How many millions of 737 departures have there been since 1967? As far as I can determine, not a single of the
172 hull loss on the 737 has been attributed to a runaway trim prior to the MAX. Two in a very short space of time for the MAX? That is why airworthiness authorities had to act.
One has to be very careful in gleaning statistical information from such a small sample. Randomness comes in lumps. But more importantly, it's vital to remember the two AoA DATA failures were of a totally different nature - a bizarre coincidence in a timescale of five months.
Infrequent said :
The aft-column cutout would have prevented the crashes, period. Overriding it should have been a red flag.
When discussing the changes to the hidden switches I find the memory aid, Column switch - MCAS wins, is useful. Recall that certification is dependant on that nose-down MCAS adjustment.
Given that STS is tried and tested, it doesn't seem unreasonable at face value to use such a system for offsetting the unwanted reduction in stick load. It seems that it was the way the algorithms were so radically altered that caused the frightening speed of AND adjustment. However, I'm not sure if the original rate would have complied. But added to this there was what is effectively a re-datumisation of the stabilizer angle which allowed summing of the AND bursts.
Takwis said:
. . . Moving the stab (repeatedly) a set amount without any check of it's initial position? Moronic. . . .