Phil Gollin

You ask how so similar a thing can occur in two separate places but with a time difference between them.

I have to say that I can't see that there is much difference in reality, six or seven seconds can be accounted for by a slightly different amount of ice (in some form) being present and the 'detaching' behaviour of that accumulated ice by the slightly different fuel flows noted in each engine.

Since this is the only case ever seen of this nature, there are no statistics with which to determine whether the similarity seen is a coincidence or not.

Let's face it, it has been shown that ice is the only remaining possibility, and how else can such a restriction occur other than that some form of solidified ice arrives at a constricted area in high concentration, overwhelming the ability of the fluid part of the flow to pass at sufficient rate.

The presence of a quantity of water in the tanks has been determined. Whilst it would appear to have been small is there any possibility that the location of the water (or ice at that stage) could have become focused/concentrated in one or two particular areas and then gone through to the engines as a slug?

I appreciate that the volume of water present does not appear to have been sufficient to cause the problems experienced.

Could it have been underestimated? Could it have been in the wrong place at the wrong time?

Jim

Actually according to some "not-easy-to-dismiss" sources, had the autopilot been disconnected immediately, and the A/C flown in "longest glide" mode, it would have (barely) made to the runway, and landed almost normally.

If you're curious, read the thread with a title like "BA038 pilots given a medal" or something like that.

Another thing that can surprise you, is that there is no training for "dead stick" landings (dual engine failure), in any airline of the world.

All in all, the positive outcome of this incident is due to sheer luck. Sorry if this lessens your trust in the safeness of flying.

Jim,
Almost certainly in the wrong place at the wrong time...and yes, the drift seems to be with such a small quantity of water, that it perhaps layered or was picked up all at once due to the change in attitude during the latter stages of approach.

It's interesting to note that one of the recommended changes in operational procedures may be to vary throttle settings more before or during descent (the implication being I think, so to stir up or purge wtaer/ice near the scavenge pumps)

A question I put on one of the early pages of this thread was along the lines ofThe answers to that were along the lines of... 'Yes, quite possible, and there has even been a move towards that situation due to approach profile that specifically encourage it' (fuel usage and noise abatement I believe)

[please clarify or correct if you feel this is wildly inaccurate, I haven't re-scanned those responses as yet]

And they may well have taken a couple of roofs and the aiport fence with them too - not to mention the need to take action within seconds when the nature of the problem is unclear.

Apart from the "not-easy-to-dismiss" sources bit !
I'd say that statement is very easy to make in retrospect, from one's armchair, very, very easy and even then maybe not so accurate, unless immediate means immediately the engines didn't pick up i.e. how does one know they aren't about to pick-up when they have for every flight one has ever flown before, how long does one wait for an uncertain event... there is little if any training for 'engines not picking up after throttle re-adjustment 720' agl runway ahead' , surely?

Yes, there was luck, and there was also some correct and non-panicky actions taken on the fight deck that ensured BA038 just got over the peri-fence and flared heavily enough with what remaining airspeed it had such that vertical speed at touch-down was low enough to prevent a complete break-up - as we know from Madrid, almost always resulting in fire and fatalaties.

However, I would like to add that I think parading the pilots in front of the press the next day was in extreemly poor taste and judgement... whoever planned that should be fired, they both looked horrified at having to endure that!

el #
 

Maybe not, but there have been instances before where all power has been lost and crew have "controlled" the AC. i.e. a BA 747 SIN to PER when it encountered volcanic ash over Indonesia and lost all 4 engines. They did manage to re-start them before their collision with the planet.
I think that all PF would have innate ability to naturally react to flight needs - as in this case where it was reported that PF lowered the nose to stop the stick-shaker.

Flynerd

I did not want to stir debate again on the matter of how the lading should have been flow, not having even a tiny bit of the necessary competence on the matter. I also recognize that anything said now is purely retrospective.

I just wanted to inform nhs that there are different opinions on the matter, so he/she can look in the relevant thread and form an informed opinion from there.

