I'm a little disturbed by Boeing's AD.

As a purely precautionary document - three cheers (but does it add to anything more than last Autumn's FAA one ?).

However, it seems a little too intrusive into the inquiries being undertaken by the proper authorities.

However, most importantly, there is no indication in the Boeing inturruption as to how the unknown process managed to affect two separate systems so similarly in time and effect.

Too much seems to be being read into something which is too vague.

.

News management - a necessary strategy
 

Warning: I'm non-professional; not crew, not engineer - just scientist guest and thanks.

I suspect we are being given a lesson in global news management. I think it is a good and necessary lesson.

Investigators, Boeing and RR engineers etc. already know that the root cause of the BA038 incident is the state of the fuel in the tanks and pipes. For fuel temperatures below -18C the AAIB have stated,

"Below this temperature little is known about the properties of ice crystals in fuel and further research may be required to enable the aviation industry to more fully understand this behaviour."

Others here have agreed that the phrase 'little is known' is shocking. But, the industry cannot, and should not, allow that damning finding to be transmitted to the general public without first indicating that there are operational actions to hopefully avoid a recurrence, and a temporary engineering solution that can be retrofitted to a class of aircraft most susceptible to the problem, namely, Boeing 777s with RR engines.

Meanwhile, quietly, the industry concentrates its efforts on understanding what does happen to fuel on these long, high and cold flights and the more permanent solution to the globally pervasive problem.

This strategy is probably the only viable one to follow. I hope that the industry is actively trying to fill the hole in its knowledge, i.e. the behaviour of cold fuel.

I still think the fuel within the main tanks stratified in some form and that a pulse of "gloop", or slurry as Airfoilmod calls it (#2178), entered the delivery systems and partially blocked them.


Moving to tongue in cheek mode - Oh to be a fly-on-the-wall in the meeting room where RR are holding their forensic investigations into the decision stage on the FOHE design. Why that design, why not the GE or P&W one? Were the GE and P&W engineers just lucky or did they have knowledge that guided them, and if they did, was this available to RR? I've lots of follow-up questions but will spare you.

There is a lot to be learned about how the industry shares knowledge and, probably more crucially, the authorities must determine how it is that, this most technically advanced global industry, does not know how fuel behaves below -18C.

I'm still staggered by that.

Regards, Tanimbar

Tanimbar
 

The Press Release causes more problems than it solves, in my opinion. I am not expert in fluid dynamics by any stretch, but logic suggests the following.

It is highly unlikely there was liquid water any where in the fuel system of 038 for hours prior to the flight. If present as ice, then a "picture" of the state of the tankage would suggest that it was present as what? Cocktail ice? large blocks clinging to aluminum? That doesn't jive with the temps experienced by the a/c overnight or well prior to launch from Beijing. Block ice won't pump, and fuel won't "freeze" at all ambient temps. surrounding the flight. If the a/c brought it with on the flight in, that's one thing, but logic again suggests the problem arose on uplift in China. In spec. fuel would be carrying some quantity of water (as ice) in the uplifted batch.
As the flight progressed, this ice would "concentrate" in progressively greater quantities as it settled lower in the fuel system. At some point the siphon starts pulling high enough quantities of particle ice with Fuel such that it migrates toward the engines. Passing into the engines it converts to Steam and causes no particular problem. It may even enhance thrust at some miniscule value. However, it also, as a solid, would "fall out" of suspension and deposit in variable flow areas (due to specific gravity difference) and eventually create flow reduction.

It isn't particularly difficult to imagine this occurring at essentially the same time in both engines, ETOPS isn't foolproof, especially when systems are homogeneous and filled with the (same) Fuel.

I can't imagine what "Unimagined quality" the Fuel possessed to remain so mysterious. Rather than mystifying its audience, perhaps Boeing and FAA should tell the complete tale. A year on with new Physics/Chemistry/Fluidics? Stretches credulity. Just sayin'.

AF

I think that you need to keep in mind that this is not an engine design problem under regulations Part 33 (engines) but an installation issue under part 25 at the airframers. Considering that the understanding that we have today was not known by the regulators who approved the system, then you can assume that it wasn't recognized as well across multiple manufacturers.

lomapaseo, airfoilmod
 

Iomapaseo, so my tongue-in-cheek comments were actually foot-in-mouth! Apologies to RR. Thanks for the correction.

