Author Topic: Boeing 737 MAX 8 crashes  (Read 1346 times)

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Online MarkOttawa

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Boeing 737 MAX 8 crashes
« on: March 17, 2019, 11:48:18 »
Start of detailed and lengthy Seattle Times story that is potentially devastating:

Quote
Flawed analysis, failed oversight: How Boeing and FAA certified the suspect 737 MAX flight control system

As Boeing hustled in 2015 to catch up to Airbus and certify its new 737 MAX, Federal Aviation Administration (FAA) managers pushed the agency’s safety engineers to delegate safety assessments to Boeing itself, and to speedily approve the resulting analysis.

But the original safety analysis that Boeing delivered to the FAA for a new flight control system on the MAX — a report used to certify the plane as safe to fly — had several crucial flaws.

That flight control system, called MCAS (Maneuvering Characteristics Augmentation System), is now under scrutiny after two crashes of the jet in less than five months resulted in Wednesday’s FAA order to ground the plane.

Current and former engineers directly involved with the evaluations or familiar with the document shared details of Boeing’s “System Safety Analysis” of MCAS, which The Seattle Times confirmed...


https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/

Mark
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Offline OldTanker

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Re: Boeing 737 MAX 8 crashes
« Reply #1 on: March 17, 2019, 12:39:57 »
We had our holiday to Palm Springs, which was supposed to start tomorrow, cancelled by Air Canada due to this issue. One of the legs on our flight was on a 737 MAX. Bloody inconvenient but better than making an unscheduled hard landing. Air Canada was good about refunding our money but I was disappointed they couldn't have found another aircraft.

Online MarkOttawa

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Re: Boeing 737 MAX 8 crashes
« Reply #2 on: March 17, 2019, 14:40:22 »
Plus from AvWeek:

Quote
Flight Recorder Data Links Ethiopian, Lion Air MAX 8 Crashes
...
Investigators believe faulty data from an AOA vane triggered MCAS during JT610’s flight, even though the aircraft’s nose was not too high. The flight crew responded with opposite nose-up commands, but MCAS is programmed to continue trimming nose-down based on the data it receives. With the AOA vane feeding erroneous data, MCAS kept attempting to push the 737 MAX 8’s nose down, and the pilots responded with nose-up commands. This back-and-forth continued for several minutes, causing the aircraft to lose and gain altitude, before it dove into the Java Sea, killing all 189 onboard.

A profile of ET302’s 6-min. flight based on satellite data provided to investigators by space-based ADS-B provider Aireon suggested similar flight control problems before it, too, dove to the ground. The [Ethiopian] transport minister’s statement solidifies the theory that the accidents are related...

Boeing is testing modifications to the MAX flight control system that will change how MCAS operates. FAA plans to mandate the upgrade as soon as it is validated.

Investigators’ ability to link MCAS to both accident sequences would further implicate the controversial system, which most pilots did not know existed prior to the JT610 accident and subsequent probe. But it also may expedite lifting the global MAX operations bans.

Boeing has been working on the flight control modifications for months, based on the early JT610 findings. If regulators determine the fixes and related training go far enough to reduce MCAS’s risk and improve pilots' understanding, the ban could be lifted without awaiting further progress in the ET302 probe.
https://aviationweek.com/commercial-aviation/flight-recorder-data-links-ethiopian-lion-air-max-8-crashes

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Offline BeyondTheNow

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Re: Boeing 737 MAX 8 crashes
« Reply #3 on: March 17, 2019, 15:19:08 »
We had our holiday to Palm Springs, which was supposed to start tomorrow, cancelled by Air Canada due to this issue. One of the legs on our flight was on a 737 MAX. Bloody inconvenient but better than making an unscheduled hard landing. Air Canada was good about refunding our money but I was disappointed they couldn't have found another aircraft.

Thank goodness you received a refund. I’m sorry to hear about your cancelled vacay plans though.

