BA038 (B777) Thread
According to the last report, FF maintained for the last 40 sec was twice that amount for each engine, which must not be far from a typical FF in order to maintain the G/S and cross the threshold at 50ft ?
With F30 in calm conditions, you're going to need about 1.05-1.06EPR (c.50-55%N1) to maintain a 3deg slope, fully configured at Vref30+5, at the approximate landing weight we're talking about. The engines at the time were producing 1.02-1.03EPR from the AAIB report.
Things improve a bit with F25, needing 1.03-1.04EPR (45-50%N1), so pretty close, which is why moving to F25 might have helped. If the failure had occurred when the flaps were at 20 or less, the residual thrust would have been in the ballpark for maintaining a 3deg slope, gear down. That wasn't what happened, though.
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Thanks for the helpful data FullWings.
I don’t want to sound picky, but to me, looking at the graph, the engines at the time were producing more like 1.03-1.04EPR, which is a bit closer to the desirable request.
Anyway, the point is there was still some valuable produced thrust, knowing that the FF reduced only 8000 feet before the threshold, I am surprised BA38 touched down at the end of the rope a full 2000 feet before the usual touchdown point ?
In no way this is a critic to the crew, but keeping the Vref would have been a better option than keeping the Glide Slope.
As we have seen again in CIA this week, dual engine malfunction (?) in final DO happen.
It would be time to implement such exercise in sim training, not to cover all possibilities but just to make aware of different options and consequences.
As always, let’s learn from the unlucky one.
I don’t want to sound picky, but to me, looking at the graph, the engines at the time were producing more like 1.03-1.04EPR, which is a bit closer to the desirable request.
Anyway, the point is there was still some valuable produced thrust, knowing that the FF reduced only 8000 feet before the threshold, I am surprised BA38 touched down at the end of the rope a full 2000 feet before the usual touchdown point ?
In no way this is a critic to the crew, but keeping the Vref would have been a better option than keeping the Glide Slope.
As we have seen again in CIA this week, dual engine malfunction (?) in final DO happen.
It would be time to implement such exercise in sim training, not to cover all possibilities but just to make aware of different options and consequences.
As always, let’s learn from the unlucky one.
Hi CONF iture,
I took the EPR levels from page 2 of the most recent AAIB Interim Report, where it states: "...at a height of about 720ft the thrust of the right engine reduced to approximately 1.03 EPR (Engine Pressure Ratio); some seven seconds later the thrust on the left engine reduced to approximately 1.02 EPR" and further on in the same paragraph: "...The FMVs responded to this command and opened fully but with no appreciable change in the fuel flow to either engine."
An interesting hypothesis. F30 on the 777 is the most you can hang out, i.e. it is drag flap with little corresponding increase in lift compared with F25. I would put forward that Vref30+5 is, with *significant* thrust being produced, quite a bit faster than Vx in this situation. Maintaining speed at 'bug' (1.3Vs+5) with F30 would lead to intersecting the ground plane some distance short: not a real improvement on what happened. There is the possibility of some help from ground effect but a) it's not over flat terrain and b) the aircraft is in its 'dirtiest' config. and bleeding energy fast. I don't think we'll ever know for sure what the optimal course of action might have been, unless someone runs some *very* detailed computer analyses (NOT in a simulator). I have a hunch that the answer will be different for each second that goes by on the approach.
I've done total engine failures as part of conversion/recurrent training on several types, including the 777. However, the situations have been (deliberately) set up to be 'survivable', i.e. a more than evens chance of getting the thing down on the runway in one piece, given average skill levels. The BA38 (and possibly the recent RYR) were both at the edge of the envelope and to try and train for rare incidents like these would probably leave the impression that in real life you'd be lucky if you weren't dead. A bit negative, not to mention the best recovery techniques are probably peculiar to each incident, so there is little 'generic' help to take away with you...
