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  #51  
Old 03-13-2019, 11:10 AM
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Canada has formally ordered all MAX 8s grounded.
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  #52  
Old 03-13-2019, 01:37 PM
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Looks like MAX 8 has just been grounded in the US too, per comments from POTUS.

Only twitter reports so far

https://twitter.com/W7VOA/status/1105898953034424320

Last edited by Baron Greenback; 03-13-2019 at 01:38 PM.
  #53  
Old 03-13-2019, 01:58 PM
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CNN says the same thing (reporting President's comments):
https://edition.cnn.com/world/live-n...ash/index.html
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Old 03-13-2019, 02:14 PM
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Boeing continues to have full confidence in the safety of the 737 MAX. However, after consultation with the US Federal Aviation Administration (FAA), the US National Transportation Safety Board (NTSB), and aviation authorities and its customers around the world, Boeing has determined - out of an abundance of caution and in order to reassure the flying public of the aircraftís safety - to recommend to the FAA the temporary suspension of operations of the entire global fleet of 371 737 MAX aircraft.
Some might doubt this statement.
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Old 03-13-2019, 04:40 PM
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Canada has formally ordered all MAX 8s grounded.
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Looks like MAX 8 has just been grounded in the US too, per comments from POTUS.

Only twitter reports so far

https://twitter.com/W7VOA/status/1105898953034424320
The grounding in the US came several hours after the Canadian announcement.

If I had not been following these developments I would not be aware of the level of incompetence that exists among our political leaders. As recently as yesterday the Minister for Transport Canada, Marc Garneau, was going on about how awesomely safe the 737 MAX was, and how there was no need to call for a grounding. Today's announcement was touted as being based on "new information" that he had received from his panel of experts. What new information, you ask? The exact same information that was widely known three freaking days ago! When he made the announcement Garneau cited the exact same reasoning, practically word for word!

One also wonders how come Boeing is suddenly overcome by an "abundance of caution" based on information that was available right from the start.

Last edited by wolfpup; 03-13-2019 at 04:44 PM.
  #56  
Old 03-13-2019, 04:43 PM
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A single engine failure wouldn't cause a crash though, right? What are the chances of runway FOD causing a double engine failure?



SAS Flight 751 was an engine failure caused by a software feature that the pilots didn't know about.

Though if you are saying it doesn't sound like something caused by MCAS, you have a point.
Most fatal airline crashes are a series of problems that act on each other to make things worse. A loss of engine due to FOD that causes an additional failure on top of a software issue.

Boeing is a major player in the aviation business so the US government should be all over this in terms getting to the bottom of it. This is another de Haviland Comet in every sense of the word.

We've already grounded the plane in the US so it's universally grounded. Now is the time to throw every effort into figuring it out.
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Old 03-13-2019, 05:18 PM
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Some might doubt this statement.
FAA Official: Canada just grounded your planes, making the U.S. the only country left where they can fly. Are you going to put your planes on the ground or do we have to order you to?

Boeing Official: Ummm, can you give us two hours to get back to you with an answer?
  #58  
Old 03-13-2019, 06:58 PM
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Most fatal airline crashes are a series of problems that act on each other to make things worse. A loss of engine due to FOD that causes an additional failure on top of a software issue.
I was just thinking about this possibility. It could be that the eyewitness accounts are accurate and something else started the problem, and possibly that sensor got knocked out due to fire/whatever it was, which turned an otherwise resolvable problem (e.g. land immediately) into an unsolvable problem (due to sensor/software issue).
  #59  
Old 03-13-2019, 08:10 PM
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Ethiopia has refused to send the black boxes to the US despite requests from American officials and instead have requested that France analyze them, to which France has agreed. This after their first choice, Germany, declined due to lack of proper software. No reason explicitly stated, but not hard to imagine that the Ethiopians don't trust an American analysis to be objective since Boeing is taking so much heat.

Last edited by chizzuk; 03-13-2019 at 08:11 PM.
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Old 03-13-2019, 09:13 PM
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I was just thinking about this possibility. It could be that the eyewitness accounts are accurate and something else started the problem, and possibly that sensor got knocked out due to fire/whatever it was, which turned an otherwise resolvable problem (e.g. land immediately) into an unsolvable problem (due to sensor/software issue).
Commercial pilots can correct me but auto pilot systems allow for a variety of climb options. They could be programmed for angle of climb, rate of climb etc.... While this is engaged the crew should be monitoring the flight as if they were physically controlling the plane. That means watching the heading, rate of climb, air speed and other instruments to ensure they are within their flight envelope and proper course.

