Author Topic: Recent Ethiopian Boeing 737 Max 8 crash - speculation  (Read 1133 times)

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Offline CarbShark

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #15 on: March 20, 2019, 09:07:23 PM »
If they disagree then I would think that it would fault the system and then not activate MCAS.

Thanks for your input, xenu.  As I understand the issue from the videos above, while it makes sense that the MCAS would have a passive fail-safe if there is a discrepancy between the two AOA sensors, that does not appear to be the case. If either of the AOA sensors indicates a stall condition, the MCAS activates and it is the pilot’s responsibility to identify the issue as a runaway stabilizer and perform the runaway stabilizer memory tasks, which include manually disabling the MCAS by turning off the motor. The pilots on the previous flight of this same plane had done precisely that.

Yes Xenu, thanks. While that is probably a good description of how it happened, it doesn't tell us much about why.

Apparently Boeing was in a hurry to get the aircraft certified, and put pressure on the FAA to speed the process.

So the FAA allowed Boeing to certify itself. In other words much of the work that the FAA used to do has been farmed out the company who assigned it's own employees to certify it's aircraft, and at the same time pressured their own employees to speed up the process.

I think this is what's meant by "regulatory capture."
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Offline CarbShark

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Offline xenu

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #17 on: March 21, 2019, 12:37:27 AM »
If they disagree then I would think that it would fault the system and then not activate MCAS.

Thanks for your input, xenu.  As I understand the issue from the videos above, while it makes sense that the MCAS would have a passive fail-safe if there is a discrepancy between the two AOA sensors, that does not appear to be the case. If either of the AOA sensors indicates a stall condition, the MCAS activates and it is the pilot’s responsibility to identify the issue as a runaway stabilizer and perform the runaway stabilizer memory tasks, which include manually disabling the MCAS by turning off the motor. The pilots on the previous flight of this same plane had done precisely that.

It should have been written up in the log book when that happened. If it was written up then I would like to know how the mechanic signed it off. The FIM said that if there was no faults in the previous flight legs on both AOA sensor then it was ok to fly and the airline was to see if it repeated on the next flight. If there was a fault then the mech was supposed to replace the faulty part. I would not want to be that guy who signed it off as checks ok.
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Offline The Latinist

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #18 on: March 21, 2019, 01:46:32 AM »
If they disagree then I would think that it would fault the system and then not activate MCAS.

Thanks for your input, xenu.  As I understand the issue from the videos above, while it makes sense that the MCAS would have a passive fail-safe if there is a discrepancy between the two AOA sensors, that does not appear to be the case. If either of the AOA sensors indicates a stall condition, the MCAS activates and it is the pilot’s responsibility to identify the issue as a runaway stabilizer and perform the runaway stabilizer memory tasks, which include manually disabling the MCAS by turning off the motor. The pilots on the previous flight of this same plane had done precisely that.

It should have been written up in the log book when that happened. If it was written up then I would like to know how the mechanic signed it off. The FIM said that if there was no faults in the previous flight legs on both AOA sensor then it was ok to fly and the airline was to see if it repeated on the next flight. If there was a fault then the mech was supposed to replace the faulty part. I would not want to be that guy who signed it off as checks ok.

The video says that there were faults on its last thre flights.  The part was replaced after the first fault and tested okay on the ground. It was cleared to fly.  The next-to-last flight the issue recurred and, as the part had already been replaced, they followed the next steps in the manual, including cleaning contacts, flushing memory, and something else I don’t recall.  It again tested fine on the ground and was cleared for its last flight.

The 737 pilot in the videos had no fault to find with the way the mechanics handled it. He said they did everything by the book. He also said the pilots on the first two flights responded correctly except that he would probably have turned the next-to-last flight around or diverted to the nearest airport rather than continuing on manual trim with three sensor conflict warnings.
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Online Desert Fox

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #19 on: March 21, 2019, 06:08:24 PM »
Daily show is talking about it
"Give me the storm and tempest of thought and action, rather than the dead calm of ignorance and faith. Banish me from Eden when you will; but first let me eat of the fruit of the tree of knowledge."
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Offline CarbShark

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #20 on: March 22, 2019, 01:24:12 PM »

Boeing charged extra for safety features. The 737 Max crashes show why that’s a bad idea - Los Angeles Times

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The passenger jets that crashed in Ethiopia and Indonesia, killing hundreds, reportedly lacked special safety features in their cockpits — features that Boeing charged extra for.
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Offline Belgarath

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #21 on: March 23, 2019, 09:44:57 AM »
So Boeing charging extra for certain safety systems is a huge thing in the news, makes a great headline and story, but Airbus (and Embraer and Canadair and British Aerospace etc) all do the same thing.  Boeing isn't alone in charging extra for some safety systems.  These things cost money and as such airlines make decisions to not include them sometimes.  If eliminating them can allow you to charge 10 cents less for a ticket, it is probably worth it, since passengers will pick a different airline for a 10 cent difference on a $200 ticket.
 
