So disconnect the stabilizer and run the "Jammed Stabilizer" procedure in the QRH and return to the airfield. It's not doing to move any more after the disconnect.
This is a procedure that (at least here in the US) you practice in the sim every time you go. And even before the industry knew what 'MCAS' stood for.
This is a procedure that (at least here in the US) you practice in the sim every time you go. And even before the industry knew what 'MCAS' stood for.
They should be looking at probability of failure, that's one of the rules for certification.
Found this link on DO-254.
https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/solutions/aerospace-and-defense/do-254-explained-wp.pdf
DO-254 is the HW equivalent of DO-178. 254 is mainly for FPGA/ASICs, but applies to any flight hw, per my understanding of it.
For DAL A, you need to prove better than 10-9 failure rate, a REALLY small number.
If this was DAL B, then 10-7, so a couple decimal points easier. You can use dual redundancy to get to those really low failure rates.
The outside of an AC is a really nasty environment to survive in. During takeoff/climb, it can go from very hot conditions to really cold (its well below 0F up at 30,000 ft) in a fairly short time. Plus exposed to anything in the air, as well as lightning.
So I'm also curious how they were able to do this based on one AOA, if that's what really happened.
Found this link on DO-254.
https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/solutions/aerospace-and-defense/do-254-explained-wp.pdf
DO-254 is the HW equivalent of DO-178. 254 is mainly for FPGA/ASICs, but applies to any flight hw, per my understanding of it.
For DAL A, you need to prove better than 10-9 failure rate, a REALLY small number.
If this was DAL B, then 10-7, so a couple decimal points easier. You can use dual redundancy to get to those really low failure rates.
The outside of an AC is a really nasty environment to survive in. During takeoff/climb, it can go from very hot conditions to really cold (its well below 0F up at 30,000 ft) in a fairly short time. Plus exposed to anything in the air, as well as lightning.
So I'm also curious how they were able to do this based on one AOA, if that's what really happened.
If your memory response to the situation is not correct.
Correctly trained and experienced pilots should be able to identify this and pull the plug.
Edit:6L6 made the point whilst I was still typing.
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The Associated Press:
“Boeing will make standard on all its troubled new airliner a safety feature that might have helped the crew of a jet that crashed shortly after take off last year in Indonesia, killing everyone on board.
The equipment,which had been offered as an option, alerts pilots of faulty information from key sensors. It will now be included on every 737 Max as part of changes that Boeing is rushing to complete on the jets early next week, according to a person familiar with the changes.
The person spoke in condition of anonymity because Boeing and federal regulators are still discussing details of the upgrade to the Max fleet, which is grounded worldwide after a second crash this month in Ethiopia.
The cause of the accidents has not been determined, but investigators probing the crash of the Lion Air Max jet have focused on an automated system designed to use information from two sensors to help prevent a dangerous aerodynamic stall.
In the Lion Air case, the sensors malfunctioned and gave wildly conflicting information, and the plane crashed minutes after take off. A preliminary report described a grim fight by the pilots to control the plane as it pitched downward more than two dozen times.”
It’s worth noting that at least two of the major North American Airlines with Max 8s in their fleets (Air Canada and WestJet) purchased the “safety option”, as may have many other of Boeing’s numerous worldwide customers. They may well be able to recertify their equipment once the software upgrade has been validated. In my opinion, this safety option - a sensor conflict warning alert and bypass - should have been standard from the beginning, and the costs for same should be immediately be refunded by Boeing to all who purchased it. They remain the largest manufacturer of commercial airliners in the world, and along with sizeable military contracts are still hugely profitable, and as fair as I’m concerned to do less would be unconscionable.
“Boeing will make standard on all its troubled new airliner a safety feature that might have helped the crew of a jet that crashed shortly after take off last year in Indonesia, killing everyone on board.
The equipment,which had been offered as an option, alerts pilots of faulty information from key sensors. It will now be included on every 737 Max as part of changes that Boeing is rushing to complete on the jets early next week, according to a person familiar with the changes.
The person spoke in condition of anonymity because Boeing and federal regulators are still discussing details of the upgrade to the Max fleet, which is grounded worldwide after a second crash this month in Ethiopia.
The cause of the accidents has not been determined, but investigators probing the crash of the Lion Air Max jet have focused on an automated system designed to use information from two sensors to help prevent a dangerous aerodynamic stall.
In the Lion Air case, the sensors malfunctioned and gave wildly conflicting information, and the plane crashed minutes after take off. A preliminary report described a grim fight by the pilots to control the plane as it pitched downward more than two dozen times.”
It’s worth noting that at least two of the major North American Airlines with Max 8s in their fleets (Air Canada and WestJet) purchased the “safety option”, as may have many other of Boeing’s numerous worldwide customers. They may well be able to recertify their equipment once the software upgrade has been validated. In my opinion, this safety option - a sensor conflict warning alert and bypass - should have been standard from the beginning, and the costs for same should be immediately be refunded by Boeing to all who purchased it. They remain the largest manufacturer of commercial airliners in the world, and along with sizeable military contracts are still hugely profitable, and as fair as I’m concerned to do less would be unconscionable.
(emphasis mine)
That's factual. Good job AP for getting something correct...
Once again, here I am saying (again) that we still don't know much and it's still mostly speculation. I will continue to repeat myself until it is no longer necessary.
In the absence of facts people will latch onto anything that seems plausible.
We will hopefully have some information to work from in determining what actually happened, but due to somewhat nebulous appearing reasons it seems that factual and useful information will be coming a long time from now.
