7 ms·

> The engine mounting certainly does not make the plane unsafe. I don't think this is a very...'precise' statement. what is "safe" in the context of aviation?

> The engine mounting certainly does not make the plane unsafe. I don't think this is a very...'precise' statement. what is "safe" in the context of aviation? If you had no MCAS, then this plane has a very bad propensity to stall. I hope we can both agree that's an unsafe airplane. You can't just say "don't do that [pull up too much] and then you're fine". The aircraft "wants" to pitch up too high and stall, which predicated the MCAS system itself. So to me, yeah the engine mounting (in and of itself) makes this plane quite unsafe. Now, with a properly functioning MCAS it may be "safe", but when the MCAS is itself another point of failure, my opinion is that the aircraft is only safe on paper, while in practice it's just got too many hacks and kludges for it to be practically safe for the millions of safe flight hours that these things are expect to deliver.

kortilla 7y ago
No, it did not “have a bad propensity to stall”. That’s a very imprecise statement in the first place but if you take it to mean, it would try to stall during normal flight conditions, it’s definitely false. Airbus aircraft are “safe” despite the fact that dual conflicting pilot input is averaged without stick feedback (see the Airfrance flight from Brazil). If electronics being used to fly the aircraft upsets you, you’re going to be in for a real shocker on any airbus.
- marcosdumay 7y ago
  > That’s a very imprecise statement in the first place but if you take it to mean, it would try to stall during normal flight conditions, it’s definitely false. The precise wording would be that it is dynamically unstable, and the ball is with Boeing now to prove it's not the case. Also after all we discovered on the last weeks, Boeing better make a good case, or they won't convince anyone. The US aviation industry is about to change. I don't know into what, but it's not in a stable situation.
- JudgeWapner 7y ago
  if it didn't have a propensity to stall, why did they add the MCAS system?
- inferiorhuman 7y ago
  No, it did not “have a bad propensity to stall”. Okay, how's: you can use thrust to pitch up a 737 beyond the authority of the elevator. Airbus aircraft are “safe” despite the fact that dual conflicting pilot input is averaged without stick feedback (see the Airfrance flight from Brazil). There is an aural warning (DUAL INPUT) on Airbuses with conflicting input.
- kuzehanka 7y ago
  So much ignorance and misinformation about this issue even on HN. The parent comment and entire thread is 100% correct. There is nothing inherently unstable or unsafe about the MAX 8. It has a pitch-up characteristic that's mild compared to some other commercial jets like the 757. The only reason MCAS was put on that plane was to allow the MAX 8 to share a type rating with the rest of the 737 family, to make it so that it handles like any other 737 despite the pitch-up characteristic. Go ask any commercial pilot, go watch any of the commercial pilots on youtube who have commented on this, go look on stackexchange. The notion that the MAX 8 is inherently unstable, or unsound, or dangerous, is a laughable myth to anyone in the industry. I get that the news cycle is financially rewarded for fearmongering, but I really expected people who frequent HN to know better and do some cursory research into the topic rather than posting comments that perpetuate bullshit. There are several major issues with what boeing has done, such as the alleged failure to reclassify MCAS as a critical system after flight testing. But instead of discussing these legitimate issues, public debate seems to have been directed towards a bullshit myth about the airframe being inherently unstable. This has been eye-opening and dispelled my notion that HN had above-average quality of discussion on technical topics.
