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Old 03-20-2019, 05:35 PM   #141
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I don't see it as dark as that. I do failure analyses as part of my business (certainly nothing related to aero). You want to consider whether there is any potential "conflict of interest" when you arrange parties to do an analysis. There is potential for such a conflict with at least Boeing in this incident. I see nothing out of sorts about having the French take the lead.

The Ethiopians did trust Boeing enough to buy their aircraft.
The aircraft were probably ordered at least 5 years ago, plenty of time to become disillusioned. Can anyone remember when anyone except Boeing and the FAA were NOT leading the investigation of a Boeing crash? I cannot, although it may have happened before now. The fact that they took the cvr and fdr away from FAA for analysis is not trivial and should not be minimized. It takes a long time to earn trust and even longer to get it back once it is lost.
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Old 03-20-2019, 06:32 PM   #142
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https://www.abc.net.au/news/2019-03-...ashed/10922820.
Interesting,and sad. Spare a thought for the passenger experiences during the extended period of atypical aircraft behavior before the crash, they must have been terrified, whatever the cause.
Now I expect attention centres on the comparison of the recordings from the Ethiopian crash.
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Old 03-20-2019, 06:42 PM   #143
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Some of this doesn't pass a smell test. The idea that unless the pilots turned off the automated systems the Max would crash itself, Boeing knew, and chose to do nothing about it. There's gotta be more to this story.



Yes, there is much more to the story. Just read this thread which is full of mostly unbiased information about the planes, training, and all sort of related stuff. So far it seems like there are lots of issues spread over many parties conspiring to cause two accidents.
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Old 03-20-2019, 09:11 PM   #144
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The aircraft were probably ordered at least 5 years ago, plenty of time to become disillusioned. Can anyone remember when anyone except Boeing and the FAA were NOT leading the investigation of a Boeing crash? I cannot,.
The F.A.A. and Boeing never lead these investigations. In a domestic crash it will be lead by a team of subject-matter experts from the NTSB, a n organization historically more than willing to criticize the F A A and aircraft manufacturers.

The investigator -in-charge has the authority to accredit parties to the investigation, and there will be a dozen or more, standing by to provide expertise. I served as an F A A rep on several of these, though only one involving a Part 121 carrier, CO1713 at Denver, and I can assure you we spoke when asked to. On more than one occasion, "parties" have been discharged for actions seen to compromise The investigation.

The F A A never reads out the F.D.R. nor the C.V.R. the N.T.S.B. does in a very sophisticated lab at L'Enfant Plaza.

The Ethiopian investigation will be "lead" by someone from the E.C.A.A., a notoriously feeble institution, but he will have a lot of assistance to draw on, including Boeing, but almost certainly not the F.A.A.
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Old 03-20-2019, 10:22 PM   #145
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Interesting discussion on the topic with a 20 year 737 pilot (also flew 737 Max) at my North Saanich marina: "Pilots rely on too much automation (ie; auto pilot with trim tabs)". When things begin to go sideways switch off the automatic functions. The auto nose down MACS system was introduced with little-to-no training or notification. Shutting down the autopilot function should have been their first reaction to an out-of-order flight situation. Fly the plane.

Your friend is broadly correct, the automation has come to interfere with basic airmanship. It's a standing joke in airline circles: "I no longer know how to fly the airplane...but I can type 80 words-per-minute".


But this case is almost exactly the opposite. We already know that the Lion Air crew was flying the airplane by hand and attempted the same ineffectual "low tech" solution 26 times. Had they turned on the autopilot, it would have disabled the MCAS and ended the event.



The alternate solution was "lower tech", reach over by the engine thrust levers, turn off the electric trim and use the big black trim wheel right beside your seat, which is the documented and trained remedy for "uncommanded pitch change."
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Old 03-20-2019, 10:24 PM   #146
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To be clear, "shutting off the automation" only means disconnecting the autopilot and the autothrottles. The plane then can be flown "manually".

In the 737 this really means that the pilot is flying the airplane via the cables to the control actuators. In an Airbus aircraft even with the autopilot and autothrottles disengaged, the pilot is still flying the plane via a computer. It's just that the control inputs to the computer come from a human, not another computer.

In the case of the MAX "shutting off the automation" will not prevent the MCAS from working. MCAS only works if the auto flight system is OFF.

In the 737 switching off the trim systems will cause the autopilot to disengage if it is engaged when the trim is turned off. If the A/P trim system is off, the autopilot cannot be engaged.

Switching off the trim systems will prevent the MCAS from working because power is removed to operate the trim actuator jackscrew.

