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Lottie

Airliner Crash Lands at Heathrow Airport

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BTW due to the landing patterns at Heathrow had this loss of power happened a few minutes earlier it would have been coming down in central London.

Or if the wind would have been different: Windsor castle.

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Space Commander Travis
Or if the wind would have been different: Windsor castle.

ahh.... *taps nose*

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ships-cat
ahh.... *taps nose*

<sigh>.. .a royal conspiracy ? ... *picks nose*.

Meow Purr.

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1.618

Machinery fails, planes crash.

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keithisco
Engines don't fail simultaneously due to fuel contamination, there can be hours of difference between failures.

Been checking around if someone I know has a maintenance manual for the triple 7 (I know, for $300 you can buy one... but I don't really need it). If it all happened due to power loss that means that there is a solenoid in the fuel supply line that only stays open while powered, which if you ask me is a engineering short come to start with, once started a turbine does not need any electricity to keep functioning (at least for a while).

But it is really mystifying...

Nah! You're right Q, just thinking out loud :tu: Howabout ctatstrophic loss of both hydraulic systems stopping the fuel pumps, then again, they also wok on gravity feed as well.....really running out of ideas, brain hurts ^_^

Hey look!! it's my 727 th post, is that kinda spooky :blink:

Edited by keithisco

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Moon Monkey

Hmm a new theorey is coming out about crossed lines and cell phones interfering, not sure how likely it is though or whether it could be done on purpose:

http://www.thesun.co.uk/sol/homepage/news/article711639.ece

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Space Commander Travis

The Sun does tend to be more interested in the dramatic than the factually accurate, mind...

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Moon Monkey
The Sun does tend to be more interested in the dramatic than the factually accurate, mind...

Lol yeh, I was going to mention the source was not the best....just an interesting development if true. Possible mobile systems access while BA are worrying about exactly the same thing on their new Boeing purchases, on a flight to Beijing, whilst Brown was taxi-ing out on his way to Beijing, on a flight path that comes in over central London. :ph34r:

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Hmm a new theorey is coming out about crossed lines and cell phones interfering, not sure how likely it is though or whether it could be done on purpose:

http://www.thesun.co.uk/sol/homepage/news/article711639.ece

I for one am not so convinced that a cellphone can cause a computer crash. It could interfere with the ILS or the NAV receivers (which in itself id bad enough), but unless you have a 5Volt (clock) input to a computer I don't see it. To cause a five volt radio frequency field at 10 feet away you need a few kilovolts at the antenna (which would be the "superpimped" cellphone).

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keithisco

Cell phones? Not really, the control signals invariable use PWM (pulse Width Modulation), Amplitude Modulation, ARinc 429, some RS protocols etc, and are all very well shielded (normally twisted - pairs + shield). If the shielding was degraded then I could see some interference, but nothing that would even remotely suggest that manual control would be affected.

Kinda coming back to the software "glitch" idea, and am moving my thoughts onwards to the idea that the Auto functions were still enabled and that manual control was never re-established....

"and thats the way the cookie crumblies" (Bruce Almighty, such a good film :lol: )

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Moon Monkey
I for one am not so convinced that a cellphone can cause a computer crash. It could interfere with the ILS or the NAV receivers (which in itself id bad enough), but unless you have a 5Volt (clock) input to a computer I don't see it. To cause a five volt radio frequency field at 10 feet away you need a few kilovolts at the antenna (which would be the "superpimped" cellphone).

You don't need to crash the computer. If the signal to the engine is not hard wired 'all' you need to do is gain access to and set the input signal to transmit zero and all systems in the control system will read as being ok and working fine.

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ships-cat

Back in the late 1990's, the 'new' GMS digital mobile phones crashed servers in our computer apparatus room. However, these computers where NOT shielded against RF. I'm sure the systems on an aircraft WOULD be.

However, as a hyphothesis: if you started bombarding an aircrafts systems with EM pulses then we would expect multiple failures and error signals. This didn't happen in this case.

Meow Purr.

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Unlimited

This is truly an interesting case...whats the faa or any agencys saying?...

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keithisco
You don't need to crash the computer. If the signal to the engine is not hard wired 'all' you need to do is gain access to and set the input signal to transmit zero and all systems in the control system will read as being ok and working fine.

All signals ARE hard-wired

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keithisco
Back in the late 1990's, the 'new' GMS digital mobile phones crashed servers in our computer apparatus room. However, these computers where NOT shielded against RF. I'm sure the systems on an aircraft WOULD be.

However, as a hyphothesis: if you started bombarding an aircrafts systems with EM pulses then we would expect multiple failures and error signals. This didn't happen in this case.

Meow Purr.

You are right SC (can I call you SC?) radiated, induced, and conducted RF signals are heavily tested (RTCA DO160E Ch. 20), and part of the Certification requirements in all commercially licensed aircraft. The frequency sweep in the testing includes all Mobile phone frequencies

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Diedtrying

Here's a couple of piccies for you all.