  - JudgeWapner 7y ago
    you're concerned about "comments that perpetuate bullshit". To me, the real bullshit is that a computer drove 2 aircraft into the earth. If we're so mistaken about what happened here, maybe the boeing engineers are similarly mistaken about how flight control systems work. I think they're the ones who have "ignorance and misinformation", like how many AoA sensors are required. Or whether a vigorous elevator UP position from the stick should be ignored and in fact counteracted by an opposite stabilizer position. Tell me what perpetuates the arrogance in the software departments at boeing that the computer knows better than the human. Unlike the pilots, the computer has nothing to lose. Yet the computer won the final decision. But calling this out is just the "news cycle financially rewarding" ... something ?
  - inferiorhuman 7y ago
    It has a pitch-up characteristic that's mild compared to some other commercial jets like the 757. Do you have any personal experience with or references for this claim?
manigandham 7y ago
The aircraft flies fine. MCAS is a stability control system that applies in certain cases (full power, high angle of attack) where the nose pitches up. It may lead to a stall but that's not what it's correcting for and it doesn't just happen during level flight. If the MCAS system was disabled then pilots handle it manually. Trim is not an exotic concept and just takes training and understanding of the operating characteristics. Airliners are very safe. They're not in dynamic stability like jet fighters and don't need active measures at all times to stay airborne. Having sensors and systems that coordinate to keep the aircraft flying optimally to remove pilot load and increase safety margins is a good thing and has been in use for decades. The problem here was a badly implemented system without redundancies and without enough training so that pilots were actually aware of the flight profile and MCAS. Also aircraft do not have millions of flight hours, they wouldn't reach a million even if they flew 24 hours a day for 100 years.
- bronson 7y ago
  The aircraft flies fine in most flight profiles, yes. At high angle of attack, the MAX-8 is more unstable than pilots were trained to expect. And the MCAS has done an absolutely miserable job of fixing this. Worst case scenario bad: it caused the loss of two airplanes that, if the MCAS had never been added to the MAX-8, would have reached their destinations just fine. Until the it flies predictably in every flight profile (including high AOA), it's demonstrably wrong to say "the aircraft flies fine." Maybe it will eventually "fly fine" but Boeing's got quite a bit of work to do first.
  - _ph_ 7y ago
    Alternatively just train the pilots on the behavior in the domain where MCAS would activate. MCAS main purpose is to lower the training requirements.
    - rocqua 7y ago
      Not quite if I am to believe other HN comments. The thing MCAS compensates for is that, in certain cases, as you pitch up more, the pressure on the stick decreases. This feels to pilots like leveling out, which is dangerous. MCAS was designed to counter this. The specific design of MCAS and not adding any new procedures, was to lower the training requirements. Specifically, anyone certified on the old 737 was still certified on the max. If they had improved the interface of MCAS and changed the procedure for runaway trim, it would have required more training. However, without MCAS or another remedy for the 'decreasing stick pressure at increasing pitch' problem, the plane would not have been allowed to fly at all.