Airfoilmod, to tell the complete tale would require an explanation the industry does not yet have and may not have for years as the research is conducted. At least, that is what this ignorant observer considers likely.

To coin a phrase, 'Better to shut up, if you can't put-up'.

Regards, Tanimbar

Likely
 

Not. The shut up part anyway. I don't buy the "unknown behaviour" bit.
You're welcome to it, to each his own. It is typical of the investigative authority to prolong its work; this is not unknown in government. This may raise howls of protest or a delete, but it is my opinion. M.Mouse suggested that there was knowledge of results given to BA and its pilots. That is fine by me. There is however another group with an investment in the "results" that would preclude "secrecy" from being practiced: Other pilots and the travelling public. When all is said and done, I wager the reluctance of the investigation (ers) will not be taken as having been prudent.

AF

AF, I'm willing to accept the explanation that good knowledge of cold fuel behavior is either not well or widely understood.

I think we always learn in aviation, for example take ditching an airliner. We've recently been reminded (again) that it can be done successfully. But how to do it? Probably only a fairly small number of aviators understood it very well prior to the Hudson River accident, while many aviators didn't think it was possible. So that knowledge existed, but wasn't widely known.

I think it may be similar regarding cold fuel behavior.

Flight Safety
 

With respect, I would point out that ditching is a Pilot issue, Cold Fuel chemistry an engineering one. I have the belief that as a group, pilot's have a superior level of Intelligence and practical experience in their field relative to other less demanding pursuits, for very good reason. However, though a pilot may have a fine knowledge of engineering, it isn't a prerequisite for the certificate.

I have a keen interest in Fuel, my life, passengers and freight depend on quality; this quality is expected, and rightly so. I remain surprised at the less than emphatic response to a Chemical, Engineering, Production, and Quality "vacuum of knowledge".

Training and recurrent training emphasize failure, response, innovation, memory, and solution. Well enough two engines fail on a twin, an ETOPS a/c; on top of a rigorous solution and implementation, the consumers of a life dependent product must be patronised with "the great unknown"?

I don't necessarily believe FAA is doing anything unusual here, but when products are found to be life-threatening, generally the appropriate agency appears to act in a more immediate and appropriate time frame.

All hydrocarbon fuel products are produced to a compromised level of specified quality, not ultimate quality. By the time all jet fuel is synthesised by the identical method worldwide we will probably have pumped the earth dry.

I assume you mean among pilots as a group. There is a tremendous amount of knowledge among experts in the various fields that touch on or specialise on fuels.

Technical and scientific progress hasn't ceased -- far from it. And the discoveries are quite astonishing while at the same time forcing us to lessen our grip on strongly held rules. Physicists can now pause a pulse of light mid-flight!

As previously posited by another poster, it's likely that jet fuel at extreme low temperatures may become a non-newtonian fluid. The time has come for rheologists to study jet fuel at very low temperatures.

Such studies will require not only complex rigs to simulate the requisite conditions, but thousands of evaluations of the myriad possible combinations of jet fuels and additives.

Have a look here for some idea of world jet fuel specs and additives.

Boeing final word /RR-Trents
 

oeing issues warning to 777 operators

A Delta Airlines 777-200ER was flying from Shanghai, China, to Atlanta last
November when its right engine suddenly lost thrust while the plane was
cruising at 39,000 feet over Montana.

The pilots followed flight manual procedures and descended to 31,000 feet,
where the Rolls-Royce engine recovered and responded normally. The flight,
with 15 crew members and 232 passengers, continued to Atlanta and landed
safely.

That incident would likely not have gotten much attention had the same kind
of Boeing jet, with Rolls-Royce engines, not lost all power in both engines
just before landing at London's Heathrow earlier in the year. The British
Airways 777 crash-landed short of the runway. Several passengers were
injured, but none seriously.

Safety experts eventually decided that the British Airways jet, also on a
flight from China, had flown through unusually cold weather at cruise
altitude and ice apparently formed in part of the engine and blocked the
fuel flow.

