for serious events.
It is possible that during this code selection, the on-off switch was inadvertently operated, but personally I find that highly unlikely.

--- End quote ---

The term used is "shutting off the transponder" but that is in flight so does that mean putting it into standby? Would that generate a message? What I'm curious about is if there is one or more acars messages that say the standby switch was hit, power shut off, or simply a signal lost issue and the same message is used for all so the crew can be notified (or whatever action taken).

So I guess the followup would be that if the power was shut off, would that be shutting down other items as well and do they report over the acars?

I find news reports so watered down it's hard to know if the reporters have asked any relevant questions.

cimmo:

--- Quote from: pickle9000 on August 01, 2015, 03:30:25 am ---The term used is "shutting off the transponder" but that is in flight so does that mean putting it into standby?

--- End quote ---
From the perspective of the ATC secondary radars, either standby, off or some actual failure* would disable the active return of the radar signal (amplification and encoding) and the aircraft would basically disappear from the radar display (although if modern enough, the display probably indicates last known position with an error flag on it).

The particular radars in use by the ATC facilities in this incident only had a low power primary radar (a primary radar works by simple skin reflection) that had a range of about 40-60 miles. The location of the aircraft when the transponder return was lost was outside of that range. The high power primary military radars were able to track the aircraft (but without accurate altitude information), but this track information wasn't available to anyone with flight following responsibilites for that flight at the time.

*Failure is mitigated against by having at least two transponders on the aircraft.
And an actual "off" switch position is useful in flight as being a digital device, transponders sometimes stop working correctly. And like any similar device, the solution is to turn it off and on. In aviation speak - "Please recycle your transponder".


--- Quote from: pickle9000 on August 01, 2015, 03:30:25 am ---Would that generate a message? What I'm curious about is if there is one or more acars messages that say the standby switch was hit, power shut off, or simply a signal lost issue and the same message is used for all so the crew can be notified (or whatever action taken).

So I guess the followup would be that if the power was shut off, would that be shutting down other items as well and do they report over the acars?

I find news reports so watered down it's hard to know if the reporters have asked any relevant questions.

--- End quote ---
I cannot speak with any authority on the subject of ACARS system interaction with the transponder - I don't have that specific information. Perhaps there is a tie from the built in test equipment of a transponder to the ACARS system that would report a discrete failure of that unit, but there would be no need for the physical "off/standby" switch to be so coupled.

But the ACARS system was not working properly that day either - the last normal ACARS uplink happened prior to the loss of transponder returns, whether this was due to a deliberate act or some part of the wider system failure, that is not really known.

kosmonooit:
Assuming the one possibility of the ghost plane scenario (humans and some electronics knocked out for some reason just after the last comms), surely they should be able to model what happens to the aircraft when flying on autopilot and the fuel runs out, in terms of the type of impact with the water. So the flaperon survived the wing break up, surely there must be clues in there.

As has been shown with other accidents, you really have to have a lot of luck and skill to ditch successfully, more often that not its going to end with a break up of the aircraft. Its going to be smashes to tiny bits if it hits the water with terminal velocity.

At least something has been found! The rest must be out there, luckily we have the Aussies with deep pockets and lots of toys on the case.

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