GonzoXL5

I work in business systems IT and not in any aviation based profession

Given that they've still been unable to find any indication of a mechanical fault yet this is something significant enough to affect both engines, what do you guys think are the chances of this being a software problem ?

nlarbale

From the AAIB's statements on the functioning of the aircraft systems, it appears that all software systems in the Autothrottle and EEC's (and elsewhere) functioned as expected

hetfield

Would even 4 engines have done the same.....?

IcePack

Mmm! pulling the fire handles at 700 ft. Now would that have the same affect?

Actually I see from other posts that the QAR did not record the last 45 secs. But I guess the FDR would have. So am just wondering when the handles got pulled. After it came to a halt I guess, interesting senario on the post impact fuel spill.
I'll go back under me rock.

sispanys ria

It is really surprising to see that both engines lost power at (almost) the same time, and in addition, they both came to same low RPM (above flight idle). In case of ice obstruction, it's already quite unlikely to expect a simultaneous event, but how can it lead to a similar low thrust setting on both engines ???
It means both ice obstructions did let a similar leak on both sides...

Correct me if I'm wrong, but up to now, it's only the indicated fuel quantity that was reported, not the actual fuel found in the wreckage...
I just want to remind that Tunintair had a fuel exhaustion accident while indications were showing adequate fuel on board... Is it really impossible to consider low fuel conditions causing the cavitation in high pitch attitude ?

grumpyoldgeek

I'm wondering if there's a fuel pressure transducer downstream of the metering valves and if so, was the fuel pressure logged.

snowfalcon2

Hi Topslide6,

thanks for the comment. I just like to stress that I'm not blaming the crew in any way here. The situation was apparently so extraordinary that one can't realistically expect more.

grebllaw123d

sispanys ria,

You are right - only the indicated fuel quantity is mentioned in the report, but the report also mentions that samples have been taken from the 2 wing tanks.

Later in the report the following statement is given:

avrflr

So you are saying that despite the fact that someone got inside the wing tanks and found a plastic scraper, a piece of tape etc it didn't strike them as odd that there was no fuel in there? You should call the AAIB and point out the mistake they are making.

Re: water/other fuel contamination - there wasn't any. The AAIB report makes fascinating reading. I highly recommend it.

sispanys ria

avrflr i'm sorry you cannot post a polite reply. I'm just interrogating myself, and never mentioned fuel exhaustion, but in a low fuel configuration, it might have been possible that the tank LP pumps were not able to provide the adequate fuel to the HP pumps...

As you refer to the small items found in the tanks, I would like to see how you explain that almost simultaneously, two different items would have reduced two fuel flows to two similar values on both engines...

Hand Solo

The thing had ten tonnes of fuel on board. There was no low fuel state. None. Ever.

AEROJUANCA

Water and ice cristals are normal into the airliners tanks,and comes with the air that vent tanks entering by the NACA inlets near the wing tips,not during refueling.
Also,to much debriss to block both booster pumps per wing tank...the engine fuel feed lines in the 777 are about 3 inches diameter.

avrflr

Terribly sorry for being so rude old chap, but ten and a half tons is not a low fuel configuration in my book. Plenty of 777s fly around happily with less than that. I wasn't suggesting that the debris found caused the accident, just pointing out that the contents of the fuel tanks has been given a thorough examination. If there was no fuel in the tanks, or less than the gauges indicated, they would have figured it out, I promise you.

I can't explain how the accident happened, but then neither can the AAIB at the moment and they do this for a living. They are not stupid or corrupt, if the answer was simple, like low fuel or contaminated fuel, they would have told us on day 1.

Pinkman

Gerry, you are reading my post literally. Replace 'post - event' with 'after the event' and you will see what I am trying to say: "how can you tell, from the evidence, when you look at the impeller after the event, that cavitation, which is a transient phenomenon, has actually occurred". Apologies for my clumsy british english phrasing. And the answer was given above by several people: pitting, damage, caused by huge pressure forces and detonation.

But despite all the slightly sarcastic comments to my earlier post no one has answered my question: If it isnt ice, wax, or water, what other common mode control law reduced one engine seven seconds after the other? I still refuse to believe that there is 100% independant authority and segregation between the two engines at all times and that there is never ever a point or situation at which the two engines in a modern aircraft with digital engine and fuel management controls have the function to compare thrust and balance accordingly. I just cant believe that you guys have to either continually adjust throttles to compensate for small variations in thrust between engines or use rudder trim to keep a constant heading (eg in the cruise)? How fuel inefficient that would be. There must at some point and in some flight modes be a digital comparison between the thrust produced in each engine and my question is still, is there concievably a flight mode or condition such that when one engine unexpectedly loses power (eg if fuel feed blocked by a red plastic scraper) the other engine is electronically limited to avoid... well you tell me. There must be a 777 sparky out there who has the FADEC decision logic.

Otherwise, there's only one explanation.. different pieces of crud left behind in different wings just happened to block respective fuel filter screens just seconds apart. I dont believe that and neither do you...

airfoilmod

My reading was that the Fuel was "in Spec". Is that "within Spec" for pure Fuel or does that consider that there is no "Spec" for Water, Alcohol, Glycol, or Canal Mud? I'd like to see collection protocol, transit, and testing methods before I defend the FUEL. (As in, what reality offered in the way of combustible supply to RR1 and RR2.) Just Sayin'.

PBL

I have stayed out of this so far, but this supposition must be corrected.

The certification process and 3.6 million flight hours says virtually nothing about manifestation of SW faults. For an example, consider that the certification process and a large percentage of those flight hours failed to discover a significant bug in the flight control SW that manifested itself first in August 2005 out of Perth.

PBL

avrflr

The spec for the fuel includes that it must contain less than (I think) 30 parts per million of water and that it must be free of solid contaminants. The AAIB report states that there was no significant quantity of water or other contamination in the fuel samples taken. I take this to mean that, being clever chaps, they considered the possibility that fuel contamination caused the accident and they went looking for it. They took samples from various parts of the engines, fuel system and tanks. If there was free, suspended or dissolve water, or solid contamination, or off spec fuel, I for one think they would have found it. I would like to know where this phantom fuel contamination went to hide from the investigators.

Pinkman

As an ex-fuel guy, if they've sampled properly, and actually taken a sample down to the worst case temperature and its OK, then its not fuel - period. And hopefully none of you - especially Danny - will remember what I offered to do if I was wrong in asserting it was waxing.

airfoilmod

I don't think I'm committing what I deplore. A conclusion of any kind is premature, speculation never is. Having been tested, the Fuel, to me, remains to be exonerated. Speculation, by its very nature, could lead to incrimination, which is silly at this point. My retort had naught to do with clever chaps, but ill advised exoneration of any procuring cause, which the chaps have not done, and someone, I think, thinks they have.

avrflr

You must know something about fuel that I don't. If testing won't exonerate it, what will?

I'm all for speculation, but let's have hypotheses that don't require me to believe that the AAIB are morons. Or that jet fuel has acquired some hitherto undiscovered properties that can't be revealed by fuel testing laboratories.