This is criminal behaviour, and people need to go to jail.
Yes.
The MAX should never be allowed to fly again.
No. Even at 20x the failure rate, flying in a Max -- even with an unmodified MCAS -- is still vastly safer than driving on a per-distance-travelled basis. Part of the problem is that commercial aviation has gotten so ridiculously safe that we've lost all perspective on risk assessment. The Max is actually fundamentally a safe plane. What made it unsafe was the totally fucked up attempt to make its flight characteristic the same as the old 737 so it and its pilots would not have to be re-certified. The right answer is to re-certify. That's expensive, but a lot cheaper than scrapping an entire fleet of brand new planes. Grounding the entire fleet forever is throwing out the baby with the bathwater.
Well, given that other models exist that accomplish the same job (albeit perhaps not from Boeing), it's going to be a steep climb to get European authorities to agree to certify it, I expect.
So, the correct comparison would not be to driving, but to flying in other planes with similar range that are already available. I am no expert, but I do not get the impression that it is looking good in this respect.
By "re-certify", do you just mean the pilots? Or do you include the plane itself?
The original problem was that the FAA requirement for how the stick force has to vary with angle of attack could not be met, because of the new engines having to be so far forward: instead of the stick force continuing to increase with higher AoA, it started to decrease at some point because of the pitch up moment due to the engines.
The simplest way to fix that would have been to increase the ground clearance so the engines could be moved back to where they were on previous 737s. That, of course, would have had to be done in the design stage, before planes started being built. I'm not sure if it would be possible to retrofit existing 737 MAX planes to do this.
If the physical airframe stays the same, then there has to be something in the flight controls that compensates for the pitch up moment of the engines at higher AoA in order to meet the stick force requirement. MCAS was an attempt to do that while keeping everything "close enough" to previous 737s. If that constraint is dropped, there might be a way to keep within the FAA stick force requirement without having the same failure modes as the MAX does, but that would still require a new type certification for the plane.
By "re-certify", do you just mean the pilots? Or do you include the plane itself?
Both.
the FAA requirement for how the stick force has to vary with angle of attack could not be met
No, that's a myth. There is no such requirement for aircraft in general. Many aircraft do not have this characteristic. But it happened to be true for the old 737, and so it had to be true for the Max in order for it to operate under the old 737's type certificate.
The Max could easily be certified as-is without MCAS as a new aircraft type (assuming no further nasty surprises turn up of course). That will be neither cheap nor easy. If it were, Boeing would have just done that in the first place. But it will be a hell of a lot cheaper than scrapping the fleet.
> that's a myth. There is no such requirement for aircraft in general.
14 CFR Part 25 Subpart B contains a number of requirements for stick force and gradient of stick force. In particular, section 25.255(b) says the stick force vs. g curve must have a positive slope and that the direction of the primary longitudinal control force must not reverse. IIRC that's the one that bit the MAX, but, as below, I'll have to go dig up references to see.
It's true that this is not the same as stick force vs. AoA, but under the conditions for which MCAS was intended, stick force vs. g works out to be basically the same thing.
It's been a while since I looked up references for all this, so I'll have to go back and see if I can dig up where I got the info that because of the pitch up moment of the engine the MAX could not meet one of the stick force gradient requirements without some kind of modification.
Well, I could be wrong. I remember reading in what I considered an authoritative source that MCAS was needed to preserve the type cert, not to comply with the FARs. But I can't find the reference right now.
If it's true that the Max can't be certified at all without MCAS that would be a whole nuther kettle of fish.
The specific issue seems to be the sentence: "No abnormal nose-up pitching may occur." The 737 MAX engines cause abnormal nose-up pitching at high enough AoA, if their pitch up moment is not compensated somehow.
Here is the page that first led me to that section:
I haven't read that there is an abnormal pitch up, which would directly contradict (a).
Nevertheless, I have a very serious problem about any kind of computer compensating for the lack of either static or dynamic stability as required in FAR 25. Those stability requirements are there to ensure an intrinsic aerodynamic behavior of the airplane. The instant your augmentation fails for any reason, including electrical failure, now your airplane is legally not airworthy and your pilots are legally not certified to fly it, because their training is predicated on that augmentation always being available.
That is why I think the central issue is not a violation of airworthiness standards regulations. If that were true, it seems like that would be known already, and there'd be hell to pay. Clear cut and dried.