It would be easy to get distracted or flat out not pay attention to what's going on because the plane is doing all of the flying. It would also be easy to over-focus on an emergency with the expectations that the plane will do it's thing while you sort out the problem. Throw a quirky bit of software into the mix and now you're fighting to control a mechanical issue made worse by software that's determined to do something you don't want it to do.

once you've crossed a threshold of control it usually takes some altitude to correct it. This flight didn't have the altitude available to fix things.
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Old 03-13-2019, 09:46 PM
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I'll acknowledge that it's way, way too early to reach serious conclusions, but it seems that the 737-Max was heavily reliant on engineering and woefully insufficient in the area of instructional design/training/user experience...which has fatal consequences.
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Old 03-13-2019, 10:08 PM
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It appears that manual override can be hard to achieve once bad AOA data starts to pitch the nose down unless one follows the cutout procedures. The Boeing Operations Manual Bulletin released after the Lion Air crash states:
In the event of erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds. The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released. Repetitive cycles of uncommanded nose down stablilizer continue to occur unless the stabilizer trim system is deactived through the use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC. It is possible for the stabilizer to reach the nose down limit unless the system inputs are counteracted completely by pilot trim inputs and both STAB TRIM CUTOUT switches are moved to CUTOUT.
This is probably the most comprehensive overview I've yet seen of the AOA and stabilizer trim system on the 737 MAX.

Note that at this point it's not established that this had anything to do with the Ethiopian crash.
I don't want to go all Trump "airplanes are too complicated", but shit like the above gives me the heebie-jeebies. Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
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Old 03-13-2019, 10:36 PM
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Originally Posted by HMS Irruncible View Post
I don't want to go all Trump "airplanes are too complicated", but shit like the above gives me the heebie-jeebies. Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
I'm curious to know how many flight hours you have logged, and in what aircraft.
  #64  
Old 03-13-2019, 10:56 PM
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I wonder if Trump will take credit for causing these crashes?
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Old 03-13-2019, 11:00 PM
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If the Ethiopean Airlines crash turns out to be caused by MCAS, then it actually is Trump's fault because it is a direct result of Trump's government shutdown.

Last edited by scr4; 03-13-2019 at 11:01 PM.
  #66  
Old 03-14-2019, 12:20 AM
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Originally Posted by HMS Irruncible View Post
Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
Actually, haven't we already done so, partially?

A friend who flies for Delta mentioned that the auto-pilot flies the plane for more time than he does. It's on most of the time during normal flights. He said he only flies during takeoffs & landings, and during bad weather or unscheduled route changes. And I believe that they are working on automating those. Many big airliners now have the technical capability for auto-landing built in.
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Old 03-14-2019, 12:26 AM
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Ethiopia has refused to send the black boxes to the US despite requests from American officials and instead have requested that France analyze them, to which France has agreed. This after their first choice, Germany, declined due to lack of proper software. No reason explicitly stated, but not hard to imagine that the Ethiopians don't trust an American analysis to be objective since Boeing is taking so much heat.
Good. The Frenchies are going to be conduct an absolutely AIR tight investigation once the boxís BUS arrives.
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Old 03-14-2019, 12:46 AM
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I don't want to go all Trump "airplanes are too complicated", but shit like the above gives me the heebie-jeebies. Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
I don't agree with this. The high level of engineering of modern airplanes is precisely why air travel is safer than it's ever been and continuing to get even better. If one makes the assumption for the sake of argument that in this instance, as with Lion Air, the flight control computer was incorrectly trimming the nose down as a response to the perceived conditions, the problem was that the perceived conditions were wrong due to bad data from the AOA sensor, not that the flight computer was faulty. On Lion Air this was compounded by apparently defective air speed indications. If the pilots don't know what's really going on, they are probably as likely to do the wrong thing as the flight computer -- maybe more likely. Which is exactly what happened on AF447. It wasn't the flight computer that did them in, it was bad information coming in to the cockpit and resultant human confusion. A jet airliner doing 630 mph at 35,000 feet over the Atlantic ocean in the darkest night in the middle of nowhere is not exactly amenable to the "seat of the pants" flying practiced by 1920s pilots in their faithful biplanes.

Here's another counterexample. If Colgan Air 3407 had automatically taken control to push the nose down instead of what the idiot pilot actually did -- which was the opposite -- it may well have landed safely instead of killing everyone on board. In fact that's exactly what the flight computer tried to do, but the pilot overrode it.

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Good. The Frenchies are going to be conduct an absolutely AIR tight investigation once the boxís BUS arrives.
I think you're mistaken in your assumptions about the scope of their responsibilities. They're doing raw data extraction. If you want to be paranoid and conspiratorial, consider that Boeing has a whole team now involved in the investigative effort. Boeing -- who declared the MAX 8 perfectly safe right up until today, when they suddenly agreed that it should be grounded "out of an abundance of caution", but only after every major country in the world had already done so.
  #69  
Old 03-14-2019, 01:04 AM
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I don't want to go all Trump "airplanes are too complicated", but shit like the above gives me the heebie-jeebies. Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
Thank god nobody has ever died because the way pilots are trained to do their jobs was faulty.
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Old 03-14-2019, 03:51 AM
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I was just thinking about this possibility. It could be that the eyewitness accounts are accurate and something else started the problem, and possibly that sensor got knocked out due to fire/whatever it was, which turned an otherwise resolvable problem (e.g. land immediately) into an unsolvable problem (due to sensor/software issue).
At that altitude I'm not sure it's possible to land an airliner in a survivable manner anywhere other than a runway or equivalent paved surface. They were either at the same height or lower than when I used to start landing procedures in small Cessnas and Pipers. It was low, damn low, and regardless of what it was that low they might have all been doomed at that point.

