Another (2nd) 737 Max 8 crash

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#2265695 27-Jun-2019 12:02

https://edition.cnn.com/2019/06/26/politics/boeing-737-max-flaw/index.html

New flaw discovered on Boeing 737 Max, sources say

By Shimon Prokupecz, Drew Griffin and Gregory Wallace

A new flaw has been discovered in the computer system for the Boeing 737 Max that could push the plane downward, according to two sources familiar with the testing, an issue that is expected to further delay the aircraft's return to service.

A series of simulator flights to test new software developed by Boeing revealed the flaw, according to one of the sources.

The latest versions of Boeing's popular jet were grounded in March after two crashes -- Lion Air flight 610 and Ethiopian Airlines flight 302 -- that killed 346 people.

While the crashes remain under investigation, preliminary reports showed that a new stabilization system pushed both planes into steep nosedives from which the pilots could not recover. The issue is known in aviation vernacular as runaway stabilizer trim.

Boeing announced it could break the chain of events that led to both crashes by developing a software fix that would limit the potency of that stabilization system.

In simulator tests, government pilots discovered that a microprocessor failure could push the nose of the plane toward the ground. It is not known whether the microprocessor played a role in either crash.

When testing the potential failure of the microprocessor in the simulators, "it was difficult for the test pilots to recover in a matter of seconds," one of the sources said. "And if you can't recover in a matter of seconds, that's an unreasonable risk."

Boeing engineers are now trying to address the issue, which has led to another delay in recertifying the 737 Max.

"The safety of our airplanes is Boeing's highest priority. We are working closely with the FAA to safely return the MAX to service," Boeing said in a statement.

The sources say Boeing engineers are trying to determine if the microprocessor issue can be fixed by reprogramming software or if replacing the physical microprocessors on each 737 Max aircraft may be required.

...
Boeing has proposed computer-based training which could be completed quickly and on an iPad. Pilots unions, as well as "Miracle on the Hudson" hero Chelsey Sullenberger, have said such training cannot be adequately experienced on an iPad.

The FAA is still actively considering whether more time consuming and expensive simulator training will be required, according to both sources.
...

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#2265704 27-Jun-2019 12:22

I look at this story now in the exact opposite way many others might.

Will this make the MAX one of the safest aircraft in the skies to fly on once it returns to service?

It's now seen a level of scrutiny that's potentially far beyond what any other modern aircraft has seen. While other aircraft may not have crashed, the same design processes and check systems would have occurred regardless of whether the aircraft was made by Boeing, Airbus or any other commercial manufacturer. What would be find in other aircraft is such scrutiny was applied to them?

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#2265718 27-Jun-2019 12:47

sbiddle:

I look at this story now in the exact opposite way many others might.

Will this make the MAX one of the safest aircraft in the skies to fly on once it returns to service?

It's now seen a level of scrutiny that's potentially far beyond what any other modern aircraft has seen. While other aircraft may not have crashed, the same design processes and check systems would have occurred regardless of whether the aircraft was made by Boeing, Airbus or any other commercial manufacturer. What would be find in other aircraft is such scrutiny was applied to them?

So, I am asking you this genuinely, would you have been happy to fly as a passenger on these aircraft prior to the changes being made by Boeing, knowing the "issues" with them?

Would you board one now without hesitation post changes?

Unrelated, what was your reaction to AirNZ going with Boeing this time around?

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#2265727 27-Jun-2019 13:28

networkn:

sbiddle:

I look at this story now in the exact opposite way many others might.

Will this make the MAX one of the safest aircraft in the skies to fly on once it returns to service?

It's now seen a level of scrutiny that's potentially far beyond what any other modern aircraft has seen. While other aircraft may not have crashed, the same design processes and check systems would have occurred regardless of whether the aircraft was made by Boeing, Airbus or any other commercial manufacturer. What would be find in other aircraft is such scrutiny was applied to them?

So, I am asking you this genuinely, would you have been happy to fly as a passenger on these aircraft prior to the changes being made by Boeing, knowing the "issues" with them?

Would you board one now without hesitation post changes?