kortilla 7y ago

No, it did not “have a bad propensity to stall”. That’s a very imprecise statement in the first place but if you take it to mean, it would try to stall during normal flight conditions, it’s definitely false. Airbus aircraft are “safe” despite the fact that dual conflicting pilot input is averaged without stick feedback (see the Airfrance flight from Brazil). If electronics being used to fly the aircraft upsets you, you’re going to be in for a real shocker on any airbus.

marcosdumay 7y ago
> That’s a very imprecise statement in the first place but if you take it to mean, it would try to stall during normal flight conditions, it’s definitely false. The precise wording would be that it is dynamically unstable, and the ball is with Boeing now to prove it's not the case. Also after all we discovered on the last weeks, Boeing better make a good case, or they won't convince anyone. The US aviation industry is about to change. I don't know into what, but it's not in a stable situation.
JudgeWapner 7y ago
if it didn't have a propensity to stall, why did they add the MCAS system?
inferiorhuman 7y ago
No, it did not “have a bad propensity to stall”. Okay, how's: you can use thrust to pitch up a 737 beyond the authority of the elevator. Airbus aircraft are “safe” despite the fact that dual conflicting pilot input is averaged without stick feedback (see the Airfrance flight from Brazil). There is an aural warning (DUAL INPUT) on Airbuses with conflicting input.
kuzehanka 7y ago
So much ignorance and misinformation about this issue even on HN. The parent comment and entire thread is 100% correct. There is nothing inherently unstable or unsafe about the MAX 8. It has a pitch-up characteristic that's mild compared to some other commercial jets like the 757. The only reason MCAS was put on that plane was to allow the MAX 8 to share a type rating with the rest of the 737 family, to make it so that it handles like any other 737 despite the pitch-up characteristic. Go ask any commercial pilot, go watch any of the commercial pilots on youtube who have commented on this, go look on stackexchange. The notion that the MAX 8 is inherently unstable, or unsound, or dangerous, is a laughable myth to anyone in the industry. I get that the news cycle is financially rewarded for fearmongering, but I really expected people who frequent HN to know better and do some cursory research into the topic rather than posting comments that perpetuate bullshit. There are several major issues with what boeing has done, such as the alleged failure to reclassify MCAS as a critical system after flight testing. But instead of discussing these legitimate issues, public debate seems to have been directed towards a bullshit myth about the airframe being inherently unstable. This has been eye-opening and dispelled my notion that HN had above-average quality of discussion on technical topics.
- JudgeWapner 7y ago
  you're concerned about "comments that perpetuate bullshit". To me, the real bullshit is that a computer drove 2 aircraft into the earth. If we're so mistaken about what happened here, maybe the boeing engineers are similarly mistaken about how flight control systems work. I think they're the ones who have "ignorance and misinformation", like how many AoA sensors are required. Or whether a vigorous elevator UP position from the stick should be ignored and in fact counteracted by an opposite stabilizer position. Tell me what perpetuates the arrogance in the software departments at boeing that the computer knows better than the human. Unlike the pilots, the computer has nothing to lose. Yet the computer won the final decision. But calling this out is just the "news cycle financially rewarding" ... something ?
- inferiorhuman 7y ago
  It has a pitch-up characteristic that's mild compared to some other commercial jets like the 757. Do you have any personal experience with or references for this claim?

manigandham 7y ago

The aircraft flies fine. MCAS is a stability control system that applies in certain cases (full power, high angle of attack) where the nose pitches up. It may lead to a stall but that's not what it's correcting for and it doesn't just happen during level flight. If the MCAS system was disabled then pilots handle it manually. Trim is not an exotic concept and just takes training and understanding of the operating characteristics. Airliners are very safe. They're not in dynamic stability like jet fighters and don't need active measures at all times to stay airborne. Having sensors and systems that coordinate to keep the aircraft flying optimally to remove pilot load and increase safety margins is a good thing and has been in use for decades. The problem here was a badly implemented system without redundancies and without enough training so that pilots were actually aware of the flight profile and MCAS. Also aircraft do not have millions of flight hours, they wouldn't reach a million even if they flew 24 hours a day for 100 years.

bronson 7y ago
The aircraft flies fine in most flight profiles, yes. At high angle of attack, the MAX-8 is more unstable than pilots were trained to expect. And the MCAS has done an absolutely miserable job of fixing this. Worst case scenario bad: it caused the loss of two airplanes that, if the MCAS had never been added to the MAX-8, would have reached their destinations just fine. Until the it flies predictably in every flight profile (including high AOA), it's demonstrably wrong to say "the aircraft flies fine." Maybe it will eventually "fly fine" but Boeing's got quite a bit of work to do first.
- _ph_ 7y ago
  Alternatively just train the pilots on the behavior in the domain where MCAS would activate. MCAS main purpose is to lower the training requirements.
  - rocqua 7y ago
    Not quite if I am to believe other HN comments. The thing MCAS compensates for is that, in certain cases, as you pitch up more, the pressure on the stick decreases. This feels to pilots like leveling out, which is dangerous. MCAS was designed to counter this. The specific design of MCAS and not adding any new procedures, was to lower the training requirements. Specifically, anyone certified on the old 737 was still certified on the max. If they had improved the interface of MCAS and changed the procedure for runaway trim, it would have required more training. However, without MCAS or another remedy for the 'decreasing stick pressure at increasing pitch' problem, the plane would not have been allowed to fly at all.