Originally Posted by
Notanatp
The malfunction also involved flipping a bit to fool the FCC computer into thinking MCAS was active, which disabled the control column cut-out switches from stopping the runaway trim. One or more of the other bit flips must also have prevented the FCC computer from recognizing that MET was being used because use of MET should have reset the MCAS bit to "off," which should have re-enabled the control column cut-out switches (unless the pilots were told to recover without MET). As I wrote before, and tried to explain again (my comment wasn't posted), the likelihood of a five-bit error flipping the five specific bits needed to create the simulator scenario is beyond astronomically small. If the chance of the stars (or in this case neutrons) lining up, over the lifetime of the type, is less than one in a trillion, would you still say that it deserves to be fixed (even though the chances of messing up the fix is probably a lot greater than that)?
The pilots of both accident aircraft detected a malfunction. Detecting the malfunction with enough time to take corrective action wasn't the problem in either flight. The Lion Air crew successfully countered with nose-up trim for about 6 minutes. Nobody knows why they stopped or why they didn't turn electric trim off (or why they apparently advanced the throttles in the final dive). The Ethiopian Airlines crew detected the malfunction but failed to follow the AD (I also believe ET302 was overweight, further complicating the crew's situation).
1. As I wrote before, I am not sure that the five flips coinciding was transmitted correctly through the com. channel main stream media.
2. Even if it was, the astronomically small probability is irrelevant because it uncovered a massive shortcoming of the FCC to handle an exception that may occure through other failure modes as well. They can only be mitigated by choosing an appropriate architecture.
3. Time argument isn't sound. Time was enough to put the aircraft in an energy state and attitude preventing recovery. No, the ethipoian crew did not push the throttles forward during dive.
4. It has been proven by argument and experiment that pilots are unsuitable for pushing the occurance probability for a rare but catastrophic event from the 1e-6 range to the 1e-9 range. This is due to their human nature and not their training state.