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My understanding is that the Boeing 737 max jet is unstable. Instead of redesigning a new plane from the ground up, Boeing placed the larger engines forward and

My understanding is that the Boeing 737 max jet is unstable. Instead of redesigning a new plane from the ground up, Boeing placed the larger engines forward and upward on the wings. Boeing then tried to issue a "software patch" on a bad hardware design. Boeing came up with an automated system to seize control of the aircraft in the event that the flight became unstable and neglected to inform pilots of this new automated system. Although not confirmed, it appears that both crashes may be the result of pilots wrestling with the plane's automated system, which they knew little about and may have been faulty

lisper 8y ago
Private pilot here. That is exactly right, based on everything that I've read and heard from other pilots, some of whom fly the Max 8.
- djsumdog 8y ago
  Other articles posted said there is a way to turn off the auto-correction, but it's not intuitive. On earlier 737s which had this, it came on when engaging automatic ascents/descents and was disabled when a pilot disabled those systems. In the case of the Max8, it's always on and there is additional training needed to react quickly when this happens. I think all current pilots who are watching this situation should know what to do at this point, but the needed the awareness brought by the situation. In the two crashes so far, it seems like the pilots had years of commercial experience.
  - lisper 8y ago
    Knowing what to do and actually doing it under stress are two very different things. The aircraft that I fly, a Cirrus SR22, also has an electric trim and so there is the potential for something to go wrong and the trim to go rogue. When that happens, dealing with it is a "simple" matter of pulling the right circuit breaker. But the circuit breakers are on a panel located near your right shin. They are not easy to see nor to reach, and if you don't have the location of the trim breaker memorized, the odds of being able to find it and pull it while the plane is trying to kill you are rather low. Happily, there has never been a runaway trim on an SR22 (AFAIK) so this doesn't keep me up at night. But I can certainly understand how even a pilot that was prepared for this eventuality might fail to deal with it properly while under duress.
planteen 8y ago
You are discounting the possibility of software controlling an aerodynamically unstable airplane safely. This has been happening for decades (see X-29, B-2, etc)
- jacquesm 8y ago
  Those airplanes were designed from the ground up with that control system in mind (the F16 is one of those). It's not something that you would normally retrofit on an otherwise unchanged design, the original 737 was never meant to be flown in that mode and a software patch to make it work that way sounds like a dangerous plan. On another note, I don't think the 737 Max is inherently unstable, so I'm not even sure this line of reasoning applies at all or even in part.
- localhost 8y ago
  Sure, but those pilots knew they were flying that kind of aerodynamically unstable airplane ahead of time. These pilots apparently were thinking "this is just a 737".
  - mcv 8y ago
    Exactly. The plane might well be perfectly safe in properly trained hands, but it seems rather obvious by now that it doesn't fly the same as a regular 737.
- deleted 8y ago
  [deleted]
- sangnoir 8y ago
  Did any of those aircraft quietly oppose the pilots authority?
  - mcv 8y ago
    I remember reading 30 years ago that the F-16 has 3 computers that vote on how to respond to user input.
ishan1121 8y ago
This is the conclusion I too could come up with. But whatever, I think these 2 737 crashes have pushed fully automatic flights a bit further.
shanth 8y ago
If this turns out to be a software bug of dangling pointer... oh imagine that poor developer has to take all the karma of lost lives...
- jostmey 8y ago
  Yes, it's possible that an engineer made a mistake--Boeing will certainly blame everyone else including the pilots and engineers. But the bigger picture here is that the plane might be unstable, it used a "software patch" as a band-aid, and it neglected to inform pilots about the new automated systems. I suspect the blame lies with Boeing's management and with the FAA for being complicit with Boeing.
tzs 8y ago
Unstability is not necessarily considered to be bad hardware design. Stability comes at a cost, such as less maneuverability or lower efficiency. Before fly by wire, it was always worth going for stability because pilots couldn't fly unstable aircraft. Fly by wire enabled making flyable unstable aircraft, and so trading off some inherent stability for more maneuverability (military) or higher efficiency (civilian) became an accepted design option.
cmurf 8y ago
That is not accurate. There is a sufficiently different pitching moment in high angle of attack attitude that results in the engine nacelle producing lift. That means the flight characteristic of the MAX is sufficiently different to otherwise warrant its own type rating separate from previous 737 generation type rating. Boeing and FAA agreed to a software abstraction to obviate the need for a separate type rating for pilots. The plane is not unstable. A pilot who is trained for the actual flight characteristics absolutely can handle the plane. The problem is they weren't required to get that training, because 737's still all share the same type rating as if they all have substantially the same flight characteristics. Which is generally true except one particular attitude, high angle of attack. It's an open question to me (I'm no one, but I am a pilot and a flight instructor in a previous life) exactly how different stall avoidance could be with MCAS disabled (which is indirectly done by setting stabilizer trim to cutoff) once it has already induced a dive by having fought with it a little bit too long. If it's a normal procedure to disable the very software abstraction that means you don't need a type rating for this airplane, but the stall avoidance technique is substantially different from other 737s - that's very concerning to me. Not that the plane is unstable or unsafe. But that there's a disconnect in pilot knowledge and actual airplane flight characteristics with this abstraction turned off.

