Ethiopian airliner down in Africa
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Your analysis is fundamentally flawed because AOA is not valid before takeoff, and any data points prior to that must be ignored. The AOA sensor relies on significant forward speed to align the vane with the airflow, and this is not possible while taxiing.
Your analysis is fundamentally flawed because AOA is not valid before takeoff, and any data points prior to that must be ignored. The AOA sensor relies on significant forward speed to align the vane with the airflow, and this is not possible while taxiing.
Any data points before takeoff (or after landing) do not correlate with real AOA values, without significant forward speed the vane will not reflect anything resembling AOA: Obviously correct.
These data points should be ignored? I don't agree. Lots and lots of hints there.
For instance, a constant offset theory (like bad indexing) doesn't hold water:
If the offset were there from the power on, as in a software error, it is an amazing coincidence that the right side vane, supposedly ok, has no noise and very minimal changes on the ground while the left one (suspect) has significant noise and/or large changes in both flights. (true I'm only basing this on 3 taxi events, but each is some minutes long). As opposed as in the air, where you could not tell one from the other if it wasn't for the offset. Wind on the ground will move the vanes randomly, of course, but it is an amazing coincidence that only left side dances in all three taxiing events.
Another example. If the offset were a consequence of a wrong correction table based on airspeed being used in the left side computer, it would be an impossible coincidence that the offset remained after landing with airspeed back to zero, as we can see in the data trace of the previous flight.
I would regard any proposed theory better if it is consistent with that behaviour in the air and on the ground seen in both data traces.
In fact, due to Occam's razor, any theory should also be consistent with the rest of the alarms. Specially the FEEL PRESS DIFF. There must be a root cause for all this.
Don't you agree?
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Boeing are going to make damn sure branding of the next variant of the Max will be an ocean of clear blue water away from the Max-8/9. They might even drop the 'Max' name, and come up with something touchy-feely that taps into the 'Dreamliner' imagery - The '737-Sunliner', perhaps.
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Boeing are going to make damn sure branding of the next variant of the Max will be an ocean of clear blue water away from the Max-8/9. They might even drop the 'Max' name, and come up with something touchy-feely that taps into the 'Dreamliner' imagery - The '737-Sunliner', perhaps.
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“From reading the comments on the mainstream media stories covering this issue, my sense is that a large percentage of pax don't have that faith. I'll be surprised if there isn't widespread reluctance to fly the MAX as SLF, when it returns to commercial service”
I’m former ATC and I can tell you that even before the MAX was grounded I had checked that my next flight was NOT a MAX, otherwise I would have cancelled it right away. This beeing said, I think that with time, assuming the MAX is allowed to fly again, fewer and fewer people will keep in mind that this version of the venerable 737 has gone a step too far and is probably the last “improved” version of this cable and pulleys dinausaur.
Yet, our last chance of pushing certification agencies to take their mission seriously is for the travellers to refuse to board a plane when they have good reasons to believe their safety was sacrified to better profit for the shareholders which is clearly the case here.
Vincent
I’m former ATC and I can tell you that even before the MAX was grounded I had checked that my next flight was NOT a MAX, otherwise I would have cancelled it right away. This beeing said, I think that with time, assuming the MAX is allowed to fly again, fewer and fewer people will keep in mind that this version of the venerable 737 has gone a step too far and is probably the last “improved” version of this cable and pulleys dinausaur.
Yet, our last chance of pushing certification agencies to take their mission seriously is for the travellers to refuse to board a plane when they have good reasons to believe their safety was sacrified to better profit for the shareholders which is clearly the case here.
Vincent
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Band-aid on a band-aid - that's the Boeing design philosophy of the Max. The AoA display makes little, if any, safety contribution to the flight deck (procedure wise) and the AOA disagree light even less. What is a pilot supposed to do when the AoA disagree light illuminates? Hit the trim switches? I wonder how often that light will illuminate, anyway. Probably often enough to get ignored.
