Is this a pilots' forum or a lawyer's forum? As an engineer and an SLF, I believe civilian airplanes are supposed to be flyable by normal humans, not Chuck Yeager or even Sully. And now we have all this talk about 3 second response times and neutral stability etc. It's a joke.
No employee of the FAA or Boeing would allow a family member to get into an airplane with a 200 hour first officer who is PF after clean up and now and has 3 seconds to respond to HAL's runaway trim while half a dozen of alarms and alerts are going off. Nor even a 55 year old captain with 20K+ hours but 200 on type in a brand new airplane which he got trained on for 1 hour on an iPad, and who may bring lots of experience but zero knowledge of MCAS to the table.
As for "neutral stability", in my book it sounds suspiciously like the edge of a coin.
This is lawyer talk. Engineer talk is "this system is solid, and we have built in such a fat margin of error that not even the most idiotic rest-deprived pilot should ever have an issue with the controls, and also no force is required, every pilot should be able to move the trim wheel with no great effort with one hand."
Pilots should tell their companies, and Boeing, that they want an airframe that is clearly engineered to help them stay in the air. Which in fact is something which the superb engineers at Boeing used to be very happy to deliver.
Or else maybe the pilots who want to discuss semantics in the case of the 737's averred faults should retrain and embrace a more lucrative career in corporate law.
Edmund
Originally Posted by
yoko1
I think a big part of the problem is that words employed in common usage may have more specific meanings in the world of aircraft certification. In a sense, any system that helps keep an aircraft away from the stall environment (for example, autothrottle alpha floor protection, stick shaker, visual and/or audio alerts, etc) could be generically called an "anti-stall" device. However, strictly from a certification standpoint I'm not sure there is even a definition for an "anti-stall" system, much less a requirement. On the other hand, I know there are requirements that commercial aircraft have stall warning systems and demonstrate certain handling characteristics approaching and recovering from a stall.
MCAS exists because of requirement for a linear control feel response through the high AOA environment. To the extent that someone wants to call this an "anti-stall" system and there is no conflicting definition in the FAR's, then I guess there is no harm.
However, in some cases words really do mean something, hence my interest when someone claims the 737 is "unstable." There are very specific definitions of what stability means, and there is no evidence that the 737 demonstrates anything but positive static stability through its flight envelope. I would accept the premise that the this positive stability may trend toward neutral stability approaching high AOA values, but it never goes negative.