777, A very specific questions thread

[Loose rivets]

Could I suggest a "777, A very specific questions" thread?

By this, I mean just one point at a time being established and answered by people with specific knowledge of the subject.

By all means read in, but please let the experts answer.

Normally, I would put such a thread on the technical forum, but the Treble Seven accident is very serious. Thankfully not because of passenger injury, but because of what it means to Boeing and their customers worldwide.

If there is a computer fault it may be very, very difficult to prove. Electronic and software faults can be incredibly difficult to find. The intermittent ones, by their very nature, may not reoccur for literally years. Sometimes there is only the process of elimination left to designers and engineers.

Investigators will likely find the most probable cause, but during the history of accident investigation, there have always been those that disagreed with the findings, sometimes passionately. But there has not been any further investigative path to take.

There have probably never been so many people taking an interest in such an incident, and the fact that the whole world is asking why, is very significant. So, the more people that question the minutiae, the better. Something just might come out of the mist.

Could I kick off?

I recall special handling procedures for low fuel on the 727. Not rotating too far on an overshoot was one of them I believe. (This may have only been one companies's policy. I don't know.)

Are the reports of the apparent turn/roll/wing drop, reliable? If so, could this aircraft's control system allow a momentary side g-force long enough to slop minimal fuel away from the scavenge system and allow air into the fuel lines?

[Halfnut]

Rumor at my company is there was around 20,000 lbs. of fuel left in the tanks. And yes we have triple sevens.

[019360]

All of that is possible....however all would have been preceded by the mother of all barrage of EICAS warnings as well as good old plain airmanship...watching the fuel gauges....absolutely inconceivable that a crew, especially a BA crew, would have noticed nothing and said nothing until 600 ft.

If they'd given a fuel low Mayday call at 10,000 ft in the hold it would be different....but they didn't.

[Wizofoz]

20 000lbs = 9000 KG = Plenty.

I got in fron flying a 777 JFK-DXB last night. We had left DXB with 126T of fuel and shut down at JFK with 4.9. Tight but in no way an unusual or emergency occurence (Mayday would have been if we were going to land with less then Final Resereve = 3.2)

Arrived last night with 9.5 which was comfortable.

LR, the 777 has a similar procedure in response to a low fuel warning, which activates at >2T in either main tank. Wouldn't have happened here.

IF he had that much fuel, then the fuel state is not a factor.

[Loose rivets]

Well, it wasn't the final fuel per se, given that somewhere someone said a min of 7 tonnes legal; later to be suggested that they arrived with 11 tonnes.


What I'm asking is if a sudden un-accountable side g-force could displace first-approach fuel to the point where air is allowed in the lines.


We have two things. One is the reported apparent turn. The other is a sudden loss of the ability to spool up.

It would have to be a heck of a tail-wag, but these things happen.

There seems to be no reason for that turn -- if it happened at all. There has been no report of a late runway change for example, so the reason that more than one person is reported as saying that the aircraft seemed to be in a steep turn remains a mystery.

Edit to say. Of course, I'm ready to accept that the 777's control system would never allow a unbalanced turn/tail wag of this magnitude, so even if the lines could cavitate, it would only open another series of questions. Having said that, my dead heading in 777s was a trial when down the back- due to an inherent battle of wag and yaw-damping function.

[CSilvera]

Isn't that what the tech log forum is for?

[Loose rivets]

Yes, that's what I said in the intro, but this is such a major issue. I enjoy the tech discussions, and read carefully the items written by experts, but I'm suggesting that this is worthy of a tech discussion on what is in effect the main forum. No doubt the mods will make that decision.

If no fault can be found with the aircraft or the crew, it will leave the type with a huge question mark over it. We are not just talking about a main manufacturer, but the very validity of handing more and more of our control over to black-boxes.

[grumpyoldgeek]

Where are the FADEC's physically located on the 777?

[Jabawocky]

Grumpy....a pretty fair question, given the kind of "incident" that QF had recently that could have ended far worse......all for the sake of some cracked drip shields and unwanted liquids!

J:ok:

[Meadowman]

Grumpyoldgeek,
FADEC stands for "full authority digital engine control" and it does not physically exist, like say the EEC's do.(electronic engine controls.)
So FADEC is a name for the way the engines are controlled.

[SuperRanger]

on the trent 895, the EECs are mounted on each engine.

[Jabawocky]

Ok, being more specific then based on the intent of Grumpyold's question....is there a common point or several common points where a possible liquid strike could cause such devastating results. The throttle levers themselves is a start, but unless they spilled a cup of tea into them......

I know the 744 is different and the QF incident is quite different, but a similar kind of liqud event in a concentrated place of common coupling might just do it.

Any 777 systems guys know the answer?

J

[Meadowman]

My airline, and I'm sure many others, has rules about the way liquids are handled on the flight deck. Any liquid spilled on the centre pedestal could have very serious consequences. I think getting liquid into the thrust levers of the 777 could happen fairly easily if somebody does not follow the rules or is clumsy. Definitely would not happen at 600ft but, of course, could have happened earlier.

[conquest7]

What was the rate of descent on intercepting the GS?
What was the IAS?
Are we talking 600' aal or QNH?
What was the thrust lever position at that point?

[4Greens]

The pilots had to trade speed for height to make the airport. They may well have approached a stall situation in which one wing stalls before the other. Loss of directional control is then normal. High bank angle the result.

[mutt]

The pilots had to trade speed for height to make the airport Was this in the AAIB report?
They may well have approached a stall situation in which one wing stalls before the other Or this?

You appear to be assuming that the sequence of events was a near stall, loss of directional control, lateral displacement of the fuel and then fuel starvation to both engines at exactly the same time?

Is this logical?

Mutt

[ETOPS]

Can I just kill this "bank" business before we get in too deep.

The eyewitness who used the word "bank" actually was describing the high nose attitude or pitch angle but (unfortunately) used a term which has very different connotations for us here. On the video he can be seen indicating this with his hands as he describes, to the reporter, the very unusual sight which caught his attention.

When the FDR is played in public you will all see that the aircraft was essentially wings level throughout.

[CaptYanknBank]

Quote <<Are we talking 600' aal or QNH?>>

I don't think it'd be too much of an issue at LHR as it's only 80' AMSL.

[goudie]

Sensible thread LR
The question I have is:- are the engines controlled by totally independant systems or is there a point of commonality? I'm puzzled by the fact that both engines spooled down simultaneously. Therefore if there is no commonality in the engines control system then it would appear only fuel is the common factor.

[Milt]

The likely common link would seem to be the signals from the autopilot/auto throttle sytem attempting to maintain a set IAS.
Where does that signal split to the independent FADEC systems?