Starboard

linked-image

Port

linked-image

port u/c

linked-image

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Moon Monkey
All signals ARE hard-wired

Sorry, of course, I am not talking about wireless, I mean the digital signals on a circuit board as opposed to the old-style cabling. Do you know the volatges used from the autopilot and the bit size of the converter when the pilot over-rides ? When the pilot over-rides is it through an old-style cable or are the same digital signals used just missing out the controller ?

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keithisco
Sorry, of course, I am not talking about wireless, I mean the digital signals on a circuit board as opposed to the old-style cabling. Do you know the volatges used from the autopilot and the bit size of the converter when the pilot over-rides ? When the pilot over-rides is it through an old-style cable or are the same digital signals used just missing out the controller ?

Sorry MM, I am not conversant with Boeing, just with Airbus... with manual override invoked then a completely isolated (from the auto function) circuit board is used to translate the joystick and throttle positions to Control Commands. These are double redundant for EACH engine, this is why I am thinking that the Auto function never dis-engaged.

The circuitry is completely isolated in each case, there is no single point of interaction.

Does anybody know which engines were on the aircraft? I suspect GE or RR.

note:edited to add 2 comments and requests

Edited by keithisco

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Sorry, of course, I am not talking about wireless, I mean the digital signals on a circuit board as opposed to the old-style cabling. Do you know the volatges used from the autopilot and the bit size of the converter when the pilot over-rides ? When the pilot over-rides is it through an old-style cable or are the same digital signals used just missing out the controller ?

triple 7 is an old style pulley, purely mechanical, no electronics involved.

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Moon Monkey
Sorry MM, I am not conversant with Boeing, just with Airbus... with manual override invoked then a completely isolated (from the auto function) circuit board is used to translate the joystick and throttle positions to Control Commands. These are double redundant for EACH engine, this is why I am thinking that the Auto function never dis-engaged.

The circuitry is completely isolated in each case, there is no single point of interaction.

From what I have read about this accident and this plane for both engines to refuse power at the same time it MUST have been a command from somewhere, I just wonder where ?

eidt: it had two Trent 895 engines, manufactured by Rolls-Royce.

triple 7 is an old style pulley, purely mechanical, no electronics involved.

Not according to wiki:

http://en.wikipedia.org/wiki/Boeing_777

Edited by Moon Monkey

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Back in the late 1990's, the 'new' GMS digital mobile phones crashed servers in our computer apparatus room. However, these computers where NOT shielded against RF. I'm sure the systems on an aircraft WOULD be.

However, as a hyphothesis: if you started bombarding an aircrafts systems with EM pulses then we would expect multiple failures and error signals. This didn't happen in this case.

Meow Purr.

I still don't see, GMS phones at that time had less than 2 Volts output at the antenna at 400 MHZ, the computer clocks in those times had around 5 Mhz...? unless someone put the phone right into the case touching the RC clock there is no way.

Flip flops don't flip or flop beyond hysteresis, and that is 4.5 Volts.

BTW, my computer case is not tempest proof and so far neither my cell phone nor my cordless has managed to crash it, though my computer has managed to interfere both.

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keithisco
triple 7 is an old style pulley, purely mechanical, no electronics involved.

Really? Thanks for that QM, so actuators relied on mechanical stress to implement manual control? Does this mean that in manual configuration that fuel flow is determined by throttle position, and does this also mean that FCMC and FMGEC computers are by-passed? Even so, both engines not reacting to the manual commands still suggests (to me) that the auto function never dis-engaged.

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Really? Thanks for that QM, so actuators relied on mechanical stress to implement manual control? Does this mean that in manual configuration that fuel flow is determined by throttle position, and does this also mean that FCMC and FMGEC computers are by-passed? Even so, both engines not reacting to the manual commands still suggests (to me) that the auto function never dis-engaged.

We are talking several circuits here, the autopilot (or autothrottle) just moves the same throttle sticks as the pilot would. Then there are several shut-off valves powered by solenoids. So as far as the throttle setting everything can be bypassed, as far as the fuel supply I am not sure.(That is why I was looking for a maintenance manual).

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From what I have read about this accident and this plane for both engines to refuse power at the same time it MUST have been a command from somewhere, I just wonder where ?

eidt: it had two Trent 895 engines, manufactured by Rolls-Royce.

Not according to wiki:

http://en.wikipedia.org/wiki/Boeing_777

Fully digital fly-by-wire flight controls with emergency manual reversion

That means precisely that. There are traditional pulleys to operate the plane.

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Moon Monkey
That means precisely that. There are traditional pulleys to operate the plane.

You said there are no electronics involved however it seems that it is all electronics unless in an emergency the pilot chooses to "go outside the control envelope". Can you link me to something where it says the manual override reverts to cable/pulleys as it seems that would add an awful lot more complexity/weight/lack of reliability etc. and defeat the whole point of going down the fly-by-wire route in the first place. It would be more sensible to have redundant electronic circuits for manual control.

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