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Ethiopia has refused to send the black boxes to the US despite requests from American officials and instead have requested that France analyze them, to which France has agreed. This after their first choice, Germany, declined due to lack of proper software. No reason explicitly stated, but not hard to imagine that the Ethiopians don't trust an American analysis to be objective since Boeing is taking so much heat.
I'm OK with the French BEA looking at the black boxes. What's important is that that information is looked at as soon as possible because that will tell us more about what happened than eye witness accounts and kneejerk "ground them all". And why did the Ethiopians drag their feet over getting the black box data out? WTF?

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I don't want to go all Trump "airplanes are too complicated", but shit like the above gives me the heebie-jeebies. Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
We've already given it to robots.

In ordinary circumstances with routine operations and uneventful flights machines really do tend to fly better than humans. It's when the shit hits the fan that humans become the better pilots....IF they have the training and experience to do that.

And while your "heebie-jeebie" paragraph is full of jargon, it wasn't opaque to me and I'm just a piddling single-engine piston-engine pilot.

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I don't agree with this. The high level of engineering of modern airplanes is precisely why air travel is safer than it's ever been and continuing to get even better. If one makes the assumption for the sake of argument that in this instance, as with Lion Air, the flight control computer was incorrectly trimming the nose down as a response to the perceived conditions, the problem was that the perceived conditions were wrong due to bad data from the AOA sensor, not that the flight computer was faulty. On Lion Air this was compounded by apparently defective air speed indications. If the pilots don't know what's really going on, they are probably as likely to do the wrong thing as the flight computer -- maybe more likely. Which is exactly what happened on AF447. It wasn't the flight computer that did them in, it was bad information coming in to the cockpit and resultant human confusion. A jet airliner doing 630 mph at 35,000 feet over the Atlantic ocean in the darkest night in the middle of nowhere is not exactly amenable to the "seat of the pants" flying practiced by 1920s pilots in their faithful biplanes.
^ This.
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Old 03-14-2019, 05:16 AM
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Now this is interesting ...
Pilots repeatedly voiced safety concerns about the Boeing 737 Max 8 to federal authorities, with one captain calling the flight manual "inadequate and almost criminally insufficient" several months before Sunday's Ethiopian Air crash that killed 157 people, an investigation by The Dallas Morning News found. The News found five complaints about the Boeing model in a federal database where pilots can voluntarily report about aviation incidents without fear of repercussions. The complaints are about the safety mechanism cited in preliminary reports about an October Boeing 737 Max 8 crash in Indonesia that killed 189.

The disclosures found by The News reference problems with an autopilot system, and they all occurred during the ascent after takeoff. Many mentioned the plane suddenly nosing down. While records show these flights occurred in October and November, the airlines the pilots were flying for is redacted from the database.

Records show that a captain who flies the Max 8 complained in November that it was "unconscionable" that the company and federal authorities allowed pilots to fly the planes without adequate training or fully disclosing information about how its systems were different from those on previous 737 models.

(More at the link ...)
https://www.dallasnews.com/business/...ed-safety-flaw
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Old 03-14-2019, 07:06 AM
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...
I think you're mistaken in your assumptions about the scope of their responsibilities. They're doing raw data extraction. If you want to be paranoid and conspiratorial, consider that Boeing has a whole team now involved in the investigative effort. Boeing -- who declared the MAX 8 perfectly safe right up until today, when they suddenly agreed that it should be grounded "out of an abundance of caution", but only after every major country in the world had already done so.
I'm happy to have every expert in the world get access to that data. I certainly want Boeing engineers to have a team working on it.
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Old 03-14-2019, 07:58 AM
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The two incidents quoted (I didnít see links to the rest) have nothing to do with MCAS. The auto thrust failing to come up is not MCAS and MCAS is not active when the autopilot is on.

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Now this is interesting ...
Pilots repeatedly voiced safety concerns about the Boeing 737 Max 8 to federal authorities, with one captain calling the flight manual "inadequate and almost criminally insufficient" several months before Sunday's Ethiopian Air crash that killed 157 people, an investigation by The Dallas Morning News found. The News found five complaints about the Boeing model in a federal database where pilots can voluntarily report about aviation incidents without fear of repercussions. The complaints are about the safety mechanism cited in preliminary reports about an October Boeing 737 Max 8 crash in Indonesia that killed 189.

The disclosures found by The News reference problems with an autopilot system, and they all occurred during the ascent after takeoff. Many mentioned the plane suddenly nosing down. While records show these flights occurred in October and November, the airlines the pilots were flying for is redacted from the database.

Records show that a captain who flies the Max 8 complained in November that it was "unconscionable" that the company and federal authorities allowed pilots to fly the planes without adequate training or fully disclosing information about how its systems were different from those on previous 737 models.