Unrelated, what was your reaction to AirNZ going with Boeing this time around?

Well it wasn't really possible to fly on a MAX prior to the issues being known. I would however happily fly on a MAX once they are back in service.

As for Air NZ going with Boeing for the Dreamliner apart from the battery issue and the RR engine issue that plane has had a pretty successful 8 years since it entered service. It was hardly a surprise they'd buy more.

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#2265748 27-Jun-2019 14:39

Interesting webpage on "Runaway Stabilizer Procedure"

http://www.b737.org.uk/runawaystab.htm
...
1967-1987

The whole procedure is just 3 lines long!
...
1987-2000

After 20 years Boeing added a second memory item: “If runaway trim continues: Stabilizer Trim Wheel ______ Grasp and hold” and some helpful notes.
...
2000-2013

By the year 2000, the procedure had expanded to 4 memory items:
...
2013-Current

In 2013 the procedure changed to add in the step of disengaging the Autothrottle, and ending the procedure if disengaging the A/P stopped the runaway trim, taking it up to 5 memory items
...

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#2265942 27-Jun-2019 20:24

sbiddle:

I look at this story now in the exact opposite way many others might.

Will this make the MAX one of the safest aircraft in the skies to fly on once it returns to service?

It's now seen a level of scrutiny that's potentially far beyond what any other modern aircraft has seen. While other aircraft may not have crashed, the same design processes and check systems would have occurred regardless of whether the aircraft was made by Boeing, Airbus or any other commercial manufacturer. What would be find in other aircraft is such scrutiny was applied to them?

I still think its crazy that Boeing thought 1 angle of attack sensor was enough for such a system.

Question is if they will be allowed to fly them as they are.

The MCAS system should really have 3 angle of attack sensors to work from, not one or two. There are two sensors on the plane today, but there is no way for a computer system to figure out which one is faulty (which is probably why they didn't use both).

In a 3 sensor system, you would trust the two that give the same result (although, even a 3 sensor system could have a fault with 2 of the 3 sensors).

The A350 apparently have 4 angle of attack sensors...

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#2265947 27-Jun-2019 20:33

A sneaky news outlet used the high range mirror lens to take a peek. You can see some integral testing going on that may or may not be related.

The amusing scene is at 1:36. Few less staff parks.. (also the video still)

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#2265952 27-Jun-2019 20:44

And in the news today:

United Airlines has become the latest carrier to extend its ban on using the Boeing 737 Max after the US aviation regulator said it had identified a new potential risk with the plane.

As the Federal Aviation Administration said on Wednesday that Boeing must address the new issue before the jet can return to service, United joined American and Southwest in continuing to ground the plane through August.

...

Two people briefed on the matter told Reuters that an FAA test pilot during a simulator test last week was running scenarios seeking to intentionally activate the MCAS stall-prevention system. During one activation it took an extended period to recover the stabilizer trim system that is used to control the aircraft, the people said.

It was not clear if the situation that resulted in an uncommanded dive can be addressed with a software update or if it is a microprocessor issue that will require a hardware replacement, but Boeing has told the FAA it believes the issue can be addressed with a software upgrade.

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#2265953 27-Jun-2019 20:50

networkn:

So, I am asking you this genuinely, would you have been happy to fly as a passenger on these aircraft prior to the changes being made by Boeing, knowing the "issues" with them?

Would you board one now without hesitation post changes?

Unrelated, what was your reaction to AirNZ going with Boeing this time around?

Would I have been happy to fly as a passenger prior to the changes? Yes, but I'd be choosy about which airline I'd fly with. That applies no matter what model of aircraft I would be getting onto.

Would I board one post changes without hesitation? Ditto to the first question.

It was a no brainer that Air NZ chose more 787's. Not surprised about the change in engine supplier either, though I'm sure RR will get their engines sorted.

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Technofreak

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#2265957 27-Jun-2019 21:10

jarledb:

I still think its crazy that Boeing thought 1 angle of attack sensor was enough for such a system

I disagree. MCAS is only activated with the auto pilot off, in other words the pilot is hand flying the aircraft. He can feel what is happening directly, and take action.