On Thursday, Boeing sent a notice to all operators of its 777s with Trent
engines made by Rolls-Royce, advising them that it now believes the Delta
and British Airways incidents appear to have been caused by the same thing –
ice blocking the fuel path.

A Boeing spokesman said Tuesday the "all operators" notice contains a series
of precautionary measures that pilots should take during flight to lessen
the chance ice could cause a sudden loss of engine power.

Eventually, the spokesman said, the FAA can be expected to order a
"permanent fix.'' That would likely mean a redesign of part of the Trent 777
engine.

Boeing would not release a copy of the letter it sent last week. The
spokesman said it is not a public document. But the industry magazine Flight
International obtained a copy and said the Boeing letter describes the Delta
and British Airways incidents as likely being caused by "similar factors.''

More than 700 Boeing 777s, a widebody jet that typically carries from 300 to
360 passengers, depending on the model, are in service with airlines around
the world. About 30 percent have Trent engines.

General Electric and Pratt & Whitney also make engines for the 777, but
those have a different design than the Trent engine from Rolls-Royce and are
not thought to be susceptible to the ice problem. The newest 777s built by
Boeing, the best-selling 777-300ER and the ultra-long-range 777-200LR, are
only powered with GE engines.

In September, the Federal Aviation Administration issued a formal
airworthiness directive that required changes in the way ground crews
prepare 777s with Trent engines and how pilots fly them in extreme cold
weather in response to what investigators found in studying the British
Airways crash in January. Shortly before the FAA issued its warning, Boeing
had sent out an "all operators" notice with a series of recommendations
developed to prevent a similar problem on its 777s with Trent engines.

Boeing recommended, for example, that pilots rev their engines when the fuel
temperature falls to 14 degrees Fahrenheit. That would conceivably dislodge
any ice that might be in the fuel line.

Another procedure recommended by Boeing, and ordered by the FAA, called for
the crew to advance the engine throttles to maximum thrust for 10 seconds
before descending on flights that have maintained the same altitude for at
least three hours, if the fuel temperature is below 14 degrees.

Those procedures have been revised in the Boeing bulletin sent last week,
following the Delta incident.

Boeing now recommends that pilots advance engine throttles to maximum thrust
before descending on flights that have maintained the same altitude for two
hours, not three.

Also in its latest notice, Boeing recommends that pilots, during the descent
for landing, reduce engine power to full idle for at least 30 seconds. By
reducing fuel flow, engine oil heat can melt any ice that may have
accumulated.

The FAA, as it did in September, is likely to make Boeing's latest
recommendations mandatory.

The 777 has never had a fatal crash since it entered service with United
Airlines in 1995. But the Delta and British Airways incidents have given
safety experts cause for concern, in large part because they are apparently
dealing with a previously unknown phenomenon.

The British Airways crash occurred Jan. 17, 2008, as the 777-200ER, with 152
passengers and crew members, approached Heathrow after a flight from
Beijing. Both engines failed to respond to autopilot commands for thrust as
the plane approached the airport.

It turned into one of the most puzzling aviation accidents in modern times.
The plane was badly damaged but was mostly intact, so investigators had all
the physical evidence in hand to look for clues. But one thing was missing –
the ice. The key piece of evidence had literally melted away.

Investigators now believe the problem is with the fuel-oil heat exchanger
system on the Trent 777 engine.

Boeing engineers, according to Flight International, have determined by
working in the laboratory that the heat generated by the Rolls-Royce
fuel-oil heat exchanger is not adequate to prevent moisture in the fuel from
freezing. When that happens, ice can form that blocks fuel to the exchanger,
"starving the engines,'' according to the magazine.

The General Electric and Pratt engines on the 777 have a different fuel
system architecture.

"Based on our knowledge of the system configurations, scenario studies and
laboratory test results, we do not believe that immediate action is
necessary or warranted for 777s powered by other engine types or non-777
airframes regardless of engine type,'' the Boeing letter sent to 777
operators last week states, according to Flight International.

