Checkout_my_Six
Touchdown! Greaser!
so....maybe your airline didn't use the AoA vane as a jetway stop?
Ethiopian Airlines Crash; Another 737 Max
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Matthew
Touchdown! Greaser!
And in the meantime the fleet is grounded.
LongRoadBob
Cleared for Takeoff
Why?
Weren't there many here coming right out and blaming the pilots? Assumptions that they weren't trained well enough, etc. Nothing concrete there.
Now we have a source, which at least major news media checks, they just don't talk to some unnamed person, they ask, do research, they just cannot reveal the source because the source wants to remain anonymous. They don't just get a telephone from someone, and take that in good faith. They interview sources, check them out, question them.
Which also fits in with grounding them, if they had already the idea that the procedure was followed.
But..ok...
Checkout_my_Six
Touchdown! Greaser!
you know this is gonna get political.......Airbus folks will blame Boeing....and the others will blame the pilots. lol
in the meantime.....no issues with the US Max operators.....crickets. And the previous Lion Air crew got "lucky".
in the meantime.....no issues with the US Max operators.....crickets. And the previous Lion Air crew got "lucky".
I know you live in Norway, so don't take this the wrong way. You may not be up on the latest information regarding the state of U.S. journalism.
FYI: most major news media will report only what they want you to know... not necessarily what you should know. Even in aviation there are background agendas, especially at this level, that get played out across all mediums. There is a lot at stake beyond the actual accident.
Andy Pasztor and WSJ in general aren’t the quality of CNN.
Matthew
Touchdown! Greaser!
There seems to be something going on, but I'm not quick enough on creating conspiracy theories to come up with a good scenario. If there was something indicated on the FDR, I would hope that Boeing and FAA are being notified so they can come up with a fix or other preventive measures. The longer this goes on, the more it looks like there are motives other than safety.
What happens when Ethiopia and the BEA folks are finished interpreting the FDR data? I *think* NTSB was assisting in extracting the data, but I don't think NTSB will be interpreting it. There will be the data points that show what happened and when, but not necessarily "why", "Why did the crew do this or that?"
I'm starting to expect one side to say, "The crew did XYZ in response to ABC, and ABC is the fault of the airplane designers" and the other side to say "ABC occurred and the crew then performed XYZ. Training dictates the crew should have done JKL after an occurrence of ABC, therefore the crew acted improperly."
What happens when Ethiopia and the BEA folks are finished interpreting the FDR data? I *think* NTSB was assisting in extracting the data, but I don't think NTSB will be interpreting it. There will be the data points that show what happened and when, but not necessarily "why", "Why did the crew do this or that?"
I'm starting to expect one side to say, "The crew did XYZ in response to ABC, and ABC is the fault of the airplane designers" and the other side to say "ABC occurred and the crew then performed XYZ. Training dictates the crew should have done JKL after an occurrence of ABC, therefore the crew acted improperly."
Larry in TN
En-Route
The procedure does not include turning the electric trim back on.
It also doesn't include retracting the flaps below 500'.
sourdough44
En-Route
Not saying this accident was in any way intentional, but we do have entities that like to steer the findings somewhat. Remember Egypt Air flight 990? To this day Egypt says it was an ‘elevator failure’, as far as I can tell. The NTSB disagrees with that.
https://en.m.wikipedia.org/wiki/EgyptAir_Flight_990
Confusing, likely yes. Was this plane flyable, yes again, Ethiopian Air.
https://en.m.wikipedia.org/wiki/EgyptAir_Flight_990
Confusing, likely yes. Was this plane flyable, yes again, Ethiopian Air.
LongRoadBob
Cleared for Takeoff
So when you follow the procedure and it doesn’t work...you mean the answer is “well, let’s just give it more time”?
Interesting release in Bloomberg. Apparently the Lion Air AOA sensor went through a CRS; implies the sensor did not operate correctly since installation after it came back from the CRS.
https://apple.news/A3Z1tgPUqRhG_7FYCiqLoNQ
https://apple.news/A3Z1tgPUqRhG_7FYCiqLoNQ
Checkout_my_Six
Touchdown! Greaser!
do you have to follow all of the procedure....and can you add other procedures to complete the procedure?
