Computer failure most likely cause of 777 British Airways 38 accident
01-26-2008, 04:25 PM
#11
Gets Weekends Off
Joined APC: Mar 2006
Position: Contract purgatory
Posts: 701
You miss the power lever because you are high, hot, 1000 AGL is coming up real quick and you are behind the eight ball. The power lever on the 777 are as wide as the 747 across, there are just two of them.
You see, I just don't get it, and frankly (strike me down if I am, hopefully, dead wrong) I'm not not all together buying it. The only thing that tells me that I am wrong is that the pilot's and the AIB are saying that the engines did not respond to commanded thrust; but I am wondering about exactly what data on the DFDR they (the AIB) are looking at.
Allow me to explain:
The DFDR data tells them that at some point, I understand at around 600 feet, the power did started to advance, but then after three seconds the right power came back, then eight seconds later the left power. This makes absolutely no sense from a technical malfunction standpoint (but I am no engineering expert). What does make sense, as I have over the years seen this type of thing happen on an unstable approach (with previous employers only thankfully), is that the thrust reduced below commanded (A/T) because the pilot physically retarded the power levers.
On approach and with the A/T's armed, as you reduce speed and bring out flap you bug back the command airspeed bug to the next flap setting speed which is nicely represented on the tape. As the speed approaches that setting the Thrust Management Computer tells the A/T's to advance the power. If you are in a big hurry to reduce speed, and you call for the next flap setting just prior to bug speed, the power will start to advance. This is no worries, you just grab the levers and pull them back, the thrust will follow what you are setting over what the TMC and the Auto Pilot FD system think is prudent. The problem with my theory is that as you bugged the speed back to the next setting the commanded thrust would reduce as well. But, if you set that lower flap, then forgot to re-set the command airspeed but (these thing's happen on a regular basis if people are busy and not all together focussed) then the commanded thrust would want to stay up, even increase as the aircraft would require more to fly at that speed, with that flap setting.
The flaps; who in their right mind would reduce flap when below that speed. I'd say nobody. But, if one was high on speed, greater than 170 knots on the 777 with flap 30, then they would blow back automatically and not come back out until the speed had reduced to a lower one. To me, looking at the plane on the ground, the flaps look like they are fully out, but that's probably a stupid thing to say as it is pretty touch to judge. Either way, reducing flap makes no sense, nor does the idea that a pilot would even think that it was a good idea at 600 feet.
There have also been accounts that the plane was maneuvering somewhere on final, which you just don't do at LHR (they have you on the approach way back), and a number of people said that it was very loud as the plane came close to the ground. OK, it'd be pretty loud anyway, but it would be relevant to my wholly unlikely tale here. I have not seen any graphics of the approach course so that's admittedly pretty speculative.
The RAT can been seen but if it was deployed it would have been spinning and the blades would have been gone. They at least look quite intact in the picture.
The left engine at least was spinning at a reasonable rate as all of the fan blades are badly damaged; most looked missing or bent rite back.
Who thought it was a good idea to parade the skipper and co out in front of the public the next day. Likely some management jockey who was previously working for a large car rental agency and went to the pages in their management 101 book labeled "damage control". Also, as BALPA so furiously told the BA management that this was a grand example of why they should continue to only have BA pilots fly all BA planes, as they are so very skilled, the day of the accident. . . well, if I was BA management and I wanted to put a nail in that one, and I knew thing's were not as simple as being made out, perhaps I'd put the pilots in the public spotlight so as to more easily hang their butts out in the wind when it all came crashing down in the future.
But perhaps I am a bit paranoid. That would mean of course that two separate systems failed to respond when told to do so by everything, which is something that has never happened before on how many flights; basically one in a billion. And, it would all have to happen at 600 ft on final. Just just makes no sense, but I hope there is some weakness in the system that allowed this to happen, I really do. After looking at LOSA and IOSA numbers regarding unstable approaches it does make me wonder. Let's all hope I'm an idiot shall we.
You see, I just don't get it, and frankly (strike me down if I am, hopefully, dead wrong) I'm not not all together buying it. The only thing that tells me that I am wrong is that the pilot's and the AIB are saying that the engines did not respond to commanded thrust; but I am wondering about exactly what data on the DFDR they (the AIB) are looking at.
Allow me to explain:
The DFDR data tells them that at some point, I understand at around 600 feet, the power did started to advance, but then after three seconds the right power came back, then eight seconds later the left power. This makes absolutely no sense from a technical malfunction standpoint (but I am no engineering expert). What does make sense, as I have over the years seen this type of thing happen on an unstable approach (with previous employers only thankfully), is that the thrust reduced below commanded (A/T) because the pilot physically retarded the power levers.
