Comment by kuzehanka | Hacker News Reader

Comment by kuzehanka | Hacker News Reader

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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.

That's not quite correct. When the aerodynamics of a plane was not designed to push forward the mounting of the engines, you have more reinforcement. That alone causes an uneven distribution for lift not accounted in the design itself. THIS is what causes the plane to nose up. But that doesn't mean stress is not put on the frame itself and mechanical parts that will be, on a daily basis, "abused" to the point of metal fatigue. You see, when it comes to aerodynamics, it's easy to test it on a simulator. And it seems boeing's 737 max passed with flying colors. Then, it had to fly. That's the moment when test pilots came to a conclusion that the design will not work. Boeing's solution was a software "fix" and it needed to relay on 1 sensor to pass certification.

So, what do you have? NO TRAINING on this airplane, a bugged software system, poor aerodynamics, poor design choice, stress on elevator, etc. The ethiopian airlines plane had such force that pilots were not able to manually turn the trim control wheel. Do you know how much force that plane had to have that the jack screw couldn't be operated manually? THAT is a severe design flaw. THAT is what is being investigated. Who is investigating Boeing? Boeing is investigating Boeing. Boeing on 5/7/19 admits it knew they had a severe problem but it can still be fixed. Who certified the fix? Boeing. But now the FAA is investigating that fix which was promised by April. Again, this is a severe design flaw with still many unknowns yet to be found.

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 ?

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?

Nobody who isn't an engineer wants is terribly interested in the argument that a model of plane that has killed 2 planes full of people recently is in anyone's opinion safe.

Personally I won't fly on one in my lifetime.

I'll leave the analysis of why to others to figure out why I fly on other airplanes.

Incidentally I have seen pilots argue that the max is inherently unsafe on this forum which is probably why people are reiterating it.

What is your area of expertise and what is your opinion?

You're missing the point of the post you're responding to. The poster is saying that the 737 MAX isn't inherently unsafe due to its aerodynamic configuration. The safety issue arose from the bungled MCAS system. This could be fixed without changing the airframe.

Actual engineers do care about the "why" since that's what matters. Otherwise don't bother flying on any aircraft since all models have crashed at some point.

Your second sentence is too glib. By just about any statistic you want to look at, the MAX-8 has an abysmal safety record. Probably worse than any other aircraft in revenue flight.

It's perfectly rational to look at the results, regardless of "why", and decide that the risk is just too great.

The 737-MAX with the larger engines turned the statically stable airframe into one that must use computers (eg MCAS) to make it dynamically stable which is a technique used on modern fighter jets but to my knowledge has never been applied to a passenger aircraft.

In this plane which is not "fly-by-wire" the pilots are part of the safety loop and are given a certain short amount of time to respond to an emergency.

Troubling to me is the footnote in the manual which there are times where the manual wheels for the trim require 80 lbs or 100 lbs or more of force. This amount of force would potentially preclude female pilots on these planes to handle these sorts of emergencies.

>The 737-MAX with the larger engines turned the statically stable airframe into one that must use computers (eg MCAS) to make it dynamically stable which is a technique used on modern fighter jets but to my knowledge has never been applied to a passenger aircraft.

This is completely false. The 737 MAX does not have relaxed static stability in the manner of a fighter jet. It just has different handling characteristics than earlier 737s at high angles of attack -- a region of the flight envelope that the pilot should never take the plane into in the first place.

Fighter jets of the kind you're referring to require continuous and precise adjustments of the flight control surfaces merely to avoid departing from controlled flight. This is absolutely not the case for the 737 MAX.

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