airfoilmod

Would you explain your vague terms? "Exceeded"? "From several sources"?

Because if you are suggesting the Fuel is surprising people, you are also suggesting the Trent has an anomalous "fuel problem".

Be specific, explain your statement, err, "fact", ( for Mr Mouse., and the rest of us).

See, the problem appeared to be specific to the Trent 800, has it expanded into other types? You see where you're going?

AF

Carnage Matey!

OK, specifically for the semantics game, the fuel freeze point for the Chinese fuel was colder than required for specification, the water content was lower than the permissible maximum. In that way it exceeded spec. There's no problem talking about something exceeding spec. Every engineering organisation I've worked in (and thats quite a few) has had no issue with describing something as exceeding spec. Nonetheless talk about exceeding spec is a pointless word game and all this could all have been gleaned from earlier posts.

The behaviour exhibited by water molecules in very cold fuel is not as expected and investigations are ongoing to establish what mechanisms and behaviours are at work. The Trent 800 is the only engine being investigated initially and it would appear that specific interactions could exist between the fuel/water mixture and elements of the Trent fuel feed system that could lead to unexpected ice accretion. Boeing intend to test the entire 777 fuel system to see if the fault could occur elsewhere in the system. Given that the unexpected fuel/water mix behaviour will be common across all aircraft operating in similar environmental conditions it's quite plausible other aircraft types could be affected.

airfoilmod

And it is "expected" the fuel problem "will be" common across all other a/c operating in similar environment? The semantic problem isn't mine, sir.

You describe Boeing's "intention" to test the 777 fuel system. When will that happen? After another year?

Please look at your last sentence. This is not the verbiage of science.

"It's quite plausible that other a/c types will be affected?"(italics mine).

It sounds like a reporter with an agenda.

Pinkman

When CM says 'exceeded' he means, in the case of freezing point, that it wasn't just ' - 47 deg C' (the usual spec of jet A-1) because it was in fact RP-3/Jet Fuel Number 3 which is what is sold as equivalent to Jet A-1 in the Chinese market. There is indeed a common phrase "meets or exceeds" spec in our business so you are wrong about that although from a fit for purpose / contractual point of view, yes, it either meets spec or it doesnt. It did. By miles.

What he has also said or implied is that the detailed research is discovering some heretofore unknown relationships between fuel composition and extended exposure to extremely low temperatures.

Given the fact that Chinese Jet is probably wide cut, that is of no surprise to me, and although I am nowhere near the investigation it also wouldnt surprise me if there were to be discovered that there were a physico-chemical interaction between wax from wide-cut product (similar to diesel in winter) and microscopic ice crystals under these conditions. Its a personal guess, and I would bet my house on it, but it will be something like that.

I cant see that he is at all suggesting the Trent has an anomalous "fuel problem", although if you ran RR Trent and GE 90 together under identical conditions it would be unlikely that they would both respond identically. One would inevitably be slightly more sensitive than the other to low temperatures and variations in certain fuel components and on the basis of one incident you couldnt say which.

What he didnt say and what it WILL do is to introduce an additional and/or an altered test for freeze point and maybe introduce additional tests or change the upper limit on aromatics or density, and possibly some other parameters. Now that I would bet my house on.

Pinkman

airfoilmod

Noted. However, the implication is the fuel is "better" than spec. OK.
Then where is the problem? The spec? or the fuel/Trent lnterface. If other systems are not being tested, where is the "new" or "surprising" data. Either the Fuel effects are singular to the Trent, or NOT. If singular to the Trent, whose "problem" is it? Suggesting a new and mysterious chemical profile for Jet Fuel is irresponsible. One CANNOT have it both ways. Bad Fuel? Trent/Fuel interaction?

Pinkman- "meets or exceeds spec." though old, and tried, implies a "value" and to me doesn't belong in a description of Fuel. One wonders how the FP is "exceeded? What mechanism? Lights? Melamine?

AF

Carnage Matey!

Are you a fan of 'Loose Change' Airfoilmod? If you are going to quote me at least do it accurately. I said:


I did not say:

My statement is a simple logical conclusion that if we are discovering a new interaction between fuel and water then as all aircraft use fuel (with some water in it) then all aircraft could be affected. There's nothing contentious in that unless you are looking for some sort of conspiracy theory.