Something's missing
 

So the cold fuel transits the system, waits with liquid water in its composition so that it can freeze after entering the pylon and the enhanced heat of the HE? I think that isn't likely. Again, at the temps in the tanks, there would be no liquid water in the fuel. Something Capt. Cargill suggested covers more ground; an upstream "snowstorm" that caused cavitation at the engines. The "snow" (small granular water ice) would have formed as early as in the trucks (A/P tankage) prior to uplift.

Another problem with the Boeing memo as supplied. The assumption is the cavitation was caused by ice blocking proper flow to the HP pumps, if the blockage occurred at the HE does Boeing suggest the Fuel was flowing fine until the ice formed at the exchanger? I suppose the tests are ongoing relative to the FOHE and Boeings fully mocked up system. From the initial response of both engines one could assume that the exchangers were collecting a suspended (preformed) "precipitate" or subjected to the necking down of the exit aperture as ice quickly formed ahead of the exit.

It would be folly for Boeing to target only the RR if it suspected at all that the other engine types were in the least susceptible to the anomaly.
It would be likewise almost unthinkable for Boeing to allow a vulnerability to problems with the fuel to go unreported. This would appear to exonerate the fuel by default, the GE and Pratts as well. Let's not forget that rollbacks occurred well into the long flight, lending some suspicion to a greater concentration of particle ice with time aloft. Also, that on Delta, the rollback appears to have occurred without a demand for increased thrust, as on 038.

AF

Chicken or Egg?
 

Which came first on 038, the rollback or the demand for thrust? :hmm:

Published data seem to indicate both 038 rollbacks came as thrust was already increasing ... but ?

Another question is : Did the Delta fuel pump show signs of cavitation afterward ?

It appears at least AAIB is onto something here and has done extensive testing to identify the problem with the water ice ahead of the FOHE. So now the solution will have to be some sort of a redesign by RR and of course tested and accepted by the correct authorities.

The question goes back to did GE and PW have previous knowledge of problems with ice, just returned the warmer fuel due to convenience of a place to return the fuel, or dumb luck?

Then again I would also wonder if other RR engines are plumbed in the exact manner of engines in question on the T7 and just not exposed to the long periods cold soaked conditions connected to the T7.

VFD

Airfoilmod
 

There are so many errors in what you have written that you clearly havent a clue either about phase-separation chemistry, airport bulk storage or apron hot-hydrant / hydrant servicer systems. If you dont KNOW why dont you just say nothing?

I am still extremely disturbed that people are taking the (relatively unofficial) Boeing statement too seriously.

Any proper solution would need to explain the problem scientifically and (eventually) come up with a new set of rules both for Fuel Specification(s), for pipework/accessories installations and flight planning and operations.

THEN ALL aircraft, no matter what engine, would need to be checked against the new rules.

---------------

Two other things ;

(i) Still three cheers for any useful information.

(ii) Any real explanations for the BA flight having suffered a dual failure so almost simultaneously ?


------------------

Grasping at partial straws is not a solution.

.

Because that is not his modus operandi!

Absolutely agree:ok:

We need to learn and avoid pointing fingers at persons/organizations and stop throwing stones inside a glass house that we are all inside.

Since it's obvious to me that the industry (regulators, engine and airframers )did not know of this combination beforehand it just happend to be a RR installation that first illustrated the weakeness in all our collected ignorance.

Quote :-

......... Since it's obvious to me that the industry (regulators, engine and airframers )did not know of this combination beforehand it just happend to be a RR installation that first illustrated the weakeness in all our collected ignorance.

unquote


I knew someone intimately involved in the Kings Cross fire. There, both before during and after the official enquiry there were masses of misinformed criticism. Most people nowadays will say it was simplistically the combination of wooden treads and build-up of rubbish in the under-escalator area (plus poor emergency procedures).

Actually the main reason was the flash-over effect caused by the layout of the tunnels - something never expected and indeed "new" in terms of underground railway operation. The experts know what happened, the general public just have a simplistic view.

(The final costs of all the remedial works has been vast - and is only now being completed - I have a vague feeling the same might be a case here).

.

Actually there seems just as few facts in that piece as any other.

Still no information on where the "water" for the ice came from.

Still no information on the process whereby the ice formed and acted so regularly on two separate systems

Still no scientific/engineering explanations and new rules to cover ALL aircraft and ALL engine installations.