Silvaire
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yes I've been saying this from the beginning that despite the MCAS system design and training issues there is something weird about two identical AOA sensor failures on new airplanes. It's also quite possible it isn't even the sensor but something downstream that corrupts the signal. Could be as simple as an improperly crimped contact in a terminal block.
Matthew
Touchdown! Greaser!
Until the FDR info is released, we are relying on "sources say", and we've seen plenty of that in the press over the years to be justifiably skeptical.
If the procedure is "don't retract flaps below 500' ", then don't.
If the procedure is "turn off MCAS", then turn if off. If that doesn't work, you need to move on to something else, and probably not turn it back on.
Apparently FAA concedes the trim jackscrew was full nose down. Something or someone did that. Turning off MCAS, and keeping flaps extended when called for, should have prevented MCAS operation. Did it? Don't know. Were flaps retracted too soon and MCAS ran the trim full nose down? Don't know. Did the crew try to re-trim after turning off MCAS? Don't know. Did they retrim and turn MCAS back on? Don't know. Did they turn off MCAS expecting the airplane to automatically retrim back to neutral? I don't know that either, but if they turned it back on because "nothing happened", then it's possible they expected some system to take over.
A lot of times in flying, if you do something that makes things worse, undo what you just did (switching to an empty fuel tank, for example). In an airliner, it's not always that simple. If the checklist says, "MCAS - OFF", it probably doesn't say "turn it back on if nothing happens right away because the flight crew now has to take manual control and undo whatever it is that MCAS did." Dealing with what comes next is why pilots get paid. Turning off an automated system and waiting for something to happen doesn't always work, fly the airplane.
Silvaire
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There was a post earlier by an actual 737 pilot and he put it pretty succinctly - you need to follow the procedure, you can't just go rogue and start flipping switches on a hunch to see what happens. You can't make up your own procedure. In the Ethiopian case it all happened in less time than it took me to read the last post in this thread. Obviously the QRH is not designed to handle something like that.
LongRoadBob
Cleared for Takeoff
Seems like “Pilots at the controls of the Boeing Co. 737 MAX that crashed in March in Ethiopia initially followed emergency procedures laid out by the plane maker but still failed to recover control of the jet, according to people briefed on the probe’s preliminary findings“ is a good bit better than “sources say”
In that they are verifiable as people briefed on the probes preliminary findings. But sure, we wait to hear.
Not a lot waited to fault the pilots though here.
Tj1376
Pre-takeoff checklist
Flaps up at 450 agl - seems like an odd choice, no?
TJ
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Matthew
Touchdown! Greaser!
" 'sources say' (P)ilots at the controls... "
Until they are identified so they can be questioned and their stories verified, they are just "sources" even if they are described as "people briefed on the probe's preliminary findings". How preliminary were those findings? Was the briefing for those people or were they simply in the room at the same time and overheard things they don't understand?
Were the "emergency procedures laid out by the plane maker" the correct procedures for whatever was happening?
The whole system requires the proper operation of the hardware, software, and pilots. Any combination of failures of those three legs can result in fatalities. I'm a s/w guy, so I lean towards thinking the weakest link is the s/w, but I also think it's the one thing that can be disabled - turn off the automation and fly the plane.
Larry in TN
En-Route
Your premise is flawed because if they turned the electric stab trim back on then they didn't follow the procedure. The next steps are to trim the airplane manually and to leave the electric stab trim in cut out through landing.
The Ethiopian flight's problems were made worse by their decision to retract the flaps at less than 500' AGL. You would normally climb to acceleration altitude (800' to 1000' minimum), accelerate to the next flap retraction speed, then retract the flaps on schedule. You'd be 1,500' AGL, or more, before the flaps are fully retracted. Since MCAS is inhibited when flaps are not up, that would have delayed the start of the unscheduled MCAS activation until their altitude had roughly tripled. The additional altitude would have given them more time to complete complete the runaway stabilizer procedure. I'm also unclear on how they would have reached clean maneuvering speed before 500' in order to safely fly with the flaps retracted even without having any other problems. Flying clean below clean maneuvering speed would not have helped them control the airplane.
Matthew
Touchdown! Greaser!
