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>>Software does not need to be this complicated. >>Design a damned airframe that's airworthy without needing stabilization hacks. In effect you are stating th

>>Software does not need to be this complicated. >>Design a damned airframe that's airworthy without needing stabilization hacks. In effect you are stating that you understand better than the hundreds of engineers involved with this project why these design trade-offs were made. Careful with that line of thinking. You're nearly guaranteed to be wrong. There are a host of reasons for the design in place: Efficiency, ease of implementation, familiarity with the components/technology, reliabilty of subsystems, availability of components, cost, maintenance complexity, etc. etc. etc. And, don't forget, efficiency standards. As the whole world freaks out about CO2 and global climate change/cooling/warming, and the insta-crowd 'air travel shames' those who use these magnificent machines, it's important to realize that some of these design decisions maximizing efficiency are the hereditary descendants of cultural pressures, too. Not to excuse any engineering f-ups, but there's a lot more to it than just 'build a simple tube with wings and an engine.'

Rooster61 7y ago
> ...why these design trade-offs were made. While your line of reasoning is sound in most scenarios, in this case, the why is pretty obviously written on the wall. The overriding reason why this hacky-hack software solution was slapped into the airframe was to keep from having to reclass the plane following the addition of too-large engines. Your reasons listed played into the design decisions that became MCAS, but the underlying reason as to why any of this nonsense was needed in the first place is because non-engineers forced a shitty situation on the people who actually implement these airframes. Hacker News is frequented by engineers from multiple disciplines, including software engineering, and many of those engineers know the kinds of terrible design decisions forced by management that come about to make a quick buck. People are pissed about it due to this fact, and rightly so.
- ethbro 7y ago
  I get the impression half of HN is pissed at Boeing because they understand terrible management-driven engineering decisions. The other half just think we're "pissed off at Boeing" and makes claims like "well, they should have just built the plane right." And so you get engineers taking umbrage (IMHO, rightly so) for the ridiculous simplification being made by the second half.
  - Rooster61 7y ago
    The lovely thing about HN is that that first half is probably indeed half of the people reading; whereas this same conversation on reddit might be 10% engineers, 90% echo chamber. That's at least my experience.
linuxftw 7y ago
> In effect you are stating that you understand better than the hundreds of engineers involved with this project why these design trade-offs were made. We don't know that any engineers approved this design. It could have been completely compartmentalized and approved by management only. We'll never know what the engineers said until there's a complete investigation and the engineers are subpoenaed. Here's what we know so far about the 'engineers': 1) The MCAS software was outsourced. 2) MCAS as originally designed and submitted to the FAA didn't have enough authority to affect the plane in the needed amount, so Boeing increased it's authority and never told the FAA. Point to speaks to a failure in basic engineering or a deliberate deception of the FAA. A competent engineering team should have been able to calculate exactly how much effect was needed before the plane left the ground. Sounds like they were winging it on this one.
- phicoh 7y ago
  I think the key thing is how the MCAS added new failure modes that the pilots where not briefed about. There should be way more strict user interface requirements. Including how humans are supposed to react to failures and whether that makes sense from human psychology point of view If the MCAS had informed pilots of a potential sensor failure, then there would have been a very good chance that the pilots would have been able to land the planes safely.
  - linuxftw 7y ago
    > If the MCAS had informed pilots of a potential sensor failure, then there would have been a very good chance that the pilots would have been able to land the planes safely. Perhaps on the two crashes. We don't have any data on successful landings with MCAS disabled in very adverse flying conditions. What if the plane is unsafe to fly without proper MCAS operation? There should be a test that results in a plane crash with 50% of the simulations with MCAS behaving properly (IE, extreme weather, low fuel, land or die). Now during that same simulation, disable MCAS randomly. Also, there seems to be potential for the MCAS to come in and out based on disagreement (loose sensor wiring, etc), and see what the crash rate is for intermittent MCAS failures. It's clear Boeing didn't do any of this kind of testing because they would have easily caught the failure modes that caused the plane to nose-dive into the ground. Completely predictable based on the behavior of the system.
vesinisa 7y ago
The reason for the MCAS hack was not any engineering wisdom but simply allowing them to build a completely different plane that they could claim was in fact the very same plane, and then sell it to airlines as such. While the aircraft manufacturing industry was decades ago heavily safety-focused, this oversight was possible because the FAA has resigned its regulatory powers to the industry's own "self-regulation". When the purported self-regulation of a stock market company stands between making large profits, guess which one budges?
- msbarnett 7y ago
  > The reason for the MCAS hack was not any engineering wisdom but simply allowing them to build a completely different plane that they could claim was in fact the very same plane, and then sell it to airlines as such The idea that MCAS is some kind of 737 emulator intended to keep the plane under the 737’s certification, and that without MCAS it would have needed more thorough training, is a persistent myth on HN. The reality is that MCAS exists because without it the 737 MAX’s aerodynamics are uncertifiable no matter how much training pilots were given. During testing the MAX was discovered to have an inverted force curve on the stick approaching a stall — as the aircraft approaches stall angle, forces flip around and it becomes easier to pull the stick back (into the stall) than push it forward (out of the stall angle). This violates a fundamental airworthiness requirement — commercial aircraft cannot be certified as airworthy if the stick forces invert. MCAS “solves” this by commanding the stabilizers down when it thinks the airplane approaches stall — effectively using the stabilizer to put the forces on the stick that are “missing” due to the MAX’s aerodynamics, ensuring the force curve never inverts. MCAS isn’t really allowing the plane to pretend to be anything other than “a plane that doesn’t want to stall mid-air”. Desire to keep the MAX requiring minimal training for 737 pilots (probably) drove the concealment of MCAS mentions from the manual, but MCAS would need to exist even if the airframe had been totally recertified from the ground up.
gdubs 7y ago
Isn’t that an appeal to authority fallacy though? With everything that’s come out about the Max, it’s clear that something is rotten in the process.