I took the EPR levels from page 2 of the most recent AAIB Interim Report, where it states: "...at a height of about 720ft the thrust of the right engine reduced to approximately 1.03 EPR (Engine Pressure Ratio); some seven seconds later the thrust on the left engine reduced to approximately 1.02 EPR" and further on in the same paragraph: "...The FMVs responded to this command and opened fully but with no appreciable change in the fuel flow to either engine."
...keeping the Vref would have been a better option than keeping the Glide Slope.
It would be time to implement such exercise in sim training, not to cover all possibilities but just to make aware of different options and consequences.
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Phil gollin,
....and something that 2 of the 3 AAIB Safety Recommendations addressed. Concerning the semantics, "theory" seems appropriate as defined by the OED. On your comment about there being insufficient water to form ice, isn't that what I said?
Rgds
[I think calling the AAIB suggestion a "theory" is a little bit too optimistic - they do not think there was enough water to form sufficient ice, and can't model a reasonable event to cause damage.
I think it is merely something they are investigating.
I think it is merely something they are investigating.
Rgds
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Pettifogger
A "theory" which fails to have the correct circumstances for it to be valid and also which cannot be even commenced to be tested is not a valid "theory".
.
A "theory" which fails to have the correct circumstances for it to be valid and also which cannot be even commenced to be tested is not a valid "theory".
.
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not enough water.... post 2056 Phil Golin
Phil to reply to your assertion about not enough water content strikes me as "denial" ,The Met physistists swore there wasnt enough water at 25000ft to cause a Viscount complete 4 engine shut down over the Alps in1958. Their figures were out by an enormous factor , something like100/1. So we had to modify all Bristol Proteus engines as a result.
Heavy ice built up in the Ubend very rapidly,then came away in a rush
Heavy ice built up in the Ubend very rapidly,then came away in a rush
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Phil gollin, re your post #2066, sorry to get picky or even pettifogging about this, but according to the compact OED, a theory is a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained. 2 an idea accounting for or justifying something.
http://www.askoxford.com/concise_oed/theory?view=uk,
or if you prefer Chambers ED "an explanation or system of anything: an exposition of abstract principles: speculation as opposed to practice". (sorry, no linked source for this one)
Or the Merriam-Webster dictionary "6 a: a hypothesis assumed for the sake of argument or investigation b: an unproved assumption". This one seems particularly fitting, wouldn't you say? theory - Definition from the Merriam-Webster Online Dictionary
Sorry to be irritating and quote dictionary definitions, but "theory" as described above is what I meant to say, and it seems to me to be entirely appropriate at this stage of the investigation. If you or others think not, or disagree with some aspect of the AAIB's Interim Report and Safety Recommendations, I shall respect their views, but without seeing convincing arguments (or sources in the case of further 'definitions' of 'theory'), would be unlikely to agree with them. For the present, I prefer to stick with the AAIB's avenue of investigation, particularly the yet to be seen assessment of the fluid dynamics modelling, something which I alluded to much earlier, around post #500, I think.
rgds pf
http://www.askoxford.com/concise_oed/theory?view=uk,
or if you prefer Chambers ED "an explanation or system of anything: an exposition of abstract principles: speculation as opposed to practice". (sorry, no linked source for this one)
Or the Merriam-Webster dictionary "6 a: a hypothesis assumed for the sake of argument or investigation b: an unproved assumption". This one seems particularly fitting, wouldn't you say? theory - Definition from the Merriam-Webster Online Dictionary
Sorry to be irritating and quote dictionary definitions, but "theory" as described above is what I meant to say, and it seems to me to be entirely appropriate at this stage of the investigation. If you or others think not, or disagree with some aspect of the AAIB's Interim Report and Safety Recommendations, I shall respect their views, but without seeing convincing arguments (or sources in the case of further 'definitions' of 'theory'), would be unlikely to agree with them. For the present, I prefer to stick with the AAIB's avenue of investigation, particularly the yet to be seen assessment of the fluid dynamics modelling, something which I alluded to much earlier, around post #500, I think.
rgds pf
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This is a waste of time.
