[OT] “Raise the nose, HAL.” “I’m sorry, Dave, I’m afraid I can’t do that.”

[Uknown]

On Monday, 22 April 2019 at 01:59:31 UTC, Tony wrote:
> On Sunday, 21 April 2019 at 19:52:58 UTC, Walter Bright wrote:
>
>> [snip]
>> He argues that airplanes are stable without augmentation. This 
>> isn't true for any jetliners, they have an active yaw damper:
>
> I don't know which part you are referring to as suggesting "are 
> stable without augmentation" (a phrase not in the article

What Walter is referring to is the fact that planes in general 
are not machines that fly "in a straight line". They have a 
tendency to bank, roll, or yaw. These are fixed by using 
hardware, or as most modern designs do, in software. When the 
pilot yanks the controller, he dooesn't actually move any control 
surfaces, he just gives an input. This input is then translated 
into movement of control surface by software. If the pilot thinks 
that specific flight control surfaces need to be moved, he can do 
that too, but its not the default.

> , but I see him saying "The airframe, the hardware, should get 
> it right the first time and not need a lot of added bells and 
> whistles to fly predictably".

That is something that hasn't been true for a long time. The 
early planes were all unstable designs. Modern military jets are 
all "relaxed stability". The MD-11 was also similarly unstable. 
It had an "LSAS" to keep it stable. This design isn't something 
that's unheard of or bad. At least we can't say that based on 
publicly available info. The NTSB report will be necessary to say 
anything about this.

> I don't read that as planes should have "zero pilot 
> augmentation". I think his point is you don't design an 
> aircraft, and when you find it has a tendency to stall on 
> takeoff more than a typical or historical aircraft, go ahead 
> and produce it anyway. "Other than a higher than normal 
> tendency to stall on takeoff..." is not what most people want 
> to hear in a design review of a proposed production aircraft.

The point is that such designs really aren't as radical or 
unheard of as the article suggests. These things have been done 
before and will be done again. The MD-11 is an example of another 
commercial aircraft that did it. The MD-11 was also controversial 
in its decision. The real issue here is that the software (MCAS) 
which was supposed to fix the pitch up, was poorly designed.