As for the Trent/fuel interface issue, the Trent is the only engine under close scrutiny as this is, I remind you, an accident investigation on a Trent powered aircraft. If unusual behaviour is noted in the Trent no doubt subsequent tests will be performed on other engine models, but first you need to know what to test for and that is what the investigation is trying to establish.

Boeing will get round to testing the fuel system just as soon as they can finish building the full scale 777 fuel system inside a large vacuum chamber that can create and sustain temperatures of -73C and lower for a prolonged period at low atmospheric pressure. That sort of kit doesn't get built overnight.

There's no question of bad fuel, just that we don't know as much about good fuel as we thought we did.

airfoilmod

Appreciate the patient reply. Let me try a different course, I seem to be having difficulty with language.

You suggest the Trent is being singled out for testing because it was fitted to the accident a/c. Also that Boeing will follow up by testing the 777' complete system by way of mockup, to eliminate (or implicate) the airframe.

I do see your point that the Trent is not being impugned to now. What is alarming to me, (taking as fact your statements re: FP/Fuel), is that there is a new horizon of unexplored chemistry re: FUEL. This is disconcerting, since I fly alot and frequently on ETOPS cert. a/c. That Boeing hasn't finished their mockup, and other engines are not being tested, my assumption is that either the Trent or the Fuel is drawing most suspicion, or the several investigative bodies are being rather careless with conclusions needed on a more timely basis.

Are Chemists that expensive? Forensic Metallurgists? I'll help pay. As will all who fly.

Carnage Matey!

I'm afraid you are going to have to be more patient airfoilmod. Given that this is the only known incidence of this phenomena occurring in service I think the odds are on your side next time you fly. Temporary measures have been taken to minimise the chances of a repetition.

Unfortunately it's just not as simple as saying it must be the fuel or it must be the Trent. It could be both. The fuel clearly is introducing the contaminant (water) into the system. The question is why does it form ice accretions? Do these form only because of the fluid dynamics in the Trent system? Do they form elsewhere in the 777 fuel system and only become trapped in the Trent because of it's design? Could this occur in other designs? Are there geometries which encourage ice accretion which are not specific to the Trent? At the moment all they can confirm is that in a certain part of the Trent ice can accrete under certain conditions, but given that nobody has tested any other engines like this nobody can say for sure whether other engines could be affected.

This is fairly blue-sky research and throwing money at it doesn't necessarily give you an answer any quicker. If it did we'd all be using our fusion reactors to power plants manufacturing an HIV vaccine.

airfoilmod

I try not to read too much of inference into web posts. It's useless. So.
You say the Rollback on 038 is the only incident of its type? Not so. Unless you mean the only one causing an accident.

If you "sense" impatience in my post, you are correct. I believe I share this with others who have posted on this thread. I draw my conclusions from what I read here.

Does this "new frontier" of Fuel chemistry concern you? While flying, I never got completely comfortable hearing ATC tell me: "Standby". Tell someone else, is what I was thinking. Not irrational, considering I was giving over my flight to another, if only temporarily. The same holds true here.

Long ago, I was downwind on first solo, abeam tower. "Cessna xxxJ extend downwind for Aztec landing straight in." 3 MILES later, I timidly called Tower requesting a base turn. Never been patient with other authorities since; at least not completely.

AF

Aside: by the way, could the reason no other engine types have been tested "yet" mean anything to you?

airfoilmod

you mention that in certain areas of the Trent ice can accrete? That is possible, but Captain Cargill claimed the ice formed first, before entering the Trent. I'm still assuming (among other assumptions) that the heat exchanger (Fuel/Oil) is the "pinch in the pipe". Tiresome, these bleats to "wait for the report". Of course; meanwhile I think discussion is allowed.

Carnage Matey!

If you mean the only rollback in which ice accretion is strongly suspected of being the cause then yes, I believe it is. Other than that I can't add any more. I'm not involved in the investigation and will have to wait for the report just like you.

airfoilmod

While we're waiting, I'm still interested in your statements that Fuel is behaving in ways hitherto unknown to the flying and chemistry community.
For obvious reasons, and I'm not winding anything, can you explain your post? M.Mouse called it the introduction of a FACT. Educate Me?