I had a Westjet flight affected. I received notification that they were going to bump my return flight to the following day. Not so great, as new travel and accommodation plans needed to be made. I called them and was able to get on another flight that was arriving back home on the same day as originally planned, but still had to dish out additional expenses. There was no offer of reimbursement. I understand it wasn’t the company’s fault, but still a nuisance. And yes, better than something going wrong.
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Offline Good2Golf

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Re: Boeing 737 MAX 8 crashes
« Reply #4 on: March 17, 2019, 16:19:08 »
Start of detailed and lengthy Seattle Times story that is potentially devastating:
(article details)
Mark
Ottawa

Some serious issues regarding the horizontal stabilizer's limit of travel under MCAS control, than in some cases exceeded the original FAA approved limit by more than four times.  The fact that some of the FAA's final certification approval team we unaware of Boeing's increased control authority is an issue.

Additionally, it appears that information pertaining to certain modes of the MCAS is somewhat limited within the Aircraft Flight Manual, giving little information to aircrew regarding the specific modes and limitations of the system.  An interesting article in the Atlantic related to aircrew self-reporting of MAX 8 control issues using NASA's anonymous ASRS (Aviation Safety Reporting System).

Here’s What Was on the Record About Problems With the 737 Max
by James Fallows
14 March 2019
Quote
As mentioned in two previous reports—a long one, and a short one—some things are known, and many are not, about the horrific crash this past weekend outside Addis Ababa, in which all 157 people aboard a new-model Ethiopian Airlines 737 Max were killed.

One thing that’s known: This is the second crash of this kind of plane within the past five months, following the Lion Air crash in Indonesia last year.

One thing that’s not known: whether the two crashes are related, which would suggest a disastrous system flaw with the 737 Max and its software.

Just this afternoon—minutes ago as I type, four days after the Ethiopian crash— aviation authorities in the United States and Canada joined their counterparts in Europe and Asia in grounding the 737 Max fleet. This is until more is known about whether the crashes are connected and whether there is something systematically wrong with the plane.
...
What will happen with the 737 Max? At this point, again, no one knows—or has said publicly. As a practical matter, grounding all Boeing 737s would have an enormous effect on world air travel, since they’re the most popular airliners on Earth, with a production run of well over 10,000. Although more than 5,000 orders have been placed for the 737 Max series, only a few hundred of them have gone into service, fewer than 100 with U.S. carriers. Most airlines can cancel those Max flights without fundamentally disrupting their service.
...
Boeing, like Airbus, has earned trust for decades’ worth of safe decisions. The FAA, like most of its counterparts, has earned similar trust for its safety-mindedness—despite endless grievances from pilots, airlines, and aircraft companies about aspects of FAA bureaucracy. If either Boeing or the FAA is making the wrong choices now, the airline-safety culture will certainly recover—but their reputation and credibility might not, for a very long time.

While the fundamentals remain unknown, here are some relevant primary documents. They come from an underpublicized but extremely valuable part of the aviation-safety culture. This is a program called ASRS, or Aviation Safety Reporting System, which has been run by NASA since the 1970s. That it is run by NASA—and not the regulator-bosses at the FAA—is a fundamental virtue of this system. Its motto is “Confidential. Voluntary. Nonpunitive.”

The ASRS system is based on the idea that anyone involved in aviation—pilots, controllers, ground staff, anyone—can file a report of situations that seemed worrisome, in confidence that the information will not be used against them. Pilots are conditioned to treat the FAA warily, and to make no admissions against interest that might be used again them. What if I confess that I violated an altitude clearance or busted a no-fly zone, and they take away my certificate? But they’ve learned to trust NASA in handling this information and using it to point out emerging safety problems. I’ve filed half a dozen ASRS reports over the years, when I’ve made a mistake or seen someone else doing so.
...
Below are all of the reports I could find that are related to possible runaway-trim problems with the new 737 Max. As a reminder, that is the presumed cause of the Indonesian Lion Air crash, and possibly a factor in the accident in Ethiopia. I won’t annotate or parse them, but I offer them as the documentary supplement to what you’ll read about in the papers.