lisper 8y ago

Private pilot here. That is exactly right, based on everything that I've read and heard from other pilots, some of whom fly the Max 8.

djsumdog 8y ago
Other articles posted said there is a way to turn off the auto-correction, but it's not intuitive. On earlier 737s which had this, it came on when engaging automatic ascents/descents and was disabled when a pilot disabled those systems. In the case of the Max8, it's always on and there is additional training needed to react quickly when this happens. I think all current pilots who are watching this situation should know what to do at this point, but the needed the awareness brought by the situation. In the two crashes so far, it seems like the pilots had years of commercial experience.
- lisper 8y ago
  Knowing what to do and actually doing it under stress are two very different things. The aircraft that I fly, a Cirrus SR22, also has an electric trim and so there is the potential for something to go wrong and the trim to go rogue. When that happens, dealing with it is a "simple" matter of pulling the right circuit breaker. But the circuit breakers are on a panel located near your right shin. They are not easy to see nor to reach, and if you don't have the location of the trim breaker memorized, the odds of being able to find it and pull it while the plane is trying to kill you are rather low. Happily, there has never been a runaway trim on an SR22 (AFAIK) so this doesn't keep me up at night. But I can certainly understand how even a pilot that was prepared for this eventuality might fail to deal with it properly while under duress.

planteen 8y ago

You are discounting the possibility of software controlling an aerodynamically unstable airplane safely. This has been happening for decades (see X-29, B-2, etc)

jacquesm 8y ago
Those airplanes were designed from the ground up with that control system in mind (the F16 is one of those). It's not something that you would normally retrofit on an otherwise unchanged design, the original 737 was never meant to be flown in that mode and a software patch to make it work that way sounds like a dangerous plan. On another note, I don't think the 737 Max is inherently unstable, so I'm not even sure this line of reasoning applies at all or even in part.
localhost 8y ago
Sure, but those pilots knew they were flying that kind of aerodynamically unstable airplane ahead of time. These pilots apparently were thinking "this is just a 737".
- mcv 8y ago
  Exactly. The plane might well be perfectly safe in properly trained hands, but it seems rather obvious by now that it doesn't fly the same as a regular 737.
deleted 8y ago
[deleted]
sangnoir 8y ago
Did any of those aircraft quietly oppose the pilots authority?
- mcv 8y ago
  I remember reading 30 years ago that the F-16 has 3 computers that vote on how to respond to user input.

ishan1121 8y ago

This is the conclusion I too could come up with. But whatever, I think these 2 737 crashes have pushed fully automatic flights a bit further.

shanth 8y ago

If this turns out to be a software bug of dangling pointer... oh imagine that poor developer has to take all the karma of lost lives...

jostmey 8y ago
Yes, it's possible that an engineer made a mistake--Boeing will certainly blame everyone else including the pilots and engineers. But the bigger picture here is that the plane might be unstable, it used a "software patch" as a band-aid, and it neglected to inform pilots about the new automated systems. I suspect the blame lies with Boeing's management and with the FAA for being complicit with Boeing.

tzs 8y ago

Unstability is not necessarily considered to be bad hardware design. Stability comes at a cost, such as less maneuverability or lower efficiency. Before fly by wire, it was always worth going for stability because pilots couldn't fly unstable aircraft. Fly by wire enabled making flyable unstable aircraft, and so trading off some inherent stability for more maneuverability (military) or higher efficiency (civilian) became an accepted design option.

cmurf 8y ago

That is not accurate. There is a sufficiently different pitching moment in high angle of attack attitude that results in the engine nacelle producing lift. That means the flight characteristic of the MAX is sufficiently different to otherwise warrant its own type rating separate from previous 737 generation type rating. Boeing and FAA agreed to a software abstraction to obviate the need for a separate type rating for pilots. The plane is not unstable. A pilot who is trained for the actual flight characteristics absolutely can handle the plane. The problem is they weren't required to get that training, because 737's still all share the same type rating as if they all have substantially the same flight characteristics. Which is generally true except one particular attitude, high angle of attack. It's an open question to me (I'm no one, but I am a pilot and a flight instructor in a previous life) exactly how different stall avoidance could be with MCAS disabled (which is indirectly done by setting stabilizer trim to cutoff) once it has already induced a dive by having fought with it a little bit too long. If it's a normal procedure to disable the very software abstraction that means you don't need a type rating for this airplane, but the stall avoidance technique is substantially different from other 737s - that's very concerning to me. Not that the plane is unstable or unsafe. But that there's a disconnect in pilot knowledge and actual airplane flight characteristics with this abstraction turned off.