The pilots on Ethiopian Airlines Flight 302 initially reacted to the emergency by shutting off power to electric motors driven by the automated system, these people said, but then appear to have re-engaged the system to cope with a persistent steep nose-down angle. It wasn’t immediately clear why the pilots turned the automated system back on instead of continuing to follow Boeing’s standard emergency checklist, but government and industry officials said the likely reason would have been because manual controls to raise the nose didn’t achieve the desired results.
After first cranking a manual wheel in the cockpit that controls the same movable surfaces on the plane’s tail that MCAS had affected, the pilots turned electric power back on, one of these people said. They began to use electric switches to try to raise the plane’s nose, according to these people. But the electric power also reactivated MCAS, allowing it to continue its strong downward commands, the people said.
Did they just not crank the wheels enough? The motor operates quickly so it would take a lot of hand cranking to return the trim to neutral. Maybe they hadn't practiced the manual procedure before and were unaware of how many turns were needed?
well is there an indication on how long does it takes to come out of full trim manually? because if it's 30 seconds of cranking the aircraft might very well be descending too fast or too fast in general by the time control is regained.
It’s a lot of cranking to do by hand[1]. You could use the electric trim to reset back to zero and then disable electric trim. (But, that isn’t the procedure.)
It looks like the motor takes 30 seconds to move the jackscrew from one end to the other. Cranking presumably takes much longer. It doesn't seem hard to imagine the ground intervening before you finish cranking back to trimmed level flight.
And that's assuming there's no issue with the aerodynamic load preventing the stabilizer from being retrimmed until you unload the elevator (by pushing the yoke forward), as is being theorized to be the case.
The pilots on Ethiopian Airlines Flight 302 initially reacted to the emergency by shutting off power to electric motors driven by the automated system, these people said, but then appear to have re-engaged the system to cope with a persistent steep nose-down angle. It wasn’t immediately clear why the pilots turned the automated system back on instead of continuing to follow Boeing’s standard emergency checklist, but government and industry officials said the likely reason would have been because manual controls to raise the nose didn’t achieve the desired results.
After first cranking a manual wheel in the cockpit that controls the same movable surfaces on the plane’s tail that MCAS had affected, the pilots turned electric power back on, one of these people said. They began to use electric switches to try to raise the plane’s nose, according to these people. But the electric power also reactivated MCAS, allowing it to continue its strong downward commands, the people said.
Did they just not crank the wheels enough? The motor operates quickly so it would take a lot of hand cranking to return the trim to neutral. Maybe they hadn't practiced the manual procedure before and were unaware of how many turns were needed?