(More at the link ...)
https://www.dallasnews.com/business/...ed-safety-flaw
  #74  
Old 03-14-2019, 08:24 AM
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...Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
As others have mentioned, we've already reached a point where most phases of flight are handled by computer. Even when flown "manually", fly-by-wire computer systems process and interpret the pilot's inputs in order to generate appropriate control surface movements; extreme control inputs are modulated to ensure that the aircraft remains within the safe flight envelope.

Allowing manual override sometimes saves an aircraft in unusual circumstances; but manual override sometimes causes accidents. When we reach a point, as we surely will, where allowing manual override is a net safety negative, the rational course is to go to full automation. For psychological reasons, this will probably happen much later than it should, and we will continue to employ people to sit in a cockpit even when they have minimal authority to override the flight computers.

Last edited by Riemann; 03-14-2019 at 08:27 AM.
  #75  
Old 03-14-2019, 08:31 AM
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Now this is interesting ...[INDENT]Pilots repeatedly voiced safety concerns about the Boeing 737 Max 8 to federal authorities, with one captain calling the flight manual "inadequate and almost criminally insufficient" several months before Sunday's Ethiopian Air crash that killed 157 people, an investigation by The Dallas Morning News found. The News found five complaints about the Boeing model in a federal database where pilots can voluntarily report about aviation incidents without fear of repercussions. The complaints are about the safety mechanism cited in preliminary reports about an October Boeing 737 Max 8 crash in Indonesia that killed 189.
To throw in some skepticism, though... it is unusual for safety concerns to be voiced about a new airplane? Is five a lot? Above average, below average? I would fully expect pilots to formally lodge safety concerns; I imagine there is, in fact, a system for doing exactly that, and that pilots are ENCOURAGED to register safety concerns, as that sort of thing is how you improve safety. So maybe this is a bad sign, but maybe it's absolutely normal. Without context and comparison, none of us know.
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Old 03-14-2019, 03:48 PM
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I'm happy to have every expert in the world get access to that data. I certainly want Boeing engineers to have a team working on it.
Absolutely. I was just pointing out how silly it was to be concerned that the organization extracting the flight recorder data was French. Data is data, and I'm sure that BEA is very competent at what they do.

Regarding the various comments about the story on 787 MAX pilots' safety concerns, I have no idea of its relevance to this accident, I just thought it was an interesting data point that others may have missed, although CNN has now picked up the story. One would certainly hope that comments about the flight manual being "inadequate and almost criminally insufficient" would not be the norm! And it seems self-evident that Boeing's Nov 6 2018 notice on the subject of potential "Ucommanded nose down stabilizer trim" problems, issued after the Lion Air accident, is something that should have been in the flight manual from the start.

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Old 03-14-2019, 05:13 PM
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I don't want to go all Trump "airplanes are too complicated", but shit like the above gives me the heebie-jeebies. Airplanes should be commanded and configured by their pilots. We're never going to give this job to robots, so just let the pilots do their jobs.
You want me to list major airline crashes caused by pilot error?

Here's a few:

Tenerife
Northwest Airlines Flight 255
Varig Flight 254
Aeroflot Flight 593

Those are just the ones off the top of my head. There are other disasters that had another root cause but the crew made bad decisions and the plane went down. Throw in near disasters like the Gimli Glider and Air transat 236, in both of which the crew made fuel calculation errors and flamed out at altitude, but landed safely.

So yea, pilots are infallible. Who needs instruments anyway? Real men (tm) fly by the seat of their pants. And always chew Beemans.
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Old 03-14-2019, 06:33 PM
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Absolutely. I was just pointing out how silly it was to be concerned that the organization extracting the flight recorder data was French. Data is data, and I'm sure that BEA is very competent at what they do.
Data may be data but extracting it is a technical process.

Germany declined to do it
:

ďThis is a new type of aircraft with a new black box, with new software. We canít do it,Ē BFU spokesman Germout Freitag said.
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Old 03-14-2019, 09:36 PM
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Huh, as the product of "stubborn Krauts", I'm surprised they'd give up so easily. I'd expect the Germans to work tirelessly until they cracked it: "You will tell us vat ve vant to know!" (whack black box with Hugo Boss riding crop)
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Old 03-14-2019, 09:59 PM
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Most fatal airline crashes are a series of problems that act on each other to make things worse. A loss of engine due to FOD that causes an additional failure on top of a software issue.

Boeing is a major player in the aviation business so the US government should be all over this in terms getting to the bottom of it. This is another de Haviland Comet in every sense of the word.

We've already grounded the plane in the US so it's universally grounded. Now is the time to throw every effort into figuring it out.
It seems to me that what Boeing did was fixing (or rather not fixing) a hardware problem with a software patch. The design of the airplane itself is flawed if throttling up can lead to an uncontrollable nose up and stall condition, that's the first problem and it's baked in.
An analogy I used elsewhere was that it's as if Boeing designed a boat with a hole in the hull and out of expediency "solved" that problem by installing a pump to keep it from sinking instead of producing a boat with no holes in the hull to begin with.