Xenu, thanks for that post.  It makes a lot of sense.   This scenario has an exact analog on the Airbus. 

We very recently had memory items added to our process for what is essentially the same problem in the A320(for the geeks among you its an Abnormal V alpha PROT scenario).  Under certain sensor/computer failure scenarios, the computers command a nose down pitch THAT CANNOT BE OVERRIDDEN by the pilot.  Generally this is a good thing because the computers are trying to keep the airplane from stalling.  If everything is working correctly, you do not want a pilot overriding this system, but sometimes computers and sensors fail.

You must immediately recognize this failure mode and turn OFF two of the three Air Data Computers computers.  Doesn't matter which ones.  This procedure will take away the computers ability to command the nose down push.  You then troubleshoot the problem and bring back online the working computers.

I can completely see a pilot who is not aware of this failure mode being COMPLETELY and UTTERLY confused and it would take some time to overcome the confusion and solve the problem.  If this were to happen close to the ground, it's game over.  I've done this procedure yearly in the simulator and even when you know it's coming ahead of time, it takes a couple of seconds to realize exactly what it is and react the right way. 999 times out of 1000 when you do something with the side stick, the airplane responds.  When the airplane doesn't respond, it takes a second to realize it and fix it.  Imagine in your car if you were driving and you pushed the brake pedal and nothing happened.  Do you know what you'd do?  Sitting reading this I'm sure you can state a number of things, but in the moment, it's going to take you some few seconds to realize the brake isn't doing anything and react appropriately.  Would you react fast enough to keep the car from crashing into something?  Maybe.   

Either way as I said in my first post, it's best to avoid speculation and wait to see what the investigation tells us. 



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Offline daniel1948

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #22 on: March 23, 2019, 11:29:25 AM »
Reacting to Belgarath's post:

1. Car companies have always charged extra for some safety features. Air bags and anti-lock brakes were not standard for a long time after they first came out. Preventive medicine is a safety feature for your body, but here in the U.S. you don't get that unless you can pay. Free-market capitalism demands that corporations minimize costs, and often that means calculating ahead of time the cost of a safety feature against the expected cost of the lawsuits when there are the inevitable injuries and fatalities if the safety feature is not included.

2. On reaction times. I quit scuba diving because I didn't think I could react fast enough in the event of an inflator valve sticking open, something that happened to a fellow diver once. And I paid for so-called "enhanced autopilot" on my Tesla Model 3 because I know that sometimes I can become momentarily distracted from the road and might not be able to react quickly enough. I do my best to stay alert at all times while driving, but EAP is an added safety feature. The less likely a scenario, the more likely it is that there will be a longer delay reacting to it. Computers have made flying enormously safer than it was, and will do the same for cars, but there will always be failures. We just have to keep working to reduce the likelihood.

I will always pay for all the safety features I can get for the activities I engage in. I want my airplane to have all available safety features. It's disturbing that for ten cents a ticket they might leave something off, but that's the world we live in. And it's not unique to Boeing.
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Offline Belgarath

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #24 on: March 30, 2019, 09:07:00 AM »
This basically explains what is going on.

https://www.nytimes.com/interactive/2019/03/29/business/boeing-737-max-8-flaws.html

Boeing is criminally negligent in my mind for configuring MCAS to rely on a single sensor.   Aircraft sensor failures are rare but regular. 

They could have mitigated this negligence by allowing the system to be disabled and TRAINING that, but I'm not sure this quote from the article is accurate:

Quote
The only permanent solution for the pilots would be to turn off the electrical system that runs the stabilizers. Either way, if the pilots don’t intervene quickly enough, the plane can go into an unrecoverable nosedive.

