"Much like tapping the brake pedal in a car to disengage cruise control, a sharp tug on the controls of older models of Boeing Co’s 737 used to shut off an automatic trim system that keeps the plane flying level, giving the pilot control.
But Boeing disabled the “yoke jerk” function when it brought out the 737 MAX, the latest version of its top-selling jet - and many pilots were unaware of the change, aviation experts told Reuters....
...pilots would have needed to know that MCAS existed, that it had unusual power to force the plane down and that “a hard pull on the yoke” would no longer turn off the automatic trim that uses MCAS, John Hansman, an aeronautics professor at MIT, said in an interview.
“That wasn’t clear to the pilots flying the airplane,” Hansman said. “The training material was not clear on that.”"
https://www.reuters.com/article/us-e...-idUSKCN1R322M