Not necessarily, it is entirely conceivable that a design flaw has been lurking there since day one of commercial operation. It just takes a specific sequence to cause an accident
I prefer this theory..We dont know if this is MAX specific.A cursory glance at the NG AMM confirms that this will happen in a NG as well.There may well be differences between MCAS and STS but they both involve trim,they both require inputs that may be corrupted.....you will get unwanted trim if the holes in the swiss cheese line up whether youre sitting in an NG or MAX.
Because of the many variables involved(type of UAS/piloting ability/which FCC is controlling) this specific sequence just never occurred before.We know piloting ability is definitely a variable because this was the 4th flight in sequence.Which FCC is controlling the trim is just a throw of the die...software logic...the pilot wont know this in the heat of the moment(the data is buried in the AMM anyway).The type of UAS is a huge variable(ie multiple ADIRU inputs to FCC,single side vs both side etc).
Is it a design flaw?You cant design perfection...not yet anyway.They need the protection systems but unfortunately those systems may be fed with corrupt data.
Manual flight....you establish this as a recall item during a UAS event.What is manual flight?AP/AT/FD are de-selected.You dont de-select trim....now you may well de-select trim if you recognize STS (or MCAS) responding to bad side data(alertness good airmanship),or you may even disable the AP stab trim as a precaution before STS or MCAS even has a chance to trim(high level of airmanship)....or you may not recognize the insidious trim until its too late due startle factor/panic/inexperience/distraction of tactile aural warnings.So many variables...
Nobody has the data yet on MCAS but Im assuming it works via the AP stab trim motor(even though Boeing in their AD says to disconnect both trim motors) and its controlled by one FCC at a time...
What surprises me here is the total absence of any discussion on the need for pilots to disable loud tactile aural warnings being fed by corrupt data.This to me is the key.The need to establish calm and quiet in a confusing environment can not be over-stated.IMO,the 4 circuit breakers for left/right overspeed and stick shaker should be on the center pedestal right next to the pilots.Those warnings are life savers when correct....but they may be killers when corrupted by bad data.