5 upvotes, 2 direct replies (showing 2)
View submission: /u/im-ba explains how badly written software caused the Boeing MAX crashes
But what does that have to do with the air vanes that determine airspeed described in the original post?
Comment by myselfelsewhere at 16/05/2024 at 08:24 UTC*
7 upvotes, 0 direct replies
The sensors being referenced are "angle of attack" or AOA sensors. They don't measure airspeed, they measure the angle of the airplane *relative* to the oncoming air. This is important because if the AOA becomes to great, the wings will stall (no longer produce lift). It's kind of analogous to a car skidding on pavement. but it's an airplane "skidding" through the air.
I originally heard that the controls were programmed in such a way that didn’t require retraining pilots because some of the controls were developed to handle just like the former versions of the 737 but had a different angle for take off.
Yes, that's pretty close, it had to do with angles not for, but after take off. The above commenter is pretty close with their explanation too, but I think it could be said more clearly. Due to the engine changes, the new 737 had slightly different flight characteristics at higher angles of attack. The forward placement of the new engines causes the plane to pitch up more at higher angles of attack - possibly leading to passing the critical angle at which the wings stall.
I'm kind of reiterating most of what you already understand, but adding in some context here...
Boeing had an agreement with the airlines buying the new plane that pilots would not require a new "Type Rating" (basically a license to fly a certain "type" of plane). The altered flight characteristics would have meant a different type rating than previous 737's. So Boeing developed a control scheme that would override the pilots when the plane detects it is at a high angle of attack.
As others in this thread have commented, it wasn't just a software problem. The software more or less did what it was designed to do. The real problem was the way Boeing implemented the system. There weren't the typical safeguards or redundancies in place to ensure the flight computer was receiving data that was *correct*. With the planes that crashed, MCAS was activated because the data it was receiving incorrectly said the plane was at a high angle of attack. So it overrode the control inputs, pushing the nose down to reduce the angle of attack. Pilots were never told about MCAS, particularly about it having the capability of overriding the control inputs. So when MCAS activated, the pilots had no idea why. It just isn't something that would have been the cause of a "trim runaway" situation on previous 737's,
Comment by blablahblah at 16/05/2024 at 02:25 UTC
8 upvotes, 0 direct replies
That's how the computer figures out what the plane is currently doing so it knows how much it still needs to adjust.