However rib4t4, on the subject of "need to take action within seconds", well that is exactly what the crew didn't do, at least regarding the autopolit/autolanding, that was left engaged for the last critical seconds of the landing.

Again, I don't know if the a/c would have taken roofs or fallen from the sky if flown manually. What I know is that some real pilot did a real sim test and it seems like a normal landing could have been completed. Do wath you want with this notion, and if you think that in these dramatic seconds the Cap.n came the conclusion that A/P would have landed acceptably despite virtually no thrust, and consciously left it engaged instead of taking control, that's OK with me.

Finally be assured that I do not have any agenda or position to defend, and be assured this is my 2nd and last post in this thread.

Can´t be too expensive, since everything in NATO from tent stoves, jeeps and tanks to fighter aircraft run on the stuff. (F-34 / JP-8)

And civ a/c too come to think of it.....

Power Was Added In The Holding Pattern
 

The AAIB report says power was increased upon entering holding. It even specifies the fuel flow rates at that time.

Hatton Cross. Details of a close call with surroundings.
 

For those not familiar with LHR ( Hatton Cross tube station area). A little local geography expanding on the the BBC map of the area.
The BBC showed a car hire depot but not the filling station next door.
Sadly a BP petrol (gas) station seems more newsworthy.
The busy A30 4 lane major road is only a fence from the perimeter road.
The Green Man pub ( the noisiest pub in the world near a civil airport ?) is also one of the roofs that had a near miss.

A view from Hatton Cross underground station across the A30
with a normal approach of a SQ 747 shows how close the 777 was from an even worse event.

http://farm1.static.flickr.com/50/13...1ff0d30d0.jpg?

http://farm1.static.flickr.com/50/13...g?v=1158408144



A view from the other side of the station
The peri track is past the green traffic lights.
Just and only just to the right of the traffic lights is the landing location.

http://www.oxford-chiltern-bus-page....A340-buses.jpg
http://www.oxford-chiltern-bus-page....A340-buses.jpg

I disagree. A certain 737 operator did train for that event. If I remember correctly the number was outbound over the marker at 5000 above FE, complete normal PT and return for landing. It worked in the SIM!

Feathers ;

I have to say that I can't see that there is much difference in reality, six or seven seconds can be accounted for by a slightly different amount of ice (in some form) being present and the 'detaching' behaviour of that accumulated ice by the slightly different fuel flows noted in each engine. .........

......... Let's face it, it has been shown that ice is the only remaining possibility, and how else can such a restriction occur other than that some form of solidified ice arrives at a constricted area in high concentration, overwhelming the ability of the fluid part of the flow to pass at sufficient rate.


But this is like having your cake and eating it.

The engines had their commands at the same time, but the roll-backs occured at slightly different times, HOWEVER the effect on final thrust was almost exactly the same.

You say "ice is the only remaining possibility" - but this is what annoys me. They can only reproduce one aspect (the cavitation damage) but without any real expalantion (the two icing scenarios are not really supported by the report) so grasp that one straw. If they could reproduce the icing that leads to the cavitation damage AND show that that icing condition can be variable in time but not effect - THEN they would have something that would convince me.

Don't get me too wrong, as a cautious warning (as opposed to a "finding") I would be happy, but fail to see why this mysterious icing wouldn't affect 777s powered by other types of engines.

.

TREE

my airline also did some dual/all engine flameout landings in the sim.

I think that we could all benefit by this training.

Deadstick training?
 

Dual Engine failure "dead stick " not taught anywhere in the world?

Not so.

Dual Engine failure has been trained on each conversion I've had since about 1999, (two different airlines).

el #

Not correct. A large British Airline based at LHR includes total engine failure landing training in at least one of its current two engined fleet types.

What are you basing your statement on??

How long would it take to recognise this was an engine problem rather than an autopilot/ILS problem? Did I hear an early TV report that GA was called or am I mistaken?. They were still running and they had been cycling to maintain GS - it may not have looked like an engine failure for some moments?

