Is a Boeing 737 MAX the safest plane in service?

I will say one thing about media coverage for this or any Boeing product, it is anti Boeing. Can you imagine if that A350 crash in Tokyo was a Boeing. They would have not been talking about how great the cabin safety material was in helping slow the fire. Instead they would have grounded the fleet for inspections of the seats due to the fire igniting at all.

 

Alaska is known for a wide variety of paint schemes. I could see them doing that.

(Yes, I understand that there is a roll of duct/speed tape in the picture)

 

600-mph tape?

 

That's the Test Director. He sits behind the pilots on the flight deck, ensuring that they fly the test profile. The guy on the right is the Ground Ops Engineer, and I'm the tall guy on the left, an Analysis Engineer manning a console in the cabin. The fellow at the head of the stairs in the background is a senior Instrumentation Engineer, responsible for the data collection system installed on the aircraft. He had recently won a million-dollar lottery (in 1982 a million dollars was a lot of money) and could have retired then and there, but chose to keep working because he loved his job in Flight Test. That was not unusual at heritage Boeing.

 

Recollections of a once storied company. Maybe someday they can regain that status. Thanks for the photos and your memories, Wiley

 

just booked flights on United... and yeah they're on 737-9.
They have some balls charging a premium for row 26 window seats.
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First one off the plane

 

"Row 26, now equipped with our patented 'pressure controlled ejector window seats', available only on a Max-9 model near you"

 

I'm becoming more and more convinced Boeing is completely lost and it will take a hero to save the company. It's probably time for the CEO and most of the Board to resign. Wholesale change.

 

Keep your seat belt firmly affixed. And if you are taking anything of value with you put it in the overhead bin.

 

Like government. Once a large company goes that far off the rails it rarely finds its way back. Besides, business schools and modern business inperatives seem to dictate quarterly profits above long term corporate health. Companies building products that are the pride of America is a dead and gone concept.

 

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Agree that this decision (from the earlier problems) was unforgivable. However, I would argue strongly that two sensors is also insufficient. There should be three -- if any sensor disagrees with the other two, it's ignored. With only two sensors, how do you know which one is wrong?

 

Yeah well, that would be what the third management turnover in a decade. Who would they get.
Boeing management needs to be engineering driven (not financial engineering) and on the shop flaw, like before, ie where planes are built, not Chicago or now Virginia. Harvard business school ruined Boeing.

As with Nuke plants, priority 1 needs to be safety not a "balance of safety and profit."

The video is 100% RIGHT. Lack of leadership, its endemic in USA. Not buying his pro union stick, they're part of a problem too.
My observation is that peopel doing the actual work care and know what to do, but they have no say. Poor leadership. Problem is your average MBA finance guy thinks leadership is something you learn in a book.

 

Like airbus then.

 

Big difference when the system is a primary flight control system. B737 is not FBW, and the system in question is not required for safe flight. On the other hand, A320 (etc) are FBW and thus the system has 3 AOA sensors.

 

You probably know it already but that's called "2 out of 3" voting and it's very common in all kinds of non-aviation but still "critical" instrumentation, even when a failure of that "1oo1" instrument couldn't result in potential loss of human life.
The cost of "2oo3" is only additional sensor(s), some additional wiring and a few extra lines of code.
There's absolutely no excuse for Boeing shipping any MCAS-equipped plane relying on data from only one AoA sensor. Whether the plane is fly-by-wire or has cables running to and fro the control surfaces.

Even if they wanted to save a few bucks with only 2 AoA sensors not 3 Boeing could have programmed a double check of AoA data vs airspeed/rate of climb/atmospheric conditions to determine if that data made sense and should be relied on to activate MCAS. Alas.

funny commentary aside, AvE did an interesting teardown of an AoA sensor:

 

Two out of three voting is old hat. Most of the digital flight control systems have four channels. That way if one goes bad, the other three can still be compared. With three channels, if one goes bad, now it is 50-50 on another failure. Select the wrong one and...

At least with two AoA or yaw probes, there is something to compare against and you get a light.