The problem as I see it is that the design is flawed and that leads to two failure modes, one the MCAS doesn't work when it should and the plane can crash because of uncontrollable pitch-up, the other MCAS works when it shouldn't and it can (and has!) cause the plane to pitch down and crash.
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Old 03-14-2019, 10:30 PM
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I think the problem was likely that there was no way to fix this particular mounting configuration for the larger, more efficient LEAP engines without a significant redesign of the whole airframe. Or just give up on the higher efficiency, which would be a non-starter from a competitive standpoint. Its competitor the A320neo already has significantly larger engines (in terms of overall diameter and fan diameter) but it also has correspondingly higher ground clearance.

I've never seen anyone claim that the 737 MAX has dangerously poor handling, only that too many pilots were not aware of the uncommanded nose down stabilizer trim issues. There are many serious questions to be answered about how this situation was allowed to happen, but with appropriate pilot training and additions to the flight manual, and the software changes currently in the works, it ought to be fine. I'm sure that what a lot of airlines are worried about is continued passenger aversion to this particular airplane even after all the fixes. And of course the big question currently hanging over everything is what the flight data recorder will reveal in this latest accident.
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Old 03-14-2019, 10:52 PM
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Article linked below has some new information with the following comment:

"Flight 302 was just three minutes into its flight, the person said, and appeared to have accelerated to even higher speeds, well beyond its safety limits."

https://www.nytimes.com/2019/03/14/w...-airlines.html
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Old 03-15-2019, 01:03 AM
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I'm not sure where this "speeds well beyond its safety limits" information is coming from. The article refers to "publicly available data", which would be this, which is also the source of the information about erratic vertical speed. Just for reference, the maximum speed shown before communication is lost at around three minutes was 383 knots at around 8500 ft MSL (but barely 1500 ft AGL, and only briefly). For comparison, I checked the track log for a typical normal 737 MAX 8 departure and after three minutes it was doing about 300 knots at about 7000 ft MSL (about 6500 ft AGL in that specific case).
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Old 03-15-2019, 03:06 AM
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The maximum speed for a B737 MAX is 340 knots (and Mach 0.82 but that is irrelevant at low altitude). On the face of it, 383 knots is indeed significantly faster than max operating. However that's not the end of the story. The speed data from Flight Radar 24, which is where your link leads, is ground speed (GS). The speed limits for aircraft are referenced to indicated air speed (IAS). The actual speed of the aircraft through the air is the true airspeed (TAS). The indicated speed will always be lower than the true speed with the error increasing with altitude. The ground speed is the true air speed plus/minus the wind.

So was it exceeding the speed limit or not? That depends on what the wind was. If it was flying at the speed limit at 8500, the true airspeed would have been around 395 knots, so a nil wind ground speed of 383 knots would actually be within the normal operating range. If there was a 50 knot headwind though, that would equate to a true air speed of 434 knots and an indicated speed of 370 knots, well in excess of the limit.

Confused? The moral of the story is that it is unwise to read too much into data from the likes of FR24 without having a very good understanding of what that data actually represents.

What I can say is that a normal indicated speed for a passenger jet at 1500 feet AGL is somewhere between 130 - 200 knots. It depends greatly on the departure profile flown, some airlines accelerate from relatively low altitudes, some from much higher. Noise abatement procedures figure heavily as well.

Last edited by Richard Pearse; 03-15-2019 at 03:07 AM.
  #85  
Old 03-15-2019, 04:04 AM
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What I can say is that a normal indicated speed for a passenger jet at 1500 feet AGL is somewhere between 130 - 200 knots.
Richard, thanks for the clarification. I was aware of the basics you describe but had completely forgotten that the speed data from all of these tracking sites are ground speed -- a fact I should have remembered well since I track flights a lot due to family travels and I have occasionally noticed flights apparently going supersonic for certain periods, simply indicative of a strong tailwind up in the jet stream!

But are you sure you meant AGL in the above comment, and not MSL? Why would Indicated Air Speed be affected by distance from the ground rather than pressure altitude (essentially, MSL)? From that perspective one notes that the Ethiopian flight was doing about 383 kts (ground speed) at about 8600 ft MSL. My reference flight at the same point of approximately three minutes elapsed (08:29:40 timestamp) was doing 304 kts (again, ground speed, to be clear) at a slightly lesser altitude (2400 m, or about 7800 ft MSL). This seems to me to be comparable speeds at similar altitudes above MSL, but as you say, the winds could have been much different. Still, I'm not sure on what basis, given the above, one could positively conclude that the flight was exceeding safe airspeed.
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Old 03-15-2019, 08:09 AM
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Most fatal airline crashes are a series of problems that act on each other to make things worse. A loss of engine due to FOD that causes an additional failure on top of a software issue.
I know next to nothing about airplanes or commercial flying, but I suspect that things ”go wrong” far more frequently than I would really want to know about.