Maybe they got spooked because they just had training telling them, "if you see the autotrim work when you don't expect it, flip these switches or you die"? That doesn't explain why flaps were retracted early. But if retracting the flaps early caused MCAS to engage (and maybe there really was no problem with the AOA at all if they were legitimately nose high), then bad things might happen.
Checkout_my_Six
Touchdown! Greaser!
....and I said it earlier....somewhere.....this is one of those things if you have to pull out the check list it ain't gonna work out. It needs to be a memory item....like runaway trim. So, here we are.....blaming the plane.
Rumor is the Preliminary Report will be out tomorrow some time.
And just as an FYI: the MCAS is not an anti-stall system. It is designed to provide consistent control column forces required per Part 25.
And just as an FYI: the MCAS is not an anti-stall system. It is designed to provide consistent control column forces required per Part 25.
I’m no expert, but how in the wide wide world of sports does intermittently applying nose down trim result in “consistent column forces?”
Greg Bockelman
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You saying CNN is better?
Greg Bockelman
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Because without that nose down trim input, the pitch force becomes lighter. The whole point of the system as I understand it is to provide for a constant column force as the power is increased.
Greg Bockelman
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And now it is a memory item. It is all a part of the runaway trim checklist.....and I said it earlier....somewhere.....this is one of those things if you have to pull out the check list it ain't gonna work out. It needs to be a memory item....like runaway trim. So, here we are.....blaming the plane.
Nope.
Greg Bockelman
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Good. The way your post was worded, I wasn’t sure.
I can see how that could happen. Back to the runaway stab trim and alleged cut out, then back on.
Generally speaking, that’s a no no. It’s been posited the crew may not have been unable to overcome the aerodynamic forces using manual trim and, as a last ditch effort, thrown it back on in a last ditch effort to get electric trim back. And then continued to get F’d at the drive thru.
I could see that chain of events occurring as the ground is getting bigger quicker and quicker.
Doesn’t make it right, but is in the realm of believable.
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Here's one explanation:
"MCAS normalises a stick force gradient that does not fully meet the applicable certification standard § 25.173 Static longitudinal stability, sub paras a through d. It is not a stall prevention mechanism. Stall warning requirements are specified in § 25.207 Stall warning and for handling in § 25.203 Stall characteristics. Compliance with the latter is exhibited in demonstration compliant with § 25.201 Stall demonstration. The lifting body effect of the engines is a non linear effect, at a modest relative inflow angle, they will develop lift, at high angles that lift increment will not occur, and inertial forces will dominate the aircrafts behaviour, weight is still forward of the Cp, the plane will pitch down at the break #.
The non linear stick force gradient issue is not permitted to be so significant that the failure of the augmentation system precludes flight within the operational envelope, and specifically up to the stall. § 25.672 Stability augmentation and automatic and power-operated systems.
In simple terms, the control force in part of the operating envelope, outside of normal flight conditions experienced by the RPT pilot, but within the full flight envelope did not meet the standard that was set half a century ago, in a time where the automation and instrumentation would have made it unacceptable to fly for a period of time an aircraft that had say the same control forces as a Lancair 360, and which are still more applicable to IFR operation than a Pitts or an Extra. The Lancair, Pitts and Extra can easily be flown by instruments, it is just undesirable for long term comfort, and therefore the system safety. To remove the issue, Bill Boeing added the MCAS, which is a variant of the STS that has been there for years on the SLUF, dealing with a similar issue in a small part of the envelope around retracting flaps and initial acceleration, e.g., 3rd segment."
Larry in TN
En-Route
They never should have been in a full nose-down trim condition (as the recovered jackscrew indicated they were).
From the DFDR data from the Lion Air accident we know that the Captain was able to stop 21 consecutive MCAS activations, and re-trim the aircraft back to a trimmed state each time, through the use of primary electric trim. That cycle could have continued indefinitely even without disabling the electric trim to stop the MCAS' trimming. They lost that "equilibrium" when the Captain transferred control to the First Officer who failed to re-trim after each of his 5 MCAS activations. Each uncorrected activation progressively drove the trim farther nose-down, eventually reaching the full nose-down position.
When the aircraft's nose is "heavy", you trim up. This happens dozens, if not hundreds, of times on every flight. It is a conditioned response that doesn't require any significant thought. If you continue to do this during an unscheduled MCAS activation then you won't be so far out of trim when the stab trim switches are thrown that you can't manually trim the airplane.