On approach and with the A/T's armed, as you reduce speed and bring out flap you bug back the command airspeed bug to the next flap setting speed which is nicely represented on the tape. As the speed approaches that setting the Thrust Management Computer tells the A/T's to advance the power. If you are in a big hurry to reduce speed, and you call for the next flap setting just prior to bug speed, the power will start to advance. This is no worries, you just grab the levers and pull them back, the thrust will follow what you are setting over what the TMC and the Auto Pilot FD system think is prudent. The problem with my theory is that as you bugged the speed back to the next setting the commanded thrust would reduce as well. But, if you set that lower flap, then forgot to re-set the command airspeed but (these thing's happen on a regular basis if people are busy and not all together focussed) then the commanded thrust would want to stay up, even increase as the aircraft would require more to fly at that speed, with that flap setting.
The flaps; who in their right mind would reduce flap when below that speed. I'd say nobody. But, if one was high on speed, greater than 170 knots on the 777 with flap 30, then they would blow back automatically and not come back out until the speed had reduced to a lower one. To me, looking at the plane on the ground, the flaps look like they are fully out, but that's probably a stupid thing to say as it is pretty touch to judge. Either way, reducing flap makes no sense, nor does the idea that a pilot would even think that it was a good idea at 600 feet.
There have also been accounts that the plane was maneuvering somewhere on final, which you just don't do at LHR (they have you on the approach way back), and a number of people said that it was very loud as the plane came close to the ground. OK, it'd be pretty loud anyway, but it would be relevant to my wholly unlikely tale here. I have not seen any graphics of the approach course so that's admittedly pretty speculative.
The RAT can been seen but if it was deployed it would have been spinning and the blades would have been gone. They at least look quite intact in the picture.
The left engine at least was spinning at a reasonable rate as all of the fan blades are badly damaged; most looked missing or bent rite back.
Who thought it was a good idea to parade the skipper and co out in front of the public the next day. Likely some management jockey who was previously working for a large car rental agency and went to the pages in their management 101 book labeled "damage control". Also, as BALPA so furiously told the BA management that this was a grand example of why they should continue to only have BA pilots fly all BA planes, as they are so very skilled, the day of the accident. . . well, if I was BA management and I wanted to put a nail in that one, and I knew thing's were not as simple as being made out, perhaps I'd put the pilots in the public spotlight so as to more easily hang their butts out in the wind when it all came crashing down in the future.
But perhaps I am a bit paranoid. That would mean of course that two separate systems failed to respond when told to do so by everything, which is something that has never happened before on how many flights; basically one in a billion. And, it would all have to happen at 600 ft on final. Just just makes no sense, but I hope there is some weakness in the system that allowed this to happen, I really do. After looking at LOSA and IOSA numbers regarding unstable approaches it does make me wonder. Let's all hope I'm an idiot shall we.
01-28-2008, 11:59 AM
#15
APC co-founder
Joined APC: Feb 2005
Position: B777
Posts: 5,853
Originally Posted by KoruPilot
The RAT can been seen but if it was deployed it would have been spinning and the blades would have been gone. They at least look quite intact in the picture.
I'm a strong advocate of waiting for the formal report too. There are reports out today suggesting that fuel temp/contaminates could be an issue.
upper air temperatures over Russia and northern Europe were extremely cold on the day of the accident. Information from other crews coming from Asia on Jan. 17 encountered extremely low temperatures in the -70 to -75 degrees C. range, resulting in fuel temperatures dipping into the -40s. European upper air temperatures also indicate the last 6.5 hours of the inbound China flight would have been flown at an outside air temperature of -60 deg. C. or lower. Although this would have resulted in fuel temperatures on approach in the -35 degrees C range, this would not normally constitute a problem unless, potentially, contaminants were present.
01-28-2008, 12:46 PM
#16
Gets Weekends Off
Joined APC: Mar 2006
Position: Contract purgatory
Posts: 701
You can se the RAT on the right side of the wreckage; the turbine looks intact but. . . (I didn't notice it in the video either, but it wasn't great video)
At any rate, the engines didn't quit, so the transfer buses would not have fired up, so the RAT would not have deployed.
Boeing changed the fuel tanks on the B777 so the aircraft would not have the same problem that the 747 had regarding freezing fuel, so that's really kind of unlikely. Some sort of contamination, other that water, could have done the trick however. But then all the samples they are taking from fuel uploads in Beijing should show the same contaminant. Even then, why just the one airplane, and for both tanks to experience the same problem at about the same time. Remember as well that the center tank would have run dry about five hours prior, and there would have been just about a ton left when it did, so if there was a contaminant problem it should have shown up there.
Of course the AIB would have thought of this, so like every one else they are grasping at straws a bit.
None the less, it really appears to be the only 'logical' technical explanation. I just don't see two staggered EEC problems, but perhaps a smart design engineer will help out and come up with an explanation.
At any rate, the engines didn't quit, so the transfer buses would not have fired up, so the RAT would not have deployed.