However, I also know that there are multiple systems and back-ups and fail safes so that in the vastest majority of cases, the passengers end up safely on the ground, often not even knowing that something went awry. I include humans in as safety systems - the pilot, the ground crew, the air traffic controllers.

My amateur impression of aircraft safety is that a plane usually crashes for only two reasons: 1. A really catastrophic event, 2. Multiple system failures.

I’m guessing the Boeing Max flights went down because of case #2 - and something inherent to the aircraft is causing it. If something, anything is hindering the “safety system” known as the pilot from fixing a problem, that is very bad.

ETA : I didn’t mean to imply the pilot is just a redundant system. I mean that he or she can serve as the backup to another system gone wrong. Autopilot acting weird? Pilot flies the plane manually. Engine throws a part and breaks a window mid-flight? Pilot figures out how the get everyone on the ground with minimal loss of life.
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Huh, as the product of "stubborn Krauts", I'm surprised they'd give up so easily. I'd expect the Germans to work tirelessly until they cracked it: "You will tell us vat ve vant to know!" (whack black box with Hugo Boss riding crop)
My own stereotype of Germans is that they are practical - sometimes to the point of being a bit amusing about it.*

I’m sure the Germans would have loved to do it, but if they felt like they couldn’t do it to the highest standards for whatever reason, then it doesn’t surprise me that they would say no.


* Case in point - Angela Merkel’s remarkably efficient wardrobe. No criticism from me on that front - As a woman, I find her system quite admirable, and I’m really sort of jealous of it.

Last edited by Green Bean; 03-15-2019 at 08:13 AM.
  #87  
Old 03-15-2019, 09:05 AM
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My amateur impression of aircraft safety is that a plane usually crashes for only two reasons: 1. A really catastrophic event, 2. Multiple system failures.
My view is that accidents happen for one or more of three reasons;

1) Stuff breaks
2) People make mistakes
3) Only God controls the weather

All accidents trace back to one or more of those three.

Quote:
Iím guessing the Boeing Max flights went down because of case #2 - and something inherent to the aircraft is causing it.
The only problem is that while that's a theory to be explored it is not PROVEN. It's important to know what the actual problem(s) is(are) rather than making assumptions. Make the wrong assumption and miss the real root cause you could wind up with more accidents down the line and none of us want that.

It's possible (though, again, not proven) that the Lion crash could have been a software problem and the Ethiopian crash due to debris being sucked into the engine(s), leading to loss of control and a crash. In which case they're not the same cause and maybe the Max line of 737's is OK.

At this point we just don't know.
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Old 03-15-2019, 12:10 PM
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But are you sure you meant AGL in the above comment, and not MSL? Why would Indicated Air Speed be affected by distance from the ground rather than pressure altitude (essentially, MSL)? From that perspective one notes that the Ethiopian flight was doing about 383 kts (ground speed) at about 8600 ft MSL. My reference flight at the same point of approximately three minutes elapsed (08:29:40 timestamp) was doing 304 kts (again, ground speed, to be clear) at a slightly lesser altitude (2400 m, or about 7800 ft MSL). This seems to me to be comparable speeds at similar altitudes above MSL, but as you say, the winds could have been much different. Still, I'm not sure on what basis, given the above, one could positively conclude that the flight was exceeding safe airspeed.

I did mean AGL. During take off and subsequent climb the aircraft will become airborne at whatever the calculated indicated air speed was, letís say 140 knots (it depends on many factors including weight and flap setting), it will then climb at a slightly higher speed, eg 150 knots, to the acceleration altitude. The acceleration altitude is the altitude at which itís calculated it is safe to accelerate to a faster speed, normally 250 knots, and retract the flaps. Although it is expressed as an altitude AMSL, it is actually defined by height above the ground. Additionally, an airline will have a minimum acceleration altitude. The acceleration altitude may be higher than the minimum in order to out climb a building or hill, but it canít be lower. Where I work our min acceleration altitude is 1500í above the ground. 250 knots is then flown until any air traffic control speed restrictions cease to apply.

The initial climb profile then is all based on height above ground and you canít compare speeds of aircraft if one of them is relatively low AGL because it wonít have accelerated to its final climb speed yet.

Whether or not 383 knots is above the Vmo for the B737, it is certainly going very fast, a good 200 knots faster than would be typical for the initial climb.
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Old 03-15-2019, 05:01 PM
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My amateur impression of aircraft safety is that a plane usually crashes for only two reasons: 1. A really catastrophic event, 2. Multiple system failures.

Iím guessing the Boeing Max flights went down because of case #2 - and something inherent to the aircraft is causing it. If something, anything is hindering the ďsafety systemĒ known as the pilot from fixing a problem, that is very bad.
As I understand it the new engines change the balance enough to warrant a more aggressive stall prevention profile. It's designed to push the nose down and will stop that momentarily if the pilot uses the trim switch. It then resumes the nose-down maneuver until the pilot uses trim again. Under the right conditions It keeps doing this. The changes to the programming includes additional sensors and a limit of one cycle of the nose down-trim.