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Band-aid on a band-aid - that's the Boeing design philosophy of the Max. The AoA display makes little, if any, safety contribution to the flight deck (procedure wise) and the AOA disagree light even less. What is a pilot supposed to do when the AoA disagree light illuminates? Hit the trim switches? I wonder how often that light will illuminate, anyway. Probably often enough to get ignored.
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Band-aid on a band-aid - that's the Boeing design philosophy of the Max. The AoA display makes little, if any, safety contribution to the flight deck (procedure wise) and the AOA disagree light even less. What is a pilot supposed to do when the AoA disagree light illuminates? Hit the trim switches? I wonder how often that light will illuminate, anyway. Probably often enough to get ignored.
Notably, the Max had already got a poor passenger reception for reduced passenger ambience standards, with carriers such as American, with (compared to the NG) reduced seat pitch, particularly cheaper-feeling and less padded seats, and a very minimalist toilet module that some felt difficult to even turn round in. When assigned to long runs such as Miami down to South America these were all apparently noticeable. Yet the carrier did not seem to find them an issue, and continued to market the services and take delivery of additional aircraft without issue.
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BBC News: Ethiopian Airlines crash: 'Pitch up, pitch up!'
Leaks this week from the crash investigation in Ethiopia and in the US suggest an automatic anti-stall system was activated at the time of the disaster
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Band-aid on a band-aid - that's the Boeing design philosophy of the Max. The AoA display makes little, if any, safety contribution to the flight deck (procedure wise) and the AOA disagree light even less. What is a pilot supposed to do when the AoA disagree light illuminates? Hit the trim switches? I wonder how often that light will illuminate, anyway. Probably often enough to get ignored.
I have never had it come on. Never had a problem related to the AOA sensors either.
Are the MAX sensors a new design?
But neither Ethiopian nor Lion had it installed.
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Basically analog, AC, fixed freq, varying amplitude, going from maxAOA (vmax, 0) to minAOA (0, vmax) and being centered in (0.707vmax, 0.707vmax).
I'm not sure, though.
No, sensors are interchangeable with those on the NG.
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From the NY Times...
In Ethiopia Crash, Faulty Sensor on Boeing 737 Max Is Suspected
Black box data from a doomed Ethiopian Airlines flight suggests the crash was caused by a faulty sensor that erroneously activated an automated system on the Boeing 737 Max, a series of events suspected in an Indonesian disaster involving the same jet last year.
Data from a vane-like device, called the angle-of-attack sensor, incorrectly activated the computer-controlled system, according to several people who have been briefed on the contents of the black box in Ethiopia. The system, known as MCAS, is believed to have pushed the front of the plane down, leading to an irrecoverable nose-dive that killed all 157 people aboard.
The black box, also called the flight data recorder, contains information on dozens of systems aboard the plane. The black boxes on the jets, Boeing’s latest generation of the 737, survived the crashes, allowing investigators to begin piecing together what caused the disasters. Both investigations are continuing, and no final determinations have been made.
The new connections between the two crashes point to a potential systemic problem with the aircraft, adding to the pressure on Boeing. The company already faces scrutiny for its role in the design and certification of the plane. The Federal Aviation Administration delegated significant responsibility and oversight to Boeing...
- https://www.nytimes.com/2019/03/29/b...max-crash.html
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In both causes software is attempting to prevent the stall.
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Why only 2 AOA sensors
The new connections between the two crashes point to a potential systemic problem with the aircraft, adding to the pressure on Boeing. The company already faces scrutiny for its role in the design and certification of the plane. The Federal Aviation Administration delegated significant responsibility and oversight to Boeing...
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Are you being serious? A faulty AOA vane instructs the flight control computers/stabilizer to pitch the nose down in both the Airbus and the Boeing events, overriding the pilots inputs and you fail to see the similarities. Do you work for Airbus by any chance or are you just being ignorant. In both causes software is attempting to prevent the stall.
So there is one big difference: Airbus AOA protection doesn't move the stabilizer at all: it acts on the elevators. It uses three AOA vanes with a voting system. While I am not saying at all that this implementation is the best can be built by the industry, I think it is way different from the path that Boeing has followed with MCAS