Interested in the post from 6L6 when he shared a post from Greg Feith on dealing with a “runaway trim” event and wanting to find out more I picked up a medium res image of a 737 max cockpit (attached, sorry about the size but any smaller and you lose detail). Once I got over the '**** me what a lot of knobs and buttons' and reminded myself why I am eternally impressed (and grateful for) the abilities of commercial airline pilots to both multitask and think ahead to get me up and down safely and where I wanted I hunted around for information on how to disable the auto trim.
The yellow arrow points to 2 switches with what appears to be 'STAB TRIM' written above them. Apparantly those cut power to the trim motors then the pilots go back to the good old fashioned trimming method with the trim wheels.
I am still none the wiser on how a pilot spots runaway trim and we still don't know if that was a problem on this flight but I suspect these two switches will cause a lot of column inches in the coming months. From a photo behind the seats they look blinding obvious to someone on the ground, who can't fly and has never had to deal with the stress of something going badly wrong.
BTW love the huge handbrake light. Seems so 1950s yet clearly is still needed/mandated.
The yellow arrow points to 2 switches with what appears to be 'STAB TRIM' written above them. Apparantly those cut power to the trim motors then the pilots go back to the good old fashioned trimming method with the trim wheels.
I am still none the wiser on how a pilot spots runaway trim and we still don't know if that was a problem on this flight but I suspect these two switches will cause a lot of column inches in the coming months. From a photo behind the seats they look blinding obvious to someone on the ground, who can't fly and has never had to deal with the stress of something going badly wrong.
BTW love the huge handbrake light. Seems so 1950s yet clearly is still needed/mandated.
Attachments
That's a fairly uncluttered cockpit.
See the two black wheel things on the side of the center pedestal...? They will move. They even have a white stripe on them so you will see it moving in your peripheral vision. (see photo) Also the weight in your hands using or pulling the yoke will change, and if you let it get too far away that force gets to be very heavy. The trim will also make the nose of the aircraft to move up or down if you don't do anything to correct it. I.E., it's extremely obvious once it gets just a bit off where you are expecting it to be.
See the two black wheel things on the side of the center pedestal...? They will move. They even have a white stripe on them so you will see it moving in your peripheral vision. (see photo) Also the weight in your hands using or pulling the yoke will change, and if you let it get too far away that force gets to be very heavy. The trim will also make the nose of the aircraft to move up or down if you don't do anything to correct it. I.E., it's extremely obvious once it gets just a bit off where you are expecting it to be.
An externally hosted image should be here but it was not working when we last tested it.
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It's a system that keeps the stick forces feeling correct, as far as I can tell. At high power and aft CG the location of the engines is going to tend to make the pitch forces very, very light and probably no longer have a positive force gradient. You can't have that according to the rules (rightly so, as the airplane stops feeling and reacting like an airplane "should") and the MCAS is there to keep the feel gradient.
If the stick forces get too light the airplane can be pitched up very easily and a tiny stick movement can have a large effect in pitch. That's bad.
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apparently according to news reports -- it's the engines -- the older 737's had a lower rate of ascent, the new more powerful and fuel efficient GE-CFM more rapid rate of ascent. (obviously you burn a lot more fuel at take-off when fully tanked up...)
btw, NYTimes reported this morning that the pilot of the Ethiopian jet had trained on an older simulator which didn't incorporate some features of the new system.
btw, NYTimes reported this morning that the pilot of the Ethiopian jet had trained on an older simulator which didn't incorporate some features of the new system.
Yes, they were slightly larger and had to be hung a bit more forward than the original, also moving the center of trust forward. This then caused the sensitivities Jim described, making an MCAS necessary to help regain the 'airplane feeling', that there's actually a plane hanging on the stick ;-).
Jan
Jan
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Assuming that's what's actually happening.
Once again, it's not evident that the problem is with the MCAS. Things are pointing in that general direction in regards to Lion Air, but there is no clear information that says that's the actual issue. There is still no information about Ethiopia.
Once again, it's not evident that the problem is with the MCAS. Things are pointing in that general direction in regards to Lion Air, but there is no clear information that says that's the actual issue. There is still no information about Ethiopia.
All expressed concerns here, are valid as you can read.
737 MAX - MCAS
Alas, for the SW changes only, the design/implement/test/verify/approve cycle will take a minimum of two-three months, even if the change procedure had been completed prior to the second accident.
6L6 you are correct. Unfortunately the lack of operational transparency toward the pilots of the (inadequately designed) MCAs, makes for an uncertainty in timely decision-taking within a hot cockpit environment (multiple visual and aural alarms, column shaking, especially at a limited flight altitude at take off phase). You see, glass cockpit adds to the confusion with the automatic page change when a single alarming event occurs, let alone multiple concurrent alarms.
They do move. They are mechanically linked to the trimable horizontal stabilizer.
George
737 MAX - MCAS
Alas, for the SW changes only, the design/implement/test/verify/approve cycle will take a minimum of two-three months, even if the change procedure had been completed prior to the second accident.
6L6 you are correct. Unfortunately the lack of operational transparency toward the pilots of the (inadequately designed) MCAs, makes for an uncertainty in timely decision-taking within a hot cockpit environment (multiple visual and aural alarms, column shaking, especially at a limited flight altitude at take off phase). You see, glass cockpit adds to the confusion with the automatic page change when a single alarming event occurs, let alone multiple concurrent alarms.
They do move. They are mechanically linked to the trimable horizontal stabilizer.
George
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