Excellent report...

but I don't understand the apparent lack of logic between the prudent requirement for..."interim measures for the Boeing 777, powered by Rolls Royce Trent 800 engines" but only a recommendation that the authorities consider the implication to other engined 777's and aircraft in general.

Maybe they didn't want to get into commercial politics and passed the buck.

Since the specific mechanism is not understood I would have expected whatever interim action is taken on Trent engines to also apply to GE.

How much more efficient are the Trents?
To what extent does this reduce fuel flow in terms of cross sectional pipework terms? Significant?
The two Trent engines were exhibiting different (measured at least) fuel rates anyway!

My interpretation of the report is that the blockage was due to ice in the fuel delivery system prior to the engine unique part of the installation.

My conclusion would have been to consider both engines types equally subject to whatever caused the restriction at least until the exact mechanism is understood.

Comments?

<Phil Gollin>
Feathers ;

I have to say that I can't see that there is much difference in reality, six or seven seconds can be accounted for by a slightly different amount of ice (in some form) being present and the 'detaching' behaviour of that accumulated ice by the slightly different fuel flows noted in each engine. .........

......... Let's face it, it has been shown that ice is the only remaining possibility, and how else can such a restriction occur other than that some form of solidified ice arrives at a constricted area in high concentration, overwhelming the ability of the fluid part of the flow to pass at sufficient rate.


But this is like having your cake and eating it.

The engines had their commands at the same time, but the roll-backs occured at slightly different times, HOWEVER the effect on final thrust was almost exactly the same.
</Phil Gollin>

I like cake!

On the assumption that a similar ice/fuel mixture was present, then the fuel flow that could pass the obstruction would be limited by the consistency of the ice and the throat area it is trying to pass. This will be the same in both engines (although perhaps there is a 'handedness' to the fuel piping, I do not know).

<Phil Gollin>
You say "ice is the only remaining possibility" - but this is what annoys me. They can only reproduce one aspect (the cavitation damage) but without any real expalantion (the two icing scenarios are not really supported by the report) so grasp that one straw. If they could reproduce the icing that leads to the cavitation damage AND show that that icing condition can be variable in time but not effect - THEN they would have something that would convince me.

Don't get me too wrong, as a cautious warning (as opposed to a "finding") I would be happy, but fail to see why this mysterious icing wouldn't affect 777s powered by other types of engines.
</Phil Gollin>

Well, the latter statement is quite correct, and you will see that AAIB are saying that an urgent investigation into precisely that condition is needed, it clearly isn't just a Trent issue it's just that the one instance so far happened to be on a Trent-powered airframe.

As for the reproducibility, yes, so far they have shown that a problem is seen in circumstances not that alike to the real fuel system. More work is to be carried out to improve the test to mimic reality better. They may not succeed, but they have to try.

The ultimate mimic though would be a 12 hour flight from China in similar TAT conditions and flight profile with the same approach clearances, descent rates, power profiles. If they are lucky they get to see it happen again, but maybe this time with a 777 embedded in Hatton Cross tube station.

The other thing to note, they state quite clearly that very little is known about the precise effects of ice in fuel under varying circumstances. So a major research task would be called for to understand it better, that will take time.

Do you feel that it wasn't ice? Because there surely are precious few other culprits lurking.

Apparantly you airline types have been using the wrong technique for landing. In todays Daily Telegraph their esteemed Jorno David Millward - Transport Editor suggests that you use "Reverse Thrust"to slow the aircraft for landing. And there was me thinking it was a balance of thrust vs drag from flaps !!!. It any of you chaps would like to try this new technique, I will keep an eye on Sky News to see the results. I know that the Concorde could do this, on the inboard Olympus engines, but dont try this at home chaps

Front page top of far right column

There seems to be an assumption that the effective temperature within the wings is reasonably uniform and similar to or above the TAT.
Is this correct ? Are there no cold spots resulting from different aerodynamic conditions ?

