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

[sclytrack]

On Tuesday, 23 April 2019 at 08:54:30 UTC, Uknown wrote:
> On Tuesday, 23 April 2019 at 08:09:58 UTC, Russel Winder wrote:
>> On Mon, 2019-04-22 at 13:35 -0700, Walter Bright via 
>> Digitalmars-d wrote: […]
>>> [snip]
>> Surely, Boeing need to remove the MCAS system by reverting the 
>> 737 design to be stable rather than unstable.
>>
>> The 737 MAX is, as far as I know, the first commercial 
>> airplane to be unstable.
>
> The McDonal Douglass MD-11 was also unstable and was used for 
> freight transport.
>
> Wiki link : 
> https://en.wikipedia.org/wiki/McDonnell_Douglas_MD-11
>
> It was designed to have a smaller stabiliser, to reduce drag 
> and thus improve fuel efficiency.
>
>> All military fighter airplanes are unstable but that is a 
>> military fighter. To date, again as far as I know, the 
>> strategy had been that all commercial aircraft were stable. 
>> Boeing broke ranks on this strategy with the 737MAX simply 
>> because they were trying to put an engine that was too big for 
>> the space available and so moved the engine forward and upward 
>> creating an aerodynamically unstable configuration.
>
> Not all are, the ones that are unstable are generally designed 
> in that way so that they are more manoeuvrable. They use use 
> digital fly by wire to make sure that the plane is seemingly 
> stable. This decision by Boeing would have been fine if they 
> had designed their software properly.


You need a stable design for a passenger plane. It happens every 
now
and then that the sensor fails and the plane needs to be able
to fly without them. The Dutch roll effects should go away if you 
just
fly straight, without active dampening, otherwise it is a bad 
design.

Airbus planes have standard 3 angle of attack sensors all 
connected
to the flight computer and you don't have to purchase any 
additional
safety measures like Boeing is doing with their angle of attack
sensors. It is one complete package. So with a single angle of 
attack
sensor failing an airbus plane keeps flying.

In case of an emergency you can switch to other "flight control 
modes".

Lufthansa A321
FL310 Two of the angle of attack sensors frozen in the same 
position. Nose dive.
FL270 Plane recovery.

You need time to recover.

In the Dreamliner Boeing places its angle of attack sensor nicely 
close
to the door so when a jet bridge is attached then they have to be
extremely careful. Just weird design decisions Boeing.