5 ms·

Maybe HN needs a way to flag comments as factually inaccurate. This meme about the airframe being 'fundamentally flawed' or 'engines are too big(????)' or inher

Maybe HN needs a way to flag comments as factually inaccurate. This meme about the airframe being 'fundamentally flawed' or 'engines are too big(????)' or inherently unstable has been disproved by everyone in the industry including people invested in Airbus. Please stop perpetuating evening time TV show fearmongering bullshit. The eli5 explanation of the MAX 8 MCAS incident is as follows: * Boeing wanted MAX 8 to have the 737 type rating. This means it must handle and fly just like other 737. This would allow existing 737 pilots to fly the MAX 8 with no additional training. This was part of Boeing's financial advantage. * To achieve the efficiency it has, the MAX 8 has pretty large engines. Because they wanted to keep the airframe like other 737, they couldn't lift the wings to accommodate. Instead they moved the engines closer to the body. * Moving the engines closer to the body increased the pitch-up characteristic at high AOA. Not so much as to make the plane unsafe (the 757 has a more aggressive pitch-up characteristic). But enough to make it sufficiently different from other 737 to invalidate the type rating. * Boeing adds MCAS to augment the pitch-up and make it handle like other 737. They get their type rating. * MCAS software validation happens with the assumptions that it's not a flight critical system, so constraints are relaxed. It passes. * Flight testing reveals that MCAS needs significantly more pitch authority to do its job. It's updated to get that pitch authority. MCAS now becomes a flight critical system after these changes, but is not re-evaluated as one. The airframe is fine. If Boeing gives up the 737 type rating and drops MCAS, they could have the fleet back in the air within a few weeks after pilots train for it. It just would cost their clients a lot more than originally promised and be a financial disaster. https://www.youtube.com/watch?v=CD0JabYjF3A&t= https://www.youtube.com/watch?v=CD0JabYjF3A&t= https://www.quora.com/Is-the-737-Max-supercritical-that-is-inherently-unstable-and-unflyable-without-constant-computer-intervention https://www.quora.com/Is-the-737-Max-supercritical-that-is-i...

