LATAM upset SYD-AKL Mon 11 Mar
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The problem with 2 buttons is that if the seat has to move -now- and one button fails then the pilot could be very restricted in making a rapid exit or prevented from getting into the seat and getting the seat arranged. Or maybe one switch fails in the "On" position and no one notices and then this same event happens when the second switch also fails.
Some days those big knife switches as appear in Frankenstein movies are very appealing. Up for forward, Down for back, and sit in the middle for don't move. But then you don't have enough room to replace all the switches with those. Someone spills coffee and it all goes abby normal.
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The SMYDs each rely on a single AoA sensor and don't have bounds checking and don't have self-verification of calibration**. MCAS relied on the SMYD. The SMYD issued the false stall warning that prevented the continued operation with the autopilot and autothrottle and pushed the plane into manual control. Whether MCAS existed or not the false stall warning remains a fundamental problem that some claim causes some pilots to be unable to function, being all startled.
**If the AoA sensor had two changes the SMYD could be changed to determine whether the sensor was clearly invalid. The first is a stop that the vane contacts at some extreme AoA, such as 60 degrees nose high. If the vane is removed the counterweight will move to an out-of-range position which is normally impossible, indicating a missing vane. Alternately or additionally, use a low current to check continuity to the vane heater (there is already a high-current check) and if there isn't continuity assume the vane is compromised. This warning was given on ET-302. Using both would confirm vane departure. The second is to add a small torque coil that would drive the vane to the stop. Since that stop is a known value the reading from the resolver can be checked as part of aircraft startup. Perhaps one has seen the clever gauge needles in cars do what looks like a range test, probably to confirm they are actually moving as commanded so drivers know the speed and RPM and fuel readings, et al, are correct and the needles aren't stuck. If the drive doesn't turn off, the AoA reading will be constant at that stop, also signalling an invalid AoA sensor. Drive in the other direction would meet the internal AoA sensor stop.
In the event that either test fails, the SMYD reports "invalid" or stops reporting data. MCAS is already programmed to shift to the other SMYD in the event such a report happens. In both accident aircraft the SMYD reported the unrealistic AoA sensor reading as valid.
Note that if the torque coil is used then the AoA sensor can also be given a small, perhaps 60Hz, continuous sinusoidal torque that is capable of making slight sinusoidal nudges to the AoA sensor which can be used to detect from the resulting sinusoidal output if the AoA vane is locked into place by ice or not. If the dithering is reasonably fast a simple averaging routine would smooth that out before sending it to the autopilot or to MCAS. Also, it would alert pilots that the AoA sensor had become unreliable if the vane doesn't move with a known torque. Airbus had an event happen with 2 of 3 vanes frozen and their system voted the only working one off the island before starting a nose-down trim event the pilot input could not overcome because, as speed increased the AoA needed to decrease, but the vanes were frozen in place and could not move. More nose-down trim kept getting added to correct the too-high AoA reading.
Some days those big knife switches as appear in Frankenstein movies are very appealing. Up for forward, Down for back, and sit in the middle for don't move. But then you don't have enough room to replace all the switches with those. Someone spills coffee and it all goes abby normal.
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The SMYDs each rely on a single AoA sensor and don't have bounds checking and don't have self-verification of calibration**. MCAS relied on the SMYD. The SMYD issued the false stall warning that prevented the continued operation with the autopilot and autothrottle and pushed the plane into manual control. Whether MCAS existed or not the false stall warning remains a fundamental problem that some claim causes some pilots to be unable to function, being all startled.
**If the AoA sensor had two changes the SMYD could be changed to determine whether the sensor was clearly invalid. The first is a stop that the vane contacts at some extreme AoA, such as 60 degrees nose high. If the vane is removed the counterweight will move to an out-of-range position which is normally impossible, indicating a missing vane. Alternately or additionally, use a low current to check continuity to the vane heater (there is already a high-current check) and if there isn't continuity assume the vane is compromised. This warning was given on ET-302. Using both would confirm vane departure. The second is to add a small torque coil that would drive the vane to the stop. Since that stop is a known value the reading from the resolver can be checked as part of aircraft startup. Perhaps one has seen the clever gauge needles in cars do what looks like a range test, probably to confirm they are actually moving as commanded so drivers know the speed and RPM and fuel readings, et al, are correct and the needles aren't stuck. If the drive doesn't turn off, the AoA reading will be constant at that stop, also signalling an invalid AoA sensor. Drive in the other direction would meet the internal AoA sensor stop.
In the event that either test fails, the SMYD reports "invalid" or stops reporting data. MCAS is already programmed to shift to the other SMYD in the event such a report happens. In both accident aircraft the SMYD reported the unrealistic AoA sensor reading as valid.