Boeing changed the fuel tanks on the B777 so the aircraft would not have the same problem that the 747 had regarding freezing fuel, so that's really kind of unlikely. Some sort of contamination, other that water, could have done the trick however. But then all the samples they are taking from fuel uploads in Beijing should show the same contaminant. Even then, why just the one airplane, and for both tanks to experience the same problem at about the same time. Remember as well that the center tank would have run dry about five hours prior, and there would have been just about a ton left when it did, so if there was a contaminant problem it should have shown up there.
Of course the AIB would have thought of this, so like every one else they are grasping at straws a bit.
None the less, it really appears to be the only 'logical' technical explanation. I just don't see two staggered EEC problems, but perhaps a smart design engineer will help out and come up with an explanation.
01-28-2008, 01:24 PM
#17
APC co-founder
Joined APC: Feb 2005
Position: B777
Posts: 5,853
Oops, I guess I had a photo of an intact RAT all along:
Large Version Here
I get dizzy speculating, so I'm just going to sit on the sidelines and wait for the report. It is unsettling to be in the fleet and not have even a hint of an answer.
Large Version Here
I get dizzy speculating, so I'm just going to sit on the sidelines and wait for the report. It is unsettling to be in the fleet and not have even a hint of an answer.
01-28-2008, 01:32 PM
#18
Gets Weekends Off
Joined APC: Mar 2006
Position: Contract purgatory
Posts: 701
I agree, which is perhaps why I am 'talking it out' so to speak. It is just so similar to potential problems that I have encountered over the years, that kind of go unbeknown to the pilots and end in an unflattering aircraft state. Usually, however, they end up going around. So really, if these guy's could have gone around, or made the runway, they surely would have. Nothing they have mentioned makes sense to me when I think it through though, so yea, I'm really looking forward to seeing a result. Funny that neither Boeing, nor RR appear to be losing any sleep over this though.
Like you, being on the 777 and knowing how the systems operate, I just don't get it.
I should also mention that whenever I post something like this (or open my mouth) I am wrong, so the pilots have nothing to worry about.
Like you, being on the 777 and knowing how the systems operate, I just don't get it.
I should also mention that whenever I post something like this (or open my mouth) I am wrong, so the pilots have nothing to worry about.
01-28-2008, 01:49 PM
#19
Gets Weekends Off
Joined APC: Mar 2006
Position: B777 FO
Posts: 416
I posted this in a couple different places but thought I would report in this thread.
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I think if it were a fuel contamination problem there would have been other instances of this occurring out of PEK that day. On the 744 if we get low fuel temps we have to resolve the issue as quickly as possible. We can usually accomplish this by speeding up and/or descending.
I encountered outside temps of -75C a few weeks ago over northern Canada. We sped up and descended. This kept the fuel temp at roughly -36C until we came out of that cold air. Initially we sped up from .83 to .87 and that started to do the trick. Keep in mind, we were fueled in DFW with Jet A not A1. Our procedure is that we must have been fueled three sectors with A1 before we can use that -47C as a freeze point.
Could be that the aircraft had been fueled with Jet A at some point in the past couple days and a bit of it was still in the tanks? Not sure what MMO is on the 777 but they may not have been able to speed up enough to get above -40C. Having been fueled with Jet A1 out of Beijing, they may not have been concerned with it. It would be interesting to see where that aircraft had been over the previous few days.
--------------------------------------------------------------------------
I think if it were a fuel contamination problem there would have been other instances of this occurring out of PEK that day. On the 744 if we get low fuel temps we have to resolve the issue as quickly as possible. We can usually accomplish this by speeding up and/or descending.
I encountered outside temps of -75C a few weeks ago over northern Canada. We sped up and descended. This kept the fuel temp at roughly -36C until we came out of that cold air. Initially we sped up from .83 to .87 and that started to do the trick. Keep in mind, we were fueled in DFW with Jet A not A1. Our procedure is that we must have been fueled three sectors with A1 before we can use that -47C as a freeze point.
Could be that the aircraft had been fueled with Jet A at some point in the past couple days and a bit of it was still in the tanks? Not sure what MMO is on the 777 but they may not have been able to speed up enough to get above -40C. Having been fueled with Jet A1 out of Beijing, they may not have been concerned with it. It would be interesting to see where that aircraft had been over the previous few days.
01-28-2008, 03:37 PM
#20
Gets Weekends Off
Joined APC: Mar 2006
Position: Contract purgatory
Posts: 701
That's a good point. Leaving LAX for LHR we do have to be a bit more careful due to just that. Even though we talk about the same procedures for warming thing's up, the Boeing people tell us that it is simply not an issue on the 777, as I understand it, due to the leading edge of the tank; different positioning or more insulation I do not know. I've only flown the LAX-LHR route a few times in the 777, but twice we had fuel temp advisories and never made it close to where we would have been worried, even with Jet A.
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