Zigurd 7y ago
This is just a bit circular. The 737 MAX was designed so as to keep the type rating. The design would be different, and very likely fundamentally safer if keeping the 737 type rating were not a goal. A perverse incentive from the start. So I would not dismiss the claim that the 737 is "fundamentally flawed."
- kuzehanka 7y ago
  High AOA pitch-up is not a fundamental flaw and sure as shit isn't inherent instability of the airframe. There's a million things that went wrong with the MAX 8 debacle, serious things that need to be addressed after the industry takes a hard look at itself. But there being something wrong with the airframe isn't amongst them. That meme has no grounds, isn't supported by anyone at all in the industry, and originated from clickbait spamblogs and late night tv shows that feed off FUD. > The design would be different, and very likely fundamentally safer if keeping the 737 type rating were not a goal Errrr. The design is may not be maximally optimal (what does that even mean?) because of type rating pressure, therefore the design is fundamentally flawed? Please stop. You're perpetuating clickspam driven fake news and distracting from the real problems.
  - salawat 7y ago
    >There's a million things that went wrong with the MAX 8 debacle, serious things that need to be addressed after the industry takes a hard look at itself. But there being something wrong with the airframe isn't amongst them. That meme has no grounds, isn't supported by anyone at all in the industry, and originated from clickbait spamblogs and late night tv shows that feed off FUD. Really? Would you like to supply some names, or provide some whitepaper for that? https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the... Btw, the entire cause for MCAS being implemented is a desperate attempt to comply with FAR 25.173. If the non-certifiable behavior hadn't been there, there would not have been an issue. But wait, there's more! https://www.nytimes.com/2019/07/27/business/boeing-737-max-faa.html https://www.nytimes.com/2019/07/27/business/boeing-737-max-f... So we even have severe concerns over whether Boeing overstepped bounds in the safety process by approving their control line setup in spite of FAA concerns anyway. Some gems from that. >F.A.A. managers conceded that the Max “does not meet” agency guidelines “for protecting flight controls,” according to an agency document. But in another document, they added that they had to consider whether any requested changes would interfere with Boeing’s timeline. The managers wrote that it would be “impractical at this late point in the program,” for the company to resolve the issue. Mr. Duven at the F.A.A. also said the decision was based on the safety record of the plane. >Engineers at the agency were demoralized, the two agency employees said. One engineer submitted an anonymous complaint to an internal F.A.A. safety board, which was reviewed by The Times. >“During meetings regarding this issue the cost to Boeing to upgrade the design was discussed,” the engineer wrote. “The comment was made that there may be better places for Boeing to spend their safety dollars.” >An F.A.A. panel investigated the complaint. It found managers siding with Boeing had created “an environment of mistrust that hampers the ability of the agency to work effectively,” the panel said in a 2017 report, which was reviewed by The Times. The panel cautioned against allowing Boeing to handle this kind of approval, saying “the company has a vested interest in minimizing costs and schedule impact.” >By then, the panel’s findings were moot. Managers at the agency had already given Boeing the right to approve the cables, and they were installed on the Max. So, forgive me if I question the veracity of "most in the industry have figured it isn't a big deal", and even if they have, I question whether or not that decision comes from some level of just wanting to return to business as usual with minimum interruption or action/further regulation based on the coming to light of the scale of regulatory capture that has been uncovered by this debacle. The physics and presence of MCAS at all don't lie. The plane could not be certified without it. Personally, I deem an airframe to only encompass the physical structure without automation, and that assumption seems to be well received by those I know who have worked in aviation circles previously. Given that when I raise concerns with them, I universally get some variation of "what the hell were they thinking?," I'm not terribly willing to accept that a large portion of the active industry is necessarily making the most impartial judgement given that their livelihoods may very well be adversely effected by the fiscal failure of this plane. My sources include a former safety investigator/tech, and someone who worked with a maintenance squadron. So make of that what you will. Furthermore, I'm willing to tolerate some leniency with stretching regulations a bit, but not to the extent of normalizing deviance for the sake of expediency. Down that road lies too much catastrophe. Now I'll admit, I was one of the early central repeaters of the artificial feel system theory; I didn't have access to good technical docs, but apparently someone at the Seattle Times was able to find some corroboration, but I've done my damnedest to keep my reasoning constrained to my enthusiast level understanding of aerospace engineering and aviation, which has been rapidly expanding in my efforts to understand how something like this could happen in an industrial vertical famous for it's capacity to generate some of the safest machines on the planet. Just that reasoning alone is enough to at least get me questioning the sanity of the design decisions that have transpired w.r.t the MAX. This isn't FUD. People need to pay attention.
dTal 7y ago
In every rerun of this topic on HN, I've heard two countervailing viewpoints: 1) The 737 MAX is a perfectly viable airplane without the MCAS, whose sole purpose is to not invalidate the type rating; 2) The 737 MAX has dangerous, uncertifiable flight characteristics without the MCAS; namely, the stick force gradient inverts at high angles of attack. One comment[1] in this thread has even linked the relevant legislation[2]. So, which is it? [1] https://news.ycombinator.com/item?id=20607242 https://news.ycombinator.com/item?id=20607242 [2] https://www.law.cornell.edu/cfr/text/14/25.173 https://www.law.cornell.edu/cfr/text/14/25.173

Zigurd 7y ago

This is just a bit circular. The 737 MAX was designed so as to keep the type rating. The design would be different, and very likely fundamentally safer if keeping the 737 type rating were not a goal. A perverse incentive from the start. So I would not dismiss the claim that the 737 is "fundamentally flawed."

