NTSB update on Asiana 214
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I can never remember ever using FLCH after the FAF on any aircraft type. Maybe I am confused, but I'm pretty sure FLCH is actually a pitch mode either with max climb thrust or idle; elevator controls the speed, yes? Throttles would then control your rate of climb or descent. So, with power at idle, if indeed one was in FLCH, wouldn't you be descending at a good rate to maintain that speed? As I understand it, the Asiana flight was not descending too fast, just too slow. What does this have to do with FLCH?
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FLCH adjusts thrust to give you a rate of climb (or descent, as the case may be) to reach the selected altitude / level in 2 minutes. i.e. If you are descending 2000 FT, it will give you approximatly 500 FPM. 1000 FT / 250FPM, etc. The AP will adjust the thrust up to CLB, or IDLE, as the case may be to try and achieve this.
So, with power at idle, if indeed one was in FLCH, wouldn't you be descending at a good rate to maintain that speed?
Last edited by Capn Bloggs; 24th Jun 2014 at 05:49. Reason: "rubbish" comment deleted.
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The National Transportation Safety Board is debating the extent to which Boeings automatic throttle contributed to the 777s loss of speed before the jet slammed into a seawall in San Francisco last July 6, said three people with knowledge of the discussions.
WASHINGTON U.S. investigators are debating whether to blame a Boeing jetliners design for helping cause a cascade of pilot mistakes in last years Asiana Airlines crash that killed three Chinese teenagers.
The sticking point within the National Transportation Safety Board (NTSB), in the days before its final decision is due, is over the extent to which Boeings automatic throttle contributed to the 777s loss of speed before the jet slammed into a seawall in San Francisco on July 6, said three people with knowledge of the discussions. They asked not to be identified because they werent authorized to speak.
The safety board Tuesday will decide on the probable cause and other factors leading to Seoul-based Asianas crash, the first in the United States with passenger deaths in more than four years. While theres little doubt the pilots made mistakes, a finding that equipment on the 777-200 jet confused them could open Boeing to greater liability in lawsuits and shade public opinion.
WASHINGTON U.S. investigators are debating whether to blame a Boeing jetliners design for helping cause a cascade of pilot mistakes in last years Asiana Airlines crash that killed three Chinese teenagers.
The sticking point within the National Transportation Safety Board (NTSB), in the days before its final decision is due, is over the extent to which Boeings automatic throttle contributed to the 777s loss of speed before the jet slammed into a seawall in San Francisco on July 6, said three people with knowledge of the discussions. They asked not to be identified because they werent authorized to speak.
The safety board Tuesday will decide on the probable cause and other factors leading to Seoul-based Asianas crash, the first in the United States with passenger deaths in more than four years. While theres little doubt the pilots made mistakes, a finding that equipment on the 777-200 jet confused them could open Boeing to greater liability in lawsuits and shade public opinion.
Underfire reported:
An aircraft certified by the FAA is then criticised by the NTSB after an accident. What's an air-framer to do then?
On wonders exactly how Boeing are supposed to second guess the NTSB. It would seem that their first contact with the NTSB on a design issue is after an accident involving one of their aircraft flying with FAA certification.
If Boeing really are somehow dragged into it then surely there can be only one corporate response; no more automatics, other than a rudimentary autopilot. Same for Airbus too. If they are going to be liable in the US for a pilot's failure to fully understand these systems then they're not going to fit them in the first place.
Though surely the NTBS won't make such a finding, will they? I guess we'll find out in due course.
While there’s little doubt the pilots made mistakes, a finding that equipment on the 777-200 jet confused them could open Boeing to greater liability in lawsuits and shade public opinion.
On wonders exactly how Boeing are supposed to second guess the NTSB. It would seem that their first contact with the NTSB on a design issue is after an accident involving one of their aircraft flying with FAA certification.
If Boeing really are somehow dragged into it then surely there can be only one corporate response; no more automatics, other than a rudimentary autopilot. Same for Airbus too. If they are going to be liable in the US for a pilot's failure to fully understand these systems then they're not going to fit them in the first place.
Though surely the NTBS won't make such a finding, will they? I guess we'll find out in due course.
Originally Posted by Dartman
FLCH adjusts thrust to give you a rate of climb (or descent, as the case may be) to reach the selected altitude / level in 2 minutes. i.e. If you are descending 2000 FT, it will give you approximatly 500 FPM. 1000 FT / 250FPM, etc. The AP will adjust the thrust up to CLB, or IDLE, as the case may be to try and achieve this.
FLCH adjusts thrust to give you a rate of climb (or descent, as the case may be) to reach the selected altitude / level in 2 minutes. i.e. If you are descending 2000 FT, it will give you approximatly 500 FPM. 1000 FT / 250FPM, etc. The AP will adjust the thrust up to CLB, or IDLE, as the case may be to try and achieve this.
I don't fly the 777 but I call "rubbish" on all of that.