Tree and others, I didn't knew about the fact that such situations are actually practiced in certain companies and apologize for having said that is not so.

My information was based on the fact that in many many cases I've read on pprune that because is considered "negative training", dual engine failure is not part of the training. It's great news that not everyone thinks that way and thank you for correcting me.

Amount of water in the fueltanks on BA038
 

I have just read the latest report - interesting reading and thorough work, but many questions remain.

According the report (page 12): the estimated amount of water in the tanks at departure from PEK was max. 5 liters plus maybe some water left from the flight to PEK, but the aircraft was sumped before departure and on the day before, so I suppose that it will be safe to assume that the amount was rather small. (?)
The A/C had almost 100 000 liters of fuel at departure from PEK - and the 5 liters of water "was evenly spread throughout the fuel".

How could this extremely small amount of water have produced severe problems on just this flight and not on thousands of other flights in the past - the actual temperatures along the route were low, but not unusually low?

Which factor(s) made this flight so special? The report mentions some - but again 5 liters of water!?

I am looking forward to the final report.

I admire the crew for their excellent A/C handling.

El #

You say "What I know is that some real pilot did a real sim test and it seems like a normal landing could have been completed."

Well I personally know a real pilot who did a real test on a B777 full motion category A simulator. There is no way a normal landing could be made, ie reaching the runway.

Although many pilots practice total engine failures it is usually at a height that allows a glide approach to a runway. The BA038 was fully established on the ILS with flap 30 set. Airlines do not practice total engine failures at that stage as it is negative training as the plane will inevitably land short, ie crash. El # The pilots have been exonerated of blame in the latest AIB report. Please do not infer otherwise. Please accept the facts that it was impossible to reach the runway with the power available. A manual landing was achieved in which all the passengers survived.

If you want more pontification by people who think they know everything, check this thread out:

Comments on ?Ice in fuel caused Heathrow 777 crash? | The Register

Conspiracy theories are being spouted about now... :-)

S.

Feathers :

I like cake!

On the assumption that a similar ice/fuel mixture was present, then the fuel flow that could pass the obstruction would be limited by the consistency of the ice and the throat area it is trying to pass. This will be the same in both engines (although perhaps there is a 'handedness' to the fuel piping, I do not know).

Not as much as me (I) !

The reproduceable result (IF I have read correctly) was a 95% reduction in the area before the valve. Somehow this occured in two separate systems at different times, but to the same effect. Somehow the UNKNOWN ice phenonomen managed to be dissimilar in the two systems enough to affect the valves at slightly different times, but to near-enough the same extent. (N.B. there is a possibility NOT NOTED IN THE REPORT that the 95% figure has a large margin of error - but ??????)

Still dissatisfied.



Well, the latter statement is quite correct, and you will see that AAIB are saying that an urgent investigation into precisely that condition is needed, it clearly isn't just a Trent issue it's just that the one instance so far happened to be on a Trent-powered airframe.

As for the reproducibility, yes, so far they have shown that a problem is seen in circumstances not that alike to the real fuel system. More work is to be carried out to improve the test to mimic reality better. They may not succeed, but they have to try.

The ultimate mimic though would be a 12 hour flight from China in similar TAT conditions and flight profile with the same approach clearances, descent rates, power profiles. If they are lucky they get to see it happen again, but maybe this time with a 777 embedded in Hatton Cross tube station.

The other thing to note, they state quite clearly that very little is known about the precise effects of ice in fuel under varying circumstances. So a major research task would be called for to understand it better, that will take time.

Do you feel that it wasn't ice? Because there surely are precious few other culprits lurking.


I still see no reason why ALL 777s aren't affected by the AAIB report.

I am dissatisfied because the report is NOT stating anything firm (both icing scenarios proposed are left dangling) - they are merely grasping the reproduceability of the 95% blockage causing cavitation. They have got a "one" and a "one" and made "ten" because the other eight parts of the puzzle are still to be found.

