Originally Posted by
bimmerdriver
The fact that the 737 family doesn't have a full FBW flight control system is not the issue. The issue is that the original implementation of MCAS was flawed because it did not take advantage of the redundant AoA sensors, among numerous other things. MCAS is a software function within the redundant flight control computers, which have full authority over the control surfaces.
No, the 737 does not have a full authority flight computer. The A320, 787, 777, etc., does. The 737's pilots can turn off the computer(s), and fly the airplane. A320/787/777/etc. pilots who pull the circuit breakers for the computers are left with a plane with extremely limited function. The 737's systems are best thought of as an overlay onto the existing analogue system of pulleys and cables, while the systems used in true fly-by-wire airplanes fully replace mechanical linkages with computer messages.
MCAS is flawed for multiple reasons, including, but not limited to, the use of inherently non-fault tolerant instrumentation (ie: only 1 AoA sensor, instead of 3), excessive authority required for MCAS to meet certification requirements, and of course, a computer control architecture that was not fault tolerant.
Boeing is not adding a second flight control computer to fix MCAS as your reference claims.
They might have to given that the design basis of the autopilot (its an autopilot -- not a 'flight control computer') did not anticipate that it would be required to operate in such a way that it could not be cut out/disabled and flown manually.
https://fortune.com/2019/08/02/boein...trol-computer/
"
Boeing is working on new software for the 737 Max that will use a second flight control computer to make the system more reliable".
(in contrast, the A320 has, I believe, 5 flight control computers running in parallel, with different CPU architectures and codebases to avoid the possibility of common-mode faults...).
All 737s including the MAXes already have redundant flight control computers. Here is a reference:
Flight Control Computer (FCC). The "ton of additional testing and certification" is exactly what's taking place as we speak.
"All 737s"? Really? I guess if you consider pilots to be 'computers'.....