BA038 (B777) Thread
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BA38s engines "Hesitated"
Dear Me Myself,
"Unknowingly" means, that crews very seldom stay at idle power during the whole descent, since ATC req. some "level flight" or "holding".
But the BA38 crew had a very light plane and "not headwind" during descent,
they even entered and departed "Lamborne Holding" descending at idle power.
Dear fellow pilots, have you read any other (and better) possible cause of this 104 day old mystery?
Oluf
"Unknowingly" means, that crews very seldom stay at idle power during the whole descent, since ATC req. some "level flight" or "holding".
But the BA38 crew had a very light plane and "not headwind" during descent,
they even entered and departed "Lamborne Holding" descending at idle power.
Dear fellow pilots, have you read any other (and better) possible cause of this 104 day old mystery?
Oluf
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Oluf
On a modern jet engine, which parts are actually anti/de-iced by "hot air"? The answer, I suggest, may help to focus some of the wilder speculation going on here.
And do you really think the absence of any "remaining" ice due to melting will have escaped the AAIB?
On a modern jet engine, which parts are actually anti/de-iced by "hot air"? The answer, I suggest, may help to focus some of the wilder speculation going on here.
And do you really think the absence of any "remaining" ice due to melting will have escaped the AAIB?
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Oluf,
Is that your assumption or is it based on facts? The AAIB only mentioned that the aircraft entered the hold at Lamborne at FL110; it remained in the hold for approximately 5 minutes, during which it descended to FL90.
Although that would give an average 400 ft/min rate of descent, the aircraft may have maintained FL110 for 3 or 4 minutes before descending to FL90? No mention in the report how the hold was performed. Or does a descent in the hold include a standard descent procedure?
Regards,
Green-dot
But the BA38 crew had a very light plane and "not headwind" during descent, they even entered and departed "Lamborne Holding" descending at idle power.
Although that would give an average 400 ft/min rate of descent, the aircraft may have maintained FL110 for 3 or 4 minutes before descending to FL90? No mention in the report how the hold was performed. Or does a descent in the hold include a standard descent procedure?
Regards,
Green-dot
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BA38s engines "Hesitated"
Dear Starbear,
The jet engine "Lips", the compressors big-fan blades and the very first part
of the "core-engine" is kept above the freezing point by hot bleed air, if you remember to turn the system "on" and increase the power setting.
"The higher the temperature, the more severe is the icing situation" up to +10 degrees C. (since the cloud water content, at 100% humidity, is approx. the double at +10 C, than it is at 0 degrees C.)
The amount of ice needed to make the engines to hesitate, can easily be gone, before the AAIB gets around, when the ground temperature is/was 11 degrees C.
Oluf
The jet engine "Lips", the compressors big-fan blades and the very first part
of the "core-engine" is kept above the freezing point by hot bleed air, if you remember to turn the system "on" and increase the power setting.
"The higher the temperature, the more severe is the icing situation" up to +10 degrees C. (since the cloud water content, at 100% humidity, is approx. the double at +10 C, than it is at 0 degrees C.)
The amount of ice needed to make the engines to hesitate, can easily be gone, before the AAIB gets around, when the ground temperature is/was 11 degrees C.
Oluf
Why only this one?
One thing is clear - the BA38 incident was self evidently an exeptional event. I am doubtful about how the engine icing theory fits this bill. If such a relatively unexeptional approach profile can cause this problem, why are B777s not dropping like flies?
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BA38s engines "Hesitated"
Dear Green-dot,
I is my assumption, since also i only have the AAIB feb. report, but if BA38
just had some speed above "Holding Speed" when entering Lamborne at FL110 and was cleared to FL90 early, they could have stayed at idle power.
The AAIB report don't even mention if the engine anti-ice system was used,
very strange, since the actual weather was "Broken Clouds" over London.
Oluf
I is my assumption, since also i only have the AAIB feb. report, but if BA38
just had some speed above "Holding Speed" when entering Lamborne at FL110 and was cleared to FL90 early, they could have stayed at idle power.
The AAIB report don't even mention if the engine anti-ice system was used,
very strange, since the actual weather was "Broken Clouds" over London.
Oluf
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BA38s engines "Hesitated"
Dear Dont Hang Up,
During my 30 years of descents, I almost never did one without some level-offs or "Holdings", but I think, that was what the BA38 crew did.
