201–210 of 260 posts
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> has big design flaws and a relatively bad safety record understatement...
Yeah 2 out of 387 hull losses over 2 years is a pretty awful record. I will stick to not 737 MAX thanks.
With the airline industry going through an unprecedented recession I don't think we will see a lot of new 737s being delivered thankfully.
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They have two AOA sensors. In a particular stroke of genius, the MCAS system would select one randomly at boot and use it exclusively (so you have twice the failure rate of a single sensor and no benefits from an extra one). And the AOA disagree system the FAA "proposes" installing? That was already an optional extra.
Maybe I need to brush up on my probabilities, but why would you have twice the failure rate? If each sensor failed 5% of the time and the sensor was chosen at random, wouldn’t the failure rate be the same?
There was no automated cross-check out of the box.
Part of the reason for that setup was that Boeing knew if they implemented a multi-sensor solution, it'd require class D simulator training, which they were trying to avoid at all costs. See the 60 Minutes 737 MAX exposé. They apparently had a whistleblower willing to attest to it.
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The LA pilots worked the problem for 5 minutes, the EA 2 minutes. Quite a bit more than seconds. Frankly, I'm baffled by the EA pilots. If I was a MAX pilot, and I received an EMERGENCY AIRWORTHINESS DIRECTIVE about how to not crash like LA pilots, it's my job to read, understand, and remember those instructions. And not just my job, it'd save my own life, too. It's not like it's complicated, either. Two simple steps…
A crash is not due to one cause. Multiple things have to fail for this to be a problem. Blaming pilots is way too simplistic. The design of those warnings were highly confusing and overwhelming. Saying "oh, just have better pilots" it NOT good enough. It should be as per the Swiss cheese theory where multiple things should fail before there's a problem. Further, not hide things like MCAS, downplay the need for additi…
You're entirely correct.
> Blaming pilots is way too simplistic.
Also correct, but in my opinion the pilots were one of the multiple causes of the accidents, based on the published accounts of their actions. Ignoring Emergency Airworthiness Directives is inexcusable. Ignoring EADs is a problem that should be dealt with as part of the corrective actions required by the FAA.
Recall that immediately prior to the LA crash, the previous flight crew on the same airplane had the same problem, dealt with it, and landed safely. (That was also before the EAD was issued.)
Let me put it another way - would you want to get on an airplane with a crew that didn't pay attention to Emergency Airworthiness Directives? I wouldn't.
And yes, Boeing must fix the MCAS system. I'm not excusing Boeing's role in the accidents.
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This is not a good argument. You can control this level of risk. Taking on any unnecessary risk when you don't have to is not a wise choice.
Yours is not a good argument. You can't assess this type of risk, let alone control it. Even if you are an aeronautical engineer, you won't convince me that you can assess these risks, because teams of aeronautical engineers designed this plane and did it overall very safely like they did the planes that came before it, and I'd have no reason to believe your claims. None of them assessed this level of risk as risky,…
Then there’s the hackiness of MCAS itself. Boeing tried to cut corners and put bigger engines on an ancient plane design that couldn’t accommodate them without deleterious aerodynamic effects.
Then, to help airlines cut corners, they slapped MCAS on it to suppress those effects and obviate the need for pilot training.
Of course, the big “problem” should be easily manageable by any pilot: an upward-pitching tendency under heavy power. If you don’t notice or can’t easily correct for that, you have no business flying a plane.
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> why is the MCAS still needed? Because Boeing and the FAA are talking out of both sides of their mouth. The planes aren't safe to fly without MCAS, MCAS is unreliable, so the solution is to disable MCAS whenever the plane determines it's best, even if it's going to be highly detrimental to safely operating. We still don't have ANY data on flying the planes safely without MCAS. We only have data on planes where MCAS…
MCAS is only supposed to activate in extreme circumstances. The planes are perfectly safe to fly and capable of flying without MCAS working. I think you need to read up on MCAS a bit more.
