Originally Posted by LarryJ

MCAS is operational only when the autopilot is OFF. You don't takeoff with the autopilot on. The minimum autopilot engagement altitude on takeoff is 800' and it's actually easier to continue to hand fly it through the acceleration and clean up (gear and flaps).

The media keeps reporting that MCAS is a stall prevention system. It is not (though it might also have that affect). MCAS is Maneuvering Characteristics Augmentation System. Due to the aerodynamic characteristics of the engine nacelles, and higher engine residual thrust, the pitch "feel" is lighter at high angles-of-attack on the MAX than it is on the 737 NGs. MCAS adds a nose-down bias, through the application of nose-down stabilizer trim, to produce a heavier "feel" in these situations which more closely matches the pitch "feel", or maneuvering characteristics, of an NG in similar situations.


No. MCAS is only active when the autopilot is disengaged. Since, as you note, the purpose of MCAS is to match the MAX's maneuvering characteristics to those of the NG it is only necessary when the pilots are hand-flying. The autopilot doesn't care if it "feels" the same as other 737 models.

The procedure is not the "MCAS deactivation procedure". It is the "runaway stabilizer" procedure. A variety of systems, and failures, can result in a runaway stabilizer; MCAS is only one of them. Because an unchecked runaway stabilizer can quickly lead to a loss of control, you don't waste time trying to diagnose the reason for the runaway. If you have a runaway, you disable the electric stab trim which stops it. Let the mechanics figure out the cause of the runaway after you land. The runaway stabilizer procedure is the correct actions regardless of the underlying cause of the runaway. Since the autopilot also operates the trim (when it is on), the procedure has you disconnect the autopilot as part of the procedure because a failure in the autopilot could potentially cause a runaway. We're talking here specifically about a runaway caused by MCAS so, in that case, the autopilot must already be off by definition.



More bad reporting. The reporters are trying to report technical information that don't fully understand. The AoA display isn't a "safety feature" and it would not be helpful in dealing with an invalid MCAS activation.

The 737 has two options for conduction low visibility landings--called CAT II and CAT III landings. One option is through the autoland feature which uses the airplanes two autopilots, working together, to land in visabilities as low as 600 feet. The other option is the installation of a heads-up-display (HUD). With the HUD the Captain hand-flies the aircraft to landing using the data display on the HUD as he's looking out the window. This HUD option requires the AoA indicator display option; autoland does not. The airlines that have the AoA display option are the airlines that opted for HUDs for CAT II/III landings while the airlines without it use autoland.