And further more, I was almost always "Stabilized" no later than 1000 ft. and had my engine anti-ice system "on" when flying in and out of clouds.
Oluf
During my 30 years of descents, I almost never did one without some level-offs or "Holdings", but I think, that was what the BA38 crew did.
And further more, I was almost always "Stabilized" no later than 1000 ft. and had my engine anti-ice system "on" when flying in and out of clouds.
Oluf
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Oluf
Wild,wild speculation my friend. And for the record is the anti-ice system on the 777 not automatic..i.e.doesn't require "switching on" in the traditional sense.
Also i understand that at idle thrust adequate engine anti-ice is provided by the switch from low-stage to high stage bleed air. Otherwise no anti-ice would be available from high flight levels for long periods of time.
Just leave it to the AAIB who i'm sure will have considered this at some point QED.
Wild,wild speculation my friend. And for the record is the anti-ice system on the 777 not automatic..i.e.doesn't require "switching on" in the traditional sense.
Also i understand that at idle thrust adequate engine anti-ice is provided by the switch from low-stage to high stage bleed air. Otherwise no anti-ice would be available from high flight levels for long periods of time.
Just leave it to the AAIB who i'm sure will have considered this at some point QED.
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BA38s engines "Hesitated"
Dear 3Greens,
Any descriptive of the Anti-ice systems (on most jet engines) claims to work, also at idle power, but that is mostly to comply with the certification, not in the real world.
P & W send at notice to: "All costumers" in the year 1994, that you need more than idle power to have any/some effect from the anti-ice systems.
Oluf (read all about it here: www.whistleblowers.dk )
Any descriptive of the Anti-ice systems (on most jet engines) claims to work, also at idle power, but that is mostly to comply with the certification, not in the real world.
P & W send at notice to: "All costumers" in the year 1994, that you need more than idle power to have any/some effect from the anti-ice systems.
Oluf (read all about it here: www.whistleblowers.dk )
Paxing All Over The World
Don't Hang Up
I think the point being made is NOT so much about the descent profile but the exceptionally low temperatures that were encountered in the cruise. Many other AC encountering the same cold air mass had to drop height. Some people are considering that the extended cold soak of the fuel was then met by icing conditions during the descent.
Which is why this one-off event is so perplexing. There may well be guidance from the AAIB and manufacturers, there may well have to be another five years elapse before it happens again and more data is captured. It may never happen again.
obie2
The 50 seconds I read was quoted earlier in this thread but, as I recall, not more than 60 seconds elapsed from loss of power to ground contact. Thinking time for a unique event that no one had ever encountered before? And yet some (I am merely an observer) criticise the crew for not taking out A/P and all sorts of other things. It is thanks to them that we can be discussing data and a very different AAIB problem.
If such a relatively unexeptional approach profile can cause this problem, why are B777s not dropping like flies?
Which is why this one-off event is so perplexing. There may well be guidance from the AAIB and manufacturers, there may well have to be another five years elapse before it happens again and more data is captured. It may never happen again.
obie2
Assuming 180 kts average over 4nm= 80 secs.
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The Sun
I see some columnist in The (soaraway) Sun has postulated his theory today....no gas in the tank? Is this to be discounted as pure Journo speculation....or is the investigation leaking again?
I'm sorry to read so many posts using the words engine icing and anti-ice in such an unsupportable matter regarding BA038.
Not for many years have these large fan engines used piped hot air to warm up the blades or vanes to keep ice off them. In the air they depend on the compression cycle temperature rise, centrifugal force and air air-velocity loads to shed accreted ice at low enough mass levels to not damage the engine internal parts or affect the engine surge stability.
Whilst tis true that the culprit ice does melt, its evidence on the engine that it leaves behind is unmistakeable to an investigator.
So to me the credibility of the engine teardown examination as well as the memory readouts pretty much eliminates this area still in consideration.
Not for many years have these large fan engines used piped hot air to warm up the blades or vanes to keep ice off them. In the air they depend on the compression cycle temperature rise, centrifugal force and air air-velocity loads to shed accreted ice at low enough mass levels to not damage the engine internal parts or affect the engine surge stability.
Whilst tis true that the culprit ice does melt, its evidence on the engine that it leaves behind is unmistakeable to an investigator.