The regulation is clear cut, and unambiguous in that regard. Furthermore, the crashes that occurred happened because a system that is only supposed to kick in at the extremes did so in non-extreme situations repeatedly due to GIGO (Garbage In, Garbage Out), and to disastrous effect.
I welcome you to look at the FDR telemetry curves for the two flights. The AoA measurement for one of them was 70-80 degrees if I recall, the other was 20ish degrees offset from where it should have been.
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> However the method, it's far more likely to injure you than flying on a 737 MAX. That depends. If you take a bus to go to the airport and it takes you an hour to get there, then your flight also lasts an hour (for simplicity's sake), you are almost 3 times more likely(on average) to die during the flight than you are during the bus ride [0]. In terms of number of journeys by plane and bus, for the same number of jo…
Deaths per billion: |Journeys | Hours | KM Bus| 4.3 | 11.1 | 0.4 Air| 117 | 30.8 | 0.05 That's really interesting. Per KM, air is way safer than bus, but per journey it's roughly the same degree in the other direction. I'm having a hard time saying which one is safer from that data. However, both are very, very safe. I would like to see "Air" replaced by "737 Max" though.
Don't tell me that when people tout the safety of air transport they're using deaths per billions of km rather than per (billions of) journeys. Journeys is the important metric, surely!
https://www.faa.gov/news/media/attachments/19_035n-R3-8-3-20... > "To address the unsafe condition, the FAA proposes to require four design changes: (1) installing updated flight control software (with new control laws) for the FCC operational program software (OPS), (2) installing updated MDS display processing computer (DPC) software to generate an AOA disagree alert, (3) revising certain AFM flightcrew operating p…
> seems to amount to about 20 lines of code it's sobering to think that 20 lines of code could potentially have saved 346 lives :/
[0] https://www.nytimes.com/2019/05/05/business/boeing-737-max-w...
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There are force feedback joysticks, though I don't know whether something like MS Flight Simulator supports that.
It'd take a pretty fancy home force feedback system to be able to simulate forces in the multiple-pound range, which I think is what it'd take to give an accurate simulation.
I did some napkin math at one point, and the motor on those screwjacks to actuate against the Ethiopian Airlines loads was in the avenue of a 300 ft-lbs if I remember correctly.. (I only remember it was a number similar to what a car engine would be expected to put out).
I didn't know the exact gearing arrangement for the trim wheel, but the simulator footage was enough to convince me it certainly wasn't guaranteed to be practical.
Hum, it doesn't seem like a lot. Maybe I missing something, but looks like a software update to make MCAS more robust. And if it bug, raise an alarm and flight-crew operating procedures should be (?) to deactivate MCAS and fly without ? Could pilots actually fly the plane without MCAS ? It must feels like an entirely different aircraft.
Yes, to my understanding the only issue a pilot would run into with MCAS disabled and neutral is decreasing control forces at high angles of attack. The FAA requires control forces to monotonically increase with angle. I say "only" but that probably makes for a very weird feeling airplane to fly; how dangerous that actually is for a trained pilot I can't answer for sure but my gut and experience tells me not very.
I'd be comfortable with taking it as a given this is not an avenue worth excavating.
Earlier quoted context omitted.
They have two AOA sensors. In a particular stroke of genius, the MCAS system would select one randomly at boot and use it exclusively (so you have twice the failure rate of a single sensor and no benefits from an extra one). And the AOA disagree system the FAA "proposes" installing? That was already an optional extra.
Maybe I need to brush up on my probabilities, but why would you have twice the failure rate? If each sensor failed 5% of the time and the sensor was chosen at random, wouldn’t the failure rate be the same?
Now imagine it's not a coin but a normal distribution. If you sample from it twice then take the minimum of your samples, the chance that the minimum is below the mean is 75%. Just the same as with the coin but in another context.
Obviously the time-before-failure is not normally distributed, nor are the sensors completely independent random variables. But the chance of failure of the system will be higher than one sensor, not double exactly but higher.