There was nothing wrong with the MCAS concept. What was wrong was its reliance on a single sensor, such that a bad sensor made it misbehave. Other things wrong with it were it had too much authority, and it should have disabled itself if the pilot was countermanding it with the control column.
The other thing wrong was the pilots not using the stab trim cutoff switch, which is supposed to be a "memory item" for them.
I worked on the design of the 757 stabilizer trim system. The cutoff switch was always the backup for things going wrong with the trim. It's right there on the console within easy reach for a damn good reason. (Other systems could be turned off by overhead circuit breakers, but the stab trim cutoff was placed in a special priority position.)
As for needing software at all, all jetliners have an active yaw damper to keep the pointy end forward. This is to counter a stability problem from having swept wings. Pilots of low&slow straight wing aircraft are often not familiar with this. A Cessna will be stable if you just let go of the controls. A swept wing jetliner, not without augmentation.
The mass media also omits the reason for the MAX. The new engines gave it 15% less fuel burn. This is massive cost savings (and less pollution, too.)
I fly an SR22, which has a yaw damper. It's not strictly necessary -- the SR22 is quite stable without it -- but I'm familiar with the concept.
The facts of the MCAS debacle have been litigated to death (literally!) and since you work in the industry you probably know more about them than I do. However, I'm still going to respectfully take issue with this:
> There was nothing wrong with the MCAS concept.
That's a vacuous claim because "the MCAS concept" is not well-defined. If "the MCAS concept" is something like "an automated control system that always does the Right Thing" then obviously there is nothing wrong with that. But MCAS was never an automated control system that always did the Right Thing. The problems with it were known -- indeed, self-evident -- long before anyone actually died. MCAS was explicitly designed to be an automated control system that sometimes did the Right Thing, and sometimes did the Wrong Thing (with a single point of failure), but that was OK because when it did the Wrong Thing, the human pilots would take over and do the Right Thing in its place [1]. I think it's pretty clear, even without the rather definitive evidence in the form of two lost aircraft, that there is quite a bit wrong with that concept. But maybe we'll just have to agree to disagree about that.
And, somewhat less respectfully...
> The new engines gave it 15% less fuel burn. This is massive cost savings (and less pollution, too.)
I'm sure the families of the victims will take great comfort knowing that their loved ones died efficiently.
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[1] UPDATE: And, I might add, that they were expected to do the Right Thing without any additional training because the whole point of MCAS was to make the new plane behave like the old plane. Which is manifestly failed at rather spectacularly. But that is neither here nor there because I think the case can be made that the "MCAS concept" was flawed even without this little detail.
> I fly an SR22, which has a yaw damper. It's not strictly necessary
The SR22 is a straight wing aircraft, not a swept wing one. "Some aircraft, such as the Boeing 727 and Vickers VC10 airliners, are fitted with multiple yaw damper systems due to their operation having been deemed critical to flight safety.[1][4]"
https://en.wikipedia.org/wiki/Yaw_damper
There have been crashes due to failure of the yaw damper and the pilot being unable to control the resulting instability.
> I'm sure the families of the victims will take great comfort knowing that their loved ones died efficiently.
We should get rid of jet airliners entirely. The whole point of jetliners was to reduce operating costs. People have died because of many flaws in jetliners. Should have just stuck to the DC-3.
Yes, the cutoff would have worked had it been activated quickly enough. The failure is insidious though.
a) When MCAS falsely activates, it only does so briefly. Then, assuming the problem is that the AoA sensor is broken, it activates again every five seconds. This is very confusing as the problem appears to have resolved and then it comes back.
b) During initial climb, other parts of the speed trim system are normally working and the trim wheel is turning and clacking with no input from the pilot. If not for the big pitch down, the extra MCAS inputs would not be otherwise noticeable.
c) The pilots had no way of knowing that MCAS even existed, because all references to it were deleted from the flight manual, so they had no way of being ready for such a set of circumstances.
d) After MCAS has activated a couple of times, if you then recognize a problem and flip the trim cutoff, you lose the manual electric trim as well, and the trim is so nose down that you don't have the physical strength to turn the trim wheels. If you turn the trim cutoff back on to try to recover control, MCAS will hit you again.
e) The procedure on previous versions of the 737 for dealing with a plane so out of trim that you couldn't turn the wheel was to pitch down even more to unload the stabilizer and then crank the trim wheel, but this procedure was also deleted from the flight manual, I believe as of the 737 Classic series.
>The mass media also omits the reason for the MAX. The new engines gave it 15% less fuel burn. This is massive cost savings (and less pollution, too.)
Sure they did. It's all over the reporting. Just from a cursory search:
>Boeing gave the Max aircraft larger engines for greater fuel efficiency"[1]
>Consequently, improving fuel efficiency has emerged as one of the major bases of competition between airline manufacturers.[2]
>Airbus announced the A320neo, a more fuel-efficient version of the A320...Boeing had to choose between short-term gain and long-term pain. The simpler option was to refurbish the 737NG with a bigger, more fuel efficient engine.[3]
>Mistakes began nearly a decade ago when Boeing was caught flat-footed after its archrival Airbus announced a new fuel-efficient plane that threatened the company’s core business. It rushed the competing 737 Max to market as quickly as possible.[4]
>That threatened to change in 2010 when Airbus introduced a version of the 320 called the Neo (for “new engine option”) that offered large improvements in fuel efficiency, range and payload. The following year, American Airlines warned that it might abandon Boeing and buy hundreds of the new Airbus models. Boeing responded with a rush program to re-engineer the 737[5]
The real issue was leadership strategy and poor process control.
The other thing wrong was the pilots not using the stab trim cutoff switch, which is supposed to be a "memory item" for them.
I worked on the design of the 757 stabilizer trim system. The cutoff switch was always the backup for things going wrong with the trim. It's right there on the console within easy reach for a damn good reason. (Other systems could be turned off by overhead circuit breakers, but the stab trim cutoff was placed in a special priority position.)
As for needing software at all, all jetliners have an active yaw damper to keep the pointy end forward. This is to counter a stability problem from having swept wings. Pilots of low&slow straight wing aircraft are often not familiar with this. A Cessna will be stable if you just let go of the controls. A swept wing jetliner, not without augmentation.
The mass media also omits the reason for the MAX. The new engines gave it 15% less fuel burn. This is massive cost savings (and less pollution, too.)