The first four reports involve the aspect of the 737 Max software most in the news: its MCAS program that automatically lowers the nose of the plane, even if the pilot does not want the plane to descend. In these cases, it is worth noting, these U.S.-carrier pilots disabled or overrode automated systems and took control of the plane themselves. Obviously none of these flights crashed.

Here we go. Most readers will want to skip to “Narrative” and “Synopsis,” but I have left in all the other information just for the record:
[a number of ASRS reported incidents related directly to 737 MAX trim runaway situations]
...
That’s what is on the record, from U.S. pilots, about this plane. If I’ve missed any relevant 737 Max reports among the many thousands in the ASRS database, I assume someone will let me know about them. We’ll see where the evidence leads.

Here is another highly relevant offering for the day. It comes from J. Mac McClellan, a longtime writer and editor in the flying world, at the Air Facts site. He argues that Boeing may have been assuming that pilots would note any pitch anomaly, and override it if it occurred (as appears to have happened in the incidents involving U.S.-carrier pilots that were reported in ASRS). His whole article, about how airlines manage the complexities of automated and human flight guidance, is worth reading.

In the article, called “Can Boeing Trust Pilots?,” McClellan writes:
Quote
What’s critical to the current, mostly uninformed discussion is that the 737 MAX system is not triply redundant. In other words, it can be expected to fail more frequently than one in a billion flights, which is the certification standard for flight critical systems and structures.

What Boeing is doing is using the age-old concept of using the human pilots as a critical element of the system ... In all airplanes I know of, the recovery is—including the 737 MAX—to shut off the system using buttons on the control wheel then a switch, or sometimes circuit breaker to make a positive disconnect.

Though the pitch system in the MAX is somewhat new, the pilot actions after a failure are exactly the same as would be for a runaway trim in any 737 built since the 1960s. As pilots we really don’t need to know why the trim is running away, but we must know, and practice, how to disable it.

Boeing is now faced with the difficult task of explaining to the media why pilots must know how to intervene after a system failure. And also to explain that airplanes have been built and certified this way for many decades. Pilots have been the last line of defense when things go wrong
...
But airline accidents have become so rare I’m not sure what is still acceptable to the flying public. When Boeing says truthfully and accurately that pilots need only do what they have been trained to do for decades when a system fails, is that enough to satisfy the flying public and the media frenzy?


It will be interesting to see what the fix will be, but I would think that it would no only need some type of flight control system modification, but also more information available to aircrew both during training and during operations (Flight Manual) related to the operation of the MCAS portion of the MAX's FCS.

Regards
G2G

Offline kev994

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Re: Boeing 737 MAX 8 crashes
« Reply #5 on: March 17, 2019, 16:52:46 »
C130J has 2 AoA vanes, if they disagree then the stick pusher is disabled and you get an associated warning. Sounds like something like this would work.

Offline Good2Golf

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Re: Boeing 737 MAX 8 crashes
« Reply #6 on: March 17, 2019, 17:03:13 »
C130J has 2 AoA vanes, if they disagree then the stick pusher is disabled and you get an associated warning. Sounds like something like this would work.

MAXs do have two vanes, but MCAS was taking a feed only from one, Kev.  The article surmises that a s/w fix will include polling both AOA vanes.  Also, the single-cycle pusher would go a long way to easing the pilots' ability to respond to and control the situation.

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Re: Boeing 737 MAX 8 crashes
« Reply #7 on: March 17, 2019, 21:52:35 »
Start of detailed and lengthy Seattle Times story that is potentially devastating:

Mark
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Thanks for this link. Devastating is an understatement. If the information is to be believed, and I think that it can be, then there should be a parallel FBI investigation of criminal negligence within both Boeing and the FAA.

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