BA 777 landing accident at LHR

[ATFS_Crash]

Intentional sabotage or terrorism is a stretch at this point. If anything, unintentional poor maintennace practices is a likelier cause. Without a/c maintennace records being revealed or any further facts it's obviously just a speculation. The airline I used to work for had numerous issues with maintennace personel in China not following AMM and just "making things work".

Like many you seem to be trivializing sabotage. Sabotage IS terrorism.

As I said before; I think terrorism is a very improbable, but so far I see nothing that rules it out.

As I said before; I think we should stay objective, I don't think we should prematurely eliminate other possibilities even though they are unlikely.

As far as speculation. Speculation is our intent. At this point any probable cause is speculative. Often even conclusions are somewhat speculative. Many of us like to speculate before all the evidence and findings are available; so we can see how good our speculation is and to try to keep sharp and learn.

Some of us want to make sure that people remain objective. It's like before 9/11 most people were not objective about airline terrorism; because they assumed the terrorist would continue their MO as they have before. Regrettably we had a policy of limited cooperation with airline hijackers, that prejudice policy burned us on 9/11 because we were not objective and our policies were based on stereotypes.

Like I said before I think we should follow the evidence instead of prematurely ruling out possibilities.

As I've said before, I think the most likely cause is some sort of electromechanical fault (ranging from electronics, wiring, fuel pumps, fuel control/management to software issues).

I think the next most likely is something like a fuel quality problem, such as water, fuel icing, fuel foaming, fuel jelling or other contaminants.

In addition I think we should keep in the back of our mind that there are other more remote possibilities or contributing factors. Such as RF interference or sabotage/terrorism.

A good crash investigator should focus most of their attention on the most probable, however they should remain objective and consider (keep an open mind to) the improbable. Instead of ruling out possible causes. Investigators should follow the evidence.

A cause is not always known, often the finding is the most probable cause. That doesn't always mean there isn't a shadow of doubt that there was something else.

Like I said before if a problem is found, we then have to determine why. If something is found to be a maintenance issue, we have to look more deeply into why it was a maintenance issue. Was it from counterfeit parts? Was shortcuts taken, because of, laziness, cheapness to expedite and or keep costs down, or was it sabotage?

Sometimes it all comes down to motive and intent. If someone forgets a step, that could be considered an accident. If someone cut corners, that can be considered criminal (an accident in the making). Sabotage (deliberate with malice) can be considered extremely criminal, such as terrorism.

Ignore stupidity.

Stupidity is the most frequent cause of most mishaps. Stupidity should be considered as a possible cause factor in any crash investigation.
(due to your vagueness, I realize this may not be the context you meant)

[3WE]

...Regrettably we had a policy of limited cooperation with airline hijackers, that prejudice policy burned us on 9/11 because we were not objective and our policies were based on stereotypes...

ATFS, you are somewhat off base here.

"Objective" means based on what you know, as opposed to what you think.

Pre 9/11 policies were extremely objective: Until then, hijackers had very strong tendencies to not be on suicide missions. With few exceptions the "cooperation" angle was clearly the best, and this was backed by objective data on what hijackers do, as opposed to stereotypes that some Muslims are capable of suicide attacks and shouldn't be let in the cockpit, even if it means dead flight attendants and passengers.

If you want to fault pre 9/11 policies then fault them for not being subjective and speculative enough.

I agree that it is very sad that previous hijack experience and policy helped the 9/11 terrorists get cockpit access.

It is also possible that some intelligence was over-looked, but over-reacting to possibly subjective claims sometimes does more harm than good.

The objective analysis of the data before 9/11 clearly pointed to the "cooperation" policy. Sadly, the 9/11 hijackers were able to capitalize on this.

[Dmmoore]

ATF-CRASH, and all.
Please cease all terrorism speculation and bring this thread back to this accident.

In the event the AAIB or other official agency indicate that some form of terrorism could be the cause.

Future terrorism posts in this thread will be deleted.

Please open a thread on terrorism if you wish to continue.

Thank you for your consideration.

[Smilin_Ed]

B777 Throttles

Does anyone here know:

1. Is there any mechanical linkage between the throttles (power levers) and the fuel control?

2. Is there any means, as in much older aircraft, to switch to Manual Fuel Control, whereby the power lever directly controls metering of fuel to the burners? (In much older aircraft, there was a switch which bypassed all the fancy fuel flow controls and allowed the pilot to manually meter fuel.) You had to be very careful not to overtemp.

Also: I recently read that in some models of Airbus, there is a prohibition on using full flaps with very low fuel states because the use of full flaps at proper approach speeds results in a deck angle which cuses fuel to flow to the back of the feed tanks and unport the fuel boost pumps.

[Dmmoore]

Does anyone here know:

1. Is there any mechanical linkage between the throttles (power levers) and the fuel control?

No. It's all done electronically. In this case the throttle system worked as specified.

2. Is there any means, as in much older aircraft, to switch to Manual Fuel Control, whereby the power lever directly controls metering of fuel to the burners? (In much older aircraft, there was a switch which bypassed all the fancy fuel flow controls and allowed the pilot to manually meter fuel.) You had to be very careful not to overtemp.

No such system has been used on commercial aircraft during the last 40 years.

Also:

I recently read that in some models of Airbus, there is a prohibition on using full flaps with very low fuel states because the use of full flaps at proper approach speeds results in a deck angle which cuses fuel to flow to the back of the feed tanks and unport the fuel boost pumps.