 

I can't remember hearing what changes Boeing made after the two 737-Max crashes.
Here's the FAA Airworthiness Directive: https://www.faa.gov/sites/faa.gov/files/2022-08/737_AD_2019-NM-035fr.pdf

So there's still only 2 AoA sensors but now (page 6 and 7):
- MCAS (and "Speed trim") only activates if both AoA sensors agree within 5.5degrees, only activates one time per "sensed high AoA event", and never (in theory) moves the horiz stab so much that pilots can't override the command with stick input.
- if the 2 sensors disagree >5.5 degrees, the new "Flight control laws" will "disable Speed Trim System (STS), which includes MCAS, for the remainder of the flight" (bold mine)

An indicator light is all well and good, but isn't MCAS deemed an essential safety feature to prevent stalls due the thrust/CG issues with the big turbines?
If there were 3 AoA sensors, at least MCAS could still safely operate if one sensor went down during climb-out.

 

If it were essential they wouldn’t be allowed to shut it off.

 

ok that's addressed on pages 10-12:
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In other words: "we trust the pilots to fly the plane without MCAS".

Which begs the question - why is MCAS there in the first place.

Ultimately seems like a "nice to have" feature, like automatic emergency braking or adaptive cruise control feature in some cars. As long as it doesn't disable the brakes or yank the steering wheel to one side if a wheel speed sensor goes out.

 

Here is the crazy thing -- even though Max had two sensors, it used only one of the sensors for MCAS. The even crazier thing is that Boeing did have ability to compare AoA sensors, but the "sensors disagree" warning light indicating to the pilots that there was a problem was an OPTION. With that optional warning light, both flights would have known to disable MCAS. It was inexcusable to design it to rely on only one sensor, and then 100 times more inexcusable to make the sensor failure warning light an option. (https://arstechnica.com/information-technology/2019/03/boeing-sold-safety-feature-that-could-have-prevented-737-max-crashes-as-an-option/).

 

My understanding is that MCAS was needed to avoid retraining the pilots so that the Max would fly the same as 737 even though the physics had changed significantly to accommodate the more fuel efficient engines. I remember that it was not disclosed in initial Max testing for FAA approval that Boeing had to change the control systems parameters to wild numbers to make the system work in testing. Although sensor failures caused those two accidents, it has always bothered me that Boeing had to use control parameters very far outside the expected values to make that system work. Control systems design is a very delicate balance between responsiveness and stability. You can't beat physics, and they couldn't make the control systems work properly with reasonable control parameters . Because of these parameters, I felt that they would never be able fully fix MCAS.

I didn't follow what they did to get the Max flying again after the two major incidents, but I am still of the opinion that they couldn't/didn't fully fix MCAS. All the pilots know to disable MCAS now -- which was not the case back then (because many weren't even trained on it) -- and the plane is still flyable with it disabled, so catastrophic risk has largely been eliminated.

The next thing I'm going to say is going to sound pretty crazy, but I'll say it anyway, and this is just a total guess (could very much be wrong). I still feel the same way I did back then, that it wasn't possible to solve the control systems/physics problem. If it was, they would have solved it in initial testing the first time without resorting to wild control parameters. I've flow Max's many, many times since they started flying again. One thing I've noticed in only the last few years is that landings are often quite rough, both impact wise and direction wise (feel the plane swaying left and right -- fairly slight, but prominent enough to be disconcerting). I think the MCAS system doesn't work optimally even under normal conditions. If any of this is correct (I may be dead wrong), we may see planes suffer more stress than expected for flight hours (or bolts work loose). Maybe it's just weather changes, but landings have been significantly less controlled in the last few years in my experience.

This is quite possibly senseless ramblings of somebody who could never find peace with what Boeing had to do to make MCAS work. If the physics or physical control systems had changed in the "fix", I'd probably feel differently.

 

https://www.commerce.senate.gov/2024/1/cantwell-gives-faa-2-weeks-to-provide-answers-on-its-boeing-production-line-oversight

"Nice".

 

Reading that plug-door equipped 737-9s are still grounded (possibly for a while, while FAA investigates not only the plug-door bolts but lots of other things) I checked and see the plane I'm due to fly on in 3 weeks is in the air right now.

Tail # N37408 "737-924" built in 2001 for Continental then rebranded United in 2011.
From pic below it doesn't look like there is any door/plug/potential door behind the behind the twin emergency exit rows.
All windows appear to be full sized, and the seat chart shows a full 6 seats in row 26 ("plug door row" on Alaska Airline's 737-9).
So apparently 737-9s of a certain vintage don't have the option of additional emergency exits and aren't affected by the latest grounding directive.
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Blancoliro's latest video, digging into situation at Spirit Aerospace i.e. profits over quality/safety:

Boeing 737 -9 Plug Doors and Spirit Aerospace Lawsuit (youtube.com)