Originally Posted by
Angle of Attack
There has never ever been a Boeing jet that puts Stabilizer trim commands in remotely.
That's what a whole lot of people think, however, it's not true.
According to NTSB submittal to KKNT (page 246 of final PK-LPQ report), Speed Trim System and Maneuvering Characteristics Augmentation System are, despite the nomenclature, not the systems but merely software. They are flight control laws through which Flight Control Computers act on the horizontal stabilizer during manual flight. What NTSB has written about STS being installed on NGs is true but it's not the whole truth: STS has been introduced on 737-300. Baby Boeings have track record of FCC meddling with pitch trim while autopilot is off since 1984. but as STS has far lesser authority than MCAS (especially as installed, compared to as certified) it is at worst just a mild nuisance.