I highly doubt the only way to overcome this would be to turn off the stabilizers.  It's more likely that there is a method to turn off the computer that orders MCAS to activate.
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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #25 on: March 30, 2019, 09:15:04 AM »
One point I have heard numerous times is to never design an aircraft with a single point of failure whenever possible.  I believe there have been issues in the past where sensors are fed by a single Pitot tube and it gets blocked with everything going haywire as a result.
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Offline The Latinist

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #26 on: March 30, 2019, 10:27:58 AM »
Yes, it appears that the speculation was pretty much dead-on.
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Offline xenu

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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #27 on: March 31, 2019, 07:40:21 PM »

Boeing is criminally negligent in my mind for configuring MCAS to rely on a single sensor.   Aircraft sensor failures are rare but regular. 


I agree. For a system that Boeing thought was necessary because (of having to install bigger engines that would not have fit under the wings without moving them forward and pointed up) of the plane being more susceptible to a stall. Boeing added MCAS (that is not on the 737NG only on the 737MAX) to help with the new flight characteristics. They should have had some form of redundancy in the system. It sounds like Boeing was trying to get a few more bucks out of some of these airlines thinking that all of them would pay for the upgraded system.

This basically explains what is going on.


They could have mitigated this negligence by allowing the system to be disabled and TRAINING that, but I'm not sure this quote from the article is accurate:

Quote
The only permanent solution for the pilots would be to turn off the electrical system that runs the stabilizers. Either way, if the pilots don’t intervene quickly enough, the plane can go into an unrecoverable nosedive.

I highly doubt the only way to overcome this would be to turn off the stabilizers.  It's more likely that there is a method to turn off the computer that orders MCAS to activate.



I was talking to some pilots and they said that they have a flight deck warning when the system is activated on our planes. If the horizontal stabilizer was being moved by MACS and the crew turned off the system the only way to move the stabilizer back would be to hand crank it. This is no quick thing. Its this big wheel on the side of the center pedestal. With the work load of the flight crew at the time this is near impossible.
 
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Re: Recent Ethiopian Boeing 737 Max 8 crash - speculation
« Reply #28 on: April 21, 2019, 02:25:40 PM »
More issues with Boeing

https://www.nytimes.com/2019/04/20/business/boeing-dreamliner-production-problems.html

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NORTH CHARLESTON, S.C. — When Boeing broke ground on its new factory near Charleston in 2009, the plant was trumpeted as a state-of-the-art manufacturing hub, building one of the most advanced aircraft in the world. But in the decade since, the factory, which makes the 787 Dreamliner, has been plagued by shoddy production and weak oversight that have threatened to compromise safety.

A New York Times review of hundreds of pages of internal emails, corporate documents and federal records, as well as interviews with more than a dozen current and former employees, reveals a culture that often valued production speed over quality. Facing long manufacturing delays, Boeing pushed its work force to quickly turn out Dreamliners, at times ignoring issues raised by employees...

...Safety lapses at the North Charleston plant have drawn the scrutiny of airlines and regulators. Qatar Airways stopped accepting planes from the factory after manufacturing mishaps damaged jets and delayed deliveries. Workers have filed nearly a dozen whistle-blower claims and safety complaints with federal regulators, describing issues like defective manufacturing, debris left on planes and pressure to not report violations. Others have sued Boeing, saying they were retaliated against for flagging manufacturing mistakes.

Joseph Clayton, a technician at the North Charleston plant, one of two facilities where the Dreamliner is built, said he routinely found debris dangerously close to wiring beneath cockpits.

“I’ve told my wife that I never plan to fly on it,” he said. “It’s just a safety issue.”

And more

https://www.popularmechanics.com/military/aviation/a27032708/air-force-stops-deliveries-of-trash-filled-kc-46-tankers-yet-again/

Quote
The discovery of more construction debris inside KC-46A Pegasus aerial tankers has prompted the U.S. Air Force to again halt delivery of the new aircraft. The Air Force found foreign object debris, or FOD inside the planes, delivered by Boeing, that it believes could present a safety issue during flight.

According to Air Force Times the service stopped accepting planes on March 23rd, after finding construction debris inside a closed up section of one of the aircraft. This follows a similar stoppage on March 1st that was triggered by debris discovered in several airplanes, including loose tools and unwanted materials. The Air Force is concerned that such junk banging around inside aircraft during flight could cause damage, particularly to the aircraft’s electrical system, threatening the safety of the aircraft.

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