The MCAS fault presents in a similar fashion to a runaway trim and the memory items for a MCAS fault are from what I can tell the same actions to be taken in the case of a runaway trim. It really doesn't matter which device is commanding the trim movement, i.e auto pilot, Mach trim, MCAS the same corrective actions apply.

jarledb:

Question is if they will be allowed to fly them as they are.

I'm sure they will. There has been no indication any extra sensors are part of the fix.

jarledb:

The MCAS system should really have 3 angle of attack sensors to work from, not one or two. There are two sensors on the plane today, but there is no way for a computer system to figure out which one is faulty (which is probably why they didn't use both).

In a 3 sensor system, you would trust the two that give the same result (although, even a 3 sensor system could have a fault with 2 of the 3 sensors).

The A350 apparently have 4 angle of attack sensors...

So how does 4 sensors fix the situation you mention where there's two faulty sensors. How does the computer figure out which two to believe?

In the case of a two sensor system the pilot is the adjudicator in deciding which one is faulty by analysing other indications. Effectively he/she is the third sensor.

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#2266073 28-Jun-2019 09:25

Technofreak, are you are Boeing employee or shareholder? If yes, I understand. If not, I'm at a loss.

You seem hell bent on blaming the pilots and training over Boeing for the two fatal accidents.

For me, I'll trust the opinion of the two truly heroic pilots who are in the rare few on this planet that have had to survive similar emergency situations over the second guessing of a non-commercial pilot.

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#2266085 28-Jun-2019 09:50

Mod's or @Batman. Any chance we could change the thread title from "Another 737 Max 8 crash - no survivors" to "Second 737 Max 8 crash - no survivors"

I keep thinking that there has been a third crash, until I remember that the thread is 3 months old...

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#2266089 28-Jun-2019 09:59

Ok will do

Technofreak

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#2266101 28-Jun-2019 10:10

dafman: Technofreak, are you are Boeing employee or shareholder? If yes, I understand. If not, I'm at a loss.
You seem hell bent on blaming the pilots and training over Boeing for the two fatal accidents.
For me, I'll trust the opinion of the two truly heroic pilots who are in the rare few on this planet that have had to survive similar emergency situations over the second guessing of a non-commercial pilot.

No I am not a Boeing employee nor a shareholder.

You haven't read all of my posts have you. Nowhere have I said Boeing are blameless, in fact I've said they have some culpability. Mainstream media seem hell bent on making this all Boeing's fault. There is ample evidence that both crews and even more so the second crew didn't follow Boeing instructions. Why? I don't know but there is only a handful of reason why they didn't.

The only "heroic"pilot I've seen quoted was Chesley Sullenberger, and he didn't express an opinion on whether or not the pilots were at fault, but expressed the view it wasn't fair to prejudge them.

You're wrong on your second guessing statement too.

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#2266223 28-Jun-2019 12:33

Technofreak:

There is ample evidence that both crews and even more so the second crew didn't follow Boeing instructions. Why? I don't know but there is only a handful of reason why they didn't.

I think there's a couple of aspects to this:

1. Why didn't they follow Boeing's instructions? They weren't willfully doing something stupid like aerobatics or low flying or anything. They were desperately trying to save their own lives and those of their passengers. I think it's safe to assume they did they best that they could. Clearly, from what they experienced they somehow decided that Boeing's instructions wouldn't work.

2. When people doing their best end up crashing, you have to look for systemic problems like inadequate training or inadequate instructions.

3. It's a standard tactic to where possible blame the pilots whenever there's a crash, because that exempts the airline and manufacturer and everyone else from damages. We only have to look at the Erebus crash to see the lengths that they will go to in falsely blaming the pilots. So any move to blame the pilots needs to be taken with a grain of salt.

4. It does seem to me that, if the aircraft was in fact airworthy and recoverable, then some intensive pilot training in the recovery procedure would have sufficed. Instead, we're seeing months of software updates and documentation reviews and so on. That says to me that it's not as straightforward as we're being led to believe.

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