Note that if the torque coil is used then the AoA sensor can also be given a small, perhaps 60Hz, continuous sinusoidal torque that is capable of making slight sinusoidal nudges to the AoA sensor which can be used to detect from the resulting sinusoidal output if the AoA vane is locked into place by ice or not. If the dithering is reasonably fast a simple averaging routine would smooth that out before sending it to the autopilot or to MCAS. Also, it would alert pilots that the AoA sensor had become unreliable if the vane doesn't move with a known torque. Airbus had an event happen with 2 of 3 vanes frozen and their system voted the only working one off the island before starting a nose-down trim event the pilot input could not overcome because, as speed increased the AoA needed to decrease, but the vanes were frozen in place and could not move. More nose-down trim kept getting added to correct the too-high AoA reading.
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For the benefit of the uneducated among us, I shall now translate. ME is trying to demonstrate with all that gumph that the 737 Max is a much maligned product from an outstanding company whose main motivation is people before profit and that it was the useless pilots that are to blame. Bollocks is my reply.
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For the benefit of the uneducated among us, I shall now translate. ME is trying to demonstrate with all that gumph that the 737 Max is a much maligned product from an outstanding company whose main motivation is people before profit and that it was the useless pilots that are to blame. Bollocks is my reply.
For the benefit of the uneducated among us, I shall now translate. ME is trying to demonstrate with all that gumph that the 737 Max is a much maligned product from an outstanding company whose main motivation is people before profit and that it was the useless pilots that are to blame. Bollocks is my reply.
So you mean to say that the simple, albeit distressing, explanation for the 737 Max tragedies – useless pilots – turned out not to be a valid explanation? You mean to say that, sometimes, errors in design, errors in manufacture, errors in regulatory supervision or errors in maintenance can result in bad outcomes that are easily but invalidly blamed on pilots?
Please hold that thought and pop over to the thread about the recent 172 tragedy at Camden and reflect upon what you’ve posted there.
/thread drift off.
Oh I don't hold the pilots solely to blame. No one in their organization did more then forward the Emergency AD. No one checked to see if the pilots actually read it, actually understood it, actually memorized it. Might as well be on toilet paper. Does that not make anyone angry? They even owned MAX simulators and did not try the procedure.
I do find a great fault in the way the AoA sensors are managed on both Boeing and Airbus aircraft as not individually verifiable in spite of cases where 3X voting fails. This could be addressed at the lower module rather than a full system overhaul like synthetic AoA requires.
But, sure, compare the procedure for stall warning to the FDR. See any sign that the existing stall warning procedure, with decades of training in the type, was followed in the slightest? Is that an airplane problem or a pilot training problem?
I do find a great fault in the way the AoA sensors are managed on both Boeing and Airbus aircraft as not individually verifiable in spite of cases where 3X voting fails. This could be addressed at the lower module rather than a full system overhaul like synthetic AoA requires.
But, sure, compare the procedure for stall warning to the FDR. See any sign that the existing stall warning procedure, with decades of training in the type, was followed in the slightest? Is that an airplane problem or a pilot training problem?
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Interesting that now when you reply to me you use your real name but when you liked my post you used your nom de plume.
I have always been consistent with my discussion on the Max. Sometimes the pilots through deliberate action or non adherence to SOPs i.e.VMC into IMC are responsible for a crash. In this case Boeing introduced a digital response to an analogue problem and did not tell the pilots or the airlines what was going on. Its not rocket science. You compare your profession of lawyer with that of pilots and come to the conclusion that pilots don't come up to the same standard of conduct. Thats because you are on the outside looking in and simply don't understand the environment and mindset of the professional pilot. Pilots are always assessing the actions of other pilots and being critical of their conduct if necessary, that's how two crew operations work. I have explained my reasons for why I consider the Camden accident to be a deliberate action. For the same reason I consider MH370 a deliberate action by the PIC. Its not blaming the pilot simply because thats the simplest option in the way ME is trying to. Its looking at the flight profile and coming to a conclusion that a pilot trying maintain control and get an unsafe aeroplane on the ground would have flown a very different profile. If you want to see the difference look at the Silk Air 737 profile and then look at the Ethiopian 737 Max. Most professional pilots could spot the difference.
I have always been consistent with my discussion on the Max. Sometimes the pilots through deliberate action or non adherence to SOPs i.e.VMC into IMC are responsible for a crash. In this case Boeing introduced a digital response to an analogue problem and did not tell the pilots or the airlines what was going on. Its not rocket science. You compare your profession of lawyer with that of pilots and come to the conclusion that pilots don't come up to the same standard of conduct. Thats because you are on the outside looking in and simply don't understand the environment and mindset of the professional pilot. Pilots are always assessing the actions of other pilots and being critical of their conduct if necessary, that's how two crew operations work. I have explained my reasons for why I consider the Camden accident to be a deliberate action. For the same reason I consider MH370 a deliberate action by the PIC. Its not blaming the pilot simply because thats the simplest option in the way ME is trying to. Its looking at the flight profile and coming to a conclusion that a pilot trying maintain control and get an unsafe aeroplane on the ground would have flown a very different profile. If you want to see the difference look at the Silk Air 737 profile and then look at the Ethiopian 737 Max. Most professional pilots could spot the difference.
