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You can fix the issues that have been found in the MCAS, sure. You can do more training, rewrite the code, introduce more tests/checks, etc... But what you can

You can fix the issues that have been found in the MCAS, sure. You can do more training, rewrite the code, introduce more tests/checks, etc... But what you cannot do is change the fact that the MCAS is necessary. The plane is always and forever going to be off-balanced and require an active system to account for that. Active systems will fail. Maybe they can fix it such that the failure rate is negligible, but I doubt it.

Alupis 7y ago
All Airbus airliners (the only other serious airline manufacturer in the world) are fully fly-by-wire and require computers and sensors to even get off the ground, let alone maintain level flight. Unstable flight profiles are not foreign in aircraft, and requiring computer systems to maintain stable flight is nothing new. The problem is entirely how this specific system was implemented... and that can be fixed.
- addicted44 7y ago
  The fact that Airbus are fly by wire doesn't mean they are "unstable". They might be, but fly by wire does not imply that. For the record, I don't believe Airbus plans are unstable in the way the MAX is, whose instability, from what I understand, came about because they were trying to fit larger engines on the original 737 frame (to prevent pilot retraining), and so had to move the wings higher.
  - johannes1234321 7y ago
    In some avionics podcast A380 pilots described that that huge beast is a quite good glider. This makes sense since you want to reduce fuel usage and just enjoy smooth sailing. Something like an F-16 however is less stable and requires constant adjustment of flaps etc. there dynamic properties of air to air dogfight are more important.
- henryfjordan 7y ago
  I'm not saying unstable planes cannot be built, just that I don't trust a company that's already had 2 planes go down to get it right. A quick google search seemed to imply most unstable airframes were military or experimental, not commercial. Unstable airframes are not appropriate for commercial airliners unless you can point to a good reason. "We don't want to train pilots" is a bad reason. The FAA should have pushed back very hard on this point. Personally I think the flaws in the 737-MAX design process were so deep that it would be safest to just scrap the plane. It's not that the issues cannot be fixed, but rather that we'd be better off starting over from scratch knowing that good design principles will be followed the whole time.
  - mlyle 7y ago
    It is not "unstable" in that sense. At high thrust, slow speed, high aoa it is a little too close to neutrally statically stable. C f. to airliners that can break up from dynamic yaw instability if the yaw dampers fail in some flight regimes.
    - henryfjordan 7y ago
      Thanks for explaining! I suppose I've been using "unstable" a bit too liberally in this thread.
- ClumsyPilot 7y ago
  Airbus planes don't fall out of the sky when air speed sensor fails.
  - benjohnson 7y ago
    Air France Flight 447 crashed with all souls on board lost when the air speed sensors on the Airbus A330 failed. https://en.wikipedia.org/wiki/Air_France_Flight_447 https://en.wikipedia.org/wiki/Air_France_Flight_447
    - ClumsyPilot 7y ago
      Have you read about accident you linked? "It highlighted the role of the co-pilot in stalling the aircraft while the flight computer was under alternate law at high altitude. This "simple but persistent" human error was given as the most direct cause of this accident"
DigitalSea 7y ago
I don't know why you are being downvoted, because you are right. While software and sensors to account for unstable airframes is not uncommon in aviation, before the 737 MAX, there has never been a civilian passenger plane with such a dynamically unstable frame requiring real-time correction via software and sensor data. In civilian aircraft, unstable frames like what we saw in the 737 MAX were not a thing. And honestly, I don't want them to become a thing either. I also acknowledge that the specific terms I use in this comment might not be 100% down to the letter terms used in the aviation industry (such as unstable frame). The point being made here is corners were cut, Boeing is 100% to blame for the situation they find themselves in with the 737 MAX. In avionics, fighter jets are unstable requiring computers and algorithms to keep them flying. This is in part to the speed of which they travel, the [Dassault Rafale](https://en.m.wikipedia.org/wiki/Dassault_Rafale https://en.m.wikipedia.org/wiki/Dassault_Rafale) has multiple levels of redundancy to correct negative flight conditions (it has three computers I believe). Even with the fixes, the plane is still going to be unstable. However, fortunately, unstable planes like passenger jets which move slower can still be manually flown (unlike fighter jets moving at Mach 1). But, I am definitely not going to fly on a 737 MAX if I can avoid it, not until it has proven itself in service for 10 years. I wouldn't say fixing an engineering problem with the software and additional sensors inspires confidence. Dynamically unstable airframes should not be a thing in passenger jets. The only reason the 737 MAX is unstable is that they put bigger engines on a 737 and moved them up because of how low the 737 sits on the ground, thus disrupting the centre of gravity and requiring pitch correction when at full thrust. The Airbus A320 has no such issues with its design. It can safely glide during total engine loss for quite a long distance. Could the 737 MAX claim the same thing? At full thrust the nose would point too far upward with the new design, potentially causing a stall. MCAS automatically pushed the nose down if the nose was detected to be pointing too far up. Pilots received a two-hour training course on an iPad before being allowed to fly on the 737 MAX, they didn't even highlight the new MCAS system. The training material didn't even mention the new MCAS software... The worrying thing about this entire situation is the MCAS system relied on a single AOA (Angle of Attack) sensor and overreacted and took control of the plane. Given planes are known for their levels of redundancy, a single sensor and some overzealous software coupled with other mistakes resulted in hundreds of lives lost. Pilots were not even notified in the cockpit that the MCAS software had taken over control of the plane. How insane is that? This all happened because Boeing pretended the 737 MAX was basically the same as the 737. The cause of the problems was not because of poor software, it was because Boeing tried to cut costs and put in a bandaid solution for the unstable frame they created. The software did its job, it's the lack of redundancy and ability to manually override the system that was the problem. They're just doubling down on it because there is no alternative to the engineering problem they created. MCAS = May Crash Any Second