--------------------------------------

I have copied the piece below ;


Boeing issues warning to 777 operators

Below is a story I just filed, following up on the British Airways crash at Heathrow a year ago.

BY James Wallace
P-I aerospace reporter

A Delta Airlines 777-200ER was flying from Shanghai, China, to Atlanta last November when its right engine suddenly lost thrust while the plane was cruising at 39,000 feet over Montana.

The pilots followed flight manual procedures and descended to 31,000 feet, where the Rolls-Royce engine recovered and responded normally. The flight, with 15 crew members and 232 passengers, continued to Atlanta and landed safely.

That incident would likely not have gotten much attention had the same kind of Boeing jet, with Rolls-Royce engines, not lost all power in both engines just before landing at London's Heathrow earlier in the year. The British Airways 777 crash-landed short of the runway. Several passengers were injured, but none seriously.

Safety experts eventually decided that the British Airways jet, also on a flight from China, had flown through unusually cold weather at cruise altitude and ice apparently formed in part of the engine and blocked the fuel flow.

On Thursday, Boeing sent a notice to all operators of its 777s with Trent engines made by Rolls-Royce, advising them that it now believes the Delta and British Airways incidents appear to have been caused by the same thing – ice blocking the fuel path.

A Boeing spokesman said Tuesday the "all operators" notice contains a series of precautionary measures that pilots should take during flight to lessen the chance ice could cause a sudden loss of engine power.
Eventually, the spokesman said, the FAA can be expected to order a "permanent fix.'' That would likely mean a redesign of part of the Trent 777 engine.

Boeing would not release a copy of the letter it sent last week. The spokesman said it is not a public document. But the industry magazine Flight International obtained a copy and said the Boeing letter describes the Delta and British Airways incidents as likely being caused by "similar factors.''

More than 700 Boeing 777s, a widebody jet that typically carries from 300 to 360 passengers, depending on the model, are in service with airlines around the world. About 30 percent have Trent engines.

General Electric and Pratt & Whitney also make engines for the 777, but those have a different design than the Trent engine from Rolls-Royce and are not thought to be susceptible to the ice problem. The newest 777s built by Boeing, the best-selling 777-300ER and the ultra-long-range 777-200LR, are only powered with GE engines.

In September, the Federal Aviation Administration issued a formal airworthiness directive that required changes in the way ground crews prepare 777s with Trent engines and how pilots fly them in extreme cold weather in response to what investigators found in studying the British Airways crash in January. Shortly before the FAA issued its warning, Boeing had sent out an "all operators" notice with a series of recommendations developed to prevent a similar problem on its 777s with Trent engines.

Boeing recommended, for example, that pilots rev their engines when the fuel temperature falls to 14 degrees Fahrenheit. That would conceivably dislodge any ice that might be in the fuel line.

Another procedure recommended by Boeing, and ordered by the FAA, called for the crew to advance the engine throttles to maximum thrust for 10 seconds before descending on flights that have maintained the same altitude for at least three hours, if the fuel temperature is below 14 degrees.

Those procedures have been revised in the Boeing bulletin sent last week, following the Delta incident.

Boeing now recommends that pilots advance engine throttles to maximum thrust before descending on flights that have maintained the same altitude for two hours, not three.

Also in its latest notice, Boeing recommends that pilots, during the descent for landing, reduce engine power to full idle for at least 30 seconds. By reducing fuel flow, engine oil heat can melt any ice that may have accumulated.

The FAA, as it did in September, is likely to make Boeing's latest recommendations mandatory.

The 777 has never had a fatal crash since it entered service with United Airlines in 1995. But the Delta and British Airways incidents have given safety experts cause for concern, in large part because they are apparently dealing with a previously unknown phenomenon.

The British Airways crash occurred Jan. 17, 2008, as the 777-200ER, with 152 passengers and crew members, approached Heathrow after a flight from Beijing. Both engines failed to respond to autopilot commands for thrust as the plane approached the airport.

It turned into one of the most puzzling aviation accidents in modern times. The plane was badly damaged but was mostly intact, so investigators had all the physical evidence in hand to look for clues. But one thing was missing – the ice. The key piece of evidence had literally melted away.