There was a reason in the 747 to have 2 switches in series, so with what rationale now a single switch does the same job?
Originally Posted by Mechengr
The problem with 2 buttons is that if the seat has to move -now- and one button fails then the pilot could be very restricted in making a rapid exit or prevented from getting into the seat and getting the seat arranged. Or maybe one switch fails in the "On" position and no one notices and then this same event happens when the second switch also fails.
If you need to get out in a hurry, just jump up, stand on it and GTFOOT.
One failed on and the other switch fails? Really?
Yes - unless there is a way to detect the switch has failed in the closed/conducting position then the situation ends up no different than if it was replaced by a piece of wire when it fails. It is far better to have a single, more robust switch than try to build a fail-safe logic out of components that do not fail in a safe manner.
When the Alaska jackscrew failed there were two nuts, one for "backup," but the backup had already failed by being unable to take the load when the primary failed; there wasn't any clear method of detecting the wear of the "backup" separately. Were it not for the false logic that there was a backup the development would likely have taken a different direction.
In this case, why didn't the pilot just jump up? Was he not quick enough?
When the Alaska jackscrew failed there were two nuts, one for "backup," but the backup had already failed by being unable to take the load when the primary failed; there wasn't any clear method of detecting the wear of the "backup" separately. Were it not for the false logic that there was a backup the development would likely have taken a different direction.
In this case, why didn't the pilot just jump up? Was he not quick enough?
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Yes - unless there is a way to detect the switch has failed in the closed/conducting position then the situation ends up no different than if it was replaced by a piece of wire when it fails. It is far better to have a single, more robust switch than try to build a fail-safe logic out of components that do not fail in a safe manner.
When the Alaska jackscrew failed there were two nuts, one for "backup," but the backup had already failed by being unable to take the load when the primary failed; there wasn't any clear method of detecting the wear of the "backup" separately. Were it not for the false logic that there was a backup the development would likely have taken a different direction.
In this case, why didn't the pilot just jump up? Was he not quick enough?
When the Alaska jackscrew failed there were two nuts, one for "backup," but the backup had already failed by being unable to take the load when the primary failed; there wasn't any clear method of detecting the wear of the "backup" separately. Were it not for the false logic that there was a backup the development would likely have taken a different direction.
In this case, why didn't the pilot just jump up? Was he not quick enough?
In this case, why didn't the pilot just jump up? Was he not quick enough?
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I can’t say I really understand any of this. If you bring the 787 seat all the way forward, you still don’t touch the control column assuming you’re sat normally.
If you did have something on your lap, or your legs crossed or similar, the seat moves so slowly that there would be ample time to move any obstacle out of the way.
If you did have something on your lap, or your legs crossed or similar, the seat moves so slowly that there would be ample time to move any obstacle out of the way.
Nearly 200 Posts on this Thread and 30 on the other Thread (same topic) and I have been struggling to find \a sensible Post! Ah well, that's PPRuNe!
A few days ago I had a thoroughly enjoyable flight on a B787. During the cruise we had a friendly hat with one of the cabin crew. Amongst many other topics, this LATAM incident was brought up and the seat issue had only just got into the news (we read it in the departure lounge). They had been briefed on the matter before the flight ad being aware of the info that they were given, sensible precautions were being taken. That real world does not fit in with the 230-odd pages of nonsense that there have been here.
We have another flight booked in a B787 next month and we are looking forward to it.
A few days ago I had a thoroughly enjoyable flight on a B787. During the cruise we had a friendly hat with one of the cabin crew. Amongst many other topics, this LATAM incident was brought up and the seat issue had only just got into the news (we read it in the departure lounge). They had been briefed on the matter before the flight ad being aware of the info that they were given, sensible precautions were being taken. That real world does not fit in with the 230-odd pages of nonsense that there have been here.
We have another flight booked in a B787 next month and we are looking forward to it.
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Nearly 200 Posts on this Thread and 30 on the other Thread (same topic) and I have been struggling to find \a sensible Post! Ah well, that's PPRuNe!
A few days ago I had a thoroughly enjoyable flight on a B787. During the cruise we had a friendly hat with one of the cabin crew. Amongst many other topics, this LATAM incident was brought up and the seat issue had only just got into the news (we read it in the departure lounge). They had been briefed on the matter before the flight ad being aware of the info that they were given, sensible precautions were being taken. That real world does not fit in with the 230-odd pages of nonsense that there have been here.
We have another flight booked in a B787 next month and we are looking forward to it.
A few days ago I had a thoroughly enjoyable flight on a B787. During the cruise we had a friendly hat with one of the cabin crew. Amongst many other topics, this LATAM incident was brought up and the seat issue had only just got into the news (we read it in the departure lounge). They had been briefed on the matter before the flight ad being aware of the info that they were given, sensible precautions were being taken. That real world does not fit in with the 230-odd pages of nonsense that there have been here.
We have another flight booked in a B787 next month and we are looking forward to it.
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