If the thrust comes back to IDLE, the autothrottle then transitions to HOLD. It doesn't 'wake up' again unless another vertical mode engages. Therein lies the problem.
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FAA and NTSB are supposed to be completely independent. So it is OK, that NTSB criticises what FAA has certified. That ist the whole idea behind, and it is an ICAO requirement.
FAA certified that the aircraft complied with the rules, not that it is foolproof, nor that it is the best possible aircraft one could build. The certificate determines that the minimum requirements are met, not the maximum anyone could require.
FAA certified that the aircraft complied with the rules, not that it is foolproof, nor that it is the best possible aircraft one could build. The certificate determines that the minimum requirements are met, not the maximum anyone could require.
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. So it is OK, that NTSB criticises what FAA has certified.
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Spot on Volume.
There have been many incidents. At my airline, I know that they've had several on the 777 just like Asiana. The only difference being that crews caught their mistake early on.
Even the regulator suffered from this FLCH trap during a certification flight on the 787, with the same logic. Boeing chose to ignore the recommendations as a result of that incident claiming that the FCOMs covered such a trap with sufficient clarity (even though it was more emphasised on the 787 FCOMs)
As much as I believe the crew in the AAR accident were incompetent, having 10K hours in 747s I personally think there is room for improvement in the automatics.
Just out of curiosity , has there ever been another serious incident/accident to the T7 because of the auto throttle misunderstanding ?
Even the regulator suffered from this FLCH trap during a certification flight on the 787, with the same logic. Boeing chose to ignore the recommendations as a result of that incident claiming that the FCOMs covered such a trap with sufficient clarity (even though it was more emphasised on the 787 FCOMs)
As much as I believe the crew in the AAR accident were incompetent, having 10K hours in 747s I personally think there is room for improvement in the automatics.
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I am puzzled by the choice made to inhibit min speed protection with AP or FD engaged and FLCH selected with Throttle 'HOLD'. I understand it also happens in VNAV speed. Does anyone know why this was chosen as a function? I never tried it in a 737 with LVLCHG so maybe it was the same there!
I am puzzled by the choice made to inhibit min speed protection with AP or FD engaged and FLCH selected with Throttle 'HOLD'.
Now if the AP and FD are off or FD ignored (dunno if exactly relevant to the 777) and pilot pulls back on stick, the AT does not react and speed decreases. This happens in my machine (not a real Boeing) when it is in equivalent of FLCH. Speed will reduce BUT, when Vmin is reached, even if the ATS is off, Lo Speed Protection engages, ATS comes alive and controls to Vmin. A similar function appears to be fitted to Airbii. Not so, it seems, 777 or by the sounds of it 787?
This, from the CNN article, will answer your question, BOAC:
Boeing said it was without fault.
"All airplane systems were functioning as expected prior to impact and did not contribute to the accident," it told the safety board.
Asked why the "hold" mode did not protect against dangerous drop-offs in speed, Boeing told the board, "To do this would violate (Boeing's) design philosophy: the pilot is the final authority for the operation of the airplane."
"If the auto-throttle automatically (switched mode to prevent an aerodynamic stall), it would be overriding the crew's selection," Boeing said.
"All airplane systems were functioning as expected prior to impact and did not contribute to the accident," it told the safety board.
Asked why the "hold" mode did not protect against dangerous drop-offs in speed, Boeing told the board, "To do this would violate (Boeing's) design philosophy: the pilot is the final authority for the operation of the airplane."
"If the auto-throttle automatically (switched mode to prevent an aerodynamic stall), it would be overriding the crew's selection," Boeing said.
Last edited by Capn Bloggs; 24th Jun 2014 at 14:05. Reason: Added article quote.
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"If the auto-throttle automatically (switched mode to prevent an aerodynamic stall), it would be overriding the crew's selection," Boeing said
I'm all for freedom of choice, but as a fare-paying pax now......................
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I'm all for freedom of choice, but as a fare-paying pax now
All I can say is they are very lucky only a few passengers died in this accident.
For those who were quick to blame SFO ATC, I hope you eat your shorts... This was no slam and dunk approach, he was brought in on a 14 mile final!
For those trying to blame Boeing for this, I don't agree.
This comes down to not knowing how the systems works (A/P and A/T), not following your own company's SOP, having a check pilot obviously not doing his job properly and ultimately a Captain trained on the B777 that can't fly his aircraft on a VFR day on a visual approach to a runway without the assistance of auto flight, in other words, manually.
For those who were quick to blame SFO ATC, I hope you eat your shorts... This was no slam and dunk approach, he was brought in on a 14 mile final!
For those trying to blame Boeing for this, I don't agree.
This comes down to not knowing how the systems works (A/P and A/T), not following your own company's SOP, having a check pilot obviously not doing his job properly and ultimately a Captain trained on the B777 that can't fly his aircraft on a VFR day on a visual approach to a runway without the assistance of auto flight, in other words, manually.