kuzehanka 7y ago
High AOA pitch-up is not a fundamental flaw and sure as shit isn't inherent instability of the airframe. There's a million things that went wrong with the MAX 8 debacle, serious things that need to be addressed after the industry takes a hard look at itself. But there being something wrong with the airframe isn't amongst them. That meme has no grounds, isn't supported by anyone at all in the industry, and originated from clickbait spamblogs and late night tv shows that feed off FUD. > The design would be different, and very likely fundamentally safer if keeping the 737 type rating were not a goal Errrr. The design is may not be maximally optimal (what does that even mean?) because of type rating pressure, therefore the design is fundamentally flawed? Please stop. You're perpetuating clickspam driven fake news and distracting from the real problems.
- salawat 7y ago
  >There's a million things that went wrong with the MAX 8 debacle, serious things that need to be addressed after the industry takes a hard look at itself. But there being something wrong with the airframe isn't amongst them. That meme has no grounds, isn't supported by anyone at all in the industry, and originated from clickbait spamblogs and late night tv shows that feed off FUD. Really? Would you like to supply some names, or provide some whitepaper for that? https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the... Btw, the entire cause for MCAS being implemented is a desperate attempt to comply with FAR 25.173. If the non-certifiable behavior hadn't been there, there would not have been an issue. But wait, there's more! https://www.nytimes.com/2019/07/27/business/boeing-737-max-faa.html https://www.nytimes.com/2019/07/27/business/boeing-737-max-f... So we even have severe concerns over whether Boeing overstepped bounds in the safety process by approving their control line setup in spite of FAA concerns anyway. Some gems from that. >F.A.A. managers conceded that the Max “does not meet” agency guidelines “for protecting flight controls,” according to an agency document. But in another document, they added that they had to consider whether any requested changes would interfere with Boeing’s timeline. The managers wrote that it would be “impractical at this late point in the program,” for the company to resolve the issue. Mr. Duven at the F.A.A. also said the decision was based on the safety record of the plane. >Engineers at the agency were demoralized, the two agency employees said. One engineer submitted an anonymous complaint to an internal F.A.A. safety board, which was reviewed by The Times. >“During meetings regarding this issue the cost to Boeing to upgrade the design was discussed,” the engineer wrote. “The comment was made that there may be better places for Boeing to spend their safety dollars.” >An F.A.A. panel investigated the complaint. It found managers siding with Boeing had created “an environment of mistrust that hampers the ability of the agency to work effectively,” the panel said in a 2017 report, which was reviewed by The Times. The panel cautioned against allowing Boeing to handle this kind of approval, saying “the company has a vested interest in minimizing costs and schedule impact.” >By then, the panel’s findings were moot. Managers at the agency had already given Boeing the right to approve the cables, and they were installed on the Max. So, forgive me if I question the veracity of "most in the industry have figured it isn't a big deal", and even if they have, I question whether or not that decision comes from some level of just wanting to return to business as usual with minimum interruption or action/further regulation based on the coming to light of the scale of regulatory capture that has been uncovered by this debacle. The physics and presence of MCAS at all don't lie. The plane could not be certified without it. Personally, I deem an airframe to only encompass the physical structure without automation, and that assumption seems to be well received by those I know who have worked in aviation circles previously. Given that when I raise concerns with them, I universally get some variation of "what the hell were they thinking?," I'm not terribly willing to accept that a large portion of the active industry is necessarily making the most impartial judgement given that their livelihoods may very well be adversely effected by the fiscal failure of this plane. My sources include a former safety investigator/tech, and someone who worked with a maintenance squadron. So make of that what you will. Furthermore, I'm willing to tolerate some leniency with stretching regulations a bit, but not to the extent of normalizing deviance for the sake of expediency. Down that road lies too much catastrophe. Now I'll admit, I was one of the early central repeaters of the artificial feel system theory; I didn't have access to good technical docs, but apparently someone at the Seattle Times was able to find some corroboration, but I've done my damnedest to keep my reasoning constrained to my enthusiast level understanding of aerospace engineering and aviation, which has been rapidly expanding in my efforts to understand how something like this could happen in an industrial vertical famous for it's capacity to generate some of the safest machines on the planet. Just that reasoning alone is enough to at least get me questioning the sanity of the design decisions that have transpired w.r.t the MAX. This isn't FUD. People need to pay attention.

dTal 7y ago

In every rerun of this topic on HN, I've heard two countervailing viewpoints: 1) The 737 MAX is a perfectly viable airplane without the MCAS, whose sole purpose is to not invalidate the type rating; 2) The 737 MAX has dangerous, uncertifiable flight characteristics without the MCAS; namely, the stick force gradient inverts at high angles of attack. One comment[1] in this thread has even linked the relevant legislation[2]. So, which is it? [1] https://news.ycombinator.com/item?id=20607242 https://news.ycombinator.com/item?id=20607242 [2] https://www.law.cornell.edu/cfr/text/14/25.173 https://www.law.cornell.edu/cfr/text/14/25.173