.

Difference in rollback times
 

The AAIB report records, but does not comment on, that the fuel flows to the left engine were generally lower than those to the right engine, whilst the EPR of the right engine reduced first and to a value slightly higher than that of the left engine.

If, as is hinted, the engines (or rather some of their pumps) were separately sucking fuel from the pipework downstream of blockages at similar points in the two sets of pipework, it seems reasonable that the less thirsty engine could run for a few seconds longer. The extra pipework leading to the APU could possibly give the left side system a little more volume to suck from - but this would depend on the position of the constriction.

However, whilst possibly explaining the time difference between the rollbacks, I might expect that with similar restrictions the less thirsty engine might develop the larger, rather than smaller, EPR.

On a different theme, a couple of questions that physical chemists may be able to answer with a definite NO: does the presence of dissolved water alter the increase the temperature at which some waxing compoents solidify; and do the variations in composition of the Chinese fuel from normal Jet A1 modify the response to the previous question?

And finally: would it not be possible to provide the QAR with enough battery or even capacitor backup energy to enable it to write the volatile memory to non-volatile memory on failure of external power?

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

A more detailed reading of the AAIB interim report leads me to the following conclusions:
1) The AAIB strongly suspects that an unknown (or possibly forgotten - reference the mentioning of B52 operations) fuel condition led to a blockage (partial) in the fuel delivery system.
2) The AAIB does not understand the details of how the blockage occurred.
3) The AAIB does not think any other organisation has a current understanding of how very cold fuel behaves.
4) The AAIB strongly suspects that aircraft type, operator, manufacturer (airframe and engines) are irrelevant to the root cause of this accident, i.e. the accident could, and may, happen to any aircraft using that fuel type in similar operating conditions.
5) Given point 4 then this incident is extremely important to the industry, not only for those now manufacturing or operating, but also for the future design and operation of aircraft. Put another way, this incident, and the avoidance of recurrence, will be very expensive.

There seems a strong possibility that a rigorous research programme will be initiated, probably involving multiple organisations not directly related to commercial concerns, to study very cold fuel.

I wouldn't be surprised if a flying test rig was involved maybe operated by an outfit like NASA.

Following on from the AAIB reference to B-52s and FSII, I wonder if some poor souls are not already deep into the RAF and USAF/SAC archive records looking for those papers that covered their 1950-60s tests on cold weather flying.

What has been written, and the quick response from the NTSB, suggests that the AAIB has already had detailed discussions with all the interested parties, that there is common agreement on interim measures and, hopefully, agreement on a research programme to find the eventual cause. The final AAIB report is years away.

I still think the fuel within the main tanks stratified in some form and that a pulse of "gloop" entered the delivery systems and partially blocked them.

But, I'm intrigued by the some of the hints in the AAIB's report about low maximum fuel flow rates from the main tanks and two flights in very cold circumstances separated by a cold stop in Beijing. Are the AAIB thinking that ice built up over two flights in the fuel lines/systems emanating from the main tanks and that a new operating procedure of some kind should be considered to 'purge' the lines under similar circumstances? Time will tell.

Regards, Tanimbar

'Which factor(s) made this flight so special?'
 

Doesn't the answer come from page 17?:

Analysis of fuel flow from the 13,000 flights shows that 10% had fuel flows less than 10,000 pph during step climbs (the accident flight did not exceed 8,896 pph), and 10% had had fuel flows greater than 10,000 pph during the approach phase (the accident flight was greater than 12,000 pph). Although these were not unique, they were at the edge of family for the data analysed. However, when analysed in conjunction with the fuel temperature data above, all of these factors make this flight unusual within the 13,000 flights analysed.

Maybe we should infer that the absence of high fuel flows in the cruise (gentle cruise climbs) promotes ice formation while the high flow on descent encourages any slug that has formed to move; take away either and you break the chain. Since, as others have said, it isn't obvious that there is anything special about the RR engine in all this, maybe this analysis will be continued to the other 128000 PW and GE powered 777 flights. If BA38 is still ' unusual' in the bigger data set, that would be more than interesting.

