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The big issue here is how much of the existence of this system, the desire to NOT make OTHER changes to the plane that would inhibit the pitch-up tendencies, an

The big issue here is how much of the existence of this system, the desire to NOT make OTHER changes to the plane that would inhibit the pitch-up tendencies, and the lack of necessity for another type rating were all driven by simply an attempt to skirt existing regulations and save Boeing and Southwest a ton of money. The reality is that this was the whole deal with the Max. All of these decisions were made in a context were avoiding the requirement for a new certification or type rating for pilots was a must. We can't avoid the reality that had the necessity to skirt regs not been there, Boeing would have definitely come up with a different solution from an engineering perspective.

rpiguy 8y ago
To add to your hypothesis - making a change to the fly-by-wire system was probably much cheaper than making airframe changes to make the aircraft more neutral in flight (airframe changes which would likely also negatively affect fuel economy). So Boeing took the cheap rout and decided to have the computer handle the pitch-up tendencies of the aircraft... This kind of fix is quite common on fighter aircraft which are purposely designed to not be neutral/stable in flight for better handling characteristics (among many other reasons). I have no idea how common this kind of fix is on a passenger aircraft.
- PaulHoule 8y ago
  It is a violation of the brand expectations pilots have for Boeing. Boeing introduced fly by wire after Airbus and it did it in such a way to preserve the feel of flying a plane, in particular if you have a fight with the system you could pull harder and win. Some pilots have strong feelings about this and are loathe to switch from Boeing to Airbus or vice versa.
  - ChicagoBoy11 8y ago
    As a pilot (sadly not a Boeing, or anything close to that side), I think this is a non-trivial point. Every second professional airline pilot you will talk to will talk about that philosophy difference between Airbus and Boeing, and 99.999% of them will take Boeing's side. Sadly, pilots really don't have much of a say in those discussions. They'll fly what's put in front of them, but I can assure you that all feel safer being given a plane not trying to actively fight them.
- coryfklein 8y ago
  Are you saying now we have pilots trained for commercial that are flying planes designed more like fighter jets? Eeek.
justin66 8y ago
> We can't avoid the reality that had the necessity to skirt regs not been there, Boeing would have definitely come up with a different solution from an engineering perspective. "Necessity?"
- ChicagoBoy11 8y ago
  Bad choice of words. I meant to imply that someone in upper management made this a requirement, and then it was up to the engineers to figure out how to accomplish that, contrasting it to a view that this was a pure engineering failure. If this were completely an engineering consideration, I'm sure they would have come up with a different solution. The (artificial) political constraint is what led to this particular design.
mikeash 8y ago
This also suggests a failure by the FAA. Not to deflect any blame from Boeing, but regulators have to assume that companies will bend the rules as much as they can, if it’s to their benefit. Perhaps the rules on what requires a new type rating are too lenient.
mannykannot 8y ago
One of the articles this one links to [1] makes what might be a significant point, at least with regard to the Lion Air crash: "[The MCAS-commanded trim change] can be stopped by the pilot counter-trimming on the yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the pilot pulling the yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the pilot pulling so hard on the yoke that the aircraft is flying close to stall. "It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the pilots pulling against it. The faulty high AOA signal was still present. "How should they know that pulling on the yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the pilot’s manual, the FCOM." From other sources, it seems that Boeing's decision not to reveal this feature was justified, in part, on the grounds that the documented procedure for dealing with a trim runaway was the same as for preceding versions of the aircraft. This does not seem to have taken into account that the pilots' experience would differ from what they had been led, through their training, to expect, and likely to cause confusion over what was going on. Of course, now that this has come to light, one would hope that every 737-MAX pilot would have by now been well-prepared to handle the situation - unless there is some additional issue which has not been identified yet. [1] https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ https://leehamnews.com/2018/11/14/boeings-automatic-trim-for...

rpiguy 8y ago

To add to your hypothesis - making a change to the fly-by-wire system was probably much cheaper than making airframe changes to make the aircraft more neutral in flight (airframe changes which would likely also negatively affect fuel economy). So Boeing took the cheap rout and decided to have the computer handle the pitch-up tendencies of the aircraft... This kind of fix is quite common on fighter aircraft which are purposely designed to not be neutral/stable in flight for better handling characteristics (among many other reasons). I have no idea how common this kind of fix is on a passenger aircraft.

PaulHoule 8y ago
It is a violation of the brand expectations pilots have for Boeing. Boeing introduced fly by wire after Airbus and it did it in such a way to preserve the feel of flying a plane, in particular if you have a fight with the system you could pull harder and win. Some pilots have strong feelings about this and are loathe to switch from Boeing to Airbus or vice versa.
- ChicagoBoy11 8y ago
  As a pilot (sadly not a Boeing, or anything close to that side), I think this is a non-trivial point. Every second professional airline pilot you will talk to will talk about that philosophy difference between Airbus and Boeing, and 99.999% of them will take Boeing's side. Sadly, pilots really don't have much of a say in those discussions. They'll fly what's put in front of them, but I can assure you that all feel safer being given a plane not trying to actively fight them.
coryfklein 8y ago
Are you saying now we have pilots trained for commercial that are flying planes designed more like fighter jets? Eeek.

justin66 8y ago

> We can't avoid the reality that had the necessity to skirt regs not been there, Boeing would have definitely come up with a different solution from an engineering perspective. "Necessity?"

ChicagoBoy11 8y ago
Bad choice of words. I meant to imply that someone in upper management made this a requirement, and then it was up to the engineers to figure out how to accomplish that, contrasting it to a view that this was a pure engineering failure. If this were completely an engineering consideration, I'm sure they would have come up with a different solution. The (artificial) political constraint is what led to this particular design.

mikeash 8y ago

This also suggests a failure by the FAA. Not to deflect any blame from Boeing, but regulators have to assume that companies will bend the rules as much as they can, if it’s to their benefit. Perhaps the rules on what requires a new type rating are too lenient.

mannykannot 8y ago

One of the articles this one links to [1] makes what might be a significant point, at least with regard to the Lion Air crash: "[The MCAS-commanded trim change] can be stopped by the pilot counter-trimming on the yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the pilot pulling the yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the pilot pulling so hard on the yoke that the aircraft is flying close to stall. "It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the pilots pulling against it. The faulty high AOA signal was still present. "How should they know that pulling on the yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the pilot’s manual, the FCOM." From other sources, it seems that Boeing's decision not to reveal this feature was justified, in part, on the grounds that the documented procedure for dealing with a trim runaway was the same as for preceding versions of the aircraft. This does not seem to have taken into account that the pilots' experience would differ from what they had been led, through their training, to expect, and likely to cause confusion over what was going on. Of course, now that this has come to light, one would hope that every 737-MAX pilot would have by now been well-prepared to handle the situation - unless there is some additional issue which has not been identified yet. [1] https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ https://leehamnews.com/2018/11/14/boeings-automatic-trim-for...