Rooster61 7y ago

> ...why these design trade-offs were made. While your line of reasoning is sound in most scenarios, in this case, the why is pretty obviously written on the wall. The overriding reason why this hacky-hack software solution was slapped into the airframe was to keep from having to reclass the plane following the addition of too-large engines. Your reasons listed played into the design decisions that became MCAS, but the underlying reason as to why any of this nonsense was needed in the first place is because non-engineers forced a shitty situation on the people who actually implement these airframes. Hacker News is frequented by engineers from multiple disciplines, including software engineering, and many of those engineers know the kinds of terrible design decisions forced by management that come about to make a quick buck. People are pissed about it due to this fact, and rightly so.

ethbro 7y ago
I get the impression half of HN is pissed at Boeing because they understand terrible management-driven engineering decisions. The other half just think we're "pissed off at Boeing" and makes claims like "well, they should have just built the plane right." And so you get engineers taking umbrage (IMHO, rightly so) for the ridiculous simplification being made by the second half.
- Rooster61 7y ago
  The lovely thing about HN is that that first half is probably indeed half of the people reading; whereas this same conversation on reddit might be 10% engineers, 90% echo chamber. That's at least my experience.

linuxftw 7y ago

> In effect you are stating that you understand better than the hundreds of engineers involved with this project why these design trade-offs were made. We don't know that any engineers approved this design. It could have been completely compartmentalized and approved by management only. We'll never know what the engineers said until there's a complete investigation and the engineers are subpoenaed. Here's what we know so far about the 'engineers': 1) The MCAS software was outsourced. 2) MCAS as originally designed and submitted to the FAA didn't have enough authority to affect the plane in the needed amount, so Boeing increased it's authority and never told the FAA. Point to speaks to a failure in basic engineering or a deliberate deception of the FAA. A competent engineering team should have been able to calculate exactly how much effect was needed before the plane left the ground. Sounds like they were winging it on this one.

phicoh 7y ago
I think the key thing is how the MCAS added new failure modes that the pilots where not briefed about. There should be way more strict user interface requirements. Including how humans are supposed to react to failures and whether that makes sense from human psychology point of view If the MCAS had informed pilots of a potential sensor failure, then there would have been a very good chance that the pilots would have been able to land the planes safely.
- linuxftw 7y ago
  > If the MCAS had informed pilots of a potential sensor failure, then there would have been a very good chance that the pilots would have been able to land the planes safely. Perhaps on the two crashes. We don't have any data on successful landings with MCAS disabled in very adverse flying conditions. What if the plane is unsafe to fly without proper MCAS operation? There should be a test that results in a plane crash with 50% of the simulations with MCAS behaving properly (IE, extreme weather, low fuel, land or die). Now during that same simulation, disable MCAS randomly. Also, there seems to be potential for the MCAS to come in and out based on disagreement (loose sensor wiring, etc), and see what the crash rate is for intermittent MCAS failures. It's clear Boeing didn't do any of this kind of testing because they would have easily caught the failure modes that caused the plane to nose-dive into the ground. Completely predictable based on the behavior of the system.

vesinisa 7y ago

The reason for the MCAS hack was not any engineering wisdom but simply allowing them to build a completely different plane that they could claim was in fact the very same plane, and then sell it to airlines as such. While the aircraft manufacturing industry was decades ago heavily safety-focused, this oversight was possible because the FAA has resigned its regulatory powers to the industry's own "self-regulation". When the purported self-regulation of a stock market company stands between making large profits, guess which one budges?

msbarnett 7y ago
> The reason for the MCAS hack was not any engineering wisdom but simply allowing them to build a completely different plane that they could claim was in fact the very same plane, and then sell it to airlines as such The idea that MCAS is some kind of 737 emulator intended to keep the plane under the 737’s certification, and that without MCAS it would have needed more thorough training, is a persistent myth on HN. The reality is that MCAS exists because without it the 737 MAX’s aerodynamics are uncertifiable no matter how much training pilots were given. During testing the MAX was discovered to have an inverted force curve on the stick approaching a stall — as the aircraft approaches stall angle, forces flip around and it becomes easier to pull the stick back (into the stall) than push it forward (out of the stall angle). This violates a fundamental airworthiness requirement — commercial aircraft cannot be certified as airworthy if the stick forces invert. MCAS “solves” this by commanding the stabilizers down when it thinks the airplane approaches stall — effectively using the stabilizer to put the forces on the stick that are “missing” due to the MAX’s aerodynamics, ensuring the force curve never inverts. MCAS isn’t really allowing the plane to pretend to be anything other than “a plane that doesn’t want to stall mid-air”. Desire to keep the MAX requiring minimal training for 737 pilots (probably) drove the concealment of MCAS mentions from the manual, but MCAS would need to exist even if the airframe had been totally recertified from the ground up.

gdubs 7y ago

Isn’t that an appeal to authority fallacy though? With everything that’s come out about the Max, it’s clear that something is rotten in the process.