Re: Boeing 737 and 737 MAX software

[tranngocduong@gmail.com]

On Friday, April 19, 2019 at 1:20:21 AM UTC+7, Niklas Holsti wrote:
> ...
> manual correction of the elevation trim 
> becomes impossibly hard when the MCAS-commanded large "dive" trim 
> applies large aerodynamic forces to the trim mechanism. Thus the problem 
> was not only in the software process, but also in the controllability of 
> the aircraft under anomalies
> ...
> Niklas Holsti
> Tidorum Ltd

I know. I've seen a couple of pilots confirming this situtation from simulator experiments.

Every aircraft is designed so that resuming from anormaly, i.e. returning a control surface from heavily deflected position to neutral, is easy thanks to aerodynamic force. 

In particular, manual correction of the horizontal stabilizer becomes impossibly hard because the pilot is deflecting the elevator to the maximum, i.e. he/she is [unknowingly] generating maximal aerodynamic force which goes _against_ the manual correction.

Aerodynamics is friend, not enemy. Pilots are supposed to use it, not to fight it.

In order to return the stabilizer, one have to return the elevator to neutral first.

True, this maneuvre is not so easy as it sounds. It requires training and has became less well-known to pilots in the recent decades. Just like assembly language to programmers. The control stick is like a high-level programming language while the trim wheel is like the assembly language. It is more powerful and it gives more flexibility. But it requires more knowledge and responsibility. Nevertheless, it is there, and perfectly usable.

That said, I don't think manual controlability is a problem of the 737.