So to me the credibility of the engine teardown examination as well as the memory readouts pretty much eliminates this area still in consideration.
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BA38s engines "Hesitated"
Dear lomapaseo,
You and a few others think, that I should wait for the AAIB or drop my theory of possible engine ice produced "hesitation"
OK, can you explain, why the FAA issued an AD on the 23. jan. 2008, only six days after BA38s "grass-landing" in order to:
"Prevent internal engine damage due to ice accumulation and shedding, which could cause a shutdown of both engines, and result in a forced landing of the airplane"
It was a 10 page AD called 2008-02-05 (or Directorate Identifier 2005-NM-263-AD) effective Feb. 27. 2008.
Valid for: Boeing Model 777-200 and -300 Series Airplanes Equiped With Roll-Royce RB211-TRENT 800 Series Engines.
Read it yourself, the improved procedure, calls for a more strict "engine anti-ice ON GROUND procedure" why this can avoid shut downs when airborne beats me. But it is the only change of procedures, since 17. jan.
2008.
So, at least the FAA thinks that engine ice might be the villain, why have the AAIB not commented on this AD.
Oluf
You and a few others think, that I should wait for the AAIB or drop my theory of possible engine ice produced "hesitation"
OK, can you explain, why the FAA issued an AD on the 23. jan. 2008, only six days after BA38s "grass-landing" in order to:
"Prevent internal engine damage due to ice accumulation and shedding, which could cause a shutdown of both engines, and result in a forced landing of the airplane"
It was a 10 page AD called 2008-02-05 (or Directorate Identifier 2005-NM-263-AD) effective Feb. 27. 2008.
Valid for: Boeing Model 777-200 and -300 Series Airplanes Equiped With Roll-Royce RB211-TRENT 800 Series Engines.
Read it yourself, the improved procedure, calls for a more strict "engine anti-ice ON GROUND procedure" why this can avoid shut downs when airborne beats me. But it is the only change of procedures, since 17. jan.
2008.
So, at least the FAA thinks that engine ice might be the villain, why have the AAIB not commented on this AD.
Oluf
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BA38s engines "Hesitated"
Dear lomapaseo,
You and a few others think, that I should wait for the AAIB or drop my theory of possible engine ice produced "hesitation"
OK, can you explain, why the FAA issued an AD on the 23. jan. 2008, only six days after BA38s "grass-landing" in order to:
"Prevent internal engine damage due to ice accumulation and shedding, which could cause a shutdown of both engines, and result in a forced landing of the airplane"
It was a 10 page AD called 2008-02-05 (or Directorate Identifier 2005-NM-263-AD) effective Feb. 27. 2008.
Valid for: Boeing Model 777-200 and -300 Series Airplanes Equiped With Roll-Royce RB211-TRENT 800 Series Engines.
Read it yourself, the improved procedure, calls for a more strict "engine anti-ice ON GROUND procedure" why this can avoid shut downs when airborne beats me. But it is the only change of procedures, since 17. jan.
2008.
So, at least the FAA thinks that engine ice might be the villain, why have the AAIB not commented on this AD.
Oluf
You and a few others think, that I should wait for the AAIB or drop my theory of possible engine ice produced "hesitation"
OK, can you explain, why the FAA issued an AD on the 23. jan. 2008, only six days after BA38s "grass-landing" in order to:
"Prevent internal engine damage due to ice accumulation and shedding, which could cause a shutdown of both engines, and result in a forced landing of the airplane"
It was a 10 page AD called 2008-02-05 (or Directorate Identifier 2005-NM-263-AD) effective Feb. 27. 2008.
Valid for: Boeing Model 777-200 and -300 Series Airplanes Equiped With Roll-Royce RB211-TRENT 800 Series Engines.
Read it yourself, the improved procedure, calls for a more strict "engine anti-ice ON GROUND procedure" why this can avoid shut downs when airborne beats me. But it is the only change of procedures, since 17. jan.
2008.
So, at least the FAA thinks that engine ice might be the villain, why have the AAIB not commented on this AD.
Oluf
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This is pure speculation from someone no longer associated with airlines, but I am afraid it may not be so easy to discard Mr. Husted's theory.
I note that the latest AAIB report says:
Posters have jumped to the conclusion that if the fuel flow increase was scheduled, then, if engine thrust did not increase, therefore the scheduled fuel flow increase did not happen. But, unless I'm missing something somewhere else, that's not what the report says.
