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Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

nytimes.com

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Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#231

Post by mannykannot »

nopzor wrote: post #104
na85 wrote: post #99

Earlier quoted context omitted.

The hardware isn't faulty. The problem is the way Boeing tried to achieve a zero training delta so pilots wouldn't have to get a second type rating.

the airplane did not have stable flight characteristics because of its physical design. that’s a hardware problem. MCAS only exists because of that hardware problem. the fact that boeing also did not train or tell pilots about MCAS, in order to make the airplane more financially appealing by retaining the 737 type rating, is a separate (also bad) issue.

Even the 737 Max variants are statically stable in pitch, at least up to the stall. The issue that MCAS was intended to address was the handling characteristics, again in the flight regime prior to the stall. I do not know whether the airplane could have been certified, as a separate type, without some sort of augmentation, but it seems that Boeing did not think it could be certified under the common type rating that covers prior variants.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#232

Post by droithomme »

mikeash wrote: post #4
aivisol wrote: post #2

Is this only me, or all this one-vs-two AoA sensor talk seems some kind of diversion from the real problem with this plane. I mean, if one-sensor based MCAS failed twice so early in the life span of the plane model, what is the probability that a two-sensor model will fail pretty soon as well? The math should be simple, we have all data needed: combined hours flown by all planes of the type and number of failures (at…

The problem isn’t failure, but detecting failure. If the sensor had just stopped responding, there wouldn’t have been any problem. The planes would keep flying, the sensors would get replaced, and everyone would be fine. What happened was that the sensor gave erroneous readings. The MCAS system reacted to those erroneous reading and crashes the plane. With two sensors, you can detect failure. It’s very unlikely that…

> It’s very unlikely that both would fail simultaneously.

Ice, insects, birds, and volcanic ash are all things that tend to cause the pitot and the static tubes to become blocked. When you encounter ice, insects, birds, and volcanic ash, it is often the case that you get multiple simultaneous blockages. Blockages of the various tubes are not statistically independent events in practice.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#233

Post by phkahler »

volkl48 wrote: post #59
phkahler wrote: post #42

Earlier quoted context omitted.

But MCAS was added because the plane doesn't handle well in some situations.

Doesn't handle well is not equivalent to "is uncontrollable", though.

If I recall, it made it more prone to stall in certain conditions. I'd like to call that hazardous, but without test pilot feedback I'm not sure how to classify it. My recollection from articles a few months ago is that they added MCAS not due to simple differences in handling, but due to a potentially hazardous difference in handling.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#234

Post by dhimes »

jMyles wrote: post #220
dhimes wrote: post #216

Earlier quoted context omitted.

Is there a requirement to fly the plane advertised? In other words, if I book specifically a non-737 800 Max plane, and the airline switches, can I get my money back, or make them fly me on a different airline?

Interesting question. I have never had this happen, and I think I'll be asking a lot of questions if it does. It's not something an airline can do hastily, as different aircraft (well, at least those of differing type rating) require different crews to operate. So the airline will have to grab a totally different crew to match their replacement aircraft.

When it has happened to me, the crew came with the plane.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#235

Post by CydeWeys »

sorisos wrote: post #203
sirsuki wrote: post #190

Earlier quoted context omitted.

If the pilots were putting that much force on the yoke it is pretty apparent that the pilots really truly wanted the plan to do what they asked of it. I am curious what scenarios the designers of the plan drove then to not trust that the human in the seat really has no idea what they are doing. Was the ignoring the wishes of the pilot and attempt to prevent a crazed irresponsible and unlicensed idiot from doing somet…

Perhaps related crash[0] where the autopilot was disabled because it was listening to user input, in this case a child. [0] https://en.wikipedia.org/wiki/Aeroflot_Flight_593#Accident

Oooof. Well the real lesson there is that unqualified people (especially children) shouldn't be in the cockpit of an airliner at all. Autopilot can't be made smart enough to determine if the person operating the controls actually knows what they're doing, and thus to follow/ignore them as appropriate.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#236

Post by moritzplassnig »

jMyles wrote: post #220
dhimes wrote: post #216

Earlier quoted context omitted.

Is there a requirement to fly the plane advertised? In other words, if I book specifically a non-737 800 Max plane, and the airline switches, can I get my money back, or make them fly me on a different airline?