I imagine it gets a bit confusing if a pilot has to fuss with this for any length of time. It would be like fighting a ghost because of the time delay between manual trim input and counter computer trim input.
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Old 03-15-2019, 07:16 PM
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As I understand it the new engines change the balance enough to warrant a more aggressive stall prevention profile. It's designed to push the nose down and will stop that momentarily if the pilot uses the trim switch. It then resumes the nose-down maneuver until the pilot uses trim again. Under the right conditions It keeps doing this. The changes to the programming includes additional sensors and a limit of one cycle of the nose down-trim.
The problem is obvious if you look at the engines on the original 737 (https://upload.wikimedia.org/wikiped...nced_Smith.jpg) compared to the newest (https://upload.wikimedia.org/wikiped...cropped%29.jpg). The airframe was designed to support small diameter engines mounted underneath the wing, and with each new generation the engines got bigger (wider diameter turbofans are more efficient and quieter), requiring them to be mounted further forward to keep ground clearance, which changes the center of gravity, and in turn the flight characteristics, which has necessitated in the Max the software to automatically try to keep the plane in stable flight under certain circumstances.
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Old 03-15-2019, 09:27 PM
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I'm OK with the French BEA looking at the black boxes. What's important is that that information is looked at as soon as possible because that will tell us more about what happened than eye witness accounts and kneejerk "ground them all". And why did the Ethiopians drag their feet over getting the black box data out? WTF?

Really? You can't imagine why an African country with a significant Muslim majority might want to shop around and make sure the black boxes go to an impartial country, even if that takes some time?

Rather than hand them over to an American airplane manufacturer and an American government agency, and then trust that the American government agency will be impartial between the large American company and the African operators of the airline?

Seems perfectly reasonable to me that they want to make sure the investigation is carried out by a relatively neutral agency, even if it takes a bit longer to arrange.
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Old 03-15-2019, 09:57 PM
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Oops - typo - that should be "a significant Muslim minority".

Thought I'd fixed that before hitting "Reply".
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Old 03-16-2019, 02:48 AM
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The problem is obvious if you look at the engines on the original 737 (https://upload.wikimedia.org/wikiped...nced_Smith.jpg) compared to the newest (https://upload.wikimedia.org/wikiped...cropped%29.jpg). The airframe was designed to support small diameter engines mounted underneath the wing, and with each new generation the engines got bigger (wider diameter turbofans are more efficient and quieter), requiring them to be mounted further forward to keep ground clearance, which changes the center of gravity, and in turn the flight characteristics, which has necessitated in the Max the software to automatically try to keep the plane in stable flight under certain circumstances.
I don't think it's a center of gravity issue, it would be relatively easy to lengthen the fuselage aft of the wings to fix that. I think it's more of a thrust angle problem, I suspect they couldn't (or wouldn't for efficiency sake) set a thrust line that would cancel out the pitching moment of the engines when power is increased. Normally that would require the engines to point down so that the thrust vector would be as close as possible to the aerodynamic center of the airplane but doing so may A) further lower the front of the engine nacelle reducing ground clearance, B) direct the engine exhaust right into the underside of the wing and C) reduce fuel efficiency because part of the engine thrust would be spent in pushing against lift.
AFAIK most airliners with wing mounted engines pitch up when power is increased, but in this version it seems the effect is so pronounced it can overwhelm the flight controls.

I still believe the plane is intrinsically flawed because of this, like people have said here accidents are usually the result of a chain of events going wrong and this issue of the engine placement is a permanent issue with the plane that is kept in check by systems that can and have failed killing many people.
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Old 03-16-2019, 02:58 AM
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I think the problem was likely that there was no way to fix this particular mounting configuration for the larger, more efficient LEAP engines without a significant redesign of the whole airframe. Or just give up on the higher efficiency, which would be a non-starter from a competitive standpoint. Its competitor the A320neo already has significantly larger engines (in terms of overall diameter and fan diameter) but it also has correspondingly higher ground clearance.

I've never seen anyone claim that the 737 MAX has dangerously poor handling, only that too many pilots were not aware of the uncommanded nose down stabilizer trim issues. There are many serious questions to be answered about how this situation was allowed to happen, but with appropriate pilot training and additions to the flight manual, and the software changes currently in the works, it ought to be fine. I'm sure that what a lot of airlines are worried about is continued passenger aversion to this particular airplane even after all the fixes. And of course the big question currently hanging over everything is what the flight data recorder will reveal in this latest accident.
"It can't be fixed" is not acceptable, if the engine configuration leads to an airplane that makes it susceptible to losing control then they need to change that even if it means recalling all the airframes and rebuilding them. Back at the beginning of passenger jets the de Havilland Comet turned out to have a serious design flaw, the square shape of the windows caused too much concentrated stresses on the fuselage that led to two airplanes blowing up like balloons killing everyone on board. The reaction was to redesign the airplane not throwing up the arms and saying that it would be too much work to do so.