There’s a missing ‘not’ in my text you quoted. Don’t know why it wasn’t included when I wrote it, but it’s been corrected.
We also know the two AoAs were in disagreement for the entire duration of the flight, and the crew did not have that information available to the them, even though they could have had Boeing not made it optional or Lion Air paid for the upgrade.
The argument that it’s pilot error and be done with it is like saying UA262 was delayed at arrival because Sully landed it in the Hudson.
While it may be factually correct, it doesn’t tell the whole story.
Larry in TN
En-Route
The AoA displays are generally part of the HUD CAT II/III system. I don't know of any airlines that has it that doesn't also use the HUD option for CAT II/III approaches.
I'm also unsure how AoA displays would have helped either of these crews. The available data strongly suggests that they allowed the stab trim to reach its full nose-down position before disabling the electric stab trim (Ethiopian flight only). How would additional information, which wouldn't normally relate to a runaway stabilizer, help them get to the runaway stabilizer procedure any quicker? I think it's more likely to delay them longer, especially in conjunction with the stick-shaker that both flights had activating, as they're trying to figure out which AoA display is correct.
We have had three crews (two Lion Air and one Ethiopian) who failed to complete the applicable runaway stabilizer procedure in a timely fashion (without help from a jumpseater [first Lion Air]). AoA displays don't get them there faster. In depth MCAS training does not get them there faster. Raising the flaps too early (Ethiopian) certainly does not get them there faster. What gets them there faster is flying the airplane first. Trimming out the "heavy nose" and noticing that it keeps re-trimming back down on its own. That gets them there faster and with the stabilizer in a reasonable position so that they can smoothly transition to manual trim.
SWA and AA are the only airlines that purchased the option to have an AOA disagree warning in the PFD prior to the crashes.
The AoA Disagree Alert will display "AOA DISAGREE" in amber at the bottom right of the PFD if the AoA vanes disagree by more than 10 degrees for more than 10 continuous seconds.
And there was a QRH item for it if you had the option.
Part of Boeing’s response to the second crash is to make this standard for everyone.
While the pilots’ actions were contributory, the fact that on at least 26 consecutive times in the Lion Air instance, Boeing’s FCC logic was actively trying to crash the plane due to a faulty sensor and there was an ‘optional’ ability to be more readily identified and a QRH item for that is just stupid.
I’ll go back to this:
If Boeing wrote the QRH event for that, it means they knew the failure mode could occur and the severity of failure mode.
That they chose to make it an option leads to one of two conclusions:
1. The rate of occurrence for the failure mode would be low.
2. The severity of the failure mode would be low.
I’m willing to bet #1 was the choice. AOA vanes don’t have a high failure rate.
If Boeing wanted to be honest about this, they’d show fleet-wide data on A) MCAS activations vs B)failures.
While I’m willing to assume “A”>”B”, there’s only three known failures I’m aware of. And of those three, one is anecdotal, two were fatal.
So, either the assumption that 1. or 2. above is no longer valid.
Larry in TN
En-Route
United has the AOA DISAGREE warning as well.
SWA, AA, and DL use the HUD for CAT II/III approaches and all have the AOA displays (at least in the HUD). UAL uses autoland for CAT II/III and does not have the AOA display.
The AOA DISAGREE checklist in the QRH tells you that the left and right AOA vanes disagree and that you may have airspeed and altimeter errors along with their associated "IAS DISAGREE" and "ALT DISAGREE" alerts. There are no pilot actions in the checklist. I don't see how that would be helpful to pilots who are facing a stabilizer runaway. It would be one more thing distracting them from the real threat.
I have been flying airliners with AOA vanes since 1996 and have had exactly one AOA vane failure so I'd agree that failure rate is low.
If there had been any additional MCAS activations recorded by FOQA, or reported via ASAP, we'd know about them by now.
What they are sayin is... it's the pilots. This is post Lion Air. They had the instructions from Boeing for handling the emergency (which were of course the same instructions as before Lion Air), and they didn't follow them. Which means... it's the pilots.
Greg Bockelman
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LOL. Mixing incidents here?
Well, flight numbers at least. Should’ve been UA 1549.
Greg Bockelman
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Sully was USAir, not UA. Cactus.