Interesting question. I have never had this happen, and I think I'll be asking a lot of questions if it does. It's not something an airline can do hastily, as different aircraft (well, at least those of differing type rating) require different crews to operate. So the airline will have to grab a totally different crew to match their replacement aircraft.

I assume it happens regularly. I had a couple of flights myself on other plans than initially advertised. I always assumed that the airline canceled/delayed other flights because of it (taking plane a and crew a from flight a to do flight b with plane a).

Before the 737 Max got grounded (after the 2nd crash), I remember reports that some airlines allowed passengers to rebook their flights for free (to end up on a different plane). I doubt they will continue doing it once the 737 Max is allowed to fly again. Eg, Southwest is too dependent on it.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#237

Post by CydeWeys »

dhimes wrote: post #216
Haga wrote: post #180

Earlier quoted context omitted.

It will fly only to be voted down with customers feet. I know a lot of people who looked on the plane type for the first time during their holiday bookings. This plane is finished.

Is there a requirement to fly the plane advertised? In other words, if I book specifically a non-737 800 Max plane, and the airline switches, can I get my money back, or make them fly me on a different airline?

Why did you put the 800 in there? The 737-800 is a separate plane from the 737-MAX, and doesn't suffer from these problems (and is still operating; I just flew one cross-country last week). You might be referring to the 737-MAX 8 (not 800), which is the only variant of the 737-MAX delivered so far.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#238

Post by sooheon »

suzzer99 wrote: post #193
kejaed wrote: post #43

Earlier quoted context omitted.

Thinking about this a little more, I also see a failure here in terms of naming things, which I have noticed in my career can be scoffed at but is so important. As the article says, the function of MCAS changed and its operational envelope was greatly expanded. What if, internally at least, the new system was referred to as MCAS2? This is somewhere that things can get political, as was exactly the case with the Max,…

This is so true. Naming to me is one of the most important decisions. When I see someone who frets over naming decisions for hours, or will sit down with me and really think through what we're going to name something - I know they get the gravity of the situation. I trust those kinds of people much more for big picture architectural or project lead decisions.

Do you have examples off the top of your head of really great names that have come as a result of this process?

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#239

Post by perl4ever »

frostburg wrote: post #183
deanCommie wrote: post #162

Earlier quoted context omitted.

I assume these must be small examples on a long list of accomplishments, because 30k/year doesn't seem like it's enough to offset your salary. I have to imagine the impact of a principal engineer should be measured in the 10-100x of their salary?

That's some pretty impressive ingrained bias towards rent-seekers. Why not 1.1x or the board can try doing the work?

Consider a fast food business. Should the manager be satisfied with making 10% profit on french fries?

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#240

Post by ackfoo »

There was indeed a deadly assumption in the design of the 737 Max: that pilots would be able to cope with a runaway trim problem by invoking a memory checklist.

Neither the Lion Air nor the Ethiopian pilots were able to do so, although the Lion Air crew that flew the same aircraft and encountered the same problem the day before managed to disable the electric trim and continue the flight to its destination without even inconveniencing the passengers.

This is not a design problem with the 737 Max. It is an indictment of the pilot training, economic, and social systems affecting the operation of some airlines.

The article fails to make it clear that the MCAS is, in fact, inactive for almost all of a normal flight: it is not operative when the autopilot is engaged, and it is not operative when the flaps are extended.

Furthermore, it is of no consequence whether the MCAS is specifically included in the flight manual because there is no possibility for the pilots to interact directly with the MCAS system; this can only happen through the runaway trim memory checklist.

The aircraft will be modified to use multiple sensors and to diminish the authority of MCAS. This will do nothing whatsoever to address the actual and growing problem that caused these incidents, which is the increasing tendency for pilots to be capable monitors of automated flight systems, but absolutely useless at flying the plane manually when those systems fail.

Thee will continue to be an increasing number of these type of incidents until we understand that not everything can be made cheaper and that objective facts exist and must guide our actions.

Our deflationary system enriches the few and keeps the rest happy by striving for ever-cheaper goods. We should be looking at pilots in the right seat of commercial aircraft with 98 hours of total flight time and saying, "no, that's beyond the limit of madness; we want quality of life instead of cheap goods and the pipe dream of wealth."

That won't matter to most of the ignorant reactionaries commenting in this thread who are looking to point the finger of blame anywhere but ourselves.

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