Absent independent data from a fuel flow sensor showing that fuel flow did not increase, then I wonder if it's possible that fuel flow did increase, but that Mr. Husted's core icing prevented the engines from generating sufficient thrust?
If this were the case, I suspect there would be considerable egg on a lot of faces in the industry.
P.S.: In a fully flapped (40 deg) Cessna on a 3 degree approach at 500 ft, at engine idle I can't reach the end of the runway either. Please think about it before criticising the pilots.
I note that the latest AAIB report says:
Data, downloaded from the Electronic Engine Controllers
(EECs) and the QAR, revealed no anomalies with the
control system operation. At the point when the right
engine began to lose thrust the data indicated that the
right engine EEC responded correctly to a reduction
in fuel flow to the right engine, followed by a similar
response from the left EEC when fuel flow to the left
engine diminished. Data also revealed that the fuel
metering valves on both engines correctly moved to then
fully open position to schedule an increase in fuel flow.
Both fuel metering units were tested and examined, and
revealed no pre-existing defects.
(EECs) and the QAR, revealed no anomalies with the
control system operation. At the point when the right
engine began to lose thrust the data indicated that the
right engine EEC responded correctly to a reduction
in fuel flow to the right engine, followed by a similar
response from the left EEC when fuel flow to the left
engine diminished. Data also revealed that the fuel
metering valves on both engines correctly moved to then
fully open position to schedule an increase in fuel flow.
Both fuel metering units were tested and examined, and
revealed no pre-existing defects.
Absent independent data from a fuel flow sensor showing that fuel flow did not increase, then I wonder if it's possible that fuel flow did increase, but that Mr. Husted's core icing prevented the engines from generating sufficient thrust?
If this were the case, I suspect there would be considerable egg on a lot of faces in the industry.
P.S.: In a fully flapped (40 deg) Cessna on a 3 degree approach at 500 ft, at engine idle I can't reach the end of the runway either. Please think about it before criticising the pilots.
I don't think that increased fuel flow would be prevented by core icing, if fuel flow was reported to be increased with no response then icing could be suspected, but fuel flow did not reportedly increase. As I understand the term, the engines did not hesitate, they merely carried on in accordance with the fuel they received. Regarding the AD, as far as I am aware, freezing fog was not present nor poor vis.
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BA38s engines "Hesitated"
Dear Oldlae,
The definition of a cloud could be: "Freezing Fog" or just "Fog" and the visibility is always lousy in fog, and that is what the AD warns about.
Oluf
The definition of a cloud could be: "Freezing Fog" or just "Fog" and the visibility is always lousy in fog, and that is what the AD warns about.
Oluf
Oldlae:
No Oldlae, you are making an assumption. Nowhere in the report does it say that the fuel flow did not increase. What it says is that "the fuel
metering valves on both engines correctly moved to then fully open position to schedule an increase in fuel flow." You are making the causal assumption that since this occurred, and the engine did not respond, then the increased fuel flow did not occur.
As far as I can tell, the AAIB used those words because it does not have the data to show whether an increased fuel flow occurred or not.
To put it another way, if the AAIB knew for a fact that the fuel flow did not increase, they would have said the fuel flow did not increase, but that is not what they said.
If Mr. Husted's theory is correct, maybe an increase in fuel flow did occur, but the engine did not respond because of core icing.
but fuel flow did not reportedly increase
metering valves on both engines correctly moved to then fully open position to schedule an increase in fuel flow." You are making the causal assumption that since this occurred, and the engine did not respond, then the increased fuel flow did not occur.
As far as I can tell, the AAIB used those words because it does not have the data to show whether an increased fuel flow occurred or not.
To put it another way, if the AAIB knew for a fact that the fuel flow did not increase, they would have said the fuel flow did not increase, but that is not what they said.
If Mr. Husted's theory is correct, maybe an increase in fuel flow did occur, but the engine did not respond because of core icing.
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Did fuel flow increase or not?
Sunfish,
....Presumably an increase of fuel flow without rotational acceleration would have led to higher engine temperatures.Wouldnt these show on FDR or QAR ?
....Presumably an increase of fuel flow without rotational acceleration would have led to higher engine temperatures.Wouldnt these show on FDR or QAR ?