Boeing already spent the "we'll fix the software" card after the crash in Indonesia, if this new crash was caused, at its root, by the design compromises they made with the engine placement then they need to fix that root cause.
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Old 03-16-2019, 03:09 AM
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Seems perfectly reasonable to me that they want to make sure the investigation is carried out by a relatively neutral agency, even if it takes a bit longer to arrange.
Oh, I understand the political realities and the reasoning behind it... but I can still disapprove of the delay in the investigation. I am just baffled at the time delay in finding a third party. There are plenty of NTSB-equivalents around the world capable of doing the work.
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Old 03-16-2019, 04:10 AM
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It is not the thrust line. The new position of the engines causes the nacelle to create lift at high angles of attack resulting in a pitch up moment. If it was related to increasing thrust it would happen at any angle of attack. A pitch up with increasing thrust is normal behaviour for most aircraft and does not need to be designed out of an airframe.

The deal is that if you pull back on the column it should become progressively harder the more you pull. This is normal safe behaviour. What the Max was doing was decreasing the force required as the angle of attack got higher, this leads to a tendency for the aircraft to pitch further and stall. The Max could not be certified with this characteristic and Boeing opted to solve the problem by effectively disguising it with the MCAS system which artificially increases the force required by trimming in the opposite direction (nose down).

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Originally Posted by Ale View Post
I don't think it's a center of gravity issue, it would be relatively easy to lengthen the fuselage aft of the wings to fix that. I think it's more of a thrust angle problem, I suspect they couldn't (or wouldn't for efficiency sake) set a thrust line that would cancel out the pitching moment of the engines when power is increased. Normally that would require the engines to point down so that the thrust vector would be as close as possible to the aerodynamic center of the airplane but doing so may A) further lower the front of the engine nacelle reducing ground clearance, B) direct the engine exhaust right into the underside of the wing and C) reduce fuel efficiency because part of the engine thrust would be spent in pushing against lift.
AFAIK most airliners with wing mounted engines pitch up when power is increased, but in this version it seems the effect is so pronounced it can overwhelm the flight controls.

I still believe the plane is intrinsically flawed because of this, like people have said here accidents are usually the result of a chain of events going wrong and this issue of the engine placement is a permanent issue with the plane that is kept in check by systems that can and have failed killing many people.
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Old 03-16-2019, 05:02 AM
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It is not the thrust line. The new position of the engines causes the nacelle to create lift at high angles of attack resulting in a pitch up moment. If it was related to increasing thrust it would happen at any angle of attack. A pitch up with increasing thrust is normal behaviour for most aircraft and does not need to be designed out of an airframe.

The deal is that if you pull back on the column it should become progressively harder the more you pull. This is normal safe behaviour. What the Max was doing was decreasing the force required as the angle of attack got higher, this leads to a tendency for the aircraft to pitch further and stall. The Max could not be certified with this characteristic and Boeing opted to solve the problem by effectively disguising it with the MCAS system which artificially increases the force required by trimming in the opposite direction (nose down).
That's... even worse, I didn't thought it would be an aerodynamic negative stability issue.
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Old 03-16-2019, 08:59 AM
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Oh, I understand the political realities and the reasoning behind it... but I can still disapprove of the delay in the investigation. I am just baffled at the time delay in finding a third party. There are plenty of NTSB-equivalents around the world capable of doing the work.
It sounds like the German equivalent was concerned that because it's a new black box with new software, they weren't comfortable taking it on. That suggests that there wouldn't be very many safety boards with the technical capabilities to do the job.
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Old 03-16-2019, 11:48 AM
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The best summary I've seen of the situation comes from an anonymous engineer commenting in the New York Times:

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From an engineering point of view it seems to me that the bean counters have prevailed over the real engineers at Boeing. They kept on evolving a 1967 aircraft design for over 50 years, presumably to avoid the massive costs of a complete redesign, testing and certification.

The MAX 8 has pushed the 737 envelope so far that they had to mount the new, larger engines further out on the wings, otherwise they'd touch ground. However, moving the engines further out created a potential aerodynamic instability that could lead the aircraft into a stall. Rather than redesigning the wings (and incurring all the costs) they decided to use a very invasive software to automatically correct a detected stall.

Then to save even more money they decided that this software would rely on the data from two sensors (instead of three) to determine the pitch of the aircraft - thus making it impossible to determine a safe pitch in case of sensor failure. Then, to squeeze even the last dollars out of their budget, they decided not to include all these new software functions in the manuals, which would have required additional pilot training, and so on.

In summary, it seems to me that the MAX 8 is the result of the worst kind of "cost-saving engineering" that I would not accept out of a cheap plastic toy, let alone on a sophisticated aircraft that's supposed to carry millions of people safely around the world. Shame on Boeing. Their CEO and CFO should be sacked.
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Old 03-16-2019, 01:56 PM
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It is not the thrust line. The new position of the engines causes the nacelle to create lift at high angles of attack resulting in a pitch up moment. If it was related to increasing thrust it would happen at any angle of attack.
Could they have fixed the issue with a larger horizontal stabilizer, or is there more to it?
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