Investigators now believe the problem is with the fuel-oil heat exchanger system on the Trent 777 engine.

Boeing engineers, according to Flight International, have determined by working in the laboratory that the heat generated by the Rolls-Royce fuel-oil heat exchanger is not adequate to prevent moisture in the fuel from freezing. When that happens, ice can form that blocks fuel to the exchanger, "starving the engines,'' according to the magazine.

The General Electric and Pratt engines on the 777 have a different fuel system architecture.

"Based on our knowledge of the system configurations, scenario studies and laboratory test results, we do not believe that immediate action is necessary or warranted for 777s powered by other engine types or non-777 airframes regardless of engine type,'' the Boeing letter sent to 777 operators last week states, according to Flight International.



============================================

Extract from Boeing MOM issued Thursday 26th Feb:

Rolls-Royce has developed a modification to the FOHE to mitigate the potential for a future fuel system ice accumulation and release event resulting in a restriction at the inlet to the FOHE. Information on the proposed modification is provided via the ref /E/ Rolls-Royce Worldwide Communication (WWC). As noted in ref /E/, the modified FOHE is similar to the existing unit except that the fuel tube inlets are flush mounted to the inlet face plate instead of being proud of the inlet face plate. Testing has demonstrated a significant improvement in the tolerance to the arrival of ice at the inlet face plate in respect of ice quantity and fuel temperature.

Boeing and Rolls-Royce are working with the FAA and EASA to determine the most expedient path to certify the proposed FOHE redesign. Pending certification of the redesigned FOHE, Rolls-Royce is targeting service bulletin release in the third quarter of 2009. Per the ref /E/ WWC, the plan for allocating modified FOHEs is currently being developed and will be communicated with each operator individually once available.

Fascinating -- but it doesn't actually address the process that MIGHT have caused the crash, or where the water came from.

Nor is it a set of rules that applies to ALL aircraft with all types of engine.

Keep these announcements in context.

.

Phil Gollin
 

My 2 cents, as a non engineer type, still relates to fuel and extended periods of very cold and very stable cruise. Both incidents occurred after very long periods of cold soaked and static cruising. All fuel has water in it, the spec allows small amounts. If the a/c tanks fuel prior to launch, it may already contain minute crystalline frozen water, albeit in trace amounts. Dispersed throughout the a/c tanks in some homogeneous mixture, it can certainly collect in small or "restrictive passages" (FOHE).
Built up as a "powdery" rather than a "solid" mass, it may collect in such a manner over time, that it allows cruise thrust, the flow of fuel acting to prevent continued necking down of the constricted passages so affected.
Without being specific due to my limited expertise, I can envision this "snowy" mass preventing higher thrust levels, or, due to additional accretion, maintaining current thrust, causing unresponsive power.

In the case of BA038, sudden full demand may have redistributed this occlusive mass downstream, packed it up and caused cavitation.

For Delta, the plug may simply have shifted on its own.

Anticipating the hue and cry from true believers in ETOPS, it isn't hard to imagine roughly simultaneous faults, given that at periods of long cruise, the systems acclimate and perform as one, essentially, given that there is no discrepancy in design, one from the other. Modern machining, chemistry and refining contributes to non anomalous behaviour of systems.

Then again, the Trent FOHE may melt and allow the ice to refreeze downstream. Over time, (long cruise) this could compromise fuel flow in the traditional way.

Chicken Or Egg?
 

Were the Fuel Oil Heat Exchangers for either GE or RR engines specifically designed to warm the fuel as well as cool the oil or was increasing fuel temperature simply a fortuitous byproduct? (Actually, increased fuel temperature would incrementally improve thermal efficiency.)

How so, got any numbers?

Airfoilmod,

Please don't get me wrong, I like more information. All I worry about is that people MAY be being misled by short-term ideas or solutions. What is needed is a full scientific answer with a proper engineering solution which applies to all aircraft and engine installations.

It may (!) be that only one aircraft/engine installation combination is found to be at risk, but that is so unlikely as to be ridiculous. I just want people looking at the "big picture", not just concentrate on little ones.

.