It is a hypothesis - as in "IF there were more water, then ......."
It cannot be a real "theory" as it doesn't have the right conditions to start with.
.
It is a hypothesis - as in "IF there were more water, then ......."
It cannot be a real "theory" as it doesn't have the right conditions to start with.
.
Usual disclaimers apply!
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Nobody appears to have a definitive answer. That is the AAIB, Boeing, etc,etc. As has already been published the complete fuel manifolding, valves etc had been removed from one wing and reassembled into a test rig. Now (in the last week!) the complete manifolding from the other tank has been removed to make up the complete a/c assembly to see if that makes any difference to the test results.
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@ wilyflier,
Not to be nit-picking, to my knowledge the Bristol Proteus was indeed prone to icing but was married to the Britannia, not the Viscount. The Viscount had RR Darts.
@gas path,
With regards to "the other tank", that does not mean only the other main tank but I assume that also includes the fuel lines and override jettison pumps from the center tank?
Green-dot
The Met physistists swore there wasnt enough water at 25000ft to cause a Viscount complete 4 engine shut down over the Alps in1958. Their figures were out by an enormous factor , something like100/1. So we had to modify all Bristol Proteus engines as a result.
Not to be nit-picking, to my knowledge the Bristol Proteus was indeed prone to icing but was married to the Britannia, not the Viscount. The Viscount had RR Darts.
@gas path,
Now (in the last week!) the complete manifolding from the other tank has been removed to make up the complete a/c assembly to see if that makes any difference to the test results.
Green-dot
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With regards to "the other tank", that does not mean only the other main tank but I assume that also includes the fuel lines and override jettison pumps from the center tank?
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Venturi works for liquids too
Green dot post 2071
We all know the difference Viscount /Brit and Dart/Proteus but both engines were reverse (air)flow
The Viscount event was a wake up call.
My statement pointed out that the pundits figures on the water content conditions everyone accepted as normal were wildly wrong and so design changes were made across the industry.Reverse flow was avoided in new engine designs.Existing designs were modified to de- ice the bends.SOPs were issued to avoid icing conditions
It may be a bit fanciful but are we coming to the idea that liquids and gasses have similarities in flow behaviour round convoluted ducting and that ice accretion occurs in pipe lines carrying wet fuel similar to impact icing on wings and such? .New stricter parameters for dynamic fuel-icing avoidance?
We all know the difference Viscount /Brit and Dart/Proteus but both engines were reverse (air)flow
The Viscount event was a wake up call.
My statement pointed out that the pundits figures on the water content conditions everyone accepted as normal were wildly wrong and so design changes were made across the industry.Reverse flow was avoided in new engine designs.Existing designs were modified to de- ice the bends.SOPs were issued to avoid icing conditions
It may be a bit fanciful but are we coming to the idea that liquids and gasses have similarities in flow behaviour round convoluted ducting and that ice accretion occurs in pipe lines carrying wet fuel similar to impact icing on wings and such? .New stricter parameters for dynamic fuel-icing avoidance?
wilyflier:
"We all know the difference Viscount/Brit and Dart/Proteus but both engines were reverse (air) flow".
In words of one syllable (or maybe two) - boll*cks.
The Proteus as fitted to the Britannia was indeed a reverse flow engine but the RR Dart was most certainly not.
For those of you who are unfamiliar with reverse flow turbo prop engines, here comes a simple explanation.
The only reason to have a reverse flow engine is to reduce the length of the engine and make it more compact (like the PT-6). So, the airflow enters the intake behind the prop and then goes through a 180 degree bend before entering the compressor. Then it goes through another 180 degrees before the combustion stage and then exiting through the turbine stage.
On the Britannia, the Proteus engines used to ice-up badly on the first U-bend and this caused the aircraft to be years and years late on entering service.