Whereas it's a more complicated matter when it comes to type certifications. There are many nuances including the little detail that the FAA gets to decide the conditions under which a (new) aircraft type certificate is required (or not), and what kind of mitigations are required (or not). Only if the aircraft gets a new type certificate, is a pilot required to have a type rating and the commensurate training and currency requirements that go with it. I still think that's what all of this (being the problem with the airplane and the on-going delays) is about, and negotiating this with all the other civil air authorities.
I bet Brazil and EU regulators have resisted a sweep it under the carpet approach. And I also bet that somewhat recently the regulators, even at FAA, got to a point where they decided they needed to see the NTSB report. Otherwise, they could plausibly roll out a "fix" that doesn't adequately fix the problem per NTSB. And if that happened, while I could see FAA paper over it these days, I'd expect other civil aircraft authorities say no. And plausibly reground the airplane until it does get a proper fix.
> That is why I think the central issue is not a violation of airworthiness standards regulations. If that were true, it seems like that would be known already, and there'd be hell to pay. Clear cut and dried.
The airworthiness regulations are tested in flight, so if Boeing flight tested a 737 MAX with MCAS active and it passed, there would be no violation. The regulations do not say the airplane has to pass the flight test with no automated compensation systems active.
> it's a more complicated matter when it comes to type certifications
Yes, the judgment of when a new variant is different enough that it requires a new type certification is not cut and dried. That might come into play if the FAA's judgment of whether the 737 MAX with MCAS should have required a new type certification were the question; but it isn't. The question is what it would take to make the 737 MAX without MCAS qualify to fly. At this point I don't think anyone believes that will happen without a new type certification for the 737 MAX; the question is whether even with a new type certification it will be possible to convince the FAA that the plane qualifies to fly.
I don't know if the per-distance-traveled basis is really that meaningful. If air travel didn't exist, people would simply not undertake these trips under the same "cheap" circumstances they do now, and our attitude toward long distance travel would be very different as a result. It's not like, if I want to go to Europe for a week, I'm choosing between flying and driving. I'm flying or I'm not going at all.
Comments
Yes.
No. Even at 20x the failure rate, flying in a Max -- even with an unmodified MCAS -- is still vastly safer than driving on a per-distance-travelled basis. Part of the problem is that commercial aviation has gotten so ridiculously safe that we've lost all perspective on risk assessment. The Max is actually fundamentally a safe plane. What made it unsafe was the totally fucked up attempt to make its flight characteristic the same as the old 737 so it and its pilots would not have to be re-certified. The right answer is to re-certify. That's expensive, but a lot cheaper than scrapping an entire fleet of brand new planes. Grounding the entire fleet forever is throwing out the baby with the bathwater.
I did the math one time with very conservative numbers (thinking it'd be an easy win) and got shockingly close:
https://news.ycombinator.com/item?id=19983686
If you have an alternative reference or more exact numbers I'd love to see them!
Well, given that other models exist that accomplish the same job (albeit perhaps not from Boeing), it's going to be a steep climb to get European authorities to agree to certify it, I expect.
So, the correct comparison would not be to driving, but to flying in other planes with similar range that are already available. I am no expert, but I do not get the impression that it is looking good in this respect.
No doubt.
Yes, but the correct comparison is the recertified Max, without MCAS, and with re-trained pilots. That is the alternative to scrapping the fleet.
> The right answer is to re-certify.
By "re-certify", do you just mean the pilots? Or do you include the plane itself?
The original problem was that the FAA requirement for how the stick force has to vary with angle of attack could not be met, because of the new engines having to be so far forward: instead of the stick force continuing to increase with higher AoA, it started to decrease at some point because of the pitch up moment due to the engines.
The simplest way to fix that would have been to increase the ground clearance so the engines could be moved back to where they were on previous 737s. That, of course, would have had to be done in the design stage, before planes started being built. I'm not sure if it would be possible to retrofit existing 737 MAX planes to do this.
If the physical airframe stays the same, then there has to be something in the flight controls that compensates for the pitch up moment of the engines at higher AoA in order to meet the stick force requirement. MCAS was an attempt to do that while keeping everything "close enough" to previous 737s. If that constraint is dropped, there might be a way to keep within the FAA stick force requirement without having the same failure modes as the MAX does, but that would still require a new type certification for the plane.
Both.
No, that's a myth. There is no such requirement for aircraft in general. Many aircraft do not have this characteristic. But it happened to be true for the old 737, and so it had to be true for the Max in order for it to operate under the old 737's type certificate.
