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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 29th Oct 2014, 09:55
  #11581 (permalink)  
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Fuel Imbalance and cross feeds

See page 970 here: https://db.tt/4EXSNq5o for info on fuel imbalance and cross feeds.
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Old 29th Oct 2014, 10:12
  #11582 (permalink)  
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Can anyone with access to B777 manuals please find out the maximum fuel imbalance?
There's no quoted Limitation/"maximum" in the manuals (whilst gross imbalance obviously isn't desirable I suspect for certification purposes the aircraft would have to be controllable one wing tank full, the other wing tank empty (e.g.holed)).

Balancing, when called for, is performed as ALSM/the FCOM 2 describes.
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Old 29th Oct 2014, 14:53
  #11583 (permalink)  
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Originally Posted by slats11 View Post
I find it difficult to believe Inmarsat took days to discover they actually had this information. Or that it would take 4 days to deduce the plane kept flying for many hours after lost contact.
1. It was a weekend. Someone probably to had to go and look at the data in their time off, when the news reports already seemed sure it had crashed not long after takeoff, where it would be relatively easy to find.
2. The BBC documentary said their first thought was that someone was spoofing the system, pretending to be the aircraft. That probably involved pulling in experts from other companies to verify that it wasn't. Again, on a weekend.

So, you're probably already up to the 10th by the time everyone is available who needs to be available.
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Old 29th Oct 2014, 16:00
  #11584 (permalink)  
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Then don't forget getting authorization to release the data and getting the report that was being handed over double checked by lawyers that nothing was going out that would be detrimental to INMARSAT. Calculations and documentation re-checking amendment and reapproval by senior management after all hoops jumped through.

I know some companies where that would take a month.
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Old 10th Dec 2014, 00:08
  #11585 (permalink)  
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Is this number of transponders correct?

In the following article, regarding redundant systems, Byron Bailey said

"the 777 has 80 computers and three sets of nearly every system on board – including three radios, three radar transponders, three autopilots and three flight management computers – to ensure a "practically fail safe" operation.

A failure of one will result in transfer, usually automatically, to another. "

Here is what I am asking 777 pilots: Is it correct that there are three transponders?

Flight MH370: former Boeing 777 pilot points to sabotage | Flight MH370 News | The Week UK

Last edited by TamairTarmac; 10th Dec 2014 at 00:25. Reason: to focus the question
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Old 10th Dec 2014, 04:53
  #11586 (permalink)  
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There are actually 2 ATC Transponders; L & R switched by the crew. The general thrust of his statement is however correct in that most flight critical systems are triplicated and have auto switching.

If it's not triplicated; then in most cases it's duplicated. These systems are never on the same power supply.

As a separate example; a non essential system such as ACARS is a software function within the AIMS system. There are 2 AIMS systems and therefore ACARS; The system uses the VHF system it can tune to, one of three (VHF L, C or R), depending on the aircraft option/vintage it will the go for one of two HF systems (L or R) after that; then on to a single SATCOM connection if enabled and optioned. The pilot can select a source if so desired.

So what he's saying in a nutshell is that something IS fishy leading to the end of this aircraft.
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Old 10th Dec 2014, 05:05
  #11587 (permalink)  
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2 is 2 and 3 is 3

I have just seen him quoted all over the internet referring to three transponders; and I just wonder if it is only 2, that no one has called him on it. Or if there is some kind of third redundancy, want or where it might be. Or might he be referring to the Inmarsat pings as a kind of transponder?
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Old 11th Dec 2014, 02:25
  #11588 (permalink)  
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As somebody who knows nothing about this (or anything of a technical nature like this) i'm curious, how does the auto-switching work? That is, what is the technology that detects the need for a switch and switches it? To my lamen brain, it seems logical than in order for a switch to take place between two systems, they would have to be connected in some sort of way?

Apologies if this is really dumb question.
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Old 11th Dec 2014, 06:56
  #11589 (permalink)  
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You are correct that there is a link between systems for automatic switching to occur; this can either be via data bus links between computers or simply by relay connections.

Trying to keep it simple;

Depending on the system; computers on different power supplies will be connected through data buses, each computer comparing and monitoring against the computer in control to detect a failure and then force a transfer to a good computer.

Relays often provide discrete inputs to computers as to status of power and other circuits. A failure of power on a circuit can be the trigger to initiate the system on standby.
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Old 11th Dec 2014, 16:30
  #11590 (permalink)  
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I have just seen him quoted all over the internet referring to three transponders;
It doesn't matter anyway. The plane was no longer within radar coverage, so 1 transponder or 1 hundred, there is no transponder signal when outside radar coverage.
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Old 12th Dec 2014, 15:59
  #11591 (permalink)  
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Just a thought about this faux concern vis a vis 3 transponders. Uninformed complaints / criticisms seem to abound in the media these days.
1. The IFF/Transponder system doesn't need to be triple redundant, the way some of the flight safety systems mentioned above might need to.