AF

Carnage Matey!

Like I said, I can't add any more. I don't know anything about the mechanisms at work, only that the behaviour is not as expected/predicted and they don't know why.

airfoilmod

You cannot add more? You make a statement that is frankly, wild and unsubstantiated, and you can't explain or quote sources?

You will excuse me if I take exception to your posts and to Mr. Mouse's ill founded support.

Regards, AF

FullWings

AF,

I can sense your frustration (almost a disturbance in the Force) but there are many serious, lab-coat-wearing, possibly pipe-smoking engineers and scientists working on this problem and the ramifications thereof. I am told that the sum of available knowledge on fuel/water behaviour at different temperatures is not at the level that many expect it to be - there is an attempted remedy in progress. Please be patient.

Have you seen phase diagrams for plain H2O or Iron/Carbon? Amazing complexity for a pure chemical or simple mix; I wouldn't be surprised at all if some hitherto unseen weirdo behaviour of certain concentrations of water, hydrocarbons, temperature and pressure comes to light...

Re-Heat

AF

I see you are somewhat alarmed that it has been mentioned that we are dealing with hitherto potentially unknown properties of fuel. Regardless of what the AAIB and Boeing are currently investigating, you should perhaps instead think of the investigation as more of an intellectual investigation.

Not to detract from the seriousness of the incident last year, the key is that incidents such as that are now so rare, that the few accidents we do have are no longer caused by extremely obvious errors in piloting ability or build quality. It is natural that people will of course now work to reduce this risk as well, but you have to imagine this risk as miniscule in relation to all the others that have been dealt with over time in the past, and of more intellectual interest than of clear and present danger on ETOPS flights.

Under these circumstances, I believe that the AAIB and Boeing do not consider this event to have ever occurred at all before under these circumstances. Nor do they expect it to in the imminent future.

I understand that they think they know what caused it, that procedures have already been altered to minimise the risk, but that the exact, precise chain of events is hitherto still unknown.

We live in a modern world where everything is instant - there is a reason many of us are not research scientists, as we are not patient enough. There is however a place for the detailed and diligent work that those people are doign right now, and will be for some time on the problem that occured to the aircraft.

airfoilmod

Thank you, that was kind. I may have an off-course read on the science; I doubt it, but without updates, one is left with slim pickens. What is apparent, assuredly is my lack of Faith in the state of the authority vis-a-vis daily ops. The silence is speaking volumes. The pipe smokers will never change, that's a good thing for the most part. The change that is needed is a posture of willingness to disseminate results and show at least a feigned interest in safety and a shoring up of consumer confidence, by communicating with the client. The industry is wicked safe, but the bureaucratic nonsense of the authority is maddening and does little to add to the perception of safety among those who fly and couldn't care less about cascading nucleation.

And thanks to ReHeat.

AF

Machaca

The composition of crude oil varies considerably by region and even batch.

There are several methods of refining crude oil into desired base products and removing much, but not all, of the undesirable compounds. Additives enhance the refined base products to ensure they will perform to established specifications.

There are dozens of specifications for each product -- some are maximum limits, some are minimum limits, and some are range limits. The resultant finished products meet or exceed specs, yet still vary by region, batch, process and additives.

Carnage Matey!

My statements were neither wild nor unsubstantiated. I suspect Full Wings is getting his information from very similar sources to me, none of which are worthy of quoting because none are directly involved in the investigation. They get updates from the AAIB as a courtesy as the operators of the accident aircraft. Furthermore there's nothing in my postings regarding the fuel which couldn't reasonably be deduced from the information already in the public domain by anyone with a reasonable level of scientific competence. If you find the slow release of information from the investigative authorities frustrating then I'm afraid it's just tough luck. Investigation is not a process best served by a daily news bulletin or an hourly update on Twitter and nothing you or I do is going to change that.

airfoilmod

Had you offered a source of what seemed a rumour, that would have been satisfactory. Nobody appreciates the coy one when discussing serious matters. Just my opinion.