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  # 1011508 23-Mar-2014 21:25
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Technofreak: Fred99

The TCAS is part of the transponder system (which also provides the ADSB signal). Turning off or a failure of the transponder by default turns off the TCAS.

There is an ADSB blank spot in the area the last radar sinal was received so it wouldn't be seen on the likes of flight radar 24 in that area either.

Turnin

The power output from a transponder transmitter is very high, if there's a fault it needs to be able to be turned off from the cockpit.


Hmmm, granted they need to be able to turn stuff off and I guess there isn't much time to detail 'why' they need to turn it off in an adrenalin/emergency situation but I would have thought that if one or many critical systems were disabled, that info should make it to the ground via any means possible, even if its the last signal it sends prior to power down.




gzt

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  # 1011517 23-Mar-2014 22:13
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If the plane did a controlled landing in the ocean it is long sunk by now surely. Do the liferafts have emergency transmitters? What is the range of those? It's been a long time it seems like a lost cause in that regard.

The huge amount of information released lends itself to explanations of absolutely anything yet we know little of certainty about the reliability of much of the information.

 
 
 
 


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  # 1011530 23-Mar-2014 22:18
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gzt:\Do the liferafts have emergency transmitters? What is the range of those? It's been a long time it seems like a lost cause in that regard.


If they did, they would be the standard 406Mhz  emergency beacons.

They would have been picked up within minutes by sat systems.

Unfortently its very unlikley they are sitting in life rafts waiting to be rescued :(



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  # 1011540 23-Mar-2014 23:15
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Fred99: It's negative I know - but I don't think they're going to find the black boxes for this one.
I'm perplexed by reports of "possible" large pieces of wreckage.  That doesn't add up with either suicide by pilot, or an unpiloted plane running out of fuel at altitude.



I've been wondering what would happen after fuel exhaustion and the engines have stopped.  I don't know how the auto pilot is set up but the way I see it it could be one of these four options.

1. The autopilot maintains height till the aircraft stalls then the aircraft starts a high rate of descent and crashes into the sea like Air France AF 447.

2. The autopilot system is set up to prevent a stall and the aircraft descends in a controlled fashion and lands on/impacts the sea.

3. The autopilot disconnects and the aircraft descends in a similar fashion to what it would under the control of the autopilot and lands on/impacts the sea. Aircraft are designed to be naturally stable and provided they are correctly trimmed, they are capable of flying hands off or autopilot off for extended periods.

4. The autopilot disconnects and the aircraft starts to descend in an uncontrolled fashion and crashes into the sea.

The the scenarios 2 and 3 it is possible, but unlikely, the aircraft could "land" in the water and sustain "minimal damage and there might be some bigger parts.  Such that passengers might survive and be able to use the rescue slides/rafts.  However I doubt there was anyone alive when the aircraft went into the water, assuming it has.




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  # 1011543 23-Mar-2014 23:25
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Technofreak:
Fred99: It's negative I know - but I don't think they're going to find the black boxes for this one.
I'm perplexed by reports of "possible" large pieces of wreckage.  That doesn't add up with either suicide by pilot, or an unpiloted plane running out of fuel at altitude.



I've been wondering what would happen after fuel exhaustion and the engines have stopped.  I don't know how the auto pilot is set up but the way I see it it could be one of these four options.

1. The autopilot maintains height till the aircraft stalls then the aircraft starts a high rate of descent and crashes into the sea like Air France AF 447.

2. The autopilot system is set up to prevent a stall and the aircraft descends in a controlled fashion and lands on/impacts the sea.

3. The autopilot disconnects and the aircraft descends in a similar fashion to what it would under the control of the autopilot and lands on/impacts the sea. Aircraft are designed to be naturally stable and provided they are correctly trimmed, they are capable of flying hands off or autopilot off for extended periods.

4. The autopilot disconnects and the aircraft starts to descend in an uncontrolled fashion and crashes into the sea.

The the scenarios 2 and 3 it is possible, but unlikely, the aircraft could "land" in the water and sustain "minimal damage and there might be some bigger parts.  Such that passengers might survive and be able to use the rescue slides/rafts.  However I doubt there was anyone alive when the aircraft went into the water, assuming it has.


Without the engines running there would be no power(ok limited power due to a wind turbine that drops down and powers a few displays and a few hydraulics). There would be no chance that the autopilot would be active after this. So 1 and 2 are both out. Chances are that it would just continue gliding down but a lot of factors need to be factored in.





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  # 1011544 23-Mar-2014 23:29
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geocom:
Technofreak:
Fred99: It's negative I know - but I don't think they're going to find the black boxes for this one.
I'm perplexed by reports of "possible" large pieces of wreckage.  That doesn't add up with either suicide by pilot, or an unpiloted plane running out of fuel at altitude.



I've been wondering what would happen after fuel exhaustion and the engines have stopped.  I don't know how the auto pilot is set up but the way I see it it could be one of these four options.

1. The autopilot maintains height till the aircraft stalls then the aircraft starts a high rate of descent and crashes into the sea like Air France AF 447.

2. The autopilot system is set up to prevent a stall and the aircraft descends in a controlled fashion and lands on/impacts the sea.

3. The autopilot disconnects and the aircraft descends in a similar fashion to what it would under the control of the autopilot and lands on/impacts the sea. Aircraft are designed to be naturally stable and provided they are correctly trimmed, they are capable of flying hands off or autopilot off for extended periods.