FWIW, https://www.cnn.com/2019/03/20/busin...nas/index.html
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Old 03-20-2019, 10:36 PM   #147
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... Had they turned on the autopilot, it would have disabled the MCAS and ended the event...."
Except that by then the plane was probably too far out of trim for the autopilot to engage. Autopilot will only engage if the aircraft is already in trim and no one is pulling on the control column.
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Old 03-20-2019, 10:49 PM   #148
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Except that by then the plane was probably too far out of trim for the autopilot to engage. Autopilot will only engage if the aircraft is already in trim and no one is pulling on the control column.

oh.
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Old 03-20-2019, 10:52 PM   #149
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Except that by then the plane was probably too far out of trim

One question I keep forgetting to ask my "expert" who is flying this airplane...or was until last week:


When the MCAS activates, does the trim wheel roll down?
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Old 03-20-2019, 11:03 PM   #150
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It borders on word games to say that automation is shutdown but the plane still automatically adjusts trim. Especially when the automatically adjusted trim can automatically crash the plane while automation is shutdown.


To a pilot who missed this distinction and thought he had control, didn't understand that MCAS was another layer of automation, and was fighting a "demon" for control of the aircraft, it was an ugly end. The voice recorder would tell this story.

I have said it before, not really meaning it, but it sounds like we have reached the point where it takes more attention and hands-on control to drive a bus.


I wonder how many Boeing coders would rather be writing video games?
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Old 03-21-2019, 06:56 AM   #151
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The F.A.A. and Boeing never lead these investigations. In a domestic crash it will be lead by a team of subject-matter experts from the NTSB, a n organization historically more than willing to criticize the F A A and aircraft manufacturers.

The investigator -in-charge has the authority to accredit parties to the investigation, and there will be a dozen or more, standing by to provide expertise. I served as an F A A rep on several of these, though only one involving a Part 121 carrier, CO1713 at Denver, and I can assure you we spoke when asked to. On more than one occasion, "parties" have been discharged for actions seen to compromise The investigation.

The F A A never reads out the F.D.R. nor the C.V.R. the N.T.S.B. does in a very sophisticated lab at L'Enfant Plaza.

The Ethiopian investigation will be "lead" by someone from the E.C.A.A., a notoriously feeble institution, but he will have a lot of assistance to draw on, including Boeing, but almost certainly not the F.A.A.


Thank you for dismissing certain conspiracy theories as nothing more than someone massively miss informed.

This thread has been an incredibly refreshing dose facts and information with minimal opinion and drama. This is how we all learn, where one is so inclined.
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Old 03-21-2019, 08:13 AM   #152
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Yes it is called a stabilator and I believe the above reference to a jackscrew which moves it is misleading. The MD 80 for example works that way. On the 737, the control inputs from the yoke or the autopilot go to the trim tab which basically exerts an aerodynamic force shoving the freely swiveling stabilator where you want it.


Then a small "trim jackscrew" balances the forces so the system achieves a new stable state. This is the bit which was found set "full nose down".
So to be clear, the "stabilator" (aka horizontal stabilizer or elevator, the whole horizontal large surface) on the 737 Max is free floating on its pivot and is only moved by aero forces from the trim tabs? No big jackscrew machine operating the stabilator? Just little jackscrews operating the tabs? This seems counter to what XSbank posted.

I understand the Alaska Airlines crash in the Pacific was caused by a stripped/jammed jackscrew mechanism which controlled the whole stabilator?

So when you pull or push on the yoke it only controls the trim tabs, or does it move the stabilator? If the stabilator is controlled with the jackscrew, then where would the 100lb of force on the yoke come from? Seems there would be no feedback to the yoke if all it did was command the JS motor.

Not sure how relevant this is to the topic, but when trying to pick through a failure I like to have a clear mental image of the machinery.
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Old 03-21-2019, 10:11 AM   #153
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So to be clear, the "stabilator" (aka horizontal stabilizer or elevator, the whole horizontal large surface) on the 737 Max is free floating on its pivot and is only moved by aero forces from the trim tabs? No big jackscrew machine operating the stabilator? Just little jackscrews operating the tabs? This seems counter to what XSbank posted.



I understand the Alaska Airlines crash in the Pacific was caused by a stripped/jammed jackscrew mechanism which controlled the whole stabilator?



So when you pull or push on the yoke it only controls the trim tabs, or does it move the stabilator? If the stabilator is controlled with the jackscrew, then where would the 100lb of force on the yoke come from? Seems there would be no feedback to the yoke if all it did was command the JS motor.



Not sure how relevant this is to the topic, but when trying to pick through a failure I like to have a clear mental image of the machinery.


Hello, longtime lurker and current 737 pilot here.