Even then, the problem was never satisfactorily solved. The civilian Brits had heating skins (B skins) fitted but their use caused a 10% loss in thrust. Even then, the engines were for ever shutting down and restarting (called "bumping") in icing conditions and this ensured that the crew never were allowed to go to sleep.
The RAF had a cowl heat system fitted but this resulted (so I'm told) in a 25% loss in thrust every time the system was used.
I will now move on to the RR Dart; I flew the Argosy for ten years and also the Viscount 802/806.
The Dart was a conventional engine in that there was no reversal of flow. It simply went: compression stage, combustion stage and then turbine stage. That is why the Dart was such a long and slim engine.
In fact, the engine was developed in a very simple fashion. When the Da 6 was not powerful enough, compression and turbine stages were added and so it was that the cowlings got longer right up to the Da 10.
I have never heard of four Darts failing at once through icing. I have personally had four inches of jagged ice on the engine intakes after an engine antice fault and not one of them even murmured.
"We all know the difference Viscount/Brit and Dart/Proteus but both engines were reverse (air) flow".
In words of one syllable (or maybe two) - boll*cks.
The Proteus as fitted to the Britannia was indeed a reverse flow engine but the RR Dart was most certainly not.
For those of you who are unfamiliar with reverse flow turbo prop engines, here comes a simple explanation.
The only reason to have a reverse flow engine is to reduce the length of the engine and make it more compact (like the PT-6). So, the airflow enters the intake behind the prop and then goes through a 180 degree bend before entering the compressor. Then it goes through another 180 degrees before the combustion stage and then exiting through the turbine stage.
On the Britannia, the Proteus engines used to ice-up badly on the first U-bend and this caused the aircraft to be years and years late on entering service.
Even then, the problem was never satisfactorily solved. The civilian Brits had heating skins (B skins) fitted but their use caused a 10% loss in thrust. Even then, the engines were for ever shutting down and restarting (called "bumping") in icing conditions and this ensured that the crew never were allowed to go to sleep.
The RAF had a cowl heat system fitted but this resulted (so I'm told) in a 25% loss in thrust every time the system was used.
I will now move on to the RR Dart; I flew the Argosy for ten years and also the Viscount 802/806.
The Dart was a conventional engine in that there was no reversal of flow. It simply went: compression stage, combustion stage and then turbine stage. That is why the Dart was such a long and slim engine.
In fact, the engine was developed in a very simple fashion. When the Da 6 was not powerful enough, compression and turbine stages were added and so it was that the cowlings got longer right up to the Da 10.
I have never heard of four Darts failing at once through icing. I have personally had four inches of jagged ice on the engine intakes after an engine antice fault and not one of them even murmured.
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I still think it Carb ice
Sorry about the bollocks ,Didnt the dart have a centrifugal stage whuch changed the direction of the airflow>?
As for the Viscounti icing up over Switzerland . Im not wrong about that .Caused plenty of kerfuffle at Bristol ,I was there
As for the Viscounti icing up over Switzerland . Im not wrong about that .Caused plenty of kerfuffle at Bristol ,I was there
Last edited by wilyflier; 23rd Nov 2008 at 21:53.
Well, I suppose it is a matter of your interpretation, but I would hardly call a two-stage centrifugal compressor where the airflow moves from the front of the engine towards the rear "a reverse flow engine".
Anyway, none of this has anything to do with BA038 so I'm off out.
Anyway, none of this has anything to do with BA038 so I'm off out.
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whattimedoweland,
Nice flight deck picture.
Does anyone happen to have a picture of the BA B777 first class cabin (four class cabin configuration), preferrably taken from the rear in the direction of flight?
Thanks,
Green-dot
Nice flight deck picture.
Does anyone happen to have a picture of the BA B777 first class cabin (four class cabin configuration), preferrably taken from the rear in the direction of flight?
Thanks,
Green-dot