Alupis 7y ago

All Airbus airliners (the only other serious airline manufacturer in the world) are fully fly-by-wire and require computers and sensors to even get off the ground, let alone maintain level flight. Unstable flight profiles are not foreign in aircraft, and requiring computer systems to maintain stable flight is nothing new. The problem is entirely how this specific system was implemented... and that can be fixed.

addicted44 7y ago
The fact that Airbus are fly by wire doesn't mean they are "unstable". They might be, but fly by wire does not imply that. For the record, I don't believe Airbus plans are unstable in the way the MAX is, whose instability, from what I understand, came about because they were trying to fit larger engines on the original 737 frame (to prevent pilot retraining), and so had to move the wings higher.
- johannes1234321 7y ago
  In some avionics podcast A380 pilots described that that huge beast is a quite good glider. This makes sense since you want to reduce fuel usage and just enjoy smooth sailing. Something like an F-16 however is less stable and requires constant adjustment of flaps etc. there dynamic properties of air to air dogfight are more important.
henryfjordan 7y ago
I'm not saying unstable planes cannot be built, just that I don't trust a company that's already had 2 planes go down to get it right. A quick google search seemed to imply most unstable airframes were military or experimental, not commercial. Unstable airframes are not appropriate for commercial airliners unless you can point to a good reason. "We don't want to train pilots" is a bad reason. The FAA should have pushed back very hard on this point. Personally I think the flaws in the 737-MAX design process were so deep that it would be safest to just scrap the plane. It's not that the issues cannot be fixed, but rather that we'd be better off starting over from scratch knowing that good design principles will be followed the whole time.
- mlyle 7y ago
  It is not "unstable" in that sense. At high thrust, slow speed, high aoa it is a little too close to neutrally statically stable. C f. to airliners that can break up from dynamic yaw instability if the yaw dampers fail in some flight regimes.
  - henryfjordan 7y ago
    Thanks for explaining! I suppose I've been using "unstable" a bit too liberally in this thread.
ClumsyPilot 7y ago
Airbus planes don't fall out of the sky when air speed sensor fails.
- benjohnson 7y ago
  Air France Flight 447 crashed with all souls on board lost when the air speed sensors on the Airbus A330 failed. https://en.wikipedia.org/wiki/Air_France_Flight_447 https://en.wikipedia.org/wiki/Air_France_Flight_447
  - ClumsyPilot 7y ago
    Have you read about accident you linked? "It highlighted the role of the co-pilot in stalling the aircraft while the flight computer was under alternate law at high altitude. This "simple but persistent" human error was given as the most direct cause of this accident"

DigitalSea 7y ago

I don't know why you are being downvoted, because you are right. While software and sensors to account for unstable airframes is not uncommon in aviation, before the 737 MAX, there has never been a civilian passenger plane with such a dynamically unstable frame requiring real-time correction via software and sensor data. In civilian aircraft, unstable frames like what we saw in the 737 MAX were not a thing. And honestly, I don't want them to become a thing either. I also acknowledge that the specific terms I use in this comment might not be 100% down to the letter terms used in the aviation industry (such as unstable frame). The point being made here is corners were cut, Boeing is 100% to blame for the situation they find themselves in with the 737 MAX. In avionics, fighter jets are unstable requiring computers and algorithms to keep them flying. This is in part to the speed of which they travel, the [Dassault Rafale](https://en.m.wikipedia.org/wiki/Dassault_Rafale https://en.m.wikipedia.org/wiki/Dassault_Rafale) has multiple levels of redundancy to correct negative flight conditions (it has three computers I believe). Even with the fixes, the plane is still going to be unstable. However, fortunately, unstable planes like passenger jets which move slower can still be manually flown (unlike fighter jets moving at Mach 1). But, I am definitely not going to fly on a 737 MAX if I can avoid it, not until it has proven itself in service for 10 years. I wouldn't say fixing an engineering problem with the software and additional sensors inspires confidence. Dynamically unstable airframes should not be a thing in passenger jets. The only reason the 737 MAX is unstable is that they put bigger engines on a 737 and moved them up because of how low the 737 sits on the ground, thus disrupting the centre of gravity and requiring pitch correction when at full thrust. The Airbus A320 has no such issues with its design. It can safely glide during total engine loss for quite a long distance. Could the 737 MAX claim the same thing? At full thrust the nose would point too far upward with the new design, potentially causing a stall. MCAS automatically pushed the nose down if the nose was detected to be pointing too far up. Pilots received a two-hour training course on an iPad before being allowed to fly on the 737 MAX, they didn't even highlight the new MCAS system. The training material didn't even mention the new MCAS software... The worrying thing about this entire situation is the MCAS system relied on a single AOA (Angle of Attack) sensor and overreacted and took control of the plane. Given planes are known for their levels of redundancy, a single sensor and some overzealous software coupled with other mistakes resulted in hundreds of lives lost. Pilots were not even notified in the cockpit that the MCAS software had taken over control of the plane. How insane is that? This all happened because Boeing pretended the 737 MAX was basically the same as the 737. The cause of the problems was not because of poor software, it was because Boeing tried to cut costs and put in a bandaid solution for the unstable frame they created. The software did its job, it's the lack of redundancy and ability to manually override the system that was the problem. They're just doubling down on it because there is no alternative to the engineering problem they created. MCAS = May Crash Any Second