Originally Posted by
Fly Aiprt
What about this "not and anti-stall device" thing, implying the MCAS is supposed to activate before a stall AOA is reached ?
First, a historical note - in the past, airliner stall avoidance training in the sim was directed at the "approach to stall" region. We never actual put the aircraft in the stall because 1) recognition and recovery prior to the stall was the objective, and 2) the sims were never programmed to simulate a full stall in the first place. Thus all the various stall-related warnings and system responses would actually kick in before a full stall was reached. In the aftermath of AF 447 the FAA mandated full-stall training, but that is just now coming on line due to the time required to gather accurate real world data and reprogram the sims.
The whole debate about whether MCAS is an "anti-stall" system is part semantic and part technical. If you browse through FAR Part 25, the particular section dealing with transport category aircraft certification, you will not find any requirement for an "anti-stall" system. On the other hand, you will find requirements for stability and control feel response as the aircraft approaches the stall. The only reason MCAS exists is to meet these requirements. It just so happens that in meeting these requirements, MCAS does assist with control and recovery through the approach to stall region - but technically it is not an "anti-stall" device. That being said, MCAS and a host of other warning indications and system responses in this area of the flight envelope do aid in the stall recovery and could be informally referred to as "anti-stall" devices. While they are technically correct, Boeing and their helpmates have not done themselves any favors by trying to win this technical argument with a largely non-technical audience.