The 737 does not have a “stabilator” like a piper Cherokee, it has a trim-able tailplane or stabilizer. The aft end of the stabilizer is a hinge and the leading edge is trimmed up and down with a jackscrew.

This jackscrew is motor driven until the flightcrew elects to disconnect it by use of the much discussed switches just aft of the first officers trim wheel, then the jackscrew can be manually turned by the conventional trim wheel.

The 737 still has conventional elevators which are actuated by hydraulic servos which are in turn controlled by a complicated collection of cables, bellcranks, feel generators, etc... Additionally these elevators have “servo” or “balance” tabs on their very trailing edge. These are aerodynamic devices which move in the opposite direction of the elevator to aerodynamically lighten the load of the elevator.

Alaska’s MD80 on flight 261 had a similar system, conventional elevators and a trim-able stabilizer which failed due to a maintenance error, very sad story that one.
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Old 03-21-2019, 01:33 PM   #154
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Thanks, that clears things up.
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Old 03-21-2019, 03:15 PM   #155
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The 737 does not have a “stabilator” like a piper Cherokee, it has a trim-able tailplane or stabilizer. The aft end of the stabilizer is a hinge and the leading edge is trimmed up and down with a jackscrew.
...

...
Alaska’s MD80 on flight 261 had a similar system, conventional elevators and a trim-able stabilizer which failed due to a maintenance error, very sad story that one.

Thanks, I stand corrected.
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Old 03-22-2019, 12:45 AM   #156
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The 737 jackscrew and drive mechanism is about 6' long (give or take). The jackscrew itself is a couple of inches in diameter.

Video showing it working:



Big metal beams in the video is the connection to the stabilizer itself.
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Old 03-25-2019, 05:56 PM   #157
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What`s happening? Must be a lot of parked aircraft not earning $ still requiring lease or other financial resources, and disrupted schedules.
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Old 03-25-2019, 06:24 PM   #158
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What`s happening? Must be a lot of parked aircraft not earning $ still requiring lease or other financial resources, and disrupted schedules.
Boeing is still working on an aircraft change and a training update. It all has to be tested and approved. Boeing has already had a problem with unintended consequences. Probably making *am*** sure it doesn't happen again. The FAA is probably also looking at it very closely too.

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Old 03-25-2019, 06:26 PM   #159
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The 737 jackscrew and drive mechanism is about 6' long
Okay. Here's the enigma: In my years in the F.A.A., in addition to my 2200hours of "little airplane" time, I've got 200 or 300 hours watching the pros fly everything from DHC-7s to Tri-Stars. (wish I'd logged all that learning!).

More than half that time in Boeing 7-somethin' and I can tell you the pitch - trim is impossible to ignore. Not only is there a huge black and white wheel (x2) whirling around a few inches from your thigh, it is NOISY.

There's a lot of talk about the lack of alerting system, but I gotta say that if every time the airplane tries to pitch down that big NOISY wheel spins around, it isn't gonna take long before I shout, "For the love of (insert Diety of choice), shut that frapping thing off!! "

How much alerting is required by an 8000 hour pilot?
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Old 03-25-2019, 06:43 PM   #160
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Okay. Here's the enigma: In my years in the F.A.A., in addition to my 2200hours of "little airplane" time, I've got 200 or 300 hours watching the pros fly everything from DHC-7s to Tri-Stars. (wish I'd logged all that learning!).

More than half that time in Boeing 7-somethin' and I can tell you the pitch - trim is impossible to ignore. Not only is there a huge black and white wheel (x2) whirling around a few inches from your thigh, it is NOISY.

There's a lot of talk about the lack of alerting system, but I gotta say that if every time the airplane tries to pitch down that big NOISY wheel spins around, it isn't gonna take long before I shout, "For the love of (insert Diety of choice), shut that frapping thing off!! "

How much alerting is required by an 8000 hour pilot?
The amount of noise the trim system makes is a function of how old the hardware is. An old one will make a lot of noise when is starts and stops due to wear causing things to loosen up a bit. It'll clank when it starts and clank when it stops (among other noises). On a new airplane, it will make much less noise because things are tight. The white stripes on the wheels are meant to be a visual indicator trim movement. When the flaps are up (MCAS territory) the trim moves a lot slower (and more quietly) than when the flaps are not up.

Planes without the big wheels have artificial warning systems to let you know the trim is in motion (e.g. MD-80s).

The problem is that anyone with more than a few dozen hours in the 737 probably doesn't notice the noise anymore.

Since the MCAS only works in manual flight, a big clue that something is wrong should be the fact that the force on the control column is pulling the thing away from the pilot and when he trims the force off it keeps coming back.
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