That's not the reason. Using full flaps lowers the deck angle and causes fuel to flow forward. There are two fuel pick up ports in the inboard end of the wing tanks, One port is forward, one is aft.

[Kell Kong]

Kind of reminds me of free speech in some Communist, Socialist and countries with dictators. You're allowed to have free speech and free thought, as long as it is the same as the government.

That is a bit exagerated and radical... Don rightly tried to remind you that this obviously had nothing to do with this incident, and can easily be ruled out.

Now why don't you open a new thread on this, you are totally free to do so..

[Smilin_Ed]

Throttle System

[QUOTE=Dmmoore]No. It's all done electronically. In this case the throttle system worked as specified.

If the throttle system worked as specified, why is software suspected?

[Dmmoore]

[QUOTE=Smilin_Ed]

No. It's all done electronically. In this case the throttle system worked as specified.

If the throttle system worked as specified, why is software suspected?

The throttle system worked correctly between the throttle levers and the EEC(according to reports from the AAIB). The EEC software is under very close inspection. Something between the EEC and the engine burners caused or became affected by what ever caused the roll back.

[Vinco]

An interesting thought, but what type of maintenance practices could result in an event like this? It's not straightforward to screw up in precisely such a manner that the engines fail the way they did...

I don't know. I'm not familiar with details of the engine. Possible maintennance errors are usually considered, which I'm sure they were in this case. But were found to be baseless or a more likely cause is being examined.

[Gabriel]

[QUOTE=Dmmoore]

The throttle system worked correctly between the throttle levers and the EEC(according to reports from the AAIB). The EEC software is under very close inspection. Something between the EEC and the engine burners caused or became affected by what ever caused the roll back.

Don, would you give us (or me at lest) a brief explanation of how the throttle levers' resolvers, the FADEC, the FCU, the ECC, the ADIRU (and whatever other box related to engine control is arround) work together?

[Dmmoore]

In brief. FADEC is in simple terms an electronic throttle system. Many new cars have a much simpler but similar system. Move the throttle in the cockpit and the movement is electronically carried out in the EEC. The EEC processes the information and signals the FCU (P&W Term for Fuel Control Unit) or MEC (GE Term for Main Engine Control) I don't know the RR term, to adjust the power. The unit controlling the fuel now adjusts the fuel. At the same time the device controlling the compressor VGV (variable guide vanes) adjusts the vanes to match the demand on the compressor at the new power setting.

Throttle position and engine parameters are sent directly to the flight recorder

On a Boeing aircraft the Auto Throttle in effect moves the throttle lever in the cockpit and all power actions are the same as above. Airbus is totally different. Do not try and transpose auto throttle and Airbus's auto thrust.

Boeing in effect moves the throttles as the pilot would to adjust the power. It makes no difference if the auto throttle signal is sent directly to the FADEC box or applied to the motor directly attached to the throttles, the throttles move in response to a command to change power.

[Gabriel]

In brief. FADEC is in simple terms an electronic throttle system. Many new cars have a much simpler but similar system. Move the throttle in the cockpit and the movement is electronically carried out in the EEC. The EEC processes the information and signals the FCU [...] The unit controlling the fuel now adjusts the fuel. At the same time the device controlling the compressor VGV (variable guide vanes) adjusts the vanes to match the demand on the compressor at the new power setting.

Thanks for your answer, which triggers more questions...

Are the ECC and the FCU sub-systems within the FADEC?
Is the FCU and "the unit controlling fuel" the same thing in your previous description?
What phisically controls fuel flow (a sort of valve, I guess) and how does that thing moves exactly what it moves? And the VGV?

I have more questions but that's enough for a starter...

Thanks again.

[Theoddkiwi]

The basic control systems work like this
(disclaimer: some systems may differ from the following blabber)

The EEC sends control voltages to the valve control which using a motive force then moves the valve to its commanded position. The valve will have 2 position transmitters which reports back to the EEC the valve position.
This is a standard closed loop control system.

If the EEC commands a new position, and either the valve does not move, it moves to an uncommanded position or there is a fault in the position transmitters circuit. The incorrect position transmitter signal will indicate to the EEC that there is a fault.

Because these systems are dual channel, eg two position transmitters A & B, if both indicate a position signal error then it likely an valve failure. If the error is on only one transmitter it is likely a transmitter circuit failure.

Either way a fault will log in the EECs fault history and give time and date info.

Depending on the system that has failed will depend on the effect. Serious faults will flag the pilots and possible revert to Backup Engine controls. Minor faults will only be indicated during maintenance checks and tend to be economical faults.

Bear in mind some valves only have one position signal but there will be two valves located in different locations on the engine. End of the day there are two of everything and everything is being monitored and cross checked.

[Gabriel]

Thanks!

Next question would be, backup engine controls?

Serious faults will flag the pilots and possible revert to Backup Engine controls.

I thought that the redundance was achived via doubling channels, sensors, etc, but that there was no backup system as such (like a mechanical reversion)

(I know, I saw the disclaimer)

[snanceki]

Maybe Theoddkiwi is referring to a process similar to "Limp Home" on your auto.

If certain input signal(s) is out of range then a default value is used which gets you home but with various limitations. e.g. max speed, gear change quality etc.

As you state there is no mechanical backup connection.