I regularly operate on the China to Heathrow route and in winter the fuel temp always goes to around -42c sometimes -49c after around 6 hrs of flight.The minimum temp the fuel can drop to is -40c if USA fuel used and -49c for other countries. The engines can be at flight idle for around 20 mins during the descent with temps a lot lower than the fuel would have been on short finals which would have been around -8c or even warmer.
I'm pretty sure if there was any ice present it would have accumalated long before then and most certainly flagged up in the descent.

Engines hesitated due to "core-icing"?
 

Dear fcom,

I have earlier, 2/3, 8/4, 1-5/5 and 3-4/7 (July) 2008, been writing, on this thread, about my theory, that core-icing, due to an ineffective or "turned off" engine anti-ice system, had the engines hesitate, and after "landing" just melt away.

This can also have been the cause in Amsterdam (TK1951)

So have a look, and let me know, if you have had the same thoughts.

Oluf Husted www.whistleblowers.dk

Might this thread, especially the discussion of water from condensation, be relevant to the discussion?

Has a "final" report come out yet on this accident?

Core icing
 

is this for voting or only for expert opinions:confused:

At any rate the answer is No

apparently you don't understand anti-icing systems nor core icing.

However having formed an opinion and your own web site I doubt that you will change your mind seeking only support for your theory.

Phil Gollin
 

On board with that. My feeling all along is that information is being grasped a little too tightly by AAIB. FAA and NTSB operate a little differently. I do not buy the "Unknown characteristics". I think it is a wheeze. As time marches on, the leakage from the authority (not AAIB) has firmed up what Cargill and others were saying from the very beginning.

So it's the Trent? Boeing says so. Commercialism and turf battles have no place vis a vis safety issues. If that's what's happening.

As a reader of this forum I found, with all the due respect, your post absolutely meaningless. If you do not agree with a theory you should explain the reasons why you do not agree.

From that website:

Not on any high-bypass jet engine I've ever operated. Engine anti ice keeps the nacelles ice free but it certainly doesn't route air to to spinner or fan cone nor does it prevent fan blade icing. I suspect this may be but one of many inaccuracies on that site.

Edited to add I've just spotted a complete lack of understanding of the BA LAX-LHR 3 eng flight in there too.

answer=42 - possibly....
 

The thread you quote says the amount of water that can accumulate is quite substantial.

Against - there was a limited time window for it to accumulate after the inspection.
For - water scavenge is of doubtful effectiveness below freezing.

Any accumulated 'water' could all appear at once as the empty centre tank thawed out during the descent, and be scavenged through the still frozen main tanks to be fed to the two 'independent' engine systems as ice 'droplets'.

Oil cooling is a requirement, but the heat exchangers main purpose is to warm the fuel.

Boeing hasn't said exactly that. It is the combination of the Trent engine and the airframe fuel system that will require tweaking. Engineering on both sides obviously missed some low-temperature and possibly fuel quality management gotchas.

40 odd years ago I worked for a DC8-50 operator that experienced ice blockage of the inlet to the Fuel Oil Heat Exchangers on engines 1 and 4 on one particular sector. I don't recall if there were any power reductions as a result but the indicated fuel pressure on 1 and 4 used to drop late in the 9.5 hr flight. Investigation revealed impact icing on the fuel inlet end of the heat exchanger core. Part of the problem was the fuel loaded at HNL contained too much water as the tank farm capacity back then did not allow sufficient settling time before use. Engines 1 and 4 only were affected because the coldest fuel was in tanks 1 and 4 toward the end of the sector.
The fix was to reverse the oil flow through the FOHE. The original design had the hot oil entering at the fuel exit end and the cooled oil exiting at the fuel inlet which I recall was supposed to be the more thermally efficient flow but by reversing the flow the hot oil went into the fuel inlet end of the core and stopped the ice from building up on the FOHE core.

CV880

That should sort the problem out for little more than a couple of dollars:)

Engine core icing
 

I have to agree with lomapaseo , you are confusing nacelle icing with engine core icing , two completely different things . As for your website , at least try to get your facts right before trying to impress a group of professionals on a forum !!

Besides , how on earth does engine core icing explain the HP fuel pump cavitation exhibited by both engines ??