The plane flies safely with 0, 1, or 2 operational.
If 0 are working, the crew need to use their radios more often in terms of coordinating with ATC on where they are and what they are doing, since the information isn't passed by the system via the radar and radar returns.

You can argue that if you wish to "for safety's sake" rely on a third layer of capability, that third layer is present in the ability to use two way radio communication:

You tell them where you are and what you are doing, just as we have always done in areas where there is no radar contact.

ATC then associates that with a radar reflection, rather than a transponder paint/code, and can thus track you and sequence you into the air traffic du jour. If you turn off your two transponders, and refuse to talk to them on the radio, it amounts to the same thing as turning off three transponders.

May we put to bed (without any supper!) this "three transponders" thing?

For any journalists reading (Mr Bailey?): please, give it a rest.
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Old 23rd Dec 2014, 16:50
  #11592 (permalink)  
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New Theory about MH370

Flight Magazine has just published a new theory on the location of the possible crash site of MH370. It looks very plausible, what do others think?

Is this where MH370 is?
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Old 23rd Dec 2014, 17:44
  #11593 (permalink)  
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He assumes a constant TAS and true track for the last two and a half hours of flight. If either of those varied, his final position calculation will be wrong.
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Old 23rd Dec 2014, 22:08
  #11594 (permalink)  
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R.E. Flight Magazine article

The proposed route is not all that different from routes that others have proposed. Great circle and true track routes at constant air velocity tend to end up at the Southern limit of the search area, around -37 to -40 deg latitude. Once again, however, only BTO data are considered in the detailed solution. Such tracks do not match the BFO data very well - the BFO data favor a lower velocity for the first hour after the final turn South and either an increase in velocity or some sort of curved path thereafter. Unfortunately we do not have as clear an understanding of the BFO error model as we do for the BTOs, so deciding whether a seemingly poor match to the BFOs is significant or not is still unclear.
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Old 20th Jan 2015, 05:33
  #11595 (permalink)  
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Situation 15 Jan 15


This is the official latest

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Old 20th Jan 2015, 06:36
  #11596 (permalink)  
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I'm really starting to think they will never find it.
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Old 20th Jan 2015, 06:52
  #11597 (permalink)  
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I find it difficult to understand how, after more than 10 months, not a single shred of wreckage has appeared on some coastline somewhere, or been sighted, floating.

The prevailing weather, wind, and currents drive debris from this area towards Western Australia, and up and along the West Australian coast.
One would think that either seat cushions, luggage, honeycomb panels, or one of a thousand items from an aircraft, that floats, would eventually be sighted or found on a beach or near the shoreline.

The fact that not a shred of anything from MH370 has ever been sighted or found only feeds the conspiracy theorists and the tinfoil hat brigade.
I find it hard to believe that a 777 would disappear into an ocean without a trace.
I know it's a big and lonely ocean, but sooner or later, some type of wreckage usually appears from an ocean disaster such as this.
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Old 20th Jan 2015, 11:46
  #11598 (permalink)  
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People do not understand how extremely large the world is. The West Australia coast is around the same as if there were a coastline from Galveston running all the way around to Seattle. The State is around as big as the USA West of a North South line running through Galveston to the Canadian border. The entire state has a population of around 2.5million which is a million less than the population of Los Angeles and most of that population is in Perth. The chances of wreckage being found by someone who remembers MH370 is extremely small. The coast is covered with flotsam and jetsam of all sorts. Only if a sizeable piece of aircraft turned up on a beach might anyone notice and that is a long shot.

If you wanted to lose an aircraft dropping it into the sea over a thousand miles West of Perth into unexplored areas of the South Indian Ocean would be the ideal choice.
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Old 20th Jan 2015, 12:02
  #11599 (permalink)  

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"The West Australia coast is around the same as if there were a coastline from Galveston running all the way around to Seattle"
Hi Ian,
With respect, the size of the coastline is exactly why it is surprising nothing has been found. It is a huge 'mitt' in which to catch debris.

Whilst I appreciate the coastline is long there are enough settlements, holiday marine traffic, GA and other populations that something should have been found.
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Old 20th Jan 2015, 23:21
  #11600 (permalink)  
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Update on Capt Simon Hardy's theory

There is an update on Capt Simon Hardy's theory:

Considerations for ditching MH370 - Learmount
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