The Max could easily be certified as-is without MCAS as a new aircraft type (assuming no further nasty surprises turn up of course). That will be neither cheap nor easy. If it were, Boeing would have just done that in the first place. But it will be a hell of a lot cheaper than scrapping the fleet.
> that's a myth. There is no such requirement for aircraft in general.
14 CFR Part 25 Subpart B contains a number of requirements for stick force and gradient of stick force. In particular, section 25.255(b) says the stick force vs. g curve must have a positive slope and that the direction of the primary longitudinal control force must not reverse. IIRC that's the one that bit the MAX, but, as below, I'll have to go dig up references to see.
It's true that this is not the same as stick force vs. AoA, but under the conditions for which MCAS was intended, stick force vs. g works out to be basically the same thing.
It's been a while since I looked up references for all this, so I'll have to go back and see if I can dig up where I got the info that because of the pitch up moment of the engine the MAX could not meet one of the stick force gradient requirements without some kind of modification.
Well, I could be wrong. I remember reading in what I considered an authoritative source that MCAS was needed to preserve the type cert, not to comply with the FARs. But I can't find the reference right now.
If it's true that the Max can't be certified at all without MCAS that would be a whole nuther kettle of fish.
I had misremembered the specific CFR section: it was 14 CFR 25.203:
https://www.law.cornell.edu/cfr/text/14/25.203
The specific issue seems to be the sentence: "No abnormal nose-up pitching may occur." The 737 MAX engines cause abnormal nose-up pitching at high enough AoA, if their pitch up moment is not compensated somehow.
Here is the page that first led me to that section:
http://www.b737.org.uk/mcas.htm
Still digging for more info.
Possibly 25.173, in particular (c).
I haven't read that there is an abnormal pitch up, which would directly contradict (a).
Nevertheless, I have a very serious problem about any kind of computer compensating for the lack of either static or dynamic stability as required in FAR 25. Those stability requirements are there to ensure an intrinsic aerodynamic behavior of the airplane. The instant your augmentation fails for any reason, including electrical failure, now your airplane is legally not airworthy and your pilots are legally not certified to fly it, because their training is predicated on that augmentation always being available.
That is why I think the central issue is not a violation of airworthiness standards regulations. If that were true, it seems like that would be known already, and there'd be hell to pay. Clear cut and dried.
Whereas it's a more complicated matter when it comes to type certifications. There are many nuances including the little detail that the FAA gets to decide the conditions under which a (new) aircraft type certificate is required (or not), and what kind of mitigations are required (or not). Only if the aircraft gets a new type certificate, is a pilot required to have a type rating and the commensurate training and currency requirements that go with it. I still think that's what all of this (being the problem with the airplane and the on-going delays) is about, and negotiating this with all the other civil air authorities.
I bet Brazil and EU regulators have resisted a sweep it under the carpet approach. And I also bet that somewhat recently the regulators, even at FAA, got to a point where they decided they needed to see the NTSB report. Otherwise, they could plausibly roll out a "fix" that doesn't adequately fix the problem per NTSB. And if that happened, while I could see FAA paper over it these days, I'd expect other civil aircraft authorities say no. And plausibly reground the airplane until it does get a proper fix.
Including possibly a new type certification.
> That is why I think the central issue is not a violation of airworthiness standards regulations. If that were true, it seems like that would be known already, and there'd be hell to pay. Clear cut and dried.
The airworthiness regulations are tested in flight, so if Boeing flight tested a 737 MAX with MCAS active and it passed, there would be no violation. The regulations do not say the airplane has to pass the flight test with no automated compensation systems active.
> it's a more complicated matter when it comes to type certifications
Yes, the judgment of when a new variant is different enough that it requires a new type certification is not cut and dried. That might come into play if the FAA's judgment of whether the 737 MAX with MCAS should have required a new type certification were the question; but it isn't. The question is what it would take to make the 737 MAX without MCAS qualify to fly. At this point I don't think anyone believes that will happen without a new type certification for the 737 MAX; the question is whether even with a new type certification it will be possible to convince the FAA that the plane qualifies to fly.
I don't know if the per-distance-traveled basis is really that meaningful. If air travel didn't exist, people would simply not undertake these trips under the same "cheap" circumstances they do now, and our attitude toward long distance travel would be very different as a result. It's not like, if I want to go to Europe for a week, I'm choosing between flying and driving. I'm flying or I'm not going at all.
Perhaps sailing is starting to look interesting again? (yes, yes, that's a 10+ year in the future, I guess)
I don't think people are making the comparison of Max vs driving. They are making the comparison of Max vs other air planes.