No comment on the probable cause, but the proposed revised operating procedures remind of my Tiger Moth days (1961); "when descending with throttle closed, regularly open throttle to rev engine". Trouble is, you guys no longer train on Tigers. :ok:

Sun in my eyes 176p.

Sir,

(i) Disagreed, if you read the whole thread and like many others I have, there are current 777 pilots out there and for whom I have great respect having read their postings over time, who claim to have made it to the runway in the sim using the data as published.

(ii) Agreed, this interim report confirms magnificent, intuitive and effective flying by the pilots in "less than a minute". Although we need to wait for the final report, this report should at least now stop any poisonous whispers to the contrary.

(iii) For the record I have been proven wrong by this report as I have speculated here that it was low Molecular Mass fuel components (hydrocarbon or the friends of ethoxy ethane as addditives) that caused the HP pump cavitation.

I have unequivocal respect for the AAIB and I need to think through the water ice explanation at the ppm level in fuel that is within spec.

The magic bullet flying oxygen cylinder retracing its steps as it exited the Quantas 747 and now this, reminds me not only to respect those slices of cheese but to show a little more humility.

CW

Tanimbar:

Having read the report twice now I concur with your analysis and in particular I'm drawn to the last conclusion. Ice accretion inside the wing fuel pipes over the two flights separating when the high fuel flow was demanded and causing the restriction. Where the restriction is is not clear but the face of the FOHE looks like a good bet.
They say that formation of the ice there was unlikely but don't comment on this being the collection point for ice formed upstream.
I'm sure we will see requirements for fuel feed line purging by high thrust demands coming to an AFM near you pretty soon.

I think the previous posts questioning the temperatures reached within the pylon pipework may be significant.

In the refining and petro-chem industries, pipework which is subject to icing, waxing or similar problems is often trace heated. This is usually by steam or electrical heaters, but I guess a warm air bleed would also work.

Does anyone know if anything similar has ever been applied in aviation.

occasional,
From the latest Interim report:
One of the difficult to find and, I think, generically interesting pieces of information to emerge from this investigation.

Dont think thats new, its been in the manuals for as long as i can remember.

No simulator has true airplane fidelity.

No simulator has true airport environs and runway fidelity.

It's not an argument. Just a statement of fact. :ooh:

Try try and try again?
 

It would be interesting to hear whether they reached past the grass on the
first attempt, or after a few tries.

Given the available energy, I find it hard to believe a crew being able to
make it to the concrete. However, details of how different strategies played
out might be interesting. I don't remember reading such a post.

If they set up the sim just to try BA038, then they were in a much better
position than the real crew: they knew the exact problem to expect, had
seen the true outcome, and no lives were on the line. A true test would be to
spring BA038 rollback on crews when their configuration and energy
matched in the simulator, and see how they did first time, building up
data slowly.

For what my view's worth: getting BA038 over the fence, stopped
and evacuated with only a single serious injury onboard and none on the
ground - for real - deserves much respect.

Training & Value
 

El #

From posts since mine your claim from "not-easy-to-dismiss" sources" appears to have been dismissed.
And please don't be so dismissive of me. I have read all post & also the one you suggested.

Your statement re: dead stick landings also appears to be incorrect. "sheer luck" Well I dont think so. Ok I'm just SLF but my view was reflected by suninmyeyes in post 1765.

My trust in flying has not been decreased by this, in fact has been increased. I trust the people I fly with. I also trust the AAIB to get to the bottom of this no matter however much speculation there might be on this site.

My bottom line was reflected by suninmyeyes. "A manual landing was achieved in which all the passengers survived" For that I thank & respect the crew. I'd rather have been on BA038 than the Madrid flight.

Post #121 in this thread answers your question.

http://www.pprune.org/rumours-news/3...ml#post4322326