4. The autopilot disconnects and the aircraft starts to descend in an uncontrolled fashion and crashes into the sea.

The the scenarios 2 and 3 it is possible, but unlikely, the aircraft could "land" in the water and sustain "minimal damage and there might be some bigger parts.  Such that passengers might survive and be able to use the rescue slides/rafts.  However I doubt there was anyone alive when the aircraft went into the water, assuming it has.


Without the engines running there would be no power(ok limited power due to a wind turbine that drops down and powers a few displays and a few hydraulics). There would be no chance that the autopilot would be active after this. So 1 and 2 are both out. Chances are that it would just continue gliding down but a lot of factors need to be factored in.



Are you sure?  There has to be at least one hour of battery power after generator failure.  Plus as you mentioned the RAT. I know there will be some load shedding to achieve this one hour time but does that include the autopilot?  Then if so, is the load shedding automatic or does it require crew intervention?




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  # 1011546 23-Mar-2014 23:40
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Technofreak: Are you sure?  There has to be at least one hour of battery power after generator failure.  Plus as you mentioned the RAT. I know there will be some load shedding to achieve this one hour time but does that include the autopilot?  Then if so, is the load shedding automatic or does it require crew intervention?


From Wikipedia


The aircraft has triple redundant hydraulicsystems with only one system required for landing.[152] A ram air turbine –a small retractable propeller which can provide emergency power– is also fitted in the wing root fairing.[153]


No mention of battery power




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  # 1011548 24-Mar-2014 00:07
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geocom:
Technofreak: Are you sure?  There has to be at least one hour of battery power after generator failure.  Plus as you mentioned the RAT. I know there will be some load shedding to achieve this one hour time but does that include the autopilot?  Then if so, is the load shedding automatic or does it require crew intervention?


From Wikipedia


The aircraft has triple redundant hydraulicsystems with only one system required for landing.[152] A ram air turbine –a small retractable propeller which can provide emergency power– is also fitted in the wing root fairing.[153]


No mention of battery power


I'm talking about certification requirements. You will probably need at look at the FAR's to find out what is specified, I wouldn't rely on Wikipedia.  The requirement is to have 30 minutes or 1 hour electrical power (the length of time differs according to aircraft certification standards, I'm pretty sure the 1 hour requirement applies to the likes of the 777)  backup following generator failure.  In a lot of aircraft this can only be done with a battery. It is possible that a RAT might be the way they comply in the 777.

Certain systems will be required by certification to be retained by the use of this emergency supply. Unless you have knowledge about what is is or isn't required and what equipment remains in operation how do you know the autopilot won't keep working?  Some aircraft are very difficult to hand fly at altitude and it is very possible the autopilot is a system that must be retained.  I don't know what is required for the 777, do you know?




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  # 1011550 24-Mar-2014 00:24
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I have watched numorus air crash investigations and they have done quite a few engine loss episodes and these never mention that there is any backup battery. Every time they show a episode where the engines have quit the rat drops down and they have limited controls without any grace period other than it complaining that your low on fuel.

The rat is lighter than battery's would be and less prone to failure and need to be replaced much less. So yes if this requirement exists it is likely Boeings way of complying with it.




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  # 1011552 24-Mar-2014 00:44
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Aircrash investigations.

Another form of reality TV. I wouldn't be basing any credible research solely on that sort of TV programme. Knowing more than just a little bit about flying I am sick of some of the stuff that gets dished by these programmes. Very often they do not convey the correct information.

I get a bit frustrated by people making sweeping statements that seem to be only based on guess work or suspect information.

Your guess that the autopilot stops working may be correct but as I suggested in my earlier post there is no way you can say that categorically, unless you know the 777's systems




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gzt

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  # 1011553 24-Mar-2014 00:57
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What is the range and nature of the black box locator beacon?

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  # 1011568 24-Mar-2014 07:27
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I am at the point where I do not expect it to be found. I expected once they find debris, they can backtrack based on winds and currents, how each piece of debris would react to wind and/or current (light stuff, heavier stuff, submerged stuff), but now that I see that part of the ocean is a gyre, where flotsam floats around in a huge revolving area, how can they possibly decipher where any debris came from?

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  # 1011619 24-Mar-2014 09:49
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gzt: What is the range and nature of the black box locator beacon?


AFAIK, they are ultrasonic transducer "pingers" with a range of only about a mile or so.  However, reading about the Air France crash, though they didn't locate the boxes via the pingers initially, I think I read mention that the French may have picked something up from analysis of recordings later.
While this seems woefully inadequate (in the case on the Air France flight and now this MH370), it wouldn't be a trivial exercise to design a self-powered locator beacon that can withstand the likely impact forces and water pressures, and to continue to operate for weeks.


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  # 1011631 24-Mar-2014 10:25
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I haven't had time to read the article properly but here's some details on detecting the Black (usually orange) box.

http://www.hydro-international.com/issues/articles/id1130-Deepwater_Black_Box_Retrieval.html




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  # 1011655 24-Mar-2014 11:02
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Technofreak: I haven't had time to read the article properly but here's some details on detecting the Black (usually orange) box.

http://www.hydro-international.com/issues/articles/id1130-Deepwater_Black_Box_Retrieval.html


There you go - one simple (?) suggestion in that article to improve detection range and battery life.  Use a (higher power) acoustic transponder which only "pings" when it hears a signal, rather than using up all it's battery power sending weaker continuous signals when nobody is listening.

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