New flaw discovered on Boeing 737 Max

CNN ^ | June 26, 2019

[CondoleezzaProtege]

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.

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.

[CodeToad]

The microprocessor replacement isn’t a 1:1, it would a be a dual processor setup.

[Capt. Tom]

The microprocessor replacement isn’t a 1:1, it would a be a dual processor setup.

That would make sense and for safety reasons should have been done from day one.

Making both of the AOA sensors hooked up also should have been done from day one.

We all experience computer strange goings on, and have to restart our computers; but planes close to the ground in flight may not have the time to re-start or reboot.

To me it is the pilots who fly these planes that should be upset about the safety lapses.
Passengers can choose another type of plane. - Tom

[CodeToad]

“To me it is the pilots who fly these planes that should be upset about the safety lapses. Passengers can choose another type of plane. “

Well said, and they are.

[MeganC]

737 MAX interest ping!

I honestly didn’t expect that ANOTHER problem would surface with the new 737...I hope Boeing is thinking about an alternative to the MAX like maybe a new version of the 757 that can handle the fancy new engines.

[Revel]

Your door next door neighbor is full of crap, and completely ignorant. I would not want him flying my plane. Pretty much everything you said he said has long been picked apart as propaganda and untruth. The actual details are much more complicated than that crap.

[Revel]

Those switches completely turn off the electric trim. Including the manual electric trim buttons on the yoke. The fully manual system is slow and impossible to use under load. The plane had no means to deactivate MCAS. Only to cripple it by killing the trim motors. And that is the number one reason why those planes crashed. I know that in the second crash the pilots turned off those switches but they could not regain control of the trim. So they turned them back on to regain manual electric trim. When they did that then MCAS also regained control and crashed the plane. If they had not turned those switches back on then it is very probable that they also would have crashed(In a longer amount of time). because of where the trim already was set way off from where it needed to be.

[Celtic Conservative]

I defer to your expertise in this. Sounds like a fatally flawed system.

CC

[PAR35]

I was planning to post “In before the ‘pilot error’ Boeing cheerleaders” but it looks like I got to the thread too late.

[Capt. Tom]

I know that in the second crash the pilots turned off those switches but they could not regain control of the trim.

Long before the 737 MAX problems the 737 200-300s had tail rudder malfunction caused crashes.
And that was before the bigger engines and trim changes were made on the MAX. -Tom

[PhiloBedo]

+1

[Tucker39]

Could there be sabotage here? Find the engineer who just happened to leave Airbus and find his way to Boeing. This is starting to look a little too pat to me. Picture a few heads getting together at Airbus, and thinking up one or two slick little booby traps that could be engineered into one or more Boeing plane models, that would cause a lot of trouble before discovery. And then draw straws to see who comes to the States and applies for a job at Boeing. Crazy me!

[cba123]

I was just thinking (precisely) the same thing.

Exactly.

[Vinnie]

I read that with any kind of speed with high velocity air over the stabilizers the trim wheel is extremely difficult to turn . Could require both pilots to turn.
And with female pilots?

[logi_cal869]

“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.”

---

I’ve asked prior the rhetorical question how many Chinese-borne engineers worked on the 737MAX project for obvious reasons.

This is now officially starting to stink to high heaven and I suspect that the bureaucracy may very well collaborate with Boeing to keep the facts about this under wraps (software or hardware...either of which would give Chinese aviation builders a massive boost). This has the makings of a scandal of epic proportions.

[Revel]

Yes- You are correct.

[EVO X]

Here is a report from June 22:

https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/

[spetznaz]

Exactly. It is almost hilarious the type of spin that happens on FR. some FReepers are willing to totally give Boeing a pass, and to put all the blame on the pilots. Thing is - even if the pilots were grade school dropouts (they were not, but let’s assume they were absolutely incompetent - absolutely), and let’s assume ANY pilot with anything more sophisticated than a PPL license for flying small personal planes could fix the issues with the 737 Max (and do so half asleep and blindfolded), it would still remain that the 737 Max had bad systems that put human lives in danger.

Just because I got some training years ago on how to handle a spinning car doesn’t mean that I would be OK driving a vehicle that, at a randomly appointed time, can suddenly whip its tail around and try to do a pirouette on the freeway! Even though I can fix the issue 10 times out of 10 I would call that a sh!((y car.

But hey, nothing wrong with the 737 Max. Not one thing.

[spetznaz]

One more thing - if this was an Airbus doing this I am certain the same FReepers would be slamming AB for selling bad planes ...

I am half thinking of looking up threads on that Air France Airbus plane that took a dive over the Atlantic to see if any of the FReepers posted there, and what those posts were.

[Vinnie]

Airbus had plenty of fly-by-wire problems.
Two I can think of right now.
Chief test pilot demonstrating a new model, maiden flight. He makes a low pass over the runway, can’t pull up, crashes in the trees at the end of the runway.
He was blamed but after the dust settled it was determined a flaw in the computer.

The Air France across the S. Atlantic. Apparently the AOA or pitot tube froze up. The computer goes crazy , the pilots are at a loss as to what to do and down it goes.

Did Boeing take note of those incidents(and others)? Apparently not.
I’m a disillusioned Boeing lover guy.
And the icing on the cake. The CEO still has his job!

[Yo-Yo]

You can't, the plane cannot fly without it, due to the larger LEAP engines which changes the balance.

That is not exactly a true statement. The 737 MAX will fly just fine without MCAS.

What it won't do, however, is have the same control feel as the 737NG during a very narrow window of airspeed and angle of attack that would normally never be encountered during passenger operations.

They flew the 737 MAX during its development without an MCAS system, and that is where they confirmed wind tunnel predictions that the controls would lighten up too much when in a high speed stall situation.

The above is from this Seattle Times article that is pretty good for explaining what MCAS is supposed to do, how Boeing screwed up in its implementation, and how it needs to get fixed:

https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/

This new problem with the flight control processor is a new wrinkle that could prove much more costly and time intensive to rectify.