But even if there are unknown problems with the MCAS system, American says it is confident pilots can recover because they train for similar problems. MCAS is supposed to push the nose of the plane down if it gets too high by moving the horizontal stabilizer, a panel used all the time to “trim” the airplane. The trim system keeps the plane level, or at a designated rate of climb or descent. The autopilot trims the airplane, or pilots can do it manually.
(Ethiopian Airlines has said its pilots had
new training for 737 MAX planes after the crash in Indonesia.)
If the MCAS system malfunctions, pilots say the prescribed fix is to use manual trim to stabilize the plane, and then disconnect the trim system. There’s a cutoff switch on the center pedestal of the 737, not far from throttles, marked “Stab Trim.” Pilots routinely train to disconnect the automatic trim in the case of runaway trim with autopilot use.